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One of the influential factors in estimating the service life of reinforced concrete bridges (RCB) is determining the long-term seismic performance of these structures. Corrosion due to chloride ion diffusion leads to the destruction of critical members of the RCB during the useful life of the structure. So, the long-term seismic performance of the bridge deteriorates as a result. It is essential to study the effect of corrosion deterioration on the long-term seismic performance of bridges in the southern regions of Iran, near the coasts of the Persian Gulf and the Oman Sea, because of the seismicity of the region and high corrosion rate of reinforced concrete (RC) members is the result of environmental conditions. In order to investigate this issue, considering studies about environmental conditions of southern Iran, the onset time of corrosion in the columns, as seismic critical members of the bridge, was determined. Based on that, the corrosion's effect on characteristics of RC at specific time points during the bridge's useful life (0, 15, 30, 45, 60, 75 and 90 years) have been calculated. The effects of corrosion include deterioration of the core and cover concrete properties, steel bar and the connection between concrete and steel bar. In the next step, at each time point, according to the modified stress-strain relationships, the moment-curvature analysis of the bridge pier was done, and the properties of the plastic hinge were determined. Finally, based on the obtained data about plastic hinge characteristics at each time point, overload analysis of the bridge was performed in both longitudinal and transverse directions. Then the capacity curves of RCB were compared at the mentioned time-points. The results show that the capacity of the bridge deteriorates over time due to corrosion. Therefore, a proposal to increase the value of base shear design has been made to ensure the long-term seismic performance of RCB in corrosive environments.

Design coordination and clash detection are the most common and appreciated applications of three-dimensional modeling (3D modeling). In some projects, millions of clashes are detected including a large number of irrelevant clashes. The purpose of this research is to determine the priority of resolving clashes before the construction phase. In this research, the results of Autodesk Navisworks have been used to improve the process of clash detection. Also, this study attempts to use the fuzzy-AHP for weighting criteria and then, by presenting a relationship, to provide a basis to prioritizing clashes for their resolution and, finally, for identifying irrelevant clashes. This method has been tested on a real project, and the comparison of the expert opinions and the proposed method showed that applying the proposed relationship can identify important and irrelevant clashes. Practical application If clashes are not carefully detected in the design stage, project management components face a serious challenge. In this study, using the weight of clash elements and the degree of penetration of clash elements into each other, a logical and practical relationship is presented that improves the process of clash detection.

The corrosion of reinforcements in the tidal zone leads to significant damage to offshore concrete piers. To overcome such damages, the quality of concrete and its mechanical properties should be improved. The aim of the present study is to identify and evaluate the causes and extent of corrosion observed in piers P3 & P4 in Imam Khomeini petrochemical. The concrete reinforced by microsilica and the ECC concrete are used to prevent corrosion. Some tests were conducted to determine the conditions of concrete piers in terms of reinforcement corrosion. Then, a reinforcement corrosion intensity test using Potentiostat involving a placement process was used, where the water-to-cement ratio was 38%; superplasticizers was 4%; and microsilica was 10% and 15%. The microsilica can serve as an alternative to the consumed cement and was measured according to the ASTM standards; Besides, it was exposed to aggressive conditions at different periods, and a concrete compressive strength test was performed. The results show that the compressive strength of concrete with microsilica 15% is nearly 25% higher than that of ECC, while for the control specimen, this value is about 42%. Regarding the corrosion intensity, the concrete with microsilica 15% has the minimum value compare to all three other samples. It is recommended to use this type of concrete to overcome the corrosion problem in piers P3 & P4 in Imam Khomeini petrochemical.