Journal of Civil Engineering Researchers
Volume:5 Issue: 2, Spring 2023

in recent decades, Geopolymer concrete (GPC) is a new material in the construction industry, which has favorable performance and workability and contains aluminosilicate materials full of silicate (Si), aluminum (Al), and alkaline solution as a binder. The advantages of using geopolymer materials instead of cement in concrete are not limited to high mechanical and microstructural properties. It also has a remarkable effect in reducing greenhouse gas emissions. In the current study, Granulated Blast Furnace Slag (GBFS) GPC was used with 0-2% polyolefin fibers (POFs) and 0-8% nano-silica (NS) to improve its structure. After curing the specimens under dry conditions at a temperature of 60 °C in an oven, they were subjected to compressive strength, tensile strength, elastic modulus, ultrasonic pulse velocity (UPV) and impact resistance tests to evaluate their mechanical properties. The addition of NS enhanced the whole properties of the GBFS geopolymer concrete. The compressive strength, tensile strength, and elastic modulus of the concrete increased by up to 22%, 14%, and 24%, respectively. Besides, it leads to ultrasonic wave velocity enhancement to 12% in the room temperature. The addition of the fibers to the GPC significantly increased the tensile strength (by up to 9%) and the energy absorbed due to the impact. Moreover, compared to Concrete containing ordinary portland cement (OPC), the GPC demonstrated much better mechanical and microstructural properties. Besides, the presence of POFs in the GPC compound substantially affects tensile strength and resistance against an impact. Accordingly, the sample’s tensile strength had an improvement by 8.4% in the room temperature. In the following, by conducting the X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), and Scanning electron microscope (SEM) tests, a microstructure investigation was carried out on the concrete samples. In addition to their overlapping with each other, the results indicate the GPC superiority over the regular concrete. © 2017 Journals-Researchers. All rights reserved.

Coarse-grained materials, such as sand and gravel, exhibit a significant dependence on particle failure rate, which greatly influences their engineering behavior. This research focuses on the three-dimensional modeling of grain material behavior using the discrete element method (DEM) with PFC3D software and FISH programming language. The specific objective is to model the particle breakage phenomenon and its impact on resistance behavior and deformation. To accurately represent the non-spherical shape of the particles, an interconnected sphere approach was employed. The modeling of grain failure was achieved by establishing a failure criterion that considers two critical conditions: the heterogeneity of contact forces and stress within the particle. The proposed model and criteria were validated through comparison with triaxial experimental results obtained from the Purulia dam gravel. The results demonstrate that the developed model successfully captures the essential aspects of particle failure and its influence on the behavior of the granular environment. The simulations accurately represent the resistance behavior and deformation characteristics observed in the triaxial experiments. This validates the effectiveness of the proposed model in simulating the significant effects of particle failure on the behavior of coarse-grained materials. The findings of this study contribute to a deeper understanding of the complex behavior of coarse-grained materials, particularly in terms of their response to particle failure. The developed DEM model, incorporating the particle breakage phenomenon, provides a valuable tool for accurately predicting and analyzing the behavior of granular materials in various engineering applications. © 2017 Journals-Researchers. All rights reserved.

Cities became one of the main centers for conducting research due to the fact that they are the main places where people gather. One of the problems that plague the city today, especially the big cities, is the phenomenon of the city's heat island. Many things play a role in the spatial changes of the heat island, among them are human activities and changes in the earth's surface cover, which often lead to the reduction of green space. Several vegetation indices have been developed, and in this research, NDVI and EVI indices were investigated. Earth's surface temperature for Mordad 27, 1400 was retrieved from Landsat images using a single-channel algorithm and the mentioned indices were extracted for the above date. The results showed that most of the city surface was covered by a temperature layer of 305-310 degrees Kelvin. By comparing the indices and the temperature of the earth's surface, it was found that the temperature of the earth's surface and vegetation have an opposite relationship so that in the south and east the temperature is lower and the vegetation is more; But this issue is the opposite for the south and west. Also, the relationship between the surface temperature of the earth and the EVI index was equal to -31.23%, and its relationship with the NDVI index was about -24%; This shows that these two indicators are similar with a slight difference. © 2017 Journals-Researchers. All rights reserved.

In recent years, many advances have been made in fatigue and failure modeling in steel structures. The methods used to simulate failure and fatigue caused by earthquakes in steel structures are based on experimental and semi-empirical methods or conventional fracture mechanics. Semi-empirical methods cannot be generalized to a wide range of structural details, but conventional fracture mechanics can be reliably used only to simulate brittle fractures such as those observed in the Northridge and Kobe earthquakes, where large-scale yielding is absent. Similar to what is described in this paper, physics-based micromodels seek to simulate the fundamental processes of void growth and coalescence and granular shear responsible for very low-cycle fracture and fatigue in structures. These models are relatively free of assumptions about behavior and can be accurately used to simulate fracture and fatigue in a general sense under different conditions. The growth of voids or cracks can cause sudden crack propagation and deterioration of strength on a global scale of structural components. Therefore, these micromodels, relying on fundamental physics, are equally applicable to situations considered as "brittle" or "unbreakable" at the structural or component level. Examples are given to demonstrate the use of one of these models - the Cyclic Void Growth Model (CVGM) - to simulate failure through continuous finite element analyses. © 2017 Journals-Researchers. All rights reserved.

Aftershocks can always cause the collapse of structures damaged by the main earthquake. In this article, the seismic performance of an 8-story steel bending frame designed in c-type soil was first subjected to the seismic sequence of an earthquake and an aftershock, and then the same building with the addition of a fluid viscous damper (Fluid Viscous Damper) was evaluated. The results showed that the seismic performance of the studied frame under the effect of severe aftershocks with the presence of a liquid viscous damper is very different from the case without FVD. For example, the maximum displacement of the structural floors was reduced by 60% compared to the case without a damper. It was also found that while most of the aftershocks in buildings without dampers cause a significant increase in the permanent displacement of the roof, in the presence of dampers, this amount has decreased significantly, although in general, the damage caused by the effect of aftershocks on the building is much more as it will be from a state in which the structure is only subjected to the main earthquake © 2017 Journals-Researchers. All rights reserved.

The particle penetration removal efficiency of the High Efficiency Particulate Air (HEPA) and Ultra Low Particulate Air (ULPA) filters were studied by using of mono-disperse liquid aerosols of Di-Octyl Phethalate (DOP) under vary operational conditions. The effects of different operational factors, including the particle size, the face velocity and pressure drop were investigated in this study. The results indicated that the most penetrating particle size through the ULPA and HEPA filters was approximately 0.1-0.12 μm. Brown diffusion effect is suggested mechanism for particle size removal mechanism of 0.1 μm and less while impaction and interception mechanisms are explained the behavior of HEPA and ULPA filters for removal of 0.12 μm and more particle size. The penetrations of particle through both kind of filters were increased with increasing of face velocity. Additionally, the pressure drop of filter is increased versus the rising of face velocity. The cost of energy is lower in low face velocity of filters. © 2017 Journals-Researchers. All rights reserved.