Seismic Performance Of Light Steel-Fast Growing Timber Composite Beam-Column Joints

There are problems of imbalanced and insufficient development in the vast number of villages and towns in China.It is an urgent requirement for the implementation of rural revitalization strategy to improve the rural living environment and build a livable and beautiful village.However,the current residential houses in villages and towns still use adobe,brick and stone masonry,and other building materials,which have problems such as poor disaster resistance,low utilization of resources and energy,and backward construction technology.It is urgent to research and develop a new system of green assembly type ecological village houses in the new era.The timber is a natural,environmentally friendly,renewable material,consistent with the requirements of green ecology,and the timber structure is also increasingly concerned.However,the widely researched and applied timber structures or steel-timber composite structures are mainly focused on glulam,which has high cost and process requirements and is difficult to promote in village houses.Fast-growing timber has a short growth period,wide distribution,and abundance of reserves,but it has low strength,more defects,large dispersion and deformation,and cannot be directly applied as structural timber.Based on the consideration of using light steel to improve the performance of fast-growing timber,our group has proposed a light steel-fast-growing timber structural system.As a key part of the structure,the joint has a great influence on the structural mechanical performance,economy,and installation convenience.Therefore,a fully bolted joint is designed in this paper,and experimental,finite element analysis,and theoretical analysis are conducted.The main research work and results are as follows:(1)The manufacturing process of the joints was explored and it was found that the use of self-tapping screws and wood screws was the easiest for the combination of components,and the beam-column connection could be quickly accomplished through bolts.The use of glue will greatly reduce the efficiency of the manufacturing process.(2)The quasi-static tests of seven joints are carried out to analyze their seismic performance.Two damage modes of the joint were obtained,and the results of the hysteresis curve,skeleton curve,ductility and energy dissipation,strength and stiffness degradation,and strain were compared.The results show that the seismic performance of joints can meet the requirements of low-rise residential buildings in villages and towns.(3)The finite element simulation of the test is also carried out,and the modeling approach is described in detail.The FE results are in good agreement with the failure modes and load-displacement curves of the specimens,which verifies the accuracy of the model and provides a reference for the analysis of similar combined members and joints.On this basis,parametric analysis was carried out to analyze the influence of parameters such as the thickness of U-shaped steel and number of bolts on the joints’ performance.(4)The component-based expression was used to propose a simplified spring model for the calculation of the initial rotational stiffness and flexural bearing capacity of the joints and compared with the experimental results for practical applications.It is indicated that the model can predict the joint stiffness and ultimate capacity better which provides a reference for the application of the joints.