| As the throat of national transportation,bridge plays an important role and position in national economy and military transportation.It may suffer from missile strike,terrorist explosion and accidental explosion during its service period.Prestressed continuous box girder bridge,which suffer great damage risk under explosion,is one of the important structural systems of Bridges.Aiming at the problem of damage assessment of prestressed continuous box girder bridge,the damage pattern and process of prestressed continuous box girder bridge were studied by means of experiment and numerical simulation.The damage assessment of prestressed continuous box girder bridge was studied by means of numerical simulation and theoretical calculation.The main contents are as follows:(1)A design method of prestressed continuous box girder bridge segment model under explosion condition was proposed,and contact explosion test of prestressed continuous box girder bridge segment model was carried out.Based on the explosive equivalent of the explosion test,the propagation distance of shock wave attenuating to elastic wave was estimated by empirical formula,and the segment length required by the segment model was designed.Based on the stress calculation theory of box girder bridge,the stress state of segment model was basically the same as that of the original bridge by adjusting the arrangement of additional prestressed steel strands.The contact explosion test of large equivalent bridge deck 4m away from the bridge pier was carried out.The damage mode and damage range of prestressed continuous box girder bridge under contact explosion condition were obtained by measuring the size of local explosion pit and the overall deformation of the bridge.(2)The numerical simulation of prestressed continuous box girder bridge segment model was carried out,the damage mechanism was analyzed,and the influencing factors of residual bearing capacity of section were studied.The numerical model of prestressed continuous box girder bridge segment model was established by using separate modeling method.The dynamic damage process of box girder bridge in static loading stage,explosion loading stage and whole collapse stage was reproduced by three-stage numerical simulation method,and the damage mechanism of roof,bottom plate,web,ordinary steel bar and prestressed steel bar under contact explosion and implosion condition was analyzed.By comparing the damage effects of box girder bridge under 8simulated conditions,the effects of explosive equivalent,explosion location,initiation mode and their interaction on the residual bearing capacity of section were analyzed.(3)Research on damage assessment of prestressed continuous box girder Bridges was carried out,and a damage assessment method of prestressed continuous box girder Bridges was proposed.According to the analysis results of vulnerability of box girder bridge in numerical simulation,the corresponding relationship between explosive equivalent and damage degree of box girder bridge was further studied.Based on the local damage data provided by numerical results and through calculating the residual bearing capacity of the section after explosion,the empirical formula for damage assessment of the explosive equivalent and prestressed continuous box girder bridge was obtained.Compared with the numerical results,the damage degree of the box girder bridge calculated by the empirical formula is basically consistent with the numerical results. |
