فهرست مطالب
 Volume:4 Issue: 4, Autumn 2022
 تاریخ انتشار: 1401/09/10
 تعداد عناوین: 5

Pages 115In recent years, isolated systems are noted for preserving structures against harmful effects of earthquakes. Across all types of friction isolators, the latest one, triple concave friction pendulum, is transcending for its hardening behavior in high risk states. Isolated systems dissipate energy of earthquakes by increasing period and damping. In this paper, the behavior of structures (3, 6, and 9 stories) mounted on TCFP subjected to nearfield and farfield earthquakes are studied using fragility curves concept. Results indicate by increasing the effective period of TCFP decreases the median acceleration of collapse damage state (Sa50% collapse). For better understanding the behavior of TCFP isolators with different effective periods, collapse margin ratio is also used, that demonstrates isolator with higher period reduces collapse risk. Comparing Sa50% collapse in structure subjected to nearfield and farfield earthquakes shows that the structure subjected to near field earthquake is less than the far field one.Keywords: Far field earthquakes, Near field earthquakes, seismic isolator, TCFP isolator, IDA, Fragility curve

Pages 1625One of the issues that strongly affect the properties of selfcompacting concrete is the role of fillers. The effect of the type and performance of fillers on the properties of concrete in a fresh and hardened state is important. In this research, the effect of using iron ore powder as filler on the rheological and mechanical properties of selfcompacting concrete has been investigated. To evaluate the rheological properties of selfcompacting concrete, slump flow and T50 tests were performed on samples with different percentages of iron ore powder (0 to 80%). The mechanical properties of the samples were also measured by performing concrete compressive strength tests at the ages of 3, 7, 28, and 90 days. The results of the tests performed on the samples show that increasing the amount of iron ore powder, increases the unit weight of the selfcompacting concrete and decreases the slump flow by up to 30%. In addition, the results of the compressive strength test show that, in general, with the increase in the amount of iron ore powder, the compressive strength of the samples has decreased between 223%. Based on the results of this research, an optimal amount for iron ore powder replacement cannot be reported.Keywords: Iron ore powder, Heavy concrete, Concrete fresh properties, Concrete hardened properties

Pages 2637Most of the buildings are made of concrete; hence, the consumption of cement, freshwater, river sand, and coarse aggregate has increased, leading to environmental pollution and natural source depletion. The percentage of the ocean on the Earth’s surface is 71%. Hence seawater is available in abundance. If the freshwater is replaced by seawater, there would be sustainable development in the construction industry. In this study influence of the composition of Portland cement  fuel ash  metakaolin – silica fume binders partially mixed with seawater on the strength and durability of the concrete have been investigated. The percentage of replacement of freshwater by seawater was 5%, 10%, 15%, 20%, 25%, and 100%. The effects of concrete mixing with seawater on compressive strength and its durability were studied.Keywords: Concrete, Fly ash, Metakaolin, Silica fumes, Sea water

Pages 3854In this paper, a regression model is formed to make the foretelling of the compressive strengths and their compactible mix ratios for a limecement concrete as effective and perfect as possible using the Scheffe’s regression theory. Twenty four selected mix ratios were studied experimentally for their compressive strengths at 28 days after curing in water at room temperature. Compressive strengths obtained stretched from 15.12N/mm2 to 24.58N/mm2. Fifteen of the readings obtained were used to develop the regression model while nine mix proportions were adopted for validation of the developed model. The model was tested for reliability at 95 % level of confidence using the Fstatistic test and found to be adequate as the calculated Fvalue (1.918) was less than the critical Fvalue (3.438). A MATLAB based computer program was written based on the regression model using visual basic 6.0 software to optimize the compressive strength of the lime cement concrete and also speed up the process of selecting the corresponding mix ratios. The peak value of compressive strength predictable by the model is 24.460336 N/mm2 and the corresponding mix ratio is 0.586:0.841:0.159:2.42:4.84 (water: cement: lime: sand: granite chippings). MATLAB program developed is interactive, quick and is suitable for application in optimum concrete mixture proportioning.Keywords: Scheffe’s regression theory, Compressive strength, Limecement concrete, Mix ratios

Pages 5570In this article, the control over the inlet sediment into the lateral intakes incorporating parallel skimming walls is assessed using harmony search algorithm. The skimming walls are known as the structures constructed in front of the lateral intake and consisted of two plates, one of them is in oblique form and the other one is parallel to the flow. The parallel skimming walls direct the sediments toward the downstream of the main channel by forming a rotational flow, as a result the entry of sediments into the lateral intake is prevented. Using the experimental data obtained in the laboratory and Buckingham’s method, the dimensionless parameters were obtained. The parameters were nonlinearly transformed into the relations, in such a way that using harmony search algorithm almost 20,000 optimal points were obtained. In the present research, the relations between the dimensionless parameters were yielded by harmony search algorithm. The results indicate that the optimized maximum and minimum and mean values of CS1 for governing equations is equal to 17%, 31% and 29%, respectively, relative to the observational maximum, minimum and mean values of CS1. For governing equation, the optimized maximum, minimum and mean values of CS2 exhibited error values of 11%, 4% and 31% relative to the observational maximum, minimum and mean value of CS2.Keywords: Lateral Intake, Skimming Wall, Sediment Control, harmony search algorithm