نشریه مهندسی عمران
سال پنجاه و چهارم شماره 6 (شهریور 1401)

The purpose of this paper is to study some properties of building materials made with plaster (commercial - CGP and recycled - RGP)and waste (red - RC, and chinese - PW ceramics)using Press pressure. The brick is made with a solid mass composition containing 50 wt% of cohesive material and 50 wt% of waste material and is proportional to the amount of dry water / dry powder (0.22). According to these findings, there are various industrial waste materials such as plaster recycling, as well as materials from red (RC)and chinese waste (PW)waste. In this study, specimens were cast before using a single - core inquiry (10 kN)before obtaining a uniaxial compressive strength (10 kN). After treatment and characterization of specimens, the stress and flexural strength, porosity and microstructure of samples were investigated. The results of the compressive strength were in the range of 12MPa to 35MPa. The ratio of solid water / mass and the applied force applied to the uniaxial compressive stress before getting caught in reducing the porosity of specimens had a significant effect on their mechanical properties. The results show that this increase of waste material will cause a better quality of brick building materials.

Nowadays, explosion phenomenon has been considered by structural engineers due to the increase of terrorist attacks and unforeseen events. Therefore, the calculation of the final dynamic loads resulting from these loadings should be considered as a criterion in order to design structures and protect military buildings. In this investigation, the behavior of pumice hybrid-fiber reinforced concrete slabs under blast loading was assessed. To evaluate the performance of pumice hybrid-fiber reinforced concrete, contact explosion test on slabs with dimensions 100×100×10 cm was conducted. Six slabs including one unreinforced concrete slab and five fiber reinforced concrete slabs were prepared. Also, C4 explosive material was used to investigate different failure modes of slabs. The results showed that the addition of various types of fibers improved the behavior of slabs. The results showed that the addition of various types of fibers improved the behavior of slabs .Also, it is concluded that replacement of cement and steel fibers with pumice and polyolefin fibers, respectively, led to a slight increment in number and extent of cracks, however, the costs were significantly decreased.

Given that one of the most concrete and concrete construction materials with suitable compressive strength, ductility, tensile and flexural strength is low. For this purpose, in the past few years by adding fiber to fiber reinforced concrete and concrete construction, greatly improve the weaknesses. The purpose of this study is to investigate the effect of different fibers on the flexural behavior of reinforced concrete beams made with natural and recycled aggregates. In this research, 12 samples of reinforced concrete beams in two groups (6 beams made of natural aggregate and 6 beams made of recycled aggregate) were made in real scale with dimensions of 150×50×20 centimeters, which The reinforcement details of all the beams were the same and three types of steel fibers, polypropylene and Kortta were used separately and hybrid in the construction of the beams. Four-point flexural strength test was performed on the samples. Fracture mode, fracture behavior as well as absorbed energy parameters, ductility and final load capacity of beams made with natural and recycled aggregates were investigated. The results showed that the addition of hybrid fibers had a greater effect on improving the above parameters than separate fibers and also the flexural behavior of recycled samples with hybrid fibers could be closer to natural samples with separate fibers.

Low compressive and tensile strength, high water absorption of the AAC leading to excessive absorption of the mortar’s water as well as low impact resistance, are the technical and executive drawbacks of using the ACC in the construction projects. To address these issues, in this paper, it has been attempted to replace cement with Nano-Graphene (NG) at ratios of 0.2, 0.4 and 0.8% and study mechanical properties of the modified NG-incorporated AAC, using the compressive and tensile strength tests (cylindrical specimens with diameter and height of 10 and 20cm, respectively), impact resistance and water absorption tests (cubic specimens with size of 15cm) as well as SEM and XRD tests. Based on the results, replacement of cement with NG, could enhance the compressive, tensile strength and impact resistance by 45, 81 and 130% compared to the control specimen. Moreover, it was observed that inclusion of the NG reduced the water absorption up to 61%. Finally, the SEM results revealed that incorporation of the NG strengthened the bonds between the compounds and the particles were downsized by 30%.

One of the conventional recycling methods of asphalt mixture is the reuse of reclaimed asphalt with cement as a method for treatment of the base layer and its replacement in pavement layers. In this research, cold recycled asphalt mixture with using emulsified asphalt binder has been investigated through response surface method. In this regard, the technical and economical aspects of fabricated samples of recycled cold asphalt mixtures using crushed asphalt materials, cationic emulsified binder and Portland cement (type II) were investigated. Marshal strength and flow, bulk specific gravity and air voids of mixture were determined by experiments. By performing analysis of variance on the proposed models and determining the effective parameters, mathematical equations between independent and dependent parameters were developed and the effect of the parameters was investigated. Finally, an optimum mix design, which has 60% desirability, was suggested for cold recycled asphalt. Results showed that emulsified binder and cement content have significant effect on the marshal strength. Also, water exhibit a significant effect on the flow of asphalt mixtures.

One of the solutions to deal with improper temporal and spatial distribution of water resources problems is the optimal use of dam reservoirs. Reservoir systems analyze, properly, manages and properly utilizes water resources and tries to design water resources systems in such a way that specific purpose such as hydropower generation, drinking water supply and agriculture, control of destructive floods, according to a set of Implement the constraints optimally. For this purpose, in this study, the objective function of minimizing the total power of the difference between the demand of agriculture and release has been used to solve the problem of optimizing the operation of the Amirkabir reservoir. The purpose of this study was to evaluate the performance of single-objective versions of algorithms such as multi-verse optimizer and genetic algorithm, as well as the performance of a combination of these two algorithms (MVGA). The results of the study of meta-heuristic algorithms indicated that among the multi-verse, genetic algorithm and MVGA algorithm, the MVGA algorithm similar to GA has a lower number of iterations with objective function values of 24.29 and 24.22, respectively, better than the MVO algorithm with objective function values 29.14. The results of this study showed that to increase the efficiency of one algorithm, it can be combined with another algorithm. In this study, the combination of genetic algorithm with multi-world algorithm has improved the performance of multi-world algorithm by 16.64%.

The study of cyclic behavior of sandy soils during seismic load application has been one of the most important geotechnical issues in previous decades and is still one of the most geotechnical challenging seismic aspects among researchers. In the earthquake state, the soil is under initial constant normal stress and the shear stresses due to the earthquake on the sample change direction regularly, and as a result, the directions of cyclic changing the main effective stresses the soil sample is accessible. In this research, cyclic simple shear responses for different combinations of clean silicate sandy soil and non-plastic fine content of silt have been evaluated in order to understand such soils. The experiments were performed at cyclic stress ratios of 0.15 (CSR = 0.15) and confine pressures of 50, 100 and 150 KPa. Constant volume cyclic Simple shear tests on clean sand samples have shown that by increasing the non-plastic fines content to 30% by weight of the sample, the shear strain decreases and then the shear strain increases but the shear strain of the sand with 40% silt is less than the clean sand. The results showed that the liquefaction resistance of clean sand soil under the same conditions is higher than the silty sand soil. Also, with increasing confine pressure, the soil liquefaction resistance increases in all silt percentages.

Granular materials used today in many engineering projects such as rockfill dams and railway have a wide variety of shapes. This shape variation ranges from very sharp to perfectly rounded.  The shape of the aggregates affects the mechanical properties of the grain, including fracture strength and internal friction angle. As a result, the mechanical behavior of the mass of granular materials depends on the shape of the grains. In order to investigate the effect of this property, different types of grains in the shapes of spheres, cylinders, cubes and pyramids, which include a wide range of shapes of natural aggregates, were made artificially in the size range of 1.5 to 2.0 cm. Small-scale uniaxial compressibility tests were performed on each of the grain shapes under the same conditions including initial porosity ratio and maximum stress and after each experiment, the stress-strain behavior and the amount of breakage were obtained using Hardin breakage factor. Then, the results evaluated using an analytical model proposed by McDowell et al. based on the law of conservation of energy. This model has 7 parameters which depend on the initial conditions of the grains, material, shape, size and fracture strength of the grains. Comparison and evaluation of the results indicates the ability of the analytical model in predicting the compressibility behavior of pyramidal grains. As the grains become angular, the compressibility and breakage of the materials increase. Also, with increasing the fracture surface energy of material, the effect of shape on compressibility decreases.

The Traffic assignment problem in the transport networks is formulated as a convex optimization problem using simplifier assumptions. Link based, path based and bush based algorithms have been presented to solve this problem, among which the link based algorithm have found more applications thanks to their low memory requirements. The link based algorithm of Frank-Wolf (FW) is yet amongst the most popular assignment algorithms, because of its simplicity as well as high convergence speed during the initial iterations. However, the low convergence rate of this algorithm near the optimal solution has driven many studies that focus on modifying the FW search direction, resulted in newer link based algorithms. Among them are conjugate direction algorithms which are more effective and simply implementable. These algorithms include PARTAN, conjugate FW (CFW) and bi-conjugate FW (BFW). This paper uses the Chicago Regional and Sioux-Falls test networks to make direct comparisons among these algorithms with respect to the CPU time and iteration number needed to reach various accurate solutions. The results for Chicago show that, compared with the FW algorithm, the three algorithms CFW, PARTAN increase the convergence speed to the relative error of 10-5 (i.e. a stable solution) by about 89, 72 and 63%, respectively, while only the BFW can reach to a 10-6 relative error. Comparing the results from Sioux-Fall with those of Chicago demonstrate that the performance of the conjugate directions Algorithms improves as network size decreases.

Using steel braces is regarded as one of the significant methods for retrofitting and seismic rehabilitating of reinforced concrete frames. Thanks to its easy implementation, economic considerations and appropriate seismic retrofitting performance against lateral forces, this system has received more attention from researchers in comparison with other seismic resistant systems. In this type of structural system, the connection properties are of high significance and they can play a significant role on the obtained results including ductility, resistance, stiffness, etc. The detailed behavior and performance of this type of connection have received less attention from researcher; hence, it is regarded as an under-researched issue. In the present study, we addressed this research gap; we made an effort to comprehensively explore and investigate this issue. ABAQUS finite element software was applied for modeling and numerical analysis; a total of 8 models were analyzed and investigated which were categorized into 3 different groups with respect to the type of steel brace connection to the reinforced concrete frame. These connections include steel bolts and plates, steel jacket and steel box which were modeled and discussed under different conditions within each group. Nonlinear analysis of samples indicated that the connection of steel bracing to the concrete frame by penetrating bolts in concrete and steel plates led to significant enhancement of stiffness, resistance and ductility. Furthermore, these reinforcements have maximum energy dissipation, minimum concrete frame cracking and steel consumption reduction in joints.

The presence of petroleum products (crude oil pollutions) in clay with low limit liquid (CL) due to physical and chemical processes causes changes in the stress-strain curve, wedge rupture, plastic zone and, strain energy compared to unpolluted soil. These changes often reduce the safety factor against failure, increase the plastic zone, and Decreased soil slope stability. So far, the effect of crude oil pollution on soil shear strength parameters has been tested by direct shear test and the modulus of subgrade reaction has been tested by plate loading test for different types of clay and sandy soils. In this study, the effect of changes in crude oil pollution in the range of 0 to 16% (0-4%-8%-12%-16%) on clay soil slope stability has been done by numerical modeling of finite element method in ABAQUS software. The height of the clay slopes is 10 m, 13 m and, 16 m and, the slope angle of the slope is 53 degrees. The results of this study show that increasing crude oil pollution reduces slope stability. It is predicted that with the increase of crude oil pollution in the range of 0 to 16%, the safety factor of clay slope stability will decrease by 72%. Also, increasing only 4% of crude oil pollution in clay soil slope (12% to 16% of crude oil pollution), causes a 2 to 3 times increase in horizontal displacement and a 3 to 4 times increase in vertical displacement.

Robust estimation of fundamental elastic period of the buildings is essential for obtaining realistic seismic base shear. Seismic design codes provide a variety of equations to calculate the fundamental elastic period of vibration for steel moment frame buildings. The empirical equations are mainly based on the building height and does not take into account the effects of irregularity and soil-structure interaction. In this paper, an empirical predictive equation is developed to estimate the fundamental elastic period of steel moment frames. The predictive equation includes parameters that represent irregularity effects and soil-structure interaction . The database used in this study consists architectural and geotechnical data for 45 building cases. The proposed predictive equation shows satisfactory accuracy. The predicted results are then compared to the values obtained from Iranian 2800 seismic design code, ASCE7-16 and UBC-97. The proposed predictive equation is also verified by 10 fundamental elastic periods obtained from analytical models. The fundamental elastic period obtained using the predictive equations are specifically more accurate for mid- and high-rise buildings compared to seismic design codes. The values obtained from seismic codes are well below the realistic values for the buildings.

One of the most widely used techniques in the rehabilitation of concrete structures is the application of post-installed adhesive anchors in concrete. The main purpose of this study is to evaluate the efficiency and safety of post-installed adhesive anchors under domestic Iranian workshop conditions. This study focuses on the effects of parameters such as adhesives used in Iran, embedment depth, edge distance, and either single or group behavior of post-installed anchors on both reinforced and plain concrete members. The design procedure is in accordance with ACI 318-19 guidelines. For this purpose, eight tension and eight shear tests were performed on post-installed adhesive anchors in reinforced and plain concrete members to evaluate the types of failure and the factors affecting its behavior. The results show that by increasing embedment depth and distance from the edge of the concrete member, respectively, both tensile and shear capacities increase. In group installation, by reducing the rebar spacing, the nominal bond strength between adhesive and concrete decreases due to the initiation of cracks between two rebars. Finally, the comparison of experimental results with ACI 318-19 equations showed that the code predicts the tensile and shear failure capacities with safety factors of at least 1.5 and 2, respectively.

The relatively low compressive strength and negligible tensile resistance aligned with inadequate ductility are considered as major drawbacks of earthen buildings leading to their vulnerability against the gravity and lateral loading including seismic-induced forces. In this study, the possibility of using palm fibers as a natural reinforcement in order to improve the mechanical properties of adobe bricks including compressive strength, tensile strength and ductility are evaluated. To this end, adobe bricks with dimensions of 200 × 200 × 50 mm3 are made by adding palm fibers of 0, 0.25, 0.5, 0.75, and 1% of soil weight. Compressive properties are determined using cubic samples with dimensions of 50 × 50 × 50 mm3 cut from the full-scale adobe bricks while the ductility factor is obtained using the compressive stress-strain curves. To evaluate the tensile strength of specimens, three point flexural tests are conducted on prismatic specimens of 50 × 50 × 200 mm3 cut from the full-scale adobe bricks. The obtained results indicated adding 0.25% palm fibers can add the compressive strength of adobe bricks by 50% and adding 1% palm fiber can twice the tensile strength. Further, based on the analysis of the results obtained from the compressive and three-point bending tests, analytical expressions are proposed to estimate the compressive and tensile strengths of adobe bricks reinforced by palm fiber (from 0 to 1%).

The effluent of the beverage industry has high amounts of organic compounds, and biological treatment methods are very common in this field. By applying efficient methods to treat the effluent of the beverage industry, it is possible to provide the ground for the consumption of treated effluent in other places. The general purpose of the present study is to evaluate the efficiency of the activated sludge process with extensive aeration and sludge return for wastewater treatment of the beverage industry. The present study lasted for 60 days. After making a laboratory pilot, for evaluation, first the pilot was fed with sugar and then synthetic effluent was prepared and transferred to the pilot. The organic load has increased from 1.03 kgCOD/m3.d to 1.93 kgCOD/m3.d. In this study, the COD parameter was used to measure the effluent pollution of the beverage industry and the working cycle was 24 hours. The results of the mentioned process showed that with the final organic loading at the rate of 1.93 kgCOD/m3.d, the removal efficiency was equal to 90%. By examining the hydraulic retention times of 6, 12, 18 and 24 hours, the highest efficiency in the retention time of 24 hours was obtained and in the research process, the pH was between 7 and 9 and the temperature was in the mesophilic range. Therefore, it can be concluded that the process of activated sludge with extensive aeration and sludge return is effective in treating the effluent of beverage industries with medium organic load.

One of the methods of stabilizing embankments is the implementation of anchored walls, which is one of the common methods of restraining types of walls is the use of anchor plates. Also, Back to Back Mechanically Stabilized earth walls is one of the types of so-called mechanically stabilized earth walls with complex geometry, whereas their use has been less the subject of research. So far, no special research has been done to investigate and analyze the behavior of anchored back-to-back sheet-pile walls with anchor plates under a load of shallow foundations and the behavior and interaction of two walls with each other and the interaction of sliding surfaces of two walls and sliding surfaces of shear failure of subsurface soil. Since the effect of the interaction of two back-to-back walls with each other and the loading plate(shallow foundation model) with two walls due to the interference of their failure surfaces, strongly affects the load-bearing capacity and stability of walls, so in this article by physical modeling, The effect of horizontal distance between two walls, dimensions of loading plate on stability, load-bearing capacity and soil failure model under foundations and walls have been investigated and analyzed. In order to survey the shape, form and how the critical failure curves of the embankment behind the walls intersect, the Particles Image Velocimetry technique has been used. The results show that the effective distance between the two back-to-back anchor plates walls is about 130-120 cm, equivalent to 20-30 cm distance of their anchor plate.

The optimal design and construction of sewage networks have always been considered by researchers and experts due to the very high costs of implementing this infrastructure. Being consisted of various variables and subjected to complex constraints, conventional mathematical optimization procedures are unlikely to be able to solve sewage network optimization problems. Thus, utilizing meta-heuristic optimization algorithms is a must to tackle these problems. The shuffled frog leaping algorithm (SFLA) is one of the new meta-heuristic algorithms which has shown its ability to solve a large number of optimization problems. In this research, the capability of the SFLA in solving the problem of optimal design of sewage networks has been investigated. The diameter of the pipes as discrete decision variables and the depth of pipe placement as continuous decision variables were simultaneously considered in this study as the unknowns. To this end, three sewage networks with 13, 41, and 65 decision variables have been selected as case studies. Various technical, operational, and hydraulic constraints are controlled by defining appropriate penalty functions. The results showed that for case studies 1 and 3, the SFLA decreased the minimum construction costs derived by GA, PSO, and SCE algorithms by 0.43 and 3.2 percent respectively, and for the second case study, with the less number of function evaluations, SFLA has reached the equal objective function compared to other algorithms.

Using fibers to reduce cracks and increase the joint spacing of concrete slabs has become popular in the concrete pavements of airports and freeways recently. However, their durability behavior against acid rain has been less studied. The purpose of this paper is to investigate the mechanical performance and durability of concrete reinforced with polyolefin and polypropylene fibers containing 15% of pozzolanic materials (pumice or metakaolin) instead of Portland type II cement. In this regard, compressive and flexural strength were measured to investigate the mechanical behavior of the studied mixtures at different ages. On the other hand, chemical resistance against acid rain simulated was investigated through the visual examination and weight loss, and also microstructural analysis was performed by SEM analysis and CT scan testing. Based on these results, the addition of both of these fibers in concrete reduces the compressive strength of concretes compared to the similar content in the control concrete. On the contrary, fibers increased the flexural strength, which became much more significant with the addition of pozzolanic materials. However, ordinary and fibrous concrete containing pozzolanic materials showed a weak performance against acid rain. Based on the results of CT scan and SEM analysis, concretes containing pozzolanic materials have a porous structure. Besides, the ratio of calcium to silicon in them is much lower than the control concrete due to decalcification reactions caused by acid attacks.

Steel is one of the most widely used materials in structures due to its high strength and speed of execution. One of the most important disadvantages of steel is corrosion damage and low fire resistance. When the temperature of the steel exceeds a certain value, its strength decreases to a great extent; therefore, in this paper, the performance of canned steel specimens with corrosion and at different temperatures has been investigated. Thus, the corrosion weakness is considered as a perforation and the columns with different positions of the perforation in 6 states and the application of heat in 5 different states 20, 100, 250, 500, and 700 are examined and the load-displacement diagrams of each column under axial loading are presented. Then, in order to improve the behavior of the damaged specimens by the two mentioned factors, the perforation location has been reinforced and reinforced using a steel sheet and axial loading has been done in two-temperature states of 20 and 700 ° C. The results show that: with increasing temperature, the bearing capacity of unreinforced columns has decreased and this reduction has reached up to about 15% for perforated specimens and up to about 35% for perforated specimens according to the type of perforation. Also, in steel columns reinforced with steel sheets, the bearing capacity has increased by about 5 to 15 percent (depending on the perforation).

Today, the semi-circular bending (SCB) test has become a common method and used in studying the mechanical behavior of asphalt mixtures. According to the regulations, this test has specified laboratory conditions such as sample geometry, test temperature and a certain loading rate. However, in addition to providing these conditions for SCB testing, the shape and type of supports used in the experiment are less considered and they do not have an integrated type and shape, which may cause differences in laboratory results. Therefore, in this study, the effects of 5 different support configurations on important parameters of fracture mechanics at intermediate temperatures was investigated by considering the coefficient of variation (CV). The used loading rate was selected 5 mm/min in which the asphalt samples were subjected to uniform static loading under mode I. The experimental results showed that the selection of support type has a direct influence on the fracture mechanic parameters, while the selection of the wrong support type may cause significant error in the test results. Nevertheless, the friction between the sample and the support causes more dispersion in the test results and could reduce its repeatability. For this purpose, it could be recommended not to use rigid supports that have considerable friction with the sample. Finally, considering specific laboratory conditions for the SCB test (i.e., sample geometry, test temperature and specific loading rate), support No. 1 was selected as the most suitable support with high repeatability of the results.