【作者】 王敢峰；

【导师】 支运芳；

【作者基本信息】 重庆大学 ， 结构工程， 2004， 硕士

【摘要】 以往对钢筋混凝土梁抗剪性能的实验研究中,为保证最终发生剪切破坏,常有意将梁的单侧纵筋配筋率设置得很大,通常大于2.8%,这与实际工程中单侧纵筋配筋率一般在1.0～1.5左右的实际情况差距较大。所以,建立在这种单侧纵筋配筋率较高的梁的受剪性能试验数据基础上的规范抗剪设计方法可能是偏不安全的。张川教授的硕士研究生陈臣同学已就集中荷载作用下剪跨比为1.5不同单侧纵筋配筋率的有腹筋约束梁进行了抗剪性能研究,这些试件采用上下对称的纵筋通长布置; 而实际工程中上部纵筋一般要截断。因此本课题提出在试验构件各种参数与陈臣试验均相同的情况下按现行规范把梁上部纵筋截断,探索在这种情况下约束梁的抗剪性能与陈臣试验结果是否存在差异,以找出更接近工程实际的单侧纵筋配筋率对有腹筋约束梁的抗剪性能的影响规律。本文通过集中荷载作用下五根不同单侧纵筋配筋率的有腹筋约束梁在负筋截断时的试验,深入研究了在纵筋截断下有腹筋约束梁的受剪破坏全过程及纵筋配筋率对抗剪强度的影响。首先,通过单调静力加载试验,对梁的裂缝的产生和发展、纵筋应变、箍筋应变、梁的挠度等指标进行了记录和数据采集,试图追踪试件中纵筋应变状态的变化和裂缝发展程度的相关性,进而总结出有腹筋约束梁裂缝开展及钢筋应力分布的一般规律。其次,通过对比研究不同单侧纵筋配筋率试件的裂缝开展和延伸规律、破坏形态特征以及承载力等,初步总结了纵筋配筋率的影响规律,并与陈臣试验结果进行对比。研究结果表明,钢筋混凝土有腹筋约束梁的裂缝开展过程大致可分为裂缝扇形区的逐步形成、劈裂裂缝出现和发展、临界斜裂缝加速发展至破坏等阶段;纵筋率的变化对裂缝的发展有显著的影响;抗剪承载力实测值高于我国规范计算值平均61%;随着单侧纵筋配筋率的提高,约束梁的抗剪承载力有规律的增长;与陈臣试验的结果相比,没有发现二者之间明显的规律,说明考虑上部纵筋截断的有腹筋约束梁的抗剪承载力没有因上部纵筋截断而降低。更多还原

【Abstract】 In general,to ensure the final shear failure,a very large longitudinal reinforcement ratio,usually larger than 2.8%,was chosen as a prerequisite in previous studies on shear behavior of reinforced concrete beams. It is very different from that in practice,under such circumstance the longitudinal reinforcement ratio is among 1.0~1.5%. The codified design equations based on such testing data may be unconservative.ChenChen ,the master of zhangchuan professor,has studied the effect of longitudinal reinforcement ratio on shear behavior of restrained beams with web reinforcement when shear-span ratio is 1.5,and the longitudinal reinforcement of his tries was disposed through the whole beam;But the top longitudinal reinforcement of beam is usually truncated in practice. Therefore,it is put forward that studies that the effect of longitudinal reinforcement ratio on shear behavior of restrained beams with web reinforcement when the top longitudinal reinforcement of beam is truncated according to the China Design Code,and comparing the results of different tests,and then wishing that that find some disciplinarian approaching the civil practice.In this paper,five restrained beams with web and different longitudinal reinforcement ,and above longitudinal reinforcement is truncated,were tested under static point loads . On this basis,the overall process of cracking development under shear and the effect of longitudinal reinforcement ratio on it was investigated.At first,development of various cracks carefully recorded and strains on both the rebars and the stirrups were measured in detail,together with the deflections of the beam. In such a way,correlation between the measured strain profiles of the reinforcement and the observed cracking development of each specimen was pursued. Principal factors contributing to the cracking pattern and failure mode were figured out as a result. Secondly comparison of the tested results unveiled effect of various longitudinal reinforcement ratios on development of cracks,final failure mode,and ultimate capacity. Primary conclusions were thus drawn,and the tests results were compared with ChenChen tests results. The experiments showed that the cracking process of such restrained beams in this paper can be divided into three phases,that is,formation of the fanning zones,initialization and development of splitting cracks along longitudinal reinforcement,and <WP=7>accelerating development of the critical cracks. Different amount of longitudinal reinforcement has a significant impact on formation of different cracks. As for ultimate shear capacity,the difference between the predicted results obtained from the China Design Code and the tested results is 61%. Ultimate shear capacity of restrained beams is increasing disciplinarian with the increasing longitudinal reinforcement ratio. It was not founded of evident disciplinarian between the results of this test and the results of ChenChen test,and it shows that shear behavior of restrained beams with web reinforcement is not receded when the top longitudinal reinforcement of beam is truncated.更多还原