再生混凝土框架顶层角节点的抗震性能试验研究

通过对3榀再生混凝土框架顶层角节点(再生粗骨料掺量为100%)在低周反复荷载作用下的抗震性能试验,对试件的破坏形态、延性、耗能能力等进行了分析。研究表明,再生混凝土框架顶层角节点试件在低周反复荷载作用下经历初裂、通裂、极限、破坏4个阶段,最终呈节点核心区剪切破坏。位移延性系数在3.27～3.95之间,具有良好的抗震性能,可用于有抗震设防要求的框架。采用ANSYS软件建立了节点的有限元计算模型,进行了单调荷载下的有限元非线性分析,得到了骨架曲线和试件的应力分布形态,有限元计算结果与试验结果吻合较好。采用《混凝土结构设计规范》规定的公式对角节点抗剪强度进行了计算并与试验数据相比较,发现计算值偏于不安全。     

高强混凝土剪力墙地震损伤模型分析

在分析比较现有钢筋混凝土结构的地震损伤模型的基础上,根据高强混凝土剪力墙的滞回曲线特性及刚度退化规律,采用能量耗散系数和最大变位处的卸载刚度的退化为破坏参数,提出了适用于高强混凝土剪力墙构件的双参数地震损伤模型。依据已有的高强混凝土剪力墙构件试验研究结果,对损伤模型进行非线性回归分析,确定了相应的地震损伤模型参数,提出了高强混凝土剪力墙各性能水平的损伤指数以及相应于三水准抗震设防的损伤指数允许值。分析结果表明,按本文所提出的损伤模型计算得到的剪力墙构件最终破坏时对应的损伤指数,其平均值在合理范围内,标准差较小;损伤指数计算值对应的损伤程度基本符合试验结果,计算结果离散程度较低。     

保定市典型多层砖混结构震害预测分析

将保定市42栋典型多层砖混结构分别按照年代、用途、层数分类,采用结构易损性方法进行震害预测分析,得出各自震害矩阵,并以平均抗震能力指数评价其抗震能力。分析结论可为保定市多层砖混群体震害预测提供参考。     

Numerically based proposals for the stiffness and strength of masonry infills with openings in reinforced concrete frames

Aimed at investigating the effect of openings on the in‐plane behaviour of masonry infills in reinforced concrete frames, a parametric study is presented based on model calibration via experimental tests. Two types of openings are investigated: central window openings and different combinations of door and window openings based on the typologies of southern European countries. First, a finite element model of the structure is made using the DIANA software program. Then, after calibration with experimental results, a parametric analysis is carried out to investigate the effect of the presence and location of the different types of openings on the in‐plane behaviour of the infilled frame. Finally, different equations for predicting the initial stiffness and lateral strength of infilled frames with any types of openings were obtained. An α factor related to the geometry of the piers between openings is proposed to take into account the location of the openings in the developed equations. Subsequently, the masonry infill panel is replaced by a diagonal strut. An empirical equation is also proposed for the width of an equivalent strut to replace a masonry infill panel with openings in such a way that they possess the same initial stiffness. Copyright © 2015 John Wiley & Sons, Ltd.     

Procedures for calibration of linear models for damage limitation in design of masonry‐infilled RC frames

Recent earthquakes have confirmed the role played by infills in the seismic response of reinforced concrete buildings. The control and limitation of damage to such nonstructural elements is a key issue in performance‐based earthquake engineering. The present work is focused on modeling and analysis of damage to infill panels, and, in particular, it is aimed towards linear analysis procedures for assessing the damage limitation limit state of infilled reinforced concrete frames. First, code provisions on infill modeling and acceptance criteria at the damage limitation limit state are reviewed. Literature contributions on damage to unreinforced masonry infill panels and corresponding displacement capacity are reported and discussed. Two procedures are then proposed aiming at a twofold goal: (i) the determination of ‘equivalent’ interstory drift ratio limits for a bare frame model and (ii) the estimation of the stiffness of equivalent struts representing infill walls in a linear model. These two quantities are determined such that a linear model ensures a reliable estimation of seismic capacity at the damage limitation limit state, providing the same intensity level as that obtained from nonlinear analyses carried out on structural models with infills. Finally, the proposed procedures are applied to four‐story and eight‐story case study‐infilled frames, designed for seismic loads according to current technical codes. The results of these application examples are presented and discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Three‐dimensional beam–truss model for reinforced concrete walls and slabs – part 2: modeling approach and validation for slabs and coupled walls

A three‐dimensional beam–truss model (BTM) for reinforced concrete (RC) walls that explicitly models flexure–shear interaction and accurately captures diagonal shear failures was presented in the first part of this two‐paper series. This paper extends the BTM to simulate RC slabs and coupled RC walls through slabs and beams. The inclination angle of the diagonal elements for coupled RC walls is determined, accounting for the geometry of the walls and the level of coupling. Two case studies validate the model: (1) a two‐bay slab–column specimen experimentally tested using cyclic static loading and (2) a five‐story coupled T‐wall–beam–slab specimen subjected to biaxial shake table excitation. The numerically computed lateral force–lateral displacement and strain contours are compared with the experimentally measured response and observed damage. The five‐story specimen is characterized by diagonal shear failure at the bottom story of the walls, which is captured by the BTM. The BTM of the five‐story specimen is used to study the effects of coupling on shear demand for lightly reinforced RC coupled walls. The effect of mesh refinement and bar fracture of non‐ductile transverse reinforcement is studied. Copyright © 2016 John Wiley & Sons, Ltd.     

Shake‐table tests of a three‐story reinforced concrete frame with masonry infill walls

This paper presents the shake‐table tests of a 2/3‐scale, three‐story, two‐bay, reinforced concrete frame infilled with unreinforced masonry walls. The specimen is representative of the construction practice in California in the 1920s. The reinforced concrete frame had nonductile reinforcement details and it was infilled with solid masonry walls in one bay and infill walls with window openings in the other bay. The structure was subjected to a sequence of dynamic tests including white‐noise base excitations and 14 scaled historical earthquake ground motion records of increasing intensity. The performance of the structure was satisfactory considering the seismic loads it was subjected to. The paper summarizes the design of the specimen and the major findings from the shake‐table tests, including the dynamic response, the load resistance, the evolution of damage, and the final failure mechanism. Copyright © 2011 John Wiley & Sons, Ltd.     

Estimation of monotonic behavior of reinforced concrete columns considering shear‐flexure‐axial load interaction

Reinforced concrete columns with insufficient transverse reinforcement and non‐seismic reinforcement details are vulnerable to brittle shear failure and to loss of axial load carrying capacity in the event of a strong earthquake. In this paper, a procedure is presented after examining the application of two macro models for displacement‐based analysis of reinforced concrete columns subjected to lateral loads. In the proposed model, lateral load‐deformation response of the column is simulated by estimating flexural and shear deformation components separately while considering their interaction and then combining these together according to a set of rules depending upon column's yield, flexural and shear strengths. In addition, lateral deformation caused by reinforcement slip in beam–column joint regions and buckling of compression bars are taken into account and considered in the analysis. Implementation of the proposed procedure produces satisfactory lateral load–displacement relationships, which are comparable with experimental data. Copyright © 2012 John Wiley & Sons, Ltd.     

地震作用下纤维编织网增强钢筋混凝土柱的抗震性能分析

为了解地震作用下纤维编织网增强钢筋混凝土柱的抗震性能,采用钢筋、混凝土、纤维编织网浇筑纤维编织网增强钢筋混凝土柱,编织网主材为碳、玻璃纤维束;利用电液伺服加载系统为试件加载地震作用,监测相关数据,部分试件置入氯化钠溶液进行多次干湿循环。不同环境下的实验结果显示:纤维编织网层数越多,纤维编织网增强钢筋混凝土柱承载能力越强,抗震性能越好;配箍间距较大时,纤维编织网增强钢筋混凝土柱的抗震性能仅在地震作用的后期呈现较差状态;干湿循环次数越多,纤维编织网增强钢筋混凝土柱承载力越弱,抗震性能越差。对于氯盐环境而言,可增加纤维编织网增强钢筋混凝土柱的抗腐蚀措施改善抗震性能。适当增加纤维编织网的数量、降低配箍间距有利于提升纤维编织网增强钢筋混凝土柱的抗震性能。     

跨黏滑断层隧道纤维混凝土衬砌抗错断技术研究

为提高跨黏滑断层隧道的结构安全性和稳定性,以都汶高速友谊隧道F 1黏滑断层段为研究背景,通过采用纤维混凝土衬砌对跨黏滑断层隧道抗错断技术进行研究。结果表明:同体积纤维掺量条件下,混杂纤维混凝土(SBFRC)立方体抗压强度比纤维混凝土(SFRC)略低,SBFRC抗折强度比SFRC略高;断层黏滑错动对隧道上盘的影响大于下盘;纤维混凝土衬砌对下盘隧道结构的抗错效果优于上盘隧道,SFRC二衬平均抗错效果为12.22%,SBFRC二衬平均抗错效果为15.81%。研究成果可为黏滑断层隧道的结构设计及施工提供参考。