Reinforcement Arrangement Research Articles

Shear behavior of a perfobond strip with steel fiber-reinforced mortar in a condition without surrounding reinforcements

To sufficiently transmit the shear force of a perfobond strip shear connector in steel–concrete hybrid structures, the arrangement of the surrounding reinforcements is essential to improve the restraining effect around the perfobond strip. However, in cases of joint structures with small dimensions and rush work on site, because the arrangement of reinforcements in the joint is challenging, steel fiber-reinforced mortar (SFRM) can be used along with a perfobond strip to improve the restraining effect around the perfobond strip. This study investigates the shear behavior of a perfobond strip that uses SFRM without surrounding reinforcements. Push-out tests were conducted focusing on the effect of steel fibers inside the SFRM, SFRM compressive strength, perforation diameter, and dimensions of the mortar block around the perfobond strip. Findings of the study confirmed that the steel fibers inside the mortar contribute to the restraining effect around the perfobond strip, thus preventing a rapid drop in the shear force beyond the shear capacity of the perfobond strip. The shear capacity of the perfobond strip combined with SFRM increased with the perforation diameter, SFRM compressive strength, and dimensions of the mortar block around the perfobond strip. Several shear capacity evaluation equations proposed in previous studies are not applicable for evaluating the shear capacity of the perfobond strip that uses SFRM without surrounding reinforcements. Here, the shear capacity of the perfobond strip can be evaluated by considering the correlation between the experimental parameters of this study, but more test data are required.

Numerical Examination of Reinforced Concrete Skew Slabs

Skew slab structures are frequently investigation used in modern construction in the form of non-orthogonal reinforced concrete slabs supported by skew grid of beams. Skew bridges allow roadway alignments to a huge selection of solutions. Skew slabs contribute to a minimal environmental impact for recent road construction projects. Thus, it is difficult to analyse the skew slab bridges than the right angled bridges. The primary objective of this project is “Numerical Examination of Reinforced Concrete Skew Slab”, is to determine the effect of different arrangement of steel reinforcement in the reinforced concrete skew slabs. For skew slabs, the sides are not orthogonal and so it is a matter of interest to study the effect of different types of reinforcement schemes to arrive at the best arrangement. ANSYS (R.18.1) software was used for the analysis of skew slabs. Except the reinforcement alignment, dimensions are similar in all the skew slabs. For identifying the effective reinforcement pattern in skew slabs, deformation, stress, strain behaviour were studied. By comparing the datas for three types of reinforcement pattern in skew slab, the effective pattern will be observed in pattern having least values in solution. On analysis, the behaviour of different reinforcement pattern for the designed skew slab is studied using ANSYS (R.18.1) and the effective reinforcement pattern is suggested.

Blast protection of concrete columns with thin strips of GFRP overlay

Reinforced concrete columns are basic structural elements found in many buildings. Studies of their structural behaviour are typically concerned with quasi-static loading conditions. Lately, an interest into loading effects from explosive blasts has emerged. This is due to unconventional hazards such as global terrorism. Implementing a standoff distance between a building and a potential hazard is not always possible, especially in urban environments. Other strategies of blast protection must be considered. Current experimental work was carried out to test the effectiveness of structural strengthening of concrete columns by thin strips of glass fibre reinforced polymer overlay. The specific reinforcement arrangement was chosen for its low cost and for ease of application. Concrete columns were designed and produced in model-scale proportions. Matching pairs of regular and retrofitted columns were loaded by short clearance detonations. Regular rebar reinforced columns and short steel fibre reinforced columns were tested. Retrofitting improved the residual compressive strength of short fibre reinforced columns. The overall fragmentation/spalling effects for concrete were also reduced. The strength improvements for rebar reinforced columns were insignificant, due to specifics of the retrofit scheme.

Ductility and durability enhancement of concrete EPS by new reinforcement arrangements and polypropylene FRC utilization

The majority of precast concrete electric pole structures (EPSs) consist of prestressed concrete and reinforced concrete hybrid members with high slenderness ratios. Currently, large prestressing (PS) forces are being applied to EPSs to carry heavier weights of electric transformer machineries and to reduce deflection by increasing structural stiffness. Moreover, when EPSs are exposed to an outdoor environment year-round, their durability decreases. Therefore, the objectives of this study are to transform the failure behavior of EPSs from brittle to ductile by varying the number of PS tendons and steel rebars, and to improve the ductility and durability of the EPS by using short polypropylene fiber-reinforced concrete to control crack formation and propagation. Six different types of EPS specimens were manufactured and tested to evaluate their maximum flexure capacity and to verify their ductility behavior. The results showed that the modified EPSs displayed ductile failure behavior while either maintaining their original flexural strength capacity or improving it compared with the current EPSs sold on the market.

Investigation of Factors Affecting Distresses on Continuously Reinforced Concrete Pavement using Ground Penetrating Radar

The utilization of continuously reinforced concrete pavement (CRCP) has been widely used throughout the United States during the construction of interstate highways since the 1930s. The essential design criterion of CRCP is to manage the crack type, size, and spacing that forms to reduce the distress; thus, identification of the factors affecting the location and extent of the cracks and distresses provides a prediction for the service life of CRCP pavements. In this paper, the influence that reinforcement placement and concrete cover has on the distresses of CRCPs is investigated using ground penetrating radar (GPR) and eddy current technology at six major interstate and state highway locations in Georgia. It was concluded that pavement having inefficient concrete cover depth and pavement thickness results in increased clusters of single transverse cracks and/or punchouts. A result of this study is the recommendation that longitudinal reinforcement be placed at one-third of the depth of the slab from the top surface of the pavement. Furthermore, a distress factor (DF) was established as a good indicator of the performances of pavements relative to each other. Ideal pavement with no crack acquires a DF of 0. In this study, pavements in good, fair, and poor conditions received DFs of “0.03 and 0.05,” “0.97 and 0.98,” and “3.23 and 3.33,” respectively.

Seismic Performance Assessments of RC Frame Structures Strengthened by External Precast Wall Panel

In recent years, a variety of strengthening methods have been developed to improve the seismic performance of reinforced concrete (RC) frame structures with non-seismic details. In this regard, this study proposes a new type of seismic strengthening method that compresses prefabricated precast concrete (PC) walls from the outside of a building. In order to verify the proposed method, a RC frame structure strengthened with precast walls was fabricated, and cyclic loading tests were performed. The results showed that specimens strengthened using the proposed method exhibited further improvements in strength, stiffness and energy dissipation capacity, compared to RC frame structures with non-seismic details. In addition, a nonlinear analysis method, capable of considering the flexural compression and shear behaviors of the walls, was suggested to analytically evaluate the structural behavior of the frame structures strengthened by the proposed method. Using this, an analysis model for frame structures strengthened with precast walls was proposed. Through the proposed model, the analysis and test results were compared in relation to stiffness, strength, and energy dissipation capacity. Then, the failure mode of the column was evaluated based on the pushover analysis. In addition, this study proposed a simplified analysis model that considered the placement of longitudinal reinforcements in shear walls.

Axial performance of RC columns strengthened with different jacketing methods

This study aims to examine the potential of approaches proposed for transverse reinforcement arrangement in the jacket section of existing non-seismic or deficient columns to enhance the axial performance of these columns. To satisfy the requirements for the seismic details of column design specified in ACI 318-14, an original technique of arranging V-clips across the overlapped legs of channel-shape bars was proposed to form peripheral closed-hoops in the jacket section while avoiding the interruption of the existing column. Ten column specimens with large-scale dimensions were prepared by considering the jacketing method and the amount of transverse reinforcement in the jacket section as test parameters, following which they were tested under concentric axial loads by using a 40000-kN-capacity steel frame. In the test, concrete jacket columns prepared using the proposed V-clip technique showed an axial performance equivalent to that of the counterpart concrete jacket columns prepared using prefabricated bar units, the effectiveness of which was previously demonstrated in terms of the enhancement of axial stiffness, strength, and ductility as well as easier buildability for forming peripheral closed-hoops and supplementary ties in the jacket section. The restriction of the opening of the channel-shape bars by V-clips delayed the buckling of longitudinal reinforcing bars and resulted in less severe damage to the core concrete in the jacket section. Thus, concrete jacket columns reinforced with the proposed techniques exhibited higher values of axial ductility than conventional concrete jacket columns or columns jacketed with steel plates and carbon-fiber laminates.

Effect of concrete strength and longitudinal reinforcement arrangement on the performance of reinforced concrete beams strengthened using EBR and EBROG methods

Externally Bonded Reinforcement (EBR) is a common method to install fiber reinforced polymer (FRP) sheets using surface preparation approach. In recent years, a new method called Externally Bonded Reinforcement on Grooves (EBROG) has been introduced as an alternative to the EBR method to strengthen reinforced concrete (RC) beams. In the present study, eight RC beams with 250 mm width, 300 mm depth, and 2200 mm length with two different longitudinal reinforcement arrangements were cast and subjected to the four-point bending test. The specimens were divided into two groups of four specimens according to their strengthening technique, namely EBR and EBROG methods. In addition to the strengthening method, the effects of reinforcement arrangement and concrete strength were investigated. The results show normal strength concrete (NSC) beams strengthened with EBR and EBROG methods experience FRP debonding and concrete cover separation failure modes, respectively. On the other hand, in high strength concrete (HSC) beams both EBR and EBROG methods lead to FRP debonding failure mode. The results also show that the use of the EBROG method in the HSC specimens results in a substantial increase in the ultimate load-carrying capacity, mid-span deflection, and the area under the load-deflection curve up to the maximum load capacity compared to the EBR method. Finally, the comparison between load-carrying capacity obtained from the experimental tests and different analytical models are presented in the study.

Analysis of boundary condition effects on RC deep beams

The end support of deep beams could have different effects on behavior of the beams. In this paper, experimental results of 43 deep beams with span -to -depth ratio of less than 3, different reinforcement arrangements and boundary conditions were investigated and discussed. Results indicated that, boundary conditions have important effects on ultimate loads, modes of failure and deflections; but crack formation and their patterns are almost the same irrespective of applied boundary conditions. Furthermore, the ultimate loads of the beams with fixed ends are 1.2–6 times of simply supported and continuous deep beams, depending on amount of main bottom and top reinforcements. Furthermore, in fixed -end deep beams, modes of failure and ultimate loads mostly depend on top main reinforcement. To examine the beams theoretically, available standards and published proposed methods were used. Results indicated that, none of existing methods is suitable for fixed- end deep beams, except proposed method. However, the methods proposed by ACI 318–14 and CIRIA Guide 2 yielded very conservative results for simply supported deep beams.

Contribution of Transverse Reinforcement Configuration on Concrete Shear Capacity of RC Column

Proper design of transverse reinforcement in the RC column is needed to maintain its ability to deform under axial and shear load safely. Even though mandatory building codes for transverse support of the RC column exist, shear failure was still found in the last high earthquake in Pidie, Aceh, in 2016. Therefore, as an attempt to improve RC column strength and elasticity, the effect of transverse reinforcement configuration was evaluated experimentally to a column subjected to an axial and shear load. The experiment was conducted by using four-column specimens with a cross-section 200 x 200 mm. Four types of transverse reinforcement configurations were applied in each column. The test was carried out by loading an axial load always and shear load gradually until its failure. The test results show that the configuration of transverse reinforcement has a significant effect of maintaining column stiffness, which was subjected to compressive axial load and shear load. Furthermore, the arrangement of transverse reinforcement influences the compressive strength significantly and enhance the concrete shear capacity of a column due to its confinement effect.

A laminar box apparatus for 1g testing of granular columns embedded in soft clay

Ordinary stone columns and geosynthetic-encased columns are widely used as a method of soil improvement for soft clay deposits. The behaviour of encased and unencased columns under the action of dynamic loads are not thoroughly understood. In order to shed light into the dynamic behaviour of granular columns and column-enhanced soft soil deposits, a novel large-scale laminar box assembly is designed together with provisions for instrumentation, consolidation of clay slurry and casing pipe pushing units for column installation. The laminar box is comprised of 16 individually supported laminates. The laminar box has inner areal footprint dimensions of 900 × 900 mm and a height of 1932 mm. The laminar box is utilised to study the behaviour of granular columns of varying reinforcement stiffnesses under dynamic loads. In order to make a thorough comparison of reinforcement stiffnesses on column behaviour, columns with different reinforcement arrangements are installed together in the same clay bed, and scaled earthquake accelerograms and sinusoidal base excitations are applied. Column response is studied through the reinforcement strains occurring on the encasement and the amount of vertical pressure sustained on the column during the dynamic load cases.

Experimental study on seismic behavior of exterior composite beam-to-column joints with large size stiffened angles

The top-and-seat angles with double web angles are commonly used in the design of beam-to-column joints in Asian and North American countries. The seismic behavior analysis of these joints with large cross-section size of beam and column (often connected by four or more bolts) is a challenge due to the effects from the relatively larger size of stiffened angles and the composite action from the adjacent concrete slab. This paper presents an experimental investigation on the seismic performance of exterior composite beam-to-column joints with stiffened angles under cyclic loading. Four full-scale composite joints with different configuration (only one specimen contain top angle in concrete slab) were designed and tested. The joint specimens were designed by considering the effects of top angles, longitudinal reinforcement bars and arrangement of bolts. The behavior of the joints was carefully investigated, in terms of the failure modes, slippage, backbone curves, strength degradation, and energy dissipation abilities. It was found that the slippage between top-and-seat angles and beam flange, web angle and beam web led to a notable pinching effect, in addition, the ability of the energy dissipation was significantly reduced. The effect of anchored beams on the behavior of the joints was limited due to premature failure in concrete, the concrete slab that closes to the column flange and upper flange of beam plays an significant role when the joint subjected to the sagging moment. It is demonstrated that the ductility of the joints was significantly improved by the staggered bolts and welded longitudinal reinforcement bars.

AN ASSESSMENT OF THE EFFECT OF CONSTRUCTION ERRORS DURING THE IMPLEMENTATION OF RC T-BEAMS

This paper investigates the effects of construction errors during the implementation of reinforced concrete T-beams. These errors are classified into two main sections. The first focuses on the position and ratio of reinforcing bars, while the other is related to the concrete strength. A total of ten specimens of T-beams were tested to assess the effect of the possible defects in the construction sites, viz. impact of misplacement of slab reinforcement, irregular arrangement of slab reinforcement, the change in bar diameter of slab reinforcement and the effect of casting method of concrete on the structural behavior of T-beam sections. The results indicated that the faulty placement of slab reinforcement leads to a lower bending moment capacity of the slab (brittle behavior) and the steel strain of slab decreases as the height of slab reinforcement decreases. The irregularity of the reinforcing bars in concrete slab affects the ultimate load carrying capacity of the slab. Also, it was found out that well-arranged distribution of reinforcement improves the ductile behavior of the slab and reduces the corresponding deflections.

Behavior and strength of hidden Rc beams embedded in slabs

Reinforced concrete (RC) beams protrude from the ceiling, unless there is an infill wall beneath. Sometimes the construction of these beams is avoided due to aesthetic concerns, and instead a reinforcement arrangement with an equivalent bending moment capacity in the slab is made; this is named as a hidden beam. However, since such a design based only on strength can change the behavior to a great extent, the drawbacks of hidden beams were experimentally investigated. A total of fourteen half-scale specimens, including conventional T-beams and slabs with identical flexural capacities (hidden beams), were tested to failure under four-point loading. Reinforcement ratio and slab thickness were adopted as test parameters. The results indicated that hidden beams were able to achieve reference strengths after excessive (up to eight times larger) deformations, or they occasionally could never achieve these capacities. Experimental data were also compared with analytical deflection approaches.

Strengthening of Traditional Mud Houses on Response to Earthquake

Earthquake is an unexpected natural disaster that is unforeseeable and several earthquakes have been faced in Bangladesh with a magnitude of more than 6 in Richter scale in recent years. Non engineered houses are very common in rural area. Mudhouse is a typical house pattern among the non-engineered houses. The earthquake effect in conventional mud houses is a great concern. These houses are susceptible to earthquake damage due to some attributes of materials consisting of less stiffness, brittleness and poor bonding between the units. The present study deals with the strengthening of such houses using timber reinforcement with definite proportion contemplating the mud wall sizes and strengthening the walls by allowing some additional materials as reinforcements. Arrangements of reinforcement were followed in such a way that they would not require skilled labour and much cost. A finite element application STAAD-Pro was adopted to execute the required analysis of unreinforced and reinforced models considering both single story and double story. A series of analyses incorporating linear static and linear dynamic analyses were conducted to comprehend the actual response of models. Investigations from analyses depict that timber reinforcements impart greater stiffness and strength against overturning which increases the frequency of the structure and diminishes the lateral displacements to a good extent. The output from analyses includes lateral displacements, frequency, time-dependent displacements and time-dependent acceleration which depict the positive behaviour of reinforced mud houses. Such an arrangement of reinforcement can be a good choice to subside the detrimental effect of the earthquake.

PREDICTING THE FLEXURAL RESPONSE OF A REINFORCED CONCRETE BEAM USING THE FRACTURE-PLASTIC MODEL

This paper describes an attempt to predict the flexural response of a reinforced concrete (RC) beam using nonlinear finite element analysis. To facilitate direct comparison, the beam was tested experimentally under four-point bending with the load increased monotonically. The load-deflection response, crack pattern and failure mode were observed in the experiment. Analysis incorporating the application of ATENA 3D was performed using the fracture-plastic model which is based on the classical orthotropic smeared crack formulation and crack band model. The applicability of this model was demonstrated through detailed simulation of RC beam with identical geometry, reinforcement arrangement, and material properties. From this study, it is found that the overall predicted responses are in very good agreement to those obtained from the experiment. It is also found that the feature in ATENA enables the presentation of reasonably maximum principal strains of concrete and rebar elements which can, therefore, be associated with the predicted crack bands.

The Influence of the Height of Fiber Reinforcement Zone on the Crack Resistance of Rubcon Beams with Mixed Reinforcement

In order to research on the influence of the height of the fiber reinforcement zone on the normal sections crack resistance, we produced and tested rubcon beams of rectangular cross section with mixed reinforcement; our studies showed that the height of the fiber reinforcement zone has a similar effect on the normal sections crack resistance with the percentage of longitudinal reinforcement. It is important to note that the arrangement of fiber reinforcement at 3/4 of the section height greatly complicates the process of manufacturing the beam while not increasing the strength of the tensile zone compared to the beams with the location of the fiber over the entire height of the section.

Experimental and Numerical Assessment of Reinforced Concrete Beams with Disturbed Depth

This paper investigates numerically and experimentally the performance of reinforced concrete (RC) beam with unequal depths subjected to combined bending and shear. Such beams can geometrically be considered for unleveled reinforced concrete (RC) floor slab-beam system. However, it may generate critical disturbances in stress flow at the re-entrant corner (i.e. location of drop in beam depth). This research investigates the use of shear reinforcement and geometric properties to enhance cracking characteristics, yielding, ultimate load-carrying capacity, and exhibiting ductile failure mode. Ten reinforced concrete (RC) beams were constructed and tested experimentally considering the following key parameters: recess length, depth of smaller beam nib, and amount and layout of shear reinforcement at re-entrant corner. Finite element analysis (FEA) with material non-linearity was conducted in two RC beams that were tested experimentally to validate the computer modelling. The FEA models were then extended to conduct a parametric study to investigate the influence of geometric parameters (beam shape and width) and amount and arrangement of shear reinforcement on the structural response. Results confirmed that geometric properties and ratio of shear reinforcement at the re-entrant region significantly affect the behavior of reinforced concrete beam with unequal depths in terms of first cracking, yielding level, ultimate load carrying capacity and mode of failure.

Strengthening of Reinforced Concrete Continuous Beams using GFRP

This research paper gives the behaviour of reinforced concrete continuous beams under static loading by externally bonding with GFRP sheets. A standard two span continuous beams of size (300×300×2500)mm were casted. Reference beam with no external bonding is prepared to compare the values. Identical reinforcement arrangement is done for all beams. RC beams are tested for failure, load capacity and deflection analysis. Test results are compared for reference and GFRP bonded beams.

Local strengthening of anchorages with post-installed (supplementary) reinforcement

The existing anchorages in reinforced concrete structures may need strengthening due to an increase in the applied load during its lifetime. In certain cases, due to limited dimensions of the structural member (e.g. concrete slab or beam), the size of the anchorages that can be used is also limited and the standard design of anchorages may not be enough to provide required load-carrying capacity. In these above-mentioned cases, a method to strengthen the anchorage may be needed. In the present work, it is attempted to develop a method for strengthening of anchorages under tension loads by using post-installed reinforcing bars. Tests were performed on anchorages using bonded anchors (single anchors) without and with different configurations of post-installed reinforcement for strengthening. The main objectives were to investigate the influence of the reinforcement arrangement on the ultimate load capacity and on the load-displacement behavior of the anchorages. The bonded anchors were selected considering the ease of installation and freedom to choose the test parameters. The tests were performed on anchorages away from the edge. The test parameters were determined in a way that in the case of reference tests, concrete breakout was the dominant failure mode. The reinforcement was placed relatively close (with a distance of approx. 0.4·hef) to the anchor. The results clearly show that the post-installed reinforcement can result in a considerable increase in the load and deformation capacity of the anchorage. Depending on the amount and arrangement of the reinforcement, a change in the failure mode from concrete cone breakout to strut-failure could be observed. It was also shown that for the same amount of reinforcement provided, the arrangement of the reinforcement had a considerable influence on the effectiveness of the strengthening. To understand the mechanics better, in certain tests, strain gauges were applied on the reinforcing bars, which showed the interaction between the contribution of concrete and that of reinforcement in resisting the applied loads.