Amirkabir Journal of Civil Engineering
Year:2023 | Volume:55 | Issue:9|Papers Count:10

The development of urban environments and the excessive increase of urban population have increased the amount of energy consumption and as a result, the temperature of urban environments has increased. The phenomenon of increasing the temperature of cities compared to the temperature of suburbs is called the urban heat island (UHI). Energy waste, financial resource consumption, climate, and ecosystem change are the most important adverse consequences of the phenomenon of UHI. In this research, the causes of UHI, and methods to reduce this destructive phenomenon with the approach of using cool pavements, have been comprehensively studied. Research has shown that UHI can be evaluated using fixed, survey, and remote methods. One of the most effective actions is the use of reflective materials and the use of cool pavements on the roads to reduce the temperature of cities and reduce the effects of the destructive phenomenon of UHI. Results show that with the use of cool pavements, the ambient temperature and the surface temperature of the pavement surface can be reduced up to 2 ° C and 13 ° C respectively improved. The use of light-colored cement and aggregates and additives such as titanium dioxide, zinc oxide, aluminum oxide, and fly ash has been effective in reducing this phenomenon. By increasing road surface permeability, increasing the surface reflection coefficient, increasing the thermal coefficient, and decreasing the pavement thickness, the pavement surface temperature can be reduced, and the undesirable phenomenon of UHI can be prevented.

As the purpose of monitoring the project is to make accurate decisions that can have significant effects on the project’s success, predicting the project’s characteristics becomes more important. According to experts, schedule delays are a frequent issue in many construction projects. This research aims to propose a model that can address project scheduling problems. For this purpose, this study proposes new applications of recurrent neural network architectures based on short-term long-term memory (LSTM) prediction models. Subsequently, the prediction results of the presented models are compared and verified with the historical data of a real project. The data used in this study has been obtained from the South Extension Project of Tehran Metro Line 6. The project started in October 2016 and ended in July 2018, lasting for a total of 21 months. In this study, the training dataset consisted of the initial 14 months' data, which accounted for 83 percent of the total data. We used the construction project progress as a forecasting variable. To evaluate the performance of LSTM models, we used the mean square error (MSE) metric as the evaluation criterion. The results show that the model accurately forecasts the project’s future progress based on its past progress.

One of the new methods for flood zoning is Geomorphological Indexes (GI), which requires little hydraulic-hydrological data. In this method, the standard flood map for a small part of the studied basin is used to increase the accuracy.  The flood peak flows are different due to different standard flood map locations. Thus, the flood zoning results will be different. For this reason, it is necessary to select the best location for the standard flood map. In this research, the standard flood maps were used in the Kashafroud sub-basins including Radkan, Jaghargh, and Agh-Darband. The results showed that the Agh-Darband sub-basin located at the end of this basin had the best results for the standard flood map. The flood zoning results in the sub-basins showed flood zoning high accuracy based on the true positive rate (RTP), and the area under Curve (AUC) values. The flood risk maps results showed that 12.62, 16.30 and 24.64% of urban and rural regions will be exposed to flood risk for 25, 50, and 100-year return periods. The results of this study pointed out that the GI method can be used as an alternative to hydraulic and hydrological modeling for flood modeling due to its proper accuracy and low requirement for much hydraulic and hydrological data.

In this present, two pairs of cable models were designed and tested to reproduce the induced vibration of stay cables in a wind tunnel. Cable of cable-stat stayed bridges are flexible structural members that have very low natural frequency and low intrinsic attenuation, Therefore, they are able to various vibrations such as wind vibration, wind-rain-induced vibration (RWIV), and earthquakes. Wind-rain-induced vibration has become one of the major concerns of bridge engineering. One of the ways to reduce the effects of wind and rain on cable bridges has been examined is cable aerodynamic specification and also one of the factors affecting the aerodynamics of the cable is the formation of rainwater flow on the surface of the cable. Therefore, spiral grooves were installed on the surface of the cable to direct this flow of water to the bottom of the cable. By testing two cable models (without grooves and with grooves) in the wind tunnel with artificial rain flow, the effect of different wind speeds, and also different yaw angles, it was concluded that by creating spiral grooves to The cable circumference can reduce the induced vibration caused by wind and rain, and the presence of these spiral grooves around the cable eliminates low-frequency currents and thus reduces the amplitude of the induced vibration.

Failure to define the indicators and sub-indicators for measuring the performance of Repair and Maintenance (R&M) activities is one of the significant issues in a building to increase its life expectancy. Evaluation of R&M system in a building is one of the key factors in improving the quality of R&M performance steps. Therefore, to implement appropriate strategies, the criteria affecting on R&M system must be identified. Also, choosing the proper net policy is a strategic decision-making problem that effectively reduces the cost and longevity of buildings. In this research, by using the experts’ opinion and the Delphi method, the indicators and sub-indicators affecting the R&M system were identified, and those indicators were graded using the decision tool. The existing buildings in Karaj city as a case study were then considered to evaluate the proposed system. Analysis of the results shows that the safety index has the highest grade according to the experts’ opinion, but by reviewing the results of the case study, this rank was assigned to the health criterion. Then, by using the SWARA technique, the most critical policies affecting buildings’ R&M are identified among Emergency Maintenance (EM), Breakdown Maintenance, Corrective Maintenance (CM), Preventive Maintenance (PM), Predictive Maintenance (PdM), Total Productive Maintenance (TPM), Proactive maintenance. Applying the VIKOR method and the results of both approaches revealed that Corrective Maintenance (CM) and Breakdown Maintenance (BM) policies are the best for buildings, R&M policies.

The present paper aims to determine the undrained bearing capacity of strip footings located on two-layered clayey soil in the vicinity of a geogrid-reinforced slope under the effect of combined loading by applying horizontal (H), vertical (V), and bending moment (M) loads. To this aim, by finite element modeling in ABAQUS based on the controlled load-displacement method, the failure envelopes and the failure mechanism of the subsoil of strip footings under the effect of combined loadings were determined in V-H, V-M, and V-H-M loading spaces. The results obtained in two cases of unreinforced and reinforced slopes with geogrids were compared by performing parametric studies regarding the effect of changes in undrained shear strength ratios of clayey layers (Cu1/Cu2) and the ratio of the thickness of the first clay layer to the width of the strip foundation (H1/B). The results showed that by increasing Cu1/Cu2 in V-H loading spaces, the vertical bearing capacity increased, which is caused by the increase in the undrained cohesion of the first layer. Furthermore, in scenarios involving both vertical-horizontal (V-H) and vertical-moment (V-M) load combinations, when subjected solely to vertical loading, a greater volume of soil experienced failure. The results showed that reinforcing the slope with geogrid increases the vertical and the moment bearing capacity by 31 and 35%, respectively. In general, the findings of this study provide new insight into the failure mechanism of strip foundations based on two-layered clayey soils in the vicinity of geogrid-reinforced slopes under the effect of combined loads.

One of the important reasons that causes cracking and deformation in concrete elements, especially in the surface area of concrete, is different climatic conditions and temperature changes. In the previous researches, not many researches have been done regarding the relationship between the penetration rate value and the surface strength. The reason for the lack of research in this regard is the lack of simple methods or the high price of equipment to evaluate surface strength. In this article, infiltration- reducing materials with the brand names of Supergel and Mesocrete are used, which are widely used in Iran today. A simple "twist-off" test has been used to evaluate the surface strength. Also, "cylindrical chamber" test was used to measure the permeability. To apply the cycles of temperature changes, the samples were subjected to cycles of 50, 100, and 150 cycles. The obtained results show in the 150th cycle, the surface resistance of ordinary concrete has decreased by about 30%, but the reduction of the surface strength of concrete with penetration-reducing materials is less than 20%. Also, the increase in the permeability of ordinary concrete in the 150th cycle is equal to 486%, but this value is half of this value in concretes containing permeation-reducing substances. In the following, by using MATLAB software, it was determined that the relationship between permeability and concrete strength is close to each other, and this issue is established in terms of formulation with a first-order plane equation with a correlation coefficient of about 91%.

The behavior of soil-pile systems subjected to earthquake loading depends on many parameters. These parameters can be categorized into three main groups: geometrical parameters of the pile, soil mechanical properties, and loading characteristics. The purpose of this study is to investigate the effect of pile geometrical parameters on the seismic response of soil-pile systems considering soil nonlinear behavior. To this aim, a set of fully nonlinear three-dimensional analyses in the time domain was conducted using the finite difference computer program FLAC3D. The focus of the paper is on the seismic response of the floating single pile embedded in clayey soil and the parametric study was performed to investigate the effect of pile geometrical parameters on its seismic response. To consider soil nonlinear behavior during seismic events, an elastoplastic constitutive law was applied to the soil medium. Also, soil shear modulus reduction with the increase in soil shear strain level was simulated. The results of this study showed that an increase in pile diameter causes an increase in the maximum kinematic bending moment. This increase is proportional to the pile diameter powered by a value. Also, the results showed that effect of pile length on the magnitude of maximum bending moment in pile was not significant. However, the shape of the bending moment distribution diagram and location of the maximum bending moment are strongly affected by pile length.

Financing the mining projects is one of the issues against investors at different stages of the project. There are several options for financing mining projects and each of them has its properties. The rate of using these choices depends on the plan’s circumstance and investors’ Preferences. In the present study, after identifying the criteria affecting the NPV of mining companies, with the help of a questionnaire and using the Delphi technique, five criteria of refund mechanism, the volume of capital, interest rates, access costs, and risks, were selected as the main criteria for studying different financing alternatives (including stock exchange, sukuk, banks and financial and credit institutions, internal capital, and foreign bank). Since these criteria are not independent and the dependency between them affects the choice of financing method and as a result the goal of this research, the method of Analytical Network Process (ANP) was used and the relative weight of each criterion is obtained. In the next step, according to the mentioned criteria and determining the impact of each on the NPV of mining companies, the alternatives should be prioritized in such a way as to achieve the highest NPV. The findings of the research show that foreign banks with a final relative weight of 0.398 is the best option. After that, the use of internal capital with a relative weight of 0.217, sukuk with a final relative weight of 0.161, the stock exchange with a final relative weight of 0.138, and finally, internal banks with a final weight of 0.086 are the most appropriate methods, respectively.

In the event of progressive seismic collapse, the entire columns are not removed and can weaken in a time-dependent manner. For example, the possibility of reducing the carrying capacity of a column is higher in the maximum acceleration of the ground. Therefore, since earthquakes have different parameters such as frequency content, maximum acceleration, effective vibration duration, and other things, they can subject a structure to different effects. This is the special distinction of this phenomenon in contrast to progressive failure under gravity loads, which multiplies its importance. In this article, the ductility of simple and bending frames with special divergent bracing against progressive collapse is evaluated from a seismic point of view. The analysis used is non-linear time history analysis, according to 14 acceleration maps of the near-pulse area of FEMA P695, and non-linear static analysis, which was performed in SAP2000 software. The results showed that the maximum demand for the floor drift angle and rotation of the floor connecting beam in the two scenarios of removing the first and fourth floors for the special bending frame with special eccentrically bracing is 50% of the values of the simple frame with special eccentrically bracing. Except for the bending beam, in the scenario of removing the fourth floor, the maximum values of the floor drift angle for both frames were 0.024 radians, and for the maximum rotation of the floor beam, 0.056 and 0.061 radians, respectively.