This paper presents a structural vulnerability analysis method based on the theory of plastic limit analysis.By applying the mechanism generation method,the ultimate loading factor and the corresponding failure mode of a structural system can be obtained.The ultimate loading factor was then used to measure the performance of a structural system.The variation of this factor to different damage scenarios due to vehicle collision was investigated.To illustrate the proposed method,two cases study on statically determinate and statically indeterminate truss bridge were performed.The results of the case study showed that the susceptibility of structure performance to local damage scenarios not only depends on the location but also the severity of the damage scenarios.Based on this analysis,structural capacity can be evaluated and structural management and maintenance strategy can be made more efficiently.