四層鋼筋混凝土框架結(jié)構(gòu)的地震反應(yīng)對砌體填充的影響—一種確定性的評估

1、四層鋼筋混凝土框架結(jié)構(gòu)的地震反應(yīng)對砌體填充的影響一種確定性的評估摘要：四層樓高的鋼筋混凝土框架結(jié)構(gòu)的地震響應(yīng)對砌體填充物的影響研究使用n2的方法。方法是基于塑性分析方法和無彈性譜方法。這是最新擴展，使其適用于填充鋼筋混凝土框架結(jié)構(gòu)。文件中總結(jié)了該方法并將其應(yīng)用于四層鋼筋混凝土框架結(jié)構(gòu)砌體填充物，并沒有他們的確定性地震評估。已經(jīng)對裸露的框架的性能作出了比較。最常見的分析建模技術(shù)，是采用壓縮對角支柱砌體填充的建模，和一個組件集中的可塑性元素建模的梁、柱的抗彎性能被應(yīng)用。分析結(jié)果表明，填充物可以徹底改變整個結(jié)構(gòu)的損害分布。填充物對結(jié)構(gòu)響應(yīng)產(chǎn)生有利的影響，把他們放置于整個結(jié)構(gòu)，并不會導(dǎo)致剪切失效。關(guān)鍵

2、詞：地震評估；鋼筋混凝土框架；砌體加密；加密鋼筋混凝土框架；簡化非線性分析引言鋼筋混凝土 (rc) 框架砌體在世界許多地區(qū)是常用的結(jié)構(gòu)體系。如果填充物適當(dāng)分布在整個結(jié)構(gòu)和適當(dāng)考慮在設(shè)計中，他們通常對結(jié)構(gòu)的地震反應(yīng)有一個有益的影響。另一方面，在計劃中負(fù)面影響可能造成的不規(guī)則的定位填充，特別是在豎向。薄弱樓層崩潰是典型的填充結(jié)構(gòu)中填充物的缺失，例如底部層。然而，第一層機制和隨后的崩潰也會發(fā)現(xiàn)在鋼筋混凝土框架結(jié)構(gòu)建筑物的情況下與常規(guī)砌體填充物的分布，如果整體延展性的裸露框架和局部塑性的結(jié)構(gòu)要素很低，如果砌體填充物是脆弱和易碎的，如果地面運動是比較強的設(shè)計強度。在強烈地震中任何方法的分析或設(shè)計的填充墻

3、框架應(yīng)該適當(dāng)考慮到高度非線性變形。一個好的關(guān)于填充墻框架的設(shè)計規(guī)定已經(jīng)被提出。一個全面的概述了建模技術(shù)分析的框架填充墻結(jié)構(gòu)準(zhǔn)備好了。廣泛的用于新型填充面板，單個或多個壓縮等效斜壓桿。在本文中討論了四層鋼筋混凝土框架結(jié)構(gòu)的地震反應(yīng)對砌體填充的影響。最近由作者提出的一個簡化的抗震性能評估放法，已經(jīng)被使用。在一個變形，不開口填充（“完全填充墻框架”，第3.1節(jié)），而在其他變形有開口門窗填充（“部分填充墻框架”，3.1節(jié)）。比較了裸露的變形框架。部分填充墻框架和裸露的框架在埃爾莎實驗室進行全面的pseudo-dynamically測試。在分析中，砌體填充板被參照兩個對角線的支撐，只可進行壓縮的方式。“

4、抗彎性能的梁、柱模型的單組分集中塑性元件，組成一個彈性梁和兩根彈性轉(zhuǎn)動鉸鏈（定義為一個彎矩-轉(zhuǎn)角關(guān)系）。數(shù)學(xué)模型的計算結(jié)果與實驗結(jié)果進行比較,驗證了非線性動態(tài)分析。該opensees計劃是用于所有的分析。地震評估討論，在本文中的應(yīng)用是確定性的。在文獻(xiàn)提出了一種概率評估。1. n2的方法綜述盧布爾雅那大學(xué)和歐洲規(guī)范8(ec8)已經(jīng)實施的n2方法，最近已擴展到填充墻框架。本文簡要總結(jié)了框架平面的建筑結(jié)構(gòu)和其擴展名的基本途徑。n2方法結(jié)合靜力彈塑性分析的多自由度（多自由度）模型與反應(yīng)譜分析的一種等效單自由度（單自由度）模型。荷載橫向分布向量，采用彈塑性分析，是有關(guān)假定的位移向量(n = 1,n表示屋

5、頂高度) 其中m是對角質(zhì)量矩陣。這里沒有固定位移形狀的選擇規(guī)則。規(guī)范性文件可給予一些指導(dǎo)。基底剪力位移關(guān)系得到了彈塑性分析是理想化的，通常是由一個雙線性（彈塑性）理想化。以這種方式得到力fy和位移dy是果斷的，該轉(zhuǎn)化為等效單自由度模型是由除以基底剪力和頂層位移的多自由度模型的一個轉(zhuǎn)換因子，定義為其中1是單位向量,m是有效質(zhì)量。理想化系統(tǒng)的彈性階段被定義為容量曲線,可以在加速度-位移(ad)格式中繪制和直觀地與需求譜中相同的格式繪制相比，確定從理想化的力量變形曲線的等效單自由度體系中除以m。他們之間的關(guān)系（光譜）加速度和屈服應(yīng)力fy的多自由度系統(tǒng)可以定義為折減系數(shù)r由于耗能能力的定義是加速度的比

6、值方面的需求彈性sae為周期t、光譜加速度、加速度能力上指出(即光譜加速度對應(yīng)于屈服，式(3)注意折減系數(shù)用于抗震規(guī)范(例如變形因素q在歐洲規(guī)范8中使用)也考慮減少到極限，因此并不能等同于折減系數(shù)r的定義式（5）。折減系數(shù)r、延展性的和周期t（rt 關(guān)系）之間的關(guān)系取決于類型的結(jié)構(gòu)體系，并且提供在文獻(xiàn)中。最簡單的關(guān)系是平等的位移規(guī)則，通常用于普通結(jié)構(gòu)與時間的中期和長期范圍。為了用n2方法填充鋼筋混凝土框架結(jié)構(gòu)，在ec8中兩種改進需要做出最基本的（簡單）版本的實行方法。首先，推覆曲線已經(jīng)被理想化為線性力位移關(guān)系而不是一個簡單的彈塑性。一個典型的理想化的力位移曲線包絡(luò)對應(yīng)一個填充墻鋼筋混凝土框架如

7、圖1所示。它可以分為四部分。第一，等效彈性部分代表的初始彈性變形和變形開裂后發(fā)生在框架和填充兩處。第二部分，點p1和p2之間表示屈服。由于低延性框架填充墻，這部分通常是短暫的。第三部分，這是一個重要的特點，填充墻結(jié)構(gòu)，強度退化治理的結(jié)構(gòu)相應(yīng)直到達(dá)到p3，其填充徹底失敗。在這一點后，只有抵抗水平荷載的框架。其次，有彈性的光譜由減少使用特定的因素(即r-t關(guān)系)適合填充墻框架，例如那些建議在。結(jié)構(gòu)參數(shù)確定的折減系數(shù)，這是除了采用參數(shù)中使用的常規(guī)，例如：彈塑性系統(tǒng)（即初期和整體延展性），延性之初,強度退化s = d2 / d1(圖1),以及填充失敗后強度減少ru= f3/f1（圖1）。折減系數(shù)還取決

8、于角的彈性需求反應(yīng)譜（tc和td根據(jù)ec8）。為了進行說明，表示填充墻的框架，根據(jù)確定特定理想化系統(tǒng)rt關(guān)系呈現(xiàn)于圖2。兩個情節(jié)，一個用于給定的延展性，另一個為提供給定的折減系數(shù)（強度）。作為比較，也會顯示無強度退化彈塑性系統(tǒng)關(guān)系。the effect of masonry infills on the seismic response of a four-storey reinforced concrete framea deterministic assessmentmatjaz dolsek_, peter fajfaruniversity of ljubljana, faculty o

9、f civil and geodetic engineering, jamova 2, si-1000 ljubljana, sloveniareceived 11 may 2007; received in revised form 28 december 2007; accepted 7 january 2008available online 14 february 2008abstractthe effect of masonry infills on the seismic response of a four-storey reinforced concrete frame has

10、 been studied using the n2 method. the method is based on pushover analysis and the inelastic spectrum approach. it was recently extended in order to make it applicable to infilled reinforced concrete frames. in the paper the method is summarized and applied to the deterministic seismic assessment o

11、f a four-storey reinforced concrete frame with masonry infills, with openings and without them. a comparison has been made with the behaviour of the bare frame. the most common analytical modelling technique, which employs compressive diagonal struts for modelling of the masonry infill, and one-comp

12、onent lumped plasticity elements for modelling the flexural behaviour of the beams and columns, was applied. the results of the analyses indicate that the infills can completely change the distribution of damage throughout the structure. the infills can have a beneficial effect on the structural res

13、ponse, provided that they are placed regularly throughout the structure, and that they do not cause shear failures of columns.c 2008 elsevier ltd. all rights reserved.keywords: seismic assessment; reinforced concrete frame; masonry infill; infilled rc frame; simplified nonlinear analysis1. introduct

14、ionreinforced concrete (rc) frames with masonry infill are a popular structural system in many parts of the world 1. if the infills are properly distributed throughout the structure and properly considered in the design, then they usually have a beneficial effect on the seismic response of the struc

15、ture.on the other hand, negative effects can be caused by irregular positioning of the infills in plan, and especially in elevation 1, 2. a soft-storey collapse is typical for infilled structures in which the infills are missing in one, e.g. the bottom storey. however, a first-storey mechanism and s

16、ubsequent collapse can also occur in the case of rc frame buildings with a regular distribution of masonry infills if the global ductility of the bare frame and the local ductilities of the structural elements are low, if the masonry infills are weak and brittle, and if the ground motion is strong c

17、ompared to the design strength 3. any method for the analysis or design of infilled frames should properly take into account the highly nonlinear behaviour of this system during strong earthquakes. a good review of design provisions related to infilled frames has been presented by kaushik et al. 4.

18、a comprehensive overview of the analytical modelling techniques of infilled frame structures was prepared, for example, by moghaddam and dowling 5 and, more recently, by crisafulli, carr and park 6. the mostcommonly used technique to model infill panels is that of single or multiple compressive equi

19、valent diagonal struts. in this paper the effects of masonry infill on the seismic response of a four-storey reinforced concrete frame are discussed. a simplified seismic performance assessment method, recently proposed by the authors 7, has been used. in one variant, the infill is without openings

20、(the “fully infilledframe”, section 3.1), whereas in the other variant there are openings for windows and doors in infills (the “partially infilled frame”, section 3.1). a comparison has been made with the behaviour of the bare frame. the partially infilled frame and the bare frame were pseudo-dynam

21、ically tested at full-scale in the elsa laboratory in ispra 8. in the analyses, the masonry infill panels were modelled by means of two diagonal struts, which can only carry compression. the flexural behaviour of the beams and columns was modeled by one-component lumped plasticity elements, consisti

22、ng of an elastic beam and two inelastic rotational hinges (defined by a momentrotation relationship). the mathematical model was validated by comparing the results of nonlinear dynamic analyses with the experimental results. the opensees program was used for all the analyses 9. the seismic assessmen

23、t discussed and applied in this paper is deterministic. in the companion paper 10 a probabilistic assessment is presented.2. summary of the n2 methodthe n2 method 11, which was developed at the university of ljubljana and has been implemented in eurocode 8 (ec8) 12, has been recently extended to inf

24、illed frames 13,7. in this paper, the basic approach for planar building structures and its extension to infilled frames are briefly summarized. the n2 method combines pushover analysis of a multidegree- of-freedom (mdof) model with the response spectrum analysis of an equivalent single-degree-of-fr

25、eedom (sdof) model. the lateral load distribution vector , employed in pushover analysis, is related to the assumed displacement shape vector _ (_n = 1, n denotes the roof level) bywhere m is the diagonal mass matrix. there are no fixed rules for the choice of the displacement shape. some guidelines

26、 may be given in the regulatory documents. the base sheartop displacement relationship obtained by pushover analysis has to be idealized, usually by a bilinear (elasto-plastic) idealization. in this way the yield force fy , and the yield displacement dy , are determined. the transformation to an equ

27、ivalent sdof model is made by dividing the base shear and top displacementof the mdof model with a transformation factor which is defined as where 1 is the unity vector and m_ is the effective mass. the elastic period of the idealized system is defined as the capacity curve, which can be plotted in

28、the acceleration displacement (ad) format and visually compared with demand spectra plotted in the same format, is determined from the idealized forcedeformation curve of the equivalent sdof system by dividing the force by m_. the relation between the (spectral) acceleration and the yield force fy o

29、f the mdof system is thus defined as the reduction factor r due to energy dissipation capacity is defined as the ratio of the acceleration demand sae in terms of the elastic spectral acceleration for the period t , to the acceleration capacity say (i.e. spectral acceleration corresponding to the yie

30、ld force, eq. (3) note that the reduction factors used in seismic codes (e.g. the behaviour factor q used in eurocode 8) take into account also the reduction due to overstrength, and are thus not equivalent to the reduction factor r defined in eq. (5). the relationships between the reduction factor

31、r, the ductility , and the period t (the rt relations) depend on the type of structural system, and are provided in the literature. the simplest relation is the “equal displacement rule”, which is often used for ordinarystructures with periods in the medium- and long-period range.in order to apply t

32、he n2 method to infilled rc frames, two modifications need to be made to the basic (simple) versionof the method implemented in ec 8. firstly, the pushover curve has to be idealized as a multi-linear forcedisplacement relation rather than a simple elasto-plastic one. a typicalidealized forcedisplace

33、ment envelope corresponding to an infilled rc frame is shown in fig. 1. it can be divided into four parts. the first, equivalent elastic part represents both the initial elastic behaviour and the behaviour after cracking has occurred in both the frame and the infill. the second part, between points p1 and p2, represents yielding. this part is typically short, due to the low ductility of infilledframes. in the third part, which is an important characteristic of infilled structures, strength degradation of the infill governs the structural response until t