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Physical and numerical modeling of nonlinear cyclic load-deformation behavior of shallow foundations supporting rocking shear walls.

機(jī)譯：支撐搖擺剪力墻的淺層基礎(chǔ)非線性循環(huán)荷載-變形特性的物理和數(shù)值模擬。

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摘要

A shear wall supported by a shallow foundation system is a commonly used seismic-force-resisting structural building system, yet there are many unresolved issues regarding their design and performance. One of the major changes in the traditional seismic design procedures adopted in the 1997 Federal Emergency Management Agency's (FEMA) Building Retrofit NEHRP Guidelines was to allow mobilization of the ultimate capacity and rocking behavior of shallow foundations to reduce the ductility demands on structures. However, the uncertainty in soil properties, the absence of practical reliable foundation modeling techniques, and the resulting permanent settlement beneath the footing due to foundation rocking have hindered the use of nonlinear soil-foundation-structure interaction as a mechanism for reducing demands on the structure in practice.; About sixty footings, representative of footings for building shear walls, were tested in a centrifuge under cyclic vertical (V), horizontal (H), and moment (M) loading; some were tested in slow cyclic loading while others were shaken using the shaking table on the centrifuge. Footing dimensions, depth of embedment, shear wall weight, soil strength, initial static vertical factor of safety (FSV), and loading paths were systematically varied. Experimental findings suggest that footings with higher FSV are capable of dissipating energy (approximately 20% of critical damping for FS V ≈ 10) through foundation rocking without causing excessive permanent settlement. Moment capacity of the foundation does not degrade significantly with increasing cyclic rotation for the types of soils tested in the experiments.; A new "contact interface model" has been developed to provide coupled nonlinear constitutive relations between cyclic loads (V-H-M) and displacements (settlement, sliding, and rotation) of the footing-soil system. The footing and the soil beneath the footing, considered as a macro-element, were modeled with the introduction of a new parameter, critical contact length ratio (Lc/L), where Lc is the minimum length of the footing required to be in contact with the soil to satisfy equilibrium. The contact interface model is able to predict load capacities, stiffness degradation, permanent and cyclic displacements, and hysteretic energy dissipation as measured in the centrifuge experiments. The contact interface model is implemented and tested in OpenSEES finite element framework.
機(jī)譯：淺基礎(chǔ)系統(tǒng)支撐的剪力墻是一種常用的抗震結(jié)構(gòu)建筑系統(tǒng)，但在設(shè)計(jì)和性能方面仍存在許多未解決的問(wèn)題。 1997年美國(guó)聯(lián)邦緊急事務(wù)管理局（FEMA）建筑改造NEHRP指南采用的傳統(tǒng)抗震設(shè)計(jì)程序的主要變化之一是允許調(diào)動(dòng)淺層基礎(chǔ)的極限承載力和搖擺特性，以降低結(jié)構(gòu)的延性要求。但是，由于土壤特性的不確定性，缺乏實(shí)用可靠的基礎(chǔ)建模技術(shù)以及由于基礎(chǔ)搖擺而導(dǎo)致的基礎(chǔ)下永久沉降，阻礙了非線性地基-結(jié)構(gòu)相互作用作為減少對(duì)結(jié)構(gòu)要求的機(jī)制的使用。在實(shí)踐中。;在循環(huán)垂直（V），水平（H）和彎矩（M）載荷下，在離心機(jī)中測(cè)試了約60個(gè)代表建筑剪力墻的基礎(chǔ)的基礎(chǔ)。其中一些在緩慢的循環(huán)負(fù)載下進(jìn)行了測(cè)試，而另一些則使用離心機(jī)上的振動(dòng)臺(tái)進(jìn)行了振動(dòng)。系統(tǒng)地改變了基礎(chǔ)尺寸，嵌入深度，剪力墻重量，土壤強(qiáng)度，初始靜態(tài)垂直安全系數(shù)（FSV）和加載路徑。實(shí)驗(yàn)結(jié)果表明，具有較高FSV的基礎(chǔ)可以通過(guò)基礎(chǔ)搖擺消散能量（對(duì)于FS V＆ap; 10，約為臨界阻尼的20％），而不會(huì)引起過(guò)多的永久沉降。對(duì)于實(shí)驗(yàn)中測(cè)試的土壤類(lèi)型，基礎(chǔ)的動(dòng)量不會(huì)隨著循環(huán)旋轉(zhuǎn)的增加而顯著降低。已經(jīng)開(kāi)發(fā)了一種新的“接觸界面模型”，以提供循環(huán)荷載（V-H-M）與基礎(chǔ)土壤系統(tǒng)的位移（沉降，滑動(dòng)和旋轉(zhuǎn)）之間的耦合非線性本構(gòu)關(guān)系。底腳和底腳下面的土壤（被視為宏觀元素）通過(guò)引入新參數(shù)臨界接觸長(zhǎng)度比（Lc / L）建模，其中Lc是需要接觸的底腳最小長(zhǎng)度與土壤滿(mǎn)足平衡。接觸界面模型能夠預(yù)測(cè)負(fù)載能力，剛度降低，永久和周期性位移以及在離心機(jī)實(shí)驗(yàn)中測(cè)得的滯回耗能。聯(lián)系人接口模型是在OpenSEES有限元框架中實(shí)現(xiàn)和測(cè)試的。

著錄項(xiàng)

  • 作者

    Gajan, Sivapalan.;

  • 作者單位

    University of California, Davis.;

  • 授予單位 University of California, Davis.;
  • 學(xué)科 Applied Mechanics.; Engineering Civil.
  • 學(xué)位 Ph.D.
  • 年度 2006
  • 頁(yè)碼 373 p.
  • 總頁(yè)數(shù) 373
  • 原文格式 PDF
  • 正文語(yǔ)種 eng
  • 中圖分類(lèi) 應(yīng)用力學(xué);建筑科學(xué);
  • 關(guān)鍵詞

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