نشریه مهندسی عمران امیرکبیر
سال پنجاه و ششم شماره 8 (آبان 1403)

Considering the indicators of sustainable development in the calculation of cutoff grade leads to the sustainable mine design and is the biggest opportunity to reduce the adverse effects of mining activities. Until recently, only economic indicators were considered in the calculation of the cutoff grade. In recent studies, environmental indicators have also been implicated, but research that considers social factors has not been reported. Therefore, in the present study, a new model developed to calculate the cutoff grade, which includes all three criteria of sustainable development. To carry out the study, the costs related to sustainable development were entered into the break-even cutoff grade formula and the proposed model was validated with the information related to Choghart Iron Ore Mine. The results show that the sustained development costs included in the estimation of the Choghart Mine account for only 5% of the total costs, and the results of the sensitivity analysis show that these costs have the least impact on the determination of cutoff grade. The findings also show that the impact of sustainable development costs in Choghart Mine has increased the percentage of the cutoff grade by 5.5% and may not have much effect on the results. Therefore, the outcomes indicate that by using this method, a big change has not been achieved in the percentage of the cutoff grade. Also, some of the environmental and social problems of the project, taking into account the sustainable development costs, and spending the lowest percentage of the cost will be decreased.

According to the experiences gained from past earthquakes, the need for a structure that has less damage and can be easily repaired after an earthquake is essential. One of the methods of depreciating seismic energy and having a repairable structure is to use the rocking brace system. In this study, the effect of using swing brace along with liquid viscous damper in improving the seismic fragility of structures has been investigated. The swing brace is formed by adding a liquid viscous damper. The set of this system has been installed at the base of the structure. For numerical studies, a three-story shear structural model with nonlinear behavior is considered. The examined structures in an uncontrolled state and equipped with a brace-swing-damper system have been subjected to the vibration of 60 earthquake records recommended in the seismic regulations with different specifications and frequency content. The results of dynamic analyzes are subjected to regression analysis to obtain the relationship between the intensity of earthquake excitation and the response of the structure and to estimate the seismic demand of the structure. Finally, the fragility curves for mild, mild, extensive, and complete performance levels for three performance criteria including drift ratio of structural members, drift ratio of non-structural members sensitive to drift and acceleration of non-structural members sensitive to acceleration have been determined and compared. The results indicate the effective performance of the brace-swing-damper system in improving the seismic fragility of the studied structures, so that the fragility has decreased by 35%.

Despite the expansion of public-private partnership in the world, the amount of private sector investment in Iran's infrastructure projects is lowe. In this article, the success factors of public-private partnership, specific to Iran's business environment, have been identified and their priority has been analyzed from the point of view of different stakeholders. By nominal group method, 23 success criteria of Iran's public-private partnership were identified and practical solutions to overcome them were proposed. The results of this research show that the most important success factors of public-private partnership in Iran include the project's profit rate, the employer's experience in project management, how to share risks between the two parties to the contract, and the transparency of the tender. The analysis of the results of the evaluations carried out by the private sector and the public sector in this article shows that there is a big difference between the priorities of the two parties. From the point of view of private sector, the main obstacle to public private participation in Iran is the adherence of executive bodies to contractual obligations. From the point of view of the public sector, the main priority against the development of public-private partnership is ambiguity in the laws and powers of public sector decision-makers. Therefore, it is suggested that by passing special laws for public-private partnership, while providing legal incentives and exemptions for financial support of private investors, efforts should be made to increase transparency in the decision-making process of the public sector.

Reducing the severity of plastic shrinkage cracking in concrete pavements by using new materials and comparing with traditional methods by using new analysis methods can increase the durability and improve the performance of concrete pavements. The current research examines the comparative effect of macro polypropylene fibers and reinforcement bars in controlling and reducing plastic shrinkage cracking in concrete pavements. The severity of cracking in the reference concrete mixture, steel bars mesh at intervals of 100 x 100 mm and macro polypropylene fibers in the amount of 1.8 Kg/m3 was evaluated according to the ASTM C1579 standard method. The results indicated that both reinforcement bars and fibers significantly reduce the cracking area up to 40% in concrete containing reinforcement and 68% in fiber-reinforced concrete. The length of the crack changes more than the average width of the crack The cracking behavior of concrete containing steel bars mesh is similar to the cracking behavior of fiber concrete, as a result, macro polypropylene fibers may be considered as a suitable substitute for steel bars mesh. It was also seen that the effect of fibers in reducing cracking is greater than the effect of steel bar mesh.

In Direct Displacement-Based Design (DDBD), the performance objective is to achieve the design displacement (target displacement) and the stiffness and strength of the structure is determined in such a way that the maximum displacement of the structure in an earthquake reaches this displacement. For this purpose, the design base shear is determined based on 3 key parameters of equivalent damping, damping modification factor and P-Delta effect. Due to the variation of relationships for each of these parameters, in this study the influence of using different relations on achieving performance objectives is investigated. In this study, 8 bridge piers with 2 different heights, 2 different span lengths and 2 seismic hazard levels were selected. Then, each of these piers was designed for 27 different design paths resulting from 3 distinct relationships for each of the 3 key parameters and a total of 216 bridge piers were designed by DDBD approach. Then, to evaluate the seismic performance of the piers, each of the 216 piers was modeled in OpenSees software and subjected to 14 earthquake records scaled on the design spectrum. After determining the maximum displacement of each pier, the proximity of this displacement to the target displacement was studied as a performance objective indicator. The results of analysis show that the use of different design relations has a significant effect on the maximum displacement of piers and their performance in earthquakes. Finally, comparing the results for 27 selected design paths, the best combination of relations for direct displacement-based design was proposed.

The theory of planned behavior has been used in various studies to understand human behavior in various traffic studies, including the understanding of the risky behavior of drivers. Considering the importance of violation in the occurrence of accidents, we tried to measure the contribution of each human factor in its occurrence and analyze the existing relationships between them according to the theory of planned behavior. According to the use of this theory, a large number of independent and dependent parameters were found in the research, and structural equation modeling was used to analyze and investigate the relationships between them. Also, exploratory and confirmatory factor analysis was used for statistical analysis of data. A strong relationship was found between the driver's Intention toward violations and the frequency of accidents. The structures examined in this theory, which included attitude and subjective norms and perceived behavioral control, directly affected the driver's Intention a violation. The greatest impact belonged to the variable of the first scenario, which included a special category of indicators. These indicators included the indicators used in the discussion of perceived behavioral control and subjective norms in the descriptive norms section, which were used simultaneously in an item titled the first scenario. In the positions after that, the attitude and second scenario were placed. The second scenario included a group of indicators that examined subjective norms in the brief norms section. Also, a significant relationship was found between the two variables of slip and error with the frequency of accidents.