Reinforcement Arrangement Research Articles

Confinement effect of different arrangements of transverse reinforcement on axially loaded concrete columns: An experimental study

AbstractConcrete behaves as a brittle material due to its low inherent tensile strength, but it can also exhibit a markedly ductile behavior when coupled with transverse reinforcement like steel stirrups. The role of stirrups is to enhance confinement effect, to restrain the lateral expansion of concrete, thus modifying the concrete stress-strain constitutive law and enabling higher compression strains and higher ductility. This paper focuses on the confinement effect induced by different arrangements of transverse reinforcement on axially loaded concrete columns. An experimental campaign has been carried out, comprising 18 concrete columns with two different mechanical strengths and reinforced with three different layouts of stirrups, namely typical closed square hoops, closed stirrups with additional cross ties, and a novel type of stirrups involving rectangular hoops with additional restraint plates, the latter offering an enhanced diffused confinement action and limiting extensive spalling of the cover concrete. Formation and propagation of longitudinal micro-cracks are reduced with the novel type of diffused stirrups and a moderate-to-high increase of ductility is observed. However, the beneficial effects induced by diffused stirrups are more pronounced in medium-strength concrete and almost negligible in low-strength concrete that collapses due to a brittle cracking failure without involving the confinement action of the transverse reinforcement.

Consideration of the state of corrosion in seismic assessment of columns

Purpose Seismic assessment procedures of RC members quantify member strength, deformation capacity and failure mode using detailed information regarding member geometry and reinforcement amount and arrangement. However, the condition of the reinforcing materials is not explicitly accounted for in the calculation process. The paper aims to discuss this issue. Design/methodology/approach This problem is explored in the present paper through consistent evaluation of the evidence from a database of column tests which were subjected to cyclic lateral load reversals simulating earthquake effects after being subjected to accelerated corrosion. The column performance expressed in terms of the shear vs drift resistance envelope is introduced in the available methodologies of rapid assessment of reinforced concrete structures showcasing the limitations and uncertainties of the existing state of the art in the field of seismic assessment of existing structures. Findings Simple estimations as well as experimental observation show that the effect can be staggering, in terms of reduced deformation capacity, prevailing mode of failure and residual strength under seismic loading. It has been observed in the field that deterioration and ageing can reduce a well detailed structural component to behave as a poorly constructed one, by means of cover delamination, transverse and longitudinal bar area loss and steel embrittlement. Originality/value The amount of deterioration in the residual life of the component, in the face of a future seismic hazard, is fraught with uncertainty regarding the amount and intensity of material deprecation and the manner in which this may be considered in the logistics of the assessment process.

Concrete beams with different arrangements of GFRP flexural and shear reinforcement

This paper presents experimental research on the flexural and shear behaviour of concrete beams reinforced with glass fibre reinforced polymer (GFRP) composite reinforcement. Three-point bending tests on shear critical concrete beams reinforced with GFRP longitudinal bars and GFRP stirrups are presented. The test variables were the size and spacing of closed loop stirrups as well as the size, amount, and arrangement of longitudinal reinforcement. Twelve beams were tested with four different stirrup arrangements and three different longitudinal reinforcement arrangements. Longitudinal bars were instrumented at mid-span and stirrups were instrumented at the straight and bent portions. The beams had a shear-span-to-effective-depth ratio of 2.5 and behaved like deep beams. The beams without stirrups failed in shear-tension while the beams with stirrups failed in shear-compression with no ruptured stirrups. Longitudinal reinforcement strains showed evidence of a tied arch mechanism. The analysis found diminishing increases in shear strength with increasing shear reinforcement ratio when failure occurred as a result of crushing of confined concrete.

Behaviour of continuous reinforced concrete floor slabs subjected to different compartment fires

This paper presents the experimental results of four continuous reinforced concrete slabs with three compartments under different compartment fire scenarios. The research focuses on the quantitative relationships of the compartment fire temperatures, the temperature distribution along the thickness of the slabs, the vertical and horizontal deflections, the crack patterns and failure modes of the slabs and the corners’ reaction forces. The results indicate that for a continuous floor slab, the central vertical deflection of the slab in the middle compartment is considerably affected by the vertical deflections of the slab in the two edge compartments. The boundary condition, the ratio and arrangement of the top reinforcement of the continuous slab, and the fire spreading scenarios have important effects on the failure mode of the slab in different compartments. It is evident that more severe cracking happened within the slab in the middle compartment compared to the two edge compartments. For the edge compartment, the slab may fail by large deflection and the integrity failure of the slab in the middle compartment may occur. Increasing reinforcement ratio and using the continuous reinforcement are the effective methods to prevent or delay the failure of the continuous slabs with any fire spreading scenarios.

Comparing skill acquisition under varying onsets of differential reinforcement: A preliminary analysis.

The purpose of the current study was to evaluate the effect of implementing differential reinforcement at different times relative to the onset of teaching new skills to learners with autism spectrum disorder. Specifically, we first determined the most efficient differential reinforcement arrangement for each participant. Using the most efficient arrangement, we evaluated if differential reinforcement from the immediate onset, early onset, or late onset is the most efficient for learners to acquire a new skill. Three children diagnosed with autism spectrum disorder who have a history of receiving intervention based on the principles of applied behavior analysis participated in this study. The immediate onset of differential reinforcement resulted in the most efficient instruction in 6 of 7 comparisons. The results are discussed in light of previous studies and suggestions for future research are provided.

Bending Stiffness and Strength of Reinforcement Arrangements for CFRP Reinforced Glulam (AFRW)

Bending Stiffness and Strength of Reinforcement Arrangements for CFRP Reinforced Glulam (AFRW)

Effects of arrangement and shape of MWCNT and GNP reinforcements on nanocomposite mechanical properties

In this investigation, multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets were used to prepare two-phase and hybrid epoxy-based nanocomposites. Tensile and compressive mechanical pro...

Strengthening Of Cast-In-Situ Long-Span Reinforced Concrete Roofs Using Pre-Stressed Wire-Rope Reinforcement

The article describes the strengthening of monolithic reinforced concrete coatings of the large-span roof of the sports hall of the school with elements with a curvilinear arrangement of pre-stressed wire-rope reinforcement. The use of pre-stressed wire-rope reinforcement as a reinforcement of reinforced concrete floors and coatings made it possible to simplify the production of reinforcement elements, reduce the time of installation work and eliminate the execution of preparatory work on opening. In the process of installation, the reinforcement elements fixed on the structures perceive the loads, pre-strengthening and increasing their bearing capacity both from the bending moments and from the shearing forces (punching) on the supports. As a result of the work carried out, the mass of the used structures was significantly reduced and the costs of construction and installation work were reduced compared to traditional methods of strengthening.

Dynamic performance of concrete slabs reinforced with steel and GFRP bars under impact loading

Reinforced concrete slabs are common structural elements that could be exposed to impact loading. Although use of reinforced concrete slabs and utilization of Fiber Reinforced Polymer (FRP) as alternative to traditional steel reinforcement slabs are growing, but the influence of various parameters on their response under impact loads is not properly evaluated. This study investigated the effect of rebar’s material, amount and arrangement of reinforcements, concrete strength and slab thickness on dynamic behavior of reinforced concrete slabs using both laboratory experiments and numerical simulations. Performance of fifteen 1000 × 1000 mm concrete slabs, including two 75 mm thick plain slabs, five 75 mm thick steel reinforced concrete slabs, six 75 mm thick reinforced concrete slabs with Glass Fiber Reinforced Polymer (GFRP) bars and two 100 mm thick steel reinforced concrete slabs under drop weight impact loads was experimentally investigated. Failure mode, crack development, displacement-time, strain-time, and acceleration-time responses were studied and compared between various slabs. Finite element analyses and simulation of specimens were conducted using LS-DYNA explicit software. The results obtained from experiments and numerical models are in good agreement, and they indicate that increasing the reinforcement ratio or the slab thickness enhance the behavior of RC slabs under impact loads. By adjusting the amount and arrangement of GFRP, better performance in GFRP slabs than steel reinforced slabs can be achieved, which considering the corrosion resistance of this material, can make it an appropriate selection of reinforcement material.

Sliding stability and lateral displacement analysis of reinforced soil retaining walls

Field observations have demonstrated that reinforced soil retaining walls generally have superior seismic performance when compared to traditional gravity retaining walls. However, current design guidelines for reinforced soil retaining walls are typically based on pseudo-static methods of analysis, which involve simplifying assumptions. For instance, the reinforced zone is usually assumed as a rigid body in external stability calculations. As a result, the influences of reinforcement arrangement and properties on the sliding stability and displacement of the wall cannot be accounted for in their design. Additionally, the soil shear strength is assumed to be constant in conventional displacement calculations using the Newmark sliding block method. In this paper, an analysis method is proposed to determine the yield acceleration and lateral displacement of reinforced soil walls that includes soil shear strength mobilization and a two-part wedge planar failure mechanism. The proposed method is validated against the results of laboratory model tests, and influences of factors such as ground acceleration coefficients, and reinforcement and backfill properties on the stability of the wall are examined.

A Review on Pull out Test on Exterior Beam-Column joint

Conventional concrete loses its tensile resistance after the formation of multiple cracks. However, fibrous concrete can sustain a portion of its resistance following cracking to resist more loading. Use of the headed bar can offer a potential solution for these problems and may also ease fabrication, construction, and concrete placement. There have been many catastrophic failures reported in the past earthquakes, with Turkey and Taiwan earthquakes occurred in 1999, which have been attributed to beam–column joint failures. To achieve this performance level, special steel reinforcement details are required in the beam–column joint region of reinforced concrete framed structures. The experimental work carried out on four different arrangements of reinforcement of beam column joints. The aim of the research is to investigate the pull-out behavior such as strength, failure mode, and crack patterns of different arrangements of reinforcement in exterior beam column junctions. The transverse reinforcement of a joint reduces stresses by improving the confinement of concrete. All joints were tested by using reversed cyclic loading. In the first arrangement, the beam bars are extended in the column for distance Ld + (10xDia) from the inner face of column. This research studies the experimental behavior of full-scale beam-column space (three-dimensional) joints under displacement-controlled cyclic loading. Eleven joint specimens, included a traditionally reinforced one (without adequate shear reinforcement), a reference one with sufficient shear reinforcement according to ACI 318, and nine specimens retrofitted by ferrocement layers, were experimentally tested to evaluate a retrofit technique for strengthening shear deficient beam column joints.

Fracture grouting and geonails for soft soil tunnelling

ABSTRACTTo stabilise the tunnel faces and slopes in soft clay for the Airport Link construction in Australia, fracture grouting and glass fibre-reinforced plastic (GFRP) soil nails are proposed for the soil improvement as well as ease of handling. The compensation caused by the fracture grouting and the gain in strength due to consolidation as well as the geonail have stabilised the soft clay during construction. Only a small amount of ground settlement during soft clay box-jacking operation is generated so that the railway traffic above the embankment can be maintained without interference. The design method of the fracture grouting ground improvement study for this difficult project is discussed in this paper. Extensive laboratory and field tests were employed to verify the design assumptions and to fine-tune the ground improvement studies. The success of this project in poor ground conditions results from combined efforts of extensive field tests, an improved ground improvement design method and a realistic numerical analysis to assess the unstable/highly stressed zones for the placement of soil reinforcement.

Unified code-compliant equations for bending and ductility capacity of full and hollow rectangular RC sections

Simple closed-form code-compliant equations for determining the bending capacity of full and hollow rectangular reinforced concrete (RC) sections at yielding and ultimate are proposed. The equations, based on the material models of ACI 318-14 and EN 1992:2005, are fully parameterized and allow modeling square and rectangular cross-sections with steel arbitrarily distributed on all four sides and subjected to axial force and uniaxial bending moment. Because of their simplicity, the equations provide an efficient tool for performing parametric and stochastic massive analyses, and for rapidly assessing existing territorially-distributed infrastructural systems, such as highways and railways. The equations require the definition of the cross-sections material and geometrical properties and are of general validity, since any geometrical configurations, reinforcement arrangements and concrete constitutive models can be employed. The accuracy of the equations in predicting bending capacity (resisting moment), ductility and axial force-bending moment interaction domain of a representative sample of realistic full and hollow RC sections is demonstrated through comparisons with fiber analysis performed in OpenSees.

The effect of transverse and flexural reinforcement on deflection and cracking of GFRP bar reinforced concrete beams

This paper investigates the flexural behavior, deflection, and cracking of concrete beams reinforced with GFRP bars. For this purpose, 20 simply supported concrete beams with the cross-section of 250 × 250 mm and length of 2200 mm were constructed and tested. The parameters studied in this research are the amount and arrangement of transverse and flexural reinforcement. The results show that increasing the amount of transverse reinforcement of similar beams results in a significant increase in load-carrying capacity and a decrease in the crack widths and mid-span deflection until service load. Moreover, applying a small-diameter transverse reinforcement under the same reinforcement ratio showed a stronger effect on increasing the load-carrying capacity. Furthermore, using a small-diameter transverse and tensile reinforcement led to a higher effect on decreasing the crack widths. The average experimental-to-predicted load-carrying capacity ratio of beams with high flexural reinforcement ratio is slightly more than that of beams with low flexural reinforcement ratio.

Probabilistic assessment of load-bearing capacity of deep beams designed by strut-and-tie method

This paper presents probabilistic assessment of load-bearing capacity and reliability for different STM of deep beams. Six deep beams having different reinforcement arrangement obtained on the basis of STM but the same overall geometry and loading pattern were analysed. The used strut-and-tie models for D-regions of analysed elements have been verified and optimised by different researchers. In order to assess load-bearing capacity of these elements probabilistically, stochastic modelling was performed. In the presented probabilistic analysis of deep beams designed, the ATENA software, the SARA software and the CAST (computer-aided strut-and-tie) design tool were used. The reliability analysis shown that STM optimization should be a multi-criteria issue so that the obtained models were characterized by optimal stiffness with the assumed volume or weight and maximum reliability.

FINITE-ELEMENTAL ANALYSIS OF INFLUENCE OF DAMAGES OF BEAMS ON THE GENERAL TECHNICAL CONDITION OF MONOLITHIC REINFORCED CONVERGENCE

Purpose. To perform a simulation to estimate the impact of corrosion damage to the reinforcement of monolithic reinforced concrete flooring on the bearing capacity of a unit width of overlap and overlap in general. Methodology. The integral monolithic reinforced concrete overlay of the boiler house with overall dimensions of 12 × 12 m was to be investigated. The grid of the column was 6 × 6 m. The damage in the form of complete destruction of the protective layer of concrete of one of the 12 secondary beams and corrosion damage to 30% of its bearing reinforcing bars was investigated. Numerical simulation of stress-strain state of reinforced concrete structures was performed in the training version of the NASTRAN Femap 10.1.1 SC 32bit system. Two types of calculation are carried out: 1) calculation of a plate of unit width (in accordance with current regulatory documents); 2) calculation of the entire reinforced concrete floor (taking into account its joint work). Findings. The following is revealed: calculation № 1 proves the necessity of arrangement of strengthening of damages of a secondary beam of monolithic reinforced concrete floor. After the device is strengthened by the cage from the corners of the secondary beam, the stress is reduced both in the reinforcement and in the reinforcing bars to the stress level in the undamaged slab. Calculation № 2 shows that the arrangement of reinforcement of the clip from the corners of the secondary beam with cored reinforcing bars, taking into account the joint work of the whole plate, is not needed. Originality. Numerical modeling of the stressed-deformed state of reinforced concrete slab of unit width taking into account damages and the entire monolithic reinforced concrete slab is carried out, and the obtained results are analyzed. Practical value. The order of creation of models of reinforced-concrete designs and their finite element analysis is briefly given.

Topographical design of stiffener layout for plates against blast loading using a modified ant colony optimization algorithm

The stiffened plates are of demonstrable advantages and potential in offering high resistance to such extreme loading scenarios as blast. Since the distribution of the stiffeners has considerable effect on their performance, its design signifies an important topic of research. However, existing research has mainly focused on empirical design, and the configurations were largely experience based, which limits structural explosion-proof capacity. In order to improve the performance of stiffened plates against blast loading, we introduced here two new structural configurations of stiffened plates. In this study, the modified ant colony optimization (MACO) algorithm which introduces the mass constraint factor to the pheromone update function and integrates the idea of crossover and mutation was used to design the subjected to given working conditions. Specifically, material distribution of stiffeners is taken to be the design variables, and minimization of the maximum deflection of the center point of the plate to be the design objective under predetermined mass constraints. Compared with the baseline structure, the optimal designs largely improved the explosion-proof performance through distributing stiffener topology on the plates. The results showed that the optimum designs all present the reinforcement stiffeners to link with the fixed boundaries against the deformation. Moreover, the optimum designs placed more reinforcement materials in the central regions instead of four angles, and with the increase of the mass fraction, the reinforcement placement gradually extends from the center to the edges. The proposed method and new topological configurations are expected to provide some insights into design for novel protective structures.

Full scale tests of RC joints with minor to moderate seismic damage repaired using C-FRP sheets

After earthquakes FRP sheets are often used for the rehabilitation of damaged Reinforced Concrete (RC) beamcolumn connections. Connections with minor to moderate damage are often dealt with by applying FRP sheets after a superficial repair of the cracks using resin paste or high strength mortar but without infusion of thin resin solution under pressure into the cracking system. This technique is usually adopted in these cases due to the fast and easy-to-apply procedure. The experimental investigation reported herein aims at evaluating the effectiveness of repairing the damaged beam-column connections using FRP sheets after a meticulous but superficial repair of their cracking system using resin paste. The investigation comprises experimental results of 10 full scale beam-column joint specimens; five original joints and the corresponding retrofitted ones. The repair technique has been applied to RC joints with different joint reinforcement arrangements with minor to severe damage brought about by cyclic loading for the purposes of this work. Aiming at quantitative concluding remarks about the effectiveness of the repair technique, data concerning response loads, loading stiffness and energy absorption values have been acquired and commented upon. Furthermore, comparisons of damage index values and values of equivalent viscous damping, as obtained during the test of the original specimens, with the corresponding ones observed in the loading of the repaired ones have also been evaluated and commented. Based on these comparisons, it is deduced that the technique under investigation can be considered to be a rather satisfactory repair technique for joints with minor to moderate damage taking into account the rapid, convenient and easy-to-apply character of its application.

POOR FLEXURAL REINFORCEMENT PLACEMENT FACTOR ON THE PERFORMANCE OF CONSTRUCTED DRAINAGE SYSTEM.

22Dec 2018 POOR FLEXURAL REINFORCEMENT PLACEMENT FACTOR ON THE PERFORMANCE OF CONSTRUCTED DRAINAGE SYSTEM. Kachalla Mohammed. Civil and Water Resources Engineering Department, University of Maiduguri, N.E. Nigeria.

Applying Various Types of Loading on Continuous Deep Beams Using Strut and Tie Modelling

This work aims at presenting detailed procedures companied by numerical examples for designing reinforced concrete two span continuous deep beams under various types of loading; one concentrated force, two concentrated forces and uniform load for each span. Analysis and design was conducted based on Strut and Tie modeling (STM) of ACI 318M-14 since they contain significant extents of D-regions and they show a marked truss or tied arch action. It was found that changing the loading type has a significant impact on the capacity for the same specimen that has the same dimensions, concrete and steel properties, in addition to the same amount and arrangement of steel reinforcement. In more detail, the increase in the number of concentrated forces causes an obvious increase in ultimate capacity due to the reduction in span to overall height (a/h) ratio and the increase in the value of the strut-tie angle, which causes shortening in the length of the strut. Therefore, the ultimate capacity increased by about (44-70) % when the applied load was changed from 1-concentrated force to 2-concentrated forces or to uniformly distributed load.