框架柱托换节点界面力学性能试验研究

EXPERIMENTAL STUDY ON MECHANICAL BEHAVIORS OF COLUMN-BEAM INTERFACE OF FRAME UNDERPINNING JOINTS

梁柱新旧混凝土结合面是框架结构托换节点的薄弱部位。为了提高梁柱结合面承载能力,进行了配置不同界面钢筋的14组托换节点试件的静力加载试验研究。结果表明:托换节点的破坏由两种形式控制,托换节点界面滑移破坏或托换梁受剪破坏。当梁柱结合面不设置界面钢筋或界面钢筋配筋特征值(钢筋屈服强度设计值与其面积的乘积)小于2 MPa时,托换节点发生界面滑移破坏;当界面钢筋配筋特征值大于2 MPa时,托换节点的破坏形式由界面破坏转变为托换梁的受剪破坏。提出考虑界面钢筋的摩擦剪切公式,并确定了其中的参数。在托换节点设计时,可以根据托换梁的受剪承载力及界面承载力计算公式确定界面钢筋的配置量,确保托换节点的结合面不发生破坏,实现托换节点的优化设计。

The new-to-old concrete interface between the underpinning beam and column is a weak zone of the underpinning joint. Experiments of fourteen specimens with two span ratios and various interface reinforcements were carried out. The results show that the failure mode can be divided into two types： interface failure and shear failure of underpinning beam. The interface failure occurs in the cases of no interface reinforcement or the characteristic value（product of reinforcement yield strength and its area） of the interface reinforcement being less than 2 MPa. When the characteristic value of the interface reinforcement is more than 2 MPa, the interface failure will convert to shear failure of the underpinning beam. Based on the shear-friction model, the calculation formula for calculating the interface bearing capacity was put forward and the involved parameters were determined. In the actual design of the underpinning joints, the amount of the interface reinforcements can be determined according to the bearing capacity of the beam and the interface. The bearing capacity of the underpinning beam is firstly calculated, and then the interface reinforcement is obtain using the interface formula, which ensures the safety of the interface and achieves the optimal design.