نشریه مهندسی عمران
سال پنجاه و سوم شماره 2 (اردیبهشت 1400)

In this study, absorption of sulfates on activated aluminum industry waste (red mud) has been investigated in a batch system by OFAT method. The properties of the absorbents were analyzed using scanning electron microscope (SEM), BET surface area, X-ray diffraction (XRD), XRF. The process of sulfate absorption was done in a volume of 200 mL and a mixer speed of 150 rpm. The optimum adsorption conditions were derived for in an equilibrium time of 90 minutes, the initial concentration of 100 ppm, pH=4, the temperature of 65 ◦C and 1.5 g/L dose of the absorbent. The efficiency of sulfate removal was 73.1 percent at the optimum conditions. Thermodynamic analysis of absorption showed that the absorption process at all analyzed temperatures had occurred spontaneously. Sulfate adsorption kinetics on composite surfaces followed a pseudo second order equation and absorption isotherm had a high conformity with Langmuir, Dobinin-Radoshkovich and Temkin isotherms respectively and the maximum absorption capacity of it according to Langmuir isotherm is 13.07 mg of sulfate per gram of the absorbent.

Dynamic modulus is a fundamental property of asphalt materials that is used as a key parameter in the Mechanistic-Empirical pavement analysis and design (MEPDG). This modulus is a function of loading frequency and temperature that is sensitive to the aggregates, binder content and air voids in the mixture. Hence, the method of measurement and determination of dynamic modulus is important in pavement design and predicting its performance. There are several methods to determine dynamic modulus of asphalt mixtures. These methods include: Directly measuring in laboratory; Empirical and regression-based methods using prediction models; Modeling dynamic modulus using soft computing techniques like Artificial Neural Networks (ANN); Analytical and numerical methods for modeling the dynamic modulus; and, In-situ methods using nondestructive testing (NDT). This paper presents a comprehensive analysis of prediction models for dynamic modulus of asphalt mixtures including Witczak, Modified Witczak, Hirsch, Al-Khateeb, New Regression-based and ANN models. With reference to the literature, performance of prediction, sensitivity analysis with respect to input parameters, the effect of mixture type, and finally a comparison of goodness for these models were evaluated and reported. In addition, calibrated models for different local conditions were presented. The results show developed conventional predictive models are simple and applicable in determination of dynamic modulus of asphalt mixtures using some modifications for different mix types and local conditions.

Plastic analysis method is one of the most effective and most used methods in this field. Analysis of moment frames has been carried out with the aid of simple plastic analysis by many researchers. However, the analysis of braced frames due to the buckling of braces and the presence of axial and shear forces simultaneously in the frame members is very complex and therefore, little research has been done in this area. In this research, a special theory based on combination of mechanisms method for the plastic analysis of steel braced frames has been presented. Using the genetic algorithm, a program has been proposed to determine the failure mechanism and collapse load of the steel braced frames based on this methodology. The comparison of the results shows that the proposed formula is very accurate and can accurately determine the failure mode and its corresponding load. According to this, three arbitrary frames with different in number of stories is investigated. The collapse mechanism corresponding to the critical load factor is obtained by means of Genetic optimization algorithm and the virtual work theory. For Verification, a pushover analysis is performed for determination of collapse mode of each frame. In examples one and two which the frames are low-rise, the solution is the same, while in the third example, a slight difference is observed in the location of hinge formations. However, this error had been observed in moment frames due to the difference of the principals in the two applied analysis.

In shallow footings depending on the type of structure which is located on it, such as urban buildings, marine structures, billboards, dams and etc; it is influence by different types of loads, such as vertical, horizontal and bending moment. Depending on the type of structure, These loads can affect the shallow with different loading states. In this paper, by defining 32 experimental tests, the behavior of two circular and square shallow footings located on the sandy soil under the three loading states have been investigated and the failure envelope of each footing have been ploted in the V-H space (vertical load- horizontal load). Also, to study the effect of relative density on the failure envelope using the rainy method, sandy soil with two densities of 50 and 70 percent was developed. The results show that the failure envelope for shallow footing regardless of its shape in the V-H space, follows a second-order function, which the increase of density and consequently the increase of soil friction angle in the sandy soil has a direct impact on the failure envelope in the V-H space; the envelope has a maximum point which is equivalent to 0.3Vmax. The square footing has a bigger ultimate load than the circular footing; that’s why failure envelope in the V-H space for the square footing is larger. In general, the failure envelope in the V-H space for shallow footings depends on the ultimate load (Vmax) and soil friction angel.

Recent Iranian earthquake damages like the damages caused by the Kermanshah earthquake, revealed that RC buildings having soft story irregularities experienced more seismic vulnerability. Moreover, earthquake aftershocks increased the seismic failures in past earthquake events. But RC buildings having soft story irregularities and effects of earthquake aftershocks are not included in recent seismic design codes. In this article, for assessing the effects of soft story irregularities and also the effects of earthquake aftershocks, three, five, and eight story RC building models having intermediate sway moment frames are designed and then modeled in OPENSEES software platform and then IDA analysis are performed in order to producing the seismic fragility curves consistent with HAZUS definitions. The analytical results of seismic fragility curves revealed that the influence of soft story irregularities and also main earthquake shock-aftershock sequences on the vulnerability of considered RC building models. By increasing the height of the RC building structures, the effects of soft story irregularities and the earthquake aftershocks decreased in seismic vulnerability of the considered RC buildings.

Two-layer composite columns are a family of single-layer composite columns consisting of two circular steel tubes, which are assembled in a center and are filled with concrete. In this type of column, the important effect of concrete is that it delays local buckling of the steel skin, and that the concrete in its confined state can tolerate higher strains and tensions than the non-confined state. The advantages of two-layer composite columns, in comparison to single-layer columns, can be attributed to the lower weight of two-layer composite columns, more ductility and greater axial force strengthening. The behavior of these columns under pure axial load is of interest. Therefore, the study of the behavior of two-layer composite columns under the influence of axial load is of particular importance due to the behavior close to the reality in these columns. In this paper, the capacity of double-skin steel columns filled with concrete has been investigated using ABAQUS finite element, under the influence of axial stress. in this paper, sections were compared with changing the thickness of the layers and the diameter of the inner core and the existence and absence of concrete core. the results showed that the diameter of the tube increases with increasing the core diameter and the effective parameter in this issue is the ratio of thickness to diameter (D/t). In the discussion of the existence and absence of concrete in the core, the confinement effect has an important result and has increased the load strength capacity of the columns.

Dynamic site layout is identifying the optimum location for temporary equipment, materials, and other available tools and offices at construction sites. The Site layout is classified as a dynamic problem because the necessary equipment is changed continuously during the project lifetime. Some research investigated this issue in recent years and tried to develop various algorithm to solve such problem due to its complexity. In this study, a linear programming model is proposed to minimize total transportation cost among different parts, relocation cost for moveable facility, and transportation cost between warehouse and other parts. An invasive weed optimization algorithm is developed to solve large scale problems. Computational results show that different layout is obtained based on priorities considered for each parts so that their layout can be changed if priority is varied. To validate the proposed algorithm, its results for small scale problem is compared with results obtained from solving it in GAMS software. Results obtained from proposed algorithm for small problem reveal that they are so close to obtained from exact method. Furthermore, scenarios analysis indicates that the proposed meta heuristic algorithm is outperformed, thus the proposed IWO algorithm can be applied for solving large scale problem in real world.

In conventional seismic design methods the performance of structure has not been considered in base shear estimation and structural drift as a measure of damage will be checked at the end of design stages. This weakness of force-based design (FBD) methods causes to special attention to performance based design. Performance-based plastic design (PBPD) is one of performance based design in which the desired damage level and plastic mechanism of structure are predefined in the beginning of design procedure, to estimate internal forces. It is expected that applying PBPD ends to a structural behavior with more compliance with desired mechanism. In this paper the priority of PBPD over FBD has been investigated. The PBPD and FBD methods are applied to design of four special steel moment frames of 4, 8, 12 and 16 stories. Nonlinear behavior of designed structures have been evaluated by push-over and nonlinear time history analyses. Analyses results show that PBPD frame have mechanism mode closer to assumed mechanism mode in design procedure. Another conclusion is that PBPD frame mechanism in push-over analysis is more ductile than FBD frame. Also it concluded that in PBPD frame, plastic hinges approximately distributed uniformly all over the structure. General reason of PBPD ductility improvement, versus FBD, is strength of columns which prevent undesirable mechanism.

In blasting operations in tunnels, the occurrence of back break caused by the high energy content of explosives leads to many problems. In this project, it is tried to solve the problems caused by non-controlling blasting by controlled blasting in a pre-splitting method in one of the march tunnels of the chehel Kooreh mine in Zahedan. In order to design the blasting pattern in the tunnel section, the "theory of energy transfer" and "nitronobel (Swedish) methods" were investigated with parallel and angular holes, which ultimately led to a blast pattern based on the "energy transfer theory" with parallel holes as the final design of the selection And the control hole pattern was also designed in a "pre-splitting" manner. Finally, the proposed design was implemented in the march tunnel of the Chehel kooreh mine. Finding the results of the blasting on the basis of the proposed design showed that the face and the roof and walls were much more smooth than the blasting based operation according to the current design, which would result in more and better matching of the units with the walls and roof And preventing increased stress concentration on them. To evaluate the pre-splitting controlled blasting performance, the QCB factor is used quantitatively, after which the factor was used, the controlled blasting performance of the Chehel kooreh mine march tunnel was excellent based on the proposed design.

Rail transportation system plays an important role in the development of the economies of the countries. This system will be worn over time by operation and weather conditions and will require maintenance. One of the goals of this operation is to keep the tracks in an acceptable condition and prevent their excessive deviation from the optimal situation. Railways maintenance and repair management system has been studied and implemented to optimize activities and reduce related costs. Such systems have used various techniques to predict the future state of failure. Choosing the best maintenance policy is the goal of these systems. For policy making, the best and most cost-effective option, life-cycle cost analysis is required. In the following, with the help of the Markov prediction model, the life cycle cost (LCC) model is suggested for rail and ballast. In the end, it was found that the main costs in the ballast part are renewal costs and the track unavailability costs. The effect of renewal tonnage on these two costs is far higher than other costs. As you can see, the lowest ballast life cycle cost in the range of 100 to 150 million gross tons. In this study, assuming annual tonnage (16 million gross tonnages) as previously mentioned, it results a renewal life of about 6 to 10 years. This value for the rails is from 500 to 540 million gross tons, which is equivalent to 30 to 35 years.

By the expansion of the industrial zones, heavy metals enter the environment through industrial wastewater or leakage from storage tanks, which contaminates the soil and groundwater. The leakage of heavy metals such as lead, zinc, cadmium and etc. is not only an environmental crises, but also causes changes in soil shear resistance parameters. Type of soil and initial concentration of contamination are most prominent parameters that affect the behavior of contaminated soils.In this research, with Triaxial tests, the behavior of sandy soils with different percentages of kaolinite in two cases of non-contaminated and contaminated with lead is investigated. It can be seen that by increasing the lead concentration, the hydrogen bonding between kaolinite particles reduce and it decreases the resistance of contaminated soils. By increasing the concentration of heavy metals up to 20,000 ppm, the shear resistance of clayey sand with 15% and 25% kaolinite decreases by 18% and 24%, respectively. Then, to investigate the effect of clay minerals on contaminated soils, the shear resistance parameters of soil with kaolinite and soil with bentonite are compared. The results show, with variation of clay minerals in contaminated soils, resistance parameters have different behavior. Increasing the lead concentration in bentonite causes a flocculated structure, thus the shear strength increased. In soils with bentonite, shear strength parameters increase 20% to 30% with increasing the lead nitrate concentration

The damage detection (DD) of the bridge has always been major concerns for engineers. This paper attempts to detect damage in the continuous deck bridges by providing a new method based on acceleration responses and their instantaneous amplitudes. The DD in this paper has two steps: firstly, determining the vicinity of damage in global DD. Secondly, determining the location of damage in local DD. Then by acceleration signals, the instantaneous amplitude values of healthy and damaged structural responses extracted via HHT. Further, for accurate evaluation of the proposed method, damage locations are determined by the cross-correlation damage index (DICC). To assess the feasibility and reliability of proposed methods, several analytical models of concrete bridges of one to three-spans, as well as experimental model a simply supported steel beam, have been used. In order to consider noise pollution during data acquisition, a certain amount of noise is added to the response. The results in the analytical and experimental models showed that the proposed methods can determine the damage locations with appropriate accuracy for different damage scenarios and it could provide more exact results with a rapid estimation.

Considering the worldwide increasing rate of energy consumption and its environmental degradation effects, and considering the use of none-renewable energy sources such as the fossil fuels, consideration of energy management issues has become more important. Given the 40% share of the building industry's total energy consumption, as well as the 80% share of energy consumed during the operation period, of the total energy consumption during the life cycle of the building, attention to the areas of energy management and optimization during the operation period of the buildings can have a major impact on energy efficiency. In this research, through identifying building energy management tools and studying previous studies and assessing the effects of building energy management systems, the economic and environmental impacts of using building energy management systems on the annual energy consumption in an office building in Tehran as a case study has been investigated. The results indicate a 32 percent reduction in the energy consumption and a significant reduction in the release of the environmental pollutants in smart mode compared to the baseline. Moreover, considering the social costs associated with the emitted pollutants as well as the return period, it has been attempted to identify the factors contributing to the economic justification of using smart heating and cooling systems. According to the results, the use of smart energy management systems can be considered as an effective step in optimizing and managing energy consumption in the construction sector.

In the optimal design of the dome buildings, which is usually constructed to cover vast spaces without using the interior support, the outer shell curved shape plays an important role in the architectural approach, bearing capacity, and structural strength in vertical and lateral loads. Therefore, the designer for optimum design, in addition to beauty, should pay attention to the effect of the form of the structure on the load capacity of vertical and lateral loads in conjunction with the construction site condition. In this article the effect of arch in domes against wind is studied numerically. For this purpose, domes with fixed height – diameter proportion in type C ground and with the speed and turbulence intensity matching ASCE7 regulations are numerically simulated and the amounts of pressure coefficients (Cp) are represented on central line corresponding to wind direction and the rings around the dome with different heights including 0, 25h, 0.5h, 0.75h and h. The results of study indicate the great effects of arch height in pressure coefficient and the percent of under pressure surface and section on domes.

Structural safety can be threatened by failure of one member of the structure if it results the failure of other members of the structure. This phenomenon, which has recently attracted the attention of designers and engineers, is known progressive collapse. Progressive collapse, especially during a severe earthquakes, could threaten the general stability of structures and lead to their collapse. In this research, it has been aimed to investigate the performance of the isolated cable stayed bridges with modern Rolled-N-Cage (RNC) isolators under near-fault seismic loads and after losing a cable. In this regard, Bill Emerson isolated Cable-Stayed Bridge is implemented under three near-fault seismic events and assessed the results of the cable loss. Then, buffer mechanism of RNC isolator and its effects against preventing progressive collapse is evaluated on preventing progressive collapse of the bridge. The results indicate that the RNC isolator with activated buffer mechanism appropriately decreases the permanent displacement under near-fault seismic loads. While, not using of the RNC isolator and buffer mechanism, causes the damage propagation and progressive collapse of the bridge.

One of the best methods for improvement of clayey soils is stabilization. Traditional stabilizer such as lime, and cement have been used extensively for improving engineering properties of poor soils by earlier researcher. But using these additives involved with environmentof problems. However, lignin is a kind of natural polymer that is derived as a by-product from paper and timber processing industry, and according to government figures, annual amount of 50 million tons of lignin is discarded. This brown powder is not toxic or corrosive and does not endanger the health of humans and the environment. In this study, the effect of adding different percentages of lignin on atterberg limits, compaction properties and unconfined strength of clay is studied. Also, the effect of adding lignin with different mixing methods on resistance and soil morphology is investigated. The results of this investigation shows that the addition of lignin, generally improves the mechanical properties of soil, decreases the soil's plastic index, and enhances the strength and ductility of the soil. For soil used in this study, the optimum percentage of calcium lignosulfonate is determined as 1% of dry weight, which allowes to increase soil strength from 322 to 828 kPa after 28 days. Also, the mixing method has a significant effect on the resistance of the samples. In soil stabilization, the proper distribution of the additive among soil particles can affect the soil engineering properties. For example, mixed specimens in different ways, their maximum strength increased by up to 80%.

In many coastal areas, due to lack of fresh water, there are many limitations to use in soil stabilization. On the other, due to the extension of saline water on the surface of the earth, more studies are needed on the effects of saline water on soil improvement. Therefore, in this paper, by conducting large structural and microstructural experiments, the effect of ions in sea water on the process of chemical stabilization of clay soils with lime and nanosilica has been studied. Different amounts of lime, nanosilica, distilled water and Gulf Sea water have been used to stabilize kaolinite clay .Sample clay of kaolinite has been modified with different amounts of lime and nanosilica. In this regard, soil gradation test, Atterberg limits, pH changes of samples, compressive strength variations over time have been investigated. Also, for microstructure evaluation, X-ray diffraction analysis and scanning electron microscopy have been used. Based on the results, Unconfined Compression Strength of seawater samples has improved compared to distilled water samples. Also, when the sample were modified by 6% lime, the strength of seawater samples increased by 4% compared to distilled water samples during the 28-day processing period.

Typical braced frames, in comparison with rigid frames, have higher stiffness but they have low ductility. On the other hand, rigid frames have high ductility but due to their low lateral stiffness, they maintain large displacements throughout earthquake, which is not favorable. Furthermore, in rigid frames, the beam to column connection is a critical area that often experiences damage during earthquake. In this research, the objective is to create a lateral load-carrying system and improve the seismic performance of steel frames using placement of arch segments cut of steel plates at the corner of simple steel frames and their yielding. Due to the eccentricity, these components are subjected to an interaction of axial and flexural forces and like yeielding dampers absorb the major part of the input energy. In this study, first, hysteresis curve of arch segments made by ST37 steel was achieved using finite element software, ABAQUS. Then this damper was modeled in SAP software to create the same hysteresis curve. Then, 3, 6 and 9-story bare rigid frames and simple frames with arch segments were modeled and subjected to time-history analysis of 12 different earthquakes. Based on achieved results, maximum roof displacement and maximum story drifts of frames, in simple frames with arch segments compared to bare rigid frames in average reduced 22 and 8%, respectively. Also in simple frames with arch segments in average 46% of input energy was absorbed by arch segments that indicates relatively good performance of this system.

In order to increase the productivity of extraction of hydrocarbons reservoirs, the well is usually drilled in the direction of the minimum horizontal in situ stress and hydraulic fractures simultaneously initiate and propagate perpendicular/transverse to the wellbore. The last decade, more than 10,000 horizontal wells per year have been bored and hydraulically fractured, with up to a hundred hydraulic fractures placed in the horizontal segment of the well. The well is therefor stimulated in stages, with one stage consisting of a single pumping operation aimed at initiating and propagating simultaneously typically between3-8 cracks spaced about 10–30 m apart. When, the fluid pressure is applied on the surface of the fracture, the crack can propagate in the medium, but the pressure, induced from fluid injection, may have a negative influence on the extension of adjacent cracks which is stated as shadow or interaction stress. Certainly, an accurate estimation of interaction/shadow stress between the cracks leads to a more optimal design. In this research, the effect of the interaction between the hydraulic cracks with respect to the spacing and the number of cracks on the each other and considering position of the fractures are evaluated using the enhanced pseudo traction method. The results are shown that inner-fractures are further affected from shadow stress compared to outer-fractures. On the other hand as distance of hydraulic fractures increases, shadow stresses decrease. In the last, the results can be useful in determining the optimum number and spacing of cracks in the design of hydraulic fractures.

Antibiotics are potential pollutants that represent an important environmental problem because of their toxic effects on the food chain and aqueous streams. The goal of this study was determining the efficiency of a horizontal subsurface flow constructed wetland for a pharmaceutical pollutants antibiotic penicillin G. This study used constructed wetland pilot system for removal of penicillin G in artificial wastewater.in this study, the effects of initial concentration of wastewater, hydraulic retention time and reed on the pollutant removal efficiency were investigated. The data was analyzed using the central composite design which is the most commonly used response surface methodology design. 30 Samples of wastewater were taken from the output of constructed wetlands subsurface and tested in laboratory based on the standard reference method for experiments in water and wastewater. The results showed that reed, and retention time, has a direct relationship, and enhance them to increase efficiency. The initial concentration of wastewater is inversely related to removal efficiency. In the constructed wetland, the removal efficiency for 72 hours and different input concentrations was between 94.17% and 73.61%. Based on the study results, it can be stated that subsurface constructed wetland can remove the maximum concentration of hospital wastewater and even double this concentration with efficiency up to 90 percent, and it can be used as a proper treatment system for removal of penicillin G.

Construction wastes can be found easily and are increasing by the developing of cities. Lack of sufficient knowledge and facilities for recycling these materials causes deposition of these materials and unfavorable scenes in suburban regions. Settlement of these materials makes some troubles for building constructions on them. Prevalence of disease, growing of vermin and also the low potential of these materials for raising plants are some of the problems which are the motivation for many scientific researches about recycling of these materials. In this study first brick, gypsum and cement contained wastes were collected and then 200 samples with 3, 6 and 12 percent of cement in 4 groups with different mixture of wastes were made. Compressive and indirect tensile strength tests and the test of durability against freezing and thawing were conducted to evaluate these materials to be used in stabilized base and subgrade layers. The results show that many mixtures of these materials have sufficient compressive strength and durability to be used in base and subgrade layers according to highway construction codes.

A multi-objective optimization model has been used to provide a technically and economically optimal design. In the present study, the hydraulic design as well as the design of the groyne structures were formulated in the form of an optimization problem using the NSGA-II algorithm. The objective functions of the optimization model include simultaneously minimizing costs and maximizing sediment load transport. The first objective function is to economize the design and the second objective function is based on the definitions of river stability in order to keep the river stable. Model calibration was performed using Zanjanrood River information of bed load and scour equation. The model was investigated for sensitivity to change inlet flow parameters and longitudinal slope and its effect on output parameters and model validation with case study structural information. The optimization problem pareto front was derived based on cost and bed load functions. By comparing the five optimal possible designs (5 different design scenarios) from the pareto front with the existing design and the ideal design, the results show that the design selected among five scenarios has the closest approximation to Utopia point. The selected design suggests that the length of the groynes and the distance between them are reduced compared to the existing design and the slope of the side of the groynes is also lower than the groyne's root. The selected design has 64.95% less cost and 39.96% more sediment transport than those of the current condition.

Considering the effect of post-cracking strength and the cost of pavement construction in designing the thickness of jointed concrete pavements lead to more effective and economical pavement design. Therefore, this study evaluates the effect of the addition of macro-synthetic fibers on the thickness and construction cost of jointed concrete pavements, considering the impact of post-cracking flexural strength. The effect of polypropylene macro fibers in the amounts of 0, 1, 2, and 3 kg/m3 on changes of thickness and construction cost index of jointed concrete pavements was studied considering the modulus of rupture and equivalent flexural strength ratio of each mix design in pavement thickness design. It was observed that the addition of macro fibers reduced the thickness of jointed concrete pavement up to 25%. The highest pavement thickness reduction occurred in fiber consumption from 0 to 1 kg/m3. With the addition of more fibers, no more significant decrease in thickness occurred. The addition of fibers increased the cost index of pavement construction up to 57%. Using macro-synthetic fibers up to 1 kg/m3 caused the lowest pavement cost index's growth rate compared to other consumption contents. It was concluded that the optimal amount of macro-synthetic fibers could be determined for economic reduction of the pavement thickness by considering the growth rate of the pavement cost index, which in this study was obtained at the content of 1 kg/m3.