Journal of Civil Engineering Researchers
Volume:4 Issue: 4, Autumn 2022

Today, the use of processed mineral materials in concrete to improve mechanical properties and durability has opened a wide field of vision for researchers in the structural sciences. On the other hand, preserving the environment by reducing the toxic gas of carbon dioxide caused by cement production is one of the concerns of scientists. In this regard, minerals containing abundant aluminosilicate particles and active alkali solution (AAS) replaced ordinary cement in concrete and led to the production of geopolymer concrete (GPC). The composition and reactivity of these materials produce a strong adhesive material that in combination with other concrete components, causes the final strength of GPC. High temperatures weaken the concrete against loads by damaging the structure of hydrated gels in concrete. GPC has better fire resistance than OPCC due to its density in its microstructure.In the current study, GranulatedBlast Furnace Slag(GBFS)-based 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, Modulus ofelasticityand Weight Loss tests to evaluate their mechanical properties. all tests were performed at 90 days of age under ambient temperature (20 °C) and high temperature (500 °C). The addition of NS enhanced the whole properties of the GBFS-based GPC.Addition of up to 8% NS to the GPC composition at 20% temperature improved the modulus of elasticity test results by 13.42% and the compressive strength up to 21.94% by 11.58%. Addition of up to 2% of POFs to the GPC composition resulted in an improvement, modulus of elasticity of 07.05% and a decrease in compressive strength of up to 22.49%. Apply the lowest (0.061%) and highest (0.12%) weight loss percentage of concrete samples under 500% heat, belonging to scheme 4 (including GPC containing 8% NS) and scheme 6 (including GPC containing 2% POFs) Came.In the following, by conducting the Slag, Scanning Electron Microscope (SEM) analysis, a microstructureinvestigation 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. Besides, it demonstrated the positive influence of NS addition on the concert microstructure.

One effective way to reduce dead and earthquake loads isto use waffleslabs.The use of waffleslabsleads to smaller sections.There are various methods for predicting the behavior of slabs, the most important of which is fracturemechanics.Considering the varietyof geometry of waffleslabs, it is important to investigate the formation and growth of cracks in them.The current research aimsto analyze the post-crack behavior of waffleslabs under common loading conditions using the finite element method by using numerical modeling to analyze cracks in reinforced concrete members.by comparing the obtained results with the laboratory sample, the optimal numerical model for predicting the behavior of the hollow slab was determined.The waffleslab sample was modeled with two types of distributedand concentrated loading conditions and two types of simple and fixedsupport conditions.The models weremodeled by two methods of concrete damage plasticityand smeared cracked concreteby Abaqus software. Various parameters of these samples, including the load-displacement diagram, the load coincident with the formation of cracks, the displacement in the middle of the slab opening, and the pattern of the formation and propagationof cracks, etc., were discussed and investigated.To validate and control the modeling process, the laboratory results of the research of NithyambigaiG et al. in 2021 have been used.The outcomes of thisstudy showed; a relatively good correspondence between the two methods of Concrete damage plasticity and the concretesmeared crack model, but due to the definition of failure in the Concrete damage plasticity method, more accurate results can be obtained.

In this research, recycled concrete aggregates were used instead of natural aggregates in concrete, and then the recycled concrete was reinforced with polypropylene fibers.The purpose of this study is to first investigate the effect of replacing recycled aggregates with natural aggregates on the mechanical resistance of concrete and then to investigate the effect of adding polypropylene and micro silica fibers on concrete containing natural and recycled aggregates in two water-to-cement ratios of 0.4 and 0.55. The results of this research show that by replacing recycled aggregates with natural aggregates, the compressive and tensile strengths of concrete have decreased significantly. Also, the results show that the addition of polypropylene fibers with a weight ratio of 1.5% had a significant effect in compensating the reduction of compressive and tensile strengths in recycled concrete. It should be mentioned that the samples containing microsilica and polypropylene fibers in all mixing designs (natural and recycled aggregates) had higher resistance values (tension and pressure) than the samples without microsilica.Also, concrete samples with a water-cement ratio of 0.4 had higher compressive strengths than concrete samples with a water-cement ratio of 0.55.

In general, crisis management means purposefully pushing the progress of affairs to a controllable routine and expecting things to return to the pre-crisis conditions as soon as possible. In short, crisis management is all actions related to prevention and risk management, organization and management of resources needed in response to crisis. Crisis management is an applied science that, through systematic observation of crises and their analysis, seeks to find tools that can be used to prevent the occurrence of crises or, in case of occurrence, in terms of reducing the effects of the crisis, necessary preparation and rapid relief. and took action to improve the situation. The main purpose of this research is modern crisis management in the probability of an earthquake 

in recent years, studies have been started for the use of light-grained concrete in conventional reinforced concrete structures, it is expected that the use of light-grained concrete without having a negative effect on the use of the structure will reduce the costs in construction and reduce the structural mass. As a result, the earthquake load will be reduced. In this research, concrete with an approximate compressive strength of 18.24 megapascals and an approximate specific weight of 1800 kg/m3 was obtained by using Lika grain style. In order to evaluate the structural behavior of lightweight concrete, 5 concrete columns were built in the laboratory and were subjected to axial load and the results related to these columns were presented, and then a suitable model for these columns was presented by Abaqus finite element software and analytical studies It was done on the relevant results,which are in good agreement with the laboratory results. The agreement of the results obtained from the modeling with the laboratory results is a proof of the accuracy of the built model.

Steel shear walls have always been used in the construction and improvement of many structures due to their advantages such as high strength and stiffness, ductility and excellent energy absorption. In the meantime, corrugated steel shear walls have been proposed due to postponing the elastic buckling of the plate and increasing ductility and energy absorption. Corrugated steel shear walls can be used in both single and double layers. Due to the fact that so far, limited research has been conducted about double corrugated steel shear walls, therefore, in this research, the hysteresis behavior of double and single layer corrugated steel shear walls has been analyzed parametrically using the finite element method and using ABAQUSsoftware. Thus, after validating a experimental sample, a two-layer corrugated steel shear wall with one bay-one story with conventional angles of 30, 45 and 60 degrees was investigated in ABAQUSsoftware under cyclic loading. The results of this research showed that the hysteresis curve of double and single layer corrugated steel shear walls is stable. Also, the resistance and energy absorption of double corrugated steel shear walls is higher than single layer corrugated wall. Also, the resistance of corrugated steel shear walls with single anddouble layers is lower than that of flat steel shear walls. Also, increasing the corrugation angle of the plate has led to an increase in resistance and energy absorption. In addition, behavior factor and ductility of flat steel shear walls are higher than single-layer and double corrugated walls. Nevertheless, the over-strength factor of the studied samples is almost equal to each other.