نشریه مهندسی عمران
سال پنجاه و چهارم شماره 10 (دی 1401)

The piezocone penetration test is commonly used to measure pore water pressure, identify a soil’s profile and estimate its material properties. Depending on the soil type, ranging from clay to sand, undrained, partially drained, or drained conditions may occur during cone penetration. In silt and sand–clay mixtures, the piezocone penetration is characterized by partially drained conditions, which are often neglected in data interpretation. The effect of drainage on piezocone measurements has been mainly studied experimentally. Numerical analyses are rare because taking into account large soil deformations, soil–water and soil–structure interactions, and nonlinear soil behavior are still challenging tasks. In this paper, using advanced hypoplastic constitutive model and ABAQUS finite element software large deformations and nonlinear behavior of soil during penetration was modeled and behavior of firoozkooh saturated sandy soil in different drainage conditions and relative densities was analyzed. Then, using the obtained results, the range of influence of cone penetration on the surrounding soil and the range of partial drainage conditions for Firoozkooh sandy soil were investigated. It was also shown that drainage condition and density had a significant effect on the affected soil area and the trend of changes in excess pore water pressure.

Water supply networks are considered as critical infrastructures in urban systems, the use of which has always been associated with many challenges. In these networks, the problems such as pipe breaks, water leakages and, non-uniform distribution of nodal pressures are considered as frequent challenges. In this study, a time-based scheduling approach for the use of pressure control equipment in the water network has been presented. In this regard, two operational scenarios consisting of simultaneous use of individual pressure reducing valves in the first scenario (individual scenario) and the hybrid use of pressure reducing valves with a variable speed pump in the second scenario (hybrid scenario) have been investigated. In this case, Operational programs have been developed with the aim of achieving the benefits of pressure management based on providing minimum temporal and spatial pressure variations, using a genetic algorithm as an optimization tool. Finally, the proposed strategies based on dual scenarios were validated in the context of a theoretical network as well as a real network. The optimal scenario was determined by calculating the hydraulic evaluation indicators of the network. The results show that the simultaneous use of pressure reducing valves with a variable speed pump (hybrid scenario), has been more effective in reducing pressure variations and increasing desired pressure coverage, in comparison with the individual scenario.

The behaviour of steel circular hollow section (CHS) T-joints under combined fire load and out-of-plane bending (OPB) is investigated. A review of the literature indicates that the subject has not been previously considered by researchers. The authors carried out the first laboratory experimental study on OPB behaviour of simple steel tubular T-joints under standard fire. The results of an experimental and numerical study performed on three small-scale steel tubular T-joint specimens is reported. One specimen was tested at ambient temperature under quasi-static incremental OPB moment in the brace and the other two specimens were tested under OPB moment plus exposure to ISO-834 standard fire.In order to have a deeper insight into the strength and failure mechanism of steel tubular T-joints under fire, their OPB behaviour was also studied using a coupled mechanical-thermal finite element modelling. The numerical model was validated against the experimental results and reasonable agreements were achieved. A parametric study was then performed on the OPB fire behaviour of full-scale steel tubular T-joints. The results showed that the superimposed OPB ratio in the brace and the diameter ratio parameter had more pronounced effects on the fire response of the joint as compared to other geometric and loading parameters. Increasing the the diameter ratio parameter from 0.2 to 1, reduced the joint’s residual rotation by 56 % and increased the critical temperature by 23 %. By increasing OPB ratio from 0.2 to 1, the residual rotation increased by 245 % and the critical temperature decreased by 37%.

Weather conditions are one of the most effective factors on traffic volume. So the main purpose of this study is to identify the effect of variables related to seasonal changes in climate parameters included visibility (m), wind speed (m/s), rainfall (mm), snow depth (cm) and temperature (℃) on of Lowshan- Qazvin freeway light-vehicle traffic volume. In this research, traffic and meteorology data is evaluated on three separate sections. In order to examine the existence of differences between the different climatic groups and the number of Light vehicles, U-Mann-Whitney or Kruskal-Wallis statistical tests were employed. In addition, in the proposed research method, two-way analysis of variance test was used to statistically analyze the relationship between the combination of two climatic variables with traffic volume in the studied sections. The results showed that the amount of traffic in all parts decreased by an average of about 18% with a decrease in visibility. Also increasing rainfall only in warmer seasons of spring and summer has led to a decrease in traffic volume. The results of statistical analysis of the combined effect of two-way meteorological variables on the amount of traffic in general showed that in the Kouhin-Mahmoudabad nemune section combination of rainfall and snow and snow with wind speed has affected the number of vehicles. The outputs of the proposed method, while revealing changes in freeway traffic volume under different climatic conditions, provides useful information to the relevant authorities for management and planning of traffic volume.

Maintenances are necessary to ensure the safety and serviceability of existing bridges. With the increasing number of existing bridges, maintenances cost a large proportion of financial fund and have significant impact on environment. Bridges like any other structure and perhaps more than most of them are affected by environment. Because they belong to sensitive and high costly structures, failure to maintain them will have devastating effects. Bridges are needed continuous maintenance in order to service properly during its life cycle. Therefore, in this study, the issue of maintenance and repair of urban bridges in Mazandaran province has been studied with regard to life cycle cost and reliability of bridges. To do this end, a mathematical programming model which is include minimizing maintenance and user costs as well as maximizing system reliability. In order to solve the proposed model, a multi-objective particle swarm optimization algorithm is developed. Also, a sensitive analysis is done on failure rate. Results show that increasing in this parameter cause to increasing cost and decreasing reliability, This indicates that the proposed algorithm is working properly and the results of this research can be trusted.

In recent years, the use of embankment dams with asphalt concrete cores has become more popular in comparing with clay core dams owing to its implementation restrictions. Because in this type of dams, asphalt materials form the core of the dam and granular materials are used as a filter around the asphalt core. Therefore, investigation of behavior at the contact surface between these materials is of great importance. In this research, using large-scale direct shear experiment and applying vertical stresses of 1, 3 and 5 kg /〖cm〗^2 in both dry and saturated states, the mechanical behavior at the contact surface of asphalt materials and gravel filters has been investigated. The effect of parameters such as material density, gravel grain shape and bitumen type has been investigated. The results showed that the shear strength at the contact surface of the materials decreases with increasing the moisture content. Changing the shape of the filter material grains to the angular increased the shear strength of the contact surface and the ratio of maximum stress to residual stress at the contact surface for dry and saturated states with different relative densities showed that this ratio increased very little at low densities

In this study the sedimentation of nano silica (NS) on graphene oxide (GO) sheets using tetra Ortho silicate (TEOS) hydrolysis in water/alcohol solution and its performance in cement mortar has been investigated. First, the possible interaction between nanoparticles using UV-Vis spectroscopy and electron microscopy (TEM) spectrum is examined. Then, the mechanical properties of the composite material consisting of nano silica and graphene oxide (NS&GO) production was investigated by the Molecular Dynamics Simulation method. The application of nanoparticles on mechanical properties of mortars with and without natural pozzolans has been studied in both individual and composite forms. The dispersion of NS particles on GO sheets can be seen using TEM images through chemical pretreatment and without using surfactants. The results obtained from Molecular Dynamics Simulation indicate a 75% increase in the amount of tolerable stress and a 250% increase in the Young’s modulus of the composite material relative to single NS particles. The 28 days compressive and tensile strength of mortars containing composite nano materials also increased by 31% and 100%, respectively, compared to the control design. Proper dispersion and distribution of nanoparticles, nano silica nucleation property, graphene oxide stepping properties and high zeolite pozzolanic activity have improved the mechanical properties of mortars.

Mechanized shallow tunnelling in urban areas and soft grounds leads to horizontal and vertical displacements at the host materials of the tunnel and causes the ground settlement due to tunnelling which can have undesirable and even destructive impacts on surface structures and subsurface Facilities. In the present study, ground settlement induced by the mechanized excavation of Tabriz Metro tunnel, Line 2, is considered as a case study using semi-experimental, analytical and numerical methods, and the impact of different factors will be investigated. For this purpose, a section of the studied tunnel was selected for evaluating the settlement via mentioned three methods, and the results were analyzed and compared with the real settlements, measured during the tunnel excavation. The results show that the semi-empirical method releases relatively higher values of settlement because of intrinsic and fundamental specifications of the method while the analytical and, especially, numerical methods generally provide logical and reliable outcomes because of the utilization of more parameters of tunnel and host soil such as geotechnical characteristics of host soil and geometrical properties of the tunnel. In this regard, to emphasize the valuable capabilities of numerical methods, the effect of several factors on the amount of settlement was studied via FLAC 2D software. The outcomes showed that the ground settlement increases when the elasticity modulus of grout and the elasticity modulus of soil decrease as well as when the surface load increases and the groundwater level is dropped.

Recently, nonlinear viscous dampers have been widely used to improve the seismic performance of structures. These dampers dissipate the kinetic energy caused by the earthquake by producing a damping force. These dampers are designed in such a way that the force is proportional to the velocity. The Maxwell model is the most common model for modeling the behavior of nonlinear viscous dampers. In this model, the damping coefficient, the velocity exponent and the axial stiffness of the dampers are the key parameters. In most previous studies, the uncertainty of the underlying parameters in behaviour of viscous dampers has been ignored while it can has a significant effect on the seismic response of structures. In this study, first, the reliability analysis of a shear frame equipped with a nonlinear viscous damper was performed using the Monte Carlo sampling method. The results show that increasing the maximum drift from 0.015 to 0.02 reduces the probability of failure by 72%. Then, reliability-based sensitivity analysis of the studied frame was performed in order to determine the most effective random variable on the reliability of the frame. The results show that the velocity exponent is the most effective random variable on the reliability of the frame. Also, results indicate that importance of random variables depends on the used limit state function in the reliability analysis. For example, the imporatance value of the damping coefficient is 59% and 9.5% less than the velocity exponent with respect to the maximum drift of 0.015 and 0.025, respectively.

The aim of this study is to evaluate the effect of nitrogen oxides, volatile organic compounds, and ambient temperature on ozone concentration in the city of Tehran. In this regard, the hourly concentration for ozone and nitrogen oxides for the first half of 1396-98 were used. Also the 2-weeks averaged data for BTEX monitored by passive sampling method and 30-minutes averaged temperature data monitored at Mehrabad airport were used. First, daily variations of ozone and nitrogen oxides with their corresponding indexes were analyzed. Then, the role of nitrogen oxide and nitrogen dioxide on ozone concentration were investigated by statistical analysis. The results show a meaningful relationship between ozone and both nitrogen oxide and nitrogen dioxide with the coefficient of determinations of 0.83 and 0.8, respectively. Although an apparent increasing trend in ozone concentrations has been observed in recent years, however, no similar trends are detected for nitrogen oxide and nitrogen dioxide. The limited available data for BTEX, shows a 17.3% increase from 1394 to 1398. The daytime temperature analysis for the 30 days with the highest ozone concentrations showed an increasing trend from 1396 to 1398. Therefore, it can be concluded that the increasing trends of BTEX concentrations and ambient temperature were probably responsible for the increasing trend of ozone concentration in the study period.

Accuracy in pouring concrete, concrete density and also the appearance of concrete as an exposed material is always a concern of designers and executors of construction projects. Self-compacting concrete with weight compression properties can always be one of the options available to designers. The variety of materials used in self-compacting concrete, including recycled materials, with pozzolanic properties and fillers to achieve rheological and mechanical goals, is one of the challenges that designers face. Also, accurate determination of mixing ratios and their results is very time consuming and costly. Using soft computing and neural networks inspired by the biological structure of the human brain, computer science seeks to increase speed, accuracy, and cost reduction to prevent malicious experiments. In this study, with the help of ANN and LSTM networks, using 320 samples of self-compacting concrete with dispersion and comprehensiveness of common materials used in it by various researchers, tried to predict 28-day compressive strength of self-compacting concrete, evaluate performance and increase accuracy by 6 different training algorithms. In total, about 200 repetitions of training were performed on 320 samples of self-compacting concrete with 14 characteristics, which by comparing the best results obtained from training algorithms, best performance with root mean square error of 4.97 and correlation coefficient of 0.9484 in the test, for the network. ANN was reported with the Beyesian Regularization training algorithm, which indicates the high accuracy of that network.

In recent years, reinforced concrete (RC) shear walls have been welcomed by structural designers with regard to their desirable seismic performance in terms of ductility. Most of the time, creating an opening in the RC shear wall due to the architectural issues, which is inevitable, results in reducing the strength, ductility and stiffness of the wall.For this reason, the issue of retrofitting the RC shear walls is developed to solve these weaknesses. In this paper, an RC shear wall with opening was retrofitted with eight different schemes of carbon fiber reinforced polymer (CFRP) sheets in ABAQUS software which were:1-vertical and horizontal CFRP sheets around the opening in RCSW1 sample, 2-horizontal CFRP sheets to increase the shear capacity in RCSW2 sample, 3- vertical and oblique CFRP sheets to prevent diagonal cracks in RCSW3 sample,4-horizontal and vertical sheets in corners of the opening in RCSW4 sample,5-horizontal and oblique CFRP sheets to reduce diagonal cracks and the strain at the foot of the wall in RCSW5 sample, 6-vertical CFRP sheets to increase flexural capacity in RCSW6 sample,7-vertical, horizontal and diagonal CFRP sheets in RCSW7 sample, and 8- horizontal and vertical CFRP sheets in whole of the wall to increase flexural and shear capacity and improve ductility in RCSW8 sample. All samples were subjected to cyclic lateral loading.Various parameters such as stiffness, displacement, ductility and failure were selected to evaluate the results.Results showed that the RCSW8 in comparison to the control sample had a 12% increase in the bearing capacity.

In this paper, the irregularity effects in the initial directions of the seismic loading on the nonlinear time-history responses of the Shohada dam have been investigated. The maximum cross-section of the dam has been simulated by the 2D finite element method under the normal lake level conditions. The near-fault acceleration record of the Tabas earthquake has been applied as dynamic input motion to the two-dimensional numerical models. Numerical analysis has been conducted in the Newmark explicit time integration scheme framework. The main three patterns of horizontal, vertical, and oblique directional seismic loading are considered to investigate the effects of the initial directions of seismic motion propagation. In each case, the seismic responses are compared to the conventional seismic loading responses in the horizontal direction from the upstream (reservoir) to the downstream of the dam. The hardening soil model with small strain (HS-small) and Mohr-Coulomb model was used to model the dam's body and the foundation materials. In most 2D simulations, the initial direction of the input seismic movements has been only in one or two dimensions and in the horizontal or vertical orientation. This study has attempted to compare these traditional seismic loading patterns with other possible states in 2D numerical models. The present study results show that the seismic loading mode with the initial direction of inclination of 45 degrees has the worst and most significant effect on the seismic response of the dam compared to the traditional method of horizontal loading.

As the population and urbanization increase, policymakers consider urban water management more often; however, these policies can positively and negatively affect the urban water system. In recent years, following the increase in the water crisis in Isfahan province, pressure management has been applied to reduce access to water as a new water demand management policy in different cities of this province. The present study investigates the environmental effects of such policy in the new city of Baharestan (Isfahan province) during the 2018-2036 period, using a life cycle approach and different percentages of available water shortages. SimaPro software is used to conduct the life cycle assessment for processes such as network failure and energy consumption at the pumping station. The life cycle assessment is performed based on the conditions of the study area. The results show that significant part of the environmental effects in the water supply and distribution network is caused by network failures, which, compared to energy consumption, have many effects on most midpoint and endpoint environmental effects. So that the endpoint environmental effects of network failures are, on average, 2.2 times greater than that of pumping systems. The water distribution network and pumping system can minimize their environmental impact by implementing a pressure management policy. With pressure management, the endpoint environmental effects in both short-term and long-term scenarios are reduced by 14.7% and 20.2%, respectively.

Nowadays, the ordinary Portland cement (OPC) industry causes to extensive environmental consequences due to consuming huge amounts of fossil fuels. This necessitated researchers to introduce a novel group of binders called “Geopolymer cements” or “Green cements” with higher performance and lower pollution compared to the OPC. Thus, in this research, the effect of using two types of alkaline activators such as sodium hydroxide (NaOH) and calcium carbide residue (CCR), for stabilization of clay soil (CL) has been investigated. Initially, the chemical compositions of soil, recycled glass powder, calcium carbide residue, and sodium hydroxide were obtained via X-ray fluorescence (XRF) test. Then, the mechanical behavior of different unstabilized, geopolymer-stabilized, and OPC-stabilized samples has studied using unconfined compressive strength (UCS) test. The effects of several parameters such as the type and concentration of alkaline activators, the curing times (7, 28, and 91 days), and the initial synthesis temperature (25 and 70 ˚C) on the UCS and failure strain of samples have been assessed. Moreover, in order to studying the microstructure of samples, the scanning electron microscope (SEM) images and energy dispersive X-ray (EDX) analysis of selected samples have been used. Results showed the effective stabilization of soil geopolymer, using both alkaline activators. However, the CCR will be more appropriate if environmental and economic problems considered.

The use of concrete in industry is expanding. Self-compacting composite concrete is known as a cement composite with high performance and adhesion. This composite has a lot of psychological capabilities and efficiency, so that the use of this concrete, in addition to reducing construction time, also reduces costs. Self-compacting composites fit into the mold without the need for vibration and pass through the smallest seam. In this study, the effects of adding microsilica, fly ash and GGBFS pozzolan on the mechanical properties of self-compacting cement composite were investigated in 8 mixing designs. In making samples, 3 alternative cement additives at the rate of 10% were used in different mixing designs. In the compressive strength test, the sample with 10% microsilica increased the resistance by 5.4% more than the reference sample, which showed that the addition of microsilica increases the strength and water absorption in the samples. However, these pozzolans reduce the flow of self-compacting concrete. On the other hand, in the design of air ash mixtures, the resistance was reduced, but no significant changes were observed for slag. In total, other experiments such as tensile strength, flexural strength, water absorption, capillary, ultrasonic pulse velocity and impact resistance were performed on the mixing design.

Bridges are structures with great importance, and any interruption could cause financial damage and even life-endangering people's life. Based on the type of structure, bridges can be divided into conventional, cable, and movable bridges. Space limitations in urban areas and the establishment of the cities around the rivers attracted designers and engineers to these types of bridges. Considering the importance of the foldable bridges, seismic behavior of the bridge under subjection to near-fault ground motions has been investigated in this paper. Inheriting impulse effects in near-field contents is the main difference with far-field records. The total length of the bridge is 40 meters and consists of three movable spans, which are 3.65, 2.7 and 3.65 meters long. To study the seismic behavior of the bridge, at first modal analysis has been performed in ABAQUS built model and then under subjection to near-fault ground motions, which has been matched according to issue No.463 seismic time history analysis performed. The acceleration response, base shear, and vertical deflection of the bridge induced by perpendicular horizontal excitations were calculated and extracted. The destructive effect of the Varzeghan earthquake is more than other earthquakes, and the numerical value of acceleration response, vertical displacement, base shear, and tower drift is considerably higher than other earthquakes. The connection zone of the tower to the deck is vulnerable to seismic loads, and plastic hinges have been formed.

The Management and Planning Organization is responsible for classifying of contractors and uses criteria to assess the ability and competence of contractors. One of the factors evaluating the productivity of a project is time and the impact of the contractor's performance on this index is undeniable. In this study, a model for ranking contractors with the approach of reduction in delays in construction projects is presented. In this model, in addition to the criteria of the Regulations for Competence of Contractors of the Plan and Budget Organization, according to extensive research in previous studies and the opinion of relevant experts, using the FMEA method, four other criteria are identified as effective criteria for delay and severity to select a contractor. Eight criteria were modeled through genetic algorithm method so that the existing documents of contracting companies in the Isfahan Municipality Deputy for Urban Development were collected and considered as model input data. After analyzing them with the model and comparing the qualification score with the existing score The Company, the final model was extracted.Finally, by calculating the qualification score and ranking in the proposed model, the relocation of a number of companies and the decline from the previous position was seen due to unauthorized delays, so that sometimes it even led to a change in the company's rating. Comparing the qualification score of the two models, a change in slope from 1.3% to 8.9% was also seen, which indicated the effect of the proposed criteria on the qualification score.

Damage sustained of electrical transformers in past strong earthquakes led to irrecoverable and severe economic losses of them. The seismic performance evaluation is associated with the loss of proper functioning of the transformer. This study deals with modeling existing isolated electrical transformer structures to evaluate the effects of variables that may affect the seismic performance and dynamic characteristics. The results probabilistically determine the seismic performance acceptability of study isolated electrical transformer structures based on the impact of key structural response parameters on the seismic performance of the transformer. Analyses of systems for a wide range of parameters are performed. The effects of horizontal and vertical near-fault pulse-like ground motions, the displacement capacity of the seismic isolation system, limit states of electrical bushings, and details of the isolation system design are considered. Also, the probability of failure of the transformer under the near-fault excitations with pulse-like characteristics is investigated. The results of this study demonstrate that three-dimensional seismic isolation systems can improve the seismic performance for a wide range of parameters and can be further effective compared with only horizontal seismic isolation and offer the lowest probabilities of failure for all cases of transformer and isolation system parameters.

Classification of soil is a function of the geological conditions of the region, which according to the 2800 earthquake standard, is itself a function of average shear wave velocity, average standard penetration number and average undrained shear strength in cohesive soils in different layers to a depth of 30 meters from the surface. Due to the uncertainties in the mentioned parameters and also considering that the values of these parameters in the real material are not the same as the values obtained from the experimental tests, so for this and determination of these parameters requires the use of statistical and probabilistic methods. Due to the computational complexity of statistical and probabilistic methods, in this research, a fuzzy inference system has been used to the decision of the choice of soil type, which can consider uncertainties without the need for complex mathematical calculations. For this purpose, after determining the effective parameters in determining the soil type, triangular membership functions were selected for them and finally, a fuzzy inference system was designed. A comparison of the results of this study with the results of field research shows the efficiency of the proposed fuzzy inference system.