نشریه مهندسی عمران
سال پنجاه و دوم شماره 5 (امرداد 1399)

In recent decades, the optimal use of dam reservoirs among water resource management researchers has been of great interest. So, due to the high performance and capabilities of evolutionary algorithms, in this study, using gray wolf optimizer algorithm (GWO) to predict Urmia Shaharchay dam reservoir and present a short-term forecast program for next years. The gray wolf algorithm imitates the hierarchy of leadership and the mechanism of hunting gray wolves in nature. In this algorithm, four types of gray wolves consists of alpha, beta, delta and omega have been used to simulate the hierarchy of leadership. In this study, considering the annual planning and monthly intervals, GWO algorithm was firstly evaluated for prediction storage of Urmia shaharchay reservoir during 2006-202014 years and the results compared with ICA algorithm. The results showed that GWO algorithm, with a high accuracy of 90%, provides better results in finding optimal response, convergence rate and lower computational cost compared to ICA algorithm. The results of this study indicated that GWO algorithm, an appropriate algorithm to solve the optimal operation of dam reservoir system problem.

In this study, to improve the efficiency of TLD, a Variably Baffled Tuned Liquid Damper (VBTLD) was used. The baffles are so that they divide the tank into three equal parts when they are fully closed. Furthermore, when they are open or partially closed, they can serve as some obstacles and improve the energy dissipation parameters. When this damper meets an excitation with a specific frequency, the baffles can be tuned to make the frequency of sloshing equal to that frequency. VBTLD used in this paper could be set for frequency range from 1.73 to 3 times of a specific frequency. Compared to a simple TLD, VBTLD can be tuned to a range of frequencies and improve the performance of structure against external excitation. At first, the benchmark building was modeled in OpenSees, then the performance of the device was verified by previous test results. To examine performance of VBTLD, Tuned Mass Damper (TMD) with optimal parameters was used in this study. Results show that when the baffles are at the best angle, VBTLD with water depths of 42 mm has maximum response reduction for the numerical model subjected to the Kobe earthquake at intensities of 2, 4, 6 and 8% of the Initial maximum acceleration of the earthquake (PGA=0.87g). The improvement of structural behavior compared to the optimal mass damper at maximum acceleration are respectively 23.1, 22, 14.6 and 10.5% while for damper with water depths of 63 mm, they are respectively 8.2, 9.5, 6. 7 and 6.8%.

In this paper, a 3D coupled soil-water finite element analysis is employed to simulate the behavior of a pile group subjected to liquefaction-induced lateral spreading. The results demonstrate that the numerical model can satisfactorily simulate the response of soil including its accelerations, excess pore water pressures and displacements as well as that of the piles including displacements and bending moments. Time histories of excess pore water pressure show that liquefaction in free field soil begins at the initial stages of shaking and upon liquefaction, the amplitude of soil acceleration decreases. The maximum lateral displacement of ground is observed at the regions far from the piles. In contrary, the extent of ground displacement decreases in areas close to the piles. The numerical model was able to predict the bending moment profiles in piles and particularly their maximum values. The maximum negative bending moments occur nearby the pile cap while their maximum positive values are observed at the base of the piles. Moreover, the maximum bending moment in downslope piles of the group is about 70% greater than that in upslope one. The results of the parametric study show that the displacement of piles and the bending moment in them decrease with increasing either the flexural stiffness of piles or the relative density of the sand. Also, it is revealed that the amplitude of input acceleration is the most influencing factor affecting the pile response as increasing it by a factor of 3.5 induces 3.6 times greater bending moments in piles.

Due to the sudden increase in the price of binder in recent years and the cracking of asphalt pavements, especially in cold areas, major problems with the implementation and operation of asphalt pavement in some parts of the country can be solved with the use of roller compacted concrete pavements. Therefore, the main objective of this research is to investigate the effect of synthetic fibers on fracture resistance of roller compacted concrete pavement in different loading modes (pure mode I, pure mode II and mixed mode). For this purpose, fracture toughness of roller compacted concretes containing 0.1, 0.2 and 0.3% of a synthetic fiber named Forta was evaluated using linear elastic fracture mechanics. The results show that the effects of the fiber percentages on the mixed mode fracture toughness is very significant and adding this fiber more than 0.3% by weight of the mixture does not lead to a significant improvement of the fracture resistance. Also, by transferring from the pure mode I to pure mode II, the resistance of roller compacted concrete pavement modified with synthetic and without fibers is reduced.

ABSTRACT Morning glory spillway is built upstream of dam in the reservoir to convey water from reservoir to the downstream. The main problem of the spillway is swirling flow and vortex around spillway's axis. By increasing the submergence height, the vortex will increase which leads to reduction of flood conveyance efficiency due to decrease the discharge coefficient of the spillway. It is well known that the vortex breakers are the best for increasing the discharge coefficient of the morning glory spillway. In the present article, a physical model of morning glory spillway is designed and constructed to study the effect of number and characteristics of pyramidal vortex breakers on the discharge coefficient of the spillway. 209 experiments have been conducted in the Hydraulic Laboratory of SRBIAU, Tehran. Applying nonlinear regression analyses, empirical equations were obtained for estimating the discharge coefficient of morning glory spillway with pyramidal vortex breakers. Through comparison of results of the new equations and observed data, the determination coefficients of training and testing data for triangular and square pyramidal vortex breakers was calculated as 0.99 and 0.926, respectively. In addition, sensitivity analysis is performed to investigate the efficient variables on the discharge coefficient of morning glory spillway with pyramidal vortex breakers. Findings show that pyramidal vortex breakers in a group of six increase the discharge coefficient, significantly. The discharge coefficient performance due to pyramidal vortex breakers existence increases by 11.80% up to 16.13% compared to the non vortex breaker morning glory spillway.

By drilling borehole in the ground, the distribution of stress around it changes and stress concentration is created. If the shear stresses induced by in- situ stresses is more than rock strength, it causes a kind of failure around the borehole, which is called breakout. It has been observed that breakout failure zones are initiated and propagated in the direction of minimum in- situ stress. In this paper, by assumption of elasticit behavior of rock mass, the analytical 2D analysis of breakout failure using the Mohr-Coulomb and Hoek-Brown failure criteria is addressed and the failure zone is obtained by using these two criteria. According to the results of the mathematical model, the effective parameters in the depth and width of the breakout occurring around the borehole are depended on the mechanical properties of the materials in the medium as well as the amount and ratio of in- situ stresses. If the ratio of stresses is one, breakout failure will not occur. Also, with increasing the rock quality, the breakout depth decreases, and with decreasing rock strength and increasing the amount and ratio of stresses, the breakout area becomes larger.

History of the earthquakes occurred in Iran indicates that almost every 10 years, a destructive earthquake inflicts damages to the buildings leading to broad life and financial losses. Indeed, seismic retrofit is the process of retrospectively adding elements into the existing buildings in seismically active areas in order to enhance their resistance to the shakings during earthquake events. In doing so, one of the efficient methods is to utilize steel bracing system. To better understand the seismic performance of such systems, in this paper, RC frames retrofitted by CBF and EBF systems were subjected to 7 near-field earthquakes with varying intensities. To this end, two 10-story frames were first designed in compliance with code-based provisions and then, an IDA was conducted on them. The braces are placed in the first and fifth bays of the frame. Based on the results, retrofit of the RC frames by means of concentric and eccentric braces manages to enhance the yield capacity of the frame by 2.3 and 2times, respectively. Moreover, it was found that application of eccentric braces in RC frames, is capable of reducing the base shear by 7times, compared to the frame benefitting from concentric braces. Concerning the impact of this retrofit system on displacement demands, it was observed that when eccentric braces are employed, the roof drifts are less than those of the CBF. Lastly, it was concluded that more flexible behavior of EBF against earthquake records, increases safety and performance level of the structure in Life Safety performance level.

With regard to the development of nuclear technology in the world and the use of this technology in the industry and medical centers, the attention of countries to this topic and investment in this area has increased. In this research, concrete is made in two series. In the first series, barite powder was replaced with 10, 25, 50, 75 and 100 percent sand replacement and in the second series, barite powder with the percentages mentioned and 10 percent graphite powder was prepared. In present study, the amount of cement 400 kg/m3 and water to cement ratio of 0.4 and additives have been added to the concrete containing 10% microsilica. The mechanical properties of these concrete were determined such as compressive strength and tensile strength. Their effect was also tested as a protection against gamma radiation using the CS-137 source, and then examined by comparing the MCNP simulation code by Monte Carlo method. The results indicated that a sample containing 10% barite powder plus 10% graphite powder could be an optimal amount of protection against gamma rays. Also, the comparison of experimental results with the MCNP code showed a fairly good agreement, and the trend of increasing and decreasing it was almost the same.

It is impossible to implement projects in a risk-free environment, and the consequences of the project will affect the project's three main objectives (time, cost, quality) and usually impose costs for the project. Therefore, considering that the risks of a project are not eliminable but they are distributable, in order to optimize the objectives of a project, important and critical risks of the project should be identified and ranked, so that we can assign each risk to the employer or the contractors and monitor the consequences.Considering the Islamic Railways of Iran need for maintaining and repairing locomotives, this study introduces a fairly complete set of criteria (probability of occurrence, risk effect and probability of discovery) using multi-criteria decision making technique and SAW method has been proposed to assess all important risks related to Equipment - maintenance depot of Mashhad Railway. In this regard, two questionnaires were sent to five experts of Mashhad railway, and they evaluate and rank the identified risks through the SAW method, and finally, the risk of delay in construction (lack of integrated management system) identified as the most critical risk. Then the best response to the most critical risk was identified through the AHP model using the other questionnaire, which is “employing professional project managers and counselors familiar with management techniques.

Leakage in water distribution system is a crucial issue because of problems such as water loss, water pollution, and land subsidence. Current leakage detection methods are usually costly and time-consuming, therefore new methods have been developed based on water networks simulation. In this paper, a new method for identifying the location and amount of leakage in water distribution system based on a two-step Algorithm is introduced. The first (Stepped Algorithm) and second (Firefly Algorithm) steps for determination of leak location and amount of leakage are respectively used which is applicable for even two simultaneous leaks. The proposed method is based on the comparison of the network hydraulic simulation results and some field network data (pressure or flow or their combination). The obtained results for six examples in a looped-water network are presented. The results show that the proposed algorithm is able to locate either one leak or two simultaneous leaks and their leakage values with less than 8% error. The proposed method developed in this paper can be utilized by operators of water supply networks for identifying the position and amount of leaks.

Buried pipelines are used to transport water, liquid fuel, gas, oil, etc and they must remain in service in all circumstances such as permanent transverse ground deformation caused by slope instability. In the literature, modeling of soil-pipe interaction is carried out by using two methods of soil-equivalent springs and continuum. In this paper, numerical simulation in domain of continuum is applied to predict the behavior of the pipe embedded inside the slope. Problem modeling has been done in the FLAC 3D software by using finite difference method. The effect of parameters such as pipe diameter and thickness, width of the slope, soil adhesion and internal friction angle of soil on soil and pipe interactions were investigated. Comparison of the present numerical model with other numerical, analytical and physical models, indicates that the maximum displacement of the transverse ground and pipe occurs in the center of the area and reaches zero in the sides. Also, the anchor and force in the pipe are symmetric to the center of the model and reach a maximum value in the center. By taking steps such as increasing the diameter of the pipe, increasing the thickness of the pipe wall and reducing the angle of the slope, the displacements, tensions and strains created in the pipe can be reduced to some extent. On the other hand, the internal angle of friction of the soil and cohesion are effective in increasing the soil's resistance and also reducing the deformations in the pipe.

The supply and distribution network for drinking water is one of the key assets and infrastructure of any country and is vulnerable to terrorist attacks. Access to safe drinking water is one of the vital needs of communities.Importance of water supply facilities, sometimes in the enemy's sabotage operation, these facilities are targeted as strategic centers, which may lead to serious damage to society and sometimes security crises. Regarding this issue, in this research, a total of vulnerabilities was investigated by providing a combination of analysis and risk management for vital asset protection (RAMCAP) and Analytical Hierarchy Process (AHP) analysis of the total water infrastructure of Tehran. The present research is an applied research (extension type). In this way, a questionnaire (quantitative) method has been used for collecting and analyzing information and the research method is descriptive-analytic. The results show that the main facilities identified in the city of Tehran's water supply system, according to the criteria for the ability to discover and identify, the ability to reach the target, the weakness index, the index of resilience, the secondary damage index, the combined effects index, the most vulnerability of the Letyan dam is 0.0858, and Amir Kabir Dam with a vulnerability of 0.0779 and Taleghan dam with a vulnerability of 0.0721 are included in the next assessment. The lowest vulnerability was 0.0133 and 0.0063, respectively, based on the defined criteria for storage tanks and distribution network with vulnerability numbers.

Time-cost trade-off analysis is one of the most challenging tasks of construction project planners. Project planners face complicated multivariate, Time-Cost Optimization (TCO) problems, which require simultaneous minimization of total project duration and total project cost, while considering issues related to the optimal present value of profit. Also, the complexity of construction projects in recent years has risen up the importance of cleverly management in cases of project financing and scheduling. There are choices and limits that make it difficult to project planners to develop a proper financing plan considering project time status. Therefore, the methods of financing affect the project plan. Therefore, a skilled planner should consider various effective parameters for scheduling projects. This study presents a hybrid meta-heuristic algorithms to solve a multi-objective optimization problem in construction project planning and finance. First, the model is compared with common meta-heuristic algorithms in a simple case study. Then it is applied to a complex case study and it shows the optimal solutions which have time, cost and net present value of profit. It is shown that the proposed model is superior to the existing optimization algorithms to find better project planning solutions with less total project duration, less total project cost, and optimal profit in the construction project problems. The cumulative results are shown in a three-dimensional Pareto front. Also, the proposed model improves the solutions through generations and provide optimal solutions in an acceptable processing time.

One of the most common damages in asphalt mixtures is due to the destructive effects of moisture on the cohesion of asphalt binder and adhesion of asphalt binder-aggregate which is called moisture damage. There are several different approaches for improving adhesion and reducing moisture sensitivity in asphalt mixtures. One convenient approach is modifying the asphalt binder with suitable agents. In this research, the effects of two types of nanomaterials in two different percentages (nano ZNO and SiO2), two types of aggregates (granite and limestone), and one base asphalt binder were evaluated. To assess the effect of nanomaterials, the indirect tensile cyclyc loading (similar to resilient modulus test) in dry and wet conditions and surface free energy (SFE) tests have been used. Moisture sensitivity index, which is the percentage of the aggregate surface exposed to water as calculated by using the measured SFE and indirect tensile cyclic results, was considered an index for the moisture susceptibility of mixtures. Mechanicaltest results used in this study show that using nanomaterials significantly improves the moisture strength of samples made with the modified asphalt binder in comparison with the control samples. Results of surface free energy theory show that the nanomaterials increase the cohesion free energy of the asphalt binder that decreases the probability of the occurrence of cohesion failure in the mastic. Also, nanomaterials decrease the acid component and increase the base component of surface free energy of the asphalt binder which increases its adhesion with the aggregates that are prone to moisture damage.

Selecting the appropriate model size is a challenging issue in the numerical modelling of groundwater inflow into underground excavation. This issue was studied in this paper by presenting a methodology for selecting appropriate domain size for numerical modeling of groundwater inflow into tunnel that is excavated inside of semi-infinite aquifer. To reach this goal, first, a dimensionless factor, so-called normalized rate of inflow variation (NRIV), was defined in cooperation with its limit value, so-called acceptable level of variation (ALV). Then, the appropriate or suitable domain size (SDS) of numerical model was determined based on the NRIV and ALV. The applicability of suggested methodology was evaluated for the results of wide range geometrical parameter of tunnel (including different tunnel radiuses and depths) and different flow domain sizes. The results of this study indicate that the required domain size for numerical modelling of groundwater inflow into tunnel increase nonlinearly for larger and deeper tunnels. Moreover, the required domain size increases to 1.8 times by decreasing the level of ALV from 0.0005 to 0.0001, where the relative accuracy of results has only increased up to 4%. Since the larger domain size requires much computational difficulties and insignificant accuracy, the ALV in the level of 0.0005 is suggested for practical numerical modelling of groundwater inflow into tunnels.

Cement production is one of the most important sources of CO2 emission in the world and an energetically demanding process. Therefore, the replacement of a part of it with cheaper and environmentally friendly materials such as zeolite is of great importance. Small strain shear modulus (G0) of soil is an important parameter in many aspects of geotechnical engineering. In the present study, a series of bender element tests on loose sandy soils grouted with zeolite and cement was conducted to investigate the effects of cementation on the G0 of them. The results showed that the G0 of grouted samples increased with an increase in zeolite content up to 30%. After this (Z30), any increase in the zeolite content reduced the G0. Also, in all W/CM and Z, the G0, decreased with increase in the sand grain size. The G0 corresponding to Z30 for D11 sand (the smallest particles) samples grouted with suspension having W/CM of 3, 5 and 7 is, respectively, 21.7, 16.7 and 12.5 times that of pore sand. The minimum G0 is observed in samples grouted with Z90 and W/CM of 7, which is 2.16, 1.2 and 1.19 times the G0 of corresponding unstabilized sands for D11, D1 and D2 sands, respectively. By replacing 50-60% cement with zeolite in the grouting suspension, no reduction in the G0 of the grouted specimens compared to specimens grouted with cement is achieved. Therefore, from an economic and environmental point of view the replacing this amount of cement with zeolite is important.

Improvement of the pavement surface texture charactristics and drainage quality is an important issue in the field of increasing roads safety and reducing the rate of accidents, especially in rainy weather conditions. The assessment of the pavement surface features and its relation with the accident rate is a common research topic, but no extensive research has been carried out on the evaluation of the pavement surface drainage. In this research, a system has been developed to assess the surface drainage of the pavements. For this purpose, a hardware is designed which is able to saturate the surface and capture the drainage process under constant conditions without the effects of environmental factors. The basis of the presented system is based on digital image processing techniques. Using image processing methods, three time-related indexes including Entropy,Energy and pixels proportion have been determined for the assessment of surface drainage quality of the pavement. Providing a proper combination of the indexes, the pavements are classified as appropriate, acceptable and inappropriate in terms of surface drainage performance using C5.0 datamining algorithm. The validation of the results of the proposed system shows that this system can evaluate the surface drainage situation with 95.7% accuracy. The presented system results can be used in the pavement management systems at project and network levels as a suitable measure for the evaluation of pavement safety in the rainy conditions as well as improving roads safety.

The techniques and types of materials used in construction sites are very important considering mechanical, environmental and economical issues. Separating different parts of a building from each other and protect the interior space from outside environment requires effective walls. In order to satisfy needs such as lowering cost, increasing speed and minimizing overall energy consumption of buildings, construction material industries produce and introduce different types of separating walls for buildings. This research was conducted to assess the environmental, economical, technical and operational impacts of different types of separating walls. Five different types of walls, including solid clay (SC) bricks, hollow clay (HC) blocks, autoclaved aerated concrete (AAC) blocks, three-dimensional (3D) sandwich panels and gypsum boards were investigated in this regard. The goal was to find the most effective type of separating wall among the choices investigated. Each of the fore mentioned criteria were divided into several sub-criteria, and the Analytical Hierarchy Process (AHP), as one of the best-known multi-criteria decision-making methods, was implemented in the assessments. Evaluations were based on both qualitative and quantitative criteria. Technical data and information were used for quantitative criteria and different types questionnaires were developed regarding the qualitative criteria. The results of this study, on the basis of all criteria, showed that the gypsum board with the relative priority value of 0.368, is the best choice between the assessed separating walls. The calculated relative priority values of AAC blocks, HC blocks, SC bricks, and 3D panels were 0.177, 0.152, 0.151 and 0.144 respectively.