نشریه مهندسی سازه و ساخت
سال هشتم شماره 6 (پیاپی 45، شهریور 1400)

Seismic behaviour of shallow foundation on adjacent of the sand slope crest is evaluated in this article. The foundation of various engineering structures has been made of Shallow foundation adjacent to soil slopes. While the shallow foundation is placed in the slope or out of the slope the amount of static and dynamic bearing capacity is reduced. Static bearing capacity and dynamic bearing capacity (Seismic) have been made up of respective coefficients. In fact, when the ground slope is increased the quantitative amount of bearing capacity coefficient of shallow foundation is reduced. Bearing capacity of the shallow foundation has been investigated by various researchers. Respective researchers evaluate this problem when respective shallow foundation is on the slope in static circumstance. In respective condition, the sloe and shallow foundation are under seismic vertical, horizontal loads as well as the combination of respective loads. Seismic vertical and horizontal load effect analysis under horizontal and vertical seismic load condition could be evaluated by critical state methods in quasi-static loading technique. Two-dimensional finite element method, as well as the computational framework of the plane surface, have been used for numerical simulation in current research hypothesis. Shallow foundations have been placed at a certain distance from slope crest. The slope studied in this research has a 25-degree angle (2:1 - V: H).The respective slope has been constructed by sandy materials with medium density. Constitutive elastic models such as Mohr-Coulumb (MC) and Hardening Soil Model (HSM) have been selected for hardening effect evaluation. Actual seismic behaviour of the slope, shallow foundation as well as the direction of seismic response have been investigated innovatively. Research results are presented that two constitutive models (MC and HSM) have completely different response in the zone of the structural element of shallow foundation behaviour and geotechnical performance of dry sandy slope.

A Composite Steel Plate Shear Wall (CSPSW) consists of an infill steel plate and a reinforced concrete panel attached to one side or both sides by shear studs. CSPSW is a lateral resisting system primarily used to resist wind and seismic forces. In a steel plate shear wall, the story shear is carried by the tension field action of the steel plate after buckling of diagonal compression. Meanwhile, In a CSPSW, concrete panels prevent the out-of-plane buckling of thin-walled steel plate, thus significantly increasing the load-bearing capacity the wall. One of the main parameters for seismic design of structures is the fundamental natural period. In this paper, the fundamental period of the structures with CSPSW by an analytical method has been presented. Following this, 27 numerical models were categorized three types including low-rise building, mid-rise building and tall building with 6, 12 and 18 stories, respectively. Furthermore, the considered models were in three displacement modes including moment, shear and moment-shear modes. CSPSWs were in the span widths of 1.5, 3 and 4 m, and also concrete panel thicknesses were including 30, 40 and 50 mm in one side of steel plate. To compute the fundamental natural period of the models, ABAQUS software was employed. The results indicated that the numerical period has a good compatibility with the computional period based on moment-shear analytical method. Therefore, the proposed relations in this paper are suitable. Also, the fundamental period of the structures was decreased up to 15% by increasing the span width of CSPSW. Meanwhile, concrete panel thickness didn't have remarkable effect on the fundamental period. Finally, it seems that the proposed relations by Iranian seismic design code (Standard 2800) and seismic codes in the world are valid for determining fundamental periods of structures with CSPSW.

Photocatalytic self-cleaning is one of the most important uses of nanotechnology in the building industry. In this paper, we investigate the effect of using silicafume and titanium dioxide and nano-silica on increasing or decreasing the self-compressive properties of precast concrete components in architectural view of concrete structures. Type I-42.5 cement was used according to American Society for Testing and Materials (ASTM) -C150 specifications. Silicafume conforming to ASTM-C1240 standard specifications in the concrete blend was used as a replacement for cement. For investigation the use of TiO2 on the reduction of environmental contamination paint on the surfaces of precast concrete, three designs with zero and 2.5% and 5% TiO2 percentages were used instead of cement in the mix design. Better results were obtained with the sample with 2.5% and 5% TiO2 compared to the sample without titanium dioxide addition. The results show that TiO2 with 5% cement replacement with silicon with 20% cement replacement than 3% Nano-silica has more potential to improve the environmental properties of concrete facades of buildings in heavily contaminated cities in terms of concrete surface cleanliness and cleanliness. Better results were obtained with the sample with 2.5% and 5% TiO2 compared to the sample without titanium dioxide addition. The results show that TiO2 along with silicafume and Nano-silica has great potential to improve the environmental properties of the concrete facade of buildings in cities exposed to high contamination in terms of surface cleaning and cleaning.

Earthquake vulnerability is the major weakness of unreinforced masonry structures. Various methods have so far been proposed to strengthen such structures against earthquakes. The recommended procedures are not especially suitable for this type of structures, that are meanwhile historically and culturally valuable. One of the adequately suitable methods of retrofitting of this particular type of structures is the center-core technique; based on which the façade of buildings with no change whatsoever. Scantly little studies have so far been conducted on structural retrofitting and the essential research carried out in this area has focused on the study of masonry piers. In this study, the in-plane nonlinear behavior of two full scale unreinforced masonry wall specimens, retrofitted with three and five reinforced cores, were tested under experimental cyclic loading; and their related hysteresis force-displacement, envelop force-displacement (backbone curve), energy dissipation and secant stiffness degradation curves, were plotted. Using envelop curves, ductility and effective stiffness parameters of each of the two specimens were extracted and the results were compared with those of the reference non-retrofitted wall specimen. The outcome results revealed that this method has led to 42% increase in ultimate strength and a 55% increase in ductility of the three-core specimens compared to 84% increase in the ultimate strength and 236% rise in ductility of the five-core sample. Also, the reinforced samples’ effective stiffness raised significantly as compared to the non-retrofitted specimen. Failure and damage patterns of the strengthened specimens showed that their failure modes, compared to the non-retrofitted reference specimen, have converted from diagonal to combination of diagonal and sliding failure mode.

The buckling behavior of compression member has a decisive role in the collapse behavior of a structure. The buckling and sudden capacity loss of the compression member can be prevented using a proposed PPFLD and the brittle post-buckling behavior of the compression member can be converted into ductility behavior. The PPFLD consists of two pipes, one of which is placed into the other pipe and the axial force applied to the inner pipe. Thus, the outer pipe operates as a casing for the inner pipe. The present study investigated a number of experimental specimens. Next, numerical analysis of these specimens has been done using finite element software. Further, the behavior of the PPFLD have been investigated under important parameters such as the gap between two pipes, the inner pipe slenderness coefficient, and the ratio of outer pipe length to inner pipe length, by studying more numerical specimens. The results indicate this PPFLD is an effective, simple and economical method to prevent the buckling of compression member and can lead to a favorable increase in the bearing and deformability capacity of the compression member. The bearing capacity of this PPFLD is inversely related to the size of the gap, and is directly related to the ratio of the outer pipe length to inner pipe length. The bearing capacity of the member will increase significantly, if the gap size is less than 43% of the inner pipe's gyration radius, and the the ratio of the outer pipe length to inner pipe length is greater than 55%. This is more sensible especially when the outer pipe covers the entire length of the inner pipe. The proposed PPFLD has the potential of eliminating the buckling of compression member and providing adequate and sufficient restraints to make yielding at compression member with different slenderness.

Given that bent steel bending frames are one of the load-resisting systems such as earthquakes and winds, the role of bonding resistance in these frames will be crucial. The purpose of this study was to investigate the behavior of semi-conductive welded steel joints on the seismic behavior of 3D steel frames. The results of this study show that with the decrease in the number of structural classes, in this project the reduced formability of the structures decreases the IDA curves to a lower IM level, indicating that with increasing Structural plasticity can be achieved by higher computations in structures at the same earthquake level. Also, the coating curves corresponding to the structures with less ductility are at a higher level, that is, the coating curve is lower at higher level, with increasing formability in nonlinear static analysis. In other words, with increasing rigidity of the joints, the structures behave more rigidly and their bending curves are higher and the structures with higher plasticity become horizontal at lower seismic intensity levels. And the rigid structures are at a higher level, which is also reflected in the results of nonlinear static analysis, and by decreasing the rigidity of the joints, the effective alternation time of the asymmetric structure increases and the spectral acceleration decreases. Also with decreasing joint rigidity, the contribution of higher modes increased, so in semi-rigid joints the number of effective mods in the structures is higher than the rigid state. This issue can play an important role in the design of the structure. According to the findings of this study, little work can be done to investigate this method in the country, although research on the behavior of welded steel joints has so far been studied.

Today, Buckling-Restrained Braces (BRB’s) are considered as lateral load-bearing systems due to their non-buckling in compression. But these braces also have disadvantages. Among these disadvantages is the creation of permanent deformation in the structure after the end of loading and also the costly replacement of these members after the failure and current of the steel core of these braces. Therefore, the use of Shape Memory Alloys (SMA’s) in BRB systems, given the specific characteristics of these alloys, can be an effective step in improving seismic responses. In this paper, seismic behavior of frames with BRB’s and the effect of utilizing SMA’s were studied. Then, three 2D-frames with 6 and 12 story were utilized. The OpenSees software used for the nonlinear time history analysis of frames. The BRB’s considered in two cases, with and without SMA’s. For development of fragility curves, according to FEMA P695 seven strong ground motion records was utilized. Incremental Dynamic Analysis (IDA) procedure was utilized to achieve probability of frame collapse. The results show that the collapsing capacity of BRB frames equipped with SMA’s is higher than that of the BRB frames. As an example, at the 50% probability level, the collapse capacity of a 12-story frame with a BRB equipped with SMA is 30% higher than that of a frame with BRB. The results also show that in 6-story frames for different spectral accelerations, the BRB system equipped with SMA compared to the BRB can reduce the probability of collapse by 28%. Using SMA’s in these building systems can reduce the cost of restoring and recovering of damaged systems and make the more resilient building system.

The steel moment resisting frames (SMRF) are the most common type of structural systems for bearing the gravity and lateral loads while this system is one of the more vulnerable structural systems under fire loading due to rapid descent of stiffness and strength properties of steel with temperature. In this regards, many researchers experimentally investigated the behavior of steel structural elements (e.g. Column, Beam, Connections) when exposed to fire. Most of these researches are limited to a sole element. Therefore, in this paper the entire behavior of the Steel moment resisting frames with intermediate ductility under different fire scenarios and for several gravity load ratios are studied through the numerical models. Three steel moment resisting frame with different stories and gravity load ratios in this study are considered. The analytical models of the studied frames are modeled in ABAQUS software. The results show that in different cases depending on the ratio of the gravity loads, different failure modes occur. In cases with the normal gravity loads, progressive collapse does not occur while with increasing the gravity loads; the vulnerability of structures increases and the potential of progressive collapse are increased.Fire loading, Steel moment resistant frame, Progressive collapse, Numerical models

One of the most important issues discussed in construction management companies is the prioritization of projects and the allocation of resources among the organization so that through this selection the profit of the organization will be maximized. Construction Projects due to the close relationship among the parameters of the project and the unknown exterior environment; they encounter uncertainties in complex environment. In as much as the issue of evaluating and prioritization of construction projects is a difficult problem, the network structure is a suitable approach to explain them. In other words, the assessment and prioritization of construction projects based on risk factors in the real world is a complicated problem with many quality and ambiguous characteristics. In this study, by investigating the criteria and indices of construction projects with optimal selection used in the literature of the subject and adapting them with the experts in the field with conditions and situation of the problem, six projects have been selected and investigated. The criteria used in the research include, the facility of the performance, time, finance, geographical location, the importance of structure and the employers popularity. In this project the Best-Worth approach was used to weigh the options, VIKOR method was used to solve the evaluation problem and to prioritize the construction projects. The presented model helps the decision makers to make more accurate decisions and to be able to prioritize the construction projects which are the important strategies of some organizations so that they can apply correct management.The results obtained by the Vikor method showed that the ten-storey building with one basement floor in Neka was the highest priority. Also, after solving the mathematical model developed in this research, it was found that the selection of the projects was performed in accordance with the scenarios considered and performed well.

Necessity to a complete and accurate analysis of the crack behavior in concrete dams using new methods is felt due to the sensitivity of the cracking problem in these dams. Meanwhile, meta-heuristic algorithms have a very good performance and accuracy in evaluating and predicting problems rather than other methods. In this study, Zayandehrood arch concrete dam has been chosen as the case study and the displacements in the cracks of this dam have been investigated by using election algorithm (EA). Water level and concrete temperature from 2000 to 2013 were considered as input parameters and also horizontal and vertical displacement of cracks were selected as output parameters. The results were compared with genetic algorithm (GA) and artificial neural networks (ANN). To evaluate the performance of the proposed method, three statistical criteria including correlation coefficient (R2), root mean square error (RMSE) and Nash-Sutcliff efficiency (NSE) were utilized. The results show that EA has a higher efficiency with R2 = 0.96, RMSE = 0.022 and NSE = 0.74, compared to GA and ANN. However, due to the lack of sufficient data, the amount of regression coefficient for spillway cracks was lower than the dam cracks. It is concluded that for evaluating the displacements of cracks in concrete dams and predicting their variations in future, meta-heuristic algorithms can be utilized as a very exact and powerful method. These methods can help dam managers and decision-makers in monitoring and vulnerability analysis of dams during their operation.

Reinforced concrete (RC) flat slabs are utilized, because of their advantages such as covering large spans without beams, ease of execution increased construction speed, and decreased overall building height. However, this system is at risk of punching shear failure. In recent years, various methods have been proposed to strengthen RC flat slabs, but the latest of ones are penetrating and passing fiber reinforced polymers (FRPs) fan through the slab thickness. This method has been successfully evaluated in previous studies, and this research is tried to assess the most suitable pattern of FRP fan installation for punching shear. To reach this goal, two specimens of flab slabs from the available experimental studies, including one control and one strengthened specimen under pushover loading are similarly modeled and analyzed in ABAQUS Software to prove the accuracy of the analytical results. Then after considering two types of strengthening scheme with different patterns and changing the number of holes passing through the thickness of the slab, 18 samples are modeled in this Software. These nonlinear analyses are performed to determine the best pattern in terms of bearing capacity, ultimate displacement, ductility, energy absorption, stiffness and to find the best distance of FRP fibers form the column face. The results showed that the L1 which FRPs were placed in two parallel rows around the four sides of the column, noticed best among the other models. Among the radial patterns, the R5 which has six rows of FRPs arranged radially around the center of the slab has shown the best performance. Whatever the method of FRP fan strengthening is the load-bearing capacity, absorbed energy, and stiffness increased 137%, 535% and 21.6% compared to control slab, respectively. The results of the analysis can be used to determine the appropriate pattern of slab strengthening considering the economic aspect.

This study investigate the effect of Pumice and Metakaolin Pozzolans on properties of recycled concrete. In order to build the specimens, 10 percent of Taftan Pumice, 15 percent of Metakaolin and combination of both Pozzolans were replace to the cement. Compressive strength, water absorption, the penetration depth at the age of 28 days and 90 days for all specimens are obtained. The results of the tests indicate that the single use of Pozzolan operates better when it used in a composition. The specimen with 15 percent Metakaolin increased the compressive strength by 5.2 and 11.73 percent on days 28 and 90 in comparison with the recycled concrete specimen, respectively. Also in water absorption 27 percent decrease was caused on day 28 and 30 percent decrease was caused on day 90. And the 10 percent Pumice specimen performed better on day 90. On day 90 the water absorption was decreased by 25 percent and the remarkable decrease of penetration depth which was decreased by 53 percent. The reason of this reduction could be caused by the low hydration speed of Taftan Pozzolan and also the completion of Pozzolan and Morphology reactions. In the case of corrosion testing, the addition of Pozzolan alone increases concrete’s resistance against corrosion, so the specimens with 15 percent Metakaolin and with 10 percent Pumice Taftan perform better in comparison with the combined specimen. The reason is that the uniform structure and also the presence of Hydrated Calcium Silicate gel(C-S-H), which decreases the cavities and the passing electrical flow which causes more corrosion resistance.

Structural elements and systems experience a decrease in strength and stiffness throughout their lifetimes, called degradation. One of the most common types of degradation in RC (Reinforced Concrete) structures is the cyclic degradation caused by earthquakes. Structures that experience one or more earthquakes during their lifetime, experience a degree of degradation that affects their seismic response to subsequent earthquakes. Existing numerical models take into account the cyclic degradation of an earthquake, but many of these models neglect the effects of degradation caused by previous earthquakes; Recent studies show that this degradation has significant effects on the response of structural elements. In this study, the cyclic degradation of RC beams and their impact on the post-earthquake behavior of the beams is investigated experimentally. For this purpose, 12 RC beams are manufactured and subjected to displacement-control loading. Periodic loading with uniform amplitude is used to simulate the earthquake cyclic degradation. Three levels of slight, moderate and extensive degradation are selected to investigate the effect of cyclic degradation on the post-earthquake behavior of elements. After the experiment, the results of the hysteresis diagrams, strength degradation and energy absorption of the specimens are presented and discussed. The results of this study show that as the level of cyclic degradation increases, the energy absorption of RC beams decrease; Especially in the extensive level of degradation, the energy absorption of the beams is reduced by more than 40%.

The potential danger of fire is one of the important phenomena that may cause Irreparable damages the structure. Therefore, add fire protection is essential for columns as the main components of a structure that require sufficient fire resistance for increase in safety. In this study, the effect of expandable paint coating on the temperature distribution at the cross section and time of fire resistance of concrete-filled steel columns that are suitable for high seismic areas and tall buildings have been studied. For this purpose, in first step the finite element model of a steel column filled with concrete under ISO 834 standard fire was prepared and analyzed according to available laboratory data. After validation of the results from the finite element model in comparison with the laboratory data, various specimens of columns that protected with Intumescent Fire Coating and with circular, rectangular, square and oval sections, designed according to the Iranian Steel Code and has been modeled and analyzed by Abacus finite element software. The results show that the expandable paint coating increases the fire resistance of concrete-filled steel columns with circular, square, rectangular and oval cross sections by 2.2, 3.3, 4.14 and 3.36 equality has been afforded to those without protective cover.

Using Tuned Mass Dampers (TMD) is one of the common methods for the passive control of structures subjected to earthquake. The structure of these dampers consists of three main parameters: mass, damping and stiffness. Multiple Tuned Mass Dampers (MTMD) reduce the amplitude of the responses by affecting over the modal properties of the structures. In the most cases, the installation of only a single TMD on the roof of the buildings or several dampers at the several points of the roof of the buildings requires considerable mass and space. In this study, the performance of MTMD in regular and irregular L- and U-shaped ten-story steel building is investigated under the near and far-field records. Nonlinear time history analysis is also applied in this paper. The SAP2000 software API function and MATLAB Genetic Algorithm (GA) is also utilized to determine the optimal locations of the MTMD in the roof plan. The results demonstrate the efficiency of MTMD on reducing the seismic responses of the building including acceleration, displacement and base shear such that on average, the roof displacement, acceleration, and the base shear are reduced 50,40 and 40% respectively. The optimal locations of MTMD in the ten-story model also indicate the importance of the symmetrical positioning of the dampers relative to the centre of mass of building.

One of the most simplifying computational assumptions in the design of buildings is the omission of infills in the analysis and design of structures. The reason for this is the extremely complex nonlinear behavior of these members that fall into the category of non-structural components. International codes usually apply some factors to the equations in order to enter the influence of infills. Many studies have reported the key role of such members in the resistance of structures against earthquakes and other unexpected accidents. Therefore, it seems crucial to study structures considering infills. In this study, the resistant shear of the infilled frames is investigated by considering the existence of infills. The geometrical parameters affecting the behavior of such members are analytically studied in detail and some relations are suggested for the effects of thickness, length and height of infills. Some of the existing macro theories for modelling of infills along with the proposed relations by the researchers to examine the infilled frames are also reviewed. The proposed results show that square infills with equal length and height have the least amount of resistant shear. In addition, increasing the thickness of the casing will have a significant effect on the resistant shear of the frame.

This study presents a new hybrid framework based on the multi-criteria decision making to rank the potential site layout locations by consideration of the cost and safety criteria in the Mehr Construction Project in Tehran, Iran. To this end, all of the criteria in selecting suitable potential locations are extracted from the research literature and the most effective ones, which are matched with existing conditions in Tehran based on the opinion of experts, are considered. Then, the proper locations for site layout are determined as the potential alternatives and ranked by experts based on the structure, which exists in the proposed method. According to the data collecting from the questionnaires, the weights of selected criteria are calculated using WBM and the final ranking of the locations is performed using two Gray Relational Analysis and VIKOR methods. The computational results indicate that both VIKOR and GRA methods have largely the same ranking. However, a method with higher reliability should be used to select the best potential location of a construction site layout. Therefore, the sensitivity analysis of final outputs on the parameters existing in VIOR and GRA methods is used to rank the alternatives and select the best approach. According to the computational results, a GRA method has higher robustness compared to the VIKOR method. Accordingly, the ranking obtained from the GRA method is employed as the final solution in implementing the case study.

Recently, with the increase in the height of buildings, the need to use systems resistant to lateral forces such as earthquakes and strong winds has become more pronounced, and the lack of attention to them will lead to damage. Among the systems resistant to dynamic loads, the piston-shape bracing system has an important role in the stability of structures and the control of dynamic responses, such as displacement and acceleration, and by absorbing energy, the structure is protected against various excitations and prevent serious damage to the structure. In this paper, a new piston-shaped system consisting of two outer and inner tubes and several parallel semi-circular plates attached to them is considered, which exhibits good resistance to compression, tensile and buckling, and can be mounted in a variety of concentric, eccentric and other ways, reduce the lateral forces to the structure by dissipating energy. In this paper, the behavior of a steel frame using the piston-shaped bracing system against dynamic loads is investigated and some of its dynamic responses are controlled. Five types of pistons are designed for this purpose, each placed in a one span steel frame. After modeling all five types of braces, the results are compared with each other. The main purpose of this study will be to investigate the efficiency of controlling dynamic responses such as displacement, velocity and acceleration and buckling of the piston-shaped brace to minimize the damage caused by lateral loads applied to the structure.

Structures are considered as one of the main sources and resources of each country, due to their long-term and continuous use and the need to preserve human lives; they must always have sufficient stability and safety. Accordingly, the behavior of concrete is subject to the high degree of temperature is very important. The use of high-alumina cement has attracted the attention of researchers because of the considerable weakness of conventional cements at temperatures above 300 ° C. In this study, using the cement of IRC40 Calcium Aluminate instead of conventional cement, the combination of two types of steel fibers and polypropylene fibers was used in the manufacture of concrete. The purpose of this study was to evaluate the effect of high temperatures on the mechanical properties of Calcium Aluminate cement concrete and calculate the energy absorption of concrete samples after depositing them in the vicinity of 600,110 and 800 degrees Celsius. In the same way, four mix composition based on the use of four levels of 0, 0.5, 1, and 1.5% hybrid fibers were used to make a total of 108 samples, including cube compressive specimens of 10 × 10 × 10 cm, cylindrical tensile specimens with a diameter of 10 and a height of 20 cm and flexural beams with dimensions of 6 × 8 × 32 cm. According to laboratory results, the use of 1.5% of the hybrid fiber increased the amount of mechanical properties, including compressive strength, tensile strength and flexural strength, as well as increased energy absorption.

In this study, the effects of added stiffeners on the frequency and seismic response of an intake tower during construction period are investigated. For this purpose and in order to better investigate the effects of stiffeners, two types of circular and vertical stiffeners have been used in different numbers and height levels. It is also examined for situations where the weight of the structure is reduced in the amount of the added stiffeners' weight.In this study, the frequency responseof these models after adding the stiffeners was compared with the original model. The results show that the initial frequency of the structures is reduced and increased by the use of circular and vertical stiffeners, respectively. This indicates the effects of type and number of stiffeners on the frequency response of the structure. In order to better investigate the effects of these types of stiffeners, examined intake towers have been subjected to seismic excitation. The results show that the displacements and stresses are increased for the states in which circular stiffeners are considered. Also, for the intake towers with the vertical stiffeners, the values of displacements are decreased and the stress values are adjusted depending on the level of stiffeners. The results indicate the importance of the effects of stiffeners on the frequency response and seismic response of the intake tower and indicate the necessity of investigating these states.

Due to the importance of economic issues in building constructions, in recent decades, many studies have been performed on structural design optimization to reduce the constructional costs in various stages. Meanwhile, the structural weight is one of the important objective functions that is often applied to structural design optimization. In this study, a new single-objective optimization problem is proposed for performance based seismic design of two-dimensional steel moment resisting frame using nonlinear dynamic analysis based on the recent design codes. The objective function is defined as the weight of the frame, which should be minimized subject to some design constraints including section size compatibility, serviceability and performance-based limitations. As a well-known meta-heuristic method, particle swarm optimization (PSO) algorithm is utilized for solving this continuous optimization problem. Nonlinear dynamic analysis is employed for performance based seismic design based on specific seismic performance and seismic hazard levels. Since nonlinear time history analysis considers both material and geometric nonlinearities, it is the best choice to obtain accurate and realistic results among other seismic analysis methods. Also, spectral matching method is used for the scaling procedure of eleven accelerograms. Design example shows applicability and capability of the proposed optimization problem as well as the PSO algorithm.

Reactive powder concrete is a special type of concrete whose strength and durability have been improved by removing coarse-grained materials and the use of additives, and due to the variety of materials and methods of construction, the ratio of components or in other words Different mixing schemes have been proposed for the production of this type of concrete, and it will be difficult to decide on the best choice of reactive powder concrete mixing scheme. In this research, it is tried to use multi-criteria decision making techniques in order to rank and select the most appropriate mixed concrete powder mixing designs.Effective indicators in the concrete mixing plan include: cement, water, silica powder, silica sand, microsilica powder, superplasticizer, compressive strength, water absorption percentage and unit weight of volume, which are determined and evaluated using research background.First, the weight of the indices was determined by Shannon's entropy method, and the decision matrix was formed, then the reaction powder concrete mixing schemes were ranked separately with the three techniques of SAW, TOPSIS and VIKOR. Research shows that using different decision-making techniques can lead to different rankings for options. Therefore, in order to obtain the final ranking, the Copeland method has been proposed as the best method, and the use of multi-criteria decision-making techniques for ranking the mixed concrete mixing projects is a suitable and acceptable method.The final ranking of Copeland was compared with the techniques of SAW, TOPSIS, and VIKOR, and it was found that the results of ranking of SAW, TOPSIS, and VIKOR methods were 100, 85, and 70 percent consistent with the Kopland method, respectively. Also, the SAW method was considered the most suitable method for ranking reactive concrete mixing schemes due to its 100% compliance with the Copeland method.

The need for adequate and appropriate living and working spaces and population density and the increasing cost of land and use of high-rise buildings requires growing research on these structures. The tube system is one of the most suitable structural systems for high-rise buildings. The purpose of this study was to obtain one of the most important dynamic properties, namely the natural frequency (ω) for a number of tall buildings with a pyramidal tube system. A tube-in-tube approximate method for analyzing and calculating the natural frequency of a combined pyramidal tube system with shear wall pyramid is presented. The size of the pyramid angle of the tube frame varies with the length (height) of the structure. The proposed method enables us to calculate the natural frequency of vertical and curved tall buildings with the help of computer programming. The models were analyzed using finite element form and mathematical analytical method. The results show that the investigated method correctly calculates the natural frequency and is in good agreement with the finite element results and has better compatibility with pyramidal angle structures with higher altitude, and the resulting computational error is much lower. The results of the proposed mathematical model provide an easy-to-use method for understanding the dynamic properties of structures and the effects of angle-frequency variations. Furthermore, this analytical method has the least error for tube systems with tube-in-tube and the highest error for shear wall pyramidal systems.

In this paper, the out-of-plane behaviour of 30 models including two types of brick masonry walls with openings of 6000×3000×300 mm3 and 3000×3000×300 mm3 in two cases of unstiffened and stiffened with FRP strips under cyclic loading has been studied. The width, height and location of the openings have been the variables. A non-linear behaviour has been assumed for the materials and the finite element code ANSYS has been used for analysis. Obtained results indicate that the existence of the opening causes the 3 m wall to crack earlier than the 6 m wall. In 3 m walls, by approaching the opening to the upper corner of the wall the maximum displacement at cracking decreases and this maximum value increases by stiffening the opening. But in 6 m walls with an opening, the effect of the location and dimensions of the opening on this maximum displacement is less. In 3 m walls, by increasing the dimensions of the opening or decreasing its distance from the wall top corner the dissipated energy decreases. This value increases by stiffening the opening. But in 6 m walls, the dissipated energy is less dependent on the opening, although stiffening by FRP strips increases the dissipated energy with respect to unstiffened walls.