نشریه مهندسی سازه و ساخت
سال هشتم شماره 11 (پیاپی 51، بهمن 1400)

Brick and mortar are two main materials which have great influence on the behavior of masonry structures. Nowadays, bricks with different shapes, ingredients and strength and mortars with various strength characteristics are used in construction, where this diversity may confuse engineers to choose these two types of materials properly. In this experimental study, using two conventional types of solid and hollow burnt clay bricks in masonry construction of Iran and two types of strong and weak cement-sand mortars, standard tests were performed to determine and to compare the mechanical properties of masonry prisms, including compressive strength and diagonal-tensile (shear) strength and brick-mortar bond properties including flexural tensile and direct shear strengths. The results showed that the compressive strength of brick prism, the diagonal-tensile strength of brick panel, and direct shear strength of brick prism are more sensitive to the type of mortar compared to the shape of brick. Moreover, the flexural tensile bonding properties of brick prisms, due to presence of holes in the bricks and the possible interlocking, is more sensitive to the shape of brick compared to the mortar type. In general, among all the studied cases masonry specimens with hollow bricks and strong mortar have better performance.

By development of science and technology, new structural systems have been developed and researched. In the last four decades, extensive studies have been done on the application of the steel plate shear wall systems. Steel plate shear walls are made and executed in various shapes. Trapezoidally corrugated steel plate shear wall is a relatively new structural system. In this paper, the effects of position, geometric shape, percentage, distance from the boundary elements and the use of the stiffener around the opening were investigated in the seismic parameters of the trapezoidally corrugated steel plate shear wall system including stiffness, strength, ductility and dissipation energy by using 46 models. The openings were geometrically square, vertical and horizontal rectangular, equal to 10, 14, and 18 percent area of the steel panel. This research was performed analytically using ABAQUS finite element software. The results of the study show that the square-shaped opening has better performance than the rectangular opening in all positions. Also, models with central opening have lower strength, initial stiffness and energy absorption rather than other models. Overall, the best position to create the opening in the corrugated plate is in the middle top of the plate and at the distance of 160 mm from the beam and also in the upper corner of the plate but without distance from the boundary elements. Another result of this research is that by using stiffener around the opening, initial stiffness and strength and energy absorption of the corrugated steel shear wall can increase until 41% and 25% and 24%, respectively. In addition among the different stiffeners, the plate with 60 mm width and 3 mm thickness has the best dimension for the stiffener around the opening.

Many studies have been conducted on the fields of Building Information Modelling, Lean construction and Sustainability not only individually but also pairwise. Despite that, there are currently no researches that integrate these concepts collectively. In order to fill this gap, a systematic literature review was conducted. The input data of this research are 95 valid international articles that are mostly focused on pairwise interaction of these concepts. Using Grounded Theory, which is a method based on line-by-line review of articles and coding of sections related to the purpose of the article and with the help of Atlas.ti software, we found triple codes that represent the integrated fields of all three concepts. The triple codes were placed in 6 main categories: Stakeholder management, cost management, material waste management, resource management, project productivity and energy management. Then, by comparing each code with other codes, 6 main theories were created. To analyse these theories and prioritize them, an interview was presented in the form of a 6-question questionnaire, in which 10 experts and professors expressed their opinions. Then, the questionnaire was analyzed using statistical methods and SPSS software. To that end, Friedmann's non-parametric test was used to prioritize theories after the variables were found to be abnormal by the Kolmogorov-Smirnov test. as a result, combining the three concepts could be more effective on waste material management than other categories.

Thermal power plants are one of the most sensitive centers in Iran in terms of occupational accidents. The first step in controlling occupational accidents in this area is to identify their causes. In this research, for the first time, the dimethophase technique and Dalalah method have been used to evaluate and rank safety risks in thermal power plant construction projects. This research has been conducted as an expert-centered. For this purpose, 15 experts with appropriate work experience and familiarity with risk and risk management were purposefully selected. A total of 17 indicators in three dimensions of human, equipment and management were extracted based on literature review and research background and were approved by industry experts through a questionnaire. Then, the effect and effectiveness of the indices were investigated using the dimethophase method. The results show that among the human sub-criteria, the lack of safety training and practice is the most effective; Among the equipment sub-criteria, the lack of first aid equipment is the most effective and the criterion of lack of proper maintenance is very effective. Among the management sub-criteria, the lack of leadership and support of senior managers of the organization on the issue of safety is the most effective and the lack of creating a safety culture is very effective. In the end, the factors were ranked using the Dallah method; The results indicate that among the human sub-criteria; Lack of safety training and practice among equipment sub-criteria; Lack of proper maintenance and management sub-criteria; Lack of proper planning and prevention have gained the first ranks.

One of the aims of structural engineers is to improve the behavior of structures and reducing their responses under dynamic lateral loads. The structural control systems are advanced techniques to reduce the structural responses against vibration, and Tuned Liquid Damper (TLD) is a well-established tool for the control of structures. In this study, the effect and behavior of TLD under 7 far-field earthquakes and 7 near-field earthquakes was investigated in ANSYS software. To assess the performance of TLD on the control of structural responses including displacement, acceleration, and velocity, the effect of four different design parameters i.e., tank length, water height, water ratio, and mass ratio (with 27 different designed alternatives based on closed-form relationships proposed in the literature) were studied. The results showed that when the water ratio and the mass ratio of the cubical container are equal to 0.375 and 5 percent respectively, The TLD had the best performance under near-fault records. Also, the designed TLD with a 5 percent mass ratio and 0.125 water ratio outperforms other designed alternatives under far-fault records. In general, and among the considered alternatives, the performance of the damper with a higher mass ratio improves all studied performance criteria. Also, the well-designed TLD could reduce the acceleration better than velocity, and velocity better than displacement.

Marble dust is an industrial by-product that has recently been used as a mineral powder to improve the mechanical properties of concrete. Furthermore, since large amounts of marble dust is available in the waste of stone crushing plants in areas like Kurdistan, employing this powder in the process of making concrete reduces both environmental pollution and the final price of concrete. In this paper, an experimental study was conducted to evaluate the effects of using marble dust as a partial replacement of sand in concrete on slump, 28-day compressive strength, and durability at 28 days. To this end, 180 cubic specimens with 30 mixing designs were tested at the age of 28 days. Studied mixing designs by considering two general groups include three ratios of water to cement (0.4, 0.45, and 0.5) with five ratios of marble dust to sand (0, 0.05, 0.1, 0.15, and 0.2) for each water to cement ratios, and two fineness moduluses of 2.4, and 3 for each groups. The results indicated that partial replacement of sand with marble dust in concrete has different effects on concrete slump. Whereas, it improves compressive strength and decreases permeability of concrete. Moreover, it was found that for each of water to cement ratios, and for both quantities of fineness modulus of sand, increasing marble dust-to-sand ratio from 0 to 20%, increases the compressive strength by 5 to 16% with respect to its respective control specimen. In addition, the results indicated that for each of water to cement ratios, and for both amounts of fineness modulus of sand, increasing the marble dust to sand ratio from 0 to 20%, decreases the depth of water penetration by 55 to 79% with respect to its respective control specimen.

Population growth and development of economic relations have led to increase utilization of transportation infrastructures. The bridge is one of the important components of road construction that always needs special attention during the whole period of design, execution and operation. To ensure that the stairs are regularly inspected, evaluated and operated, management is needed to meet this need in the stairs by performing appropriate maintenance and repairs. Therefore, in this study, a three-objective optimization model includes minimization of maintenance costs, maximization of bridge performance index and reliability of bridges. For this purpose, a complex integer mathematical programming model has been developed. In order to solve the problem, a multi-objective particle mass optimization algorithm has been developed. From the solution of the proposed algorithm, different Pareto answers are obtained so that the decision makers can choose the answer from the obtained Pareto answers that is their priority.Also, after performing a sensitivity analysis on the parameters of failure rate and failure rate during the effect, it has been observed that by increasing the scenario number in two cases, which indicates an increase in failure rate and failure rate during the effect, the amount of costs increases and The overall performance of the system has been declining, which seems natural and correct.

With the growth of different uses of water and its conversion into wastewater, a large volume of various types of wastewater enters the environment. Therefore, the need for wastewater treatment and optimal use of its effluent can be considered an important step towards environmental protection. Considering the construction industry uses a significant part of nature's raw water for producing different materials, it can be expressed that using the effluent of the wastewater treatment plant is a valuable step in environmental protection. Self-compacting concrete (SCC) is a flowing concrete that does not require vibration and, indeed, should not be vibrated. It uses superplasticizers and stabilizers to significantly increase the ease and rate of flow. In this study, the effects of using the effluent of the wastewater treatment plant on mechanical properties, efficiency, and permeability of Self-Compacting Concrete specimens cured for 7, 14, and 28 days have been investigated. It should be noted that tap water has been used to make control samples. The results of the experiments show a slight decrease in compressive and tensile strength of the effluent samples compared to the control samples. Also, according to the results obtained from the efficiency experiments, it can be concluded that the effluent self-compacting concrete samples and the control samples are in the same classification. they take. On the other hand, according to the results of permeability experiments, it can be concluded that the samples of effluent self-compacting concrete have an increase in permeability compared to the control samples and the amount of permeability decreases with increasing concrete age.

Today explosion in urban centers and residential areas, there is a danger that threatens all buildings. Explosions inside or near a building can cause sudden damage to building frames. Analysis and design of structures under explosive loads requires a precise understanding of the dynamic response of members and systems of structures under this load.In this research, the behavior of three types of flexural joints of reduced type, end plate and reinforced with top and bottom plate in the phenomenon of explosion and progressive failure has been studied and to perform these studies and numerical simulation of ABAQUS finite element software And Etabs (V.NL13) were used.In determining the type of explosion, two parameters are usually decisive: the size of the weapon, which is equivalent to the weight of TNT, and the distance, which indicates the distance from the center of the explosive to the desired volume. In steel structures, there are two types of lateral load-bearing systems: flexural frame system and simple frame system with bracing. In the meantime, the bending joints of the beam to the column are the bridge of this partnership, and if it is destroyed, the structure can suffer a lot of damage. Due to the above explanations and the importance of flexural joints under lateral loads, in this research, flexural joints have been investigated.

Many studies have been done on the design methods of concrete shear walls so that in these methods, shear walls are considered rigid and are connected to the building frame by special connections. These connections, which act as fuses, are defined in various ways. One of these definitions is Self-Centring Rocking RC Shear Wall (SC-RRSCW). The purpose of this study is to investigate the dynamic behavior of the system under the effect of explosion load. For this study, the effect of various parameters such as the thickness of the wall enclosed in the wall, the thickness of the outer sheet, the thickness of the hardening sheets, the diameter of the longitudinal bolts, the distance from the center of the explosion to the wall and the mass of explosives are considered. This study was performed using the finite element numerical method and using Abacus software. The results show that except for the distance from the blast center and the mass of the explosives, the remaining variables have little effect on the maximum strain energy and displacement. It has also been seen that in all models, due to changes in the dimensional characteristics of structural components as well as changes in the distance and weight of explosives, none of the structural components have entered their yield zone.

Although advanced technologies have been emerged in construction projects, this industry is still mostly based on human resources. Motivation is known as one of the most important factors affecting labor productivity in construction projects which has a considerable effect on project performance. The aim of this research is to estimate the effects of labor motivation on construction projects performance using system dynamic (SD). In this research, the most important factors affecting the workforce motivation of construction projects have been identified in the first step. Then, using system dynamics (SD), a dynamic model of labor motivation in construction projects has been developed. In order to validate the model, the necessary information of developed model has been collected for a housing project. Based on the real case for validating the model, the paper discusses the potential benefits of the model, including: having a systematic and holistic view, considering dynamic the workflow and workforce motivation, identifying alternative strategies for performance improvement and simulating the reality of the projects in a virtual model.The presented model is capable of predicting the effects of motivation on labor productivity and project performance. Using this model, the necessary planning can be done to enhance the labor motivation before any action. Also, the necessary decision can be made to improve project performance in any stage of construction projects.

Double-layer scallop space domes is one of the new types of domes whose geometric shape is a function of parameters such as height to span ratio, amplitude to span ratio, arc style of sectors and style of variation in meridional direction. In these structures, the buckling behavior of the compression member has a determinative role in the collapse behavior of the structure and it is necessary to use an appropriate solution to deal with the failure of the compression member and consequently the collapse of scallop domes. One of the solutions is to replace the compression members with FLD, which can prevent collapse. In the present study, a TTFLD has been used, which has efficiency in eliminating the buckling of the compression member. First, the effect of geometric parameters on the collapse behavior of domes was investigated using the FEM and nonlinear analysis, and critical members prone to collapse in scallop domes with different geometric shapes were identified. The critical compression members were then replaced with TTFLDs, and the reinforced scallop domes were re-analyzed. By comparing the collapse behavior of domes in two cases with and without the use of FLDs, the results showed that by replacing the critical compression members with FLDs, a significant improvement in the collapse behavior of the models is achieved. The improvement is directly related to the number of devices. With increasing the ratio of amplitude to span, the ductility and bearing capacity of the domes increase. In addition, by changing the style variation from linear to parabolic in the direction of the meridian lines, the ductility and bearing capacity of the dome increase. In the change of arc style from sinusoidal to parabolic, with increasing the ratio of height to span, the bearing capacity and ductility of the scallop dome increase.

In order to better understanding the structural response of double-layer flat grids, the effects of using of a reinforced concrete (RC) topping in composite action with double-layer space-grid structures on the buckling behavior of such grids are studied. Both non-composite and composite flat grids (with and without any integral RC topping) with different span lengths are considered. The base models with span lengths of 15, 30 and 60 meters are initially selected and designed employing the well-known weight–density procedure. The finite element models are then developed in the ABAQUS environment with special consideration in the modeling procedure for beam type elements of pin connections at two ends in order to employ the capabilities of the software for buckling and post-buckling analyses. Elastic buckling analyses as-well-as non-linear analyses incorporating both the geometric and material non-linearities emphasizing the structural stability and post-buckling behavior are performed. It was found that the presence of a RC cover in composite action with double-layer flat grids can lead a decrease in the weight of steel around 29 % as-well-as maximum vertical deflection around 61 %. The presence of a RC layer can also improve the elastic buckling capacity up to 94 %. The results showed that the ultimate strength of such structures in composite state increases significantly. Finally, the RC layer can improve the post-buckling behavior which can lead an increase in the structural reliability from progressive failure or sudden loss of the structural strength.

To protect structures and save lives from destruction, a proper understanding of how impact load behave and act on structures is essential. On the other hand, steel structures are very sensitive to heat. Impact load and fire in steel structures can cause progressive failure in steel structures. Due to the fact that impact load is sometimes associated with fire, so in this study the effect of impact load on steel frames under fire conditions was investigated. For this purpose, the eight-story three-span steel frame is modelled and subjected to non-linear dynamic analysis by finite element method under impact load simultaneously with fire, and the results in terms of resistance, energy dissipation, deformation and failure in the structure are evaluated and compared. According to the results of this study, applying heat to the structure under the impact load will make the condition of the structure more critical. The results of this study show that applying heat to the steel frame will reduce the shear capacity and energy dissipation of the structure and increase the deformation and the potential for progressive failure in the structure. Applying temperature of 200 to 800 ° C on the steel bending frame will reduce the shear capacity and energy dissipation of the steel bending frame by 8 to 96% and 5.5 to 85%, respectively compared to the steel frame under ambient temperature.

Concrete structures are always affected by environmental conditions, and hot weather condition during mixing and casting impressively affect the performance of concrete. Concrete producers have been using different methods of reducing the temperature of concrete such as liquid nitrogen through direct injection of it into the drums of concrete trucks. Liquid nitrogen with having temperature of -196°C provide accurate temperature control and is not limited by the water-cement ratio as in the case of chilled water or ice. The purpose of this research was to investigate the effects of liquid nitrogen on concrete properties such as slump, setting time, compressive strength, tensile strength and flexural strength with two different curing methods. In this research, three mixtures were prepared: control, hot and LN-cooled. The temperature in control mixture was considered to be 27°C. Hot mixture which was made from materials stored for 72 hours at the desired temperature (50°C) to simulate hot weather condition, and the temperature in this mixture was obtained 40°C. The process in preparation of the LN-cooled mixture was the same with the hot mixture with the difference that, the temperature of the LN-cooled mixture was lowered to the control mixture (27°C). The results indicate that the liquid nitrogen improved the properties of concrete in hot weather and additionally the results show that the properties of concrete are relatively unaffected when cooled with liquid nitrogen to room temperature. Finally based on findings in this research, liquid nitrogen is an appropriate option in hot weather concreting.

Geopolymers are aluminosilicate materials that can be a good alternative to various types of concrete, because they help protect the environment by removing pollutants such as CO2 resulting from cement manufacturing process and significantly increase concrete durability by reducing concrete permeability. This study aims to investigate the mechanical properties and durability of geopolymer mortar cured at different temperatures. Therefore, metakaolin and ground-granulated blast-furnace slag (GGBFS) were used as the raw materials for making geopolymer mortar. Sodium hydroxide (caustic soda) with the concentration of 12 M and sodium silicate (water glass) were employed as the activator. In total, 12 curing regimes including three temperatures of 60, 75, and 90 °C and four durations of 8, 12, 18, and 24 h were applied to the samples and its impact on compressive and tensile strength and water absorption of geopolymer mortars was examined. Compressive and tensile strength and water absorption of geopolymer samples were determined after 3, 7, and 14 days. The results indicated the compressive and tensile strength of the samples increased and water absorption of the samples decreased with increasing the curing temperature and duration. Compressive strength of the samples cured at 90 °C for 24 h was at the highest level (62.4 MPa).

Today, due to the increase in terrorist attacks and the need to protect structures and infrastructure against these threats, especially explosive threats, the issue of analyzing the response of structures against these loads is one of the topics of the day. One of the important parameters in analyzing the response of structures is the nature and mode of the impact of the explosive load. This can be seen in the relation presented for explosive pressure in theoretical analyzes. According to the Friedlander relation, the blast pressure decreases exponentially over time, and various relations are proposed to calculate the decay coefficient of the exponential function (such as the Kinney-Graham method, the Ismail-Murray method, the Karlos- Solomosand method, etc). This coefficient indicates how the slope rate of the explosion wave time pressure graph decreases. In this paper, by examining other existing methods for calculating the decay parameter, a new relationship for the explosion pressure reduction parameter in the near and far range is presented; A comparison is also made between the relationship observed in this study and other relationships presented for the blast wave decay coefficient. The results showed that the decay parameter presented in this study with high accuracy can calculate the actual explosion pressure and this leads to a better analysis of structures against explosive threats. In this research, the high accuracy of the calculated relationships for the decay coefficient has been investigated in three ways: A) Based on the regression coefficient of fitted graphs, the value of R2 is close to one; B) by the comparison between the values of the calculated decay coefficient with other existing relations; C) Based on the actual blast pressure calculated in two numerical examples.

To reduce the damage and casualties caused by earthquakes, researchers made efforts to introduce seismic resistant structural systems. One of the new lateral force-resisting systems is the steel circular braced system called “Ogrid”. Previous studies shown the high energy dissipation and ductility of this system. This system has a high capacity to withstand nonlinear deformations after the formation of the first plastic hinge until collapse. In the present study, an attempt has been made to introduce a new type of this brace with different types of brace connection to beam and column and to evaluate its performance. For this purpose, the OGrid is used and different connections of the frame to the circular brace that embrace the connection of the brace to the beam and to the columns, as well as comparing the presence of friction and the absence of friction between the brace and the frame are modeled and the results are reviewed. It is found that by releasing the connection of the circular brace with I-shaped cross section to the column and creating friction between them with a coefficient of 0.5, the bearing capacity increases up to 22% compared to the restrained connection. In this case, before yielding, softening is observed in the proposed model, but after yielding compared to the model with restrained connection, better energy dissipation occurs due to deformations in the circular brace. Meanwhile, bearing capacity increases up to 8% by considering friction between the brace and increases up to 17% by considering friction between the brace and the column comparing with the released connections. On the other hand, the use of H-shaped circular brace with friction connection to the column and/or beam is not recommended due to the reduction of bearing capacity by at least 9% compared to the restrained connection.