نشریه مهندسی عمران
سال پنجاه و دوم شماره 7 (مهر 1399)

The correct identification of the uplift force plays an important role in the stability analysis of gravity dams. For this purpose, a numerical model of the foundation of a gravity dam of the Guangzhao, China was made using finite element method. After simulation, the uplift force values were obtained in different positions of drainage. Require experience, the timing of calculations and the accurate determination of the boundary conditions in numerical models, have caused to the development of the tendency to use intelligent models. For this purpose, in addition to the Artificial Neural Network model (ANN) with three-layer that consists of 4 input neurons, 1 hidden layer (with 8 neurons), and 1 output neurons, a new hybrid model of Artificial Neural Network-Whale Optimization Algorithm (ANN-WOA), was developed. The values of R2, RMSE and RE% for the ANN-WOA model, were 0.998, 0.021 and 3.3%, respectively, and for the ANN model were 0.995, 0.261 and 4.67% respectively, that indicate the higher accuracy of the ANN-WOA model in the estimation of the uplift force than the ANN. In addition, the density plot box and the violin plot indicate that the point density and the probability distribution estimated data with the ANN-WOA model is very similar to that the data obtained from the numerical simulation compared with the ANN model.

In this research, the deposition process of suspended sediment in presence of bed sediment has been investigated. The experiments were carried out in the circular flume for three values of shear stress, six types of beds (one smooth bed and five coarse-grained sediments) with initial concentrations of 5, 10 and 20 g/l. The results showed that, for the same initial concentration and same rotation velocity of flume, the deposition of suspended sediments in the bed containing sediments is higher than the smooth bed. However, for specific flume rotation velocity, the bed coarse-grained increased the average of flow shear stresses. Also, the results showed that the bed sediments generally increased the critical shear stress for all deposition relative to the smooth bed. It can be explained that in the bed with coarse grain sediments, in the flow with bigger turbulence, full deposition conditions for suspended sediments still exist. The results of this study showed that for threshold critical shear stress in a smooth bed, for shear stress of less than 1.28 N/m2, sediments are in the state of the deposition threshold, but for bed containing coarse grain sediment was observed in which the suspended sediments was deposited in each flow shear stress and trapped among bed sediments. Also, it can be stated that due to the phenomenon of trapping suspended sediments in the bed containing coarse grain sediments, cannot be considered threshold critical shear stress for deposition of suspended sediments.

Estimation of the ecological level of water bodies is critical to protect aquatic ecosystems and has become a major issue in sustainable water resources planning. In recent decades, several methods are utilized to estimate the minimum ecological flow in rivers and the minimum ecological level in lakes and wetlands. In this research, a multi-objective programming model, which is a comprehensive ecological level or environmental flow estimator model, has been used to determine the ecological level of the GooriGol wetland. The model has two objective targets with two indices of water and ecosystem indicators. The level of water in the wetland has been selected as a water index and three species of important ducks in the wetland have been chosen as the ecosystem indices. The first objective function is to minimize the water index, while the second objective function is to maximize the ecosystem indices, so that more habitats are provided for aquatic ecosystems. Therefore, the aim of this model is to provide conditions for the largest ecological operations with the least amount of water. In order to solve the multi-objective optimization model, the sum of weighting technique is used. The computational results indicated that the minimum ecological level of the GooriGol wetland is 1912.6 meter. The field observations during the recent decade are in agreement with the obtained result of this research and indicates the decreasing the water level from 1912.6 m causes considerable declining in the ecological performance of the wetland.

Transient flow in a pipe would cause interaction between the fluid and the pipe wall. This interaction can be studied by a mathematical model in which the pipe considered as a beam under an applied fluid pressure loading. This model is a fluid filled pipeline that is connected to a tank in the upstream and to a valve in the downstream and undergoes forces of water hammer when there is a sudden closure in the valve. The aim is to study the possibility of instability in this pipeline when there are large lateral displacements and in the meantime small constrains. As conventional dynamic analysis models in beams which are based on the infinitesimal constrain theories (ε=∂u⁄∂x) cannot reflect the effect of large lateral displacements in the governing equations. In the governing equations the axial stresses are modeled as linear stresses and constrains are modeled by so called von Karman constrains as nonlinear constrains. The resulting partial differential equations are solved by the method of finite elements in the time domain. On the other hand the linearized equation of lateral vibration of a pipeline becomes dimensionless and by drawing the dimensionless frequencies versus the dimensionless fluid velocity, the stability of the pipeline is studied in the frequency domain. The results show that in shortly supported spans the frequency domain criterion (dimensionless fluid velocity π and 2π for pinned-pinned and fixed-fixed configurations accordingly) determines the pipeline stability behavior and so does not the critical bulking pressure.

The bridge failure caused by the local scouring phenomenon around its piers or abutments is a common phenomenon. Therefore, some methods should be used to prevent the destruction of these structures. Slots and collars are among the tools that can be used for this purpose. Therefore, by conducting 49 tests in this research, we will examine and compare the performance of these two tools with new approaches around bridge abutments using an experimental model in different flow conditions. The results show that although the most effective slot model can reduce the dimensions and depth of scour hole by 61%, it cannot postpone the start of the scouring phenomenon and take the scour hole away from the abutment surroundings. However, for the most effective collar and highest Froude number, the scour hole reaches the base point after 120 minutes from the start of the test. In this collar model, the maximum depth of scour hole is shifted to a more distant point from the abutment, and the percentage of reduction in the depth of scour hole at the base point and erodible bed is 56% and 96%, respectively.

Side weir has many applications in water distribution and regulation in irrigation and flood control. For a constant opening length, weir crest can be design as labyrinth or piano key shape to increase the developed length and discharge coefficient. Another way to increase the side weir efficiency is oblique design, which make the weir crest aligned with the diverted flow. Combining the two noted approach leads to design a side weir with longer developed crest length and aligned with flow which has high performance. In this study, piano key side weirs with different key angles were studied. Flow characteristic including deflection angle and streamlines and also discharge coefficient were studied. Results show that angled keys aligned with the flow direction, increases performance of the piano key side weir up to 12 percent in high Froude numbers. Oblique keys can reduce the turbulence usually occurs in symmetric piano key side weir and results in higher discharge coefficient. The results can be used to design a side weir with which applied in conditions with high Froude numbers such as flood control.

Today, significant proportion of movements for short distances is carried out with feet. The separation of pedestrian traffic with traffic passing through highways and highways is one of the issues that, in addition to ensuring the safety of pedestrians, also cover the flow of traffic. One of the safe passageways of these pedestrian crossings is the construction of passageways of non-level pedestrians. Therefore, the mathematical model in this research was designed with the goal of the minimum total distance of pedestrians to the passage. Model inputs were prepared using the ArcGIS software, such as applying the population to applications and obtaining distances, then by solving this model, an optimal locating of non-level passes was performed using Genetic Algorithm. In order to optimize the management of project costs, the passageways were prioritized based on effective parameters. Thus, by identifying the effective parameters such as the size of the pedestrian and the volume and speed of the vehicles, using ArcGIS, the information layers of the parameters were created and applied to the layers using the required hierarchical weighting method and this method of prioritizing the non-level crossings of the pedestrian is done. The research method was carried out on a case study and non-level crossings were locally located in the area. The importance of effective parameters for prioritizing non-level passes, pedestrian accidents, and the volume of passing pedestrians from the street had the most important factor. Finally, 21 points for constructing of pedestrian crossing is determined that prioritized based on Genetic Algorithm

In this paper, for the first time, the simultaneous analysis of wavelet transformation and the concept of the time of strong ground motion in spectral analysis of structures has been used. The purpose of this research is to optimize the calculations related to the main earthquake spectrum. Accordingly, the earthquake is filtered up to 5 steps. At each stage, the filter provides two waves of approximations and details. Because the wave of approximations is closer to the original earthquake, this wave is used for calculations. For this reason, at each stage of the filter, the number of earthquake records is half past. Subsequently, based on the concept of the time of strong ground motion in the wave of the main earthquake and the wave obtained from the wavelet filter, part of the earthquake that has a strong movement is separated. So at this stage, there was a reduction in earthquake records. After that, the spectrum of each of the waveforms is plotted. At the end, a two-dimensional 10-story structure and a three-dimensional five-story structure with each spectrum obtained from two discrete wavelet concepts and the duration of a strong ground motion are analyzed. The results show that by reducing the computation of the spectrum by more than 93%, the structure can be analyzed with an error less than 4%. It can be said that the proposed technique is one of the best techniques presented in the optimization of calculations related to spectral analysis of structures.

Seismic responses of buildings are amplified due to torsion. To account for the effects that cause torsion and are not considered in the design process of buildings, the seismic codes introduce “accidental design eccentricity (ADE)”. In this study, the adequacy of the Iranian Standard No. 2800 provisions about the design eccentricity is investigated. To this end, the 5-story torsionally-stiff and torsionally-flexible buildings with dual lateral load resisting system are studied. The mass eccentricity in plan-asymmetric buildings is assumed to be equal to 0.10b and 0.20b where b is the plan dimension. Nonlinear time history analyses are performed using far-field (FF), non-pulse (NP) and pulse-like (FD) near-field records for the models in two cases. In the first case, the effect of the ADE on the seismic demands of symmetric and asymmetric-plan building is investigated. Finally, to consider what happens when an actual accidental mass eccentricity (AME) is introduced in an already designed building, the mass centre of the buildings is shifted by ±0.05b simultaneously in both directions and the buildings are analyzed for the earthquake sets described above. The results indicate that the provision related to the accidental design eccentricity has little influence on the inelastic seismic responses for torsionally-stiff buildings and can be ignored. Also, the accidental mass eccentricity has more influence on inelastic seismic responses of torsionally-flexible buildings but the accidental design eccentricity has less influence on the reduction of seismic responses. Therefore, it seems that the accidental design eccentricity needs to be modified for torsionally-flexible buildings.

The purpose of this study was to compare the performance of Fe2+ activated persulfate and electro-persulfate process in Acid Blue 25 removal from aqueous solution. For this reason, the effects of different parameters including pH, dye, sodium persulfate and ferrous sulfate concentrations were investigated. The removal efficiency of 92% at the time of 60 min was obtained at pH= 3, dye concentration= 50 mg/L, sodium persulfate concentration= 500 mg/L and Fe (II) sulfate concentration= 100 mg/L for Fe2+ activated persulfate system and the removal efficiency of 95% at pH= 5, dye concentration = 200 mg/L, sodium persulfate concentration = 500 mg/L and ferrous sulfate concentration = 100 mg/L for electro-persulfate system by means of graphite materials as the neutral electrodes. COD removal efficiency in Fe2+ activated persulfate and electro-persulfate in the mentioned conditions were 90% and 89% in 180 minutes, respectively. Moreover, the result of process kinetics showed that using electrochemical process improved the reaction velocity from 0.0016 to 0.0487 mg/L/min. The comparison between these two-process showed that using electrochemical process improved dye removal efficiency by 4 times.

The stratified reservoirs are forming due to natural phenomena such as sediment current or a significant change in the quality parameters of water in terms of salinity, dissolved oxygen, heavy metals, etc. Understanding the outflow pattern and its interactions in stratified reservoir according to different discharges from the deep conduit and application for the operation of its system in Gotvand Dam using by a physical model is the main goals of this research. An undistorted physical model with a 1:40 scale from the deep duct structure with the details was established. This scale is calculated based on the Richardson number and the same density conditions in the model and prototype. Laboratory scenarios of the physical model were designed and implemented in two sections to allow changes water level in the reservoir and maintain it. The results of experiments with different outflow rates revealed that salinity of the layer in front of the deep conduit plays an important role in the salinity of the depleted stream, and other layers in different level of the reservoir have not affect in changing this amount. Also, the pattern of the streamline formed towards the output is under very stable conditions without expanding to other layers. This issue was clearly recorded in addition to measuring by imaging from the model. Regarding the saline outflow from the layer in front of the deep duct, falling of the low dense upper layers was performed and the mixing in other layers was not observed.

The supercritical flow as the inflow at upstream of the vertical drops can produce a considerable impact, destruction and erosion at the downstream of drops influence by fall and collision. Therefore in this study, with the aim of evaluation and prediction of the general behavior of hydraulic parameters in vertical drops with the supercritical flow at upstream, 55 experiments were carried out with various discharges and Froude numbers. The experimental results indicated that in the supercritical flows, by increasing the relative critical depth and Froude numbers, the relative length of drop, the relative length of splashing and the relative total length of the drop were increased. However, by increasing the relative critical depth and Froude number, the relative depth of the pool initially increases and then decreases, and the relative energy loss is initially reduced and then increased. By increasing the Froude number at a constant relative critical depth, the relative length of the drop, the relative length of splashing, the relative total length of drop and the relative energy loss increases, and relative depth of the pool decreases. Also, in a constant Froude number, by increasing the relative critical depth, the relative length of drop, the relative length of splashing, the relative total length of the drop and relative depth of the pool increase, and the relative energy loss decreases. The results of the present study with the larger range of Froude number were compared with the previous studies and were studied the reasons for the agreement or disagreement.

Earth dams are always one of the main components of water conservation projects. Nowadays, accurate estimation of piezometric pressure and seepage discharge in earth dams using numerical models and artificial intelligence (AI) approaches is one of the fundamental steps in their design studies. In this research, soft computing models including genetic programming (GP), M5 algorithm and group method of data handling (GMDH) have been used to predict the piezometric pressure in the core and the seepage discharge through the body of Shahid Kazemi Boukan Earth Dam. For this purpose, the information recorded in the last 94 months has been used. The results showed that all of the applied models have permissible level of accuracy in the prediction of seepage discharge and piezometric pressure. The best performance in the piezometric pressure estimation is related to the M5 algorithm with a coefficient of determination (R2) of 0.95 and root mean square error (RMSE) of 0.86. The GMDH by considering the two units (months) delay time and with R2= 0.92 and RMSE=1.541 modeled and predicted the seepage discharge, which was more accurate than other models. In general, increasing the time delay in the input information of models generally increases the performance of proposed models.

The load-carrying capacity of the aggregate piers increases by circumferential confinement created by the surrounding soil. In soft clay soils, the amount of confinement is usually not sufficient to develop a load-carrying capacity. Because of that, it is practical to use geosynthetic reinforcement aggregate piers in this type of soils. This paper intends to evaluate the use of vertical steel bars as an alternative for geosynthetics. In this study, some small-body laboratory tests were performed on floating aggregate piers with diameters of 80 and 100 mm and a length of 400 and 500 mm, respectively reinforced with vertical steel bars. Moreover, two-dimensional numerical modelling using the Plexis software was conducted. The results show that using the bars with more stiffness leads to more increase in load-carrying capacity. Reinforcing the full length of the aggregate piers, compared to half-length, will further improve the load-carrying capacity of the aggregate piers. In the early stages, by applying the load, the stone aggregates tend to compress, so load-carrying capacity increases and by continuing this process, the tendency to the occurrence of lateral bulging is seen and due to the low resistance of kaolin clay to the bulging, the increase of load-carrying capacity is negligible. Also, numerical modelling results show that the floating aggregate pier penetrated into soft clay soil in the full-length case, and the failure state changed from bulging to slip.

In this paper, the overturning response and the rocking motion of free-standing intake towers is investigated under seismic pulses. Briones dam’s intake tower is selected for this purpose. The intake tower is modeled in two free-standing and anchored conditions, that in the free-standing model, three different frictional conditions are considered between the bottom of the tower and the underlying foundation. The frictional conditions include the coefficients of friction as: 1) μ = 0.58; 2) μ = 1.73; 3) μ = ∞. The intake tower is modeled three-dimensionally in three dry, submerged and semi-submerged states. The water-structure interaction is considered by the Eulerian-Lagrangian approach. In order to validate the modeling, the results of rigid and flexible blocks obtained by other researchers and the results obtained by the adopted software, i.e. Abaqus, are compared. The tower overturning responses include the tower’s top relative displacement, the base sliding, and the tower’s base opening, which are extracted and analyzed under seismic sine pulses with three time periods of 0.5s, 1s and 1.5s, and intensities of 0.2g to 1g. It is shown that the presence of the surrounding water has a significant effect on the overturning responses. Also, the tensile stresses in the free-standing state decreased by more than 50% compared to the anchored one.

The present study aims to investigate the use of agile project management in road construction projects the population consists of all project managers, specialists, experts, consultants and contractors of road and urban planning department of Isfahan province who are 150 persons. Number of 108 persons are selected as the statistical samples by the Cochran sample size formula and convenience sampling. The tool is a researcher-made questionnaire which is based on the 5-point Likert scale by the researcher under 5 dimensions (managerial-organizational, skill and competence, knowledge management, human resources, cost, project complexity) and is prepared in 30 items. The face validity is confirmed by a number of respondents and content validity is verified by the views of the experts. In addition, factor analysis is used to determine the construct validity of the questionnaire. The reliability coefficient of the questionnaire is estimated (0.891). Data analysis is performed in SPSS software. In addition, the ranking of the factors indicated that knowledge management dimension with score of 4.02, human resources dimension with score of 3.69, the project complexity with score of 3.50, the managerial-organizational dimension and the cost with score of 3.37 and the skill and competence dimension with score of 3.06 are ranked first to fifth respectively.

All costs within the life-cycle of a building are known as its life-cycle costs. In the design process of a building, the use of a lower initial cost index to select an option among others with similar performance may not lead to an economically optimal choice during the life-cycle. Hence today, building designers and investors require a tool to estimate life-cycle costs at the conceptual design phase to elect an economically-efficient option. The purpose of this study is to provide a framework to estimate life-cycle costs of a building at the conceptual design phase based on building information modeling. For this purpose, the costs of the building's life-cycle, including initial costs (cost of supply and installation based on Iran's national price list and shipping costs), repair and maintenance costs, operating costs (energy consumption) and salvage value at the end of the building’s useful life are regarded in the estimation of its life-cycle costs. The application of the proposed framework was then evaluated and approved for designing a residential building in Tehran. The application of the proposed framework for designing a residential building in Tehran was assessed and validated on two modelsو and the results showed that by increasing the initial costs in the second model by 75%, its annual operating costs decreased by 54% and Total life-cycle costs have dropped by 8% after 18 years. In this way, building designers can estimate the life-cycle costs of a building at the incipient stages of design and improve its design.