Early age corrosion of mild steel in aggressive media

Effect of exposure time, section type and solution concentration on mild steel early age corrosion was studied. Steel specimens section types were box, tube and corner. They were subjected to 3.5%; 5.0% and 7.0% NaCl solutions. It was established that solution concentration effects the corrosion until reaching the saturation value.Вивчено вплив тривалості експозиції, типу сталевого профілю та концентрації розчину на ранню стадію корозії вуглецевої сталі. Використано сталеві зразки у вигляді куба, трубки та кутника. Досліджували в 3,5-, 5,0- та 7,0%-их розчинах NaCl. Встановлено, що після досягнення граничної концентрації розчину хлориду натрію подальше збільшення вмісту солі не впливає на корозію сталі.Изучено влияние продолжительности экспозиции, типа стального профиля и концентрации раствора на раннюю стадию коррозии углеродистой стали. Использованы стальные образцы в виде куба, трубки и угольника. Исследовали в 3,5-, 5,0- и 7,0%-ых растворах NaCl. Установлено, что после достижения предельной концентрации раствора хлорида натрия, последующее увеличение содержания соли не влияет на коррозию стали

Non-linear analysis of reinforced concrete slabs under impact effect

Most of the existing structures are designed to resist static loads only. Various researchers indicate that sudden loads affecting structural members should also be considered in the design phase. Surfaces of many structures are covered with concrete slab members that are under the effect of sudden loads such as accidental drops, rock falls, or military attacks. A non-linear analysis of RC slabs is performed in this study using the Abaqus software. Impact parameters such as accelerations, velocities, displacements, impact forces, and energy capacities, are determined for each slab

Experimental and numerical investigation of timber formwork beam under different loading type

With the developing construction technologies, the formwork systems used in the manufacturing of the structures have also changed and developed significantly. Especially in the production of high-rise buildings, a special sliding formwork system that is quick-installation, resistant to external loads, can be used more than once, are widely used and preferred. Timber and composite timber materials are preferred due to their durability, ease of installation, lightness compared to steel systems, and easy to use more than one time. Within the scope of this study, it was aimed to investigate the performance and behaviors of timber beams of 1800 and 2450 mm length experimentally under the influence of different loading types in H20 top P-type, which is among the products of DOKA Company. During the use of timber formwork beams, various loading types such as static, fatigue, and sudden dynamic impact load can be affected. For this reason, an experimental study was carried out, and general load-displacement behaviors, initial stiffness, displacement ductility ratios, energy dissipation capacities, collapse mechanisms, acceleration, displacement, and impact load-time behaviors under the effect of monotonic static, repetitive fatigue and impact loading of two different length timber formwork specimens were examined. In addition to experimental study, nonlinear numerical analysis is made by using ABAQUS software for experimental specimens and compared with results with an experimental study. Communicated by Prof. Dr. Corina Sandu. © 2020, © 2020 Taylor & Francis Group, LLC

Performance of engineered cementitious composites under drop-weight impact: Effect of different mixture parameters

Current research focuses on the experimental and numerical determination of impact performance of engineered cementitious composites (ECC). Performance assessment of ECC beams with different mixture parameters was made. Mixtures were produced with different replacement rates of Class-F fly ash and slag with Portland cement, water to binder ratios and fiber types (polyvinyl alcohol [PVA] and nylon [N]). Experimental works were validated with incremental dynamic analyses performed by ABAQUS finite element software. Impact testing results were further supported by mechanical property results. Results reveal that each individual mixture parameter used is distinctively effective in modifying the properties under both sudden impact and slow static loading. In brief, enhanced impact resistance is noted when ECC is produced with slag, low amounts of pozzolanic materials, low W/B ratio, fiber addition and PVA fibers. Experimental results were also in line with the numerical results from ABAQUS largely. Significantly, cost-effective N fibers were also shown to be fully replaceable with costly PVA fibers without jeopardizing mechanical/impact performance, if mixture design parameters are adjusted suitably. Current research is likely to attract further research on the development of ECC that is with lower cost and comparable impact/mechanical performance with regards to widely studied more expensive counterparts in the literature. © 2019 fib. International Federation for Structural Concret

Low-velocity impact behaviour of two way RC slab strengthening with CFRP strips

There are a lot of studies focused on behaviour of reinforced concrete (RC) slabs under static and dynamic loadings in the literature. However, investigations related to Carbon Fibre Reinforced Polymer (CFRP) strengthened RC slabs subjected to impact load are still relatively rare. Consequently, an experimental study was performed in order to determine impact behaviour of two way simply supported RC slabs strengthened with CFRP strips. The arrangement and width of CFRP strips were varied in an experimental study. The impact load was applied to slabs using moveable drop-weight test machine designed by the authors. A total of nine RC slabs that were 1000 × 1000 × 80 mm dimensions were manufactured. RC slabs were strengthened using CFRP strips with a width of 50 and 100 mm as orthogonally and diagonally in both one and two directions. One of the specimens was un-strengthened and manufactured as reference specimens. The time-history of the impact force, the accelerations of two points, the center displacement of slabs and the strains of four points on CFRP strips were measured. The crack patterns of slabs are also observed. In the light of experimental results, the effects of applied strengthening method on low-velocity impact behaviour of RC slabs were determined and interpreted. Besides, the finite element models of RC slabs strengthened with CFRP strips are generated using ABAQUS software. It is found out that the proposed finite element model could be used for evaluation of dynamic responses of RC slabs strengthened with CFRP strips subjected to low-velocity impact load. © 2018 Elsevier Lt

Experimental Investigation of Impact Behaviour of RC Slab with Different Reinforcement Ratios

Reinforced concrete (RC) slabs may be exposed to the low-velocity impact load during their service periods. In low-velocity impact scenarios, the effect of strain rates has been remarkably higher than quasi-static loading because the loading duration is very short. Thus, structural responses and failure modes will be different. The present study aims to investigate dynamic response and failure modes of simply supported two-way RC slabs exposed to low-velocity impact load. In the experimental part of this study, nine RC slabs with the dimension of 1,000 × 1,000 × 80 mm were tested. The reinforcement ratio of RC slabs and the input impact energy applied to RC slabs were experimental variables investigated. A drop-weight test setup was utilized to apply impact load to RC slabs. By varying drop-height as 1,000, 1,250 and 1,500 mm, three different impact energies have been applied to RC slabs via a hammer of which weight is 84 kg. The time histories of the accelerations, displacements and impact loads were recorded. The dynamic responses obtained by tests and the failure modes observed has been interpreted in detail. Besides, a finite element model where explicit dynamic analysis is performed has been established for verification of the experimental results. There was observed good accordance between numerical and experimental results. Consequently, it is considered that the present finite element treatment can be used for the evaluation of the dynamic responses and failure modes of RC slabs exposed to low-velocity impact load. © 2019, Korean Society of Civil Engineers

Performance of engineered cementitious composites under drop-weight impact: Effect of different mixture parameters

Current research focuses on the experimental and numerical determination of impact performance of engineered cementitious composites (ECC). Performance assessment of ECC beams with different mixture parameters was made. Mixtures were produced with different replacement rates of Class-F fly ash and slag with Portland cement, water to binder ratios and fiber types (polyvinyl alcohol [PVA] and nylon [N]). Experimental works were validated with incremental dynamic analyses performed by ABAQUS finite element software. Impact testing results were further supported by mechanical property results. Results reveal that each individual mixture parameter used is distinctively effective in modifying the properties under both sudden impact and slow static loading. In brief, enhanced impact resistance is noted when ECC is produced with slag, low amounts of pozzolanic materials, low W/B ratio, fiber addition and PVA fibers. Experimental results were also in line with the numerical results from ABAQUS largely. Significantly, cost-effective N fibers were also shown to be fully replaceable with costly PVA fibers without jeopardizing mechanical/impact performance, if mixture design parameters are adjusted suitably. Current research is likely to attract further research on the development of ECC that is with lower cost and comparable impact/mechanical performance with regards to widely studied more expensive counterparts in the literature. © 2019 fib. International Federation for Structural Concret