Static And Dynamic Performance Of A New Semi-rigid C Joint System

Semi-rigid joints is a node connection between rigid joints and articulated joints, which can sustain some bending moment and have finite stiffness. However, the kind of prefabricated joints which is applicable to the spatial structure is single currently. In fact, for large-span single-layer reticulated structures, H, I and rectangular section has advantages in mechanics for building single-layer reticulated structures. Though the fabricated single-layer reticulated structures have a small amount of application abroad, the standardized design and calculation theory on the single-layer reticulated structures is still limited. Therefore, a new semi-rigid joint system named bolt-column(C) joint with the above advantages is designed and optimized in this paper, which can efficiently connect H, I and rectangular section members. The hysteretic dynamic and static performance for C joints were investigated through the experiment method, numerical simulations and theoretical analysis, in order to further study the lagged dynamic performance and seismic design method of semi-rigidly jointed shell structure. Through these studies, the useful seismic design theory and method will be established to solve the actual engineering design problems, which will promote the development of the semi-rigidly jointed domes in engineering application. The main contents of this dissertation includes:(1) The geometry design and optimization of C jointIn order to gain a better energy dissipation ability of C joint under strong earthquakes, this paper gives a group of preliminary sizes of C joint. And a three-dimensional finite element(FE) model of the joint was established to optimize the geometry size of C joint and determine the reasonable size of the components.(2) Experimental study on static performance and hysteretic behavior of C jointA series of test was carried out to study the static and hysteric performance of C joints under shear, in order to obtain the strength, stiffness, rotation behavior, and failure mode of the joints with different thickness of the side plates, pretension forces and diameters of bolts. And the strength and stiffness degradation, ductility and energy dissipation capacity of the joint specimens under cyclic loading were analyzed, to clarify the internal force, deformation and stress development of each part in the experiments.(3) Parametric study and analytical characterization of C jointBased on the ABAQUS finite element software, the mechanical behavior and failure models of the joints under bending, eccentric and axial loads were investigated and the bending-rotation curves were obtained. According to the parametric analysis, the theoretical equations and envelope curves for predicting the moment capacity of the joints under eccentric forces and bending with axial forces were established. A component method for the design of joints was adopted considering different thickness of the side plates, pretension forces and diameters of bolts. Furthermore, based on the component methods in Eurocode 3, a trilinear mathematical model for predicting the moment–rotation relationship of the joints was developed. The moment–rotation curves obtained by the mathematical model compare very satisfactorily with the experimental results.(4) Numerical simulation and theoretical analysis of the hysteretic behavior of C jointOn the basis of the static characteristics of the joints, the finite element method was used to analyze the hysteretic behavior of the joints under shear forces and bending with axial forces. By analyzing the hysteretic curves, skeleton curves and ductility ratios of the joints under different load models, the seismic performance of the joints was evaluated, showing that C joints embodies preferable energy dissipation capacity. The results obtained by the FEA models were compared with the experimental results, showing that the FEA models predict the behavior of the BC joints with good accuracy.