نشریه مهندسی عمران
سال پنجاه و سوم شماره 6 (شهریور 1400)

In this study, the effects of diameter and location of drain pipes in uplift force, exit hydraulic gradient and seepage in the foundation of gravity dams are investigated. For this purpose, the SEEP/W software as a subgroup of Geo-Studio software is implemented and foundation of a gravity dam is simulated. The results showed that the existence of drain pipes under the gravity dam, reduce 4, 6, and 9 times of uplift force, exit hydraulic gradient and seepage respectively. Installation of two drain pipes with 0.25L distance from each other and in depth of 0.26D near the dam heel, presents more suitable position respect to uplift force reduction (D is the pervious foundation depth). Also, by defining the best position for the location of drain pipes, it was observed that drainage pipes in these situations reduce 41-67% in the volume of the studied dam and increase the safety factor up to 2 to 3 times against the dam overturning. It is also found that the drainage pipe diameter has less effect on uplift force, exit hydraulic gradient and seepage and and is controlled by the rules of the executive. For validation, the numerical method used in this study was compared with the laboratory method by others and a suitable match was observed.

Dam break is a very important problem due to its effects on economy, security, human causalties and environmental consequences. In this study, 3D flow due to dam break over the porous substrate is numerically simulated and the effect of porosity, permeability and thickness of the porous bed and the water depth in the porous substrate are investigated. Classic models of dam break over a rigid bed and water infiltration through porous media were studied and results of the numerical simulations are compared with existing laboratory data. Validation of the results is performed by comparing the water surface profiles and wave front position with dam break on rigid and porous bed. Results showed that, due to the effect of dynamic wave in the initial stage of dam break, a local peak occurs in the flood hydrograph. The presence of porous bed reduces the acceleration of the flood wave relative to the flow over the solid bed and it decreases with the increase of the permeability of the bed. By increasing the permeability of the bed, the slope of the ascending limb of the flood hydrograph and the peak discharge drops. Furthermore, if the depth and permeability of the bed is such that the intrusive flow reaches the rigid substrate under the porous bed, saturation of the porous bed, results in a sharp increase in the slope of the flood hydrograph. The maximum values of peak discharge at the end of the channel with porous bed occurred in saturated porous bed conditions.

This research investigates the collapse responses of a concrete moment frame considering modeling uncertainties. These modeling uncertainties are considered for evaluating a collapse response related to the modified Ibarra-Krawinkler moment-rotation parameters for beam and column elements of a given structure. To analyze these uncertainties, the correlations between the model parameters in one component and between two structural components were considered. Latin Hypercube Sampling (LHS) method was employed to produce independent random variables. Moreover, Cholesky decomposition was adopted to produce correlated random variables. Performing 281 simulations for the uncertainties involved considering their inter-correlations, incremental dynamic analysis (IDA) was done using 44 far-field accelerograms to determine structural collapse responses. Collapse responses of each simulation, including mean collapse capacity, mean collapse drift, and mean annual frequency, were obtained. Then, the collapse responses were predicted using the response surface method and artificial neural network. The results show that the Correlation coefficients (R) between the target data resulted from incremental dynamic analysis (IDA), output data resulted from response surface method (RSM), and artificial neural network (ANN) were obtained for the collapse responses above 0.98. The maximum prediction errors for mean collapse capacity and mean collapse drift are less than 5% and for mean annual frequency less than 10% under response surface method (RSM), and artificial neural network (ANN).

Implementation of soil-cement columns using deep mixing method is an effective way to deal with problems caused by low resistance of coastal problematic soils. What is common in the implementation of these columns in the engineering community is the need to use fresh water to make the grout used in these columns. This, both from the point of view of its supply and transportation costs, and from the lack of fresh water in many areas, imposes high costs on projects and time delays. However, prior to the final cement retention, the saline water present in the environments of the columns was mixed with the fresh water in the grout as they were built deep in the soil. Investigating the feasibility of using sea water in mixing these columns and evaluating the behavior of soil-cement samples in marine conditions has received little attention. In this study, it has been attempted to investigate the effective factors in the grout mixing scheme including water salinity, cement percentage, water-cement ratio and processing time on uniaxial compressive strength and sand-cement tensile strength. SEM images were also microstructurally evaluated for sample behavior. The results show that in the 15% to 25% cement content, the use of sea water in grout production does not decrease the strength of sand-cement samples in marine environment. The obtained compressive strength range for sand-cement samples made with seawater is approximately (1.5 to 6) MPa and the tensile to compressive strength ratio of these samples is in the range (0.15 to 0.3).

In this paper, the damage detection of single tapered pole is studied. Structural damage has been identified using the vibration method. In this method, the APSO was used to detect the location and severity of the damage. The objective function for detecting damages, is a correlation coefficient based on natural frequencies. In order to accelerate the calculation of the natural frequencies of the structure, iterative method was used. In this paper, the damage is applied to the structure, by reduction of the stiffness matrix of the element in a finite element modeling and also in order to match the real situation, error in frequency is considered. To evaluate the efficiency and robustness of the proposed method in detecting damage of tapered poles, two numerical examples, including a police surveillance camera pole and a water storage pole under different damaged scenarios, are examined. In first and second example, structures are divided by 15 and 25 elements, respectively, with uniform moment of inertia. The results show that the proposed method is capable of detecting both location and severity of the damage properly, despite the complexity of some damage scenarios. Therefore, the algorithm can be used to detect the damage of other structures.

In asphalt pavement hot recycling, reclaimed asphalt pavements called "RAP" and aged bitumen extracted from them are known as reclaimed asphalt binder (RAB). In this study, the performance of RAB-containing binder compounds with different percentages of recycled bitumen (0, 25%and 50%) and RAP-containing asphalt mixtures with varying contents of the RAP (0, 25% and 50%) were compared in two conditions (with and without a rejuvenating agent). The main purpose of this study was to evaluate the relationship between bitumen’s performance parameters and asphalt mixture’s performance parameters. Therefore, the correlation between the parameters obtained from the fatigue and the rutting tests of binder compounds (linear amplitude sweep test and multiple stress creep and recovery test, respectively) and parameters obtained from the fatigue and rutting tests of asphalt mixtures (four-point beam fatigue test and dynamic creep test, respectively) were investigated for the first time in RAP-containing asphalt mixtures. The results indicated that the behavior of asphalt mixtures in fatigue and rutting resistance was agreed with the behavior of the binder compounds in the linear amplitude sweep and multiple stress creep and recovery tests. Besides, there were statistically good correlations between the binder's fatigue life and asphalt mixtures' fatigue life and relatively good statistical correlations between binder's rutting resistance and asphalt mixtures' rutting resistance in the RAP-containing asphalt mixtures.

The efficiency of contractors selection in infrastructure projects is always one of the main concerns of employers. The purpose of this study is to propose a new method for specification of evaluation criteria, according to the type of project under assignment and prioritization, and to determine the proposed score of the evaluation criteria of the contractors using two different methods. The first involves statistical analysis of the questionnaires and the second involves the text mining of the interviews. For this purpose, after library studies, fieldwork and questionnaire design, questionnaires were given to experts in the industry and their statistical analysis identified important criteria and sub-criteria and then interviewed another group of experts. Using the text mining and clustering of interview texts, the criteria and indices of contractors' evaluation were identified and the results of these two methods were compared with the bidding law implementing regulations in Iran. SPSS software was used to analyze the interviews and K-means algorithm was used to interviews text mining. The findings of the study indicate that the results of the text mining and questionnaire are in agreement and It can be concluded that the identified criteria have acceptable accuracy and generalization capability and organizations can use these criteria and evaluation indicators to select the most suitable contractor in the tenders. Identified Criteria, in addition to covering all the criteria introduced in the Bidding Law Implementing Regulations, also include two new criteria, namely Claim Management and Safety Management & Quality Control.

Wheat straw is known as a low–value agricultural waste resulting from wheat harvesting process of wheat fields. This waste is often burned in post–harvest wheat fields, which causes environmental pollution and loss of life cycle in farms and natural ecosystems and in the long term greatly reduces the fertility of the soil. Wheat straw is rich in amorphous silica, which the process of its extraction is simple and does not require any special equipment and chemicals. Amorphous silica has the potential to participate in chemical reactions and can be used as an inexpensive raw material for the production of silica–based materials. In the present study, amorphous and active silica successfully extracted from wheat straw as an agricultural waste and used in synthesis of magnetic nanoparticles Fe3O4@SiO2. Structural characteristics of extracted silica and synthesized magnetic nanoparticles were investigated by XRF, XRD, FT–IR, SEM and VSM analyses. Obtained results showed that active silica with purity of 96.52% in form of amorphous was extracted. In addition, it was found that the produced silica structure was fiber–like and had high performance and quality for silica–based materials production. Furthermore the results indicated the superparamagnetic nature of the Fe3O4@SiO2 magnetic nanoparticle and also verified the structural consistency of the Fe3O4@SiO2 after being functionalized by chitosan. Finally, this nanocomposite was used to remove Basic Red 46 dye from aqueous solutions and the results of experiments showed that the removal efficiency and equilibrium adsorption capacity of this adsorbent were excellent.

The purpose of this study was to evaluate the sensitivity of steel frame with converging braid compared to random variables under a seismic load. 10-story frame types with convergent bracing system (four types) are analyzed after design and modeling using Monte Carlo and FOSM methods. Then the sensitivity of their response to random variables is evaluated. In this study, two-dimensional frames for sensitivity analysis were used. Also, the sensitivity analysis of the FOSM method is compared to the Monte Carlo analysis. The steel yield stress, the steel elastic modulus, the dead load, the live load, the damping coefficient and the length of the span are considered as random variables and their impact on the period of the structures, the maximum displacement of the roof and the maximum base shear have been investigated. The results show that the effect of random variables on the maximum Roof displacement is higher. The maximum sensitivity of the base shear to the random variables in the X convergent brace is more than the other structural systems, and or compared to the maximum roof displacement and the maximum base shear. The general results of the analysis show that steel yield stress, dead load, and damping ratio have the most effect on the response of steel bracing frames, so they should be carefully considered in structural calculations. This sensitivity is lower in live load, span length, and elasticity modulus of steel.

In recent years, it is tried to express the expected performance of structures as financial and social measures. In this study, an algorithm for optimal design of viscous dampers with the goal of achieving minimum total cost is presented. For this purpose, an appropriate cost model to determine the initial cost of equipping structures with viscous dampers has been presented and the expected costs of the structure due to possible earthquakes over its life cycle have been estimated using life cycle cost analysis (LCCA). The results of this analysis have been used in an optimization algorithm with the aim of achieving minimum total cost of structures. To evaluate the seismic behavior of structures, the Endurance Time (ET) method is used as a dynamic analysis method which requires much less computation effort than conventional time history methods. In this regard, three moment frames with 3,7 and 15 stories having weakness in initial design are modeled nonlinearly, and then, using genetic algorithm the optimum arrangement of linear and nonlinear viscous dampers along with the damping exponent (Alpha) is acquired. Two closed form methods have also been used for the design of viscous dampers, namely energy-based damping design and direct displacement design. Finally, the performance of the structures has been evaluated under 12 far-field and 12 near fault ground motion records.

In the present study, effect of natural cementation on the shearing behavior of carbonate sand of Khark Island, south of Iran, has been investigated. To do so, a pseudo-natural cementation method was employed. The importance of this technique lies in its suitability as a substitute for undisturbed samples of cemented carbonate soil that are hard and costly to prepare. Uncemented and cemented samples provided by this method were tested using direct shear apparatus and the results were analyzed and compared to one another. Furthermore, effects of factors such as curing time and relative compaction on the shearing behavior of the Khark sand were studied. It was observed that cementation results in the rise of the shearing resistance, in particular at high vertical stresses, and leads to a decline in the tendency of soil to dilation. While cementation led to growth in the internal friction angle of soil, it may cause increase, decrease or no change in the cohesion of the Khark sand. Increase in curing time led to considerable rise in the cohesion and minor change in the internal friction angle of the cemented soil. Furthermore, results showed that as the relative compaction of the investigated cemented carbonate soil goes up, the cohesion of the soil might increase, decline or stay unchanged while the internal friction angle always increases. Factors that are likely to contribute to the development of the behavior stated earlier were introduced and their effects were discussed thoroughly.

One of the common phenomena in water and urban wastewater transport pipes is sedimentation. Due to complexity of sedimentation phenomenon and influence of various parameters, determining the governing equations are difficult and classical mathematical models are not sufficiently accurate. In this study, capability of Gaussian Process Regression (GPR) in predicting sediment discharge in circular rainwater transport pipes with smooth and rough beds was investigated. In this regard, hydraulic and sediment parameters which had most correlation with sediment discharge were determined using factorial analysis. Then, different models were developed and using three experimental data series were investigated. Then, the accuracy of the results was compared with the classical sediment transport models. The results showed the high efficiency of the intelligent GPR model in prediction of sediment discharge in rainwater transport pipes compared to the classical methods. In both pipes the model with input parameters λs, Fm, Dgr, d50/y which are relative sediment size, non-dimensional sediment size, fraud number of sediments, and total roughness coefficient, respectively, was obtained as superior model. It was also observed that pipe diameter affected the models efficiency and with increasing pipe diameter, model accuracy increased. The pipe with a diameter of 305 mm led to more accurate results. Factorial and omitted sensitivity analysis showed that d50/y was the most effective parameter in estimation of sediment discharge in both smooth and rough pipes.

The use of steel braces in buildings with a moment resisting frame system can significantly control the lateral displacement of the structures. One of the problems with the conventional bracing system is their buckling in compressive loads which reduces the amount of energy absorption of the structure. The buckling restrained braces (BRBs) have been proposed by the removing the buckling at the pressure of common bracing, but overweight, high prices and rigorous implementations have led to the introduction of a new type of buckling brace called Reduced Length Buckling Restrained Brace (RLBRB). However, in RLBRB, due to the low cyclic fatigue phenomenon, the length of bracing can‍‍‍‍‍ not be over-reduced so that it can be replaced as an inactive system after an earthquake. In this research, a new and innovative idea called Reduced Length Buckling Restrained Brace with S-shaped Core is introduced, which, despite its very short length, can overcome all the problems with the RLBRB and BRB system. Therefore, we first validate the analytical models of RLBRB and BRBs in the ABAQUS finite element software based on the experimental results of previous experimental research program. Then, according to the results of the analysis, the hysteresis response of the buckling braces with the S-shaped core is compared with the RLBRB and BRB braces. The results from the comparison of the proposed pattern with conventional buckling braces indicate that, despite the smaller and lighter ones, proposed braces have the same behavior as the BRB braces.

Considering the soil-foundation-structure interaction (SFSI) in the structural modelling procedure can change the seismic structural response. The aim of this paper is to evaluate the influence of the foundation flexibility on the capacity of concrete moment frames with shear wall. For this purpose, the beam on nonlinear Winkler foundation approach is used which is a simple and efficient method. First, a collection of 3, 6 and 10 storeyed reinforced concrete moment resisting frames founded on soft, medium and hard soils are designed based of FEMA450. After implementation of frames in Opensees software, a set of seismic scenarios are selected. In the following, each frame which has been founded on the soft, medium and hard soil are analyzed for the case of fixed-base and flexible-base assumption by incremental dynamic analysis (IDA). A comparison is made between the results of each frame in the flexible-base and fixed-base conditions. The results show that the consideration of the SFSI effects can significantly influence the IDA curves and decrease the structural capacity of frames. So that, dynamic instability will be occurred before the expected capacity corresponding to fixed-base assumptions has been achieved. This instability increases with increasing shear wave velocity of soils and height of frames. For example, 3 and 6 storeyed frames with flexible base which have been founded on soft soil, reach ultimate capacity in 52% and 45% of spectral acceleration corresponding to fixed base respectively.

Global sensitivity analysis is one of the beneficial and useful tool to identify the uncertainty of input variables that has been extremely investigated in different science such as simulations. Sensitivity analysis is an essential step in the production of meta-model, which, by identifying effective parameters in tunneling, reduces the time and computations required. In this paper, sensitivity analysis was carried out on geotechnical and operational parameters of EPB mechanized tunneling in soft soil. So, the tunneling processes were modeled using a finite difference method in FLAC 3D software, and the numerical model was validated by the monitoring data obtained from the East-West route of Tehran metro 7 line. The sensitivity analysis by using elementary effect Morris method was performed on the 6 input parameters and three parameters (face pressure, specific gravity and cohesion of the soil layer which the tunnel was excavated) were selected as effective and sensitive parameters in the maximum surface settlement. Then to construction of meta- model, 100 samples were generated from effective parameters using the Latin Hypercube method. After numerical simulation for each sample, the simulation results were used for surface settlement prediction by using artificial neural network. The results showed that the prediction of the meta-model based on the artificial neural network and the numerical model for the data in the design phase corresponded about 98%.

In the present study, a new model is derived to estimate the shear capacity of high-strength concrete slender beams without transverse reinforcement using hybrid adaptive neuro-fuzzy inference system (ANFIS) and particle swarm optimization (PSO) based on the wide range of experimental results. The proposed model relates the shear capacity of beam to effective depth, compressive strength of concrete, percent of longitudinal reinforcement, ratio of shear span to effective depth, and nominal maximum size of coarse aggregate. The experimental data are randomly categorized into two subsets of the training set and test set. After establishing the proposed model, a sensitivity analysis was carried out to assess the validity of proposed ANFIS-PSO model. For this purpose, the results of the proposed model are calculated by considering the variation of the two selected input parameters, whereas the values of other parameters are fixed at the corresponding median values. To check reliability of the proposed model more accurately, the predicted values are compared with the codes and standards such as: ACI 318-14, Eurocode-2, CEB-FIP Model Code, AS 3600-2009, and JSCE Guidelines against the whole experimental specimens based on the three well-known statistical measures; correlation coefficient (R^2), root mean squared error (RMSE), and mean absolute percentage error (MAPE). It can be found that the proposed ANFIS-PSO model passed desired conditions and could estimate the shear capacity of the high-strength concrete slender beams without transverse reinforcement with a good degree of accuracy.

In this study, the seismic performance of steel special moment frames under the far field records with and without viscous dampers using FEMA P-695 has been evaluated. 4,8 and 12 story frames based on ASCE 7-10 ,AISC 360 have been designed considering viscous dampers features for a specific damping ratio of 15% (4,8 storey) , and 20% (model 12). Frames with dampers and without them with centralized plastic joints have been designed in opensees software with Bilin cyclic behavior. The frames have been scaled and analyzed based on non-linear incremental dynamic analysis (IDA) using 44 acceleration record of far field in a wide area as well as of seismic intensity. Seismic performance of the above mentioned frames has been offered in case of the probability of collapse, based on probabilistic analysis of seismic fragility. The results point out that in steel frames with viscous dampers at the probable level of 50% the collapsing capacity have raised up to 28%,88% and 74% relating to middle curve of non-linear incremental dynamic analysis. It has also been shown that the design of buildings with viscous dampers with 75% base cut have significantly influenced the reduction in the building weight and its costs as well as in the improvement in technical behavior and criteria.

Road flooding has always caused many problems in cities due to inadequate surface runoff collection network. Therefore, it is important to identify flood-prone areas and channels that have been flooded. In this study, using SWMM model, the sufficiency of Surface Runoff Collection Network in Shahrekord was investigated during 2, 5 and 10 year rainfall returns. It should be noted that so far no studies have been conducted on the issue of urban runoff in this area. In this simulation, model calibration was performed for discharge index at 3 and depth index at 2 rainfall events. The error coefficients of NSE, RMSE, and BIAS% were used to compare the simulated model error with the observed values. By sensitivity analysis, equivalent width index was selected as the most sensitive index of the model. The validation was performed on two discharge parameters and runoff depth, each in 2 separate rainfall events, in several random canals and nodes. The acceptable values for the error coefficients showed high accuracy of the simulation. After the validation phase, the model was run for 2, 5, and 10 year rainfall return periods and it was found that flooding occurs in 19.4%, 20.68% and 21.52% of city canals, respectively. The location of the flooded channels indicates that the southwestern part of the city will be flooded. The optimal dimensions of the canals to prevent flooding were determined during the 10-year rainfall return period and the volume of concrete needed to modify the dimensions of each canal was also estimated.

Wind has been one of the cleanest sources of energy. The tendency to use wind turbines has been a growing trend in the world in recent decades. The size and capacity of wind turbines are increasing rapidly in order to obtain more wind energy. Statistics show that more giant turbines are more broken down and require more maintenance. The goal of wind farm owners is to monitor work to reduce downtime and increase the efficiency of each wind turbine. The wind turbine tower carries the entire wind turbine and is the second-largest cost of the wind turbine. Damage to the tower can endanger the entire wind turbine and cause extensive damage. However, the background to the study of the health monitoring of the wind turbine tower against its mechanical installations is insignificant. Besides, no comprehensive research has been conducted on the health monitoring of the tower with soil-structure interaction included. In this study, biorthogonal wavelets were used to process the mode shape of the damaged tower. The foundation is a square concrete foundation 20 m × 20 m and 1 m in depth. Two different soils, a normally consolidated clay and dense sand, are considered. Eighteen failure scenarios were defined. The results of this study indicate that the use of side-to-side mode shapes of the tower has a tangible advantage over its fore-aft mode shapes for detecting the failure. Considering the desirable effect of soil-structure interaction on damage detection, it is necessary to examine this effect in the analysis.

The purpose of paper is qualitative and quantitative study of the relationship between the energy demand of multi-degree-of-freedom systems, MDOF, and equivalent-single-degree-of-freedom systems to calculate the total energy demand of the MDOF system using the ESDOF energy demand. For this purpose, multi-story special steel moment frames designed and analyzed under 10 near-fault earthquake with forward-directivity effects. Moreover, the process done for the ESDOF system considering specified values of R (degree of nonlinearity). Accordingly, linear and nonlinear total dissipated energy (TDE), hysteretic energy (HE), and damping energy (DE) ratios were introduced to estimate the relationship of the ESDOF and MDOF energy. Results shows that ratio of nonlinear to linear TDE and HE/TDE is affected by period and R in ESDOF system. However, as the period and R increase, the ratio converges to one. The same result was observed between the nonlinear TDE of the MDOF system and the linear TDE of the ESDOF system. In other words, ESDOF linear TDE can be used instead of MDOF for long periods. In addition, the nonlinear TDE of the MDOF system to the nonlinear TDE of the ESDOF system ratio is affected by higher modes and period, by increasing the period the ratio is generally greater than one for the constant R. Also the effect of higher modes on the ratio of total story dissipated energy to total structure dissipated energy was significant for low R values. With increasing R, the structure tends to damp all the dissipated energy in the first mode.

One of the most important weakness points of concrete is its drawback in tension and cracking. The use of fibers in concrete greatly reduces this disadvantage. Fiber reinforced cementitious composite (FRCC) is a type of fiber reinforced concrete (FRC) that does not contain coarse aggregate and has only fine aggregate. In fact, the high level of cement in FRCC is a problem for the environment. This problem can be solved with using different cement replacement materials as a part of cement. In this study, the effect of copper slag on the mechanical properties and fracture energy of fiber reinforced cementitious composite (FRCC) containing polypropylene fiber is investigated. Silica fume and copper slag were replaced as a part of cement. For this purpose, a control mix without silica fume and copper slag, 4 mixes containing 5%, 7%, 10% and 15 % silica fume, and 4 mixtures with 5%, 10%, 20% and 30 % copper slag were casted. In specimens containing silica fume, the ones with 15% of it had the highest quantity of fracture energy, compressive, tensile, and flexural strengths. Among the samples having copper slag, the ones containing 10% and 20% of it had the highest values above. It is worth noting that some binary mixtures containing both copper slag and silica fume were prepared too. Comparing the results of all the mentioned mixtures, it is concluded that the best results belong to the binary mixture containing both 15 % copper slag and 15 % of silica fume.

Due to the high costs of running a water supply network, designing networks with the lowest cost and highest reliability is of great engineering importance. One issue that has been the focus of recent years' research is the comparison of indexes and their relative success in measuring the reliability of water distribution networks. In this paper, a survey was conducted on the nodal pressure performance index, velocity, pressure difference, combined velocity and node pressure index, network flexibility performance index (NRI), minimum head surplus index (MSH) and entropy performance index (ERI) on the Hanoi water distribution network and Pescara juice were performed using the NSGA-II optimization algorithm and EPANET software. Performance of the indexes were tested for three scenarios of 5%, 10% and 20% pipe failure and four different cost levels and 100 iterations. The results showed that in the design of small water distribution network (Hanoi water network) at high and low cost level, NRI performance index and at medium water distribution network (Pescara water network) and at high cost level, NRI performance index and at low cost level, Node pressure performance index (PIP), Provided water requirements of network nodes more than other indexes, and the average pressure in these indexes is higher and causes less pressure drop in the network. Therefore, the use of these indexes in the design and modernization of the network provides greater reliability in the event of unexpected events such as sudden failure or failure of the pipes.

Concrete is one of the most widely used building materials in the world and the use of fiber-reinforced concrete (FRC) in structures, to increase its tensile strength and improve its behavior, has been extensively developed in recent decades. It is necessary to determine the constitutive equations of FRCs when the numerical investigation of the behavior of them is running. These equations should be including relations to handle the effect of steel fibers on the behavior of FRC. In this study, the behavior of FRCs with a different percent of steel fiber under triaxial compression, with different values of confining pressure, is experimentally and numerically investigated. Hoek cell is used in triaxial tests. In the numerical simulation, five-parametric constitutive equations with Willam-Warnke (W-W) failure criterion, isotropic hardening/softening function and non-associated plasticity was used and substepping integration method was carried out for integration of constitutive equations. For applying the effect of steel fibers on the failure surface, Kt coefficient was determined from the results of biaxial experimental tests on SFRCs. The constitutive equations are implemented with UMAT subroutine in ABAQUS and specimens are simulated in ABAQUS. By the comparison of the experimental (maximum strength) results and the numerical (stress-strain curve) results, an acceptable agreement was seen between them. Finally, based on the consistency between experimental and numerical results, it was concluded that the numerical model can be used, with enough confidence, to predict the behavior of SFRCs specimens.

Precise Estimation of water exchange between surface and subsurface flow in hyporheic zone which is habitat of microorganisms is vital. The temperature can be used as a tracer for estimation of water exchange through sediment water interphase. In this study, for the first time in Iran, an instrument was designed and constructed to make the measurement and recording of sediment temperature in the depth of hyporheic zone possible. In this regard, measurements were made in the Ziarat River of Golestan Province by the aforementioned instrument, and surface and subsurface water exchange rates were calculated using an extended conceptual model of heat transfer. For this purpose, in a 40 m interval of the river, 10 cross sections were selected at 4 m intervals, and at each cross section, temperature of 4 different depths of the riverbed (immediately below the bed, 0.25, 0.50, 0.75 m) were recorded in July and January. The results showed that in all seasons there is a constant flow due to the difference of thermal potential between surface and subsurface of the river flow which leads to the transfer of nutrients to micro-organisms and consequently to the permanent self-purification of the river. The average of vertical exchange for July and January was 0.34 mm/day and 0.86 mm/day respectively.

Maintenance and rehabilitation scheduling optimization is one of the most critical parts of the pavement management system. Pavement agencies usually face large-scale pavement networks. The complexity of network management is exponentially increased in the circumstances that the dimension of the network is extended. Hence, meta-heuristic algorithms and decomposition techniques are usually applied to solve these problems. In this investigation, energy consumption optimization is taken into account as an essential environmental criterion. Furthermore, a recently developed meta-heuristic algorithm called Soccer league competition algorithm is utilized to solve the problem. This robust algorithm is inspired by the competitions of players and teams in soccer leagues. A real network containing 84 segments is the case study of this investigation. According to the results, the Soccer league competition algorithm is competent to solve a large-scale network problem in a short time. Moreover, the comparison of different strategies outcomes indicates that considering energy consumption as the second objective function reduces the energy consumption and total cost 13% and 10%, respectively, and increases the average international roughness index by 9%.