Efficient Analysis Method Of Bridge Structures Subjected To Vessel Impacts Based On Fiber Element

With the gradual rise of the Chinese economy,the transportation industry is developing rapidly,and the speed of building bridges is also getting faster and fa ster.The increasing number of bridges,to a certain extent,has become a barrier to ships.For dynamic analysis of bridge under vessel impacts in navigable waters,the equivalent static method in current codes is very simple to be employed in practical engineering.However,it fails to consider the dynamic interaction between vessel and structure in nature.Whether using the equivalent static method in domestic and foreign codes or the approach using general-purpose nonlinear contact-impact finite element,there are great limitations.Therefore,the purpose of this paper is to establish an efficient and accurate analysis method of bridge under vessel impacts according to the characteristics of dynamic interaction between vessel and structure.This method can clarify the dynamic response of the structure in the process of vessel-bridge collision and provide guidance for the design of the bridge.(1)For the first category of vessels in AASHTO(Barge),based on an interaction model on nonlinea macro-element,the global and local characteristics of the P-a curve of bow when the barge collides with square piers and round piers were studied.Based on the principle of energy equivalence,a simplified P-a curve of barge bow considering the effect of strain rate and pier width was proposed.The displacement of the structure was calculated by using the CVIA method,and the influence of different parameters on the P-a curve was discussed from the point of view of the shock spectrum.The results show that the simplified P-a curve of the bow is in good agreement with the actual P-a curve in the shock spectrum,which verifies the rationality of the proposed simplified P-a curve;The simplified P-a curve fitted by the envelope value is used to realize the complete envelope of the shock spectrum results under all specific events(including the common impact velocity and pier width).With reference to the concept of design spectrum in seismic research,it can be used as a design spectrum in the research of vessel-bridge collision.(2)Based on the University of Toronto Simulation Framework(UT-SIM)and the method of interaction model on nonlinea macro-element,an analysis of vessel-bridge collision method of fiber beam element based on Open Sees-Matlab hybrid simulation technology was proposed.First of all,the simulation of the impact object was realized in Open Sees,and a method which can describe the interaction between the impact object(Barge)and structure was established by using only compressed GAP spring and zer o-length element.The impact example model of Open Sees-Matlab hybrid simulation was established to verify the possibility of hybrid simulation technology used in vessel-bridge collision.Secondly,based on the interaction characteristics of the vessel-bridge collision,the Matlab substructure program was used to simulate the non-linear macroelement of the bow in the vessel-bridge collision,and combined with the Open Sees integrated structure considering the elastic pier of the pile foundation for hybrid simulation analysis.The structure peak displacement error of the LS-DYNA refined finite element model and this method are within 10%,which verifies the effectiveness and rationality of this method.Compared with the refined finite element collision model,the analysis method of vessel-bridge collision of fiber beam element based on Open Sees-Matlab hybrid simulation technology can greatly improve the calculation efficiency.(3)In order to study the performance of axially-loaded UHPC column under impact load,drop-hammer impact tests on UHPC columns were carried out.The test variable was axial force.The test results show that the impact resistance of the axially-loaded UHPC column is greatly superior to that of the conventional RC column.The total energy consumption under repeated impact is much higher than that of conventional RC column.It shows that UHPC has great potential to improve the impact resistance of columns.A simplified two-degree-of-freedom analysis method based on nonlinear fiber finite element was established.A simplified analysis method based on fiber-based nonlinear finite elements and two-degree-of-freedom mass-spring-damping systems was proposed to evaluate the impact response o f a column.The developed simplified analysis method was validated by comparing the numerical results with the experimental displacements and impact forces.It also shows that the modified Concrete02 constitutive in Open Sees can be used to simulate UHPC ma terials.(4)Based on Open Sees,a nonlinear and efficient dynamic analysis method for column was established.Comparison with existing experiments shows that this method can accurately simulate the nonlinear behavior of the column under impact load(mainly bending failure)and obtain a better response of structure.Combined with nonlinear and efficient dynamic analysis method for column and Open Sees-Matlab hybrid simulation technology,a nonlinear efficient dynamic analysis method for vessel-collision of UHPC column bridge was established.Using this method,the structural response of a typical four-span continuous beam bridge with UHPC column was studied.Finally,this method is used to analyze and compare the static and dynamic structural response of the bridge structure.The results show that the result of dynamic analysis is much larger than that of static analysis,and the dynamic effect of bridge structure under the vessel impact has a significant influence on the response.Compared with the non-linear contact finite element technology with long calculation time for modeling complex calculations,this method only needs 30-40 minutes,can save at least 40-60 hours of calculation time,and greatly improves the calculation efficiency.It can be easily and efficiently applied to actual projects.