Investigation On Damage Identification Of Steel Frame Structure Based On Static And Dynamic Parameters

In recent years, civil engineering structures are developing towards large-scale and complexity, various kinds of new structural systems have appeared. However, due to reasons such as design, construction, service and load, the civil engineering structures often suffer from different kinds of damages, which cause the change in strength, stiffness and mechanical properties of structures and affect their function and service. Therefore, it is necessary to identify the damages in engineering structures.Taking a steel frame as the research object, the damage identification method based on the dynamic and static parameters is investigated by means of static load test and finite element analysis. The main research contents are summarized as follows:1. The simplified formulas for calculating joint angle and interlayer chord angle are proposed for the single-layer plane steel frame under the action of horizontal concentrated load. The relationship between local damage and the corresponding component damage of frame is established. The modified formulas for analyzing the joint angle and interlayer chord angle after the occurrence of local damage are given.2. The sensitivity of joint angle and interlayer chord angle under horizontal concentrated load for damage is studied through the finite element analysis and static load experiment. The curvature index of static deflection difference is used to determine the damage location in frame.3. Through the finite element modal analysis, the sensitivity of frequency decrease rate and vibration mode change curvature for damage is investigated. The curvature index of first mode difference is applied to determine the damage location in frame.4. The step-by-step damage identification method of frame according to the static and dynamic parameters is studied. The comprehensive damage alarming index is constructed for frame based on the change ratio of first order frequency and the inter layer chord rotation. When the index value reaches the threshold, the location and extent of single or multiple damages in frame can be determined by mutation percentage index based on curvatures of both static deflection and vibration mode.