Prediction of the force–drift envelope for RC columns in flexure by the CAE method

A non‐parametric empirical approach, called the conditional average estimator (CAE) method, has been applied for the prediction of the normalized lateral force–drift envelope of reinforced concrete (RC) rectangular columns, as well as their characteristic drifts (effective yield drift, capping drift and ultimate drift), and drift‐related parameters (the ratio between the effective yield drift and elastic drift, and two ductility measures). A subset of the PEER RC column database was used. Five input parameters were employed: axial load index, index related to confinement, shear span index, concrete compressive strength, and longitudinal reinforcement index. The results suggest that the relations between the input and output parameters are complex, and that it is difficult to isolate the influence of a single parameter. Nevertheless, some trends were observed. The axial load index is the most influential input parameter. All the results decrease with an increasing axial load index, whereas they increase with an increasing longitudinal reinforcement index. An increase in the index related to confinement results in increases in the ultimate drift and in ductility. The influence of the shear span index is the most complex. The influence of the concrete strength is small with the exception of two output parameters related to elastic drift, which substantially decrease with increasing strength. The dispersion of the results is relatively large. The results of the predictions can be used for mathematical modelling of moment–rotation backbone curves for plastic hinges, and for the estimation of the deformation capacity of columns in seismic performance assessments. Copyright © 2007 John Wiley & Sons, Ltd.     

碳纤维布加固技术

碳纤维布是纤维增强塑料的一种,作为新型加固材料,克服了传统加固方法的诸多不足,可用于各种结构加固,具有良好的应用前景．     

Failure mechanisms of steep-faced geosynthetic-reinforced retaining walls subjected to toe scouring

Waterfront structures such as seawalls, dikes, and levees are frequently subjected to scouring at the toe of the slope, leading to deteriorated performance and increased failure potential. To this end, some model reinforced steep-faced slopes consisting of a two-dimensional backfill were brought to failure to explore the failure mechanisms of some geosynthetic-reinforced slopes subjected to simulated toe scouring. Results of model tests indicate that in the case of shallow scouring, a reinforcement length (L) increase from 0.4 to 1.0 H_t (H_t, total height of reinforced walls) significantly increases the tolerance against toe scouring-induced failures. In this case, a local bearing capacity failure of facing is the dominant failure mode. In the case of deep scouring, an increase in L beyond 0.7 H_t provides no additional tolerance against toe scouring because the ultimate state is always associated with a global circular sliding in the unreinforced zone. Experimental values of the lateral pressure coefficient (K_t) converted from the measured reinforcement forces indicate that reinforcement forces consistently increase in response to toe scouring up to the final collapsing state and that the reinforcement forces for L?=?1.0 H_t mobilize more effectively than those for L?=?0.7 H_t.     

加筋土挡墙静载模型试验及其力学性能研究

为研究加筋土挡墙在墙顶荷载作用下土体受力和变形形态,通过改变筋材层数、筋材长度和替换加筋材料等方式对加筋土挡墙进行了4种工况的模型试验。对4种工况下的加筋土墙体内竖向土压力、墙面水平位移、墙顶竖向位移和筋材应变等进行对比研究。研究表明,挡墙上部竖向土压力增长较快且各层竖向土压力最大值由加载点下部向墙面处移动;墙顶荷载超过130 kPa时,由于不均匀沉降,第5层筋材对应墙面处有向内收缩趋势,墙面水平位移最大值大约在上三分点位置;整个加载阶段,筋材总体应变值增幅不大且远小于筋材设计应变峰值;增加挡墙内筋材层数和增加筋材长度均可提升挡墙各方面性能,但增加筋材层数提高效果要优于增加筋材长度;使用废旧轮胎代替单向格栅进行加筋可有效提高挡墙整体性能,分散超载引起的附加应力,有效减小墙面水平位移和墙顶竖向位移。     

基于BP神经网络的有限特征参数砌体结构震害等级推演

详细的建筑结构特征参数是得到合理地震易损性分析结果的基础。本文给出了一种结合已有地震易损性分析成果,在具备有限特征参数的情况下,利用BP神经网络进行单体或群体结构震害等级推演的方法。以陕西省渭南市607栋设防砌体易损性评估结果为样本构建了一个3层BP神经网络模型,并对北京市海淀区近2万栋设防砌体不同地震烈度下的可能破坏状态进行推演,结果能够反映区域本地化特征,也与抗震设计目标和震害案例相符。该方法适用于少量特征参数下单体或群体结构的快速震害等级推演,可为相似烈度地区的建筑结构风险评估提供参考。     

水位对加筋土护岸挡墙的影响分析

采用有限元方法,分析水位对加筋土护岸挡墙的影响。分析得出水位影响加筋土护岸挡墙的水平位移、土压力和加筋拉力值。