Research On Action Effect And Protection For Pier Subjected To Underwater Explosion Loads

Reinforced concrete bridge piers is the main support structure of a bridge,which can cause fatal damage to the bridges when attacked by explosion ofdynamite. Therefore it is quite important to understand the failure mechanism ofexplosions acting on the bridges, which can be the useful bridge antiknock designbasis and also repairing reinforcement technology base when dealing with bridgeexplosion damage. For reinforced concrete column pier attacked by underwaterexplosion loads,using the method of numerical simulation to start study on thedamage mechanism and failure mode can be of strong practical significance andeconomic value, which also helps the establishment of antiknock performanceevaluation method of bridge structure at the same time.This article focuses onmaking equivalent numerical simulation analysis about the dynamic characteristics,damage mechanism and failure mode of reinforced concrete column pier subjectedto underwater explosion load, and carries on exploratory research on anti-explosionmeasures. This research follows several aspects below:1.Introduced and elaborating the basic physical phenomena of underwaterexplosion,the main properties of underwater explosion load and the formation andpropagation process of underwater explosion shock wave in details. Lited the Leeequation of state of dynamite and the JWL equation of state of water, and theexpression of underwater peak overpressure with the formula.2.Used the AUTODYN explicit finite element software to simulateunderwater explosion shockwave propagation process and bubble pulsationphenomenon to analyse the effects from computational grid, state equation, thecalculation area, the viscosity coefficient and water depth on computational structure,and comparing it with the empirical formula.3.Adopted impulse principle of equivalence to go on simplified analysis to theunderwater explosion loads.The shock wave of exponential decay model issimplified to a triangle pulse model, and according to the knowledge of structuralmechanics and numerical analysis, simplifying the mechanics model of cylindrical pier, the nonlinear dynamic equation structural displacement is calculated.4.Used the AOTUDYN explicit dynamic analysis software to fully consideratethe fluid-structure interaction between reinforced concrete and water,and analyzingrespondse characteristics in details of the reinforced concrete column pier underunderwater explosion loads. By comparing the proportion of distance, beamreinforcement ratio, stirrup ratio and other parameters change, the inner relationshipbetween failure modes of reinforced concrete piers and underwater shock wave wassummarized.5.According to the isolation performance of rubber materials and damage anddestruction of reinforced concrete column pier after being added flame-proof steels,exploring the anti-underwater explosion loading measures by wrapping thereinforced concrete column pier in rubber layer.Through the research,the response and failure modes of reinforced concretepier subjected to underwater shock wave is summarized and the scheme to add"anti-shock layer" on the surface of bridge piers is put forward as reference measureto assist bridge`s lower structure against the underwater explosion shock.Thereseach results can provide reference for predicting the deformation and damagemode of pier under blast loads,meanwhile,it can provide theoretical basis forantiknock design and comprehensive protection of bridge structure.