| Wood is a natural and renewable building material,which has the advantages of green environmental protection,light weight,high strength,suitable for prefabrication,good seismic performance,good heat insulation,and heat insulation performance.As the National key research and development plan key special projects "Green Building and Building Industrialization" progresses,the research on wood structure building has become a hot spot.Modern wood structure architecture has been developing in North America and Europe for many years,and a series of engineering wood products have emerged,including crosslaminated timber（CLT）.The plates of cross-laminated timber are stacked orthogonally,which makes up for the bad performance of the perpendicular grain of the wood,and is widely used in multi-storey wood structure building.Compared with low-rise buildings,fire is more harmful to multi-storey wood structures.Therefore,it is of great significance to study the fire resistance of the CLT structure.Numerical simulation is an important method to study the fire resistance of CLT structure,which makes up for the shortcomings of time-consuming and arduous fire tests plus strict requirements.At present,the research method of numerical simulation and experiment has become a trend.However,the existing numerical simulation methods also have the problems of low efficiency and low accuracy.It takes hours to simulate the components under fire.For more complex CLT joints and CLT structure,it often takes days to weeks to simulate.Based on the above analysis,it is imperative to explore an efficient and accurate numerical simulation method to simulate the fire resistance of CLT joints.In this dissertation,the CLT joints were taken as the research object.The sophisticated finite element model and the simplified finite element model were combined to simulate the mechanical properties of CLT joints at room temperature,under fire and after a fire.A numerical simulation method of CLT joints fire resistance based on OpenSees is proposed.The main research contents are divided into the following parts:（1）The research results of CLT joint mechanical properties,CLT structure fire resistance and numerical simulation method of the wood structure were summarized.（2）The constitutive law of wood under normal temperature was summarized,and the wood VUMAT subroutine developed by our research group is supplemented to improve the accuracy of finite element numerical simulation of CLT joints by using the subroutine.（3）The sophisticated finite element model of CLT wall-to-floor joints with angle bracket were carried out,and the mechanical performance test of CLT wall-to-floor joints with angle bracket under normal temperature and after a fire was simulated to verify the reliability of the model.（4）The finite element model of CLT wall-to-floor joints with angle bracket was used to simulate the bearing capacity of the joints under different fire time and the residual bearing capacity after different fire time.The degradation law of mechanical properties of the joints within 60 min of fire was obtained.（5）Timberjoint RC and Timberjoint FR materials were developed in OpenSees,which are suitable for simulating the angle bracket joints of CLT wall and floor under fire.The constitutive law of the materials is based on the degradation law of mechanical properties of the joints under fire for 60 min.（6）The nonlinear spring element,which can simulate the mechanical properties of the joint under fire,is generated by combining Timberjoint RC and Timberjoint FR with the zerolength element in OpenSees.The spring element is tested and verified to be reliable.Finally,a simplified model of CLT wall-to-floor joints with angle bracket was established in OpenSees.The numerical simulation of the joint fire resistance was carried out.The influence of load holding level and screw length on the joint fire resistance was studied.The calculation speed of fire resistance simulation of CLT angle bracket connections in OPENSEES and ABAQUS was compared... |
PDF Full Text Request