Research On The Damage Identification Of Modular Bridge Expansion Joint Based On Vibration Analysis

With the development of Highway and Bridges,the health of expansion joints of highway bridges has gradually attracted more and more attention,and more scholars have studied and analyzed its health monitoring methods.Among them,the method of structural damage identification based on vibration signal has attracted more and more scholars attention and has became a research hotspot at home and abroad due to its simple system,low cost and high precision.In this paper,under the background of health monitoring,the modular bridge numbering expansion joints is selected to make the expansion joint.Modular bridge expansion joints damage in each part is successfully identified by depth analysis of vibration signals:In this paper,under the background of health monitoring,the modular bridge expansion joint is selected to make the expansion joint.and the damage identification method of the modular bridge expansion joint based on vibration signals is studied through experiments:(1)The modular bridge expansion joint is designed and prepared by using the modular bridge expansion joint device.Four modular bridge expansion joint devices were used to simulate the temperature change of expansion joint,the damage of center beam,concrete in anchorage zone of expansion joint and the support bar.The components are damaged in multiple levels and are excited by hammer.The vibration caused by hammering is defined as random vibration.The vibration signal is collected by dynamic data acquisition instrument and acceleration sensor,and the real-time temperature is recorded by temperature sensor and multi-channel temperature inspection instrument.The natural frequency of the structure is obtained by peak method,and the instantaneous phase and Hilbert spectrum of the structure are obtained by Hilbert Huang transform.(2)The optimal placement of sensors is analyzed by the frequency distribution characteristics on the center beam,edge beam and support bar of the modular bridge expansion joint.The optimal sensor layout placements obtained from the test are the middle bottom of the center beam span,the middle side of the edge beam span and the middle bottom of the support bar span.The test analyzed the natural frequency of each part of the expansion joint,and explored the law of change of the natural frequency during the preparation of the expansion joint.The results show that the overall natural frequency of the modular bridge expansion joints after casting is shifted to high frequency,and the natural frequency increases with the increase of concrete strength during the concrete curing period,specifically 0.66 Hz/MPa.(3)The influence of temperature change on the natural frequency of the structure is studied experimentally,and the coefficient of temperature compensation coefficient of each order of vibration frequency on each structure of the modular bridge expansion joint is obtained: the second natural frequency of the center beam is 0.36Hz/℃,the first natural frequency of the edge side beam is 0.62Hz/℃,the second natural frequency is0.83Hz/℃,the third natural frequency is 1.14Hz/℃,and the first natural frequency of the beam is 0.30Hz/℃,the second natural frequency is 1.60Hz/℃,The coefficient of temperature compensation is substituted into the study of damage identification of modular bridge expansion joints.The results show that the first natural frequency of the center beam decreases by 0.40 Hz,the second natural frequency decreases by 185.40 Hz and the third natural frequency decreases by 77 Hz after complete damage.The first natural frequency of the edge beam decreases by 11.24 Hz,the second natural frequency decreases by 64.62 Hz and the third natural frequency decreases by 16.02 Hz after900mm of concrete damage in the anchorage zone.The first natural frequency decreases by 11.60 Hz,the second natural frequency decreases by 105.80 Hz and the third natural frequency decreases by 88.20 Hz after the support bar is completely damage.The damage of each part of the expansion joint can be effectively monitored by analyzing the natural frequency of the expansion joint.The damage of each part of the expansion joint can be effectively monitored by analyzing the natural frequency of the expansion joint.(4)The instantaneous phase and Hilbert spectrum of the test Specimen are obtained by Hilbert Huang transform,and the changes of instantaneous phase and Hilbert spectrum in the process of damage are analyzed.The test results show that the instantaneous phase of the concrete in anchorage zone changes slightly compared with the non-destructive state,and the energy distribution of Hilbert spectrum does not change significantly;The slope of instantaneous phase decreases by 50%,and the distribution of high energy density of Hilbert spectrum in frequency domain decreases by about 300 Hz when the center beam breaks completely;The slope of instantaneous phase decreases by about 30%,and the high energy density of Hilbert spectrum decreases by about 350 Hz as a whole when the support bar is completely damage and sensitive to damage.