نشریه مهندسی عمران
سال پنجاه و سوم شماره 9 (آذر 1400)

The scour has been studied in hydraulic science for many years, due to its complexity and lack of proper relationship, it has been the attention of hydraulic scientists. Hydraulic structures situated as an obstacle in front of water flow that changed the flow pattern in their vicinity and causing the local scour around the structure. There are various methods to reduce local scour around the pier. In this research, sacrificial pile and collar were used to reduce the local scour around inclined pier group. The results show that using of the sacrificial pile in front of the inclined pier group, the effect of the inclined pier angle on the reduction of the scour is lower. So that difference between the percentage of scour reduction for the first and second inclined piers in the angle of 5 and 15 degrees is zero and in vertical pier is 1.4%. The use of three collars with a diameter of 4b in pier group with the distance of 4b between piers and presence of sacrificial pile in front of the first inclined pier in distance of 3b compared to 2b show a greater scour depth reduction in front of the piers. In the numerical model, the use of inclined pier group with the distance of 3b between piers and sacrificial pile with distance of 2b shows lower turbulence intensity compared to distances of b and 3b.

The composite steel plate shear wall (CSPSW) is an innovative lateral load-resisting system which is comprised of reinforced concrete (RC) panels attached to one or both sides of the system by means of shear connectors. Accordingly, in the CSPSW, the RC panels prevent buckling of the steel plate and thus, shear capacity of the plate improves by the shear yielding limit of the plate instead of tension in direction of diagonal tension field. Subsequently, this study is aimed to analytically and numerically investigate the effect of thickness and concrete type of panels on the behavior of the CSPSW. To this end, 27 numerical models of CSPSWs with varying thickness of steel plate and concrete panels as well as width-to-height (W/H) ratio of 0.75, 1 and 1.5 have been built using ABAQUS software and then, analyzed through pushover analysis method. The results indicate that in all W/H ratios, the energy absorption of the models with a plate thickness of 6mm surpasses the others. Importantly, it was found that the response modification factor of the CSPSW is estimated to be 13.5. Lastly, a semi-empirical relationship was proposed to calculate the thickness of the RC panel based on that of the steel plate so that plate buckling could be prevented.

Travel time prediction as an essential issue has been scrutinized in recent decades. To this end, various techniques are applied to estimate travel duration in the dynamic networks and intelligent transportation systems. Accordingly, in this investigation, prediction of travel time is considered by machine learning techniques. Initially, the experimental test is planned, and the travel time effective parameters are spotted. Subsequently, with the assistance of the floating car method, and Mytacks application, the data are collected in six elected roads. After data preparation, stop delay, grades, and the number of the lane are determined as the most effective travel time criteria. In this study, a novel machine learning technique based on the coyote optimization algorithm is introduced, and its precision is compared with five conventional regression models. Drawing on results, the accuracy of the coyote optimization algorithm-based machine learning technique is more than that of other prediction methods. The coefficient of determination of the introduced machine learning technique for training and testing data is equal to 0.746 and 0.724, respectively. Furthermore, coyote optimization algorithm-based machine learning estimates 73% of testing data with an error of fewer than 20 seconds.

The present study investigated the characteristics of hydraulic parameters of Sloped Gabion Drops and Simple Drops. Therefore, 120 different experiments were performed on both types of sloped gabion drop and sloped simple drop with three angles and two heights. Results showed that by increasing the relative critical depth in both tested models, causes a reduction in relative energy dissipation rate but an increase in relative downstream depth. Comparing the results for sloped gabion drops and sloped simple drops showed that the use of gabion structures with three angles and two heights which, have been investigated, increases the average energy dissipation efficiency 561% and the average downstream relative depth 50.1% compared to the simple drops. So, this results in a decrease in the erosion of the downstream bed of the structure and the length of the pool. The results showed that as the angle of incline increases, the average energy dissipation efficiency decreases and, the average downstream relative depth increases. The results showed that the change in the angle of the incline in sloped gabion drops had a relatively small effect, in comparison with the simple drops due to the physical properties and the complex hydraulic effects of the flow through the porous structure. Also, some relationships were presented to estimate the relative energy dissipation rate and the downstream relative depth rate in the sloped gabion drops by using 80% percent of laboratory data, and the rest 20% of the data were used to test the relationships with the evaluation criteria.

Because to the increasing use of chromium in various industries, water pollution with chromium has become a significant problem. Hexavalent chromium (Cr (VI)) is known as a toxic substance for aquatic organisms, animals and humans and as a carcinogen, so it is very important to treat this type of wastewater. In the present study, a new magnetic nanocomposite EDTA/Chitosan/CeZnO (MEC-CeZnO) was synthetized and used to remove heavy metal ions of Cr (VI) from an aqueous solution. The morphology, structure, and properties of the new MEC-CeZnO magnetic nanocomposite were identified by SEM, EDX, and XRD methods and the effect of various parameters such as initial pH, contact time and initial Cr (VI) concentration on system efficiency was investigated. The results showed that MEC-CeZnO nanoparticles with an average diameter of less than 45 nm, had the best performance of Cr (VI) regeneration at an input concentration of 10 mg/L, pH of 3 and retention time equal to 180 minutes. Also, process kinetic studies showed that the results of Cr (VI) reduction process follow the second-order kinetic model. Finally, the reusability of nanocomposites was tested in 5 cycles; the results showed a high efficiency of 90% of nanocomposites in the reduction of metal ions.

Successive deterioration in concrete structures which is caused by the acid attack has increased the need for substantial and costly repairs to deal with the destruction of concrete structures. Common devastation of water transfer tunnels is due to sulfuric acid attack. One of the ways of maintenance of such structures is to perform the protective coating of the cementitious and geopolymer coating mortars, in which the different features of this coating layer should be studied.In this study, the mechanical properties and durability of geopolymer and cementitious coating mortars containing granulated blast furnace slag and natural pozzolan have been compared. Five cementitious mortar mixtures were prepared with water to binder ratio of 0.32, binder content of 450 Kg/m3, and replacement of Portland cement (PC) with 20 and 40% slag and natural pozzolan. 2 geopolymer mortar mixtures with KOH and NaOH as activator were designed. To evaluate their mechanical properties Compressive strength and tensile adhesion strength were carried out. Also, in order to investigate their durability features against sulfuric acid attack, mortar specimens length Change, compressive strength loss, and weight loss were investigated. According to the results, the use of cement substitute materials (furnace slag and natural pozzolan) reduced the compressive strength by 25%, increased the adhesion strength by 50%, and reduced the length change, weight loss and compressive strength loss of the samples exposed to sulfuric acid. Also, the use of geopolymer mortars had the better performance in aggressive acidic environments compared to cement-based mortars.

The main purpose of this study is an analytical comparison of attitude change to integrated management of urban water/wastewater in the development plans of Iran, before and after the Islamic Revolution. The results indicate that there are four periods of changes in attitude towards this issue in Iran. The first period was initiated to launch planning thinking. In the second period, which lasted till before the Islamic Revolution, the planning system in Iran, after gaining experience, has undergone a dramatic change and some issues such as national coverage of the wastewater collection system, reliable water supply and minimum price of water, were mentioned in the development plans for the first time. In the end years of this period, planning in Iran was matured and all aspects of integrated management except water treatment had been considered. The third period came simultaneously with the revision of the constitution of Iran, after the revolution. In this period, supported by macro policies after the mid-2000s, a period of excellence in the approach of integrated management of urban water and wastewater was created. Also, a macro roadmap in the planning system of Iran was developed. The fourth period of attitude changes began with the beginning of the second step of the revolution and will last until 2065. In this period, the "Islamic-Iranian Model of Progress", as an upstream framework of the macro policies and development plans, have a significant role in establishing an integrated urban water and wastewater management approach in future development plans.

Nowadays, designing structures follows the designs that are based on the performance. Regarding the structures, designing based on performance requires dynamic, heavy and repetitive analyses. Endurance time method is a dynamic modern method based on the performance of the structure, which leads to the reduction of number of structural analyses. In this method, the structure gets exposed to increasing acceleration functions that is getting more during time and then the structure`s seismic performance is evaluated using various demand parameters. In this article, though, using endurance time method, the performance of a structure having active mass damper was evaluated under endurance time acceleration functions of ETA20e series. To this end, an 11 story structure having active mass damper was modeled in MATLAB software using one of the fuzzy control methods. Having investigated the results of endurance time diagram that had drew the before and after statuses of the refinement process using active mass damper, the efficiency of this system in reducing the interstory drift and maximum final story drift was explored. Moreover, the results of endurance time under acceleration function of ETA20e series were compared with the time history analysis of 7 selected accelerograms. The results indicated that endurance time function could present an appropriate prediction in estimating the behavior of the structure under selected accelerogram. The results indicated the significant impact of adding mass dampers under increasing the endurance time of the building under investigation.

The widespread presence and problems of microplastics in the environment have attracted the attention of many researchers. Urban wastewater treatment plants have been one of their important releasing sources. In this study, Sari municipal wastewater treatment plant was investigated as one of the potential sources of contaminating aquatic ecosystems (Tajan River and the Caspian Sea) and terrestrial. The final effluent and sludge samples were taken in 3 replications, in May and June 2018. The effluent samples were passed through 500, 300 and 37 μm steel sieve. Organic matter in the sludge and effluent samples were digested using hydrogen peroxide and then the microplastics were extracted by density-based separation using sodium iodide salt and examined by stereomicroscope and micro-Raman. The average number of microplastics in the effluent was 423/4 per m3, of which more than 77% were fiber and the predominant size of the microplastics was 37-300 μm. Also, sewage sludge had an average 128/7 microplastic per g(d.w), and fiber (87/5%) was the most common shape of microplastics in it. Furthermore, the dominant types of fibers and particles in the samples were polyester (effluent 40% and sludge 59%) and polyethylene (effluent 73% and sludge 68%), respectively, which are mainly obtained from the wastewater from washing clothes and microbeads used in cosmetics. Therefore, considering the amount of microplastics present in the effluent and sludge, Sari wastewater treatment plant can be considered as one of the most important sources of microplastics in the aquatic and terrestrial ecosystem in the north of the country.

Direct displacement-based design (DDBD) approach is one of performance-based design methods that has been paid attention by designers and researchers because of its effective performance in achievement of design performance level. In this study, DDBD is developed for design of structures equipped with nonlinear fluid viscous damper (FVD). The designed structures are steel moment frames with different heights of 4, 8 and 12 stories that these frames are designed to achieve life safety performance level under seismic hazard having a probability of occurrence 10% in 50 years. These structures have been also designed using DDBD while have been controlled by linear FVD and a comparison has been conducted between design results. The results show that the design sections of structures equipped with linear and nonlinear FVDs are almost the same whereas nonlinear behavior of FVD has significant effect on the design of damping coefficient. Nonlinear time-history analysis of the designed structures has been performed under different earthquake records in order to evaluate the performance of design method. The results show that average peak story drift is less than target drift and the designed structures have achieved the desirable performance level. Therefore it can be concluded that DDBD developed in this study is an effective method for design of steel moment frames equipped with nonlinear FVD.

One of the effective parameters in the occurrence of fatigue cracking is the bitumen properties used. One way to control this type of failure is to use bitumen, aggregate or asphalt mix modifiers. In this study, the effect of using a polymeric additive called acrylonitrile styrene acrylate (ASA) as a bitumen modifier on the fatigue cracking potential in asphalt mixtures was investigated. Two types of aggregates, with different mineralogical characteristics, bitumen PG 64-16 and ASA additive in two percent of bitumen mass were the materials used in this study that were tested at two temperatures and five different stress levels. Marshall mix design method was used to determine the optimum bitumen percentage and indirect tensile fatigue test method was used to determine the fatigue life of asphalt mixtures. The results of this study show that the use of polymer additives has increased the fatigue life of asphalt mixtures. Fatigue life of specimens made with granite aggregates was longer than that of limestone aggregates, but the longer life of ASA resulted in a greater increase in the lifetime of specimens made of granite aggregates. The increase in temperature and stress level also resulted in a decrease in the fatigue life of the asphalt mixture samples as expected, which was much lower in the bitumen samples modified with polymeric materials. Has been in control.

A direct time-domain numerical approach named the half-plane boundary element method is proposed based on the half-space Green’s functions for seismic analysis of trapezoidal alluvial hill located on a circular cavity, subjected to propagating vertical incident SH-waves. To analyze the assumed model, a half plane time-domain Boundary Element Method (BEM) was used which can concentrate the meshes only around the boundary of desired features. First, the problem is decomposed into two parts including a pitted half-plane and a trapezoidal filled solid on the surface. Then, the influence coefficients of the matrices are obtained by applying the method to each part. By satisfying the boundary/continuity conditions on the interfaces, a coupled equation is formed to determine unknown boundary values in each time-step. After implementing the method in an advanced developed algorithm, its efficiency is investigated by solving some practical examples and compared with those of the published works. To complete the results, the sensitivity analysis was carried out to obtain the seismic response of hill by considering the key parameters including impedance and shape ratios. In the meantime, the effect of subsurface cavity on the amplification pattern of surface has been studied as well. The results showed that the impedance and shape ratios of the trapezoidal alluvial hill were very effective on the seismic response of surface. The results of the present study can be used by geotechnical engineers to completing and increasing the accuracy of existing codes around the subject of ground surface zonation in presence of different topographic features.

Subway network design can be classified as one of the most challenging problems in transportation planning, where different deterministic or non-deterministic approaches have been utilized for optimal design. Non-deterministic methods, having fewer limitations and representing reality with its intrinsic uncertainty, have thus been the focus of less research. This paper incorporates concepts of fuzzy set theory into optimal design of subway networks to the case of Tehran. Two binary mathematical programming models with different objective functions are developed. The first model maximizes the covered population while minimizing construction cost, whereas the second maximizes the ratio of the covered population to construction cost. These objective functions are modeled in both a fuzzy and a deterministic state. In the fuzzy model, we use a fuzzy penalty factor instead of edge length constraints and propose a Sugeno fuzzy inference system for calculating the covered population. Results indicate that the total length of designed lines with the linear and nonlinear fuzzy approach is equal to 139.3 km (477000 billion Iranian Rials) and 144.6 km (494000 billion Iranian Rials), respectively. Considering topology improvement per construction cost index, designed lines with the linear fuzzy model are better than the nonlinear fuzzy model. In comparison to the classic deterministic approach, the proposed fuzzy approach can improve topology improvement per construction cost index by 23 percent.

The shear strength of deep beams of the reinforced concrete beams depends on the mechanical and geometrical parameters properties of the beam. Accurate estimation of shear strength in deep reinforced concrete deep beams of the reinforced concrete is one of the major issues in the design of engineering structures. However, some methods proposed to determine the shear strength in deep reinforced concrete beams do not have high accuracy. One method to accurately estimate shear strength is to use artificial intelligence (AI). Artificial intelligence has many different methods, one of which is the use of artificial intelligence based on the support vector machine method. In this study, the weighted least squares support vector machine (WLS-SVM), which is a relatively new and efficient method for predicting the shear capacity of reinforced concrete beams, has been used. In this study, a database containing experimental results on deep reinforced concrete beams was first collected. Then, after determining the input and output parameters using a training process in WLS-SVM method and using a part of the collected data, a model was developed to predict the shear strength of deep reinforced concrete beams. In order to determine the accuracy of the WLS-SVM method, the results were compared with those obtained by other AI methods and different regulations. Statistical analysis showed that WLS-SVM has the best performance in terms of statistical evaluation parameters (R^2 = 0.9887, RMSE = 0.107, MAE = 0.478 and MAPE = 9.48%) compared to the other methods.

Flow structure around bridge pier is a very complicated phenomenon. Due to the special geometric and structural conditions in some cases, it is required that the piers be placed in pairs next to each other with special arrangements, which leads to a more complex flow structure around the piers. In this study, the variations of the flow velocity and turbulent kinetic energy around single and the twin bridge piers with a circular cross section is simulated using the Fluent model. The twin piers are placed in three configurations including tandem, side-by-side, and at inclined with the flow direction. The three-dimensional components of flow velocity, streamlines, and velocity contours have been investigated for both single and twin piers. By comparing the longitudinal velocity between measured and simulated conditions in two selected cross sections, the average error for the single tandem piers was 7.3% and 3.54%, respectively. Also, the longitudinal velocity in the tandem, side-by-side and inclined piers has decreased by 2.34% and 9.27% and increased by 87.8%, respectively, compared to the single pier conditions. In general, due to the minimum values of turbulent velocity and kinetic energy, the side-by-side model is recommended as the most appropriate arrangement of the piers with respect to the flow direction.

Energy dissipation in stepped spillways is one of the primary goals of such structures. In this study, the accuracy of the artificial neural network (ANNs) method, the adaptive fuzzy neural inference model method based on the trained firewall optimization algorithm (ANFIS-FA) and the gene expression programming method (GEP) in estimating the energy loss of skimming flow regime on stepped spillways has been studied. Also, by performing sensitivity analysis, the importance of input parameters in predicting energy loss for each of the three mentioned methods has been investigated. For this purpose, 154 series of laboratory data have been used. The input parameters for each method include the hydraulic jump Froude number, the Drop number, the number of steps, the pseudo bottom slope and the ratio of the critical depth to the height of each step.. The results show that all three methods had a higher ability to predict energy loss than classical methods for estimating energy loss based on conventional regression methods. The accuracy of the ANFIS-FA (with) method is slightly higher than the GEP (with) method. The accuracy of the neural network is slightly lower than the above two methods.However, the highest accuracy obtained is related to the multilayer perceptron neural network with 3 hidden layers with the number of 12, 8 and 7 nodes in each layer, respectively. In all three methods, the most effective parameter is the waterfall number and the least effective parameter is the pseudo bottom slope.

Seepage is one of the main threat for the stability of earth dam, which can weaken the dam structure and cause piping, washing the earth dam materials inside the body or foundation and eventually its failure. In this study, seepage analysis of Kamal-Saleh earth-dam was performed using Seep/W software for current dam and increased spillway level. The effect of increasing the height of spillway on the seepage rate inside the body and foundation, hydraulic gradient and phreatic surface was investigated. To evaluate the dam behavior in the conditions of increasing reservoir capacity, seepage analysis was performed for current level and increased levels of spillway by one meter intervals. According to the results of software, the dam was safe against seepage in the current spillway level and provided the required factors of safety. In the conditions of increased spillway level, the amounts of seepage and hydraulic gradients increased and the factors of safety against boiling decreased in a way that by increasing the dam spillway level equal to 4 meters, the seepage through the dam body and foundation increased 85% and the safety factor against boiling decreased 4.5% but in all these conditions, the dam was safe against boiling. In the current and increased spillway levels , there are appropriate similarity of phreatic lines produced by the selected analytical method and Seep/W. The most similarity is seen in the upstream shell and core and the maximum difference is seen in the phreatic line intersection with the downstream slope of the dam.

Predicting the transfer of pollutants in the water zones is of particular importance in the management and prevention of surface water pollution. The heterogeneity and non-conformance in morphology along the river, known to the Storage zone, will change the uniform Transport of pollutants to the downstream. The storage zones are actually places around the river where velocities are significantly slower than the rivers and are also famous as dead zones. The presence of these areas in rivers makes it difficult for them to use the classical equation of pollutant transport. To more accurate simulation of the transport of pollutants in natural rivers with storage zone, modifications should be made to the Advection- dispersion equation. In this research, a new approach to achieve more accurate simulation of transport of pollutant material by considering the changes of pollutant dispersion flux in a nonlinear method and considering the storage zone will be presented. To validate the model presented from the hypothetical example and actual data used. Based on the measured results, the output of the model is an acceptable adaptation with the observed data and shows that the proposed model is accurate and acceptable in simulating the transport of solute in rivers with the Storage zone and it can replace the classic model of pollutant transport in these type of rivers.

The most important feature of the behavior factor is that it allows the structural designer, to be able to evaluate the structural seismic demand, using an elastic analysis, based on force-based principles quickly. In seismic codes such as the 2800Standard, this coefficient is merely dependent on the type of lateral resistance system and is introduced with a fixed number. However, there is a relationship between the behavior factor, ductility (performance level), structural geometric properties, and type of earthquake (near and far). The main purpose of this paper is to establish an accurate correlation between the geometrical characteristics of the structure, performance level and the behavior factor in eccentrically steel frames, under earthquakes near-fault. For this purpose, genetic algorithm is used. Initially a wide database consisting of 12960 data with 3-, 6-, 9-, 12-, 15- and 20- stories, 3 column stiffness types, and 3 brace slenderness types were designed, and analyzed under 20 pulse-type near-fault earthquakes for 4 different performance levels. To generate the proposed relation, 7,500 training data in the form of genetic optimization algorithm were used. To validate the proposed relationship, 2,500 test data were used to calculate the mean squared error of the relationship in the fitness function. The results of the correlation, shows accuracy of proposed coefficients. Also, the comparison of the response of maximum inelastic displacement of 5stories EBF from the proposed correlation and the mean inelastic time history analysis, confirms the accuracy of the estimate relationship

Accurate prediction of pore water pressure, settlement, soil stress and pore water pressure coefficient (Ru) in the body of earth dams during construction is one of the necessary measures in the management of earth dam stability. In the present study, which is a case study, a three-dimensional numerical simulation was performed using the Plaxis software for the Kabudval Dam located in Golestan province, Iran. The values obtained from the numerical simulation were compared with the corresponding measured values using the dam instruments. Calibration was carried out using back analysis method (BAM) and some dam geotechnical parameters were corrected based on BAM. The results showed that the hardening soil (HS) model with the statistical indicators of R2, RMSE and GMER is more accurate compared with the Mohr- Coulomb (MC) model. The results of the numerical model were calibrated at the end of construction for Kabudval Dam and showed that the maximum increase in pore water pressure, stress, settlement and horizontal displacement occurs in the central part and its value in the axis and middle part of the dam is more than its sides. The middle part and close to the dam axis have similar changes with the fill process of the dam body; while with moving away from the dam axis due to the transfer of stresses to the sides, they have less impact from the dam filling process. In addition, in the central part, the effects of filter and drainage is low.

Due to the viscoelastic behavior of asphalt mixtures, depth temperature of asphalt layers is very important in structural evaluation of flexible pavements. Depth temperature could be measured directly in the field, or may be predicted using prediction models. This paper presents a comprehensive analysis of different twelve regression-based models for prediction of depth temperature of asphalt layers. With reference to the literature, required input parameters, sensitivity analysis, evaluation of prediction performance, as well as a comparison of goodness of these models were discussed. Furthermore, calibrated models for different local conditions were presented. This is due to the fact that the original models were usually developed in specific geographical regions and climatic conditions. Results show that the regression-based models have a good performance and high accuracy in predicting the depth temperature of asphalt layers. Among the investigated models, according to the variety of data (or parameters) used in the model development, performance, considering the effect of various parameters, BELLS model introduced as one of the best regression-based models for prediction of depth temperature of asphalt layers. The model developed by Solatifar et al. as a new version of BELLS model, showed very good accuracy for newly constructed pavements. In addition, with applying some modifications, it could be possible to use these models in different pavements and local conditions.

In the present study, the effects of glass and basalt fibers (GF and BF) and temperature on the properties of self-compacting lightweight concrete (SCLC) has been investigated. For this aim, the fresh and hardened properties of 12 SCLC mixes have been investigated that contained monotype and hybrid fibers. The volume of the monotype fibers were 0.25%, 0.5%, 0.75% and 1% of the concrete volume. The hybrid fibers had volume fractions of BF/GF= 0.25%/0.75%, 0.5%/0.5%, and 0.75%/0.25%. The self-compacting properties of SCLC was assessed by means of slump flow, T500, V-funnel and J-ring. After 28 days of curing, the compressive, splitting tensile and flexural strengths tests were performed to characterize the mechanical properties of SCLC at room temperature of 20 °C and high temperatures of 100 and 300 °C. The test results of fresh concrete showed that all the mixes could be defined as SCLC with good flowability, viscosity and passing ability. Hardened test results indicated that the addition of the fibers reduced the compressive strength and increased the tensile strength, flexural strength and fracture energy. Moreover, compared to monotype fibers, the hybrid ones formed effectively enhanced mechanical behaviors of SCLC. The mixes containing 0.75% GF and 0.25% BF was the optimum one and determined acceptable fresh and hardened properties as well as high temperature resistance.

Long driven steel piles are widely used in the foundation of fixed offshore oil and gas extraction platforms. There are different methods to determine the pile bearing capacity, including static analysis, using the results of in-situ tests, as well as static and dynamic pile loading tests. In recent years, the in-situ cone penetration test has considerably been developed in the design of offshore piles owing to its high accuracy, continuous recoding across the depth, and similarity to pile. In this paper, for the first time, a comprehensive data bank, including soil engineering parameters derived from laboratory and in-situ tests as well as field measurements obtained from dynamic pile tests in short, medium, and long term conditions, is developed for the Persian Gulf - South Pars field. Afterward, fourteen methods including four offshore static analysis methods and ten direct methods based on cone penetration test results are selected and applied to estimate the axial compressive bearing capacity of steel pipe piles driven in the studied area. According to the findings of the conducted statistical analyses, the lowest precision and prediction quality are provided in the four static analysis methods compared to the CPT-based methods for the developed data bank. The values of ultimate pile bearing capacity obtained from the static analysis methods are on average 70%, 63%, and 35% higher than the corresponding values measured by the dynamic pile tests, in short, medium, and long term conditions, respectively.

The beams are really useful for the large number of engineering structures. In this article, a simple robust beam element will be formulated. Other researchers utilized several theories such as Euler-Bernoulli, Timoshenko and higher order shear for analyzing of the beams. The proposed formulation will be written based on satisfying the equilibrium equation. Using the equilibrium equation reduces number of unknowns in addition to improving the efficiency of new element. the suggested element has only two nod and tow degrees of freedom per node. The third and second order polynomials will be used for vertical displacement and rotation fields, respectively. After calculating the matrix of shape functions, the governing equations of statics, free vibration and buckling analysis could be written. Finally, using the suggested element, static analysis, free vibration and buckling were performed on the several problems. To prove the efficiency of the new element, the large number of benchmark tests will be utilized. These numerical tests have various support conditions and different aspect ratios. By the help of these tests, rapid convergence and high accuracy of proposed element will be shown. The new element has high efficiency in all of the static, free vibration and buckling analysis for both of thin and thick beams beside of its simplicity. Good element answers of other researchers are be available to have better comparison.

Due to the limitation of Natural freshwater resources and population growth in recent decades, human has turned to the development of water desalination plants to fill the gap between supply and demand. The most important environmental problem of desalination plants is the production of brine (containing high concentration of salt) that is discharged directly into the sea. Various factors affect the dilution rate of discharged effluent, one of the most important of which is the ambient flow. In this study, using CorJet integral model, the effect of ambient flow velocity on the characteristics of jets and plumes and their dilution rates are investigated. The direction and magnitude of the ambient flow affect the mixing of the discharged effluent. This effect is the greatest when the ambient flow velocity is higher than the discharged effluent velocity. In this case, the effluent is completely diverted from its original path and advected in the direction of the ambient flow. In the presence of ambient flow, the greater the discharge angle relative to the horizon, the greater the effluent trajectory path and dilution rate. Furthermore, the discharge angle of 90° results in the highest dilution rate of effluents, when the ambient flow is present. When the angle between the effluent discharge and the ambient flow (0