In China,the working state evaluation of piers is mainly based on the Code for Rating Existing Railway Bridges.However,the vibration amplitudes of the bridge piers under train excitations vary with train types,train s...In China,the working state evaluation of piers is mainly based on the Code for Rating Existing Railway Bridges.However,the vibration amplitudes of the bridge piers under train excitations vary with train types,train speeds,axle loads and track irregularities,so the damages of piers are difficult to quantitatively evaluate by the vibration amplitude.In this paper,the impact vibration test method(IVTM) was systemically studied through theoretical analyses,numerical simulation calculation,laboratory tests and field experiments.The soundness evaluation method based on the eigenfrequencies of bridge piers was proposed.The main work done in this dissertation is as follows.(1) The fundamental of IVTM was deduced from theory in detail and the computer software for processing the impact vibration test signal was worked out.(2) The principle of determining the eigenfrequencies of structures was confirmed by laboratory tests and some numerical examples including a cantilever pier,a simply-supported beam,a two-span bridge with a single pier,a multi-span bridge with piers and a spatial truss beam model.The fundamentals of IVTM are explained as: for velocity response signal,the dominant frequency,at which the phase is 180° or 360° and the amplitude spectrum shows a dominant peak,is the natural frequency of a structure.For displacement and acceleration response signal,the dominant frequency,at which the phase is 90° or 270° and the amplitude spectrum shows a dominant peak,is the natural frequency of a structure.On the basis of field test data,the analysis results by IVTM,ambient vibration method and modal test method were compared.The frequency identification results of the three methods agree well,which proves the correctness of the fundamental of IVTM from the aspect of engineering application.(3) When bridge piers are impacted laterally by a weight hammer,their response spectra may emerge dominant frequencies at the frequencies of the adjacent piers or beams.At this time,the frequencies can be identified according to the展开更多
文摘In China,the working state evaluation of piers is mainly based on the Code for Rating Existing Railway Bridges.However,the vibration amplitudes of the bridge piers under train excitations vary with train types,train speeds,axle loads and track irregularities,so the damages of piers are difficult to quantitatively evaluate by the vibration amplitude.In this paper,the impact vibration test method(IVTM) was systemically studied through theoretical analyses,numerical simulation calculation,laboratory tests and field experiments.The soundness evaluation method based on the eigenfrequencies of bridge piers was proposed.The main work done in this dissertation is as follows.(1) The fundamental of IVTM was deduced from theory in detail and the computer software for processing the impact vibration test signal was worked out.(2) The principle of determining the eigenfrequencies of structures was confirmed by laboratory tests and some numerical examples including a cantilever pier,a simply-supported beam,a two-span bridge with a single pier,a multi-span bridge with piers and a spatial truss beam model.The fundamentals of IVTM are explained as: for velocity response signal,the dominant frequency,at which the phase is 180° or 360° and the amplitude spectrum shows a dominant peak,is the natural frequency of a structure.For displacement and acceleration response signal,the dominant frequency,at which the phase is 90° or 270° and the amplitude spectrum shows a dominant peak,is the natural frequency of a structure.On the basis of field test data,the analysis results by IVTM,ambient vibration method and modal test method were compared.The frequency identification results of the three methods agree well,which proves the correctness of the fundamental of IVTM from the aspect of engineering application.(3) When bridge piers are impacted laterally by a weight hammer,their response spectra may emerge dominant frequencies at the frequencies of the adjacent piers or beams.At this time,the frequencies can be identified according to the
