Structural Design of Connections in Precast Reinforced Concrete Structures

在预制混凝土连接的设计中，必须经常考虑一定界面上的剪力传递。给出了影响剪切传递强度的各种阻力：(1)销钉作用，(2)剪力键，(3)与轴力的摩擦，(4)对混凝土表面的粘结。为了揭示各种阻力元素的复合效应，对预制缝端面的界面剪切传递进行了基本实验。进行了15个相同尺寸的板式试件的试验，用于研究剪力传递机理的试件由两个混凝土砌块组成。所有试件的尺寸和加固细节相同：宽900 mm，高1400 mm，厚225 mm，界面860 mm×225 mm，距底部700 mm的高度。调查了下列参数：(A)混凝土连接中的抗剪强度[fr…(B)横向作用于混凝土界面的直接力[N=0,1500，-220kN]。与轴向力的摩擦力可以从滞回曲线粗略地估计如下：(A)根据不同轴力水平下试件的第一个正的最大强度来估算摩擦力，摩擦力与轴向力成正比。(B)在循环载荷作用下，与轴向力的摩擦可能发生在平坦的水平上，重新加载到相反的方向，直到与原始位移相遇。从滞回曲线可以粗略地估计出销钉的作用如下：(A)实质刚度逐渐减小。(2)最大剪切位移随循环次数的增加而增大。(C)夹持效应非常明显，随着循环次数的增加，滞回环的面积减小，滞回环的刚度较大，直到剪力键发生压缩破坏时，其位移最小。研究结果表明：(A)在相同的剪切位移下，总的抗剪强度可以用各剪切传递单元的总和来计算。(B)Dowel作用不受轴压的影响。(C)剪力键的结构性能(抗力和刚度)随着轴力的增加而提高。对混凝土节点在剪力和轴力作用下的剪切传递和剪切位移行为进行了基本试验。主要结论如下：(1)阐明了混凝土节点的剪切传递机理和剪切滑移行为。并通过结构试验验证了剪力传递机理。(B)剪力传递强度可以用各剪力传递单元在相同剪切位移下的总和来计算。并给出了评价方程。较少

Shear transfer across a definite interface must frequently be considered in the design of precast concrete connections. As the following various resistances in the effecting shear transfer strength are given : (1) dowel action, (2) shear-key, (3) friction with axial force, (4) adherence on the concrete surface. The purpose of this paper is to reveal the compound effects of the various resistance elements.Basic experiments on the interface shear transfer at the precast joint faces were carried out. Fifteen panel type specimens with the same dimensions were tested.The specimens used for investigation of the shear transfer mechanism consisted of two concrete blocks. The dimensions and reinforcement details of all the specimens were identical : the width of 900 mm, the height of 1400 mm, the thickness of 225 mm with an interface of 860 mm × 225 mm at the height of 700 mm from the base. The following parameters were investigated : (a) the kind of shear resistance in concrete connections [fr … More iction with axial force, dowel bar, shear-key, and compound of various elements], (b) the direct force acting transverse to the concrete interface [N=0,1500,-220 kN].The friction with axial force can roughly be evaluated from the hysteresis loop as follows : (a) Friction can be estimated from the first positive maximum strengths of the specimens under different axial force levels, and the force is proportional to the axial force. (b) Friction with axial force under cyclic loading may be taken at the flat level during reloading to the opposite direction until it meets the original displacement.The dowel action can roughly be evaluated from the hysteresis loop as follows : (a) Substantial stiffness decreases gradually. (b) The maximum shear displacement with cycling increases. (c) The pinching effect is very pronounced, and the area of hysteresis loops with cycling decreases.The stiffness of the hysteresis loop is high and the displacement of that is minimal until the compressive failure of shear-key. The resistance after compressive failure is constant.Research results lead to the following : (a) Total shear resistance can be evaluated as the sum total of each shear transfer element at the same shear displacement. (b) Dowel action is not influenced by compressive axial force. (c) Structural performance (resistance and stiffness) of shear-key increases by the compressive axial force.Basic experiments on concrete connections were conducted on the shear transfer and the shear displacement behavior in concrete connections under shear and axial force. The following conclusions may be drawn.(a) The shear transfer mechanism and shear slipping displacement behavior in concrete connections is clarified. And the shear transfer mechanism is verified by the structural experiments.(b) The shear transfer strength can be evaluated as the sum total of each shear transfer element at the same shear displacement. The evaluation equation is also proposed. Less