https://mcej.modares.ac.ir/ Modares Civil Engineering journal en daily 1 Sun, 13 Jul 2025 00:00:00 +0330 Sun, 13 Jul 2025 00:00:00 +0330 https://mcej.modares.ac.ir/article_12729.html Steel plates are widely used in various industries, especially in civil engineering. Low cost in implementation and reduction of seismic mass are the advantage of steel shear wall system compared to other structural systems. The goal of a good design is that along with following the existing guidelines and achieving the desired seismic resistance of the structure, the structure is affordable in terms of weight and cost. Considering that according to the design, it is not possible to achieve the optimal use of the structure's capacity by force control method, the theory of uniform deformations was proposed with the assumption of a constant performance level. The subject of design based on performance increase the safety of the structure against earthquake force and design with optimal seismic performance during the useful life of the structure in seismic areas. Also, compared to the design method based on force control, it can lead to a lighter and economical design. One of the significant ways to reduce the weight and stiffness of shear walls and boundary elements connected to them is to limit the connection of filler plates to boundary elements. In this method, limiting the length of the connection reduces the force on the beams and columns, and as a result, smaller sections can be used. In this research, in order to achieve the optimal performance level, two concrete frames with steel shear wall resistant system are subjected to nonlinear analysis. Then, the initial evaluation of the behavior and the correctness of the used method are checked. After that, the effective factors in achieving uniform stress in the height of the structure will be investigated. For this purpose, by using the effect of the thickness parameter and the appropriate pattern of connection of the shear steel plate to the surrounding elements, the way of changing the performance and behavior of the structure will be investigated. For this purpose, 3- and 4-story concrete frames with steel shear wall systems were modeled using ABAQUSTM finite element software. The steel used in the steel shear wall system is ST37. First, the connection of steel shear plates to floor beams was considered and then the influence of the partial connection pattern on the seismic performance of the steel shear wall system was investigated. The modeled frames were subjected to dynamic analysis, linear and nonlinear buckling analysis, and cyclic analysis. Based on the obtained results, the property of energy dissipation in the frame with a steel shear wall system with partial connection has increased significantly. Changing the partial connection pattern led to changing the maximum in-plan relative displacement. Also, the surface of the stress distribution shows that in the partial connection, the stress concentration mainly occurred in the place of the steel shear plate connections. In addition, according to the results of cyclic analysis, considering the partial connection of the steel shear wall has led to a decrease in the average energy absorbed in the structure and an increase in its ductility. Also, changing the connection pattern has affected the average amount of absorbed energy in different loading cycles. https://mcej.modares.ac.ir/article_27807.html This study investigates the seismic vulnerability of a case of three-column reinforced concrete bridge piers subjected to near-fault (NF) and far-fault (FF) ground motions by developing comprehensive fragility curves under varying axial load ratios. Incremental Dynamic Analyses (IDA) were conducted on a representative bridge pier model considering two axial load levels (Load Factor LF = 0.05 and LF = 0.2) to assess structural responses across different seismic intensity levels. Ground motion records were classified based on their proximity to the fault, with distinct spectral characteristics used to capture the influence of pulse-like near-fault effects versus more broadband far-fault excitations.Five damage limit states were defined for the bridge pier, including Buckling of Longitudinal Reinforcement (BL), Compression Failure of Unconfined Concrete (CF-U-NC), Compression Failure of Confined Concrete (CF-C-NC), Fracture of Longitudinal Reinforcement (FL), and Low-Cycle Fatigue (LCF) of longitudinal reinforcement. IDA curves were generated, and for each limit state, seismic fragility functions representing the probability of exceeding each damage state under increasing spectral acceleration levels were generated.The results indicate that under lower axial load (LF = 0.05), the bridge pier exhibits greater spectral acceleration thresholds for damage initiation when subjected to far-fault ground motions compared to near-fault events. On average, spectral acceleration demands in FF records were 17% to 37% higher than those in NF records for various damage states. Additionally, median drift ratios were generally lower under FF motions, except in the case of FL, where the NF drift was slightly lower.For higher axial load conditions (LF = 0.2), the differences between NF and FF scenarios became more pronounced. The spectral acceleration required to reach certain damage states in FF motions was up to 31% higher compared to NF motions. Drift values also reflected this trend, with NF ground motions generally producing higher deformation demands, particularly in brittle and fatigue-prone failure modes. This shows that under increased axial loads, the vulnerability of piers to NF excitations escalates significantly.The fragility curves further confirmed this trend. At a spectral acceleration level of 0.5g and LF = 0.05, the probability of exceeding the BL state under FF ground motions was 43.5% lower than under NF motions. In more critical damage states such as CF-U-NC and LCF, this reduction reached up to 65.2% and 58.3%, respectively. At higher spectral acceleration levels (1.0g to 2.0g), this pattern of reduced exceedance probability under FF ground motions remained consistent across all damage states. Similar trends were observed at LF = 0.2, where the influence of NF ground motions in increasing fragility was more significant, especially for brittle and fatigue-related failure modes. https://mcej.modares.ac.ir/article_28786.html The increase in the production of industrial and plastic waste, especially molecular sieve waste and polyethylene terephthalate (PET), has created a serious challenge in the field of environmental waste management. On the other hand, the current management method for some of this waste is to bury it, which clearly shows that this approach is not appropriate for environmental standards. Molecular sieves, which mainly have a zeolitic and porous structure and are used in the oil, gas, and petrochemical industries for the absorption and separation of molecules, are classified as industrial waste after their efficiency decreases due to saturation of the pores. This research aimed to investigate the feasibility of simultaneously using molecular sieve waste and PET in the production of sustainable concrete and to evaluate their impact on the mechanical, physical, and environmental properties of concrete. The simultaneous use of molecular sieve and PET waste in concrete is an innovative approach in civil engineering. Due to its porous crystalline structure and high ability to absorb moisture, molecular sieve can increase density, adhesion, and reduce water absorption in concrete; however, its excessive use may lead to a decrease in compressive strength. On the other hand, using recycled PET waste as a partial replacement for natural aggregates helps reduce the density of concrete, reduce the weight of the structure, and optimize material consumption and transportation costs. Molecular sieve waste (synthesized HYG03C) after mechanical crushing and sieving was used as a partial replacement for cement in the range of 5 to 30% by weight, and PET after washing, grinding, and sieving was used as a partial replacement for sand in the range of 2 to 10% by weight. The experiments were designed using response surface methodology (RSM) and central composite design (CCD) in Design Expert software. In this design, four variable parameters were defined including cement content (200 to 400 g), molecular sieve to cement ratio, water to cement ratio (0.40 to 0.60), and PET to sand ratio. It should be noted that the amount of sand and gravel in concrete mixtures is determined to be 42 and 33 percent by weight of the total concrete, respectively. Cubic specimens with dimensions of 10×10×10 cm were made in accordance with the requirements of the Iranian Concrete Code and were subjected to porosity and compressive strength tests (Standard 1608-3). Considering the research objectives of producing sustainable concrete, the optimal composition included 393 grams of cement, 21.56% molecular sieve, 2.85% PET, and a water-to-cement ratio of 0.515, which resulted in a porosity of 4.3% and a compressive strength of 34 MPa. The results of the slump test showed that the concrete flowability in the optimal sample was 75 mm and in all samples it was within the allowable range of 50 to 100 mm. Increasing the water-cement ratio increased the slump and increasing the amount of cement, molecular sieve waste, and PET decreased the concrete flowability. Porosity and compressive strength prediction models had high accuracy and generalizability with high coefficients of determination (R² equal to 0.9978 and 0.9970, respectively) and significance level (P-value less than 0.05). This research demonstrated the effectiveness of simultaneously utilizing molecular sieve and PET waste as a sustainable method for producing concrete with improved properties and reduced environmental impacts, which has widespread application in construction projects.