Research On Dynamic Stability Of Single-Story Steel Frame Under Earthquake Action

Steel frame structures are more and more widely applied to practical engineering due to their many merits, such as high strength, good plasticity and tenacity, light weight and being fit to work in dynamic loads. At present, static stability theories and design methods of steel frames have trends to maturity, but it is lack of dynamic stability research on steel frames, and there is little not enough developments to corresponding theory and experimental research .Therefore, it has importantly theoretic and practical value to study dynamic stability and establish stability estimation rules of steel frame structures. It is aseismic theoretic foundation to avoid the collapse of frame structures that dynamic stability of steel frame structures is studied under earthquake action.This paper studies mostly dynamic stability of single story steel frame structures. The main investigations are summarized as follows:Part 1. According to different axial compression ratio and slenderness ratio, this paper designs 15 types of single story steel frame structures that are used to study dynamic stability under earthquake action, and gives overall dimensions and characteristic parameters, then provides data for establishing ANSYS finite element models that is applied to analysis static and dynamic nonlinear characters of steel frame structures.Part 2. This paper introduces two theories that were put forward by American scholars on bilinear horizontal force and displacement relationship of single-story steel frame structures, namely, nonmodified theory and modified stiffness theory. However they didn't consider influence of P-A effects to cross-section plastic moment of frame columns. Based on analysis of civil and abroad scholars to single-story steel frame structures, This paper puts forward to bilinear horizontal force and displacement relationship of modified cross-section plastic moment. Nonlinear static analysis of single-story steel frames is studied adopting arc-length method of finite element method(FEM).Skeleton curves of single-story steel frames for different spans under monotonous loading are presented and show that the span of frames don't affect on Skeleton curves. Results show that bilinear horizontal force and displacement relationship of modified cross-section plastic moment put forward by this paper are of high accuracy.Part 3. Firstly, NONLIN(a software applied to single freedom system )is applied to analysis on dynamic stability of single-story steel frames , it is convenient and quick in determinating critical accelerations of frame dynamic instability considering P- A effects .So it can provide input acceleration for more meticulous ANSYS dynamic stability analysis of single-story steel frames . hysteretic curves of single-story steel frames by NONLIN is presented. ON the basis of it, we study dynamic stability of single-story steel frames by ANSYS. In paper, APDL advanced parameter design language is applied in addition to command flows of adding earthquake wave to frame structures and key operation steps of ANSYS are given. Four types of curves , namely, time-history curves of displacement-time, hysteretic curves of restoring force-displacement, phase-plane trajectory curves, time-history curves of energy-time are plotted, these can provide evidence for establishingdynamic stability criteria of single-story steel frames.Part 4. Based on the summarizes on dynamic stability criteria of single freedom system and analysis of four types of curves obtained in this paper, three types of dynamic stability criteria of single-story steel frames .namely, displacement-time stability criteria, phase-plane trajectory stability criteria and energy stability criteria are put forward by author.Part 5. we analyzed key parameters on dynamic stability of single-story steel frames . firstly, by comparing general calculate methods of elastic-plastic displacement in practical engineering, request of aseismic design criterion with elastic-plastic displacement on dynamic instability of single-story steel frames,...