Fatigue Performance of Orthotropic Steel Decks in Super-Wide Steel Box Girder Considering Transverse Distribution of Vehicle Load

This study presents an investigation on the fatigue analysis of four types of details on orthotropic steel decks(OSDs)for a cable-stayed super-wide steel box girder bridge based on finite-element analysis(FEA)with vehicle transverse distribution model(VTDM).A high-fidelity 3D FE model verified by the static load test is established to satisfy the fatigue analysis accuracy.The stress behavior of super-wide steel box girders under the vehicle load at different lane locations is investigated.Then,considering the effect of VTDM,the fatigue life analysis of four typical details is performed using the Miner cumulative damage rule.The results show that the vehicle transverse location has a great influence on the stress behavior of details with sharp influence surface,and the stress ranges in the outermost lane are larger than those in other lanes,indicating that the details of OSD in the outermost lane are prone to fatigue.The fatigue life analysis indicates that the diaphragm cutout is more prone to fatigue than other details,which should be carefully treated in bridge maintenance.

Research on seasonal correlation of wavelet packet energy spectrum and temperature of Runyang Suspension Bridge

In order to establish an environmental-condition-normalized structural damage alarming method,the seasonal correlation analysis of wavelet packet energy spectrum(WPES)and temperature of Runyang Suspension Bridge is performed by means of the 236-day health monitoring data.The analysis results reveal that the measured WPES has remarkable seasonal correlation with the environmental tempera-ture.The seasonal change of environmental temperature accounts for the variation of the damage alarming parameter Ip of the dominant frequency bands with an averaged variance of 200%.The statis-tical modeling technique using a 6th-order polynomial is adopted to formulate the correlation between the WPES and temperature,on the basis of which the abnormal changes of measured damage alarming parameter Ip are detected using the mean value control chart.It is found that the proposed method can effectively eliminate temperature complications from the time series of WPES and exhibit good capa-bility for detecting the damage-induced 10% variances of the damage alarming parameter Ip.And the proposed WPES-based method is superior the modal frequency and hence is more suitable for online real-time damage alarming for long-span bridges.

Assessment of bridge expansion joints using long-term displacement measurement under changing environmental conditions

This paper addresses the problem of condition assessment of bridge expansion joints using long-term measurement data under changing environmental conditions.The effects of temperature,traffic loading and wind on the expansion joint displacements are analyzed and interpreted,which reveal that measured displacements are observed to increase with an increase in temperature and to decrease with increased traffic loading,while the correlation between displacement and wind speed is very weak.Two regression models are developed to simulate the varying displacements under the changes in temperature and traffic loadings.Based on these models,the effects of the environmental conditions are removed to obtain the normalized displacement.Statistical process control using mean value control charts is further used to detect damage to the bridge expansion joints.The results reveal that the proposed method had a good capability for detecting the damage-induced 1.0%variances of the annual changes in the expansion joint displacements.