AMIRKABIR JOURNAL OF CIVIL ENGINEERING (AMIRKABIR)
Year:2020 | Volume: | Issue: |Papers Count:17

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.

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.

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.