钢筋混凝土节点核心区剪切破坏尺寸效应试验研究

Size effect on shear failure at core region of reinforced concrete connections: Experimental study

设计了最大节点核心区尺寸为700 mm×700 mm的14个几何尺寸相似的钢筋混凝土(RC)框架梁-柱节点(中间层中节点)试件,对其在不同加载方式(单调与循环加载)下的力学性能进行了试验研究.研究了荷载形式、配箍率及尺寸对节点核心区剪切破坏行为的影响规律;重点分析了节点核心区名义剪切强度的尺寸效应规律,并初步讨论了尺寸效应产生的根源.试验结果与分析表明:(1)不同荷载形式作用下RC梁-柱节点的破坏均为核心区脆性剪切破坏;(2)由于低周疲劳损伤特性,循环荷载作用下节点剪切强度较低,且变形能力较弱;(3)节点名义剪切强度随结构尺寸增大而减小,尺寸效应显著;(4)随着箍筋率的提高,节点抗剪承载力及变形能力增强,剪切强度的尺寸效应行为被削弱.本试验中,混凝土破坏的主导效应以及加载的低周疲劳特性是剪切破坏尺寸效应产生的主要原因.

Fourteen geometrically-similar interior reinforced concrete(RC)beam-to-column connections whose maximum structural sizes were700 mm×700 mm were designed.The seismic performances of these RC beam-to-column connections subjected to monotonic and low-cycle loading were tested.The effects of loading type,structural size and stirrup ratio on the shear failure behavior at the core region of the connections were studied.Moreover,the size effect on the nominal shear strength of the core region of RC connections was examined,and the sources of size effect were also discussed.The test results and analyses indicate that:(1)all the RC beam-tocolumn connections under monotonic and low-cycle loading failed by shear;(2)due to the existence of low-cycle fatigue damage characteristics,the nominal shear strength of the joints under cyclic loading is lower,and the deformation capacity is weaker;(3)the nominal shear strength decreases with the increase of the structural size of RC connections,and size effect phenomenon is obvious;(4)with the increase of stirrups ratio,the shear bearing capacity and deformation capacity of RC connections increases,at the same time the size effect in shear strength is weakened.In this experiment,the dominant effect of concrete failure and the low-cycle fatigue characteristic of loading are the main reasons for the size effect of shear failure.