建筑专业毕业设计外文翻译VIP

外文资料翻译 Contents lists available at ScienceDirect Journal of Constructional Steel Research Seismic analysis of the worlds tallest building Hong Fan a ,b, Q . S . Li a, A l e x Y . T u a n c, Lihua Xud a Department of Building and Construction, City University of Hong kong, Hong kong b China Nuclear Power Design Company, Shenzhen 518026, China c Department of Civil Engineering, Tam kang University, Taipei, Taiwan d School of Civil Engineering, Wuhan University, Hubei Wuhan 430072, China a r t i c l e i n f o Article history: Received 13 March 2008 Accepted 8 October 2008 keywords: Super-tall building Mega-frame structure Finite element modeling Seismic analysis Dynamics response Shaking table test a b s t r a c t Taipei 101 (officially known as the Taipei Financial Center) with 101 stories and 508 m height, located in Taipei where earthquakes and str o -ng typhoons are common occurrences, is currently the tallest bui lding in the world. The great height of the building, the special geog- raphic an -d environmental conditions, not surprisingly, presented one of the gre -atest challenges for structural engineers. In particular, its dynamic pe -rformance under earthquake or wind actions requires inte- nsive researc -h. The structure of the building is a mega-frame system composed of concrete filled steel tube (CFT) columns, steel brace core and belt trus -ses which are combined to resist vertical and lateral loads. In this stud -y, a shaking table test was conducted to determine the con - stitutive rel- ationships and finite element types for the CFT columns a- nd steel mem -bers for establishing the finite element (FE) model of the tall building. Then, the seismic responses of the super-tall building we- re numerically investigated. An earthquake spectrum generated for Ta- ipei Basin was a -dopted to calculate the lateral displacements and distributions of inter -ior column forces. Furthermore, time-history an- alyses of elastic and in -elastic seismic response were carried out using scaled accelerograms representing earthquake events with return perio - ds of 50-year, 100-year, and 950-year, respectively. The computational results indicate that the super -tall building with the megaframe system possesses substantial re -serve strength, and the high -rise structure wo- uld satisfy the design re- quirements under severe seismic events. The output of this study is ex -pected to be of cons ide ra ble interest and practical use to profession -nals and researchers involved in the design of super-tall buildings. 1. Introduction Owing to the growing use of high-strength materials and advanced co- nstruction techniques, building structures have become more and more flexible and taller. The increasing height of modern tall buildings po- sed a series of challenges for structural engineers. In the design of such a tall building, the structural system must meet three major require- ments: strength, rigidity, and stability 1.As is well known, the stre - ngth requirement is the dominant factorin the design of low -rise structures. However, as building height increases, the rigidity and stab - ility requirements become more im -portant, and they are often the dom - inant factors in the structural design. Especially under lateral loads, interior forces are quite vari able and increase rapidly with incre ases in height, and lateral deflection may vary as the fourth power of the height of a building 2,and structural dynamic behavior is thus one of the most importantdesign considerations in the design of a modern tall building Taipei 101, rising 508 m above the city of Taipei, e arns the title of the tallest building in the world. Its dynamic responses due to wind, ea- rthquake and other extraordinary loads are of great concern. As Taiwan is located in one of the most active seismic regions in the world, this supertall building may be susceptible to damage caused by strong ear t- hquakes. These features make a detailed study on the structural per f- ormance of the worlds highest tall building under earthquake excit- ations of particular importance and necessity. Numerous investigations on seismic behavior of tall buildings Have been carried out in the past; in particular shaking table tests play an im- portant role in earthquake-resistant design of structures, analysis of se- ismic responses and failure mechanisms 35. On the other hand, the finite element method (FEM) is a powerful tool for structural analysis of tall buildings. Fan and Long 6 adopted spline elements in the ana - lysis of tall buildings. In their method, the element displacements are interpolated with spline functions and accurate results cou ld be achi- eved with lowerorder functions and a few degrees of freedom. Take- batake et al. 7 presented a simplified analyt ical method for the pre- liminary design of doubly symmetric s ingle and double frame-tubes in- high-rise structures by replacing a tube with an equivale nt rod With consideration of the effect of bending, transverse shear defor- mation, shear-lag and torsion. Li et al. 8,9 proposed finite segment a- pproaches for estimating the dynamic characteristics of tall buildings. Recently, Li and Wu 10 established seven 3-D FE models for a 78-st- ory super-tall building, and numerical results of the structural dynami c characteristics were compared with their field measurements t o identify the FEM modeling errors for the purpose of updating the FEM models. Ventura and Schuster 11 presented a numerical study on estimation of dynamic characteristic of a 30 -storey RC building. A reducedorder con- tinuum model was proposed by Chajes et al. 12 to conduct dynamic analysis of a 47-storey steel-framed building and correlate the numeri- cal results with those from measured responses during an earthquake. Pan et al. 13 and Brownjohn et al. 14 presented numerical studies on dynamic responses of the tallest building in Singapore wi th correlation with their field measurements. Qi et al. 15 employed the finite elem - ent method to study the seismic performance of a tall building and their results illustrated that the building is likely to perform satisfactorily u - nder severe seismic events. Rahimian and Romer o 16 established a fi- nite element model to study the seismic response of the tallest building in Mexico City by time-history analysis and spectral method. These in- vestigations indicated that numerical simulation is an effective tool to determine the dynamic characteristics and seismic responses of tall buildings. However, literature review reveals that comprehensive re - search studies on seismic effects on a super-tall building (building height 500 m) have rarely been reported in the literature. So, a det - ailed analysis is presented in this paper to investigate the dynamic characteristics and seismic responses of the super-tall building. The objective of this study is to investigate the seismic effects on the wo- rlds tallest building in order to provide valuable information for the design and construction of other similar structures in the future. 2. The structural system of Taipei 101 Taipei 101, a 508-m high office tower, is located at the east district of downtown Taipei City, and the elevation view of the building is shown in Fig. 1. The structure is symmetrical with a 62.4 m by 62.4 m square footprint 17. Two sloping rectangular mega-columns with a maxim um cross-sectional dimension of 2400 mm 3000 mm, are pos itioned one at each side of the building extending to the 90th floor, and finally the cross-sectional dimension of the mega-column is reduced to 1600 mm2000 mm. All perimeter columns are sloping from the ground floor to 25th floor, and the sloping angle is 4.4. The core columns are square and rectangular concrete-filled steel tubes (CFT). The compressive strength of the concrete is 70 MPa, which provide extra stiffness and strength to the steel tubes, from bottom of the basement to the 62nd floor. The section of the core columns reduce from 1200 mm 1200 mm to 900 mm 900 mm, which are smaller than the mega-column. The composite metal deck-slabs built at each floor are 135 mm thick, however, those at mechanical floors are 200 mm thick. The primary girders are composed of H-steel beams with moment-resisting connections at the beam -column joints. Dog-bone connections are also provided at locations where ductility is required while beams are pinned to the primary girders, as shown in Fig. 2. Belt-trusses, one or two-stories high, are placed every 8 -story interval at the perimeter frame, and the brace core is connected to mega-columns via belt-trusses consisting of in-floor braces and vertical trusses. The locations of the belt -trusses in the 8th floor are shown in Fig. 3 17. When the space of the column is 10.5 m, the shape of the steel braces are V or reverse V, and when the space is 6 m, the shape of steel braces are acclivitous braces Fig. 4 presents an elevation view and the locations of the belt - trusses in axes M9 and P1 17. The belt-trusses and mega-columns help to stabilize the building core in the same way that the brace core helps to balance the perimeter frame. This mega-frame design maximizes the spaces inside the building and carries perimeter gravity loads at selected columns. The bracing, outriggers, and belts that link the columns would also redistribute loads if some members are damaged by unforeseen circumstances. The structure is a dual system: the external st ructure is composed of the mega columns and external columns providing the lateral rigidity to the seismic and wind loads, and the internal structure, also designated as substructures, provides the utilizable space and allows for significant amount of energy dissipation. Belt trusses composed of a transfer floor system are placed at every eighth or tenth floor, so the interior columns only carry the gravity loads from a limited number of floors. As a result, their sizes are substantially smaller than those in a conventional structural system, in which they would rise from foundation level to the building top. A FE model was established in this study based on t he design drawings of the super-tall building. The dead loads for building elements were determined by a commercial FE program ANSYS 10.0 18 and the design live loads were calculated accor ding to the data found from the design documents 17. 3. Structural analysis 3.1. Finite element modeling With rapid development i n computer technology and compu tational mechanics algor- ithms, three-dimensional finite element analysis has become a routine design tool of tall buildings. Four kinds of elements are emp- loyed in establishing the FE model of Taipei 101 structure: 3-D beam elements, suitable for nonlin ear large rotations and l arge strains, are employed to model the columns and beams. Li- nk elements are used to mo- del the brace. Mass elements are employed to model the live loads and non structural components. The fl oors are modeled with shell elements. The connection between t he structure and its foundation is treated to be fixed. 3.2. Constitutive relationships of rectangular CFT columns Concrete-filled steel tube (CFT) columns are widely used due to their good earthquake resistant behavior such as improved strength and high ductility capacity. When a short CFT column is under an axial load, as shown in Fig. 4(b), there is a basicassumption that steel and concrete have the same longitudinal strain 3, then the hoop stains of steel 1 s and concrete 1 ccan be calculated by: 1 s=s3, 1 c=c3 (1) where s,care the Poissons ratio of steel and concrete, respectively. Generally, at low stress conditi ons, concrete has a lower value of Poissons ratio than steel, which may result in occurrence of separation between the two materials in a CFT column. At high compressive stresses, internal micro-cracking in concrete causes it to swell. Its outwards movement is restrained by steel, and the strength of concrete is increased due to this lateral restraint. Thus the concrete and steel are stressed triaxially, as shown in Fig.5 (a). Zhong 19,20 proposed a unified theory to model CFT columns based on extensive expe- rimental and FE analysis results of CFT columns under axial loading. Accord ing to the theory, a CFT column is regarded as a new composite column or material instead of Sep- arate components of concrete and steel. The properties of the composite column depend on those of steel and concrete and their dimensions (e.g., tube diameter and steel wall thickness).The u- ltmate strength and other property parameters of a C FT column can then be determined based on the mechanical and geometrical properties of the composite material. The following fo- rmulas for rectangular CFT columns are ado pted in this study based on the unified theory 19,20: The yield strength of the composite column is fs c y= (1.212 + B + C2 )fck (2) where, B and C are coefficients. They depend on the cross-sectiongeometry. For a rectangular cross -section, one has: B = 0.1381(fy/235) + 0.7646, C = 0.0727(fck/20) + 0.2016,where is the confining factor which is expressed as ysck cfAfA in which fy, fck, Asand Acare the yield strength of steel, theunconfined strength of concrete and the areas of steel and concretecomponents in the column, respectively.The elastic modulusEscof the composite column can beexpressed as Esc= fs c p/s c p (3) where fs c p , s c p are the proportional stress and strain of the composite column, respectively.For a rectangular CFT column, one has fs c p = 0.192(fy/235) + 0.488fs c y (4) s c p = 0.67fy/ Es. (5) The tangent module of the composite column can be calculated as (fs c y ) (6) where = N/Asc, N is the axial load on the column and Ascis the total area of the column section. The hardening modulus of the composite column can be determined by E0 sc=400 150. (7) In this paper, the loaddeformation (stressstrain) relation of a CFT column was determined based on experimental measure - ments from CFT columns under axial compressions 19, which was simplified as a tri-linear stressstrain model including pro portional, yield and hardening stages, as shown in Fig. 6(a). The tangent module is substituted by the module of a straig ht line connected the proportional point and the yield point. According to Eqs. (2)(5) and (7), the related parameters for a CFT column can thus be determined. For structural analysis of the s teel beams and brace members in Taipei 101 building, a bilinear stressstrain curve with 2% post - yield hardening (see Fig. 6(b) was adopted to model the inelastic behavior of these structural members, with Youngs modulus of 420 MPa and Poissons ratio of 0.3, respectively. Von Mises yield criterion with kinematic hardening rule was employed in the numerical analysis. 3.3. Verification of the constitutive relationships of CFT columns For verification of the adequacy of the constitutive relationships of CFT columns and steel members discussed above as well as the selected finite element types for modeling the structural members of Taipei 101 structural system, a shaking table test and the associated FEM analys is were conducted in this study for a frame structure model composed of rectangular CFT columns and steel members by comparing the numer - ical results with the experimental data. The test model and its finite element model are shown in Fig. 7 and 8, respectively. The scaled mo- del was tested on the shaking table adopting three representative ear- thquake records as inputs: (1) An artificial seismic accelerogram (made according to the design code of China 21); (2) El-Centro ear- thquake record; and (3) Tianjin earthquake record. The peak ground accelerat- ions (PGA) in the three accelerogams were scaled to 0 :05g and 0:1g to represent the design earthquake actions with intensity 6 and 7 degree as stipulated in the design code of China 21, respectively. The design code 21 classifies regions of different seismicity in terms of seismic intensity which is usually regarded to be an equivalent of peak ground acceleration. Table 1 shows the relationship between the seis- mic int- ensity and peak ground accele ration 21. Each accelerogram du- ration was reduced to 1=5 of its original duration according to the scale factor listed in Table 2. Table 3 lists the first four natural frequencies of the model obtained from the test and the numerical analysis of the FE model. Furthermore, acceleration dynamic amplification factors of the modeling strategies presented ab ove in the establishment of the FE model of Taipei 101 structural system. 4. Dynamic characteristics of the super -tall building A three-dimensional FE model of Taipei 101 structural system was established for numerical analysis of the super -tall building, as shown in Fig. 10, based on the constitutive relationships for rectangular CFT columns and steel members as well as the selected finite element types which were verified above. The FE model of the super-tall bu- ilding contains 20 532 beam elements, 24 048 shell elements, and 3496 link elements. In addition to the main structural elements, nonstructural components were modeled with mass elements. Fig. 11 shows the first six mode shapes of the FE model including two for translational moti - ons in each horizontal direction and two for torsional motions abo - ut the vertical axis. Modes 1 and 2 are the translational modes in x and y directions, respectively. Mode 3 is the fundamental torsional mode. The fundamental periods of the building are 6.21 s. in the