نشریه مهندسی سازه و ساخت
سال نهم شماره 6 (پیاپی 59، شهریور 1401)

Risk assessment and prioritization is one of the most important components of risk management in any organization. Failure Mode and Effects Analysis (FMEA) is one of the most commonly used methods for assessment and prioritization of the multiple risks. Despite the widespread applications of this method in various industries, FMEA is associated with some shortcomings that can lead to unrealistic results. In this study, a new hybrid decision- making approach is presented in three phases to cover some of the shortcomings of the FMEA technique. In the first phase, based on the subject literature and getting help from a group of experts, 23 risks related to the construction project were identified and classified into six groups including technical, dynamics of the project environment, multiplicity of project stakeholders, employer, project management, and contractor. In the second phase, the fuzzy Stepwise Weight Assessment Ratio Analysis (SWARA) is used to measure the weights of decision criteria. In the third phase, the outputs of the previous phases are used as a basis to prioritize the risks using the Weighted Aggregated Sum Product Assessment (WASPAS) methods under fuzzy environment. To illustrate the potential benefits and applications of the proposed hybrid approach in a case study was implemented. The results obtained from the new hybrid approach to show that the low performance of the human resources, communication and cooperation of a poor contractor with another group, lack of proper management by the contractor regarding financial matters, supplier support, and subcontractors, and low performance of the human resources as the most important risks were recognized in the construction project of the Central Library of Markazi Province. Also, after performing the validation test and sensitivity analysis, it was found that the proposed method can provide valuable and effective information in helping to manage the risk of construction projects.

Subsurface identification in some cases requires seismic testing, especially when the goal is to identify anomalies at the site. Identifying and determining the dimensions of these anomalies is important because these cavities may be of considerable size and close to the ground. And cause irreversible risks by applying loading or any other changes in the soil environment. Seismic methods can also be used to identify aqueducts, mineral, oil and gas exploration. Due to various methods of identifying subsurface anomalies, in this paper, the multi-station surface wave analysis method is used, which is very fast and cost-effective. In this regard, by simulating in Abacus, finite element software environment, the effect of longitudinal dimensions of shallow subsurface cavities has been evaluated. The cavities are located at different lengths below the ground and the waves field in the time-offset and dispersion curves and graphs in the frequency-offset after the filter are examined. The obtained results in the time-distance showed that for a cavity with a length of 2, 4, 6 and 8 meters, the scattered waves are emitted from the far and near the face of the cavity with a longer time distance from each other in proportion to the increase in the length of the cavity. It can be concluded that the near and far boundary of cavity could be determined by using high resolution obtained data after filtering in time-distance domain, and more energy data in frequency-distance domain.

When the progressive collapse phenomenon occurs due to the column removal, the beam-to-column connections must have enough resistance and ductility to be able to withstand the additional imposed loads. Often the onset of failure in the structures exposed to abnormal loads arises from the beam-to-column connections. In the present study, using nonlinear quasi-static analysis method, the steel moment frame with different types of beam-to-column welded connections including welded unreinforced flange-welded web moment (WUF-W), reduced beam section (RBS), welded flange plate (WFP) and welded flange-weld web connection with internal diaphragms (I-W),‌ under three different corner, interior and side column removal scenarios and also the column removal scenario with two beams in line are evaluated. The force-displacement diagram and failure modes for sample connections at different positions of the plan are extracted. In addition to assessing the resistance of each connection in the four column removal scenarios, the comparison between the bearing capacities of each connection with other connections has been carried out for different column removal scenarios. The results revealed that the WFP connection (with maximum vertical force of 473.71 kN and maximum load factor of 2.49) in all connecting positions had better resistance to progressive collapse, and bearing capacity of this connection is high. After WFP connection, in the case of removal of the internal column with four perpendicular beams, the W-I, RBS, and WUF-W connections (with maximum vertical force of 369.40, 318.025 and 305.4 kN, respectively and with maximum load factor of 2.28, 1.90, 1.82, respectively) had a higher resistance, respectively. Examination of the results of load-displacement diagrams showed that WUF-W and W-I connections in the side column removal senario as well as RBS and WFP connections in the middle column removal senario had greater resistance to progressive collapse and high load-bearing capacity.

The addition of glass fibers has been used to stabilize the unsuitable clay of Rey city to reduce the subsidence in the strip foundations due to the improvement of resistance parameters. The combination of glass fibers with clay and the effect of using this additive on the stabilization of clay fine-grained clay (CL) were investigated in the laboratory. Soil samples in the natural state as well as in the combined state with different percentages of glass fibers equal to 0.2, 0.4 and 0.6, 0.8 and 1% of the dry weight of the soil were used for laboratory tests including standard compaction test, California load ratio test and direct cutting. Were located. The results show a decrease in unit weight of maximum soil volume and an increase in optimum moisture content, as well as a California load-bearing ratio by adding this material to the clay. The amount of adhesion and the internal friction angle resulting from the direct shear test increase with increasing percentage of glass fibers. After laboratory studies, the effects of using modified soil with improvement depths of one meter, two meters, four meters for strip foundations with widths of 0.75, 1.50 and 2.25 meters with the help of Plaxis2D software show that by increasing the percentage of mixing glass fibers In fine-grained clay soils, the amount of foundation deposition is reduced, while the reduction of foundation deposition on soil mixed with 0.8% glass fibers is more than soil mixed with 1% glass fibers. The reduction rate of the strip foundation with a width of 0.75 m with a mixing percentage of 0.8 glass fibers and a depth of improvement of 4 m is 1.57 cm. ،he reduction rate of the desired foundation with widths of 1.5 and 2.25 meters is equal to 2.29 and 2.72 cm, respectively

In this study, comparison of the performance of beam-to-column bolted end plate connections and T-connection under fire is considered. To achieve this objective, samples are selected in three types of bolt number, the thickness of end-plate, and T-connection. Then, they are investigated and nonlinearly analyzed in ABAQUS finite element software and the results such as displacement-time curves, counters of stress and displacement are studied. According to the nonlinear finite element analyses results obtained in the first and second types, the beam-to-column connections have been investigated by changing the number of bolts and increasing the thickness of the end plate. The results indicated that the highest and lowest values of displacement-time curves are related to the samples have a 25 mm thickness end-plate with 4 bolts and a 10 mm thickness end-plate with 4 bolts, which affect the thickness of the end-plate with 36% and 17% fire resistance to rupture, respectively. It can also be seen that among the samples, connections with weak end-plates and fewer bolts in the final moment of loading at the end of fire analysis due to the high stress of plastic hinges can be seen. In the third type, the T-connection is examined with increasing thickness. The results showed that the maximum and minimum values of displacement-time curves are related to samples with a thickness of 17.5 mm and 9 mm with 25% and 11% fire resistance up to rupture, respectively. By comparison of the results of beam-to-column connection by changing the number of bolts and increasing the thickness of the end-plate and T-connection, the best sample has 25 mm thickness end plate with 8 bolts.

With increasing population, there is an increasing use of natural resources to produce materials suitable for construction such as bricks, cement and strong rods. This has exponentially increased their prices and also polluted the environment by producing large amounts of greenhouse gases. Therefore, there is a need to provide cheap and durable infrastructure. In this research, the purpose of evaluating the use of Mazandaran common reed, which is found abundantly in agricultural land and landfills, was in the construction industry. To this end, several mixing plans were designed to replace the sand in ordinary concrete with coarse aggregate from the reed and the resistance of the designs was evaluated at the age of 7, 28 and 90 days. In the following, two wall panels with rows of Mazandaran rods were placed in two cases without steel mesh and steel mesh. To find out the two panels, Schmidt's hammer test was first performed for both panels at 28 and 90 days. Then, with a test based on a study paper, its displacement load diagram was evaluated in a three-point bending condition. The results showed that the use of reed aggregates in concrete has obtained an acceptable resistance to the construction of non-structural prefabricated parts. Also, the use of straw instead of rebar in the wall panels has a similar behavior to the panel with fittings and has shown a good performance.

Concerning the importance of shrinkage in the concrete industry, much research is being performed on this subject. Since the self-compacting concrete has high consistency, many researchers believe that the shrinkage of self-compacting concrete should be more attended than the shrinkage of plain concrete. Sulfates are among the common reasons for concrete destruction in most areas of Iran especially in the southern areas, where the concrete is subjected to seawater (which includes sulfate compounds). Since the amount of drying is higher in the surface of a concrete piece than its depth and the durability of the concrete structure highly depends on the strength and permeability of its surface layer, this paper applied a “Twist-off” test (which shows proper sensitivity against the surface change of concrete) to investigate the effect of shrinkage and magnesium sulfate on the surface strength of self-compacting concretes. Then, the change in the length of samples was presented together with their weight drop. In the end, by using the “Twist-off” test, the effect of magnesium sulfate and the length change of samples on the surface strength was evaluated. The results represent that the plain concrete, compared to the self-compacting ones, shows more reduction in the surface strength due to the effect of drying shrinkage. The reduction in strength of plain concrete is 18.4% by shrinkage that is 1.34 times of the self-compacting concrete with 45% fly ash, 1.35 times of the self-compacting concrete with 35% fly ash, and 1.37 times of the self-compacting concrete with 25% fly ash. For the self-compacting samples curing in magnesium sulfate solution, the 3-day and 7-day surface strengths were reduced by the increase of fly ash percentage, while the 28-day surface strength was increased.

In recent decades several destructive earthquakes resulted in extensive structural and non-structural damage in structures, that which was produced by lateral displacements. So, it reveals the necessity for theof accurate estimation of the lateral displacement of the structures in the design procedure. According to the present seismic design provisions, displacement amplification factor, (Cd), is being applied to acquire elastic lateral displacements in order to assess inelastic displacements, due to the ground motions. Besides, in many codes, these factors are empirical in nature and is based on structural performance, which has been observed in the past earthquakes; AlsoOn the other hand, the effect of height and number of stories are is neglected. In this paper, the effect of Cd on seismic performance of steel special moment frames is evaluated. Six types of buildings are designed with different values of Cd (i.e., 4, 5, 5.5, 6, 7, and 8). For each type of building,s 5 heights (i.e., 5-, 10-, 15-, 20- and 25-stories) are considered. The numerical finite element models are developed in Opensees. Incremental dynamic and nonlinear static analyses are performed to quantify structures’ seismic performance utilizing fragility curves and FEMA P695 methodology. The results indicate that the values of Cd provided in the codes for steel special moment frames does not induceare not completely effective on seismic performance, especially in short-rise buildings. Also, the probability of collapse of high-rise buildings are is less likely with respect to the medium-rise buildings; Therefore, in high-rise buildings, increasing the amount of Cd is not necessarily recommended, as because it increases the cross sections in of the frame members and makes the design uneconomical.

Creating slits in steel plate shear walls is a new way to improve the seismic performance of these walls. The creation of slits turns the steel sheet into a number of links, each of which dissipate the seismic energy at both ends of the links. In this study, the effect of slit location and orientation on the cyclic behavior of steel shear panels is considered. For this purpose, in a laboratory study, the effect of slits location in the central area (conventional method), in the middle of the boundary elements or sheet corners on the stiffness, strength and capacity of energy dissipation and drift corresponding to the start of sheet rupture was investigated. Experimental results show that, contrary to the conventional method with slits located in the central area of the sheet, changing the location of the slits leads to a fundamental improvement in the seismic performance parameters of the wall. The best performance is observed for the specimen with slits in the middle of the boundary elements and with parallel set of slits. The increase in the strength and drift is 39 and 100%, respectively, for the specimen with parallel set of slits in the middle of the boundary elements compared to the conventional specimen with slits in the center of the sheet. Better performance could be expected with optimization of slits spacing and patterns.

Earthquake is a destructive and unpredictable phenomenon that causes a lot of human and financial losses. An overall assessment of the damage to structures and facilities due to earthquakes shows that site conditions have had a significant impact on the distributions of damage. Therefore, identifying the effect of site and soil type in the design and construction of earthquake resistant structures is essential.Due to the fact that soil type has not been determined in many regions of the Iranian plateau, in this study, A relation is presented to determine the shear wave velocity using Horizontal-to-vertical spectrum ratio method (H/V) and the Gene expression programming (GEP).In this study, a suite of 480 records is used. Input factors in this research are moment magnitude, site to source distance, Horizontal-to-vertical spectrum ratio and the time of the maximum amount of H/V ratio. After preparing the input values from the earthquake catalog, finally, GEP method is used to obtain the prediction relationship. The advantage of this algorithm is that a fixed regression model is not used and the model is calculated intelligently. Finally, the results show that the model has a fitness of 911.57 and the shear wave velocity values provided by the relation correspond to 73% with the actual values.

The purpose of this study is to analyze the performance of various bond-slip models in modelling of reinforced concrete beams strengthened with FRP sheets. A comprehensive finite element model based on the concrete damage-plasticity behavior has been constructed. The cohesive element is used to model the bond-slip behavior and existing experimental results were used for verification. By comparing the results of the finite element model with the experimental results, the capability of the selected model in predicting beam behavior has been proven. The indent distribution of strains in FRP plates was due to the occurrence of cracks in concrete. With an increase in the loading, both the crack opening and the number of cracked sections in the beam are increased and the indentation state of the strain curves is intensified. On the other hand, the yielding of tensile rebars increases the strain in the FRP sheet. The interfacial shear stress values between FRP sheets and concrete shows high fluctuation at the final stages of loading due to the development of cracks and release of stresses at the crack tip. Maximum slip values between concrete and FRP surface occur near the loading points in which bending moment and shear force are maximum. The obtained load-displacement results showed that Lu-Bilinear and Lu-Simplified models have the best performance in modeling the bond between concrete and FRP sheets and in predicting the failure load of beams, they had On average 3.8% and 6.1% error with respect to experimental results, respectively.

The present multidisciplinary study focuses on providing a model for magnetorheological dampers. First, it presented a brief look at the existing models of such dampers, and then to achieve an invertible, efficient, and at the same time simple model, the Kwok model has been selected and has changed appropriately. A new identification algorithm based on meta-heuristic methods has been proposed to identify the model, which has used periodic excitation. This algorithm has high detection capability with the minimum necessary tests. To evaluate the proposed model and identification method, a large-scale magnetorheological damper, which is placed as a black box model in the benchmark base-isolated building introduced by the US Structural Control Committee, has been used as a virtual laboratory. The whole process has been investigated in the Simulink environment of MATLAB. The performance of the proposed model was compared with the original one under seven near-fault earthquakes. The results show that the modified Kwok model is more accurate than the original one. It can predict force-displacement and force-velocity behaviors correctly. Also, since the proposed model is invertible, it is easily applicable in practical issues of structural control. It provides the possibility of managing control devices, so is superior to the Kwok model.