钢筋混凝土框架结构位移放大系数能力分析

Capacity analysis for structural displacement amplification factor of reinforced concrete frames

结构位移放大系数能力值是预测结构最大变形能力,确定结构之间最小距离,防止结构在地震作用时因相互碰撞而发生倒塌的关键设计参数。但是目前我国结构抗震规范中并没有引入结构位移放大系数的概念。考虑不同设防烈度,不同层数严格按现行抗震规范设计了17个典型RC框架结构,采用OpenSees进行有限元建模与分析,并采用结构振动台试验数据和拟静力试验数据对有限元模型进行验证。分别采用非线性静力方法和非线性动力方法,对所设计典型结构的地震反应进行了分析,得到了按现行抗震规范所设计结构的位移放大系数能力值的取值及其变化规律。分析结果表明,采用结构位移放大系数能力值,可以预测结构临界倒塌状态时的结构最大弹塑性变形。按我国现行抗震规范设计的VI、VII、VIII度RC框架结构,位移放大系数能力值的最小值分别为15、10、5,具有良好的变形能力。结构位移放大系数与结构反应修正系数的比值(Cd/R)在0.8～1.2范围内,这和NEHRP推荐条文中的取值相近,但稍微偏大。

'Capacity'value of structural displacement amplification factor( DAF) is a key factor in seismic design,since it can be used to estimate the maximum inelastic deformations developed in severe earthquakes,and to estimate the minimum building spacing to avoid the collapse due to their collision during the earthquake. DAF,however,hasn't been introduced in current Chinese seismic code. In this work,17 RC frame buildings are designed with different fortification intensities and with different floors according to current Chinese seismic Codes. These structures are further modeled and analyzed by OpenSees. By comparison with the quasi-static test data and the shaking table test data for RC frame structures,the OpenSees models are verified and validated. For these 17 RC frames,structural seismic response are analyzed by nonlinear static procedures( NSP) and nonlinear dynamic procedures( NDP),respectively,and the'capacity'values of structural displacement amplification factors as well as their variations are achieved. It is shown that by using 'capacity'values of structural displacement amplification factor,structural inelastic deformations at collapse limit state may be estimated. For RC frames designed with seismic fortification intensity VI,VII,VIII,the minimum'capacity'value of structural displacement amplification factor is 15,10 and 5,respectively,and the deformation ability of designed RC frame is good. The ratios between displacement amplification factors and response modification factors( i. e. Cd/R) range from 0. 8 to 1. 2,which are only slightly larger than the value recommended in NEHR Pprovisions.