brb防屈曲支撐相關(guān)論文seismic response of a 40-storey buckling-restrained braced_W

1、THE STRUCTURAL DESIGN OF TALL AND SPECIAL BUILDINGSStruct. Design Tall Spec. Build. 22, 291299 (2013)Published online 6 December 2010 in Wiley Online Library (). DOI: 10.1002/tal.687Seismic response of a 40-storey buckling-restrained braced frame designed for the Los Angeles re

2、gionPierson Jones*, and Farzin ZareianDepartment. of Civil and Environmental Engineering, University of California, Irvine, California, USASUMMARYThis study utilized nonlinear response history analysis to compare the seismic demand on three variations of a 40-storey buckling-restrained braced frame

3、designed for high seismic hazard in the Los Angeles region. The three designs were referred to as a code-based design, based on the 2006 International Building Code, a performance-based design, based on criteria published by the Los Angeles Tall Building Design Council (LATBSDC) and a performance-ba

4、sed design plus, based on newly developed criteria from The Pacific Earthquake Engineering Research Center (PEER). The response history analysis utilized spectrum-matched ground motions as well as simulated ground motions for the Puente Hills fault. The spectrum-matched motions were selected from th

5、e Next Generation Attenuation of Ground Motions (NGA) database, which is largely composed of recorded motions and scaled to five hazard levels. The simulated ground motions were broadband signals generated from a moment magnitude (Mw) 7.15 scenario rupture of the Puente Hills fault for two near faul

6、t regions and exhibit long period energy content that significantly exceeds the uniform hazard spectrum. Structural performance was assessed in terms of exceedance of a safe inter-storey drift ratio (IDR). It was seen that the simulated ground motions impose higher IDR demands on the struc- tures th

7、an the spectrum-matched NGA ground motions. Furthermore, the number of instances of exceed- ance of a safe IDR, considered for this study as IDR = 0.03, is substantially higher for the simulated ground motions, pointing to the importance of considering such motions in the collapse prevention of tall

8、 buildings on a site-specific basis. Copyright 2010 John Wiley & Sons, Ltd.Received 16 September 2010; Accepted 5 October 2010KEY WORDS: performance-based design; tall buildings; simulated ground motions; buckling restrained braced frame1. STRUCTURES USED IN STUDYStructural design of the 40-storey b

9、uckling-restrained braced frame (BRBF) buildings was performed by Simpson, Gumpertz, & Heger, Inc. (Dutta and Hamburger, 2009; Moehle et al., 2009) for three design alternatives as shown in Figure 1: a code-based design (denoted as BRBF40-CBD), a perform- ance-based design (denoted as BRBF40-PBD) an

10、d a performance-based design plus (denoted as BRBF40-PBD+). The lateral load resisting frames in each structure vary in member sizing and bracing configuration in order to satisfy the differing design criteria. The three structures share identical footprints and height (227 ft by 220 ft and 40 stori

11、es, respectively). As well, their floor systems are identical, composed of lightweight concrete fill on metal deck supported by composite steelconcrete framing. Wind and seismic forces were considered and the structural elements were designed for the most severe requirements. The code-based design w

12、as based on the 2006 International Building Code (International Code Council, 2006) with an allowance to exceed the maximum height limit. The performance-based design was based on design criteria published by the Los Angeles Tall Building Design Council (LATBSDC, 2008) and the performance-based desi

13、gn plus implemented seismic design criteria developed by the Pacific Earthquake Engineering Research Center (PEER).* Correspondence to: Pierson Jones, University of CaliforniaIrvine, Department of Civil and Environmental Engineering, E4130 Engineering Gateway, Irvine, CA 92697-2175, USA. E-mail: pjo

14、Copyright 2010 John Wiley & Sons, Ltd.292P. JONES AND F. ZAREIAN(a)(b)(c)Figure 1. Three-dimensional view of the three variations on the 40-storey BRBF structures:(a) BRBF-40-CBD, code-based design; (b) BRBF-40-PBD, performance-based design;(c) BRBF-40-PBD+, performance-based design plus.

15、The structures have four subterranean levels and 40 stories above grade.The designs differed because of the disparity in the seismic design requirements. For the code-based design, linear response spectrum analysis was used to calculate seismic forces and displacements per ASCE Standard 7-05 (Americ

16、an Society of Civil Engineers, 2005) using forces scaled to 85% of the base shear obtained from the equivalent lateral force procedure with SDS = 1.145, SD1 = 0.52 and R =7. For the performance-based design, because of less stringent design criteria in LATBSDC code compared to the 2006 International

17、 Building Code (IBC), the number and size of BRBFs was reduced. In LATBSDC, it is required that for the frequent events (25-year return period), the building remain at service level for which building components remain elastic with minor yielding in BRBF compo- nents and drift limit of 0.5%, while i

18、n extreme events, at the level of maximum credible earthquake (MCE), the building can withstand collapse (drift limit of 3%). For the performance-based plus design, the serviceability earthquake is considered as the one with a 43-year return period compared with the LATBSDC design criteria and it is

19、 required that the demand to capacity ratio does not exceed 1.5, which has forced the designers to use outriggers in the structural system. Additional information on the design of the structures can be found in Simpson, Gumpertz, & Heger, Inc. (2009).2. STRUCTURAL ANALYSIS MODELSFor design and asses

20、sment purposes, the three structures were modelled and analyzed in Perform 3D (Computers and Structures, Inc., 2008). For computational efficiency, the models used in the time history analysis only included the BRBF lateral load resisting system. Models that including the lateral strength and stiffn

21、ess contribution of the gravity load carrying system were developed, but it was realized that due to the relatively stiff nature of the BRBF, inclusion of the secondary system severely increased the computational power required to analyze the structure while the results did not practi- cally differ

22、for the maximum inter-storey drift ratios (maxIDR) or the peak floor accelerations. The first four modal periods are shown for the 40-storey BRBF structures in Table 1.The columns and beams were modelled with elastic elements. Elastic behaviour was verified in these elements by monitoring their dema

23、ndcapacity ratios and ensuring that they remained in the elastic range. The columns were modelled as non-prismatic steel sections with their moment of inertia adjusted to account for the additional stiffening due to the presence of the infill concrete. The beams were modelled similarly but with W se

24、ctions. The diaphragms were modelled as rigid and the same mass properties were assigned to each floor down to the foundation. The perimeter shear walls were modelled with elastic wall elements with 50% of the gross stiffness and 40% of elastic shear modulus to account for cracked section properties

25、.Copyright 2010 John Wiley & Sons, Ltd.Struct. Design Tall Spec. Build. 22, 291299 (2013)DOI: 10.1002/talSEISMIC RESPONSE OF 40-STOREY BRBF293Table 1. Periods, mode numbers and direction of mode shape for the structural models.Mode numberStructure name1234BRBF40-CBDperiod (s)5.2523.8023.741.476direc

26、tion h2 h1tors. h2BRBF40-PBDperiod (s)6.474.9934.491.774BRBF40-PBD+direction period (s) h2 5.736tors. 4.387 h1 4.166 h2 1.639direction h2tors. h1 h2The h1 and h2 designations correspond to the 3-D views of results shown in Figures 3 through 5.Figure 2. Backbone curve for the BRBF element used in Per

27、form 3D. Image source: Simpson, Gumpertz, & Heger, Inc. (2009).The buckling-restrained braces were modelled using a built-in component model in Perform 3D. Of the length of the buckling-restrained braces, 30% were considered as End Zone. Figure 2 shows the backbone curve of the buckling restrain-bra

28、ces which were developed assuming Ry = 1.1, w =1.25 and b = 1.1. The strain in the cores of the buckling-restrained braces are monitored to ensured that the strain does not exceed 0.013 (10ey), which is an assumption employed by the design team at Simpson, Gumpertz, & Heger, Inc. based on test resul

29、ts conducted at the University of Utah by Romero and Reavely. Details of the modelling procedures can be found in Simpson, Gumpertz, & Heger, Inc. (2009) and Dutta and Hamburger (2010).3. GROUND MOTIONS USED IN STUDYTwo batches of ground motions were applied in the study. The first batch was selecte

30、d and scaled from the Next Generation Attenuation of Ground Motions (NGA) database using spectral matching criteria for five hazard levels considering a site in the Los Angeles basin near the Puente Hills Fault and was primarily made up of recorded ground motions. The second batch, specifically chos

31、en for long-period energy content (Naeim and Graves, 2005), was made up entirely of simulated ground motions for two sites in the LA region for a Mw = 7.15 scenario rupture of the Puente Hills fault.The spectrum-matched ground motions were composed of five sets, with each set considering a target ha

32、zard level and made up of 15 pairs of orthogonal horizontal components. The hazard levels were specified with return periods of 4975, 2475, 475, 43 and 25 years (denoted as OVE, MCE, DBE, SLE43 and SLE25, respectively). The four smaller return period ground motion sets are composed entirely of recor

33、ded ground motions. The OVE set, with the longest return period, was composed of eight recorded ground motions from the NGA and seven simulated motions. The seven simulatedCopyright 2010 John Wiley & Sons, Ltd.Struct. Design Tall Spec. Build. 22, 291299 (2013)DOI: 10.1002/tal294P. JONES AND F. ZAREI

34、ANOVE motions were from a moderate rupture scenario Mw = 7.15 rupture of the Puente Hills fault (Graves and Somerville, 2006) and were also matched to the target spectrum. They were employed in the OVE set due to the scarcity of recorded ground motions for extreme near fault seismic events. Addition

35、al information on the selection and modification of the ground motions can be obtained from Moehle et al. (2009), ch. 2.Graves and Somerville (2006) simulated ground motions for the Puente Hills fault by using a hybrid of deterministic and stochastic techniques. The ground motions are broadband sign

36、als with frequencies between 0 and 10 hz (f = 0.010.0 hz). For low-frequency waves (f 1.0 hz), stochastic methods were used. Three fault rupture scenarios were simulated with varying rupture models. It should be noted that other scenarios are possible and that the location of fault rupture and direc

37、tion of rupture propagation cannot be predicted. That being said, recordings of large magnitude, near fault ground motions are rare and valid simula- tions of such motions provide useful insight into possible effects on tall structures.Two additional sets of simulated ground motions used in this stu

38、dy were extracted from the largest of the three Puente Hills simulations. They were composed of two sets, with each set corresponding to a near fault region and made up of nine pairs of orthogonal horizontal components. These motions exhibited strong directivity effects with pulse-like characteristi

39、cs and were chosen for their extreme long-period energy content (Naeim and Graves, 2005). The long-period energy in these simulated motions is the direct result of the fault rupture model, a buried rupture event with short rise time and large rupture area. The first set, called WHT, was from the hig

40、h slip region of the rupture where the largest peak ground velocities were observed. The second set, called LAD, was taken from a low slip region of the fault rupture. The response spectrum of the LAD and WHT motions significantly exceed the 4975-year target spectrum. Because of the long-period ener

41、gy these ground motions possess, the demands they impose on tall structures reside at the extreme end of demands to which tall structures at the site would be subjected.In terms of seismic hazard, a direct comparison between the spectrum-matched ground motions and the simulated ground motions is dif

42、ficult to make. Firstly, the spectrum-matched ground motions are based on a uniform hazard spectrum (UHS) and attempt to account for all earthquake sources at all distances for a single site, while the simulated motions are based on a single earthquake scenario and consider two near fault sites (Lew

43、, 2009). It is important to note that the most devastating ground motions, those belonging to the WHT set, can be attributed to a very small region of peak ground velocity while the LAD set was derived from a region of peak ground velocity characteristic of a much larger area. In short, the likely s

44、patial distribution of these two types of ground motions should be kept in perspective. Second, the uncertainty in the location and direction of fault rupture point to the need to consider other rupture scenarios to effectively quantify the seismic hazard at the site using simulated ground motions.

45、Finally, knowledge of the recurrence interval of simulated events may not be particularly precise. For example, a Mw = 7.0 multi-segment rupture of the Puente Hills fault system, the return period was estimated to range from 500 to 2000 years (Shaw and Shearer, 1999). More recently, an investigation

46、 utilizing paleoseismology revealed at least four large events (7.2 Mw 7.5) have occurred on the fault during the past 11 000 years (Dolan et al., 2003), suggesting a return period of 2750 years. Certainly, a more rigorous mathematical comparison of the hazard could be made, but the authors believe

47、that the qualitative comparison given is sufficient for the purpose of this paper.4. RESULTS OF RESPONSE HISTORY ANALYSISThe results of the response history analysis are plotted in Figures 35 for the three structures studied. Each plot shows the maximum IDR plotted against the storey number of the s

48、tructure for a given direction of the structure (BRBF40 structures) or for a given ground motion component (U6 and U20 structures). In each figure, the five sets of spectrum-scaled ground motions are plotted above the twoCopyright 2010 John Wiley & Sons, Ltd.Struct. Design Tall Spec. Build. 22, 2912

49、99 (2013)DOI: 10.1002/talSEISMIC RESPONSE OF 40-STOREY BRBF295Figure 3. Results for the 40-storey BRBF code-based design. Maximum inter-storey drift ratio (IDR) is plotted against storey number. For the spectral-matched ground motions, the ground motions set in the left column descend from the 4975-

50、year hazard level (OVE) to the 25-year hazard level (SLE25). In the h2 direction, from floors 110, there is a stiff region where the IDR are relatively small because of the presence of additional bays (compared with the PBD structure).Copyright 2010 John Wiley & Sons, Ltd.Struct. Design Tall Spec. B

51、uild. 22, 291299 (2013)DOI: 10.1002/tal296P. JONES AND F. ZAREIANFigure 4. Results for the 40-storey BRBF performance-based design. Maximum inter-storey drift (IDR) is plotted against storey number. For the spectral-matched ground motions, the ground motions set in the left column descend from the 4

52、975-year hazard level (OVE) to the 25-year hazard level (SLE25). Compared with the CBD and PBD+ structures, which have additional bays in the h2 direction, the IDR is more uniformly distributed throughout the buildings height.Copyright 2010 John Wiley & Sons, Ltd.Struct. Design Tall Spec. Build. 22,

53、 291299 (2013)DOI: 10.1002/talSEISMIC RESPONSE OF 40-STOREY BRBF297Figure 5. Results for the 40-storey BRBF performance plus-based design. Maximum inter-storey drift (IDR) is plotted against storey number. For the spectral-matched ground motions, the ground motions set in the left column descend fro

54、m the 4975-year hazard level (OVE) to the 25-year hazard level (SLE25). In the h2 direction, three bands can be seen where the maximum IDR are pulled back to smaller values due additional stiffness gained from the presence of the hat truss.Copyright 2010 John Wiley & Sons, Ltd.Struct. Design Tall Sp

55、ec. Build. 22, 291299 (2013)DOI: 10.1002/tal298P. JONES AND F. ZAREIANFigure 6. Plot of percent exceedance of safe maximum inter-storey drift ratio (IDR = 0.03) for the three buckling-restrained braced frame (BRBF) structures. The results of the analysis are plotted in terms of percentage of structu

56、res exceeding the safe IDR (ordinate). Box plots are grouped by ground motions sets (abscissa). Where no box plot is shown, there were zero instances of exceedance of the safe IDR. The simulated ground motions are shown on the left, and the spectrally matched ground motions are on the right. The per

57、formance-based design plus (BRBF40-PBD+) performed the best under the spectrally matched ground motions for which it didnot exceed the safe IDR. However, for the simulated motions, the structure was the worst performer.The code-based design (BRBF40-CBD) generally performed as well as or better than the performance-based design (BRBF40-PBD) under all ground motion sets.sets of simulated motions. The spectrum-scaled ground motions that are li