Doctor of Philosophy

dissertationAccelerated bridge construction (ABC) has been practiced in the United States because of the efficiency it offers as a bridge construction method. Prefabricated reinforced concrete components have been frequently used as part of ABC. The connections between such precast components may be subjected to large earthquake-induced deformations resulting in a considerable permanent damage. The present study investigates the seismic performance of grouted splice sleeve (GSS) connections with the connectors placed in the column, footing, or cap beam of bridge subassemblies. Quasi-static cyclic loads were used to test five half-scale precast subassemblies and two cast-in-place control specimens. Two different GSS connectors were used; the column-to-footing connections incorporated one type of GSS with the bars grouted at both ends, whereas the column-to-cap beam connections used another type where one bar was threaded into one end and the other bar was grouted into the opposite end. Experimental results show that the precast subassemblies had similar strength but lower displacement capacity compared to the control specimens. Improved seismic response was observed when the location of the connectors was changed or when debonding was applied to dowel bars adjacent to the connectors. Computational models were developed and validated with the experiments to further investigate the application of such precast connections in bridge bents with full-size configurations. Force-based beam-column elements with fiber sections were used to construct the computational models based on plastic hinge weighted integration. The modeling strategy is based on transformation of the model for the precast column with GSS connectors, to an idealized equivalent cast-in-place column with a fictitious plastic hinge length that is capable of simulating both the global and local response. Bond-slip effects as well as low-cycle fatigue were included to address the performance differences between the precast and cast-in-place alternatives. Prototype precast bridge bent models designed with GSS connections were subjected to scaled ground motion records compatible with the earthquake demand in downtown Salt Lake City. Comparing the capacity and demand levels, the GSS connection was found to be promising for applications in high-seismic areas

Impacts of mustard gas exposure on veterans mental health: A study on the role of education

Background: The mustard gas (MG) exposure can impair physical health and therefore increase the probability of the posttraumatic stress disorder (PTSD) and psychological disorders. Aim: The aim of this study was to investigate long-term effects of MG exposure on veterans′ mental health. Materials and Methods: This was a cross-sectional study. In order to assess prevalence of mental health and PTSD of 100 MG victims 25 years after the exposure to MG in Iran-Iraq conflict, the general health questionnaire (GHQ-28) and Impact of Event Scale-Revised, respectively was administered. Results: The mean (±standard deviation (SD)) age of participants was 40.63 (±5.86) years. The mean GHQ-28 (47.34) of the study group was higher compared to standardized cutoff point (23) of the Iranian community. Also, it was found that 38 participants (38%) suffer from PTSD. The results of this study showed that academic education in the PTSD group was less than that in the non-PTSD group (P=0.03). In addition, in multivariate analysis it was found that only education level of the veterans and their wives were effective on the mental health score (adjusted P=0.036 and 0.041, respectively). The mean score of depression and psychosocial activity subscale in patients at higher education level was lower than patients at lower education level (P<0.05). Conclusion: This study found that sulfur mustard (SM) exposure can be effect on mental health even 25 years after exposure. Therefore, the psychological state should be more considered in chemical injured veterans and it is important that providing more mental health centers for this community