Reinforcement Arrangement Research Articles

Numerical Study on the Effect of Different Steel Reinforcement Arrangement in Reinforced Concrete Wall Subjected to Blast Load

Reinforced concrete (RC) is the most preferred construction material for the civilian structural construction such as building and bridge because it is economical to build and possesses high strength. There have been several verified numerical studies on RC, but most have all been limited to the scope of a small rectangular or small square RC panel clamped at the edges. As a result, there is still a need for a complete RC structure for example RC wall with its foundation to represent as a single stand structure. With available validated complete RC structure experimentally and numerical data on blast pressure profile, detail numerical study is possible to investigate in depth. In AUTODYN commercial software, arbitrary Lagrange Euler (ALE) solvers are used to analyse the interaction between air and RC wall structure. The RC walls were built with the same moment resistance but a different hooked direction on vertical flexural steel reinforcement into the foundation. The numerical result indicated that in the hooked-in direction, the average strain at the back side of the wall peaked at 1.0625×10-3 at first 5 msec after impact, which is half of what it was in the hooked- out direction. Furthermore, the numerical simulation coincided with the experimental findings, where the proper steel arrangement for the RC wall subjected to blast was hooked-in.

Underwater blast response and pile failure analysis of submerged reinforced concrete piles and pile group foundations

This paper presents three-dimensional (3D) nonlinear finite element analyses of pile foundations in saturated sand deposits subjected to submerged explosions. In this contribution, the explosive response and failure analysis of reinforced concrete piled foundations and blast induced wave propagation are investigated. The arbitrary Lagrangian-Eulerian (ALE) analysis tool available in the finite element software LS-DYNA is employed to simulate blast loadings. Parametric sensitivity studies are conducted for pile reinforcement arrangements, explosive charge mass, and the effect of pile head constraint conditions. Also, explosive stress wave propagation in saturated media is investigated. For this purpose, extensive numerical modellings are performed under different explosive charge shape and weights. By adopting suitable material models, the strain-rate-dependent behavior of saturated soil domain, steel reinforcements, concrete piles, and cap piles are simulated. Pile lateral displacements, explosion wave velocity, stress distributions, and pile foundation damages are illustrated in order to study the dynamic response of submerged pile foundations. It has been observed that, the reinforcement arrangement has significant effects on the behavior of the piles subjected to submerged explosions. It was also observed from results that the pile spacing in a pile group affects the bearing capacity of pile groups under explosive conditions. The findings of this research provide valuable information regarding the effects of underwater explosions on submerged piled foundations, guide engineering designers and are considerable for design codes.

Stress Field Approach for Prediction of End Concrete Cover Separation in RC Beams Strengthened with FRP Reinforcement.

End concrete cover separation is one of the most common failure modes for RC beams strengthened with external FRP reinforcement. The premature failure mode significantly restricts the application of FRP materials and could incur serious safety problems. In this paper, an innovative stress field-based analytical approach is proposed to assess the failure strength of end concrete cover separation and the conventional plane-section analysis is extended to evaluate the corresponding carrying capacity of FRP-strengthened RC beams. First, the dowel action of reinforcement and the induced concrete splitting, reflecting the interaction between concrete, steel and FRP, are considered in establishing the geometrical relationships of stress field for cracked concrete block. Then, the cracking angle and innovative failure criterion, considering the arrangement of steel and FRP reinforcement and cracking status of concrete and its softening effect, are derived to predict the occurrence of concrete cover separation and related mixed modes of debonding failure. Subsequently, an extended sectional analytical approach, in which the components of effective tensile strain of FRP resulted from flexural and shear actions are both considered, is presented to evaluate the carrying capacity of strengthened beams. Finally, the proposed calculational model is effectively validated by experimental results available in the literature.

Determining the effect of reinforcing a cement-concrete coating of bridges on the stressed-strained state of structures

This paper reports a study of the cement-concrete coating on bridges using FRP reinforcement. That has made it possible to design optimal structures by selecting the height for reinforcement arrangement in the layers of a roadbed in order to ensure strength characteristics. An engineering method for calculating a hard roadbed with composite reinforcement has been devised, which makes it possible to take into consideration its work both in a joint package of the structure with a slab and separately – when it exfoliates from the slab of the bridge's span structure. Underlying this research are effort-determining methods, estimation dependences from the theory of bending layered structures, as well as dependences from elasticity theory to assess the strength of materials for a roadbed. The consideration of shear strains when designing slabs has helped establish that the deflections according to the devises method were 1.4 times larger than those in the classical approach. The method was tested by a numerical experiment, which confirmed the need to use composite reinforcement in the upper layers of a road surface on bridges, which improves its durability by 1.2 times. The results of the numerical experiment indicate that the equivalent stresses in the lower layers of a free-moving roadbed were 2.91 MPa, and, when operating in a joint assembly with a slab, they took a negative value (–0.2 MPa). Practical application of the devised calculation method makes it possible to determine the refined normal stresses in the layers of a roadbed, taking into consideration the characteristics of structure operation. Owing to this, additional opportunities open up for calculating the roadbeds of bridges whose design utilizes the most common types of span structures in the bridge industry.

Assessment of seismic behavior of back-to-back mechanically stabilized earth walls using 1g shaking table tests

In current study, the effect of overlap length of reinforcements (LR) and arrangement of connecting two opposing walls to each other on the seismic behavior of back-to-back MSE walls (BBMSEWs) was investigated using reduced-scale 1-g shaking table tests. Results showed that fundamental frequency (ff) of BBMSEWs strongly depends on the arrangement of reinforcements and the ff value decreases with decreasing LR and separating two opposing walls from each other. It was also concluded that increasing the overlap length of reinforcements and separating the bottom half of two walls from each other can be two good solutions for reducing the possible acceleration amplification in BBMSEWs. The combination of a slant and a reverse curve with certain intersection point was observed as the failure surface in all the models. The geometry of failure surface was found to be unaffected by LR changes and only dependes on the arrangement of connecting two opposing walls to each other. On the other hand, the increase in ay values due to increasing LR and connecting two opposing walls to each other showed that the use of direct connection of two walls and applying a suitable LR can be considered as two suitable solutions to improve the seismic stability of BBMSEWs. It was also found that although the use of overlapping reinforcement instead of the direct connection of two walls to each other leads to increasing the lateral displacements, but it can be a good solution for reducing mobilized reinforcement forces in BBMSEWs.

Behavior of thin reinforced concrete slabs and effect of reinforcement bars subjected low-velocity impact

Low-velocity impacts of thin reinforced concrete (RC) slabs are considered in accidental falling objects during building constructions. In such scenario, reinforcement bars may show resistance against perforation. If the effect of reinforcement bars against perforation behavior of RC slabs can be evaluated, it allows more rational protection and construction planning. In this study, an experimental and numerical investigation has been presented to evaluate the effect of reinforcement bars on perforation behaviors of thin RC slabs subjected to low-velocity impacts assuming accidental falling objects onto underlying slabs during building construction. Two impact tests were performed with impact energy and reinforcement amount as parameters. The experimental results show that increasing the amount of reinforcement leads to increased perforation resistance. To evaluate the effect in greater depth, a numerical analysis was performed with varying reinforcement arrangements and impact energy. The analytical result reproduced the behavior of the RC slabs observed in the experiment including perfect perforation. The numerical results have shown that the perforation resistance of the slabs improved with the increasing amount of reinforcement, even under conditions other than those in the experiment. Furthermore, based on the experiment and analysis, a perforation resistance mechanism has been proposed for reinforcement bars in a range beyond the perforation limit calculated by the empirical formula, and the calculated results based on this mechanism have corresponded to the perforation behavior of thin RC slabs obtained from the experiment and analysis.

Finite Element Analysis of CFRP Strengthened Bundle RC Column Subjected to Repeated Impact Load

This paper studied numerically the behavior of carbon fiber reinforced polymer (CFRP) confined bundle reinforced concrete (BRC) columns subjected to repeated impact load. To verify the numerical models with previous experimental tests, Abaqus/Explicit based nonlinear finite element (FE) model was developed. Based on the proposed FE analysis, a parametric study was conducted to investigate the effects of different factors such as CFRP confinement, eccentric axial load, bundle reinforcement arrangement, and column height on repeated impact capacity of RC column. While modeling the structural element, concrete damage plasticity (CDP) model is adopted to account for the plastic and strain rate-dependent behaviors of concrete material under impact load. From the nonlinear FE analysis result, it was found that CFRP confinement improved the impact capacity of bundle reinforced concrete column. As column height increased, the column impact resistance was found to decrease. Moreover, when the CFRP strengthened BRC column specimens were repeatedly impacted, the continuous matrix material was severely damaged, while the fiber showed only minor and gradual compressive failures.

Experimental Investigation on Punching Shear Mechanism of Concrete Interior Slab-Column Connections without Shear Reinforcement

The punching shear failure of reinforced concrete flat plates has puzzled researchers for a long time due to the complexity of the punching shear mechanism and the difficulty of direct measurements of the internal failure mechanism. Measurements from previous punching shear tests cannot provide sufficient experimental evidence for revealing the failure mechanism. In this study, an industrial endoscope and specially designed strain measuring rods were installed inside small holes reserved in slabs around columns to track the occurrence and propagation of internal cracks of five isolated slab-column connections with different longitudinal reinforcement arrangements. The results indicated that critical shear cracks developed from internal diagonal cracks initiated at midheight of the slabs and unevenly distributed around the columns. The propagation of the internal diagonal cracks was independent of flexural cracks initiated at the slab tension faces but closely related to the unloading of radial strains of concrete at the slab compression faces. At the moment of punching failure, the critical shear cracks propagated from compression to tension zones, forming a punching failure cone. Moreover, the failure process was progressive, that is, the continuous weakening of the compression zone by the critical shear crack resulted in the shear splitting of the compression zone, which triggered the final failure of the connections. The experimental evidence obtained can provide a physical background and new ideas for modeling the punching shear mechanism of slab-column connections.

Damage assessment of RC columns under the combined effects of contact explosion and axial loads by experimental and numerical investigations

Understanding physical phenomena such as blast shock waves produced by controlled explosions is useful for problem solving in military and civil fields. The current study analyses the damage response of reinforced concrete (RC) columns exposed to contact explosion effects through experimental trials and numerical simulations and is divided into two sections: (a) experimental studies to perform and measure the damage of columns and (b) numerical studies to define the minimum quantity of pentolite 50/50 needed to collapse different RC column designs. Validation studies proved that the model was reasonably accurate. Relevant findings include the following: (a) the damage process until collapse presents a sequence in which (1) the concrete cover is fragmented, (2) the transverse bars suffer shear, (3) the longitudinal bars buckle, and (4) the concrete core is partially and fully fragmented; (b) in the case of detonations that exceed 500 g of pentolita, the type of transverse reinforcement arrangement in the RC column has significance on the final damage; and (c) the axial load increases the blast strength of the column and improves the concrete core confinement.

Effect of Weathering on Some Mechanical Properties of Prosthetic Composites

In this research, the concerted influence of ultraviolet (UV) light and water spurting on the mechanical characteristics of the naturally strengthened composites was explored. Specimens fabricated by the vacuum bagging procedure were subjected to an accelerated weathering device for 100 h. Tensile, flexural; compression tests were executed to assess the mechanical characteristics. The laminates encompass woven synthetic and natural fabric. The results exhibited that consuming altered forms of reinforcing materials had an abundant influence on the properties and the values of (tensile, flexural, and compressive characteristics) reduced under the collective influence of UV and water spurting cycles. The results advocate that the arrangement of natural and synthetic reinforcements permits the preparation of biocomposites with improved performance. This work revealed the assets of natural hybrid reinforced Polymethyl methacrylate resin composites (hybridized at various volume percentages and lamination layup), which have not been tried up to now.

Tensile and Stress Analysis of Hybrid Composite Prosthetic Socket Reinforced with Natural Fibers

Natural fibers and their composites are the evolving movements in material science, and with that, the utmost use of plant-based fibers has become the focus of this research. Sisal and cotton natural fibers were used to construct a prosthetic socket as an attempt to substitute material currently available in the manufacturing of sockets. The vacuum bagging technique was adopted to produce a below-knee socket. The influence of different fiber layering sequences on the volumetric and mechanical characteristics was estimated experimentally and numerically. Mechanical tensile tests were used to assess laminated specimens, such as tensile strength, young modulus, and elongation percentage. The number and type of reinforcing layers had an effect on mechanical properties, and the best composite specimens were three layers of sisal with two layers of carbon fiber, with tensile strength and modulus of elasticity reaching (261–4760) MPa, respectively. The finite element method (ANSYS- 16.1) was used to anatomize by seeing the contours distribution of safety factor, equivalent Von Mises stress, equivalent Von Mises strain, and total deformation. This procedure was executed by building ten models for the socket, which served as three-dimensional structural composite materials. The results of the present study advocate that the arrangement of natural and synthetic reinforcements allow the preparation of bio-composites with enhanced performance. This work revealed the assets of sisal and cotton fiber hybrid reinforced PMMA resin composites (hybridized at diverse volume percentages and lamination layup), which have not been tried up to now.

Microscopical and corrosion studies on Al6061 − 10% Al2O3 functionally graded metal matrix composites

The objective of this work is to manufacture Aluminium reinforced with 10 wt% Alumina Functionally Graded Metal Matrix Composite (Al6061 − 10 wt% Al2O3 FGMMC) through horizontal centrifugal casting process and to investigate its microstructural and corrosion properties. The microstructure was examined along the radial direction of the FGMMC and it indicated that the gradient arrangement of reinforcements across the radial direction with supreme alumina particles reinforcement at the outer periphery. Corrosion tests were carried out on the samples cut from the outer periphery of the FGMMC using an acidic immersion corrosion test. The influence of corrosion parameters such as 1 M acidic solution (Sulphuric, Hydrochloric and Nitric acid) and immersion time (0 to 220 h) on corrosion rate was analyzed. The result revealed that the reinforcement had no effect on the corrosion rate and also the samples immersed in the hydrochloric acidic solution showed higher corrosion rate in the early period of immersion time due to the presence of chloride ions.

Experimental Investigation on the Behavior of Gravelly Sand Reinforced with Geogrid under Cyclic Loading

In view of the dynamic response of geogrid-reinforced gravel under high-speed train load, this paper explores the dynamic characteristics of geogrid-reinforced gravel under semi-sine wave cyclic loading. A number of large scale cyclic triaxial tests were performed on saturated gravelly soil reinforced with geogrid to study the influence of the number of reinforcement layers and loading frequencies on the dynamic responses of reinforced gravelly sand subgrade for high speed rail track. The variation of cumulative axial and volumetric strains, excess pore pressure and resilient modulus with number of loading cycles, loading frequency, and reinforcement arrangement are analyzed. The test results reveal that the cumulative axial strain decreases as the number of reinforcement layers increases, but increases with loading frequency. The resilience modulus increases with the number of reinforcement layers, but decreases as the loading frequency increases. The addition of geogrid can reduce the excess pore water pressure of the sample, but it can slightly enhance the rubber mold embedding effect of the sand sample. As the loading frequency increases, the rubber mold embedding effect gradually weakens.

Bonded anchors with post-installed supplementary reinforcement under tension loading – Experimental investigations

This paper presents the results of comprehensive and systematic experimental investigations carried out on anchorages (single anchors and groups) of bonded anchors supplemented with post-installed reinforcement subjected to tension loading. Until now, the use of supplementary reinforcement is allowed in the codes only for anchorages with cast-in headed anchors supplemented with cast-in reinforcement. In this work, tension tests are performed on single anchors and anchor groups with different amounts and arrangements of post-installed reinforcement. Epoxy based mortar was used for installation of both anchors and the reinforcement. It was found that the post-installed supplementary reinforcement can significantly increase the capacity of anchorages undergoing concrete cone breakout failure. Due to high bond strength of the mortar, even relatively short bond lengths within the breakout body were sufficient to activate the reinforcement and contribute significantly towards the resistance. The ultimate load was limited either by reinforcement yielding (for low amounts of reinforcement) or strut failure (for moderate to high amounts of reinforcement). Not just the amount but also the placement and arrangement of reinforcement plays an important role in the tension behavior of anchorages with post-installed supplementary reinforcement. At peak load, both the concrete as well as reinforcement contribute significantly to the resistance of the anchorage.

Innovative method for assessing the fire resistance of a monolithic reinforced concrete beam floor slab of a building

The essence of the proposed innovative method lies in the fact that the testing of a monolithic reinforced concrete beam slab of a building is carried out without destruction, according to a set of single quality indicators, while evaluating their value using statistical control. To do this, the geometric dimensions of the beam slab, the heating scheme of the design section under fire conditions, the placement of reinforcement in the section, the depth and degree of its fire protection, the rate of thermal diffusion of concrete, the value of the test load on the monolithic beam reinforced concrete slab and the stress intensity in the rods of the longitudinal working reinforcement are determined. Application of the proposed method will determine the actual fire resistance of a monolithic reinforced concrete beam floor slab without full-scale fire exposure.

Usporedba učinkovitosti tragača armature i georadara u ocjeni stanja konstrukcija: primjeri iz prakse

An essential step in the condition assessment of reinforced concrete structures and evaluation of the residual capacity is the determination of the arrangement and quantity of reinforcement as well as the geometry of the structural elements. The objective of this paper is to present the fundamentals in the application of two non-destructive methods, cover meter and ground penetrating radar, in the determination of the above structural features. A comparison of the two methods is presented and their capabilities, advantages and disadvantages are shown through nine case studies.

Effect of Different Fiber Reinforcements on Some Properties of Prosthetic Socket

In the perspective of environmental advance, significant attentiveness is being displayed in the usage of natural fibers like reinforcement in polymer composites. This paper focuses on building a prosthetic socket arranged from natural fiber-reinforced composite as an effort to substitute material currently accessible in the manufacturing of the socket. The vacuum bagging procedure was adopted to yield a below-knee socket. The laminates encompass woven flax, sisal, cotton, carbon, person, and glass fabric. The impact of diverse fiber layering sequences on some of the physical and mechanical characteristics was assessed. Laminated specimens were characterized by tests such as (hardness, surface roughness, density, water absorption). The results of this study showed that consuming altered forms of reinforcing materials had an abundant influence on the properties of prepared composite and the values of (hardness, surface roughness, and density) properties improved with increasing of the volume fraction of materials and the best composite specimens were three layers of flax with two layers of carbon fiber, were the hardness property ranges 86 MPa and density of (1.276 gm. /cm3) due to their exceptional mechanical properties. The results of the present study advocate that the arrangement of natural and synthetic reinforcements allows the preparation of bio-composites with enhanced performance.

Numerical investigation of concrete filled hollow precast composite columns subjected to lateral cyclic loading

This paper describes a numerical study performed to investigate the behaviour of concrete infilled hollow precast composite columns (HPCC) subjected to lateral cyclic loading. Finite element analysis of monolithic (RC) and composite (HPCC1 and HPCC2) columns are performed and the results thus obtained are compared with documented experimental results. The present study focuses on the capability of numerical codes to capture the behaviour of the columns, such as load–displacement relationship, softening and failure modes under cyclic loading. To capture the performance of tested composite columns, a study was first performed to select a suitable material model that can further be considered appropriate to depict the cyclic performance of reinforced concrete (RC) structures. Moreover, the investigation was performed to model two concrete surfaces (precast and cast-in-situ) in contact through a contact algorithm for a precast encased composite column. Finally, a study on interface shear stress transfer mechanism and effects of confinement provided by the encasement to the inner core was performed for HPCC1 and HPCC2 composite columns. After performing numerical study and comparing with the obtained test results, a continuous surface cap material model (MAT 159) available in LS-DYNA FE code was observed to be suitable to model concrete for analyzing the behavior of RC structures subjected to lateral cyclic loading. Moreover, to simulate the behaviour of composite structures, the use of a tiebreak contact algorithm is suggested. It was observed that due to the presence of cross-ties penetrating into the inner core of HPCC1, the composite action between the inner core and outer precast encasement was enhanced, with delayed damage in the outer encasement. However, in composite column HPCC2, the ties did not penetrate into the inner column core, so interface shear strength, resulted only from cohesion and friction, caused severe damage in the outer encasement at ultimate load. The presence of a single tie and smaller thickness of precast encasement in HPCC1 resulted in lower displacement ductility of HPCC1 compared to composite column HPCC2. Moreover, parametric studies were performed to elucidate the influence of the thickness of the precast plate and reinforcement arrangement to enhance the ductility of the composite columns through a series of numerical analyses of the modified columns.

Behavior of RC Wide Beams under Eccentric Loading

Wide beams are one of the widely used structural elements in RC buildings due to the many special features that characterize them. The main objective of this research is to investigate the behavior of wide shallow beams under the effect of eccentric loading acting along their cross sections. To achieve that, an experimental program that consisted of seven wide beams was conducted. All beams were loaded using two concentrated loads at their middle third where the main parameters considered were: the magnitude of the load eccentricity, the longitudinal spacing between shear reinforcement, and the arrangement of the longitudinal reinforcement. Following that, a finite element analysis was performed where the analytical model used was first verified using the data from the experimental program. The results from both the experimental and analytical programs were in good agreement. Then, the finite element analysis was extended through a parametric study where other variables were studies such as the compressive strength of concrete, the transverse spacing between stirrups and the longitudinal reinforcement ratio. The results showed that the value of the load eccentricity, spacing between shear reinforcement, the arrangement of the main reinforcement along the beam cross section, and the compressive strength of concrete significantly affected the torsional resistance of shallow wide beams. Conclusions and recommendations are presented which can be useful for future researchers. Doi: 10.28991/cej-2021-03091766 Full Text: PDF

Monotonic and cyclic stress-strain models for confined concrete-masonry shear wall boundary elements

Simulation of the seismic response of fully grouted reinforced masonry shear walls (RMSWs) built with reinforced masonry boundary elements (RMBEs) necessitates reliable nonlinear models of their RMBEs. The axial monotonic and cyclic full stress-strain curves of RMBEs are essential for predicting the lateral cyclic response of RMSWs with boundary elements. Therefore, a reliable stress-strain constitutive model for the axial monotonic and cyclic behavior of RMBEs is required. The authors recently investigated the axial monotonic compressive behavior of unconfined and confined RMBEs built with different section configurations, vertical reinforcement arrangements, transverse confinement ratios, and different construction procedures. In the current study, the authors investigated the cyclic behavior of some RMBEs whose counterparts were previously tested under axial monotonic compression. In addition, more specimens with different confinement configurations and different grout strengths were tested. Comparisons of the test results showed that increasing the vertical reinforcement ratio increased the axial load carrying capacity of the tested RMBEs but decreased their strain ductility. In addition, using a low compressive strength grout significantly reduced the strain ductility of the RMBEs. Moreover, monotonic and cyclic stress-strain models for confined and unconfined concrete-masonry boundary elements subjected to axial compression loading were developed. The proposed models showed good-to-excellent agreement with the experimental results, predicting the stress-strain rising curve, stress drop, and postpeak behavior. Furthermore, unloading and reloading curves, strength degradations, and softening of reversal and reloading branches due to cyclic degradations were well captured by the proposed model.