(livro) structural steel design and construction, Manuais, Projetos, Pesquisas de Engenharia Civil

Baixe (livro) structural steel design and construction e outras Manuais, Projetos, Pesquisas em PDF para Engenharia Civil, somente na Docsity! Building and Construction Authority ad: E Ed Sd vel vu e e! E ESÁ E Go v09 va e ve) ga nÊ is s E g ao 8: ó | g | E E E A RESOURCE BOOK FOR STRUCTURAL STEEL DESIGN & CONSTRUCTION (SSSS & BCA JOINT-PUBLICATION) I Building and Construction .Authority Singapore Structural Steel Society IV ACKNOWLEDGEMENT T This resource book was made possible by a team of SSSS members and BCA officers with inputs from various government agencies, developers, architects, engineers, contractors, steel fabricators and suppliers. Author: Dr. J Y Richard Liew Publication Committee From SSSS From BCA Dr. J Y Richard Liew Mr Leonard Soh Mr John Moody Mr Ng Cheng Kiat Mr Tan Tian Chong Mr Ang Lian Aik Mr Steven Cheong Ms Denise K wok Ms Kong Chew K wek Department of Civil Engineering National University of Singapore National University of Singapore Continental Steel Pte Ltd Yongnam Engineering & Construction Pte Ltd TY Lin SEA Pte Ltd Technology Development Division Technology Development Division Technology Development Division Technology Development Division Technology Development Division ACKNOWLEDGEMENT (CONT'D) SSSS and BCA would like to thank the following organisations for consent to use the information and photographs from their projects. Capital Tower Private Limited for Capital Tower City Developments Limited for Republic Plaza Civil Aviation Authority of Singapore for 2 Finger Buildings at Terminal 1 Singapore Changi Airport Cuppage Centre Private Limited for The Cuppage Centre HKL (Esplanade) Private Limited for One Raffles Link Land Transport Authority of Singapore for Expo MRT Station OUB Centre Limited for OUB Centre PSA Corporation Limited for Keppel District Park and Singapore Expo Singapore Post Private Limited for Singapore Post Centre Singapore Sports Council for Bishan Sports Stadium and Singapore Indoor Stadium Singapore Turf Club for Kranji Racecourse Suntec Development Private Limited for Singapore International Convention and Exhibition Centre United Engineers Limited for UE Square Continental Steel Pte Ltd, BHP Steel Building Products Singapore Pte Ltd, Yong Nam Engineering & Construction Pte Ltd & WY Steel Construction Pte Ltd for Section V - Cost of Steel Structures & Materials v VI '""'"',.._.., SINGAPORE STRUCTURAL STEEL SociETY '""'"',.._.., The Singapore Structural Steel Society, a non-profit organization, was inaugurated on 23 October 1984. Often referred to as the SSSS, the Society aims to develop a resource of the best and latest information on the science, engineering and technology of structural steel, and strives to promote the proper and greater alternative use of structural steel for the benefit of the community and the region. This is made possible through the regular organization of seminars, evening lectures, short courses and conferences on various aspects of structural steelworks as well as publication of newsletters and technical journals. Council Members (2000/200 1) President Imm Past President 1st Vice President 2nd Vice President Hon Secretary Hon Treasurer Council Members Name Lim Keng Kuok Chiew Sing Ping J Y Richard Liew Leonard Soh Bernard Chung MS Islam Ang Kok Keng Lauw Su Wee John Moody Ng Cheng Kiat Anthony Tan Tan Tian Chong V Thevendran Company PWD Consultants Pte Ltd Nanyang Technological University National University of Singapore Continental Steel Pte Ltd Corus South East Asia Pte Ltd Singapore Polytechnic National University of Singapore LSW Consultants Pte Ltd Yongnam Engineering & Construction Pte Ltd TY Lin SEA Pte Ltd BHP Steel Building Products Singapore Pte Ltd Building and Construction Authority National University of Singapore '""'"',.._.., THE BuiLDING AND CoNSTRUCTION AuTHORITY '""'"'"'"'"' The building and Construction Authority of Singapore (BCA) is a statutory board under the Ministry of National Development of Singapore. BCA's mission is to develop a technologically advanced construction industry, which serves Singapore's economic needs, and to ensure safe buildings and infrastructure. This jointed publication with SSSS is part of the continuing efforts by BCA to promote higher quality and productivity through the adoption of buildable designs in the construction industry. The objective is in line with BCA's aim to help transform the construction industry into a technologically advanced and high valued-added industry. SECTION 1 DESIGN CONCEPTS AND STRUCTURAL SCHEMES FOR MULTI-STOREY STEEL BUILDINGS 2 1.1 MODERN TECHNIQUES IN STEEL FRAME CONSTRUCTION 1.1.1 Buildability of Steelwork Construction One of the main considerations in planning a building project is to have the building ready and occupied as early as possible. In order to reduce the time over which the investment is tied up in construction and maximize the return of investment through the use of the building, the design needs to consider the buildability aspects of the construction. Speed in construction is achieved through a number of factors, some of which are listed below: Simple building design to avoid complicated site works Design for minimum delay in construction Maximize use of pre-fabricated and precast elements to avoid delays on site Reduce the number of operations on the critical path Complete all the designs before starting work on site Complicated geometry and building layout design should be avoided where possible. This is especially critical in crowded city sites where access and storage of materials may be a problem. Repetition of work means that the work can be done in a much faster process. The more repetition in elements, the quicker the site team goes through the process of familiarization. In steel framed building the positioning of services may need careful consideration at the design stage to allocate service zones. Hence, conflict of interests between various professions can be avoided. Steel offers the best framing material for pre-fabrication. With the use of metal decks, the concept of Fast Track Construction is introduced. The metal decking can be placed easily and used as the slab reinforcement. Through- deck stud welding for composite action reduces beams weights and/or depths. It also helps ensure that the floor slab can be used as a diaphragm to transfer lateral loads to the bracing frames or stiff cores. Lightweight fire protection can be applied at a later stage, taking it off the critical path. 1.1.2 Prefabrication and Ease of Construction Steel members and plates can be shop-fabricated using computer-controlled machinery, which have less chance of mistakes. On site the assembly is mainly carried out by a bolting procedure. Lateral load resisting system should be located at the lifts, stair towers etc to provide stability throughout, rather than a rigid unbraced frame where temporary bracing may be required during erection. Structural members delivered to site should be lifted directly and fixed into position, avoiding storage on site. Steel stairs, erected along with the frame, give immediate access for quicker and safer erection. Metal decking may be lifted in bundles and no further craning is required as it is laid by hand and fixed by welded studs. This gives both a working and safety platform against accidents. Secondary beams should be placed close enough to suit the deck, so that temporary propping can be avoided, and the deck could be concreted immediately. 1.1.3 Steel-concrete Composite Design Considerable benefit is gained by composition of the slab with the steel beam with possible weight savings of up to 30%. An effective width of a slab is assumed to carry the compressive stresses leaving virtually the whole of the steel beam in tension creating a T - beam effect. Interaction between the slab and the beam is generated by 'through deck" stud welding on to the beam flange . 1.1.4 Deflection and Cambering Where the floors are unpropped, the deflection due to wet construction requires consideration to avoid the problem of ponding. Dead load deflections exceeding 15-20mm can be easily offset by cambering which is best achieved by cold rolling the beam. This is a specialized operation but not only is the camber permanent because of stress re-distribution due to controlled yielding. These will depend upon a number of factors and the advice of the specialist should be sought. Because cambering can add 10-20% to the basic steel cost, this should be compared with the cost of a deeper and stiffer beam section provided that the increase in building height does not compromise additional cladding costs. 1.1.5 Fire Resistance In the event of fire the metal deck unit would cease to function effectively due to loss of strength. However, additional strength can be provided by the added wire mesh for up to one hour fire rating. For higher period of fire resistance or for exceptionally high imposed loads, heavier reinforcement in the form of bars placed within the deck troughs can be used. Up to 4 hours fire rating can be obtained using this method based upon fire engineering calculations with the deck units serving only as a permanent formwork. For beams and columns, fire resistance may be provided by lightweight systems, which are quick to apply and economic. Normally cement based sprays are applied to beams, and boards around columns. For tall buildings, steel columns may be encased or circular steel columns infilled with high-strength concrete to enhance resistance against compression and fire. 1.2 CLASSIFICATION OF MULTI- STOREY FRAMES Itis useful to define various frame systems to simplify the modelling of multistorey frames. For more complicated three-dimensional structures involving the interaction of different structural systems, simple models are useful for preliminary design and for checking computer results. These models should capture the behaviour of individual subframes and their effects on the overall structures. This section describes what a framed system represents, defines when a framed system can be considered to be braced by another system, what is meant by a bracing system, and the difference between sway and non-sway frames. Various structural schemes for multistorey building construction are also given. 1.2.1 Moment Frames A moment frame derives its lateral stiffness mainly from the bending rigidity of frame members inter-connected by rigid joints. The joints shall be designed in such a manner that they have enough strength and stiffness and negligible deformation. The deformation must be small enough to have any significant influence on the distribution of internal forces and moments in the structure or on the overall frame deformation. An unbraced rigid frame should be capable of resisting lateral loads without relying on additional bracing system for stability. The frame, by itself, has to resist the design forces, including gravity as well as lateral forces. At the same time, it should have adequate lateral stiffness against side sway when it is subjected to horizontal wind or earthquake loads. Even though the detailing of the rigid connections results in a less economic structure, rigid unbraced frame systems perform better in load reversal situation or in earthquakes. From the architectural and functional points of view, it can be advantageous not to have any triangulated bracing systems or solid wall systems in the building. 1.2.2 Simple Frames A simple frame referred to a structural system in which the beams and columns are pinned connected and the system is not capable of resisting any lateral loads. The stability of the entire structure must be provided by attaching the simple frame to some forms of bracing systems. The lateral loads are resisted by the bracing systems while the gravity loads are resisted by both the simple frame and the bracing system. In most cases, the lateral load response of the bracing system is sufficiently small such that second-order effects may be neglected for the design of the frames. Thus the simple frames that are attached to the bracing system may be classified as non-sway frames. Figure 1.1 shows the principal components - simply frame and bracing system - Of such a structure. There are several reasons of adopting pinned connections in the design of steel multistorey frames: 1. pin-jointed frames are easier to fabricate and erect. For steel structures, it is more convenient to join the webs of the members without connecting the flanges. 2. bolted connections are preferred than welded connections, which normally require weld inspection, weather protection and surface preparation. 3. tis easier to design and analyse a building structure that can be separated into system resisting vertical loads and system resisting horizontal loads. For example, if all the girders are simply supported between the columns, sizing of the girders and columns is a straightforward task. 4. itis more cost effective to reduce the horizontal drift by means of bracing systems added to the simple framing than to use unbraced frame systems with rigid connections. 1.2.3 Bracing Frames Bracing systems provide lateral stability to the overall framework. It may be in the forms of triangulated frames, shear wall/cores, or rigid-jointed frames. It is common to find bracing systems represented as shown in Figure].2. JELCISLIDIÇICTIITTO BRACNG FRANE- CESCTLTIICILIIDIÇTI SMPLE CONNECTIONS Figure 1.1 Simple Braced Frame 38NL G3ZNVNODVII HOIHIL 3ent aaNvHs GaNaNt 3901 CIWVUS HOIUILXI AVES szen1 q: CNY TINNVHO ONI SISSAUL HVIHS HOIUILNI HLIM 3ONL O3WVHS TINNVHO QNI . 83SSQUI HIODIHLNO ONY ONVS UVIHS HUM INvUI SSnUL UV3HS HLIM 3WVHS BWvHa alo 3WvHs arotHnas o o o o o o o o o o o E o o < o q = no 100 9 S3IHOLS JO HISNNN Figure 1.5 Categorization of Tall Building Systems. 1.3 FLOOR SYSTEMS 1.3.1 Design Consideration Floor systems in tall buildings generally do not differ substantially from those in low-rise buildings. However, the following aspects need to be considered in design: 1. Weight to be minimised. 2. Self-supporting during construction. 3. Mechanical services to be integrated in the floor zone. 4. Adequate fire resistance. 5. Buildability. 6. Long spanning capability. 7. Adequate floor diaphragm Modern office buildings require large floor span in order to create greater space flexibility for the accommodation of greater variety of tenant floor plans. For building design, it is necessary to reduce the weight of the floors so as to reduce the size of columns and foundations and thus permit the use of larger space. Floors are required to resist vertical loads and they are usually supported by secondary beams. The spacing of the supporting beams must be compatible with the resistance of the floor slabs. The floor sys tems can be made buildable usi ng prefabricated or precast elements of steel and reinforced concrete in various combinations. Floor slabs can be precast concrete slab or composite slabs with metal decking. Typical precast slabs are 4 m to 7 m, thus avoiding the need of secondary beams. For composite slabs, metal deck spans ranging from 2m to 7 m may be used depending on the depth and shape of the deck profile. However, the permissible spans for steel decking are influenced by the method of construction, in particular it depends on whether temporary propping is provided. Propping is best avoided as the speed of construction is otherwise diminished for the construction of tall buildings. Floor beans systems must have adequate stiffness to avoid large deflections which could lead to damage of plaster and slab finishers. Where the deflection limit is too severe, pre-cambering with an appropriate initial deformation equal and opposite to that due to the permanent loads can be employed to offset part of the deflection. Sometimes openings in the webs of beams are required to permit passage of horizontal services, such as pipes (for water and gas), cables (for electricity, tele- and electronic- communication), and ducts (air-conditioning), etc. Various long span flooring systems in Sections 3.4 offer solutions to integrate building service into the structural depth leading to potential saving in weight and cladding cost. 1.3.2 Composite Floor Systems Composite floor systems typically involve structural steel beams, joists, girders, or trusses linked via shear connectors with a concrete floor slab to form an effective T-beam flexural member resisting primarily gravity loads. The versatility of the system results from the inherent strength 7 of the concrete floor component in compression and the tensile strength of the steel member. The main advantages of combining the use of steel and concrete materials for building construction are: Steel and concrete may be arranged to produce ideal combination of strength, with concrete efficient in compression and steel in tension. Composite flooring is lighter in weight than pure concrete slab. The construction time is reduced since casting of additional floors may proceed without having to wait for the previously cast floors to gain strength. The steel decking system provides positive-moment reinforcement for the composite floor and requires only small amount of reinforcement to control cracking and for fire resistance. The construction of composite floor does not require highly skilled labour. The steel decking acts as a permanent form work. Composite beams and slabs can accommodate raceways for electrification, communication, and air distribution system. The slab serves as a ceiling surface to provide easy attachment of a suspended ceiling. The composite floor system produces a rigid horizontal diaphragm, providing stability to the overall building system while distributing wind and seismic shears to the lateral load resisting systems. Concrete provides thermal protection to steel at elevated temperature. Composite slabs of two hours fire rating can be easily achieved for most building requirements. The floor slab may be constructed by the following methods: a flat-soffit reinforced concrete slab (Fig. 1.6a) , precast concrete planks with cast in-situ concrete topping (Fig. 1.6b), precast concrete slab with in-situ grouting at the joints (Fig. 1.6c), and a metal steel deck tops with concrete, either composite or non-composite (Fig. 1.6d). The composite action of the metal deck results from side embossments incorporated into the steel sheet profile. 1.3.3 Composite Beams and Girders Steel and concrete composite beams may be formed by shear connectors connecting the concrete floor to the top flange of the steel member. Concrete encasement will provide fire resistance to the steel member. Alternatively, direct sprayed-on cementitious and board type fireproofing materials may be used economically to replace the concrete insulation on the steel members. The most common arrangement found in composite floor systems is a rolled or built-up steel beam connected to a formed steel deck and concrete slab (Fig. 1.6d). The metal deck typically spans unsupported between steel members while also providing a working platform for concreting work. 8 in situ concrete reinforcement steel- section (a) (b) (c) (d) Figure 1.6 Composite beams with (a) flat-soffit reinforced concrete slab (b) precast concrete planks and cast-in-situ concrete topping (c) precasted concrete slab and in-situ concrete at the joints (d) metal steel deck supporting concrete slab in situ concrete reinforcement in s~u concrete reinforcement simplicity of connections and ease of fabrication make this long-span beam option particularly attractive. 1.3.4.5 Composite Trusses Composite truss systems have been used in the OUB Centre and Suntec City projects (see Sections 3 and 4). The openings created in the truss braces can be used to accommodate large services. Although the cost of fabrication is higher in relation to the material cost, truss construction can be cost-effective for very long span when compared to other structural schemes. One disadvantage of the truss configuration is that fire protection is labour intensive and sprayed-protection systems cause a substantial mess to the services that pass through the web opening (see Fig. 1.13). Figure 1.13 Composite truss Several forms of truss arrangement are possible. The three most common web framing configurations in floor truss and joist designs are: (a) Warren Truss, (b) Modified Warren Truss and (c) Pratt Truss as shown in Fig. 1.14. The efficiency of various web members in resisting vertical shear forces may be affected by the choice of a web-framing configuration. For example, the selection of Pratt web over Warren web may effectively shorten compression diagonals resulting in more efficient use of these members. The resistance of a composite truss is governed by (l) yielding of the bottom chord (2) crushing of the concrete slab, (3) failure of the shear connectors, (4) buckling of top chord during construction, (5) buckling of web members, and (6) instability occurring during and after construction. To avoid brittle failures, ductile yielding of (a) (b) (c) Figure 1.14 Truss configuration: (a) Warren truss, (b) Modified Warren truss, and (c) Pratt truss 11 the bottom chord is the preferred failure mechanism. Thus the bottom chord should be designed to yield prior to crushing of concrete slab. The shear connectors should have sufficient capacity to transfer the horizontal shear between the top chord and the slab. During construction, adequate plan bracing should be provided to prevent top chord buckling. When consider composite action, the top steel chord is assumed not to participate in the moment resistance of the truss, since it is located very near to the neutral axis of the composite truss and, thus, contributed very little to the flexural capacity. 1.3.4.6 Stub Girder System The stub girder system involves the use of short beam stubs which are welded to the top flange of a continuous, heavier bottom girder member, and connected to the concrete slab through the use of shear studs. Continuous transverse secondary beams and ducts can pass through the openings formed by the beam stub. The natural openings in the stub girder system allow the integration of structural and service zones in two directions (Fig. 1.15), permitting storey-height reduction when compared with some other structural framing systems. Shear connector Shear connector Figure 1.15 Stub girder system Ideally, stub-girders span about 12 to 15 meters in contrast to the conventional floor beams which span about 6 to 9 meters. The system is therefore very versatile, particularly with respect to secondary framing spans with beam depths being adjusted to the required structural configuration and mechanical requirements. Overall girder depths vary only slightly, by varying the beam and stub depths. The major disadvantage of the stub girder system is that it requires temporary props at the construction stage, and these props have to be remained until the concrete has gained adequate strength for composite action. However, it is possible to introduce additional steel top chord, such as a T-section, which acts in compression to develop the required bending strength during construction. For span length greater than 15 meters, stub-girders become impractical, because the slab design becoming critical. In the stub girder system, the floor beams are continuous over the main girders and splice at the locations near the points of inflection. The sagging moment regions of the floor beams are usually designed compositely with the deck-slab system, to produce savings in structural steel as well as to provide stiffness. The floor beams are 19olted to the top flange of the steel bottom chord of the stub-girder, 12 and two shear studs are usually specified on each floor beam, over the beam-girder connection, for anchorage to the deck-slab system. The stub-girder may be analysed as a vierendeel girder, with the deck-slab acting as a compression top-chord, the full-length steel girder as a tensile bottom-chord, and the steel stubs as vertical web members or shear panels. 1.3.4.7 Prestressed Composite Beams Prestressing of the steel girders is carried out such that the concrete slab remains uncracked under the working loads and the steel is utilised fully in terms of stress in the tension zone of the girder. Prestressing of steel beam can be carried out using a precambering technique as depicted in Fig. 1.16. First a steel girder member is prebent (Fig. 1.16a), and is then subjected to preloading in the direction against the bending curvature until the required steel strength is reached (Fig. 1.16b). Secondly, the lower flange of the steel member, which is under tension, is encased in a reinforced concrete chord (Fig. 1.16c ). The composite action between the steel beam and the concrete slab is developed by providing adequate shear connectors at the interface. When the concrete gains adequate strength, the steel girder is prestressed by stress-relieving the precompressed tension chord (Fig. 1.16d). Further composite action can be achieved by supplementing the girder with in-situ or prefabricated reinforcement concrete slabs, and this will produce a double composite girder (Fig. 1.16e). The main advantage of this system is that the steel girders are encased in concrete on all sides, no corrosion and fire protection are required on the sections. The entire process of precambering and prestressing can be performed and automated in a factory. During construction, the lower concrete chord cast in the works can act as formwork. If a) b l r;;;.. __ L --* --ci~ c l ~=L======* ====i:::liS d)~ l T e) !;======~ I I Figure 1.16 Process of prestressing using precambering technique the distance between two girders is large, precast planks can be supported by the lower concrete chord which is used as permanent formwork. Prestressing can also be achieved by using tendons which can be attached to the bottom chord of a steel composite truss or the lower flange of a composite girder to enhance the load-carrying capacity and stiffness of long-span structures (Fig. 1.17). This technique has been found to be popular for bridge construction in Europe and USA, although less common for building construction. Figure 1.17 Prestressing of composite steel girders with tendons 1.3.5 Comparison of Floor Spanning Systems The conventional composite beams are the most common forms of floor construction for a large number of building projects. Typically they are highly efficient and economic with bay sizes in the range of 6 to 12 m. There is, however, much demand for larger column free areas where, with a traditional composite approach, the beams tend to become excessively deep, thus unnecessary increases the overall building height, with the consequent increases in cladding costs, etc. Spans exceeding 12 m are generally achieved by choosing an appropriate structural form which integrates the services within the floor structure, thereby reducing the overall floor zone depths. Although a long span solution may entail a small increase in structural costs, the advantages of greater flexibility and adaptability in service and the creation of column-free space often represent the most economic option over the design life of the building. Figure 1.18 compares the various structural options of typical range of span lengths used in practice. Span Length (m) 4 6 RC Beam & Slab ---- Steel Beam Steel Plate Girder Composite Steel Beam Composite Plate Girder Composite Beam with Web Opening Parallel Beam System Tapered Composite Beam Stub Girder System Haunched Composite Beam Composite Truss Prestressed Composite Beam 10 12 14 16 18 20 25 Figure 1.18 Comparison of flooring systems 1.3.6 Floor Diaphragms Typically, beams and columns rigidly connected for moment resistance are placed in orthogonal directions to resist lateral loads. Each plane frame would assume to resist a portion of the overall wind shear which is determined from the individual frame stiffness in proportion to the overall stiffness of all frames in that direction. This is based on the assumption that the lateral loads are distributed to the various frames by the floor diaphragm. In order to develop proper diaphragm action, the floor slab must be attached to all columns and beams that participate in lateral-force resistance. For building relying on bracing systems to resist all lateral load, the stability of a building depends on rigid floor diaphragm to transfer wind shears from their point of application to the bracing systems such as lattice frames, shear walls, or core walls. The use of composite floor diaphragms in place of in-plane steel bracing has become an accepted practice. The connection between slab and beams are often through shear studs which are welded directly through metal deck to the beam flange. The connection between seams of adjacent deck panels is crucial and often through inter-locking of panels overlapping each other. The diaphragm stresses are generally low and can be resisted by floor slabs which have adequate thickness for most buildings. Plan bracing is necessary when diaphragm action is not adequate. Figure 1.19a shows a triangulated plan bracing system which resists lateral load on one side and spans between the vertical walls. Fig. 1.19b illustrated the case where the floor slab has adequate thickness and it can act as diaphragm resisting lateral loads and transmitting the forces to the vertical walls. However, if there is an abrupt change in lateral stiffness or where the shear must be transferred from one frame to the other due to the termination of lateral bracing system at certain height, large (a) 13 diaphragm stresses may be encountered and they must be accounted for through proper detailing of slab reinforcement. Also, diaphragm stresses may be high where there are large openings in the floor, in particular at the corners of the openings. The rigid diaphragm assumption is generally valid for most high-rise buildings (Fig. 1.20a); however, as the plan aspect ratio (b/a) of the diaphragm linking two lateral systems exceeds 3 in 1 (see the illustration in Fig. 1.20b ), the diaphragm may become semi-rigid or flexible. For such cases, the wind shears must be allocated to the parallel shear frames according to the attributed area rather than relative stiffness of the frames. From the analysis point of view, a diaphragm is analogous to a deep beam with the slab forming the web and the peripheral members serving as the flanges as shown in Fig. 1.20b. It is stressed principally in shear, but tension and compression forces must be accounted for In design. A rigid diaphragm is useful to transmit torsional forces to the lateral-load resistance systems to maintain lateral stability. Figure 1.2la shows a building frame consisting of three shear walls resisting lateral forces acting in the direction of Wall A. The lateral load is assumed to act as a concentrated load with a magnitude F on each storey. Figure 1.2lb and 1.2lc show the building plan having dimensions of L1 and L2• The lateral load resisting system are represented in plan by the solid lines which represent Wall A, Wall B and Wall C. Since there is only one lateral resistance system (Wall A) in the direction of the applied load, the loading condition creates a torsion (Fe), and the diaphragm tends to rotate as shown by the dashed lines in Fig. 1.21 b. The lateral load resistance systems in Wall B and Wall C will provide the resistance forces to stabilise the torsional force by generating a couple of shear resistance. (b) Figure 1.19 (a) Triangulated plan bracing system (b) concrete floor diaphragm 16 1.4 DESIGN CONCEPTS AND STRUCTURAL SCHEMES 1.4.1 Introduction Multistorey steel frames consist of column and beam interconnected to form a three-dimensional structure. A building frame can be stabilized either by some forms of bracing systems (braced frames) or by itself (unbraced frames). All building frames must be designed to resist lateral load to ensure overall stability. A common approach is to provide a gravity framing system with one or more lateral bracing systems attached to it. This type of framing system, which is generally referred to as simple braced frames, is found to be cost effective for multistorey buildings of moderate height (up to 20 storeys). For gravity frames, the beams and columns are pinned connected and the frames are not capable of resisting any lateral loads. The stability of the entire structure is provided by attaching the gravity frames to some forms of bracing systems. The lateral loads are resisted mainly by the bracing systems while the gravity loads are resisted by both the gravity frame and the bracing system. For buildings of moderate height, the bracing system's response to lateral forces is sufficiently stiff such that second-order effects may be neglected for the design of such frames . In moment resisting frames, the beams and columns are rigidly connected to provide moment resistance at joints, which may be used to resist lateral forces in the absence of any bracing systems. However, moment joints are rather costly to fabricate. In addition, it takes longer time to erect a moment frame than a gravity frame. A cost effective framing system for multistorey buildings can be achieved by minimizing the number of moment joints, replacing field welding by field bolting, and combining various framing schemes with appropriate bracing systems to minimize frame drift. A multistorey structure is most economical and efficient is when it can transmit the applied loads to the foundation by the shortest and most direct routes . For ease of construction, the structural schemes should be simple enough, which implies repetition of member and joints, adoption of standard structural details, straightforward temporary works, and minimal requirements for inter-related erection procedure to achieve the intended behavior of the completed structure. Sizing of structural members should be based on the longest spans and largest attributed roof and/or floor areas. The same sections should be used for similar but less onerous cases. Scheme drawings for multistorey building design should include the followings: 1. general arrangement of the structure including, column and beam layout, bracing frames, and floor systems, 2. critical and typical member sizes, 3. typical cladding and bracing details, 4. typical and unusual connection details, and 5. proposals for fire and corrosion protection. This section offers advice on the general principles to be applied when preparing a structural scheme for multistorey steel and composite frames. The aim is to establish several structural schemes that are practicable, sensibly economic, and functional to the changes that are likely to be encountered as the overall design develops. The section begins by examining the design procedure and construction considerations that are specific to steel gravity frames, braced frames and moment resisting frames, and the design approaches to be adopted for sizing multi-storey building frames. The potential use of steel-concrete composite material for high-rise construction is then presented. Finally, the design issues related to braced and unbraced composite frames are discussed. 1.4.2 GRAVITY FRAMES Gravity frames refer to structures that are designed to resist only gravity loads. The bases for designing gravity frames are as follows: ' 1) The beam and girder connections transfer only vertical shear reactions without developing bending moment that will adversely affect the members and the structure as a whole. 2) The beams may be designed as simply supported member. 3) Columns must be fully continuous. The columns are designed to carry axial loads only. Some codes of practice (e.g., BS5950, 1990) require the column to carry nominal moments due to the reaction force at the beam end, applied at an appropriate eccentricity. 4) Lateral forces are resisted entirely by bracing frames or by shear walls, lift or staircase closures, through floor diaphragm action. 1.4.2.1 General Guides The following points should be observed in the design of gravity frames: 1) provide lateral stability to gravity framing by arranging suitable braced bays or core walls deployed symmetrically in orthogonal directions, or wherever possible, to resist lateral forces. 2) adopt a simple arrangement of slabs, beams and columns so that loads can be transmitted to the foundations by the shortest and most direct load paths. 3) tie all the columns effectively in orthogonal directions at every storey. This may be achieved by the provision of beams or ties that are placed as close as practicable to the columns. 4) select a flooring scheme that provides adequate lateral restraint to the beams and adequate diaphragm action to transfer the lateral load to the bracing system. 5) for tall building construction, choose a profiled- steel-decking composite floor construction if uninterrupted floor space is required and/or height is at a premium. As a guide, limit the span of the floor slab to 2.5-3.6m; the span of the se~ondary beams to 6-12m; and the span of the primary beams to 5-7m. Otherwise, choose a precast or an in-situ reinforced concrete floor, limiting their span to 5-6m, and the span of the beams to 6-8m approximately 1.4.2.2 Structural Layout In building construction, greater economy can be achieved through a repetition of similarly fabricated components. A regular column grid is Jess expensive than a non-regular grid for a given floor area. In addition, greater economies can be achieved when the column grids in plan are rectangular in which the secondary beams should span in the longer direction and the primary beams in the shorter as shown in Figs. 1.22a&b. This arrangement reduces the number of beam-to-beam connections and the number of individual members per unit area of supported floor. Primary beams Preferred (a) !¥1- Secoiidary beams Non-Preferred -]Dill -!WIJ L, - L, IFor efficient layout LJL, ~ 1.3 (b) Figure 1.22 (a) Rectanglular grid layout (b) Preferred and non-preferred grid grid layout In gravity frames, the beams are assumed to be simply supported between columns. The effective beam span to depth ratio (LID) is about 12 to 15 for steel beams and 18 to 22 for simply supported composite beams. The design of beam is often dependent on the applied load, the type of beam system employed and the restrictions on structural floor depth. The floor-to-floor height in a multistorey building is influenced by the restrictions on overall building height and the requirements for services above and/or below the floor slab. Naturally, flooring systems involving the use of structural steel members that act compositely with the concrete slab achieve the longest spans. 1.4.2.3 Analysis and Design The analysis and design of a simple braced frame must recognize the following points: 1) The members intersecting at a joint are pin connected. 2) The columns are not subject to any direct moment transferred through the connection, but nominal moments due to eccentricity of the beam reaction 17 forces should be considered. The design axial force in the column is predominately governed by floor loading and the tributary areas. 3) The structure is statically determinate. The internal forces and moments are therefore determined from a consideration of statics. 4) Gravity frames must be attached to a bracing system so as to provide lateral stability to the part of the structure resisting gravity load. The frame can be designed as a non-sway frame and the second-order moments associated with frame drift can be ignored. 5) The leaning column effects due to column side-sway must be considered in the design of the frames that are participated in side sway resistance. Since the beams are designed as simply supported between their supports, the bending moments and shear forces are independent of beam size. Therefore, initial sizing of beams is a straight-forward task. Most conventional types of floor slab construction will provide adequate lateral restraint to the compression flange of the beam. Consequently, the beams may be designed as laterally restrained beams without the moment resistance being reduced by lateral-torsional buckling. Under the service loading, the total central deflection of the beam or the deflection of the beam due to unfactored live load (with proper precambering for dead load) should satisfy the deflection limits as given in Table 1.2. In some occasions, it may be necessary to check the dynamic sensitivity of the beams. When assessing the deflection and dynamic sensitivity of secondary beams, the deflection of the supporting beams must also be included. Whether it is the strength, deflection or dynamic sensitivity which controls the design will depend on the span-to-depth ratio of the beam. Figure 1.18 gives typical span ranges for beams in office buildings for which the design would be optimized for strength and serviceability. For beams with their span lengths exceeding those shown in Fig. 1.18, serviceability limits due to deflection and vibration will most likely be the governing criteria for design. The required axial forces in the columns can be derived from the cumulative reaction forces from those beams that frame into the columns. Live load reduction should be considered in the design of columns in a multistorey frame. If the frame is braced against side sway, the column node points are prevent from lateral translation. A conservative estimate of column effective length, KL, for buckling considerations is l.OL, where L is the storey height. However, in cases where the columns above and below the storey under consideration are underutilized in terms of load resistance, the restraining effects offered by these members may result in an effective length of less than 1.0L for the column under consideration. Such a situation arises where the column is continuous through the restrain~ points and the columns above and/or below the restraint points are of different length. 18 Table 1.2 Recommended deflection limits for steel building frames. Beam deflections from unfactored imposed loads Beams carrying plaster or brittle finish span/360 Other beams span/240 Edge beams supporting cladding span/500 Beam deflection due to unfactored dead and imposed loads Internal beams with ceilings span/200 Edge beams supporting cladding span/350 Columns deflections from unfactored imposed and wind loads Column in single storey frames Column in multistorey frames Column supporting cladding which is sensitive to large movement Frame drift under 50 years wind load Frame drift 1.4.2.4 Simple Connections Simple connections are designed to resist vertical shear at the beam end. Depending on the connection details adopted, it may also be necessary to consider an additional bending moment resulting from the eccentricity of the bolt line from the supporting face. Often the fabricator is told to design connections based on the beam end reaction for one-half uniformed distributed load (UDL). Unless the concentrated load is located very near to the beam end, UDL reactions are generally conservative. Because of the large reaction, the connection becomes very strong which may require large number of bolts. Thus it would be a good practice to design the connections for the actual forces used in the design of the beam. The engineer should give the design shear force for every beam to the steel fabricator so that a more realistic connection can be designed, instead of requiring all connections to develop the shear capacity of the beam. Figure 1.23 shows the typical connections that can be designed as simple connections. When the beam reaction is known, capacity tables developed for simple standard connections can be used for detailing such connections. 1.4.3 BRACING SYSTEMS Bracing frames provide the lateral stability to the entire structure. It has to design to resist all possible kinds of lateral loading due to external forces, e.g. wind forces, earthquake forces and "leaning forces" from the gravity frames . The wind or the equivalent earthquake forces on the structure, whichever are greater, should be assessed and divided into the number of bracing bays resisting the lateral forces in each direction. 1.4.3.1 Structural Forms Steel braced systems are often in a form of vertical truss height/300 height of storey/300 height of storey/500 Frame height/450 ~ Frame height/600 which behaves like cantilever elements under lateral loads developing tension and compression in the column chords. Shear forces are resisted by the bracing members . The truss diagonalization may take various forms, as shown in Figure 1.24. The design of such structures must take into account the manner in which the frames are erected, the distribution of lateral forces and their side sway resistance. Web cleat Partial depth end-plate Fin-plate Secondary Primary beam ;;d~~6 ::~~ ~B @:. Figure 1.23 Simple Beam-to-Column Connection The flexibility of different bracing systems must be taken into account in the analysis, since the stiffer braces will attract a larger share of the applied lateral load. For tall and slender frames, the bracing system itself can be a sway frame, and a second-order analysis is required to evaluate the required forces for ultimate strength and serviceability checks. Lateral loads produce transverse shears, over turning moments and side sway. The stiffness and strength demands on the lateral system increase dramatically with height. The shear increases linearly, the overturning moment as a second power and sway as a fourth power of the height of the building. Therefore, apart from providing the strength to resist lateral shear and overturning moments, the dominant design consideration (especially for tall building) is to develop adequate lateral stiffness to control sway. For serviceability verification, it requires that both the inter- storey drifts and the lateral deflections of the structure as a whole must be limited. The limits depend on the sensitivity of the structural elements to shear deformations. Recommended limits for typical multistorey frames are given in Table 1.2. When considering the ultimate limit state, the bracing system must be capable of transmitting the factored lateral loads safely down to the foundations. Braced bays should be effective throughout the full height of the building. If it is essential for bracing to be discontinuous at one level, provision must be made to transfer the forces to other braced bays. Where this is not possible, torsional forces may be induced, and they should be allowed for in design. Figure 1.27 shows an example of a building which illustrates the locations at vertical braced trusses provided at the four corners to achieve lateral stability. Diaphragm Lateral Load (a) Sideswayof Unbraced Frame 21 action is provided by lightweight concrete slab which acts compositely with metal decking and floor beams. The floor beam-to-column connections are designed to resist shear force only as shown in the figure. 1.4.4 MOMENT-RESISTING FRAMES In cases where bracing systems would disturb the functioning of the building, rigidly jointed moment resisting frames can be used to provide lateral stability to the building, as illustrated in Fig. 1.28a. The efficiency of developing of lateral stiffness is dependent on bay span, number of bays in the frame, number of frames and the available depth in the floors for the frame girders. For building with heights not more than three times the plan dimension, the moment frame system is an efficient form. Bay dimensions in the range of 6m to 9 m and structural height up to 20-30 storeys are commonly used. However, as the building height increases, deeper girders are required to control drift, thus the design becomes uneconomical. When a rigid unbraced frame is subjected to lateral load, the horizontal shear in a storey is resisted predominantly by the bending of columns and beams. These deformations cause the frame to deform in a shear mode. The design of these frames is controlled therefore by the bending stiffness of individual members. The deeper the member, the more efficiently the bending stiffness can be developed. A small part of the frame side sway is caused by the overturning of the entire frame resulting in shortening and elongation of the columns at opposite sides of the frame. For unbraced rigid frames up to 20-30 storeys, the overturning moment contributes for about 10-20% of the total sway, whereas shear racking accounts for the remaining 80-90% (Fig. 1.28b). However, the storey drift due to overall bending tends to increase with height, while that due to shear racking tends to decrease. Shear Racking Component (b) Column Shortening Component Figure 1.28 Side away resistance of a rigid unbraced frame 22 1.4.4.1 Drift Assessment Since shear racking accounts for most of the lateral sway, the design of such frames should direct towards minimizing the side sway due to shear. The shear displacement L'1 in a typical storey in a multistorey frame, as shown in Fig. 1.29, can be approximated by the equation: Vh2 ( 1 1 ) L'1; = 1~~ :l:(Ici /hJ + :l:(Igi ILJ (1.4) where !1; = is the shear deflection of the i-th storey E = modulus of elasticity I , I = second moment of area for columns and girders c, g respectively h; = height of the ith storey L = length of girder in the i-th storey v' = total horizontal shear force in the ith storey l I,(IJh) = sum of the column stiffness in the i-th storey I,(I /L) = sum of the girder stiffness in the i-th storey gt l Examination of Eq. 1.4 shows that side-sway deflection caused by storey shear is influenced by the sum of column and beam stiffness in a storey. Since for multistorey construction, span lengths are generally larger than the storey height, the moment of inertia of the girders needs to be larger to match the column stiffness, as both of these members contribute equally to the storey drift. As the beam span increases, considerably deeper beam sections will be required to control frame drift. Since the gravity forces in columns are cumulative, larger column sizes are needed in lower stories as the frame height increases. Similarly, storey shear forces are cumulative, and therefore, larger beam properties in lower stories are required to control lateral drift. Because of limitations in available depth, heavier beam members will need to be provided at lower floors. This is the major shortcoming of unbraced frames because considerable premium for steel weight is required to control lateral drift as building height increases. V; r r r r1~2 JT z Jr (a) (b) A 2 112 J/2 Figure 1.29 Story drift due to (a) bending of columns (b) bending of girders Apart from the beam span, height-to-width ratios of the building play an important role in the design of such structure. Wider building frames allow a larger number of bays (i.e. , larger values for storey summation terms I CIJ h) and I,(I /L) in Eq. 1.4) with consequent reduction in I g 1 1 frame drift. Moment frames with closed spaced columns which are connected by deep beams are very effective in resisting side-sway, This kind of framing system is suitable for use in the exterior planes of the building. 1.4.4.2 Moment Connections Fully welded moment joints are expensive to fabricate. To minimize labor cost and to speed up site erection, field bolting instead of site welding should be used. Figure 1.30 shows several types of bolted or welded moment connections that are used in practice. Beam-to-column flange connections can be shop-fabricated by welding of a beam stub to an end plate or directly to a column. The beam can then be erected by field bolting the end plate to the column flanges or splicing beams (Fig.1.3C)c and 1.30d). An additional parameter to be considered in the design of columns of an unbraced frame is the "panel zone" between the column and the transverse framing beams. When an unbraced frame is subjected to lateral load, additional shear forces are induced in the column web panel as shown in Fig. 1.31 . The shear force is induced by the unbalanced moments from the adjoining beams causing the joint panel to deform in shear. The deformation is attributed to the large flexibility of the unstiffened column web. To prevent shear deformation so as to maintain the moment joint assumption as assumed in the global analysis, it may be Figure 1.30 (a) (b) Beam Stub (cl (d) (a) Bolted and welded connection with a doubler plate (b) Bolted and welded connection with a diagonal stiffener (c) Bolted end-plate connection (d) Beam stub welded to a column (a) (b) Figure 1.31 Forces acting on a panel joint (a) balanced moment due to gravity load (b) unbalanced moment due to latera/load necessary to stiffen the panel zone using either a doubler plate or a diagonal stiffener as shown in the joint details in Figs. 1.30a and 1.30b. Otherwise, a heavier column with larger web area is required to prevent excessive shear deformation, and this is often the preferred method as stiffeners and doublers can add significant costs to fabrication. The engineer should not specify full-strength moment connections unless they are required for ductile frame design for high seismic loads. For wind loads and for conventional moment frames where beams and columns are sized for stiffness (drift control) instead of strength, full strength moment connections are not required. Even so, many designers will specify full strength moment connections, adding to the cost of fabrication. Designing for actual loads has the potential to reduce column weight or reduce the stiffener and doubler plate requirements. If the panel zone is stiffened to prevent inelastic shear deformation, the conventional structural analysis based on the member center-line dimension will generally overestimate the frame displacement. If the beam-column joint sizes are relatively small compared to the member spans, the increase in frame stiffness using member center- line dimension will be offset by the increase in frame deflection due to panel-joint shear deformation. If the joint sizes are large, a more rigorous second-order analysis, which considers panel zone deformations, may be required for an accurate assessment of the frame response. 1.4.4.3 Analysis And Design of Unbraced Frames Multistorey moment frames are statically indeterminate, the required design forces can be determined using either: ( 1) elastic analysis or (2) plastic analysis. Whilst elastic methods of analysis can be used for all kind of steel sections, plastic analysis is only applicable for frames whose members are of plastic sections so as to enable the development of plastic hinges and to allow for inelastic redistribution of forces. 23 First-order elastic analysis can be used only in the following cases: 1) Where the frame is braced and not subjected to side sway. 2) Where an indirect allowance for second-order effects is made through the use of moment amplification factors and/or the column effective length. Eurocode 3 requires only second-order moment or effective length factor to be used in the beam-column capacity checks. However, column and frame imperfections need to be modeled explicitly in the analysis. In the American Standard (AISC LRFD), both factors need to be computed for checking the member strength and stability, and the analysis is based on structures without initial imperfections. The first-order elastic analysis is a convenient approach. Most design offices possess computer software capable of performing this method of analysis on large and highly indeterminate structures . As an alter~ative, hand calculations can be performed on appropriate sub-frames within the structure (see Figure 1.32) comprising a significantly reduced number of members. However, when conducting the analysis of an isolated sub-frame it is important that: 1) The sub-frame is indeed representative of the structure as a whole. 2) The selected boundary conditions are appropriate. 3) Account is taken of the possible interaction effects between adjacent sub-frames. 4) Allow for second-order effects through the use of column effective length or moment amplification factors. Plastic analysis generally requires more sophisticated computer programs, which enable second order effects to be taken into account. For building structures in which the required rotations are not calculated, all members containing plastic hinges must have plastic cross-sections. A basic procedure for the design of an unbraced frame is as follows: 1) Obtain approximate member size based on gravity load analysis of sub-frames shown in Fig. 1.32. If side- sway deflection is likely to control (e.g., slender frames) use Eq. 1.4 to estimate the member sizes. 2) Determine wind moments from the analysis of the entire frame subjected to lateral load. A simple portal wind analysis may be used in lieu of the computer analysis. 3) Check member capacity for the combined effects of factored lateral load plus gravity loads. 4) Check beam deflection and frame drift. 5) Redesign the members and perform final analysis/ design check (a second-order elastic analysis is preferable at the final stage). The need to repeat the analysis to correspond to changed section sizes is unavoidable for highly redundant rames. Iteration of Steps 1 to 5 gives results that will converge to 26 more pronounce towards the top of the frame. The braced truss is restrained by the moment frame at the upper part of the building while at the lower part, the moment frame is restrained by the truss frame. This is because the slope of frame sway displacement is relatively smaller than that of the truss at the top while the proportion is reversed at the bottom. The interacting forces between the truss frame and moment frame, as shown in Fig. 1.36, enhance the combined moment-truss frame stiffness to a level larger than the summation of individual moment frame and truss stiffnesses. Braced trame Figure 1.36 (a) (b) Behavior of frames subjected to lateral load (a) independant behavior (b) interactive behavior 1.4.5.3 Outrigger and Belt Truss Systems Another significant improvement of lateral stiffness can be obtained if the vertical truss and the perimeter shear frame are connected on one or more levels by a system of outrigger and belt trusses. Figure 1.37 shows a typical example of such system. The outrigger truss leads the wind forces of the core truss to the exterior columns providing cantilever behavior of the total frame system. The belt truss in the facade improves the cantilever participation of the exterior frame and creates a three-dimensional frame behavior. Figure 1.38 shows a schematic diagram that demonstrates the sway characteristic of the overall building under lateral load. Deflection is significantly reduced by the introduction of the outrigger-belt trusses. Two kinds of stiffening effects can be observed; one is related to the participation of the Section a-a Figure 1.37 Outrigger and belt-truss system external columns together with the internal core to act in a cantilever mode; the other is related to the stiffening of the external facade frame by the belt truss to act as a three- dimensional tube. The overall stiffness can be increased up to 25% as compared to the shear truss and frame system without such outrigger-belt trusses. The efficiency of this system is related to the number of trussed levels and the depth of the truss. In some cases the outrigger and belt trusses have a depth of two or more floors. They are located in services floors where there are no requirements for wide open spaces. These trusses are often pleasingly integrated into the architectural conception of the facade. 1.4.5.4 Frame Thbe Systems Figure 1.39 shows a typical frame tube system, which consists of a frame tube at the exterior of the building and gravity steel framing at the interior. The framed tube is constructed from wide columns placed at Close centers connected by deep beams creating a punched wall appearance. The exterior frame tube structure resists all lateral loads of wind or earthquake whereas the gravity steel framing in the interior resist only its share of gravity loads. The behavior of the exterior frame tube is similar to a hollow perforated tube. The over-turning moment under the action of lateral load is resisted by compression and tension of the leedward and windward columns, which are called the flange columns. The shear is resisted by bending of the columns and beams at the two sides of the building parallel to the direction of the lateral load, which are called the web frames. Sway with core truss + outrigger Sway with core truss alone Figure 1.38 Improvement of lateral stiffness tlsing outrigger-belt truss system ' X (a) Erection column 11--.!.10-+-Steel spandrel Compos~e column Column vertical reinforcement Column ties (b) Figure 1.39 Composite tubular system Deepening on the shear rigidity of the frame tube, there may exist a shear lag across the windward and leeward sides of the tube. As a result of this, not all the flange columns resist the same amount of axial force. An approximate approach is to assume an equivalent column model as shown in Fig. 1.40. In the calculation of the lateral deflection of the frame tube it is assumed that only the equivalent flange columns on the windward and leeward sides of the tube and the web frames would contribute to the moment of inertia of the tube. The use of exterior framed tube has two distinct advantages: ( 1) It develops high rigidity and strength for torsional and lateral-load resistance, since the structural components are effectively placed at the exterior of the building forming a three-dimensional closed section. (2) Massiveness of frame tube system eliminates potential uplift difficulties and produces better dynamic behavior. (3) The use of gravity steel framing in the interior has the advantages of flexibility, and enables rapid construction. If composite floor with metal decking is used, electrical and mechanical services can be incorporated in the floor zone. Composite columns are frequently used in the perimeter of the building where the closely spaced columns work in conjunction with the spandrel beam (either steel or concrete) to form a three-dimensional cantilever tube rather than an assembly of two-dimensional plane frames. The exterior frame tube significantly enhances the structural efficiency in resisting lateral loads and thus reduces the shear wall requirements. However, in cases where a higher magnitude of lateral stiffness is required (such as for vary tall buildings), internal wall cores and interior columns with floor framing can be added to transform the system into a 27 tube-in-tube system. The concrete core may be strategically located to recapture elevator space and to provide transmission of mechanical ducts from shafts and mechanical rooms. 1.4.6 STEEL-CONCRETE COMPOSITE SYSTEMS Steel-concrete composite construction has gained wide acceptance as an alternative to pure steel and pure concrete construction. Composite building systems can be broadly categorized into two forms : one utilizes the core-braced system by means of interior shear walls, and the other utilizes exterior framing to form a tube for lateral load resistance. Combining these two structural forms will enable taller buildings to be constructed. For composite frames resisting gravity load only, the beam- to-column connections behave as pinned before the placement of concrete. During construction, the beam is designed to resist concrete dead load and the construction load (to be treated as temporary live load). At the composite stage, the composite strength and stiffness of the beam should be utilized to resist the full design loads. For gravity frames consisting of bare steel columns and composite beams, there is now sufficient knowledge available for the designer to use composite action in the structural element as well as the semi-rigid composite joints to increase design choices, leading to more economical solutions. Figures 1.41 a&b show the typical beam-to-column connections, one using flushed end-plate bolted to the column flange and the other using bottom angle with double web cleats. Composite action in the joint is developed based on the tensile forces developed in the rebars acting with the balancing compression forces transmitted by the lower portion of the steel section that bear against the column flange to form a couple. Properly designed and detailed composite connections are capable of providing moment resistance up to the hogging resistance of the connecting members. Distribution without ~~j---~t~~~t:~~:l Ill m m--Equivolent w--__---=-:. =-- 'W axial stress -;- -~-----'- t t t Lateral force Distribution without shear log Figure lAO Equivalent column model for frame tube 28 Figure 1.41 (a) (b) Composite beam-to-column connections with (a) flushed end plate (b) seat and double web angles In designing the connections, slab reinforcements placed within a horizontal distance of 6 times the slab depth are assumed to be effective in resisting the hogging moment. Reinforcement steels that fall outside this width should not be considered in calculating the resisting moment of the connection (see Fig. 1.42). The connections to edge columns should be carefully detailed to ensure adequate anchorage of re-bars. Otherwise they shall be designed and detailed as simply supported. In braced frame a moment connection to the exterior column will increase the moments in the column, resulting in an increase of column size. Although the moment connections restrain the column from buckling by reducing the effective length, this is generally not adequate to offset the strength required to resist this moment. For an unbraced frame subjected to gravity and lateral loads, the beam typically bends in double curvature with negative moment at one end of the beam and positive moment on the other end. The concrete is assumed to be ineffective in tension, therefore only the steel beam stiffness on the negative moment region and the composite stiffness on the positive moment region can be utilized for frame action. The frame analysis can be performed with variable moment of inertia for the beams. Further research is still needed in order to provide tangible guidance for design. If semi-rigid composite joints are used in unbraced frames, the flexibility of the connections will contribute to additional drift over that of a fully rigid frame. In general, semi-rigid connections do not require the column size to be increased significantly over an equivalent rigid frame. This is because the design of frames with semi-rigid composite joints takes advantage of the additional stiffness in the beams provided by the composite action. The increase in beam stiffness would partially offset the additional flexibility introduced by the semi-rigid connections. Further research is required to assess the performance of various types of composite connections used in building construction. Issues related to accurate modeling of effective stiffness of composite members and joints in unbraced frames for the computation of second-order effects and drifts need to be addressed. ' ---!.. • • (a) Connection detail Projection ;, 0.2L J• • (b) Reinforcement detail l) U bars Effective breadth of slab S6D, at edge columns Figure 1.42 Moment transfer through reinforcerent at perimeter columns ADDITIONAL REFERENCES AISC (1993) Load and Resistance Factor Design Specification for Structural Steel Buildings, American Institute of Steel Construction, 2nd Ed., Chicago, Illinois. BS5950: Part 1 (1990), Structural use of steelwork in building Part 1: Code of Practice for design in Simple and Continuous Construction: Hot Rolled Section, British Standards Institution, London. Council On Tall Buildings and Urban Habitat (1995) Architecture of Tall Buildings, Edited by P J Armstrong, McGraw-Hill, 750pp. Eurocode 3 (1992) Design of Steel Structures: Part 1.1 -- General Rules and Rules for Buildings, National Application Document for use in the UK with ENV1993- 1-l: 1991, Draft for Development. Eurocode 4 (1994) Design of composite steel and concrete structures: general rules for buildings, preENV 1994-1-1, European Committee for Standardization. Iyengar, S.H., Baker, W.F. and Sinn, R. (1992), Multi-Story Building, In Constructional Steel Design, An International Guide, Chapter 6.2, Editors, P J Dowling et al., Elsevier, UK, 645-670. Johnson R P (1994), Composite construction of steel and concrete, Vol. 1, Blackwell Scientific Publications, 210pp. Knowles, P. R. (1985) Design of castellated beams, The Steel Construction Institute. 31 Lawson, R. M. and McConnel, R. E. (1993), Design of stub girders, The Steel Construction Institute, UK. Leon R. T., Hoffman, J.J., and Staeger, T. (1996) Partially restrained composite connections, AISC Steel Design Guide Series 8, AISC, 59pp. Liew, J Y R, Balendra T and Chen W F, ( 1997) Multistorey frame structures. In Section I 2: Handbook of Structural Engineering, edited by WF Chen, pp.12-1-12-73. United States: CRC Press, Boca Raton. Liew, J Y Rand Chen W F (1997), LRFD- Limited design of frames . In Chapter 6 of Steel Design Handbook: LRFD -Method, edited by A Tamboli, pp.6-1-6-83. United States: McGraw-Hill. Mullett D L (1998), Composite floor system, Blackwell Scientific Publications, 311 pp. Neals, S. and Johnson, R. (1992) Design of composite trusses, The Steel Construction Institute, UK. Owens, G (1989). Design of fabricated composite beams in buildings, The Steel Construction Institute, UK. Owens, G.W. and Knowles, P.R. (1992), Steel Designers' Manual, 5th Edition, Black Scientific Publications. Taranath, B.S. (1998), Structural analysis and design of tall building, McGraw-Hill Book Company, NY, 739pp. SECTION 2 BUILDABLE DESIGN AND QUALITY ASSESSMENT OF STEEL STRUCTURES 34 2.1. BUILDABLE DESIGN APPRAISAL SYSTEM The concept of buildable design was introduced by the Building and Construction Authority (BCA) to address the issues of low site productivity and over dependence on unskilled foreign workers. A Buildable Design Appraisal System (BDAS) was developed to provide a measure of the potential impact of a design on the usage of site labour. The appraisal system results in a buildability score of the design. The computation of buildability score depends on the types of structural and architectural systems used and the manpower consumption. The maximum buildability score achievable is 100 points. A design with a higher buildability score will result in more efficient labour usage during construction and therefore higher site labour productivity. 2.2 LEGISLATION OF BUILDABLE DESIGN A 5 year programme to promote the use of buildable design among public sector agencies was initiated in 1993. There were significant improvements in the buildability of public sector projects over the last 6 years. However, the private sector has been slow in adopting buildable designs despite the regular promotional efforts that include seminars, exhibitions and overseas study trips. This is due to the ready availability of a large pool of low cost foreign labour and insufficient incentives for the construction industry to ensure that the designs and construction methods minimise the use of labour. Legislation was thus recommended to accelerate the adoption of buildable design to improve productivity. A new provision in the Building Control Act came into effect on 1 April1999. It paved the way for BCA to legislate minimum buildability score requirement. On 29 April 1999, the former Minister for National Development announced during the BCA Awards ceremony that Table 2.1 Structural steel systems minimum buildability score would become part of the requirements for building plan (BP) approval from 1 January 2001. The legislation of minimum buildability score was also one of the recommendations in the Construction 21 Report which was released in October 1999. 2.3 BUILDABILITY OF STEEL STRUCTURES There are several reasons for the favorable use of structural steel construction. The first is that the speed of construction is faster. A structural steel building can be constructed in 80% of the time it takes to construct a reinforced concrete building. The steel is fabricated off site and assembled at the site later. Construction is thus not subjected to the vagaries of the weather. In fact, fabrication can commence even before foundation work begins. Secondly, structural steel construction does not require a huge storage space on site. Prefabrication of 2 or 3 floors can be carried out off site and delivered as and when the site is ready. This is an important factor for buildings found in the city centre where construction sites are congested and site access is limited. Thirdly, the design of some buildings , especially commercial and institutional buildings, requires long spanning beams for column free space. Steel, which has a higher strength to weight ratio is highly appropriate for these buildings. Lastly, steel fabrication involves higher technical skills when compared to reinforced concrete construction. It allows for greater degree of automation and less reliance on unskilled workers . Thus, it reduced the number of unskilled workers that the contractors need to employ. This is also in line with the government's policy in reducing the number of foreign unskilled labour. (Assume that structural steel is used in 80% of total floor area) Structural System %Area Labour Saving Buildability Score Index Steel beam with column sprayed fire proofed and: cast in place slab on steel 80% 0.95 38.0 decking precast concrete slab 80% 0.90 36.0 Steel beam with column encased in concrete and: cast in place slab on steel 80% 0.85 34.0 decking precast concrete slab 80% 0.80 32.0 "' '·;; ;! 1!3 ~ z FA z ra 3. 1 S te el B ui ld in gs C om pl et ed b et w ee n 19 98 a n d 2 00 0 T h e st ee l b ui ld in gs t ha t w er e co m pl et ed b et w ee n 19 98 a nd 2 00 0 ar e li st ed i n T ab le 3 .1 . T h e m ai n fe at ur es o f th es e bu il di ng s ar e al so s um m ar iz ed i n t he t ab le . T ab le 3 .1 D et ai ls o f S te el B ui ld in gs C om pl et ed b et w ee n 19 98 a n d 2 00 0 P ro je ct ti tl e P ro je ct P ro je ct T yp es o f P ar t o f bu il di ng H ei gh t o f S pe ci al r eq u ir em en t o f b ui ld in g B ui ld ab il it y co m m . D at e co m pl . D at e st ru ct u ra l st ee l us in g st ru ct u ra l st ee l bu il di ng sc or e sy st em u se d co ns tr uc ti on C ap it al T ow er F eb 9 7 Ju n 20 00 S tr uc tu ra l . F ul l b ui ld in g . 52 s to re ys . B ui ld in g re qu ir es c ol um n fr ee s pa ce 79 st ee l fr am e . T ot al h ei gh t w it h m ax im um lo ng s pa n st ee l an d in te rn al o f 2 60 m tr us se s at 1 8m a nd s te el b ea m s at co re w al l 11 .5 m . C ha ng i A ir po rt Ju l9 7 O ct 9 9 S tr uc tu ra l • 2" d an d m ez za ni ne . 2 fi ng er • B ui ld in g re qu ir es l on g sp an c ol um n 78 T er m in al ! st ee l fr am e st or ey s fo r bu il di ng o f 2 fr ee s pa ce s & h ig h ce il in gs . an d st ee l co nc es si on a re a st or ey s. . T he c on ce ss io n ar ea s ar e la rg el y ro o f . S te el r oo f f ra m in g • T ot al h ei gh t co lu m n fr ee , hi gh v ol um e sp ac es . P as se ng er lo ad in g o f 14 .9 m pr ov id in g an a tt ra ct iv e en vi ro nm en t br id ge ex ce pt a t fo r p as se ng er s to e at & s ho p . co nc es si O n . N ew g en er at io n st ee l f ix ed ar ea w hi ch is ga ng w ay s w er e re qu ir ed t o co nn ec t 22 .6 m . th e bu il di ng s to t he w ai ti ng a ir cr af t. S ta rh ub C en tr e N ov 9 6 N ov 9 8 S tr uc tu ra l . F ul l B ui ld in g . 10 s to re ys . T he b ui ld in g re qu ir es l on g sp an 76 st ee l fr am e be am o f 13 .7 m ; t he a ve ra ge s pa n o f w it h w in d be am s is a bo ut 8 .6 m . br ac in g O ne R af fl es Ja n 9 8 N ov 9 9 S tr uc tu ra l . B ui ld in g ab ov e . 8 st or ey s & 2 . T he b ui ld in g ne ed s to a cc om m od at e 76 L in k st ee l f ra m e gr ou nd l ev el ba se m en ts m aj or i nt er na ti on al f in an ci al w it h w in d . T ot al h ei gh t o f in st it ut io ns r eq ui ri ng l ar ge o ff ic e br ac in g 4 lm fl oo r pl at es a nd f le xi bl e co lu m n fr ee s pa ce . S in ga po re P os t M ay 9 4 M ay 9 9 S tr uc tu ra l • T he m ai n sp or ts . 14 s to re ys a nd 59 C en tr e st ee l fr am e ha ll w hi ch w as 3 ba se m en ts su sp en de d . T ot al h ei gh t o f ab ov e th e ro of . 55 .5 m z ·- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~ ~ ~ (5 ~ 3. 2 St ee l B ui ld in gs C om pl et ed B ef or e 19 97 T h e st ee l bu il di ng s th at w er e co m p le te d b ef or e 19 97 a re l is te d in T ab le 3 .2 . T h e m ai n f ea tu re s o f th es e bu il di ng s ar e al so s u m m ar iz ed i n th e ta bl e. T ab le 3 .2 D et ai ls o f S te el B ui ld in gs C om pl et ed B ef or e 19 97 P ro je ct t it le P ro je ct c om m . P ro je ct T yp es o f P ar t of b u il d in g us in g H ei gh t of fu ll Sp ec ia l re q u ir em en t of B u il d ab il it y D at e co m pl . D at e st ru ct ur al s te el st ru ct u ra l st ee l b u il d in g b u il d in g sc or e sy st em u se d co n st ru ct io n R ep ub li c F eb 9 2 Ja n 96 S tr uc tu ra l . F ul l bu il di ng . 66 s to re ys w it h I T he b ui ld in g w as d es ig ne d fo r 72 P la za st ee l fr am e ba se m en t th e C B D f in an ci al i ns ti tu ti on s w it h in te rn al . T ot al h ei gh t o f an d ho us es a s op hi sc at ed co re w al l 28 0m bu il di ng a ut om at io n sy st em w hi ch i nt eg ra te s li ft c on tr ol , ac ce ss c on tr ol , se cu ri ty s ys te m , fi re a la rm s ys te m , a ir co nd it io ni ng a n d el ec tr ic al eq ui pm en t. U E S qu ar e Ja n 95 D ec 9 7 S tr uc tu ra l • O ff ic e bl oc k o n ly . 18 s to re ys o ff ic e A c om rn er ic al o ff ic e bu il di ng 58 st ee l fr am e bl oc k m ad e o f ef fi ci en t st ee l fr am e . 15 s to re ys s er v ic e sy st em , co re w al ls , ap ar tm en t & 1 8 co lu m n a nd s te el b ea m s, st or ey s re si de nt ia l w h ic h a ll ow s er vi ce s to p as s ap ar tm en t w it h 3 th ro ug h th e st ru ct ur al z on e. ba se m en ts O U B C en tr e Ju n 8 1 Ju n 86 S tr uc tu ra l st ee l . F ul l bu il di ng • 66 s to re ys T he t ow er r eq ui re s as a sp ec t 71 fr am e . T ot al ra ti o (h ei gh t to w id th ) as h ig h as he ig ht o f 10 a nd c ol um n fr ee s pa ce 28 0m th ro ug h it s fu ll he ig ht . A n ef fi ci en t st ru ct ur al s ys te m , co m pr is in g o f s te el tr us se s, w hi ch a llo w ed s er vi ce s to p as s th ro ug h fr ee ly w it ho ut a de di ca te d se rv ic es z o ne , w as u se d . 3. 3 St ee l B ui ld in gs - D es ig n T ea m s T h e cl ie nt s, a rc hi te ct s, e ng in ee rs a nd c on tr ac to rs f or t he s te el b ui ld in gs f ea tu re d ar e li st ed i n T ab le 3 .3 . T ab le 3 .3 D es ig n T ea m s of S te el B ui ld in gs P ro je ct t it le C li en t A rc h it ec t E n gi n ee r C on tr ac to r C ap it al T ow er C ap it al T ow er P te L td R S P A rc hi te ct P la nn er s & M au ns el l C on su lt an ts ( S) P te S sa ng yo ng E ng in ee ri ng & E ng in ee rs P te L td L td C on st ru ct io n C o. L td C ha ng i A ir po rt T er m in al 1 C iv il A vi at io n A ut ho ri ty o f P W D C on su lt an ts P te L td P W D C on su lt an ts P te L td T ak en ak a C or po ra ti on S in ga po re S ta rh ub C en tr e C up pa ge C en tr e P te L td P & T C on su lt an ts P te L td M au ns el l C on su lt an ts ( S) P te S at o K og yo C o . L td L td O ne R af fl es L in k H K L ( E sp la na de ) P te L td K oh n P ed er se n F ox A ss oc ia te s M ei nh ar dt ( S) P te L td G am m on P te L td P C S in ga po re P os t C en tr e S in ga po re P os t P te L td R D C A rc hi te ct s P te L td O ve A ru p & P ar tn er s P en ta O ce an -L K H J .V . (S in ga po re ) R ep ub li c P la za C it y D ev el op m en ts L td K is ho K ur ok aw a A rc hi te ct s & R S P A rc hi te ct P la nn er s & S hi m iz u C or po ra ti on A ss oc ia te s/ R S P A rc hi te ct E ng in ee rs P te L td P la nn er s & E ng in ee rs P te L td U E S qu ar e U ni te d E ng in ee rs L td A rc hi te ct s 61 P te L td H C E E ng in ee rs P ar tn er sh ip K aj im a O ve rs ea s A si a P te L td O U B C en tr e O U B C en tr e L td S A A P ar tn er sh ip i n as so ci at io n B yl an de r M ei nh ar dt P ar tn er sh ip JD C C or po ra ti on w it h K en zo T an ge (S ) P te L td 44 Finger Buildings at C111angi Am Terminal 1 Client Civil Aviation Authority of Singapore Architect PWD Consultants Pte Ltd Engineer PWD Consultants Pte Ltd Main Contractor Takenaka Corporation Contract Sum S$167 million Features of structure The project comprises of the extension of 2 finger buildings, Piers C & D from the existing Terminal 1. They are 2 storey buildings. T he 1st storey houses equipment areas, plant rooms and rentable offices. T he 2nd storey is exclusively for passengers boarding and alighting from aircrafts parked next to the 7 passenger loading bridges provided at each pier. The addition of 2 Concession Areas and Transfer Areas to the existing Terminal 1 provide additional concession space for shops, cafe and restaurants. The buildings require long span column free spaces and Gross Floor Area 35,000 m2 Project Duration Jul 97- Oct 99 Location of building Terminal 1 Singapore Changi Airport Tonnage of structural steel used 5,800 ton Steel Grade Grade 43 and 50 high ceilings along the Arrival Changi Airport Terminal I and Departure Malls. T he column spacing is set at 18m apart. For fast and easy construction, roof steel trusses and stainless steel roofing with high sound transmissionJoss prove to be the most effective solution, especially in view of the long spans and high ceiling space. To maximize transparency of the interior, the sterile gate lounges are separated from the Arrival and Departure Mall with frameless glass partitions that help visually expand the space. T he twelve and half degree angle sloping external glazing walls and steel sunshading louvres enhance energy conservation and minimize glare in the buildings. New generation steel fixed gangways were designed to connect the buildings to the waiting aircraft. The gangways are hung from steel beams spanning up to 24 metres and have full glass facades to provide arriving and departing passengers an interesting view of the airfield. The concession areas are strategically positioned additions to the existing Terminal 1 to create more shops and restaurant facilities for the heavy flow of passengers which regularly pass these 2 concession junctions. The concession areas are largely column free, high volume spaces providing an attractive environment for passengers to eat and shop. The use of mainly steel for the column struts and steel roof frame allowed a long span light structure which minimized the disruption to existing roadways below the concession areas during and after construction. The roof and the skylight are supported by a steel space frame which in turn are propped up by clusters of inclined radiating steel struts from 2 column clusters at the perimeter. The skylights are suspended 13 meters above the shops at 2nd storey. The glass lifts were enclosed with glass panels fixed to square hollow section steel members. Steel Support at Concession Area Pier C 45 STEEL BUILDINGS IN SINGAPORE 46 Client Cuppage Centre Pte Ltd Architect P & T Consultants Pte Ltd Engineer Maunsell Consultants Pte Ltd Main Contractor Sato Kogyo Co Ltd Contract Sum S$68m Project Duration Nov 96 - Noc 98 Features of structure The Starhub Centre is a 10-storey building with retail shopping facilities at 1st storey and a food court at 2nd storey. The upper levels consist of office spaces with carparking facilities. The superstructure is a steel framed building with composite floor system using steel sheeting. The steel sheeting serves dual purposes as bottom reinforcement and formwork during construction. Additional steel reinforcements are provided to comply with fire resistance requirement. The composite slab thickness is 125mm spanning a maximum of 3.0m length. The composite beams are designed as simply supported beams between the steel columns. The lateral stability for the building is provided by concrete core wall supplemented by additional steel bracing frames located in the car park area. The steel beams are sprayed with fire protection system, and columns are encased by concrete. STEEL BUILDINGS IN SINGAPORE Location of building Cuppage Road Tonnage of structural steel used 3,000 ton Steel Grade Grade 43/50 The cellform beams are spaced at 9m intervals to reduce the span of the secondary floor beams. The secondary floor beams are spaced at 3m intervals, permitting the concrete slab to be cast over the metal decking without the need for any propping during construction. The services core of the building are elongated along the N-S axis because of the 18m clear span required in the centre of the floor plate. The elevator shafts of the service core have been utilized as lateral stability elements. The design approach for the core walls allowed the entire structural steel frame to be designed using simple construction method in which beam-to-column connections are _rin-joinred. 49 STEEL BUILDINGS IN SINGAPORE so Client Singapore Post Pte Ltd Architect RDC Architects Pte Ltd Engineer Ove Arup & Partners Singapore Main Contractor Penta Ocean LKH J. V. Contract Sum S$369m Features of structure The project, a flagship building of Singapore Post, is strategically located at Eunos Road 8, beside the Paya Lebar MRT stations. It comprises an open plaza, a 14-storey office and retail block and a 9-storey block to house the 24- hour mail and parcel processing hub. The superstructure comprised of reinforced concrete and structural steelwork. The sport hall, weighted about 1000 tons, was supported by two mega trusses spanning between the lift shafts. The maximum depth of the mega truss was about 13m. The trusses were assembled on the roof top and they were connected by transverse girders. The entire sport hall was jacked to the final position. Gross Floor Area 137,241 m2 Project Durations May 99 - May 99 Location of building 10 Eunos Road 8 Tonnage of structural steel used 7,000 ton Singapore Post Centre (Side View) STEEL BUILDINGS IN SINGAPORE Assembling of the sport hall structure on the roof top Overall View of Site in the East Direction Sport hall was lifted to the Final position 51 STEEL BUILDINGS IN SINGAPORE 54 Client United Engineers Ltd Architect Architects 61 Pte Ltd Engineer HCE Engineers Partnership Main Contractor Kajima Overseas Asia Pte Ltd Contract Sum S$250M Features of structure Gross Floor Area 17 1,360 m 2 Project Duration Jan 95 - Dec 97 Location of building River Valley Road/ Clemenceau Avenue Tonnage of structural steel used 1,800 ton Steel Grade Grade 50 The project is a mixture of residential and commercial development. It comprises of a 18 storey office building, a 15 storey service apartment and a 18 storey residential apartment with 3 basement carparks. Only the office building utilizes structural steel for its structural system. The vertical concrete core walls provide the necessary lateral stiffness for wind resistance. Composite slab, with metal decking used as permanent formwork, was adopted. i Openings were the bea~ we~:Lro allow passage -of M & E services. UE Square • 55 Construction of residential apartment and office block. Composite construction with steel decking used as permanent for~ work. STEEL BUILDINGS IN SINGAPORE 56 O·' u··· r-D) ~ t l. ) Client OUB Centre Ltd Architect SAA Partnership in association with Kenzo Tange Engineer Bylander Meinhardt Partnership (S) Pte Ltd Main Contractor J.D. C. Contract Sum S$300m Features of structure The project comprises of a 66-storey office building located at No. 1 Raffles Place. The tower which has an aspect (height to width) ratio as high as 10, provides column free space (20m x 41m) throughout its full ,height. An efficient structural system comprising of steel trusses, which allowed services to pass through freely without a dedicated services zone, was used to reduce floor height, steel tonnage and cost. Simply supported steel trusses 950mm deep spaced at 4.32m centres in an east-west direction support the large column-free areas. These trusses are designed. to act compositely with the concrete floor system. The floor system consists of a reinforced concrete slab composite with a 63mm :•'l ~U deep ribbed steel deck. The concrete ...::: - ·"»~ slab is 150mm thick to maintain a sufficient concrete thickness, after reticulation of services, for the required fire separation between levels. Fire protection of the steel frame is provided by light-weight mineral fiber. Gross Floor Area 83,127 m2 Project Duration Jan 81- Jan 86 Location of building No. 1 Raffles Place Tonnage of structural steel used 11,000 ton Steel Grade Grade 43 and 50 u un Ull' '"" . .,., ''·'" ttm ""' .,., ~ ~ ... ,, ... ,~ .. ''""'' '" ..... ""''' '"'!•• "!!'~"' ...... , ~~·~" ........ .,.,., .. .. ,.,, . ., I I u I I • B H }J II u u II II 11 .. .. It .. It .. .. u .. .. .. -· 4. 1 St ee l R oo fs ( C om pl et ed b et w ee n 1 99 8 an d 20 00 ) T he s te el b ui ld in gs t ha t w er e co m pl et ed b et w ee n 19 98 a nd 2 00 0 ar e li st ed i n T ab le 4 .1 . T he m ai n fe at ur es o f th es e bu il di ng s ar e al so s um m ar iz ed in th e ta bl e. T ab le 4 .1 D et ai ls o f S te el R oo fs ( C om p le te d b et w ee n 1 99 8 an d 20 00 ) P ro je ct t it le P ro je ct c om m . P ro je ct c om p l. S p ec ia l re q u ir em en t o f ro of s tr u ct u re D at e D at e E xp o M R T S ta ti on Ju l9 8 Ja n 20 01 . O ve ra ll p la n di m en si on o f ro o f= 2 00 m x 2 9m . T he p ro je ct r eq ui re s th at th e sh el l ro o f s tr uc tu re b e le ft e xp os ed to v ie w a nd t ha t a ve ry h ig h qu al it y fi ni sh es s ch ed ul e fo r ro o f & c ei li ng to b e ap pl ie d. G ra nd st an d o f N ov 9 6 M ay 9 9 . O ve ra ll p la n di m en si on o f r o o f= 1 60 m x 5 6m S in ga po re . T he r o o f s tr uc tu re is a 5 6m r o o f t ru ss c an ti le ve ri ng 2 6m a nd s us pe nd in g 2 tr ac ks id e vi ew in g R ac ec ou rs e le ve ls . S in ga po re E xp o S ep 9 7 A p r9 9 . O ve ra ll p la n di m en si on o f r o o f p er h al l= 9 6m x 9 6m ( 6 ha ll s al to ge th er ) . T he r o o f s tr uc tu re r eq ui re s an u no bs tr uc te d sp an o f 9 6m i n bo th d ir ec ti on s fo r ea ch h al l. It c ov er s a co lu m n fr ee e xh ib it io n ar ea o f I 0 ,0 00 m 2. 4. 2 St ee l R oo fs ( C om p le te d b ef or e 19 97 ) T he s te el r oo fs t ha t w er e co m pl et ed b ef or e 19 97 a re l is te d in T ab le 4 .2 . T h e m ai n fe at ur es o f th es e bu il di ng s ar e al so s um m ar iz ed in t he t ab le . T ab le 4 .2 D et ai ls o f S te el R oo fs ( C om p le te d b ef or e 19 97 ) P ro je ct t it le P ro je ct c om m . P ro je ct c om p l. S p ec ia l re q u ir em en t of r oo f s tr u ct u re D at e D at e B is ha n S po rt s M ay 9 6 N ov 9 7 . O ve ra ll p la n di m en si on o f r oo f= 1 1O m x 6 0m S ta di um • T he s po rt s ha ll r oo f c om pr is es o f t w o l.O m d ia m et er t ub ul ar s te el a rc he s 88 m l on g an d 14 .5 m hi gh . T hr ee l en s tr us se s sp an ni ng 3 8m , a ga bl e en d tr us s an d m in or l en s tr us s fo rm s th e sl op in g ga bl e en ds . S in ga po re O ct 9 0 D ec 9 4 . O ve ra ll p la n di m en si on o f r oo f= 1 73 m x 1 44 m In te rn at io na l . T he r oo f s tr uc tu re c om pr is ed o f a n ex te rn al f ul ly e xp os ed s pa ce f ra m e (e xo sk el et on ) an d a se ri es C on ve nt io n an d o f s ec on da ry r oo f s tr uc tu re s su sp en de d fr om t he e xo sk el et on t o w hi ch t he r oo f c la dd in g sy st em E xh ib it io n C en tr e ar e at ta ch ed . K ep pe l D is tr ic t P ar k M ar 9 2 Ju l9 4 . O ve ra ll p la n di m en si on o f r oo f= 4 l ar ge b lo ck s o f 2 90 m 2 & 2 s m al l bl oc ks o f 2 60 m 2 . . T he p er m an en t ro of s up po rt s ys te m c om pr is es c ab le s ta y an d in te rm ed ia te s te el c ol um ns a t gr id sp ac in g o f 4 8m x 4 0m . T he c ab le s ta y is m ad e up o f 4 8 di am et er s ta in le ss s te el r od s w hi ch s pa n 16 m f ro m t he t op o f t he m ai n m as t to i nt er m ed ia te s up po rt p oi nt s on t he r oo f. S in ga po re I nd oo r D ec 8 7 Ja n 90 . O ve ra ll p la n di m en si on o f r oo f= 2 15 m x 1 28 m S ta di um . T he r oo f s tr uc tu re c om pr is es p ai rs o f c ur ve d w el de d ke el t ru ss es , w ith s pa ce f ra m e sp an ni ng be tw ee n th em , a lo ng t he l on gi tu di na l an d la ti tu di na l ax es . 4. 3 St ee l R oo fs - D es ig n T ea m s T h e cl ie nt s, a rc hi te ct s, e ng in ee rs a nd c on tr ac to rs f or t he s te el r oo fs f ea tu re d ar e li st ed in T ab le 4 .3 T ab le 4 .3 D es ig n T ea m s of S te el R oo fs · P ro .j ec t ti tl e C li en t A rc h it ec t E n ~ i n e e r C on tr ac to r E xp o M R T S ta ti on L an ds T ra ns po rt A ut ho ri ty F os te r & P ar tn er s (S ) P te L td L an ds T ra ns po rt A ut ho ri ty P en ta O ce an / L & M o f S in ga po re o f S in ga po re P re st re ss in g J. V . G ra nd st an d o f S in ga po re S in ga po re T u rf C lu b In de co C on su lt an ts P te L td / In de co C on su lt an ts P te L td / S sa ng yo ng / G ua n H o J. V . R ac ec ou rs e E w in g, C ol e, C he rr y & B ro tt E w in g, C ol e, C h en y & B ro tt an d P ro f. L ee S en g L ip an d P ro f. L ee S en g L ip S in ga po re E xp o M in is tr y o f T ra de a nd I nd us tr y C ox G ro up P ty L td ( A us tr al ia )/ O ve A ru p A us tr al ia P ty L td ! H yu nd ai E ng in ee ri ng & L iu & W o A rc hi te ct s P te L td O ve A ru p S in ga po re P te L td C on st ru ct io n C o. L td B is ha n S po rt s S ta di um S in ga po re S po rt s C ou nc il S A A P ar tn er sh ip P te L td A lb er t L oh C on su lt an ts L im K ee rl y B ui ld er s P te L td S in ga po re I nt er na ti on al S un te c C it y D ev el op m en t D P A rc hi te ct P te L td M au ns el l C on su lt an ts ( S ) P te H y un da i E ng in ee ri ng & C on ve nt io n an d E xh ib it io n P te L td (P ro je ct A rc hi te ct ) L td C on st ru ct io n C o. L td a nd C en tr e (C iv il & S tr uc tu ra l E ng in ee r) S sa ng yo ng E ng in ee ri ng & C on st ru ct io n C o . L td K ep pe l D is tr ic t P ar k P S A P la nn in g & D es ig n D ep ar tm en t, P la nn in g & D es ig n D ep ar tm en t, L ow K en g H u at ( S ) P te L td E ng in ee ri ng D iv is io n, P S A E ng in ee ri ng D iv is io n, P S A A lf re d W on g P ar tn er sh ip P te A lf re d W on g P ar tn er sh ip P te L td L td S in ga po re I nd oo r S ta di um S in ga po re S po rt s C ou nc il K en zo T an ge A ss oc ia te s/ R S P R S P A rc hi te ct s Pl an ne rs & S sa ng yo ng E ng in ee ri ng & A rc hi te ct s P la nn er s & E ng in ee rs E ng in ee rs P te L td C on st ru ct io n C o . L td P te L td 65 Fabricated Diagrids Pre-assembly of Module Lifting of Assembled Module Lifting of Module Y-Column Temporary Support Tower Bolting at Module connections Completed Roof Module STEEL ROOF STRUCTURES IN SINGAPORE . 66 Grt~Jwlstt~Jnfi of Singap6re R~t~~t~tlJS~ -~ -~ Client Singapore Turf Club Architect Indeco Consultants Pte Ltd Ewing, Cole, Cherry & Brott and Pro£ Lee Seng Lip Engineer Indeco Consultants Pte Ltd Ewing, Cole, Cherry & Brott and Pro£ Lee Seng Lip Main Contractor Ssangyong/ Guan Ho J .V Total Contract Sum S$253m Features of structure The shape of the roof was evolved from the moving profile of a horse. The roof trusses were located at 9.6m column grids along the length of the grandstand building. There is a total of 19 numbers of 53.5m roof trusses, cantilevering 26.5m and supporting 2 levels of trackside viewing decks. To optimize sight lines, the steel floor framing at the 2 trackside viewing levels were supported by solid hanger bars pinned to the structural roof trusses. T he roof trusses were designed as plane frames & sized to control deflections of the long cantilever span. The trusses were further braced laterally by four transverse trusses and horizontal diaphragms. The 2 viewing decks comprised of 165mm thick composite floor supported on steel beam girders. Taking into the account the length of the grandstand building and crane working radius limit, 4 erection zones and assembly platform positions were allocated. A 450T crawler crane which has a maximum working radius of 46m was used to lift the roof trusses. Each roof truss was assembled using bolted connection splices at the assembly platform first. It was then lifted after careful inspection. The average cycle time for erecting 1 truss was 2 days. This would include the works on temporary bracing and tie beams. The total time used for erecting all the 19 roof trusses was about 2 months. Overall Plan Dimension of Roof 160m x 56m Project Duration Nov 96 - May 99 Location of building Next to Kranji MRT Tonnage of structural steel used 2,000 ton Steel Grade Grade 50 STEEL ROOF STRUCTURES IN SINGAPORE ·~· ~. STEEL ROOF STRUCTURES IN SINGAPORE Client Singapore Sports Council Architect SAA Partnership Pte Ltd Engineer Albert Loh Consultants Main Contractor Lim Keedy Builders Pte Ltd Contract Sum S$28m Plan Dimension of Roof 110m x 60m Project Duration May 96 - Nov 97 Location of building 5 Bishan Street 14 Tonnage of structural steel used 670 ton Steel Grade Grade 36 and 50 Features of structure The roof structure has a unique shape of which structural design concept was developed immediately after the architect finished the conceptual layouts. Thus the roof concept was actually completed before the main structure. This gave the architect and the owner a good overview on the appearance of the stadium at an early stage. T he stadium roof comprises of pairs of lens trusses suspended on tension rods over a 508mm diameter tubular steel column and anchored down at the back via tension rods, CHS members and driven steel piles. The lens trusses are approximately 26m long of which 18.1 m cantilevers over the grandstand. he sports hall comprises two l.Om diameter tubular steel arches 88m long and 14.5m high. Three lens trusses spanning 38m, a gable end truss and minor lens truss forming the sloping gable ends. The arches are inclined at an angle of approximately 45 degrees and are separated by CHS struts of lengths varying from 1.0m to 30.0m. The bases of the arches are tied together using tension rods longitudinally and 508mm diamet~r tubes transversely. The arches are essentially slides and moves on bearings at each of the four columns. The three. trusses are hung off the arches using CHS rods in the plane of tilt of the arch. 71 STEEL ROOF STRUCTURES IN SINGAPORE Roll Up Procedure Lifting of Sports Hall in Progress Stadium - North Elevation STEEL ROOF STRUCTIJRES IN SINGAPORE 75 ê E Ê á ê E 5 Ê é É g Hã  E Ee ac ~ · f n.r . ··· ., ll .IL 1\_eppe . vyistrict rlt1!'N: Client Port of Singapore Authority Architect Planning & Design Department, Engineering Division, PSA Alfred Wong Partnership Pte Ltd Engineer Planning & Design Department, Engineering Division, PSA Alfred Wong Partnership Pte Ltd Main Contractor Low Keng Huat (S) Pte Ltd Contract Sum for Steel Roofs S$29m Features of structure Overall Plan Dimension of Roof 4 large blocks each measuring 290m2 2 small blocks each measuring 260m2 Project Duration Mar 92 -July 94 Location of building The site is surrounded by Keppel Road, Kampong Bahru Road and the AYE. Tonnage of structural steel used 5,800 ton Steel Grade Grade 43 and 50 The roof structure is supported with widely spaced columns, each roof panel measuring 120m x 96m for the Type A roof and 70m x 96m for the Type B (smaller block) roof. This is to allow large column free spaces which is a requirement for this building. At the edge of the span frame trusses, there is a cantilever of just over 10m. The space frame has a structural depth of l.Sm. Tubular members are connected together using a proprietary ball-jointed system. The steel roof structure was assembled on the ground. The completed space frame roof was lifted up by motor hoisters controlled by a synchronized electric controlled cabinet. At a hoisting speed of 0.5m per minute, the whole roof was lifted up to a height of 15m above the 2nd storey level in just 30 minutes. Keppel District Park 77 STEEL ROOF STRUCTURES IN SINGAPORE t:t ;Wttg;~r.~ 'P· - l o,-e In l!oo. r· · S' tA rl!i~~~,m.· 7 . ~~l'lb ~' ~ fl '~!V .. " w>'at~ 7 -.~J _'Yf!Ab"~f!ll/t 7 ' ' . · ... Client Singapore SportS Council Architect Kenzo Tange Associates RSP Architects Planners & Engineers Pte Ltd Engineer RSP Architects Planners & Engineers Pte Ltd Main Contractor Ssangyong Engineering & Construction Co. Ltd Contract Sum for Steel Roof S$9.2m Features of structure Overall Plan Dimension of Roof 215m x 128m Project Duration Dec 87 - Jan 90 Location of building No. 2 Stadium Walk Tonnage of structural steel used 2,800 ton Steel Grade Grade 50 The steel space frame roof is supported on 58 perimeter steel columns and 2 pairs of internal steel columns to provide a 1OOm x 1OOm covered space with uninterrupted viewing of the central arena. The roof structure comprises pairs of curved welded keel trusses along the longitudinal and latitudinal axes, and 4 curved triangular space frames. Single axis rotation hinges were incorporated into the curved triangular space frame. This allowed the centre portion of the roof to be constructed in its folded position and then be lifted up by the Pantadome System. The high centre portion was lifted vertically whilst the lower portions of the roof were rotated into the final roof form. The Pantadome System was utilized in the erection process to shorten the construction period, reduce temporary staging and facilitate supervision work. This system also allowed uniform jacking down and removal of temporary supports thus preventing any uneven stressi g of\ the roof members. , g Z E E 5 x E x es Pd > [oa rá o) SECTION 5 COST OF STEEL STRUCTURES AND MATERIALS