مجله پژوهش های زیرساخت های عمرانی
سال ششم شماره 1 (پیاپی 10، بهار و تابستان 1399)

Asphalt construction is one of the most important parameters of asphalt pavement quality that should always be carefully considered in any asphalt pavement project. The purpose of this study was to evaluate the performance of the decision tree algorithm and artificial neural network in predicting mixture and field design parameters affecting pavement compaction in order to identify and control these parameters to control the compaction parameter value. In this study, we used data collected from relative asphalt compaction determination report, grain curve report and results of hot asphalt experiments and asphalt mix design report recovered from soil mechanics laboratory and using decision tree and artificial neural network algorithm have been proposed to predict the parameters affecting compaction. The results show that data with a distribution temperature between 126 and 155°C, fracture rates in two sides greater than 95.5%, strength (Marshall Resistance) less than 1417.5 kg-force, and Asphalt Void less than 5.45 had a good compaction rate (more than 97%). Also, three parameters of thickness, distribution temperature, and void were introduced as influence variables affecting compaction in the software.

The use of spatial structures despite the ease and speed of execution is always limited to covering the roofs with long spans. While these types of structures, which by their mechanism of load distribution to all members, have acceptable resistance to incoming loads, both dead and live, can be a good alternative for use in bridges deck. Therefore, in this paper, numerical modeling of a two-layered lattice spatial deck with different diameters and lengths of members, its behavior against dead and live loads caused by moving motor vehicles according to the AASHTO Code is investigated. The geometrical forming of the different topologies was performed using Formex algebra by Formian 2.0 software and numerical modeling of spatial decks using SAP2000 finite element software with linear static analysis. The results showed that with increasing the diameter of the members of the double-layered lattice deck from 13.94 to 19.37 cm, the cross-sectional area and consequently the stiffness of the members increase, which leads to an increase in the stiffness of the whole structure and as a result it leads to an increase in its resistance to dead loads due to the weight of the structure and to the moving loads due to the passage of motor vehicles. Also, with increasing the length of the members of the double-layered lattice deck from 1.5 to 4.5 meters, the distance between the nodes has increased and the number of nodes and members of the two layers, and their between which most of the elements of the whole structure are located at this distance has decreased, and consequently, it leads to a reduction in the dead loads of the structure and deflection due to these loads. On the other hand, because these nodes are selected from the joint type, which has freedom of movement in all directions, the reduction in the number of nodes leads to a relative decrease due to moving loads.

The Behavior of eccentrically braced frame (EBF) in terms of stiffness and ductility is between moment resisting frame and concentrically braced frame. EBF should be designed in such a way that yielding is only concentrated in the link beam at the non-linear stage. Field survey after the Sarpol-e Zahab earthquake shows that despite several defects in structural design and construction of EBFs, they have remained stable. In this study, one of the damaged buildings in the Sarpol-e Zahab earthquake, in the form of a three-story four-bay frame was modeled in Etabs and its seismic behavior in two cases; with and without infill walls was studied. The results of the analyses show that the presence of diagonal struts of infill walls reduces the axial force of the braces, the shear force, and the bending moment of the link beams. Infill walls also reduce lateral displacement and period of EBF, and they increase the lateral stiffness. Therefore, in the condition that there are several defects in the design and construction of link beams and braces, connecting the infill walls to the structure has a positive achievement. In this condition, if there were not infill walls, there would be a possibility of structural collapse.

One of the important steps in designing and implementation of tunneling projects is analyzing and managing the risks from the viewpoint of geotechnical risks. Second part of the Emamzadeh Hashem tunnel is one of the greatest civil projects in Iran that has faced with serious and important challenges in design because of the poor geological structure and geotechnical condition in excavation track. In this research, try to be after the geological studying in the tunnel excavation track, the overall risk amount be assessed by fault tree analysis. During this study, 4 important event including damage to the personnel, damage to the TBM, damage to the restraint system and deflection from the excavation track was identified and studied by using the geotechnical hazards like: encounter to fault and comminuted areas, squeezing, water inrush and tunnel instability. Results of the analysis show that reasons of the higher risk in this project are damage to the TBM and damage to restraint system. So, the higher risk should be reduced by doing some reducer proceedings like concrete injection. After these proceedings, the overall risk came to the poor area in the risk classification. According to the results, in this project, damage to the TBM and damage to restraint system have the highest risks and their risks should be reduced by doing some reducer proceedings like concrete injection. After these proceedings, the overall risk came to the poor area in the risk classification.

The progressive collapse because it can be sustained the whole structure and the safety of the lives of residents threatens that has been the focus of scientific circles over the past few years. In the progressive collapse determining the key element that most potential for failure is of great importance. Four structural steel structures with two frames and dual systems are sensitivity analyzed with two structural systems in rectangular and L- shaped planes. Based on the results of the pushdown analysis in steel moment frame with rectangular and L-shaped planes and the dual system with middle braces, the corners column and the dual system (middle and corner braces) with a rectangular plan and in the dual system (corner braces) with the L- plan the internal column has the most potential for collapse. The results show that higher-heightened structures have a better performance against progressive collapse, and the increase in the height of the models in the dual system does not have much effect on reducing progressive collapse.

One of the Practical solutions for improving subgrade soil is the utilization of additives for soil stabilization. Generally, the unconfined compressive strength (UCS) and indirect tensile strength (ITS) tests are employed for quality control of stabilized materials. These tests are time- consuming due to the time needs for curing of samples, and can also be costly if the number of samples increases. In this study, we have employed two methods including artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) to predict UCS and ITS of clayey subgrade soil stabilized with Portland cement and iron ore mine tailing (IOMT). To this end, cement content, IOMT content, optimum moisture, and curing time were considered as input parameters, and unconfined compressive strength, as well as indirect tensile strength, were considered as output parameters and in each case a dataset consisting of 100 data points were used for developing computational intelligence models. Modeling by means of these three methods confirmsthe superiority of the artificial neural network model over ANFIS model. Also, the sensitivity analysis showed that the Portland cement content and IOMT Content have the greatest and lowest effect on the predicted compressive and tensile strength, respectively.

Risk reduction and management of oil, gas, and petrochemical plants are important in terms of energy supply, financial implications, life loss, and repairs. Probabilistic analysis and reliability methods are effective approaches for calculating the risk and cost to such plants, which are composed of units with different types of equipment and structures that have different responses and consequences. One major piece of equipment in a plant that has been shut down is the flare. Depending on the height, the flares can be self-supported, guy-supported, or derrick-supported. The current study investigated the seismic probability behavior of a derrick-supported flare. An existing flare was investigated using the finite element method and incremental dynamic analysis as a case study. The different limit states of the structures were considered when calculating the fragility curves using the results of incremental dynamic analysis. The results showed that the seismic demand on the main structure of the flare stack in the ordinary seismic intensity range was not significant due to the flexible behavior of the structure.

The engineering properties of geomaterials are determined by laboratory and In-situ testing. Problems associated with sampling, especially in coarse-grained soils, limit the laboratory testing applications to determine the engineering properties of these types of soils. Engineering geological studies would help in-situ test selection as well as managing of the coast and the validity of test results. To increase the height of the Gotvand regulatory dam, determining deformation modules of subsurface material is needed, so a multistage method has been suggested and done. For this purpose, a multi-step method was proposed and performed. In the first stage, the engineering geological properties of subsurface materials have been investigated by using geological study and exploration borehole data. The subsurface materials are gravel with some sand, silt, and clay. At this stage, to determine the modulus of deformability, pressuremeter (PMT), downhole and crosshole tests were performed. Due to the coarse texture and, heterogeneity of the materials, good results were not obtained from the pressurmeter test. in the second stage and with reference to data in first stage, the extension of same strata beneath the dam has specified in river’s left bank and the measurement of deformation modules has done by plate loading test (PLT) using circular plates of 60 cm diameter. In the last stage, to investigate the effect of plate dimensions and particle size, PLT using circular plates of 120 cm diameter has been done. By changing the loading plate diameter from 60 to 120 cm, the average measured modulus decreases from 2868 to 1075 kg/cm2. In this paper, while expressing the importance of engineering geology studies in selecting suitable in situ tests, the results obtained from various tests have been reviewed.

Designing structures with sufficient resistance to loads with minimal human and financial losses are the duties of structural designers. However, various diaphragm systems have been proposed to cover the roofs of structures, and each of these types of roofs is suitable for one type of structure. Therefore, choosing the type of structure and roof of the structure is very important. The main purpose of this study is to use the decision support systems to provide a model for structural designers, contractors and other construction experts to select the roof and structure of the building. In this paper, hierarchical analysis and fuzzy Vickor techniques are used to solve this problem. The data collection tool in this research is a questionnaire and the results show that for conventional The results of this study show that buildings with reinforced concrete joist and reinforcement concrete frame structures are the most suitable and the masonry building with jack Arch roofs are the worst choice from the point of view of experts to choose the roof and the type of the frame structure. One of the most important reasons for this result is the ease of implementation and reasonable cost of Reinforcement Concrete joist and Reinforcement Concrete frame structures.

In the present research, the effects of different turbulence models and cavitation phenomenon in the stepped spillway of Siah Bisheh dam was investigated using the FLUENT model. Three standard K-Epsilon, Renormalization Group (RNG) K-Epsilon, and K-Omega turbulence models were employed for minimum, maximum, and flood discharge flows of 150, 170, and 203 cm3/s, respectively. The numerical method was validated by simulating a laboratory spillway, by which an appropriate consistency was observed. Also, the results showed that the probability of the cavitation phenomenon was more likely for a discharge flow of 203 cm3/s downstream of the stepped spillway area of the Siah Bisheh dam. Therefore, an appropriate aeration system can be utilized in suitable locations to reduce the probability of cavitation by decreasing velocity in the desired areas. Moreover, the cavitation index changed at each point of the spillway by changing the turbulence model type. Therefore, choosing the turbulence model to investigate the cavitation is of great importance. For example, the maximum velocities created in the investigated models with a discharge flow of 150 cm3/s for standard K-Epsilon, RNG K-Epsilon, and K-Omega turbulence models were 1.34, 2.32, and 1.32 m/s, respectively. The standard K-Epsilon and K-Omega models were very similar in all discharge flows and the results of the RNG K-Epsilon turbulence model were different from the other two models.

In this paper, the mechanism of scouring caused by turbulent jet out of deep drainage of power plants has been investigated. The flow velocity and discharge flow from these drains are high for fast mixing in the near field area, hence the size of these scours is also vast. Since local sediment may lead to the destruction of coastal structures, as well as the effect of spawning in the near field area, the prediction of a suitable method for estimating the location and depth of these scours in the seabed is very important. The case study is the Neka power plant located in Mazandaran near Neka city. Three-dimensional FLOW-3D model is used for simulation. Comparing and analyzing the results of numerical simulation and field data indicate that the horizontal distance of the deepest scour hole from the discharger is acceptable with a precision of 94% and the maximum depth of the scour hole with a precision of 58% compared to the bathymetry of the Neka substrate.

The purpose of optimizing the time-cost trade-off problem is to analyze the reduction of the original project time with the lowest cost. In these issues, the impact of project implementation quality on various activities has not been taken into account. Attention to the quality factor goes back to the midnineties. Many articles have been published since then. In the equilibrium discussion, the three objectives of time, cost and quality of the project are to perform a cost-sensitivity analysis of the variations in the duration of activities to obtain the best combination of reduction in activities. This is to minimize total project costs and maximize overall project quality. This paper classifies the issues of time, cost and quality trade-off and examines how to calculate the quality factor in research as well as the relationship between the three objectives of time, cost and quality in projects and project activities. The results of the analysis of the articles show that the evaluation of the quality factor in equilibrium problems can be divided into four categories. In the first case, quality is implicitly assessed through the tasks needed to modify the non-coordinated activities. In the latter case, the quality of each activity is expressed as a function of its duration and cost. In the third case, the quality of an activity in each of its possible execution modes is estimated by experts, and in the latter case, the quality of an activity is assessed by the set of indicators.