The increasing occurrence of vehicle-pier collision accidents has significant influences on the safety of bridge structures. In order to study the impact behavior of bridge piers, a vehicle-double-pier collision numerical model was developed by LS-DYNA. Nonlinear material constitutive laws considering the strain-rate effect were used. The reliability of numerical analyses was validated. Parametric studies were carried out to investigate the effects of impact velocity, impact mass, and concrete and steel strength on the impact behaviors of piers and the impact forces. The relationship between failure modes of the impacted piers and impact energy was analyzed. Based on the numerical analysis results, the current impact design provisions of AASHTO, Eurocode, and JTG D60 were found to be unconservative, which could result in that piers designed with the current standard codes were vulnerable to the large impact energy. The recommended value of equivalent static force in the current standards is unreasonable.
In this article, a method was proposed to assess damage of the bridge piers subjected to vehicle collision with the help of the detailed numerical model. Nonlinear material constitutive laws considering the strain rate effect were adopted in the models. Validation was performed by comparing the numerical results with the available experimental results in terms of impact force, displacement, and failure pattern. Based on the validated numerical models, the failure process and different damage levels of the piers under impacts were analyzed. The results showed a four-stage failure process as well as four damage levels with the increase of the vehicle impact force. According to the numerical study, a new damage index and the corresponding assessment criterion were defined to assess damage of the impacted pier. A vehicle impact force equation and a half-sine impact impulse were developed for damage index.
Grout defects always exist in sleeves of precast structures, but studies on grout defect identification are rarely performed. This article proposes a combination method of dynamic excitation technique and wavelet packet analysis for sleeve defect identification in the precast structure. Hammer excitation on a 1/2-scaled two-floor precast concrete frame structure with column rebar splicing by grout sleeves is conducted to collect column acceleration responses. Moreover, the corresponding energy spectrum is obtained by the wavelet packet analysis. Furthermore, three defect identification indices, that is, percentage of energy transfer, energy ratio variation deviation, and energy spectrum average deviation, are calculated and compared. Robustness analysis of the energy ratio variation deviation is carried out by adding white noise in the original acceleration response signals. The results show that (1) the percentage of energy transfer, the energy ratio variation deviation, and the energy spectrum average deviation are positively correlated with the grout defect degree where the energy ratio variation deviation is more sensitive in the identification of defects; (2) the energy ratio variation deviation robustness of the original signal with the inputted multiplicative white Gaussian noises is better than that with the inputted additive white Gaussian noise; and (3) the proposed defect identification method can characterize the sleeve grout defect degree in column.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.