Configuration Of Transverse Reinforcement Research Articles

Prediction model and sensitivity analysis of ultimate drift ratio for rectangular reinforced concrete columns failed in flexural-shear based on BP-Garson algorithm

Considering that the deformation capacity of reinforced concrete (RC) columns is crucial in performance-based seismic design, the ultimate drift ratio of RC columns failed in flexural-shear are studied using BP neural network and Garson (BP-Garson) algorithm. Firstly, this study employed data onto tests conducted on 35 rectangular RC columns with flexural-shear failure. Nine influencing factors including axial load ratio, shear span ratio, longitudinal reinforcement configuration, transverse reinforcement configuration, and material strength were selected as variables, a BP neural network was used to establish the relationship between the ultimate drift ratio and these variables. Accordingly, a predictive model for the ultimate drift ratio of RC rectangular columns failed in flexural-shear was constructed. Then, the Garson algorithm for local sensitivity analysis was applied to determine the sensitivity of each influence of the ultimate drift ratio of RC rectangular columns failed in flexural-shear. The results showed that the BP neural network could accurately predict the ultimate drift ratio of RC rectangular columns with flexural-shear failure, of which the primary influencing factors are shear span ratio, axial load ratio, volume transverse reinforcement ratio and longitudinal reinforcement ratio. The BP-Garson algorithm integrates model development with influence analysis, which could improve computational efficiency and serves as a reference for evaluating the sensitivity of seismic performance and its influencing factors in other structural components.

Experimental study on longitudinal shear behavior of prefabricated steel-concrete composite beams with notched connections

To address the fit-up issues caused by the interference between shear connectors and extended transverse bars, a novel deck-to-girder connection detail, notched connection, is applied to steel-concrete composite bridges with partial-depth deck panel (PDDP) systems. In the novel joint detail, protruding transverse reinforcement is replaced by evenly distributed notches at the ends of precast panels, and tie bars inserted in the notches are anticipated to resist longitudinal shear stress, achieving shear connection between steel girders and precast deck slabs. Considering the discontinuity of bottom transverse reinforcement, a four-point bending test was performed to investigate the longitudinal shear behavior of composite beams incorporating notched connections. Experimental findings indicate that the configuration of transverse reinforcement critically influences the failure modes of composite specimens, which involve crushing of concrete slabs, longitudinal shear cracking and splitting. Notably, tie bars sufficiently anchored in notches function equivalently to extended bars spliced by welding, and the specifically designed U-shaped notches enhance the anchorage performance of tie bars. Transverse reinforcing bars placed in the concrete topping prove more effective in resisting longitudinal shear than those in the bottom layer, and therefore asymmetrically reinforced concrete slabs experience reduced longitudinal shear cracking and splitting. Moreover, interface shear reinforcement effectively ensures the full composite action, while concentrated point loads can induce excessive local longitudinal shear stress. The study also provides design recommendations for notched connections.

Quasi-static cyclic behavior of precast high-strength concrete tunnel segments reinforced with GFRP bars

The cyclic behavior of fiber-reinforced polymers (FRP) reinforced precast concrete tunnel lining (PCTL) segments under quasi-static cyclic flexural loading has not yet been experimentally tested and reported on in the literature. This study investigated the cyclic behavior of glass-FRP (GFPR) reinforced precast high-strength concrete (HSC) tunnel lining segments. Full-scale segments measuring 3100 × 1500 × 250 mm were tested under quasi-static cyclic flexural loading. Two cycles of loading and unloading were applied at 1.25%, 2.5%, 5%, 10%, 25%, 50%, and 75% of the maximum displacement obtained from the static testing results, followed by a single cycle up to failure. The test parameters included concrete compressive strength, longitudinal reinforcement ratio and transverse reinforcement configuration (closed ties versus double U-shaped ties). The experimental findings of this study revealed that the GFRP-reinforced HSC PCTL segments exhibited stable hysteretic response until failure. In addition, the test results show that the GFRP-reinforced HSC PCTL segments were able to achieve adequate ductility indexes as well as deformability limits. A theoretical prediction according to the North American codes and design guidelines, including flexural capacities, cracking moment, and crack width, was made and the results compared to the experimental results. This research illustrates the advantages of using HSC for PCTL segments internally reinforced with GFRP bars under quasi-static cyclic flexural conditions.

Numerical Analysis of Torsional Reinforcement of Concrete Beams in Unconventional by ANSYS Software

In this study, a finite element analysis is conducted to study the behaviour of RC beams with different configurations of transverse reinforcement under torsion. These configurations of stirrups are traditional closed stirrups, circular spiral stirrups, and inclined rectangular spiral stirrups. The numerical torsional load values are compared with the experimental torsional load values from previous research. The numerical analysis determined by the ANSYS software shows a reasonable agreement with the experimental torsional load values. The numerical results demonstrate that the use of continuous rectangular spiral stirrups improved the torsional response compared to using another type of beam stirrup. Thus, numerical results show that continuous spiral stirrups are effective at increasing torsional capacity. It is also noted that the behaviour of these beams with continuous spiral stirrups is better than the behaviour of the beams with traditional stirrups. The beams with helical reinforcement, which are TB2, TB3, and TB4 spiral reinforcements, greatly enhanced the toughness. The equivalent stresses are 13.709, 13.728, 14.72, and 15.894 MPa, while the equivalent elastic strains are 0.00421, 0.00377, 0.00347, and 0.00539 mm/mm for the beams TB2, TB3, and TB4, respectively. The beam TB4 had the highest stress and strain value, so its strength improved its ductility properties. As a result, the stirrups' configurations enabled the detection of beam failure mechanisms by improving torsional behaviour when compared to the beam's traditional stirrups. As a result, this research adds more knowledge to the literature on the most effective spiral stirrups for transverse reinforcement to improve the torsional behaviour of beams. Doi: 10.28991/CEJ-2023-09-01-04 Full Text: PDF

Effect of connection transverse reinforcement on the behavior of GFRP-RC T-connections: Numerical investigation

This study numerically investigates the cyclic behavior of glass fiber-reinforced polymer (GFRP) reinforced concrete exterior beam-column (T-BC) connections (GFRP-RC T-BC connections) with varying amounts of transverse reinforcement (TR) in the connection panel. The amount of TR required to provide adequate confinement and shear strength to the GFRP-RC T-BC connections has not yet been fully understood. The primary objective of this study was to evaluate the effects of TR configuration and amount of TR on the load-drift ratio response, strain distributions and shear strength of the GFRP-RC T-BC connections. The numerical investigation was conducted using the numerical models developed in ATENA software and validated against the test results of four T-BC connections (one steel-RC and three GFRP-RC). The TR ratio and TR configurations (2 leg, 3 leg, and 4 leg horizontal stirrups) in the connection panel were the main parameters of the numerical study. Results of the numerical study indicated that increasing the TR ratio in the connection panel to 0.72% significantly enhanced the peak load, stiffness and drift ratio capacity of the GFRP-RC T-BC connection. Four leg TR configuration showed significantly better performance of the GFRP-RC T-BC connections due to the higher confinement factor than the other TR configurations. A shear strength equation was proposed for the GFRP-RC T-BC connections, which represents a linear relationship between shear strength and the TR ratio up to 0.60%, followed by stable shear strength of 0.85fc′ for a TR ratio up to 1.30%.

Cyclic behavior of reinforced concrete columns with five-spiral reinforcement

Multi-spiral transverse reinforcement has been shown to provide superior seismic performance than conventional rectilinear tie reinforcement. This research intends to investigate the flexural behavior of the five-spiral transverse reinforcement configuration for square concrete columns. Large-scale flexure-critical five-spiral columns and counterpart conventional tied columns were tested under low (0.1fca′Ag) and high (0.3fca′Ag) constant axial load and subjected to double-curvature lateral cyclic loading. Test results showed that with 16%–29% less transverse reinforcement, the five-spiral columns displayed superior flexural strength, higher ductility, and larger drift capacities than the counterpart conventional tied columns. The five-spiral columns also showed improvements in the seismic capacity of the column in terms of energy dissipation. Furthermore, it was determined that the nominal moment strength could conservatively compute the actual moment strength of five-spiral columns. However, the five-spiral columns showed a higher flexural overstrength from the nominal moment than the counterpart tied columns. From the existing code methods examined in calculating the expected maximum moment, the Caltrans SDC 2019 method provided the best prediction of the maximum flexural strength of the columns, followed by the AASHTO 2017 method, then the ACI318-19 method. All three methods, however, could not fully capture the superior confinement effect of the five-spiral reinforcement.

Stress–strain model for confined concrete in rectangular columns with corroded transverse reinforcement

Reinforcement corrosion and the configuration of transverse reinforcement have evident influences on the stress–strain relation of confined concrete in rectangular corroded columns, which are not properly considered by current stress–strain models. In this paper, the experimental results of 27 reinforced concrete (RC) rectangular columns with corroded transverse reinforcement were discussed, which revealed that key variables such as corrosion degrees have significant influences on the maximum stress and the corresponding axial strain of specimens. Based on test data and nonlinear regression analyses, empirical equations were proposed to account for the impacts of both reinforcement corrosion and the rectangular shape of transverse reinforcement on three important characteristic parameters of the stress–strain curves, namely the maximum strength, the axial strain at maximum strength and the ultimate strain of confined concrete. Comparisons revealed that the proposed stress–strain model outperformed existing models and demonstrated good agreement with test results.

Experimental research and finite element analysis on seismic behavior of square reinforced concrete columns with four interlocking spirals

The seismic performance of square reinforced concrete columns confined by an innovative transverse reinforcement configuration composed of four interlocking spirals and outer square stirrups were investigated experimentally and numerically. Five composite specimens were tested under quasi-static reverse cyclic loading. The experimental results indicated that compared with conventional single spiral reinforced square composite column (SSRSCC) the newly developed interlocking multi-spiral reinforced square composite column (IMSRSCC) even with a slightly lower volumetric confinement ratio exhibited superior seismic performance in ultimate bearing capacity, energy dissipation and delaying the degradation of strength and stiffness. Moreover, a detailed three-dimensional finite element model considering the bond-slip behavior between concrete and steel reinforcement was developed and validated through a comparison with experimental results. The stress development and confining mechanism of transverse reinforcement of IMSRSCC was explored and the effects of the main design parameters on the seismic performance of IMSRSCC were also discussed through parametric studies.

Mechanical behavior of square composite columns with four interlocking spirals under compression

The compressive capacity of square composite columns confined by four interlocking spirals and outer square stirrups are experimentally and analytically investigated. The proposed innovative transverse reinforcement configuration used for square columns can improve the non-uniform confinement of outer square stirrup and thus enhance the confinement effect for the core concrete. Eight square composite columns for axial compression and ten eccentric compression specimens were tested. The study demonstrated that the newly developed interlocking multi-spiral reinforced square composite column (IMSRSCC) with the same volumetric confinement ratio outperformed conventional single-spiral reinforced square composite columns (SSRSCC) both in terms of ultimate load, bending stiffness and ductility under eccentric compression, while in axial compression test, the proposed new square composite column obtained similar ultimate load and deformation capacity. In addition, a comprehensive parametric study is presented using finite element analysis to explore the confinement working mechanism and key design parameters of IMSRSCC. Moreover, an analytical model is developed considering the composite confinement due to outer square stirrups and interlocking spirals and the formulas for calculating the bearing capacity of IMSRSCC are proposed. The analytical results are found consistent with experimental and numerical data.

Durability assessment and behavior under axial load of circular GFRP-RC piles conditioned in severe simulated marine environment

This study concerns the feasibility of using innovative glass fiber-reinforced polymer (GFRP) bars, spirals, and hoops in constructing sustainable marine reinforced concrete structures. The experimental investigation aimed at assessing the durability and structural performance of GFRP-reinforced concrete (RC) circular piles exposed to two simulated marine environments in the laboratory. A total of 15 GFRP-RC circular piles measuring 304 mm in diameter and 1000 mm in height were longitudinally reinforced with GFRP bars and transversely with GFRP spirals or hoops. Five specimens were fabricated as references (unconditioned). The remaining 10 specimens were continuously immersed in simulated marine environments (conditioned) for 12 months: five were kept in seawater at room temperature (22 °C), while the other five were stored in a large chamber that produced hot waves at high temperature (60 °C). After conditioning, all the specimens were tested under axial compression loads. Two structural variables were considered: the transverse reinforcement configuration (spirals versus hoops) and the confinement level (spiral spacing). The durability assessment included microstructure examinations (i.e., differential scanning calorimetry (DSC) and scanning electron microscopy (SEM)) were performed on GFRP bars and spirals taken from the conditioned piles. Furthermore, the bond between concrete and bars or spirals was checked by optical microscopy (OM). The microanalysis observations indicate no visible damage in the contact surface between concrete and GFRP bars or individual fibers and the resin matrix. The compressive test results pointed out that the GFRP-RC piles subjected to severe marine environments experienced 19% enhancement in their axial capacities compared to their reference counterparts. The GFRP spirals and hoops performed well in severe marine environments. The nominal axial capacities of the columns were predicted with the available design equations and are presented and discussed herein.

Effect of Configuration and Yield Strength of Transverse Reinforcement on Lateral Confinement of RC Columns

In general, the lateral confinement capacity of RC columns is influenced by the strength and configuration of transverse reinforcement. In this study, performed antisymmetric flexural moment experiments that simulated seismic loads, with the configuration and yield strength of the transverse reinforcement of RC square columns as main variables. The eight specimens were square cross-sections measuring 250 × 250 mm, and the lateral confinement effect in relation to main variables was examined by inducing flexural failure in the plastic hinge zone under a shear span-to-depth ratio (a/D) of 3.0. Transverse reinforcements comprised a square and octagonal S-series and tie-based H-series. The yield strengths of the transverse reinforcements were 453 MPa and 1053 MPa, respectively. Compared to the H-series, the S-series, whose configuration of transverse reinforcement is closer to a circular form, exhibited more prominent ductile behavior after flexural yield with increasing yield strength of transverse reinforcement, which indicates greater lateral confinement.

Seismic performance of square concrete columns reinforced with grade 600 MPa longitudinal and transverse reinforcement steel under high axial load

The aim of this paper is to investigate the seismic behavior of square concrete columns reinforced with Grade 600 MPa steel under high axial load and specify the service strength of Grade 600 MPa longitudinal bars. For these purposes, seven high-strength reinforced concrete cantilever columns with high axial compression ratio (0.64) and low aspect ratio (3.3) were constructed and tested under constant axial loading and cyclic lateral loading. A new configuration of transverse reinforcement was proposed and applied in these specimens. The main variables carried out in the current experiment include longitudinal bars ratio, transverse reinforcing strength, and the spacing of transverse bars. The milestone behaviors of these specimens were estimated and interpreted using multiple performance indexes, including failure pattern, hysteresis response, strength capacity, flexural ductility, energy dissipation capacity, strength degradation, and stiffness deterioration. Test results indicated that these specimens can be satisfied with aseismic requirement of Chinese code GB 50011-2010. Based on the strain of longitudinal bars test results, the service strength of Grade 600 MPa longitudinal bars can be specified as 560 MPa in this study. An added design suggestion is proposed with the amount of transverse reinforcement requirement to ensure seismic performance of these columns using the effective confinement index (keρshfyh/fc’). A fiber section analysis program was conducted in XTRACT finite element software. The analysis show that the failure mode of specimens was transformed with a given high axial compression ratio when the confinement effect of core concrete was considered. The method of the China Concrete Code (GB50010-2010) for determining seismic bending moment capacity of RC column was extended on the basic of confined concrete theory. Compared with experimental results, the conservative calculation results were obtained in this manuscript. It could be referenced for engineering seismic design.

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.

Torsional capacity investigation of reinforced concrete beams with different configurations of welded and unwelded transverse reinforcement

AbstractAn experimental study is carried out to test 25 reinforced concrete (RC) beams in order to investigate the torsional behavior of the beams using welded and unwelded transverse reinforcement. Four different transverse reinforcement configurations were considered: ordinary, continuous circular spiral, continuous rectangular spiral, and continuous advanced rectangular spiral configuration. Welded configuration includes welding the hoops to the longitudinal reinforcement at their intersections. Three different spacing of 200, 150, and 100 mm were used. The experimental torsional capacity results are compared with the theoretical values determined by the ACI 318–14 code, Eurocode‐2, fib model code2010 and other available equations in the literature. The results showed that the welding effect varies based on the transverse reinforcement configuration and spacing and the maximum improvement in the ultimate torsional capacity of RC beams is obtained in the specimens made with continuous circular spiral stirrups. Furthermore, the ACI‐318, Eurocode‐2, fib model code2010 and other equations available in the literature are generally conservative in predicting the ultimate torsional strength of welded and unwelded RC beams with continuous transverse reinforcement but the predicted torsion moments obtained using Eurocode‐2 and fib model code2010 are closer to the test results.

Internal transverse reinforcement configuration effect of EB/NSE-FRCM shear strengthening of RC deep beams

This paper presents an experimental study carried out on the structural performance of shear-critical reinforced concrete (RC) deep beams internally reinforced with two different stirrups configurations; i.e. aligned and unaligned with the fabric-reinforced cementitious matrix (FRCM) strips. The test matrix involved two unstrengthened (reference) beams and twelve strengthened deep beams tested under three-point bending. Three test variables were investigated: (a) the configuration of the internal transverse reinforcement (ITR), (b) the type of FRCM fabric (carbon, glass, and polyparaphenylene benzobisoxazole, PBO), and (c) the strengthening technique (externally bonded, EB, and near-surface embedded, NSE). Experimental results demonstrated an effective application of the FRCM in improving the load capacities (Pmax) of deep beams; however, its performance depends on the test variables. The NSE-FRCM provided an inherent anchorage that prevented the premature debonding of the FRCM composite, which was a standard failure mode in the externally bonded FRCM strengthened beams. Finally, a simple strut and tie model (STM) is used to predict the load capacities of the deep beams strengthened with different FRCM systems and resulted in a satisfactory prediction with an average Pth/Pex ratio of 1.11 and a standard deviation of 5.7%.

Analytical compressive stress–strain model for concrete confined with high‐strength multiple‐tied‐spiral transverse reinforcement

SummaryThe behavior of reinforced concrete members subjected to seismic loads is mainly based on the ultimate strength of concrete and its ductility. Based on this, an additional configuration of transverse reinforcement using high‐strength multiple‐tied‐spiral was proposed to improve the strength and ductility of concrete. In this paper, an experimental study of a number of axial loading tests on reinforced concrete columns confined with high‐strength multiple‐tied‐spiral transverse reinforcement is described. The effects of spacing of circular spiral and rectangular hoop, the confined area of circular spiral and concrete strength on axial behavior of confined concrete were investigated. The formulas of confined compressive strength and corresponding axial strain, factor to control the slope of descending branch, and stress in high‐strength circular spiral at confined strength are proposed based on the test results. A stress–strain model is also proposed that is found to give reasonably good prediction of the experimental behavior of reinforced concrete (RC) columns confined by high‐strength multiple‐tied‐spiral transverse reinforcement.

Mixed model for the analytical determination of critical buckling load of passive reinforcement in compressed RC and FRC elements under monotonic loading

Compressed reinforcements on reinforced concrete (RC) and steel fibre reinforced concrete (SFRC) columns are generally submitted to cyclic and monotonic loading, which can buckle. This phenomenon can cause the reduction of both ductility and peak loads, which is why design standards propose constructive details to avoid this. Although the bibliography mentions that steel fibres in concrete can delay buckling of reinforcements, design codes do not distinguish between concrete types (with and without fibres) in these constructive details. Analytical models that determine the length and critical buckling stress of reinforcements may consider this effect. Nowadays, analytical models can be classified as discrete and distributed depending on whether they consider transverse reinforcement stiffness and the stiffness of the concrete cover that concentrates on transverse reinforcements, or if they are distributed along the element, respectively. Both discrete and distributed models are valid for small transverse reinforcement separations, while distributed models that only consider the concrete cover effect are valid for large transverse reinforcement separations.This paper proposes a mixed model to determine critical buckling loads of compressed reinforcements subjected to monotonic loading to use the stress-strain relationships of reinforcing bars, including buckling, that are found in the scientific-technical literature. This model considers transverse reinforcements discretely and concrete cover distributedly. The model can be applied to any transverse reinforcement configuration, and to any concrete type (with or without fibres). An analytical equation is also proposed to determine critical compressed reinforcement loads, whose result is presented as abaci. Finally, to calibrate the model in normal-strength concrete columns under eccentric loading, with or without fibres, a programme is presented in which the critical load of longitudinal reinforcements is experimentally determined. The proposed analytical model is calibrated and a procedure to determine critical buckling loads of compressed reinforcements under monotonic loading is proposed.

Finite Element Analysis of Square RC Columns Confined by Different Configurations of Transverse Reinforcement

Introduction:Square reinforced concrete (RC) columns with the confinement effect of transverse reinforcement perform well in ductility and have been used widely in RC structures. Its behavior is the classic topic of anti-seismic and anti-collapse analysis of RC structures. With the advancement of the finite element (FE) analysis technology, the general-purpose simulation tools such as ABAQUS and ANSYS have been universally used to analyze the behavior of structures and members, where the material constitutive model is a key problem in the analysis.Methods:In this study, a new uniaxial compressive stress-strain curve of the confined concrete considering confinement effect of transverse reinforcement in square RC columns was proposed for the concrete damaged plasticity model in ABAQUS to solve the problem that there is no proper uniaxial compressive stress-strain curve for the concrete damaged plasticity model to describe the behavior of concrete confined by transverse reinforcement. Based on the proposed stress-strain relationship, a FE model was developed to analyze the behaviour of laterally confined RC columns under concentric loading.Results:The finite element model is able to predict the response of the confined RC columns from different experiments with reasonable accuracy. Finally, a parametric study was conducted in order to evaluate the effect of confinement reinforcement configuration on the behavior of core concrete in square section.

Axial compressive behaviour of RC columns with high-strength MTS transverse reinforcement

To improve the mechanical behaviour of reinforced concrete (RC) columns with square cross-section, an additional configuration of transverse reinforcement using high-strength multiple-tied spirals is proposed to achieve better lateral confinement to the concrete and to delay or avoid the buckling of longitudinal bars. In total, 12 specimens are designed for the axial compression test, including ten RC columns with high-strength multiple-tied-spiral transverse reinforcement (MTSTR) and two RC columns with conventional stirrups to provide a reference. The variables of specimens in the experiment are the spacing of circular spirals and rectangular hoops, the confined area of circular spirals and concrete strength. The experimental results indicate that the concrete and the longitudinal bars are effectively confined by the high-strength MTSTR, leading to considerable enhancements in both the load-carrying capacity and ductility of RC columns. On the basis of strain compatibility, an analytical approach to the axial behaviour of the RC column with high-strength MTSTR is proposed, and the analytical results using the model proposed by Bing and co-workers agree well with the experimental results.

Effect of Concrete Types and Construction Joints on Concrete Shear Friction Characteristics

The present study examined the effect of smooth construction joint and concrete unit weight on the shear friction behavior of concrete. From nine push-off test specimens, shear load-relative slip relationships, shear cracking stress, shear friction strength were measured. Test results showed that the shear cracking stress was hardly affected by the configuration of transverse reinforcement or concrete unit weight. The shear friction strength of monolithic normal-weight concrete was approximately three times higher than that of the companion specimens with construction joint. Meanwhile, the heavyweight concrete joints had a similar shear friction strength to normal-weight concrete ones.