Shear Transfer Strength Research Articles

Evaluation of the interface shear strength of concrete containing treated and untreated reclaimed asphalt pavement aggregates

Concrete production significantly contributes to carbon emissions and depletes natural resources, promoting increased interest in substituting traditional materials with recycled alternatives. This shift necessitates a thorough examination of recycled materials’ performance in concrete applications. This study aims to provide a better understanding of the shear transfer behavior of concrete containing reclaimed asphalt pavement (RAP) aggregates. To mitigate the potential negative impact of RAP aggregates, mechanical treatment was applied. The effects of RAP inclusion and mechanical treatment on the shear transfer strength of reinforced concrete were investigated. A total of twenty-four push-off specimens were tested to investigate the effects of aggregate replacement and the clamping reinforcement ratio on specimen behavior. Digital image correlation (DIC) was employed to monitor the strains and displacements, allowing for detailed tracking of the interface slip, crack width development, and reinforcement strain. The findings revealed that replacing natural aggregates with RAP aggregates resulted in lower compressive strengths and lower ultimate push-off strengths of the resulting concrete at equivalent effective water-to-cement (w/c) ratios. Specimens with higher reinforcement ratios retained residual strengths up to 77 % of the ultimate strength, even at relatively large slip and crack widths. The clamping reinforcement ratio was identified as the key factor influencing the ultimate and residual strengths for both types of concrete. The experimental results were compared to the strengths calculated by the ACI, PCI, AASHTO, and CSA design equations to evaluate their applicability when different aggregate types are used.

Shear transfer strength of alkali-activated slag-based concrete

As a part of ongoing research to apply alkali-activated slag-based concrete in building structures, the shear transfer behavior of alkali-activated slag-based concrete was experimentally examined through the push-off tests of 32 initially uncracked reinforced planes. The test parameters were concrete type, concrete strength, shear reinforcement ratio, and shear plane size. The test results and comparative analysis showed that the shear strength of reinforced alkali-activated slag-based concrete (AAC) was comparable to Portland cement concrete (PCC) counterparts. However, AAC planes cracked earlier and displayed larger crack separation at the peak load, which is attributed to higher cracking prevalence and brittleness of AAC. Both the increase of concrete strength and lateral constraint stress promotes the development of shear strength in reinforced planes, and their effect is interactional. The shear strength decreased as the shear plane width and depth increased. The existing strength models from design codes and literatures for the shear transfer strength of PCC are still applicable to reinforced AAC planes. Among them, AASHTO LRFD Bridge Design Specifications and the nonlinear model proposed by Mau and Hsu gave better predictions of the measured shear strengths of AAC.

Shear transfer strength estimation of concrete elements using generalized artificial neural network models

Abstract Based on published test findings, this article outlines the use of artificial neural networks (ANNs) to forecast the efficiency factor of shear transfer strength in concrete. Backpropagation neural networks with feed-forward have been employed. The ANN model was created by incorporating a huge experimental database and carefully selecting the architecture and training procedure. The presented ANN model offered a more accurate tool to compute R (where R is a measure of the closeness of association of the points in a scatterplot to a linear regression line based on those points) and capture the impacts of five primary parameters: concrete compressive strength, steel reinforcement ratio, steel yield strength, fiber volumetric ration, and steel fiber aspect ratio are given from experimental data. The obtained results reveal that the first important parameter is concrete compressive strength. In addition, ρ y f y parameter represents the normalized tensile force in steel reinforcements of section, whereas the smallest importance parameter L/D is aspect ratio of steel fibers. Also, the current study illustrated the facilities of using generalized artificial neural networks on predicting the shear transfer strength across the concrete sections, whether they are fibrous or not. From the results, the correlation factor (R 2) is estimated to be about 83%, which means it had a good correlation within the input parameters. In addition, the mean absolute percentage error was 2.06.

Evaluation of interface shear transfer strength of steel fiber‐reinforced concrete based on artificial neural network and regression method

AbstractTransfer of shear strength across the concrete‐to‐concrete interface is important to the strength of reinforcement concrete structures and is extensively existing in repairing and strengthening existing reinforced concrete members, the connections between prefabricated members and the connection joints between concrete sections cast in situ. Steel fibers improve the mechanical properties of concrete and steel fiber‐reinforced concrete (SFRC) has been universally applied as the repaired materials and the connection materials in reinforced concrete structures. The aim of this paper is to evaluate the interface shear transfer (IST) strength of SFRC. One hundred twenty‐seven‐group experimental results are collected from previous studies to establish a reliable database, which the investigated parameters include the compressive strength of concrete, the diameter, length and volume friction of steel fibers, and the volumetric ratio and yield strength of shear reinforcement. Based on the established database, an artificial neural network (ANN) model is developed and the parameters sensitive is analyzed based on the proposed ANN model. Based on the parametric sensitive analysis, the linear regression model is established to evaluate the IST strength of SFRC, which is applied to evaluate the design of the concrete‐to‐concrete connections.

Machine-learning-based models to predict shear transfer strength of concrete joints

In predicting the shear transfer strength (STS) of concrete joints, numerous design parameters need to be considered due to diverse application scenarios and various construction materials. Existing mechanical-based models were established only based on limited data or for a specific scenario, leading to their insufficient prediction capability for STS of concrete joints. This research aims to develop a more accurate, stable, and reliable prediction model for STS of concrete joints based on machine learning technology. A database of 512 test results was assembled for the STS of concrete joints. Two machining learning models, the support vector regression (SVR) model and the random forest regression (RFR) model, were determined by a customized training procedure. A new feature selection method was proposed to sort input parameters based on a combined weight value representing influence intensity. The two optimized machine-learning-based models were experimentally evaluated, and further compared with common mechanical-based models through a series of performance indicators. A parameter study was conducted on the most influential parameters using the mechanical-based and machine-learning-based models. Results show that the SVR and RFR models are experimentally verified to be more accurate, stable, and reliable compared with the mechanical-based models. Concrete compressive strength, stirrup contribution, cohesion-related parameter, and fiber volume are recognized to be the most influential for STS of concrete joints, which agree with common mechanical-based models. Parameters like height of the shear plane, height of the top support of the joints, width of the joints, maximum aggregate size, longitudinal bar contribution at the shear plane are also detected to have obvious effects on the STS but are not considered in most of the mechanical-based models. Compared with the RFR model, the SVR model is more recommended for the prediction of STS due to better consistency with experimental results.

Investigation of parameters affecting direct shear behavior of concrete strengthened with CFRP laminate

In this paper, the influence of important parameters affecting shear transfer strength and deformation of concrete strengthened externally using CFRP laminate has been investigated. Parameters investigated were the internal steel reinforcement, CFRP layers, existence of preloading, and existence of tension on shear plane. For the latter one, a special type of push-off specimen has been developed, different from those used by the others. This specimen can be named a modified pair push-off specimen and was found to be more convenient compared with the other specimens used. Results showed that there is a relatively high shear strength enhancement of non-reinforced concrete strengthened with CFRP laminate, reaching 91% when two CFRP layers are used for strengthening. Shear enhancement ratio was found to reduce with the increase of the internal steel ratio, of an enhancement between 8% and 29%. Effect of moderate preloading on concrete was found not important on the residual shear strength. There is a good chance to strengthen concrete subjected to shear and tension for shear enhancement between 22% and 157%. A new proposal was developed for the prediction of direct shear capacity of strengthened concrete, essentially depends on an accurate assessment of FRP laminate contribution to enhance shear.

Shear Transfer Strength of Uncracked Concrete after Elevated Temperatures

The shear transfer strength (STS) of uncracked concrete at ambient and after elevated temperatures of 350°C, 550°C, and 750°C is investigated. Forty-eight uncracked push-off specimens with different confinement levels were cast with a constant concrete mix having a target compressive strength of 40 MPa. Specimens were heated at different temperatures in an electric furnace and tested for STS after natural cooling. Results revealed that loss in STS was at its maximum for specimens without transverse reinforcement. An increase in transverse reinforcement resulted in a decrease of loss in STS after exposure to elevated temperatures. Elevated temperatures resulted in the reduction of stiffness of the shear stress-crack deformation curves and also increased the crack deformation corresponding to peak shear stress. An equation for the prediction of STS after elevated temperature is also suggested from the experimental results and validated on the specimens reported in the literature.

Effect of steel fiber on the shear transfer strength across a crack in reactive powder concrete

In structural concrete members that have geometrical discontinuities, the type of failure is called direct shear failure when there is no; the same member may change its response when the load arrangement is changed. This kind of failure is related to the cracks along the plane where the loaded member slides along the stationary support system and cracks are perpendicular to the axis of the member. Numerical analysis on push-off specimens were conducted in this study to investigate the shear strength in reactive powder concrete, which has cementitious compositions. The validation of the material and geometrical model to check the efficiency of the constitutive model to simulate the behavior of shear strength of RPC was achieved through comparison with the experimental result of previous work. The effects of volume fraction, aspect ratio, shape of steel fibers on the shear strength were considered to be the variables of the study. The data analyzed showed that the increase in volume fraction of steel fiber from 0% to 0.5% resulted in an increase in the shear strength of RPC by 40.3%, while, an increase in the volume fraction of steel fiber from 0% to 1.5% increased the shear strength of RPC by 140.3%. Using hook ended steel fiber increased the shear strength of RPC by 62.5%. Furthermore, the shear strength of RPC increased by 49.8% when the aspect ratio increased from 75 to 100. The stiffness and ductility of RPC members increased when the volume fraction, aspect ratio increased and provided shape of steel fiber.

High Temperature Effect on Shear Transfer Strength of Steel Fiber Reinforced Self-Compacted Concrete

High Temperature Effect on Shear Transfer Strength of Steel Fiber Reinforced Self-Compacted Concrete

Tests of Residual Shear Transfer Strength of Concrete Exposed to Fire

AbstractReinforced concrete is one of the most widely used structural components about which much scientific research has been conducted; however, some of its characteristics still require further research. The main focus of this study is the effect of direct fire on the shear transfer strength of concrete. It was investigated under several parameters including concrete strength, number of stirrup legs (the steel area across the shear plane), and fire duration. The experimental program involved the testing of two sets (groups) of specimens (12 specimens each) with different concrete strengths. Each set contained specimens of two or four stirrup legs exposed to direct fire from one side (the fire was in an open area to simulate a real-life event) for a duration of one, two, and three hours. The results of the comparison showed the importance of using high-performance concrete (instead of increasing the number of stirrup legs) to resist shear stress for the purpose of safety. A significant reduction in shear strength occurred due to the deterioration of the concrete cover after three hours of direct fire exposure.

Shear transfer strength of uncracked interfaces: A simple analytical model

This paper presents a simple analytical model for the estimation of shear transfer strength (STS) of uncracked (UC) interfaces. Model is based on the combination of cohesion resistance offered by concrete and frictional resistance offered by the reinforcement provided across the interface. Coefficient of friction is derived from the experimental data of pushoff specimens with cracked interfaces. Analysis of one hundred forty eight push-off specimens with cracked interfaces collected from the literature showed that a relationship exists between coefficient of friction and the amount of clamping stress. The derived relationship of coefficient of friction was used to work out a relationship between cohesion and concrete compressive strength using the experimental results of twelve push-off specimens with UC interfaces tested in the present study. The proposed model was compared with the models for UC interfaces available in the literature as well as with the provisions of AASHTO LRFD-14 and CSA A23.3-14. Comparison was made on one hundred seventy five push-off specimens with UC interfaces collected from the literature. Results of the comparative analysis revealed that the proposed model produced uniform and precise results over the entire range of clamping stress.

Horizontal Shear Behaviors of Normal Weight and Lightweight Concrete Composite T-Beams

This paper presents the results of recent research on the interface shear behavior of normal weight and lightweight concrete composite T-beams. In the experimental program 12 beams and necessary control cylinders were tested to provide experimental cases with the variables of interface preparation, clamping stress and lightweight slab concrete strength. Compared with 7 equations developed previously, it has been found that those formulas, especially the ones from current AASHTO and ACI design codes, give a conservative theoretical prediction of horizontal shear capacity of composite T-beams. Based on the experimental results, a more accurate equation was developed to predict the interface shear transfer strength of composite concrete T-beam. By comparing the experimental results of previous beam tests and shear-friction push-off tests for different types of concrete with both rough and smooth interface published in literature, it has been found that the proposed formula is reliable in predicting the horizontal shear strength of concrete composite T-beams.

Interface shear behavior between high-strength precast girders and lightweight cast-in-place slabs

The overall purpose of this study is to examine the shear-friction behavior of shear interface with transverse reinforcement between precast girder using high-strength concrete and cast-in-place slab with lightweight concrete. Eighteen push-off specimens, with testing parameters of lightweight coarse aggregate size, slab concrete type and shear reinforcement ratio, were tested in this investigation. Based on the analysis of the experiment, this study suggests that the granular size of lightweight coarse aggregate did not play a significant role in the shear strength of interface and the shear transfer strength of lightweight slab concrete specimens are greater than that of normal weight slab concrete specimens having the same concrete compressive strength, interface reinforcement ratio and interface treatment. Additional, the transfer reinforcing steel can improve shear capacity and residual resistance obviously. For both sand-lightweight and normal weight cast-in-place slab concretes, the interface shear strengths predicted by the design equations given in AASHTO LRFD 2014 and ACI 318-14 are conservative.

Finite Element Analysis of Shear Transfer Strength of SFRC Models

Finite Element Analysis of Shear Transfer Strength of SFRC Models

Shear transfer strength of normal and high-strength recycled aggregate concrete – An experimental investigation

Initially uncracked push-off specimens were tested to investigate shear transfer in recycled aggregate concrete with concrete grade, normal force and the replacement level of recycled aggregates being the variables. A marginal increase in normalized shear strength was noted when the natural coarse aggregates were replaced with the recycled aggregates. Normal force and concrete grade had the most significant effect on the measured strengths and predictions obtained from modified Zia failure criterion were in good agreement with the experimental results of the natural as well as the recycled aggregate concretes. Selected shear strength models in the literature have been reviewed for their predictive efficacy and in the context of design, the PCI code gave reasonably accurate and conservative predictions of the measured shear strengths of both the concrete types.

Effect of joint interface conditions on shear transfer behavior of recycled aggregate concrete

In this study, 38 uncracked and cold-joint push-off specimens were tested to explore how joint interface characteristics affect shear transfer behavior of recycled aggregate concrete (RAC). The major test variables included the recycled coarse aggregate (RCA) replacement ratio and joint interfaces. The results indicate that the shear transfer behavior of RAC with different joint interfaces is similar to that of conventional concrete. It was shown that the RCA replacement ratio has some effect on the ultimate shear transfer strength. The joint interface has great influence on the shear transfer behavior of RAC. Aggregate interlock, bond, and doweling action are aspects of the joint surface condition that effect shear transfer. The RCA replacement ratio negatively affects the aggregate interlock action of RAC. This paper demonstrates that design equations in ACI and PCI codes are conservative and effective for predicting the shear stress in RAC specimens with uncracked or cold-joint interfaces.

강섬유 보강 초고성능 콘크리트의 전단 전달 모델

Ultra High Performance Fiber Reinforced Concrete (UHPFRC) has a outstanding tensile hardening behaviour after a crack develops, which gives ductility to structures. Existing shear strength model for fiber reinforced concrete is entirely based on crack opening behavior(mode I) which comes from flexural-shear failure, not considering shear-slip behavior(mode II). To find out the mode I and mode II behavior on a crack in UHPFRC simultaneously, maximum shear strength of cracked UHPFRC is investigated from twenty-four push-off test results. The shear stress on a crack is derived as variable of initial crack width and fiber volume ratio. Test results show that shear slippage is proportional to crack opening, which leads to relationship between shear transfer strength and crack width. Based on the test results a hypothesis is proposed for the physical mechanics of shear transfer in UHPFRC by tensile hardening behavior in stead of aggregate interlocking in reinforced concrete. Shear transfer strength based on tensile hardening behavior in UHPFRC is suggested and this suggestion was verified by comparing direct tensile test results and push-off test results.

Shear transfer across a crack in recycled aggregate concrete

In this paper, 32 pre-cracked recycled aggregate concrete (RAC) push-off specimens made from 10 mix designs were tested to study the shear transfer performance across cracks. The effects of recycled coarse aggregate (RCA) replacement ratio, the water to cement ratio, the concrete strength, and the lateral constraint on the shear transfer performance were carefully investigated. The experimental results and data analysis show that the shear transfer mechanism and process across cracks in RAC is largely the same as that in natural aggregate concrete (NAC). Both the lateral constraint and the concrete compressive strength positively affect the shear transfer strength of the RAC. However, the RCA replacement ratio has adverse effects on the shear transfer strength when it is over 30%. It is also found that the design equations for NAC in ACI and PCI codes may be used to predict the shear transfer strength of RAC.

Shear transfer in lightweight concrete

This research studied the shear transfer in lightweight aggregate concrete and foam concrete. Fourteen series of pre-cracked push-off specimens, made with different concrete strengths were tested. The effects of concrete strength and shear reinforcement parameters on shear transfer behaviour, including shear transfer strength, were analysed. Almost all the specimens failed as a result of slippage along the shear plane. Together with experimental results obtained from a literature review, general formulas for shear transfer strength for reinforced lightweight concrete are also proposed.

Shear transfer in fibre-reinforced lightweight concrete

This research studied the shear transfer in fibre-reinforced lightweight concrete. Tests were carried out on nine series of initially cracked push-off specimens to assess the effectiveness of steel fibres in combination with continuous bar reinforcement in enhancing the shear transfer behaviour. The major parameters included compressive strength of concrete, volume fraction of fibres and the number of continuous bar reinforcements across the shear plane. Two general formulas for shear transfer strength of fibre-reinforced lightweight concrete are also proposed.