نشریه مهندسی عمران
سال پنجاه و چهارم شماره 11 (بهمن 1401)

One of the main goals in diverting water in rivers is to provide required water ‎with a minimum of sediments, which is usually met through installation of sediment control structures with different ‎arrangements to significantly decrease the sediment that enters the intake.In addition to sediment control,serious ‎attention should also be paid to impact of these structures and sediment control scenarios on the riverbank and ‎other relevant facilities located in vicinity of intake entrance. Using a laboratory scale canal,equipped with ‎recirculating sediment and included a 90◦lateral intake and a bed moving because of dunes movement, the effects of ‎these structures including sill,dike, and submerged vanes on the banks in the vicinity of intake entrance was ‎experimentally investigated at four different sediment control scenarios and different discharge ratio. In order to ‎accurately evaluate the scour near banks, after dynamic equilibrium was achieved at the bed due to continuous ‎changes of its elevation in these conditions,scour time series analysis was performed at upstream and downstream ‎points near the intake, along the banks on either sides of main canal.results show that different behaviors are ‎observed near intake due to various factors influencing the flow. While, in range of discharge ratios studied dike increases depth and length of scour zone at intake downstream by an average of about72%and‎‎34%, respectively, vanes reduces length of zone by37% and at discharge ratio of0.12, an ‎increase of about 66% in depth of scour zone is observed, while at discharge ratio of0.18, a decrease of‎‎24% in depth of zone occurs.‎

According to the seismic design codes, the response spectrum analysis (RSA) method can be used in the seismic analysis of tall buildings since it can consider the effect of higher modes. On the other hand, the nonlinear time history analysis is the most accurate method of the evaluation of seismic responses of structures. Consequently, it is needed to study the accuracy of the RSA method and to compare the seismic responses computed by the RSA to those from the nonlinear time history analysis. To this end, six 3D structures with 4-, 10- and 20-story heights are investigated in this paper. The lateral load resisting systems of the structures include special steel moment-resisting frames (MRFs) and concentrically braced frames (CBFs). To conduct the nonlinear time history analyses, four sets of ground motion records including three groups of near-fault records with different characteristics and one set of far-fault records are used. The near-fault ground motion sets include forward directivity effect, fling step and no pulse characteristics. All sets comprise seven seismic motion records. The results indicate that the seismic responses, obtained by the RSA, are mostly underestimated and non-conservative in comparison with those from the nonlinear time history analysis. In general, the more the height of the structure, the larger the error in the seismic responses derived from the RSA. Also, the largest error in the RSA relative to the rigorous time history analysis occurs in the case of the near-fault ground motions with fling-step effect.

Value of travel time (VOTT) plays a key role in the choices of travelers. Empirical studies have shown significant differences in VOTT estimates, which researchers attribute that to several factors, including demographic, alternatives, trip, and regional economic characteristics. One of the policies reducing use of private car is congestion pricing of the low emission zone (LEZ). This study aims to estimate VOTT and analyze its heterogeneity among users of Tehran LEZ. We use stated preference (SP) data to calibrate mixed logit models, based on which, travelers' value of time is evaluated. The mean value of travel time is calculated 5788 Rials per hour. Results of mixed logit model indicate cost coefficient with triangle distribution (mean -0.00036) and travel time coefficient with normal distribution (mean -0.20838). To investigate the source of VOTT heterogeneity, random coefficients analysis is used for the interaction between coefficients of time and cost and other variables revealing that only cost as a factor with three variables: number of entrance to LEZ, number of household cars, and high education are significant.

Weirs are structures that are important for measuring flow and controlling water levels. Previous studies have shown that the discharge coefficient is not constant and depends on the weir crest length, the height of weir, the upstream head, and the weir upstream and downstream slopes. In this study, the effect of these parameters on the discharge coefficients (Cd) are investigated by numerical simulation. Results showed that the downstream face slope has little effect on Cd. For 0.1<H1/w<0.4 by decreasing the upstream slope, Cd increases, where H1 is the water head on the weir crest and w is the length of the crest. Also, for the same range, by decreasing the height of the weir (p), the Cd increases. For 0.16<H1/p<2, as the length of the crest decreases, the Cd increases. By comparing the numerical simulation results to physical measurements, determination coefficient (R2) was between 0.71-0.86. In addition to Cd, extraction of other more detailed information such as water level profiles and velocity profiles at different locations are provided and comparison with other studies was carried out.

Granular materials are used in many projects such as dams, railways and breakwaters. Because the size of granular materials in these projects starts from a few centimeters and sometimes reaches to one meter, conducting laboratory experiments would be very expensive, time consuming and even impossible. For this purpose, the use of numerical modeling to investigate the effect of different parameters on the mechanical behavior of this type of material is very important. Among the effective factors, grain arrangement is investigated in this study. Thus, cylindrical and cubic grains are modeled as representative of rounded and angular grains, in two regular and irregular arrangement based on the discrete element method and stress-strain behavior, applied energy and breakage values after loading are investigated. Using the non-linear Hertz model and determining its parameters based on laboratory experiments, controlling the uniformity of grain distribution based on the number of contact points along with the dip and direction of grains, defining the breakage criterion based on Von Mises criterion and applying the breakage pattern based on particle splitting are among the features of the model used. In order to validate the numerical model, similar laboratory experiments were performed and their results were compared with each other. The results showed that the numerical model can study the effect of the arrangement of grains on the behavior of materials with high accuracy. Also, due to the existence of different shapes in granular materials, the effect of mixed arrangement was investigated on the results.

A meshfree method is presented for 3D elasto-static problems in homogenous media using Equilibrated Basic functions. The method treats satisfaction of the Partial Differential Equation independent of the boundary conditions, using a weak weighted residual integration over a cubic fictitious domain embedding the main domain. All 3D integrals break into combination of 1D library integrals, resulting in the omission of the numerical integration. Chebyshev polynomials of the first kind are used to approximate the solution function, and exponential functions combined with polynomials are used as weight functions. The weights vanish over the boundaries of the cubic fictitious domain, removing the boundary integrals. The meshless method considers some nodes for definition of the Degrees of Freedom throughout the domain. Each node corresponds to a local sub-domain called cloud, including 98 other nodes than the main central one. The overlap between adjacent clouds ensures the continuity of both the displacement as well as stress components, an advantage with respect to the formulations. The approximation order within each cloud is 4. Boundary conditions are applied over a set of boundary points independent of the domain nodes, granting the method the ability of application for arbitrarily shaped domains without the drawback of irregularity in the nodal grid. Definition of curved boundary surfaces is easily done by inserting the coordinates of some boundary points located on it. Three numerical examples with various geometries and boundaries are presented to challenge the method. The results are compared with either the available exact solutions or the FEM.

ABSTRACT Seismic waves caused by earthquakes undergo many changes when passing through different layers of soil, which can be due to the heterogeneity and spatial variability of soil parameters affecting the seismic response of the earth. The parameters in a heterogeneous soil layer are affected by a set of uncertainties. In this study, the inherent variability of the soil shear modulus parameter on the soil dynamic response has been investigated. In this research, using the random field theory method and finite difference method in the framework of Monte Carlo simulations, the effect of two-dimensional spatial variability of soil shear modulus parameter on the peak ground acceleration amplification factor and surface acceleration response spectrum has been investigated. In conventional certainty analysis, only a constant value of the mean shear modulus is considered in the dynamic model, but in stochastic analysis, the soil shear modulus parameter is considered as a random variable, which in the random field theory method, this variability is considered in two dimensions. The results obtained from the analysis show that with increasing heterogeneity and changes in the soil shear modulus, the values of the peak ground acceleration amplification factor decrease. Also, by increasing the coefficient of variation of soil shear modulus and thus increasing the heterogeneity of soil profiles, the acceleration response spectrum of the soil profile resulting from random analysis decreases.

Nowadays, solutions and effluents resulting from the activities of mineral processing plants and related industries can be considered as one of the most important resources for the production of valuable elements. Examining the extraction method and improving it, in addition to reducing the needs of modern industries, can be considered as one of the effective methods in controlling wastes and reducing environmental concerns.In this study, in the presence of molybdenum the adsorption behavior of rhenium on the Dowex 21K resin from pregnant solutions, in conditions very close to copper-containing solutions resulting from heap leaching, was investigated by Freundlich, Temkin, Dubinin – Radushkevich and Langmuir isothermal equations.The results showed that in the case of one-component solutions, the fit of the data obtained from static experiments on the mentioned equations are most consistent with the Friendlich equation and in the case of two-component conditions with its expandedform.Examination of resin capacity changes in the two conditions showed that due to the presence of the second component, due to the competition between the existing ions, the resin capacity is reduced by about 47%. Also, the examination of ammonium acetate (0.5 M) on desorption of adsorbed ions from seven resin samples loaded showed that after 7 hours, more than 92% of molybdenum was released from the resin, while during this period, the amount of rhenium desorption no more than 13% was obtained.

If an underground opening is excavated using drill and blast method, an excavation damaged zone (EDZ) will appear around the opening in which its mechanical and creep properties can be very different from the initial rock mass. The existence of such a zone in squeezing rock masses can lead the time-dependent displacements to increase. Therefore, in this paper, a closed-formed analytical solution is proposed to determine the long-term performance of a spherical opening surrounded by an EDZ. To consider the time-dependent behavior, the viscoelastic Burgers model is assigned to the rock mass. After verifying the proposed method, a parametric study is performed and the influence of various factors such as the radii of the opening and EDZ, the shear modulus, and the viscosity of rock mass are investigated. It was found that if the EDZ radius is considered constant, the displacement of the cavity with 7 meters radius, immediately and after 10 years, is respectively 1.42 and 1.57 times greater than the case in which the cavity radius is 4.57 meters. On the other hand, if the cavity radius is equal to 4.57 meters, immediately and after 10 years, the displacement of the cavity wall in which the EDZ radius is 8 meters is respectively 50% and 70% greater than the case in which this radius is equal to 6 meters. When the radii of the cavity and the EDZ are constant, if the Kelvin viscosity becomes one-twentieth, the cavity displacement increases by 115% and 173% after 1 year, respectively.

Fatality, injury, disability, and medical expense, road and vehicle damage, and mental aspects are the main disadvantages of crashes in a community. This study tries to find the influential factors, which are predictable on the severity of crashes in the rural highway using the descriptive logit model family. First, crash data are integrated with traffic data obtained from loop detectors in rural road. Second, the Ordered logit (OL) and Multinomial logit (MNL) models are developed to identify the influential factors on crash severity. Third, the models are evaluated in terms of goodness of fit. They are applied for the short-term prediction of crash severity on rural road network in Khorasan Razavi, one of the most populated province in the northeast of Iran. Results show that the overall goodness of fit for both OL and MNL models are 0.017 and 0.019, respectively that expectedly indicates the MNL model is more accurate. The independent traffic variables "heavy vehicle flow" and "speed above 85 km/h" are significant in the suggested OL model. In the MNL model, the independent variable "minimum headway" is also significant for accidents with serious damage, in addition to the significant variables "heavy vehicle flow" and "speed above 85 km/h" for the severity levels of injury and fatality.

One of the bonded contact models that is used to simulate the cemented bonds formed between soil particles in a cemented sample in the discrete element method is the "flat joint" model. There are numerous microparameters required to define this contact model between particles in modelling and the effects of each of these parameters on the material response are not clear. In this research, after performing large-scale static and dynamic triaxial tests on cemented gravel in the laboratory, they were simulated as a granular assembly in which the flat joint contact model exists at all grain-grain contacts. Then, a sensitivity analysis was conducted to determine the effect of each micro-parameter on the macroscopic response of cemented samples and to specify the most impressive micro-parameters in order to simplify the calibration process. To quantify the relationships between the micro-parameters and the mechanical properties of the sample, regression analysis of the numerical results was performed. The results show that maximum and residual shear strength of sample are mainly dependent on the flat joint cohesion and stiffness ratio. The effects of elastic modulus and stiffness ratio on the initial tangential modulus and shear modulus are significant. The Poisson ratio is affected by the flat join cohesion and stiffness ratio. The damping ratio depends more on the elastic modulus. These results can be used as a guide for modeling the behavior of brittle materials in the discrete element method. A comparison between numerical and experimental tests results of cemented granular specimens revealed that the model was able to capture the softening behavior of these materials with good accuracy.

Many shores in Iran are at risk of earthquakes, and due to the dynamic loading of the earthquake, these saturated soils are prone to liquefaction. In this study, the behavior of two-layered saturated sand with different relative densities and the interaction effects of soil and pile under dynamic loads has been considered. For this purpose, a constitutive model presented in the multi-surface framework has been applied. Also, the equations governing the saturated environment have been solved in a completely coupled way based on the finite element method. According to the obtained results, liquefaction will occur in the upper layers no matter the loading frequency when their liquefaction potential is high. Nevertheless, at depths and layers where the liquefaction potential is low, the pore pressure is strongly dependent on the loading frequency, so that with an increase in the frequency of the dynamic loads, the water pore pressure increases less. Also, based on the analyses performed under different frequencies, it is observed that at a dynamic loading frequency, increasing the pile length has little effect on the displacement of the pile head but can significantly affect the displacement of the buried parts. Therefore, the larger the ratio of the pile length in the liquefiable soil to the total length of the pile, the greater the possibility of more displacement in the buried end of the pile; And as a result, it can lead to instability of the structure.

Nowadays unlike decades ago, environment plays decisive role for using materials in construction. For example, one considerable part in a project is exploring environmental aspects as a preparatory topic. Chemicals such as cement have been used for decades in construction projects, however chemicals will lead to health catastrophe for both environment and human consequently. One considerable hitches in human life is waste materials such as sawdust which will jeopardise environment. One solution to alleviate these problems is using wastes in construction projects as substitution for cement. In this research, sawdust and zeolite were used to decrease cement use on sandy soil's improvement. Amount of materials are as follows: 4% cement (base on main soil weight), 0,1,3 and 5 % sawdust with two different sizes include powder and fibers (as supersede by cement) and 0, 10, 30 and 50 % zeolite as a supersede by cement. Results showed that zeolite and sawdust increase OMC but decrease MDD. Zeolite meets its optimum in 30% and powdered and fibrous sawdust in 3 and 1% subsequently. Finally, rupture strain will experience a sharp increase by enhancing amount of sawdust. Overall it can be concluded that longer sawdust is more effective than short one.

In this paper, the performance of Tuned Mass Damper (TMD) control system in seismic response reduction of a four-span integral bridge is investigated. Two classic analytical methods and one optimization method are then employed to calculate TMD parameters. Then, the effect of selecting each of the three methods for calculating TMD parameters on the seismic response of the bridge is studied. Three objective functions are considered for optimization procedure in MATLAB. After calculating TMD parameters, nonlinear dynamic analysis of the bridge in transverse direction is carried out in OpenSees. The purpose of this study is to compare different methods in obtaining damper parameters and to introduce a method that calculates damper parameters in such a way that the damper has a better performance on the bridge. Numerical results indicate performance of the damper is affected by its parameters and selecting the objective function. It is recommended to use the optimization method for calculate the damper parameters with maximum lateral displacement of the deck midpoint objective function. Also the results show that the more reduction of the response is related to the response corresponding to the objective function. For the studied bridge, the maximum values of reduction of displacement and acceleration of the middle deck are equal to 22.4 and 17.7%, respectively, and for the base shear is 4.3%. Therefore, the lateral displacement of the deck midpoint objective function is introduced as the best goal function

The difference in climatic conditions across the country and low investment capacity in waste management systems makes it unrealistic to establish the same prescribed design for the bottom liner of municipal solid waste landfills. In this paper, a semi-performance-based approach for the proper design of liners in these landfills has been proposed. This approach has been used in the development of the technical evaluation guidelines and environmental criteria for municipal and hazardous waste landfills. Therefore, different climatic and hydrogeological conditions were considered. The rate of leachate infiltration into leachate collection system in different climates corresponding to high, medium and low precipitation was calculated using the HELP model and considered as a representative parameter of climatic conditions. The rate of waste deposition, which indicates the size of landfill, was introduced as the length of landfill along groundwater direction. Groundwater velocity, hydraulic conductivity and thickness of the aquitard were used as hydrogeological parameters. The resulting scenarios (324 scenarios) were defined in POLLUTE v7 and the chloride migration in five liner options were modeled. The results show that as the landfill is larger and the hydraulic conductivity of the aquitard is higher, the maximum contaminant concentration in the aquifer and the required time period to reach the maximum concentration will increase and decrease, respectively, by reducing the different layers of the liner system and decreasing groundwater velocity. Finally, the optimum liner for all climatic and hydrogeological conditions is proposed based on modeling results.

Today, With The Development Of Nanotechnology, The Application Of This Material Is Very Important In Achieving Some Desired Properties In Construction Materials, Especially Concrete. In This Regard, The Use Of Nano Aluminum Oxide Can Cause Changes In Some Physical Characteristics And Mechanical Properties Of Concrete. Due To The High Hardness Of Aluminum, It Is Expected To Increase The Abrasion Resistance Of Concrete With The Help Of This Nanoscale Material. In This Research, By Examining The Effect Of Nano Aluminum Oxide On The Characteristics Of Concrete, While Optimizing The Amount Of Use Of These Materials, The Possibility Of Using Them In Special Applications, Especially Concrete Coatings And Flooring, Has Been Evaluated. The Amounts Of Nano Oxide Aluminum Used In The Concrete Mixing Plan Of This Research, In Weight Ratios Of 0.25, 0.5 And 0.75%, Replace Part Of Cement. Also, With The Aim Of Reducing The Cost And Making It Easier To Implement, The Spraying Of A Diluted Nano-Aluminum Oxide Solution In One To Four Layers On The Concrete Surface Was Also Tested. The Results Of This Research Showed That The Addition Of 0.5% Aluminum Oxide Nano Powder In Concrete Can Increase The Abrasion Resistance Of Concrete Up To 77% While Partially Improving Some Of The Tested Mechanical Properties. Also, The Results Of The Abrasion Test Showed That Creating A Layer Of Nano-Aluminum Oxide On The Surface Of The Concrete, Despite The Improvement Of Effectiveness By Increasing The Number Of Coating Layers, Is Less Effective Compared To The Mixed Design.

One of the most common irregularities in structures is irregularities in height and of the lateral stiffness. Due to the commonness of the use of the irregular structures and also different seismic response of this type of structures, in comparison with regular structures, investigating the seismic response of irregular structures has always been the subject of several research studies. The structures designed for the reduced base shear, under the design earthquake have inelastic response. To calculate the real (inelastic) displacements of structures under the design earthquake, the displacements obtained from the reduced base shear, are amplified by deflection amplification factor (Cd). The seismic codes have dedicated a Cd for each structural system. But different studies show that the dedicated Cd by the codes cannot accurately estimate the real displacements. The main purpose of this research is to propose the Cd values more specifically for more accurately estimating maximum interstory drift ratio (MIDR) and maximum roof drift ratio (MRDR) in steel special moment resisting frames (SMRFs) with soft story. Number of stories and the location of the soft story are the variables considered in this research. The Results show that the use of Cd = 5.5, recommended by the 2800 standard and ASCE 7-16 for steel SMRFs, underestimates the real MIDR (in most of stories), and also MRDR. Thus, for more accurately estimating MIDR in the considered structures, under the design earthquake, Cd = 8.5 is proposed. Furthermore, for more accurately estimating MRDR, Cd roof = 8 is proposed.

Accurate forecasting of hydrological process and taking into account their uncertainties are the major challenges in the water resources management. The goal of this paper is to forecast the monthly streamflow of Karun River at Armand hydrometric station using artificial intelligence (AI) methods. Applying the Monte-Carlo simulation (MCS) approach for considering the uncertainty of the AI forecasts and compareing their performance is another objective of this paper. In this regard, some AI-based models including Gene Expression Programming (GEP), Multivariate Adaptive Regression Spline (MARS) and Model Tree (MT) have been used. A 28-year historical data of Karun river (for period of 1981-2008) were also employed. To generate random numbers of stochastic variable, Thomas-Fairing (TF) parametric method was applied. The results of evaluating the performance of these models with indices like correlation coefficient (R), Mean Absolute Error (MAE) and Root Mean Square Error (RMSE), showed that the MT model had better performance than the others in both training and testing phases. The model accuracy indices for the MT model in training phase were R= 0.841 and RMSE= 36.789 m3/ s, while these indices for the test phase were R= 0.87 and RMSE = 44.253 m3/ s. The uncertainty results of the MARS, GEP and MT models showed that the MT model with R-factor= 1.67 and 95PPU=55.5% had the best performance for calculating uncertainty.

The growth of industries has led to an increase in pollutant sources, especially organic dyes wastewater from the textile, pharmaceutical, etc. industries have caused an adverse anthropogenic effects in water resources. Photocatalysis is considered the most desirable solution to treat these pollutions. In this paper, nanophotocatalyst (CNMS) was synthesized by stabilization of graphitic carbon nitride nanoparticles (CNNP) during the hydrothermal process on periodic mesoporous organosilica (PMO) based and its efficiency studied in photocatalytic degradation of rhodamine B(RhB) under RGBW LED photoreactor. The similarity of structural and optical properties of CNMS with BCN and PMO in the results of XRD, SAXRD, FTIR, and DRS analysis showed that the structure and framework of CNMS have been preserved and have been affected by both precursors. Optimization of parameters affecting photocatalyst activity was performed in surface response analysis (RSM) and by Box-Benken (BBD) model in three variables of time, photocatalyst dosage and light wavelength. According to ANOVA results, accuracy and validity of the quadratic model were accepted with high F-value and all correlation coefficients, the significance of p-value parameter, small% C.V. And lack of autocorrelation on D-W test results. The wavelength variable (C) and the interaction wavelength and dosage (BC) variable have the most significant impact on photocatalytic degradation. Finally, by kinetic analysis under optimal conditions, the experimental degradation value was calculated to be 90.04, which corresponds to the predicted value of 92.20% and is within the predicted interval (PI 95%), thus confirming the model’s validity.

Lateral behavior of piles is one of the most challenging design issues. While previous studies have mainly focused on rigid piles, a little attention has been paid to flexible ones. In this study, the behavior of flexible piles under lateral cyclic loading is investigated by experimental tests. For this purpose, a device was designed and commissioned for cyclic loading tests which can generate different types of sinusoidal loads. Measurement was made on the load and displacements during the cyclic loading with a loadcell and Linear Variable Differential Transducer (LVDT). The role of key parameters in cyclic loading including such as the frequency, loading interval, number of cycles, cyclic loading direction and also soil density were investigated. Moreover, post cyclic loading tests were performed to evaluate piles lateral bearing capacity. Experimental observations showed that under one way and two way loadings, the stiffness gradually increases during 100 cycles of loading while under one way without complete unloading process, the stiffness starts to decrease and then remains constant. Increasing the frequency from 0.1Hz to 0.2Hz has shown a significant effect in increasing the lateral cyclic resistance. Under the one way loading, the residual force at the pile head increases with increasing the cyclic loading interval.