mohammadreza javaheri-tafti

This investigation aims at studying the energy method in calculating the exceedance probability of structures under seismic loads in reinforced concrete frames and its comparison with the conventional approach based on maximum story drift in structures. To do so, two reinforced concrete moment resisting frames with six and ten stories are designed based on the Iranian seismic code of practice and modeled nonlinearly with Perform software. Twenty near-fault earthquake records have been utilized to conduct the fragility analysis. The Incremental Dynamic Analysis (IDA) approach is used for the analysis and the IDA curves obtained from two methods are extracted and compared. The IDA curves resulted from the energy method provide this ability to calculate the elastic and plastic behavior zone and the instability point of the structure accurately. The output of the fragility analysis in reinforced concrete frames illustrates that the energy method can be utilized as an applicable approach in estimating the seismic fragility of the structures. The exceedance probability calculated in this approach is lower than the conventional method. The conventional method provides more conservative results in comparison to the energy method.

The hydraulic design of diversion dams is traditionally very complicated and time-consuming and it is necessary for the designer to change the used assumptions several times in order to achieve a stable design with a suitable concreting volume. In today's advanced and competitive world, due to the lack of raw materials and the need for better efficiency, design engineers are forced to design more economically and optimally. Therefore, it is necessary to reduce the cost of concrete in the design of these dams and at the same time ensure the stability of the dam. In this research, the application of a meta-heuristic algorithm has been investigated in order to minimize the weight function of the diversion dam and, as a result, the cost of concreting the dam at the same time as providing the functions related to the dam's stability.

The algorithm used in this research is the particle swarm optimization (PSO) algorithm. According to the nature of this algorithm and the research problem, it is necessary to make changes in the execution steps of the algorithm. Therefore, by making changes in the PSO algorithm, this algorithm was developed to solve the dam weight optimization problem by considering the limitations of this problem. These changes include controlling the speed of searcher particles and normalizing the position of particles in the feasible space of the problem. The diversion dam studied in this research is the Nazelian dam located in Kermanshah province. The decision variables in the optimization problem include the height of the upstream and downstream dam cutoff walls, the length and thickness of the concrete apron at upstream and the thickness of the detention pond. In order to optimize these dimensions, by performing sensitivity analysis, the parameters with the greatest impact on the performance of the algorithm were identified.

In this research, based on the results of the sensitivity measurement of the number of particles or the population size of the PSO algorithm, the number of 20 particles was chosen for the size of the population of particles. According to the convergence graph of the PSO algorithm in different executions, to ensure finding the optimal global response and avoid additional calculations and evaluations, the number of iterations of the algorithm was equal to 1000. According to the best implementation of the PSO algorithm, the weight of the studied dam in the optimal response of this algorithm was equal to 52.80 tons per unit of dam width. The best answer to the problem of optimal design of the dam has dimensions of 7.6 meters for the length of the upstream apron, 0.6 meters for the thickness of the upstream apron, 0.6 meters for the thickness of the detention pond, 1 meter for the height of the upstream cutoff and 1.1 meters for the height of the downstream cutoff.

In general, the result of the present research indicates the optimal performance and speed of the PSO algorithm in finding the optimal solution to the problem of designing a diversion dam with the least weight of the dam along with the observance of stability indicators. Using this algorithm in order to find the optimal parameters for the design of diversion dams can provide useful information to the executives to provide the best and most optimal design with minimum cost and very little time while observing the safety factors of the stability of diversion dams. The program developed in this research provides the necessary and sufficient conditions for the optimal design of the cross-section of diversion dams and is reliable in terms of general and practical validity, but it has limitations. Among the limitations of this method is that the cross-section obtained based on the code developed in this study must be adjusted later for different stress criteria (using the finite element method) and be tested for specific conditions that are different in each project (earthquake, flood, sedimentation, etc.).

In recent years, the steel shear wall system has been used integrally in steel frames, but the appropriateness of using this system in prefabricated concrete frames is in the development stage. Little research has been done on the behavior of prefabricated concrete frames reinforced with steel shear walls. This article deals with the laboratory investigation of steel shear walls connected to precast concrete frames by bolts and nuts. Three different samples were subjected to reciprocating quasi-static loading according to ACI-374 regulations. All laboratory models include a one-story prefabricated concrete frame with hinged connection of the boundary members for corners of the frame and also a screw connection of the boundary members to the filler plate. In the first laboratory sample, a carbon steel plate was used and in the second laboratory sample, a galvanized plate was used as a steel shear wall, while the third laboratory sample did not have a steel shear wall and only a prefabricated concrete frame was used. The results show that contrary to the initial assumption in the design of the beam-to-column connection in the laboratory samples, they behaved semi-rigidly and in both samples with carbon steel and galvanized steel plates, the stiffness increased 4 times compared to the prefabricated concrete frame with the semi-rigid connection. The resistance of the final steel shear wall with carbon steel plate and galvanized plate has increased by 337% and 591%, respectively, compared to the prefabricated concrete frame. Using a steel shear wall system can significantly improve the stiffness and strength of the structure. Also, the results showed that the prefabricated concrete frame is in an elastic state until the end of loading and energy is absorbed by steel plates. Finally, the investigations showed that using steel plates in prefabricated concrete frames increases energy absorption significantly.

This study seeks to integrate steel shear walls with precast concrete systems into stable and resistant structures against lateral loads. Until now, no laboratory research has been published due to the very limited number of tests performed on the precast concrete system with steel shear wall, ductility factor, additional strength and behavior as well as the energy absorption of this integrated system compared to the precast concrete system without steel shear wall. For this purpose, two steel shear wall samples made of black plate and galvanized plate (energy absorber) have been tested. Also, a sample of precast concrete frame without steel shear wall has been tested to compare the mentioned coefficients. The results of investigations show that steel shear walls significantly increase the stiffness, ultimate strength and behavioral performance of precast concrete buildings.

The lateral behavior of cold-formed steel shear wall is dependent on several factors including the type of sheathing used. However, only a limited number of sheathing types have been studied using specific installation method. In this study, due to the high demands of builders to use local materials for sheathing light steel frames, which, in addition to being abundant and easy to obtain, can also create a variety of designs such as stone or brick to match the facade of existent parts of the building, two full-scale samples of cold-formed steel shear walls in dimensions of 1.2×2.4 meters sheathed by porcelain ceramic with different configurations have tested under combined constant gravity loading and standard cyclic lateral loading regime. After calculation of ductility and response factors by using of specimens tests results, The seismic effect of the sheathing rectangular pieces orient, which can be installed in either horizontal or vertical strips, is investigated. The study also evaluates the failure modes of the systems. The results of the tests show that porcelain sheathing pieces installation in vertical strips instead of horizontal strips causes a decrease of approximately 50% in Energy Dissipation and 18% in ultimate lateral resistance without effect on seismic response modification factor, R.

Concrete is the most used construction material in the world. Today, there are various concretes with different applications in the industry. One of the types of concrete is fiber concrete. In this study, several concrete samples were made with steel, glass and polypropylene fibers and the effect of the volume and weight percentages of each of the fibers in improving the compressive strength of the samples at temperatures Different has been checked. In order to check the results and the possibility of comparing it with the behavior of normal concrete, a type of concrete without fibers was also made using common materials and similar tests were performed on it. Based on the investigations, the results showed that the concrete samples with steel fibers tolerated higher temperature levels and had higher resistance compared to other samples. In the samples, by adding 0.25% and 0.5% by volume of steel fibers to concrete, respectively, the compressive strength of the sample at high temperatures was improved. The strength of concrete samples with 3400 Kg/m was slightly decreased by increasing the percentage of fibers from 0.5% to 0.75%. The compressive strength of concrete containing steel fibers is 20% higher than that of concrete containing propylene fibers.

One of the causes of prosperity and success in the construction industry and one of the most common debonding is the debonding of the concrete cover and the separation of the concrete surface and the reinforcement plate. This paper evaluated the beams in the experiments due to an external force applied perpendicular to the longitudinal axis. The five reinforced concrete beams test specimen dimensions were 200×140×1300 mm, with rebar 10 for the bottom and 6 for the top, rebar 8 for the girders, and the concrete grade was considered 350. The final strength of 28 days with GFRP fibers in two layers, three classic layers, two layers, and three U-shaped layers are subjected to a four-point bending test. A control specimen was used for evaluation. The experimental results showed that the three U-shaped GFRP layers performed better than the other specimens and performed better in the biaxial bending test. The three U-shaped GFRP layers sheet had the most significant effect on flexural reinforcement and prevention of debonding compared to the classic U-shaped two-layer, three-layer, and two-layer GFRP sheets. In addition, Two U-shaped layers have more resistance to external load pressure than a U-shaped layer and have a more significant impact.

The lateral bracing frames are one of the common and earthquake-resistant systems. These frames were originally used to withstand wind forces, and were later developed to withstand lateral forces caused by earthquakes. One of the most important lateral bracing systems are eccentric braced frames (EBF). In this investigation, the behavior of eccentrically braced frames with Interchangeable link beam has been studied. Unlike other past researches, in addition to paying attention to the proper function of the fuse in the structure, the researchers have put the simplicity of its construction and easy replacement on the agenda. In this system, the link beam is connected to the out-of-link beam using a pin connection, so that it can be easily interchanged while exhibiting a fully shear behavior. In order to achieve the desired results, eccentric frame design has been done by ETABS software and analysis by ABAQUS software. The results of the research show that the use of pinned link beam, in addition to its impressive performance against lateral force, due to its simple interchangeability, the reconstruction time of the structure after the earthquake has been greatly reduced and the structure can be restored in the shortest possible time to the usable state.

Lightweight steel framing is a method in housing and construction that have been widely used in lightweight steel construction. In this method, the structure is built by cold formed steel elements. They are cost-effective, light, and easy to assemble. However, the performance of lateral load resisting systems in cold-formed steel structures specially the behavior of cold-formed steel shear walls filled with lightweight structural concrete under seismic loads has not been studied in detail. In this study, an experimental investigation on cold-formed steel frames filled with lightweight structural concrete has been conducted and the results are presented. Six full-scale cold-formed steel frames filled with lightweight structural concrete with two different configurations were studied. The test was performed under a standard cyclic loading regime. This study is focused on the ultimate lateral load capacity and seismic response modification factor of cold-formed steel walls filled with lightweight concrete subjected to cyclic loads. Based on the test observation, detailed discussions on the failure modes of cold-formed steel wall specimens are given. Finally, shear load resistance, seismic response modification factor, failure modes, energy dissipation and stiffness of tested shear walls are proposed and discussed. The results show that although lower height to width ratio leads to a greater shear load resistant, energy dissipation, and stiffness for shear wall filled with lightweight concrete, its seismic modification factor is lower than those shear walls, which have higher height to width ratio.