附加节点斜筋对梁柱节点区域粘结机制的影响

THE EFFECT OF ADDITIONAL DIAGONAL BARS ON THE BOND MECHANISM IN A BEAM-COLUMN JOINT

梁柱节点在非弹性阶段的表现同钢筋和混凝土之间的相互作用有极大的关系。不仅因为梁纵筋的粘结 -滑移效应 ,尤其是发生在柱面处的滑移是使整个结构试件刚度下降的重要原因 ,也因为纵筋的粘结应力分布直接影响到节点内的抗剪机制。梁柱内节点在反复循环荷载下通常面临最不利的粘结条件 ,提出的一种新的附加斜钢筋的节点构造方式 ,被证明能有效地提高梁柱内节点的性能 ,而又避免了其内部钢筋拥挤的情形。附加斜筋的出现抑制了节点裂缝和梁柱界面裂缝的发展 ,这对保持节点的刚度是至为重要的。由于梁塑性铰出现在柱面以外一段距离 ,节点核心混凝土可避免来自钢筋的屈服渗透 ,而加强混凝土斜压杆的作用。降低了的梁内纵筋的应力能在反复循环荷载下获得较为有利的粘结条件 ,特别是在缺少柱上轴向压力的时候。

The inelastic analysis of a beam-column joint is highly dependent on the interaction between the rebars and the concrete.On the one hand,this is caused by the bond-slip effect particularly in the vicinity of the column face that accounts mainly for the stiffness degradation of the whole structural specimen. On the other hand,the bond stresses on the longitudinal bars also affect the shear stress in the panel directly.The proposed use of additional diagonal bars is proved effective to improve the behaviour of interior beam-column joints that are often exposed to the most unfavorable bond condition under reversed cyclic loading.It also avoids congestion of reinforcement in the panel.The presence of diagonal bars prevents the development of both joint cracks and interface cracks,which helps to maintain the stiffness of the joint. The shifting of beam plastic hinge away from the column face may protect the core concrete from yielding penetration and enhance the action of concrete strut.The reduced stresses in the longitudinal bars help to achieve less critical bond condition under the cyclic loading,especially in the lack of column axial force.