Journal of Civil Engineering and Materials Application
Volume:4 Issue: 4, Autumn 2020

Vital infrastructures have, nowadays, a high level of importance in urban areas. Any disruption in one of the infrastructures can cause severe impacts on inhabitants and consequently can affect the other infrastructure systems. In this regard, the electricity grid is considered to be one of the most critical infrastructures, and it has been performed vulnerable to natural hazards, specifically in past earthquakes. Iran is located in a high seismic activity region. Therefore, in this study, the seismic vulnerability of the power distribution network in Arak city has been comprehensively investigated. The power grid has three sections consisting: the electricity generation, transmission, and distribution. In this study, a seismic risk analysis was carried out on its distribution section. The obtained results show that the seismic hazard in the north-eastern part of Arak city is at the lowest level, and in the south-west region, it is at the highest level. Then, the potential damage to the network and the possible financial losses have been calculated. It was revealed that the 315 KVA transformer substations, 615 KVA transformer substations, and finally transmission lines, are at the highest seismic risk of financial damage. According to the obtained results, the probable financial losses for a return period of 475 years event for the 315 KVA transformer substations, the 615 KVA transformer substations, the transmission lines with 120 mm and 70 mm aluminum wires are, respectively, 22300000, 5717000, 270000, and 700000 U.S. dollars.

In this study, the role of eggshell powder and its effect on concrete's mechanical properties and to achieve the optimum percentage of eggshell utilization for higher strength and durability were investigated. The eggshell was grounded and heated to 950ᵒC for 2 hours, and by XRD test, the chemical analyses were carried out and compared with Portland cement. Experimental tests including water absorption percentage, the specific gravity of concrete, electrical resistance test (indicating corrosion and permeability), flexural strength, and compression strength were performed on samples with 0, 10, and 20 wt% cement replacement eggshell. The tests were carried out at 3, 7, and 28 day age on 15 cm cube specimens. Flexural tests were carried out on prisms 100x100x500mm. The results of tests on concrete showed that replacement of 10% eggshell causes 12% slump reduction, 1% increase in compressive strength, 21% decrease in water absorption, 2% increase in concrete, specific weight, and 90% increase the electrical resistance in comparison with 0% eggshell (control specimen). 20% ​​cement replacement eggshell causes 24% decrease in a slump, a 17% decrease in compressive strength, and 4% enhanced in water absorption, a 1% increase in specific gravity, and a 90% increase in electrical resistance in comparison with control specimen. Corrosion in the control specimen is fairly certain, while with 10% and 20% eggshell in both mixes, corrosion is less possible. The results of the compression test are compared to other research work in order to present the different %eggshell on concrete strength. The results of this study suggest that the use of eggshell substitutes an appropriate proportion replaced cement gives a suitable quality and also causes a safer environment.

Seismic analysis of earth and rockfill dams is generally done in two ways: quasi-static and dynamic. However, a quasi-static method with easy application and simple assumptions may lead to unsafe and uneconomical results. In the present study, two static and dynamic analyzes have been used nonlinearly using the Rayleigh Damping rule to calculate the settlement and horizontal displacement of Azadi Dam in the stages of the end of construction and steady-state seepage. Also, in numerical analysis, Abaqus software and a simple elastoplastic behavior model based on the Mohr-Coulomb criterion have been used. The seismic analysis results show that settlement is more sensitive to horizontal displacement, so that settlement at the upper, middle, and lower levels of the shell is 66%, 55%, and 52% more than horizontal displacement, respectively. The highest amount of settlement occurred in both quasi-static and dynamic states in the dam's upper levels, with the difference that in the dynamic state and the full reservoir, the upstream shell is more affected by settlement. Also, settlement in the dynamic analysis is 37% higher than the quasi-static analysis.

The daily-incremental population of Iran and the incremental need for housing as well as the insufficient traditional construction systems of Iran have increased the tendency to use modern technologies in mass housing projects. It is tried in this research to study the effects of using modern construction technologies on time, cost, and quality of Iran mass housing projects, their problems, and ways to develop. The results of this research show that these technologies in Iran will accelerate project time up to 50% than the traditional technics. Moreover, construction costs reduced to 30% in projects with fewer housing units than the traditional technics, and costs reduced in projects with many units in total per capita. The maximum use of this technology in Iran is in the step of structure-basis and facility installation. In recent years, the entrepreneurs’ tendency has increased toward modern technologies. Based on findings, providing the appraisal motives from some institutions such as municipality will increase public interest to use these technologies in the state. Based on decision-making matrix of multi-criteria decision-making method, the maximum effect of modern technologies on Iran mass-housing projects have higher integrity and solidity of structure, better quality, longer life-time of structure, acceleration in construction time, better resistance against earthquake, lower target costs in mass scale, beauty and lower harmful effects on environment, better efficiency of installation, and optimization of building energy consumption.

In this research, the effect of adding different percentages of nano-silica and rubber powder on the compressive strength of the geopolymeric concrete specimens is investigated. The set of performed tests includes the compressive and tensile strength tests of the geopolymeric concretes. Due to the high rate of consumed concrete and the daily increase of the need for cement production, it is essential to consider environmental defects of this material and present new replacement products to move towards sustainable development. Low shrinkage, high compressive, and tensile strengths are among the main properties of produced concrete. Also application of nanoparticles, due to their specific physical and chemical properties, in many respects are very good candidates for producing novel materials with unique capabilities. Hence, the use of nano-silica as one of the nano technology products which could play the role of a very active artificial pozzolan in concrete has been under the focus of attention. Replacement of the rubber powder in the construction industry, due to the irresolvability of this type of wastes and also its specific structure such as improved ductility, reduced density, and improved resistance against concrete cracking has been practiced today. The aim of this research is to implement the two mentioned materials as additives in the concrete mix design and investigating their effect on the increase of the compressive and tensile strengths in concrete. The results of this research have shown that the use of nano-silica powder and rubber powder results in an increase of the compressive strength of concrete up to  1.45 times that of the control specimen using the nano-silica powder and 1.35 times that of the control specimen using the rubber powder.