疲劳荷载作用后锈蚀钢筋混凝土梁承载力理论计算方法

锈蚀钢筋混凝土的疲劳破坏是在钢筋锈蚀和疲劳荷载共同作用下造成的结构破坏,其危害巨大。准确获得锈蚀钢筋混凝土构件在经历若干次疲劳荷载作用后的实际承载能力更是具有重要的现实意义。本文在理论上对疲劳荷载作用后锈蚀钢筋混凝土梁承载力进行分析。首先,考虑锈蚀因素对钢筋混凝土梁承载力的影响;其次,考虑疲劳荷载作用对钢筋混凝土梁承载力的影响;最后,考虑上述两种因素的影响,修改现行规范的未锈蚀钢筋混凝土梁抗弯承载力公式中的钢筋屈服强度及截面面积,获得若干次疲劳荷载作用后锈蚀钢筋混凝土梁抗弯承载力的理论计算公式。     

钢筋混凝土梁在低周反复荷载作用下受剪性能的尺寸效应试验研究

本文介绍了5组不同尺寸钢筋混凝土梁在低周反复荷载作用下的剪切破坏试验研究成果.研究中分析了钢筋混凝土梁斜截面受剪的滞回特性、承载力、延性和耗能等力学性能,及其尺寸效应的影响规律.结果表明:在本试验设计的尺寸范围内,钢筋混凝土梁在低周反复荷载作用下的受剪性能存在非常明显的尺寸效应现象,钢筋混凝土梁的强度、延性等力学性能均...     

基于界面疲劳理论的钢筋混凝土腐蚀疲劳破坏研究

腐蚀疲劳是钢筋混凝土结构破坏的主要因素之一.基于剪切筒模型及文中选用的实验加载方式,考虑界面摩擦系数的衰减,同时考虑力学因素-应力比R和加载频率f的影响,研究了钢筋与混凝土界面腐蚀疲劳裂纹扩展情况.通过对Paris公式的修正,借助能量耗散率给出腐蚀疲劳数学模型,得到了界面腐蚀疲劳脱粘速率,脱粘长度与循环荷载作用次数的关系.同时考虑混凝土损伤(如刚度衰减)的影响,分析了影响界面腐蚀疲劳(CF)裂纹扩展速率的因素,如应力比,加载频率.     

碳纤维加固与钢板加固混凝土梁抗震性能对比

通过对地震损伤钢筋混凝土梁加固修复方法的研究,进行了不同配筋率的梁在水平低周反复荷载作用下的试验。对损伤后的梁进行了加固修复,并对加固修复梁在再次地震作用下的抗震性能进行了试验。主要研究内容:完成了6根试验梁的制作,并对其在位移控制下进行了水平低周反复荷载试验,重点研究了不同配筋率的钢筋混凝土梁碳纤维加固与钢板加固的抗震性能分析比较。     

再生钢筋混凝土柱疲劳性能多尺度研究

再生混凝土是一种绿色、可循环建筑材料。当其用于结构构件时,可能会因遭受荷载作用而发生疲劳现象。因此,针对不同再生骨料掺合比(0,50%,100%)的再生钢筋混凝土试件进行疲劳强度试验,通过多尺度(微观和宏观)观察并分析试件,分析受轴心和偏心疲劳荷载作用下不同掺合比的再生钢筋混凝土试件疲劳性能差异。此试验方法和数据结果可为研究、分析其在工程中的运用提供基础依据。     

锈蚀作用下钢筋混凝土梁承载力退化规律研究

为了掌握锈蚀对钢筋混凝土梁正截面承载力的影响规律,采用电加速锈蚀试验与理论分析相结合的方法,对不同锈蚀等级下钢筋混凝土梁的承载力退化进行了研究。结果表明,钢筋从未锈蚀到严重锈蚀过程中,梁从典型的适筋梁破坏逐渐转化成典型的少筋梁破坏。随着腐蚀程度的增加,梁的极限承载力下降、延性降低、刚度减小。腐蚀量小于1%的情况下,梁的极限承载力略有提高。当腐蚀量增加至24%时,由于严重的局部腐蚀以及锈胀裂纹的存在及扩展都使得梁的极限承载力较经验模型出现较大降低。在钢筋锈蚀率小于24%的情况下,采用协同系数或基于规范的计算模型,能够较准确地计算钢筋混凝土梁正截面受弯极限承载力的影响。     

锈蚀钢筋混凝土压弯构件恢复力模型研究

根据目前已有试验资料和理论分析,结合钢筋锈蚀引起结构破坏形态的改变,综合考虑结构各种耐久性损伤因素,并对箍筋锈蚀进行修正,提出了锈蚀钢筋混凝土压弯构件基于地震损伤的恢复力模型的确定方法.通过与现有试验进行对比分析,表明模型描绘的骨架曲线与试验结果总体吻合较好,模型计算的滞回曲线所描述的现象与试验一致,该恢复力模型可在损伤钢筋混凝土结构地震反应分析中采用.     

角钢高压输电塔疲劳寿命计算与分析

输电塔结构长期受到风、雨等环境荷载作用,常常发生高周疲劳破坏甚至倒塌,但到目前为止该方面的研究还很缺乏。本文以一500kV酒杯型输电塔结构为工程对象,模拟了风荷载时程;通过计算得出结构的危险杆件,利用雨流法统计出应力时程;并基于损伤容限理论和断裂力学理论,计算了输电塔的疲劳寿命。结果表明,结构构件的疲劳破坏对于输电塔整体寿命有重要影响,需要有针对性的防范与加固。     

RC梁与柱在不同地震作用下的变形限值分析

分析钢筋混凝土(RC)梁与柱基于不同地震作用下的变形限值,对钢筋混凝土梁与柱进行低周往复循环加载拟静力试验。然后对试验进行仿真模拟,将试验结果与仿真模拟结果进行对比分析,发现二者结果相近,从而验证仿真模拟的可行性。在构件的荷载-位移曲线上获取屈服点、峰值点和极限点,分别计算这3个状态点对应的侧向位移值与构件计算长度的比值,则可得出构件在小震、中震和大震时对应的位移角值。改变梁、柱构件的剪跨比、配筋形式以及柱构件的轴压比等,来得到更多构件的荷载-位移曲线,将所有结果进行统计分析,得到钢筋混凝土构件在不同地震作用下的位移角限值。     

基于应变能耗储的钢筋混凝土框架结构地震损伤演化研究

结构地震损伤破坏,本质上是地震动输入能量超出结构或构件耗能能力所致。“能量”参数能够综合反映地震动强度、频谱特性以及强震持时对结构破坏的影响,本文基于能量耗散原理建立结构损伤模型,采用有限元软件ABAQUS对3榀单层单跨钢筋混凝土平面框架结构抗震性能进行数值模拟,通过损伤指数量化研究了地震作用下钢筋混凝土框架结构的损伤演化规律。研究表明:基于应变能耗储的结构损伤模型,能够合理有效地反映“位移首超破坏”与“累积损伤破坏”模式,且上、下界收敛;模拟分析得到的滞回曲线和骨架曲线与试验数据吻合较好,数值建模方法适用于以梁、柱构件为主的框架结构抗震性能分析;耗能构件框架梁能够对结构损伤破坏发展和抗震性能劣化起到一定延缓作用,承力构件框架柱的损伤加剧会加速结构抗震性能的劣化;加载幅值较小时,结构依靠混凝土裂缝闭合摩擦消耗能量,“位移首超破坏”所致损伤所占比例较大,随着位移幅值及循环次数的增加,“累积损伤破坏”所致损伤所占比例逐渐增大。     

Effects of reinforcement slippage on the non‐linear response under cyclic loadings of RC frame structures

This paper discusses the importance of including the bond‐slip effects in assessing the response under cyclic loads of reinforced concrete frames. The discussion is based on analyses performed using numerical models which are simple, computationally efficient and capable of representing the salient features of reinforced concrete frames under both static and dynamic loads. The numerical models comprise a displacement‐based, reinforced concrete frame element with bond‐slip and a rigid beam column joint element with bond‐slip. Two applications illustrate the model accuracy and show the importance of including bond‐slip. The first application considers a reinforced concrete beam‐column subassemblage experimentally tested under cyclic loads. The second application considers the shaking table test of a two‐story one‐bay reinforced concrete frame In both cases the analytical results correlate well with the experimental results in terms of strength, displacement demands and hysteretic energy dissipation. Furthermore, the paper shows how the analyses that include bond‐slip yield a better correlation with the experimental results with respect to the analyses that assume a perfect bond. Copyright © 2003 John Wiley & Sons, Ltd.     

寒冷地区无粘结预应力混凝土梁的抗弯与疲劳强度研究

针对我国行业标准《无粘结预应力混凝土结构技术规程》(以下简称《规程》)中，对无粘结预应力筋的极限应力设计取值规定的不足，根据大量的试验数据，推导出了适用于桥梁工程的无粘结预应力混凝土上部结构多种截面形式的无粘结筋极限应力增量实用简化计算方法。同时根据试验结果得出无粘结预应力混凝土受弯构件在反复荷载作用下的性能是可靠的结论。     

基于分灾模式的钢筋混凝土梁抗弯加固性能评估方法

针对当前钢筋混凝土梁抗弯加固性能评估法未考虑不同建筑结构的抗灾差异,所求得的各项承载力参数不够客观,从而造成评估结果与实际检测结果差异大,评估精度低的问题,提出基于分灾模式的钢筋混凝土梁抗弯加固性能评估方法。计算梁底初始拉应变、梁正截面极限抗弯承载力和钢筋混凝土梁正截面荷载挠度,然后设计分灾模式的钢筋混凝土梁抗弯加固,通过分析载荷与压应变、载荷与挠度以及剪力与位移变化,得到钢筋混凝土梁抗弯加固后各项承载力参数,输入各项梁承载力参数到ANSYS通用程序,利用该程序结合钢筋混凝土梁抗弯加固性能进行评估。通过进行仿真实验,结果表明加入分灾元件的钢筋混凝土梁抗弯加固性能有明显提高。将本文方法评估结果与实验实际评估结果对比可知,提出的评估方法与实际检测结果基本一致,评估精度准确性较高。     

基于缝宽-滑移理论的铝合金配筋混凝土梁粘结性能研究

铝合金筋与混凝土的粘结性能是影响铝合金配筋新型混凝土梁承载力的重要因素。对9根铝合金配筋混凝土梁和2根钢筋混凝土对比梁进行了静载试验,分析混凝土梁在加载过程中的裂缝发展情况,基于缝宽-滑移理论研究试验梁的粘结性能。研究结果表明:同级荷载作用下,钢筋混凝土梁的裂缝宽度小于铝合金配筋混凝土梁,钢筋与混凝土的粘结性能优于铝合金与混凝土的粘结性能;混凝土梁中纵筋所受拉力,实质上是混凝土开裂后,单元体内部粘结力的合力;纵筋与混凝土的粘结滑移量与粘结力直接相关,可通过代数和微积分计算得到二者的对应关系。     

横向预应力混凝土梁的抗剪性能试验研究

通过4根加配横向预应力筋的钢筋混凝土梁和1根普通钢筋混凝土梁的对比试验,初步考察了横向预应力筋对提高钢筋混凝土梁抗剪性能的良好效果。研究结果表明:(1)加配横向预应力筋并施加适当预应力之后,钢筋混凝土梁的抗剪承载力提高70%以上,即使在不施加预应力的情况下,梁的抗剪承载力也约有40%的增长;(2)在横向预应力筋的总截面面积一定的情况下,采用直径较小的横向预应力筋和较小的间距,更有助于改善钢筋混凝土梁的破坏形态。     

The reinforcement contribution to the cyclic behaviour of reinforced concrete beam hinges

The cyclic behaviour of plastic hinges is an essential component in tracking the behaviour of RC frames to failure, not only for monotonically increasing force/pressure loads such as under extreme wind loads but also for dynamic displacement-driven loads such as under earthquake ground motions. To describe member deformations at ultimate loading, traditional moment–curvature techniques have required the use of an empirical hinge length to predict rotations, and despite much research a definitive generic expression for this empirical hinge length is yet to be defined. To overcome this problem, a discrete rotation approach, which directly quantifies the rotation between crack faces using mechanics, has been developed for beams and been shown to be accurate under monotonic loading. In this paper, the discrete rotation approach for monotonic loads is extended to cope with cyclic loads for dynamic analyses, and this has led to the development of a new partial interaction numerical simulation capable of allowing for reversals of slip of the reinforcing bars. This numerical tool should be very useful for the nonlinear analysis of reinforced concrete beams and reinforced concrete columns with small axial loads under severe dynamic loads. Copyright © 2011 John Wiley & Sons, Ltd.     

GFRP筋混凝土梁耐火性能的试验研究

进行了4根GFRP筋混凝土简支梁在ISO834标准升温曲线下的火灾实验,试件依据ACI440.1R-06进行截面设计,分别考虑了不同荷载比、保护层厚度、端部锚固方式对梁耐火性能的影响。试验结果表明,GFRP筋混凝土梁在火灾中的裂纹开展深度较传统的钢筋混凝土结构明显偏大。由于GFRP筋横向膨胀大更易造成梁底混凝土的开裂与剥落,建议在满足纵筋锚固性能要求的前提下,尽量减少端部J型锚固筋。GFRP筋在高温下的材料性能衰减严重,合理的设计保护层厚度和限制GFRP筋的使用内力,可使GFRP筋混凝土梁的耐火性能满足实际工程的需要。     

Experimental investigation on dynamic and quasi‐static behavior of low‐rise reinforced concrete walls

Experimental evidence supporting the fact that results from quasi‐static (QS) test of low‐rise reinforced concrete walls may be safely assumed as a lower limit of strength and displacement, and energy dissipation capacities are still scarce. The aim of this paper is to compare the seismic performance of 12 reinforced concrete walls for low‐rise housing: six prototype walls tested under QS‐cyclic loading and six models tested under shaking table excitations. Variables studied were wall geometry, type of concrete, web steel ratio, type of web reinforcement and testing method. Comparison of results from dynamic and QS‐cyclic tests indicated that stiffness and strength properties were dependent on the loading rate, the strength mechanisms associated with the failure mode, the low‐cycle fatigue, and the cumulative parameters, such as displacement demand and energy dissipated. Copyright © 2012 John Wiley & Sons, Ltd.     

Cyclic behaviour of interior beam–column joints reinforced with plain bars

The seismic damages commonly observed on beam–column joints of old reinforced concrete structures, built with plain bars and without proper detailing, justifies the need to further study the behaviour of this type of structures. The response of these structures when loaded cyclically, as occurs during the earthquakes, is partially controlled by the bond properties between the reinforcing bars and the surrounding concrete. This paper presents the results of an experimental campaign of unidirectional cyclic tests carried out on six full‐scale beam–column joints built with plain bars. These joint specimens are representative of existing reinforced concrete structures, that is, built without adequate reinforcement detailing for seismic demands. For comparison, an additional specimen is built with deformed bars and tested. The seven specimens are designed and detailed to allow the investigation of the influence of bond properties, lapping of the longitudinal bars in columns and beams, bent‐up bars in the beams, slab contribution and concrete strength. The lateral force–drift relationships, global dissipated energy evolution, contribution of the joint, beams and columns to the global dissipated energy, ductility, equivalent damping, final damage observed, homogenized reinforced concrete damage index, displacement components, curvature evolutions and Eurocode requirements are presented and discussed. Copyright © 2014 John Wiley & Sons, Ltd.