Research On Finite Element Model Of The Newly-built Shuidong Bridge Based On Construction Control And Load Test

The construction of national transportation network has developed rapidly since 21 st century.Bridges have become the key of unimpeded roads,as a kind of architecture that across the rivers,mountains and rough terrains.The continuous rigid frame bridge is most widely adopted among various bridges for its rational force form,constructing convenience and the low cost of maintenance.The excessive midspan sag and cracks in box girder always happen by the increased number of continuous rigid frame bridges.The regular inspection and long-term online health monitoring for these bridges are essential while the bridges are working as an important part of the traffic lifeline engineering.In this case,an accurate finite element model of the finished bridge is necessary for regular inspection and long-term health monitoring.However,due to the ideal assumptions and simplification from the finite element model established during the bridges construction,there is a deviation between the true structure and the model.In this case,in order to minimize the error,it's necessary to update the initial finite element model of the bridge,so that this modified accurate finite element model could be used for the regular inspection,even the long-term health monitoring of the bridge during its working.Construction supervision of the whole process of the newly-built Shuidong bridge was carried out in this article.The initial Midas/Civil finite element model was established and analyzed,where the loads and stages of the bridge's construction were taken into consideration.The deformation and internal force of the main girder were obtained during each construction stage,which provide guidance for the monitoring in site construction.The vertical deflection and the stress variation presented by the embedded stress sensor were strictly controlled during the construction.If there is any problem,feedback immediately,and then the plan would be rescheduled.So,the real structure state could be very close to the design state at the end of the bridge construction based on the deformation and stress monitoring.The load test was applied to the newly-built Shuidong bridge after the main span closure and the bridge decking construction were finished.According to the initial finite element model which is based on the design drawing of construction,and relevant specification,the load test program was determined by calculations.And then,the load test was successfully completed.The deflection and stress of controlling section were detected accurately under each loading condition.The load-carrying capacity and stiffness were evaluated by comparing the test data with the calculation data.At the meantime,the effect of the construction monitoring was also examined.After the load test,the BP neural network was applied to the model updating of the initial finite element model of the newly-built Shuidong bridge,using the deflection data obtained by loading test.The training samples were determined based on uniform design concept for neural network training,to ensure that the learning efficiency is proved.A reliable BP neural network could be verified by its generalization.Using the updated parameter to establish the finite element model of the newly-built Shuidong bridge again,the results proved that the deflections obtained by calculation agree well with those obtained by exam under each test condition,and the updated finite element model based on the measured deflection data is feasible and effective.Furthermore,the 0# block local finite element model was established based on the updated parameters using ANSYS software.The stress was calculated and analyzed in the construction phase and completed bridge phase based on the load extracted from the whole finite element model.The stress obtained by calculation of 0# block was compared with that obtained by test based on the condition of the pier-top maximum negative moment.The results indicate that the updated model is reliable.The updated finite element model of the newly-built Shuidong bridge could be used to simulate the structure state of the bridge when it is under practical working condition after its construction is finished.