土木專業(yè)外文翻譯--靜力彈塑性分析法在側向荷載分布方式下的評估研究

1、<p>　　EVALUATION OF LATERAL LOAD PATTERN</p><p>　　IN PUSHOVER ANALYSIS</p><p>　　Armagan KORKMAZ1, Ali SARI2</p><p>　　1Visitor Researcher, Department of Civil Engineering, Unive

2、rsity of Texas at Austin, Austin,TX78712, PH: 512-232-9216; armagan@mail.utexas.edu</p><p>　　2Ph. D. Student, Department of Civil Engineering, University of Texas at Austin, Austin, TX 78712, PH: 512-232-921

3、6; ali_sari@mail.utexas.edu</p><p><b>　　ABSTRACT</b></p><p>　　The objective of this study is to evaluate the performance of the frame structures or various load patterns and variety

4、of natural periods by performing pushover and nonlinear dynamic time history analyses. The load distributions for pushover analyses are chosen as triangular, IBC (k=2) and rectangular. Four different framed structures ar

5、e used, which are typical reinforced concrete (R\C) frame systems and have four different natural periods. Even though the nonlinear dynamic time history analys</p><p>　　Keywords: Pushover analysis, nonline

6、ar time history, load patterns, moment-resisting frame</p><p>　　INTRODUCTION</p><p>　　Only the life safety and collapse prevention in general earthquake resistant design phenomena are explicitly

7、 prevented in seismic design codes. The design is generally based on evaluating the seismic performance of structures. It is required to consider inelastic behavior while evaluating the seismic demands at low performance

8、 levels. FEMA-273 and ATC-40 use pushover analysis as nonlinear static analysis but nonlinear time history analysis has more accurate results on computing seismic demands (</p><p>　　The objective of this stu

9、dy is to evaluate the performance of the frame structures for various load patterns and variety of natural periods by performing pushover and nonlinear dynamic time history analyses. 3, 5, 8 and 15 story R\C frame struct

10、ures are used in the analyses and the load distributions for pushover analyses are chosen as triangular (IBC, k=1), IBC (k=2) and rectangular, where k is the an exponent related to the structure period to define vertic

11、al distribution factor (IBC, 2000).</p><p>　　The performance of the buildings subjected to various representative earthquake ground motions is examined. Finally, pushover and nonlinear time history analyses

12、results are compared to choose the best load distribution (pattern) for specific natural period for these types of reinforced concrete frame structures.</p><p>　　GROUND MOTION DATA</p><p>　　For

13、this study, it is considered as 50 different data used in the nonlinear dynamic time history analyses, given in the Table 1. All the data are from different site classes as A, B, C and D. The shear velocities for the sit

14、e classes A, B, C and D are Vs > 750 m/s, 360m/s to 750 m/s, 180 m/s to 360 m/s, and 180 m/s, respectively. The ground motion data are chosen from different destructive earthquakes around the world earthquake name, d

15、ate of earthquake, data source, record name, peak ground a</p><p>　　The peak ground accelerations are in the range 0.046 to 0.395g, where g is acceleration due to gravity. All ground motion data are recorde

16、d in near-field region as in maximum 20 km distance.</p><p>　　DESCRIPTION OF THE FRAME STRUCTURES</p><p>　　3, 5, 8 and 15-story R\C frame structures with typical cross-sections and steel reinfor

17、cements are shown in Figure 1. The reinforced concrete frame structures have been designed according to the rules of the Turkish Code. The structures have been considered as an important class 1 with subsoil type of Z1

18、and in seismic region 1. The dead, live and seismic loads have been taken account during design.</p><p>　　All reinforced concrete frame structures consist three-bay frame, spaced at 800 cm. The story height

19、is 300 cm. The columns are assumed as fixed on the ground. Yield strength of the steel reinforcements is 22 kN/cm2 and compressive strength of concrete is 1.6kN/cm2.</p><p>　　The first natural period of the

20、3-story frame structure is computed 0.54 s. The cross-section of all beams in this frame is rectangular-shapes with 25cm width and 50cm height. The cross-section of all columns is 30cmx30cm. The first natural period of

21、5-story frame structure is 0.72 s and the cross-section of beams is 25cm width and 50cm height similar to 3-story frame. Cross-section of columns at the first three stories is 40cmx40cm and at the last two stories, it is

22、 30cmx30cm. The eight-story </p><p>　　NONLINEAR STATIC PUSHOVER ANALYSIS OF FRAME STRUCTURES</p><p>　　For low performance levels, to estimate the demands, it is required to consider inelastic be

23、havior of the structure. Pushover analysis is used to identify the seismic hazards, selection of the performance levels and design performance objectives. In Pushover analysis, applying lateral loads in patterns that rep

24、resent approximately the relative inertial forces generated at each floor level and pushing the structure under lateral loads to displacements that are larger than the maximum displacement</p><p>　　After des

25、igning and detailing the reinforced concrete frame structures, a nonlinear pushover analysis is carried out for evaluating the structural seismic response. For this purpose the computer program Drain 2D has been used. Th

26、ree simplified loading patterns; triangular, (IBC, k=1), (IBC, k=2) and rectangular, where k is an exponent related to the structure period to define vertical distribution factor, are used in the nonlinear static pushove

27、r analysis of 3, 5, 8 and 15-story R\C frame struct</p><p>　　Load criteria are based on the distribution of inertial forces of design parameters. The simplified loading patterns as uniform distribution, tria

28、ngular distribution and IBC distribution, these loading patterns are the most common loading parameters.</p><p>　　Vertical Distribution of Seismic Forces:</p><p><b>　?。?）</b></p&g

29、t;<p><b>　　（2）</b></p><p><b>　　where:</b></p><p>　　Cvx= Vertical distribution factor</p><p>　　V = Total design lateral force or shear at the base of

30、structure</p><p>　　wi and wx = The portion of the total gravity load of the structure</p><p>　　hi and hx = The height from the base</p><p>　　k = An exponent related to the structure

31、 period</p><p>　　In addition these lateral loadings, frames are subjected live loads and dead weights. P-△ effects have been taken into the account during the pushover analyses. The lateral force is increase

32、d for 3, 5 and 8-story frames until the roof displacement reached 50 cm and 100cm for15-story frame. Beam and column elements are used to analyze the frames. The beams are assumed to be rigid in the horizontal plane. Ine

33、lastic effects are assigned to plastic hinges at member ends. Strain-hardening is neglecte</p><p>　　The results of the pushover analyses are presented in Figures 2 to 5. The pushover curves are shown for thr

34、ee distributions, and for each frame structures. The curves represent base shear-weight ratio versus story level displacements for uniform, triangular and IBC load distribution. Shear V was calculated by summing all app

35、lied lateral loads above the ground level, and the weight of the building W is the summation of the weights of all floors. Beside these, these curves represent the lost of l</p><p>　　NONLINEAR DYNAMIC TIME H

36、ISTORY ANALYSIS OF FRAME STRUCTURES</p><p>　　After performing pushover analyses, nonlinear dynamic time history analyses have been employed to the four different story frame structures. These frames are subj

37、ected live and dead weights. Also P- △ effects are under consideration as in pushover analysis. For time history analysis P-? effects have been taken into the account. Finite element procedure is employed for the modelin

38、g of the structures during the nonlinear dynamic time history analyses. Drain 2D has been used for nonlinear time hist</p><p>　　The frames are subjected to 50 earthquake ground motions, which are recorded du

39、ring Anza (Horse Cany), Parkfield, Morgan Hill, Kocaeli, Coyota Lake, N. Palm Springs, Northridge, Santa Barbara, Imperial Valley, Cape Mendocino, Kobe, Central California, Lytle Creek, Whittier Narrows, Hollister Westmo

40、reland, Landers, Livermor and Cape Mendocino earthquakes, for the nonlinear dynamic time history analyses. These data are from different site classes as A, B, C and D.</p><p>　　The selected earthquake ground

41、 motions have different frequency contents and peak ground accelerations.The ground motion data are chosen from near-field region to evaluate the response of the frame structures in this region and comparison of them wi

42、th pushover analyses results. The results of nonlinear time history analysis for 3, 5, 8 and15-story frame structures are presented in Figure 6. Pushover and nonlinear time history analyses results are compared to f

43、or specific natural period </p><p>　　CONCLUSIONS</p><p>　　After designing and detailing the reinforced concrete frame structures, a nonlinear pushover analysis and nonlinear dynamic time hist

44、ory analysis are carried out for evaluating the structural seismic response for the acceptance of load distribution for inelastic behavior. It is assumed for pushover analysis that seismic demands at the target displacem

45、ent are approximately maximum seismic demands during the earthquake.</p><p>　　According to Figures 2, 3, 4 and 5, for higher story frame structures, first yielding and shear failure of the columns is experie

46、nced at the larger story displacements and rectangular distribution always give the higher base shear-weight ratio comparing to other load distributions for the corresponding story displacement.</p><p>　　A

47、s it is presented in Figure 6, nonlinear static pushover analyses for IBC (k=2), rectangular, and triangular load distribution and nonlinear time history analyses results for the chosen ground motion data (all of them ar

48、e near-field data) are compared. Pushover curves do not match with nonlinear dynamic time history analysis results especially for higher story reinforced pushover analyses results for rectangular load distribution estim

49、ate maximum seismic demands during the given earthquakes mo</p><p>　　REFERENCES</p><p>　　1. ATC-40 (1996), “Seismic evaluation and Retrofit of Concrete Buildings”, Vol.1, Applied Technology Co

50、uncil, Redwood City, CA.</p><p>　　2. FEMA 273 (1997). “NEHRP Guidelines for the Seismic Rehabilitation of Buildings, Federal Emergency Management Agency”, Washington D.C.</p><p>　　3.

51、 IBC (2000) “International Building Code”.</p><p>　　4. Prakash, V., Powell, G., Campbell, S. (1993), DRAIN 2D User Guide V 1.10, University of California at Berkeley, CA.</p><p>　　5

52、. Li, Y.R. (1996), “Non-Linear Time History And Pushover Analyses for Seismic Design and Evaluation” PhD Thesis, University of Texas, Austin, TX.</p><p>　　6. Vision 2000 Committee (1995). Structural Eng

53、ineering Association of California, CA.</p><p>　　靜力彈塑性分析法在側向荷載分布方式下的評估研究</p><p>　　Armagan KORKMAZ1, Ali SARI2</p><p>　　1訪問學者,土木工程學院, 得克薩斯大學, 奧斯汀, TX 78712, PH: 512-232-9216; armagan

54、@mail.utexas.edu</p><p>　　2博士, 土木工程學院, 得克薩斯大學, 奧斯汀, TX 78712, PH: 512-232-9216; ali_sari@mail.utexas.edu</p><p><b>　　摘要：</b></p><p>　　這項研究的目的是通過彈塑性分析法和非線性時程分析法來評估框架結構的性能

55、或多種荷載形式及自然周期的多樣性。彈塑性分析法的荷載分布狀態(tài)有三角形、IBC（k=2），和矩形。在這個研究中四種典型的鋼筋混凝土框架結構被采用，它們分別有四種不同的自然周期。非線性時程分析法是計算地震的最好方法，但美國的FEMA-273容量震譜法和ATC-40位移系數(shù)法推薦使用靜力彈塑性分析法。這篇論文將比較分別利用靜力彈塑性分析法與非線性時程分析法分析所得到的結果。為了評估彈塑性分析法在三種不同荷載形式和四種自然周期下的結果，非線性時

56、程分析法也被執(zhí)行來對照。在不同地震下分布在全球的50個站點紀錄了地面運動情況被用來做分析，通過比較靜力彈塑性分析法和非線性時程分析法的結果來選擇這種典型框架結構在特殊自然周期下最佳的荷載分布方式。</p><p>　　關鍵詞：靜力彈塑性分析、非線性時程分析、荷載形式、抗彎矩框架</p><p><b>　　前言</b></p><p>　　一般

57、的抗震設計中僅僅只有安全和碰撞是在地震設計規(guī)范中明確要求避免的，抗震設計一般基于結構在地震中的性能表現(xiàn)。這樣在低的地震水平下就要求考慮結構的非彈性行為。FEMA-273和ATC-40采用靜力彈塑性分析法而不是非線性時程分析，因為前者在抗震計算中能得到更精確度結果。在抗震計算的目的是：（a）、在經(jīng)常發(fā)生的小震情況下避免非結構破壞；（b）、在偶爾發(fā)生的中震情況下避免結構破壞和最小限度的非結構破壞；（c）、在罕遇大震下不倒塌或產(chǎn)生嚴重破壞。結

58、構設計要明確的在這三種情況下進行。</p><p>　　這項研究的目的是通過彈塑性分析法和非線性時程分析法來評估框架結構的性能或多種荷載形式及自然周期的多樣性。3、5、8和15層的四種框架結構被用來分析，分析中荷載分布狀態(tài)選擇三角形IBC（k=1），IBC（k=2）和矩形。其中k是與結構周期相關的系數(shù)，用來定義荷載豎向因素。這四種結構用非線性程序DRAIN-2D (Prakash, V., Powell, G.,

59、 Campbell, S., 1993)來分析，并把其結果與記錄的相應數(shù)據(jù)比較。靜力彈塑性分析法和非線性時程分析法都被執(zhí)行，這兩種非線性分析方法的聯(lián)系將被研究。</p><p>　　在各種不同的地震運動下建筑物的性能將被檢查，最后比較靜力彈塑性分析法和非線性時程分析法的結果來選擇這種典型框架結構在特殊自然周期下最佳的荷載分布方式。</p><p><b>　　地表運動數(shù)據(jù)<

60、/b></p><p>　　在這個研究中，50個不同的數(shù)據(jù)被用于非線性時程分析法中，在表1中給出。所有數(shù)據(jù)來自四個A、B、C、D四個等級不同地點，它們的橫波速度分別是> 750 m/s, 360m/s至750 m/s, 180 m/s至360 m/s, ? 180 m/s。這些數(shù)據(jù)選至發(fā)生在世界不同地方的毀滅性地震，其中地震的名稱、數(shù)據(jù)源、記錄名稱、加速度峰值、有效期及過期類型都在表1中給出。<

61、/p><p>　　地表加速度峰值大約在0.046g至0.395g，其中g為重力加速度。所有地表運動數(shù)據(jù)取至距離地面最大為20km的近地范圍內。</p><p><b>　　框架結構的描述</b></p><p>　　有著典型截面和鋼筋的3、5、8和15層的鋼筋混凝土框架結構見圖1，這些鋼筋混凝土結構是按Turkish 規(guī)范設計。考慮結構所處環(huán)境為土

62、質類型Z1、地震1區(qū)，設計為等級為1級，其中恒載、活載以及地震荷載在設計中已經(jīng)被考慮。</p><p>　　所有這些鋼筋混凝土框架結構都有3跨，長8m，層高3m。柱子假定與地基固結，鋼筋的屈服強度為22 kN/cm2 ，混凝土的抗壓強度為1.6kN/cm2.</p><p>　　3層框架結構的第一周期經(jīng)計算為0.54 s ，結構中所有的框架梁截面為矩形，寬25 cm、高25cm，框架柱截面

63、尺寸為30cmx30cm。5層框架結構的第一周期經(jīng)計算為0.72 s ，框架梁截面為矩形，寬25 cm、高50cm，框架柱截面尺寸前三層為40cmx40cm，后兩層為30cmx30cm。8層和15層的框架結構的周期分別為0.90 s和1.20s ，兩者的框架梁截面為矩形，寬25 cm、高55cm。8層結構框架柱截面尺寸前五層為50cmx50cm，后三層為40cmx40cm，而15層結構框架柱截面尺寸前八層為80cmx80cm，后七層為6

64、0cmx60cm。</p><p>　　框架結構的靜力彈塑性分析法</p><p>　　對于低等級的性能，為了估計其需求，就需要考慮結構的非彈性行為。靜力彈塑性分析法可以用來識別地震的危險，并選擇性能等級以此來設計性能目標。在靜力彈塑性分析法中，以側向荷載近似代表由層間產(chǎn)生的相關慣性力并使結構在這個側向荷載作用下產(chǎn)生的位移大于地震設計中預期的位移(Li, Y.R., 1996)。這種分析

65、方法提供了剪力與位移的置換關系并指出非彈性的界限和結構側面負荷能力，而曲線斜率方面的改變表明了各有限元的屈服強度。靜力彈塑性分析法的主要目的是決定結構的荷載數(shù)量和變形能力。這些信息都能夠用于評價結構的整體性。</p><p>　　在詳細設計了鋼筋混凝土框架結構后，就用靜力彈塑性分析法評估結構的地震反應，為此電腦程序Drain 2D會被用到。有以下三種簡化荷載形式：三角形IBC（k=1），IBC（k=2）和矩形，其

66、中k是與結構周期相關的系數(shù)，用來定義荷載豎向因素。它們也會用于3、5、8和15層的鋼筋混凝土框架結構的靜力彈塑性分析。</p><p>　　荷載標準的確定時基于設計參數(shù)中的慣性力的分布。簡化的荷載布置方式如均布分布、三角形分布、IBC分布是最常見的荷載參數(shù)。</p><p><b>　　地震力的豎向分布：</b></p><p><b&g

67、t;　?。?）</b></p><p><b>　　（2）</b></p><p><b>　　式中：</b></p><p>　　Cvx為豎向分布參數(shù)</p><p>　　V為總側向力設計值，或結構底部剪力</p><p>　　wi和wx為部分結構自重</

68、p><p>　　hi和hx為結構高度（至基地算起）</p><p>　　k為與結構周期相關的參數(shù)</p><p>　　除這些側向荷載外，結構還承受恒載和活載。P-△作用在靜力彈塑性分析中同樣被考慮。側向荷載一直會增加，直到3、5和8層的框架結構樓頂位移達到50cm?，15層的框架結構樓頂位移達到100 cm?。梁柱單元用于結構分析，假定梁在水平方向是剛性的，考慮非彈性影

69、響單元是鉸接的，而應變強化被忽略。雙線性彎矩—轉角關系假定用于所用梁柱單元，由ACI 318-89建議的軸壓荷載—彎矩關系、P—M、交互關系被用于柱單元屈服表面。薄弱破碎區(qū)段的慣性矩Icr ，在分析的時候用于所有的梁柱。Icr取總慣性矩Ig的一半。</p><p>　　由靜力彈塑性分析法所得的結果見圖2-5。每個框架結構的彈塑性曲線都分均布荷載、三角形荷載以及IBC荷載三種荷載方式給出，顯示了剪重比與之相對應的層

70、間位移。基底剪力V由地面以上所有荷載相加得到，結構重力W所有樓層重量之和。除此之外，這些曲線還表示結構抗側力的損失情況和柱位移下的剪切破壞。曲線中曲率的變化表明了不同結構單元屈服情況，首先是梁屈服，接著是柱屈服和各單元的剪切破壞。隨著結構自重的增加，頂層位移增大，出現(xiàn)首次屈服和剪切破壞（見圖2-5）。在相應的結構位移（水平位移）下，矩形荷載分布比其它荷載分布形式相比會造成更高的剪重比。 </p><p>　　框架

71、結構的非線性時程分析</p><p>　　前面對框架結構進行了靜力彈塑性分析，下面用非線性時程分析法對其進行分析。這些框架結構都承受恒載和活載，同靜力彈塑性分析法一樣，P-△作用在非線性時程分析中也被考慮。在非線性時程分析中Drain 2D程序被利用，有限元程序也被用來模擬結構。在靜力彈塑性分析中所描述的模型同樣用于非線性時程分析法中，且假定質量集中在節(jié)點處。</p><p>　　結構承受

72、的50種地震情況都是在以下地震中被記錄的，這些地震是美國南加州Anza地震、美國加州Parkfield地震、美國西部Morgan Hill地震、土耳其Kocaeli地震、日本Coyota Lake地震、美國N. Palm Springs地震、美國加州Northridge地震、美國加州Santa Barbara地震、美國Imperial Valley地震、美國加州Cape Mendocino地震、日本神戶Kobe地震、美國Central

73、California地震、美國加州Lytle Creek地震、美國南加州Whittier Narrows 地震、美國Hollister Westmoreland地震、美國Livermor地震、美國加州Cape Mendocino地震。這些數(shù)據(jù)取自A、B、C、D四類地區(qū)，來用于非線性時程分析。</p><p>　　被選中的地震有著不同的頻率和地表加速度峰值，數(shù)據(jù)來自近地范圍因而可以用來評估結構的反應并與靜力彈塑性分

74、析法所得到的結果比較。3、5、8和15層框架結構的非線性時程分析的結果見圖-6。由此可以比較兩種分析方法在不同周期、不同荷載情況，即矩形、三角形和IBC(k=2)下四種框架結構的結果。</p><p><b>　　結論</b></p><p>　　在詳細設計了鋼筋混凝土框架結構后，靜力彈塑性分析法和非線性時程分析法被執(zhí)行來評價在不同荷載情況下的地震反應。靜力彈塑性分析

75、法假定抗震所設的目標位移量與實際地震下的最大位移大致一樣。</p><p>　　從圖-2至圖-5可以看出，對于高層的框架結構位移增大，出現(xiàn)首次屈服和剪切破壞。在相應的結構位移（水平位移）下，矩形荷載分布比其它荷載分布形式相比會造成更高的剪重比。 </p><p>　　如圖-6所示，在所選的地表運動數(shù)據(jù)下，非線性時程分析法在三角形荷載、矩形荷載和IBC(k=2)荷載情況的結果相互比較知：靜力

76、彈塑性曲線在高層框架結構（8和15層框架結構）下與非線性時程分析得出的結構不是很相符。靜力彈塑性分析法在矩形分布下所得的抗震要求要比其它荷載方式如三角形荷載、IBC(k=2)荷載形式下更合理。</p><p><b>　　參考文獻</b></p><p>　　1. ATC-40 (1996), “Seismic evaluation and Retrofit of

77、Concrete Buildings”, Vol.1, Applied Technology Council, Redwood City, CA.</p><p>　　2. FEMA-273 (1997),“NEHRP Guidelines for the Seismic Rehabilitation of Buildings, federal Emergency Management Agency”, Was

78、hington D.C.</p><p>　　3. IBC (2000) “International Building Code”.</p><p>　　4. Prakash, V., Powell,G., Campbell, S. (1993), DRAIN 2D User Guide V 1.10, University of California at Berkeley, CA

79、.</p><p>　　5. Li, Y.R. (1996), “Non-Linear Time History And Pushover Analyses for Seismic Design and Evaluation” PhD Thesis, University of Texas, Austin, TX.</p><p>　　6. Vision 2000 Committee