Abstract
The accurate prediction of nonlinear structural behaviors under different seismic intensities is an important basis for seismic resilience assessments of building structures. The moment–rotation relationship is often used to characterize the seismic performance of connections, and is widely used in high-efficiency nonlinear structural analysis. In this paper, a method of calculating the curve using a four-linear equivalent model is presented, aiming to quantify the characteristic point parameters of the moment–rotation curves of monolithic precast beam–column (MPBC) connections for engineering design purposes. The method considered the contribution of the elastic flexure of beams and columns, the relative slip of beam longitudinal bars in the core zone, and the formation of plastic hinges at beam ends to the total deflection. Due to the presence of local complex configurations in MPBC connections, the fine fiber section method was used for moment–curvature analysis of critical beam sections. The determination of the sectional analysis processes was controlled by the strain of steel bars or concrete or their coupling effect. In addition, a two-step method was proposed to construct the moment–rotation relationship of cruciform beam–column connections for solving the deformation compatibility of beams on both sides of the column caused by asymmetric reinforcement and the strength difference between new and old concrete. To reflect the current manufacturing level of MPBC connections, 58 representative specimens reported in recent years were analyzed and classified as type 1–5. All types of MPBC connections and their 18 cast-in situ counterparts were calculated using the proposed method for both verification and quantification. The verification showed that the proposed method had good applicability to both cast-in situ and precast beam–column connections. The quantification showed that the characteristic point parameters were slightly different between these two connections. Accordingly, modification coefficients were suggested for MPBC connections to facilitate design.
Highlights
In recent years, due to the encouragement of the government, monolithic precast frame structures have been vigorously applied in China
The purpose of this paper is to propose a calculation method suitable for predicting the moment–rotation behaviors of monolithic precast beam–column (MPBC) connections based on the calculation concept of the traditional cast-in situ connections
The mean value was used to quantify the difference of characteristic point parameters between cast-in situ connections and MPBC connections, and the standard deviation was used to verify the accuracy of the proposed method
Summary
Due to the encouragement of the government, monolithic precast frame structures have been vigorously applied in China. The difference of nonlinear behavior between cast-in-place and precast structures has not received attention in design and seismic resilience assessments. It is necessary to investigate the force state of the connections under different deformations for scientifically evaluating the seismic resilience of monolithic precast frame structures. The moment–rotation relationship is an intuitive reflection of the mechanical behaviors of concrete members or their subassemblies, which includes the fundamental performance parameters, i.e., initial stiffness, load-carrying capacity, ductility, and nondestructive displacement. The moment–rotation curve can be utilized for the rapid definition of the nonlinearity of concrete members. It is widely adopted by commercial analysis software and is preferred by engineering designers. Reliable structural nonlinear analysis results can be obtained if the moment–rotation relationship of the components can be accurately predicted
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