Mohammad Hosein Talebpour

Many parameters are influenced by the diffusion of chloride on concrete in marine environments and these can affect concrete quality. In this study, the effect of water to cement ratio of 0.35, 0.40 and 0.45 on corrosion resistance and compressive strength of reinforced concrete was evaluated. Moreover, different percentages of micro silica (SiO2) including 5, 7.5 and 10% were utilized, in order to investigate the effect of pozzolanic materials on the corrosion of steel in concrete. Then cubic samples reinforced with steel bar spacing of 2.5, 5 and 7 cm from the cube surface were made and put in Caspian sea water for 5 months. During this period, corrosion potential of steel was measured by a calomel half cell (SCE). In order to finalize the evaluation of the mechanical strength of the samples, concrete pressure test was conducted and the result showed that after 40, 44 and 59 days for the bars with depth of 2.5, 5 and 7 cm, respectively and the samples prepared with water-cement ratio of 0.35, the corrosion potential was -350V versus SCE, while the compressive strength was approximately 450 kg/cm2. This result showed longer life span of this sample in comparison with other water-cement ratios. By adding micro silica to the samples up to 7.5%, the time for obtaining a corrosion potential of -350V, bars with depth of 2.5, 5 and 7 cm, was 43, 50 and 86 days, respectively, and the compressive strength of this sample was approximately 480 kg/cm2. Consequently, it is arguable that in order to achieve longer life span of corrosion and suitable compressive strength, the optimum ratio of water to cement should be 0.35 and the percentage of pozzolan SiO2 should be 7.5%.

Designing space is dramatically enlarged with optimization of structures based on ACO, regard to increasing section’s list. This problem decreases the speed of optimization in order to reach to optimum point and also increases local optimum probability, because determining suitable cross section process for each design variable in ACO depends on number of members in the list of section. Therefore, this paper by using partitioning the design space tries to decrease the probability of achieving local optimum during the process of structures optimum design by ACO and to increase the speed of convergence. In this regard, the list of section is divided to specific number of subsets inspired by meshing process in finite element. Then a member of each subset (in three case, maximum, middle and minimum of cross section) is defined as a representative of subset in a new list. Optimization process starts based on the new lit of section (global search). After specific number of repetitions, optimum design range for each variable will be determined. Afterward, variable section list is defined for each design variable related to result of previous step of process and based on subset of related variable. Finally, optimization process is continued based on the new list of section for each design variable to the end of process (local search). Proposal is studied in three cases and compared with common method in ACO and standard optimization examples in skeletal structures are used. Results show an increase in accuracy and speed of optimization according to cross section middle method (Case 2). © 2017, Budapest University of Technology and Economics. All rights reserved.