Application Of Refined Multiscale Modeling Method In Static And Dynamic Analysis Of Bridge Beams

The failure of bridge structures usually occurs from within the material of the structure,then gradually extends to the outside of the structure,ultimately leading to the failure of the entire structure.However,in the process of using numerical analysis methods to study the failure of large structures,computer performance issues prevent overly precise modeling and analysis of bridge structures.The multi-scale modeling method can effectively improve the computational efficiency of static and dynamic analysis of bridge beams,but the commonly used multi-scale modeling methods only consider multi-scale modeling at the bridge structure level.There is little research on multi-scale modeling of bridge structures at the material composition level,and material damage is often the key to structural failure.To address this issue,a multi-scale bridge model is established for analysis,and the concrete materials in the bridge are modeled at a mesoscale and subjected to tensile and compressive numerical simulations.Then,a mesoscale concrete simply supported beam model is established to simulate the damage process of the concrete simply supported beam.Finally,a physical bridge model is established,and through static analysis,the stress concentration and vulnerable parts of the bridge are identified.Based on these parts,a multi-scale bridge model is established,and the material of the beam elements in the model is assigned using two methods.Two different multi-scale models are established at the material composition level,and modal and dynamic analysis are performed on the model,Identify the differences between the natural frequencies of the two models and the physical model,as well as the differences between the simulation results of the two models and the physical model under seismic loads,in order to provide reference for the damage research of multi-scale bridges.The main research content and conclusions of this article are as follows:(1)Establish a micromechanical model of concrete and conduct numerical simulations of the model under tension and compression.The simulation results indicate that threedimensional mesoscopic concrete can effectively simulate the mechanical failure process of concrete,and its stress-strain relationship has a small error compared to the results of homogeneous concrete,meeting the research requirements.(2)Establish a solid homogeneous concrete simply supported beam model and a multiscale mesoscale concrete simply supported beam model,and conduct three-point bending numerical simulation on both models to study the difference between the crack trend of the multi-scale model and the solid model during the stress cracking process.The simulation results indicate that the multi-scale mesoscopic concrete simply supported beam model can better simulate the fracture and failure of the simply supported beam during the stress process compared to the homogeneous simply supported beam model,and its crack propagation is also more realistic and in line with the actual situation.(3)Establish a physical bridge model and conduct static analysis on it,identify the stress concentration areas of the bridge,establish a multi-scale bridge model based on these areas,and conduct multi-scale modeling again at the structural material composition level of the multiscale model.Directly assign homogeneous material properties to reinforced concrete on the beam element and add steel bars inside the beam element,respectively,Analyze the differences between the natural frequencies of multi-scale models composed of two different materials and the physical model,as well as the differences between the analysis results under seismic loads and the physical model.The simulation results indicate that the simulation results of the multiscale bridge model with added steel bars inside the beam element are closer to the simulation results of the physical model,and can better simulate the dynamic response results of the bridge.