Research On Hysteretic Models For Truss Members And Seismic Collapse Simulation Of Truss Structures

Space truss structures have been extensively used in electric power-line transmission towers,bridges,offshore platform structures,and roofs of large-span structures.This type of structure is sensitive to both material and geometric nonlinearities.The buckling or failure of a truss member will lead to the structural dynamic response and even the progressive collapse.It is common to see the destruction and collapse of truss structures subjected to earthquakes.For instance,more than 20 power transmission towers underwent seismic collapse during the 2008 Wenchuan earthquake causing the paralyzing of the electric supply system and great economic losses.Therefore,it is of great value to engineering practice to study the hysteretic models for truss members and simulate the seismic collapse of truss structures.This study is mainly focus on the following aspects:1.Based on the finite element software of ABAQUS,creating a refined finite element model was capable of reflecting hysteretic behaviors of a truss member accurately.The model can identify the local buckling locations and the fracture failure,and was verified by comparing the results with experiments.2.The phenomenological hysteretic model for circular steel tube was proposed.The model was calibrated using numerical and experimental data by CFT(curve fitting toolbox)available in MATLAB.The model can consider the yielding and hardening in tension,inelastic buckling in compression,the degradation of buckling capacity due to Bauschinger effect,and the degradation of yielding strength and fracture due to low-cycle fatigue effect.The simulation results of hysteretic loops for members agreed well with results obtained by finite element models.3.The physical theory model for members was proposed based on the concentrated plastic hinge theory.The model can also simulate a series of complex physical phenomena,such as yielding in tension,inelastic buckling in compression,Bauschinger effect and growth effect.In addition,the model was applicable to various sections of truss members.The hysteretic response of members matched perfectly with experiments,which verified the accuracy of the proposed model.4.Based on the platform of MATLAB,the explicit dynamic program was developed to simulate the dynamic response of truss structures.The reliability of the program was verified by comparing responses of structures obtained from the proposed method with results from ANSYS using ideal elastic-plastic model to simulate members;the physical hysteretic model and the phenomenological hysteretic model were implemented in the proposed program to simulate the inelastic response of truss structures;the fracture criteria of each model were defined to achieve the simulation of seismic collapse of structures.5.The IDA analysis for a real electric power transmission tower with 122 m in height was conducted to evaluate the resistance of seismic collapse.It showed that the high-rise tower is with greater safety factor.