Web Reinforcement Research Articles

Resultados experimentais e análise de carga limite pelo Método de Bielas e Tirantes (MBT) de vigas-parede com entalhes e aberturas

Abstract This article presents experimental results of eight non-aligned, non-geometrically symmetrical deep beams with notches and openings. The variables considered in the study were the presence of web reinforcement, and the geometry of the deep beams. Along with the experimental investigation, a study of strut-and-tie models (STM) representing the behavior (failure mode and maximum load) of reinforced concrete deep beams with complex geometries was performed. The experimental results showed that the ultimate load capacity of deep beams is significantly affected by the presence of reinforcement in the web. Furthermore, the study showed that the STM is conservative and tends to underestimate the results, reducing its ability to predict failure load.

Importance of Web Reinforcement in Beam Column Joint Connections

The primary focus of this research is to determine the optimal stirrup configuration to prevent shear failure. This project aims to investigate the behavior of beam-column joint frames under concentrated loads. Specimens with dimensions of 700mm x 500mm and cross-sectional dimensions of 200mm x 100mm, using M30 Grade concrete, were prepared for this study. The specimen was tested in the linear, non-linear range and up to ultimate load limit for a concentrated load. The load responses are measured with LVDT & Data logger in this experimental work. The code of practice recommends (Bureau of Indian standards-13920-1993) the bond, shear, and ductility, reinforcement for shear and moment carrying capacity. This code aims to fulfill both bond and shear requirements. This paper provides a thorough review and offers recommendations on the design and detailing of beam-column joint connections. Analytical value of the load carrying capacity of the beam column joint was assessed using limit state method by eliminating the partial safety factors for the load and strength. The results were compared between experiments and analytical values and suggestions are presented in this paper.

Experimental study on eccentric compressive behavior of precast concrete double-faced superposed shear walls

With the growing application of prefabricated building structural systems, precast concrete double-faced superposed shear wall (PCDSSW) structures have gained increasing popularity in multi-story and high-rise buildings. However, limited research on the eccentric compressive performance of PCDSSWs could lead to severe consequences. To address this issue, this study conducted eccentric load tests on seven full-scale PCDSSW specimens with steel truss connectors and one full-scale cast-in-place reference specimen. The influence of various design parameters, including truss web diameter, trusses layout, connection locations and methods between steel trusses and distribution reinforcement on the eccentric compressive performance of PCDSSWs was analyzed and discussed. The results revealed that both cast-in-place and PCDSSW specimens exhibited similar failure modes characterized by large eccentric compression failure. PCDSSW specimens showed no noticeable laminated interface separation and can achieve the design objective of "comparable performance to cast-in-place". Moreover, the diameter of truss web reinforcement and the layout of steel trusses had minimal impact on the eccentric compression performance of PCDSSW. While employing welded connections could boost the load-bearing capacity and cracking stiffness of PCDSSW, it also led to a marginally faster stiffness degradation rate and reduced deformation capacity. Additionally, the existing design standards yield conservative predictions for the load-bearing capacity of PCDSSWs. Furthermore, the model proposed by GB 50010–2010 is advocated due to its reliability and accuracy.

Shear Bearing Capacity of Steel-Fiber-Reinforced Concrete Shear Wall under Low-Cycle Repeated Loading Based on the Softened Strut-and-Tie Model

In this paper, the loading mechanism of steel-fiber-reinforced concrete (SFRC) shear wall (SW) under low-cycle repeated loading is analyzed, and the softened strut-and-tie model (SSTM) of SFRC SW composed of horizontal and vertical resistant members and diagonal strut is proposed, in which the contributions of distributed web reinforcement, concrete, and steel fiber (SF) to the shear bearing capacity (SBC) of SFRC SW is identified. Furthermore, a new algorithm to obtain the SBC of SFRC SW is established, and then it is validated by using the test results of steel-fiber-reinforced high-strength concrete (SFHSC) SW and SFRC SW under low-cycle repeated loading. The results show that the calculated values are in good agreement with the experimental values for the 11 SFRC SWs, and the average strength ratio between calculated and experimental values (Vjh,t/Vjh,c) is 0.958. Therefore, the proposed calculation method is scientific and accurate for analyzing and predicting the SBC of SFRC SW. In addition, the proposed calculation method can scientifically and accurately analyze and predict the SBC of SFRC SW.

Structural performance of perforated arched self-compacted reinforced concrete beams under concentrated static loading

Arched reinforced concrete (RC) beams are a viable solution for use as the main supporting system for large-span halls. This is because of the developed normal force owing to the curvature, which approaches the line of pressure under loading, leading to a balance of the resulting bending moment. Therefore, the curved beam can sustain more applied loads than the ordinary straight beam for the same span. However, providing web openings along the entire span of the arched beam can compromise the ultimate capacity. Thus, the behavior of two-hinged perforated arched RC beams made of self-compacting concrete was investigated experimentally and numerically. The experimental program consisted of 11 RC beams, one straight and 10 arched beams, divided into five groups to study the effects of arching, perforation shape and size, and reinforcement configuration around the perforations. In addition, a parametric numerical study using the ABAQUS program was conducted to investigate the relevant parameters in detail. It was found that the arched beam exhibited remarkable ultimate capacity compared to that of the straight beam; however, the strength gains due to the arching effect reduced significantly due to providing web openings. In addition, it was found that providing additional web reinforcement in both the circular and cross-bar configurations around the perforations significantly enhanced the overall behavior. Furthermore, it was found that the best rise-to-span ratio of arched beams was 0.18 for both solid and perforated ones.

Synergistic effects of web reinforcement and hybrid fibres on shear performance of continuous deep beams with unsymmetrical web openings

Application of fibre-reinforced concrete or novel web reinforcement detailing could be an effective way to enhance structural behaviour of continuous deep beams with web openings. However, there are very few experimental works studying the synergistic effects of these two methods. Therefore, an experimental programme is introduced in this paper to study synergistic effects of shear reinforcement and hybrid fibres on shear strength of nine double-span deep beams with unsymmetrical web openings (denoted as pierced span). The test specimens were designed to consist of a pierced beam span with a web opening and an adjacent solid beam span. The spans with openings were designed with different shear reinforcement configurations. It was experimentally shown that provision of sufficient web steels above and below web openings has the most important and beneficial effect on ultimate shear strength of the pierced spans. Besides, a tailored steel reinforcing method was also proposed that is capable of improving strut capacity near the web opening. In addition, adoption of hybrid fibre reinforcement led to enhanced crack-opening resistance, ultimate shear strength and shear deformation. Based on the research outcomes, it was recommended to adopt the proposed detailing method or fibre reinforcement dosage for shear strength enhancement of continuous deep beams with web openings. Furthermore, an analytical model was adopted to the shear strength of continuous deep beams accounting for web openings, steel stirrups, and hybrid fibres, which yielded safe predictions.

A unifying strut-and-tie model for conventionally reinforced link beams

Reinforced concrete link or coupling beams are usually cast integral with wall piers to help them act as a unit to resist lateral loads. The use of deep beam design in ACI 318-19 provisions leads to conservative shear designs for link beams which do not follow Euler-Bernoulli beams. Instead, strut-and-tie systems are used. The paper demonstrates the modeling of such beams using strut-and-tie provisions of ACI 318-19 Ch. 23. Alternatively, to using a time-consuming trial-and-error process, a unified general multi-panel strut-and-tie model is proposed, and simple design equations are developed to directly design conventionally reinforced link beams subjected to high shear force demand. As link beams have often a small span-to-depth ratio, the first one- and two-panel strut-and-tie models are considered basic and common. The one-panel model consists of a direct inclined compression concrete strut with horizontal tension ties in addition to the required crack-control web reinforcement and is used wherever the strut-tie angle is greater than the ACI minimum of 25 degrees; one vertical-to-two horizontal. The two-panel model is used when the beam span is too long to use the one-panel model and consists of one vertical tension tie and two steep inclined compression concrete struts. Worked design examples have been presented to justify and demonstrate the ease of implementation of the considered first two simple and direct models of the proposed unified general multi-panel strut-and-tie model. The predictions of the two basic models have been compared with five sample calculations and the comparison shows a good agreement.

Numerical Analysis of Concrete Deep Beams Reinforced with Glass Fiber-Reinforced Polymer Bars

This research aimed to generate data through a verified numerical model. The data were subsequently used to introduce a simplified analytical expression for the prediction of the shear strength of concrete deep beams reinforced with glass fiber-reinforced polymer (GFRP) reinforcing bars. A three-dimensional (3D) numerical simulation model for a large-scale GFRP-reinforced concrete deep beam (300 × 1200 × 5000 mm) was developed and validated against published experimental data. A parametric study was then conducted to examine the effects of key variables on the behavior and shear strength of GFRP-reinforced concrete deep beams. Eighteen 3D numerical models were developed to study the interaction between the concrete compressive strength (f’c), the shear span-to-depth ratio (a/h), the spacing between web reinforcement (s), and the shear strength. The a/h value was either 1.0 or 1.5. The values of f’c were 28, 37, and 50 MPa. The spacings between the web reinforcement, if present, were 100 and 200 mm. The results of the parametric study indicated that the shear strength of deep beam models increased almost linearly with an increase in f’c and a decrease in the stirrup spacing irrespective of the value of a/h. The strength reduction caused by increasing a/h was more pronounced for the beam models with the lower f’c and greater stirrup spacing. The simplified analytical expression introduced in the present study provided a reasonable prediction for the shear strength of GFRP-reinforced concrete deep beams.

Novel Calculation Method for the Shear Capacity of a UHPC Beam with and without Web Reinforcement.

To accurately predict the shear-bearing capacity of UHPC beams, it is crucial to quantify the shear contribution of the fiber bridging effect and UHPC compression zone. Nevertheless, it should be noted that the shear contribution of UHPC in the compression zone is not fully considered in most existing calculation methods, and the probability distribution of fibers within the matrix is also not taken into full account, which reduces the calculation accuracy of the shear bearing capacity of UHPC beams. In this paper, a UHPC beam shear test database containing 247 samples was created, and the influencing factors on the shear capacity of UHPC beams, such as the shear span ratio, the web reinforcement ratio, and the volume fraction of steel fiber, were analyzed. It was found that the ratio of cracking load to ultimate load ranges from 0.2 to 0.6, and the failure in the compression zone of UHPC beams can be divided into diagonal tension failure and shear compression failure. Based on the failure mechanism of the compression zone, considering the contribution of fiber micro tensile strength, a formula for calculating the shear-bearing capacity of UHPC beams with and without web reinforcement was proposed. Verified by experimental data, the proposed formula accurately predicts the shear-bearing capacity of UHPC beams. In comparison with other shear capacity formulas in current design codes, the proposed formula in this paper provides a higher prediction accuracy.

Parameter optimization for pivot hysteresis model for reinforced concrete walls with different failure modes

AbstractReinforced concrete structural walls are major vertical lateral load‐resisting members in reinforced concrete structures located in seismic regions. It is important to understand and evaluate the hysteresis behavior of these members for an efficient earthquake‐resistant design. Among the various models available for estimating this hysteretic behavior, the Pivot hysteresis model, which models hysteretic behavior through parameters α and β, respectively, representing the unloading stiffness and pinching behavior, has been effective and efficient for use with columns. In this paper, an effort is made to extend the application of the Pivot hysteresis model to reinforced concrete walls. Key variabratiosuch as axial load ratio, wall height‐to‐length ratio, web reinforcement indices, boundary element reinforcement indices, and length‐to‐effective thickness ratio were considered to derive expressions for α and β suitable for walls. Equations for α and β were calibrated through the hysteretic test data of 108 wall specimens subjected to cyclic loading and exhibiting different failure modes. The calibration is based on the optimization of energy dissipation for specimens from the collated database—a numerically complex task achieved through a superior optimization technique known as Simulated Annealing. The proposed formulations showed reasonably good accuracy in predicting complex hysteretic responses when verified against an extensive database of wall test specimens with flexural and shear modes of failure.

Development of Prediction Models for Shear Strength of FRP Reinforced Fibrous Concrete Beams without Stirrups Using ANN and Nonlinear Regression

ABSTRACT The shear behaviour of fibre-reinforced polymer reinforced concrete (FRP-RC) beams without web reinforcement suffers from low strength, low stiffness, more brittleness and wide and quick propagated cracks. Fortunately, the addition of various types of fibres could improve most of these weaknesses. On the other hand, the shear strength prediction of FRP-RC beams with various types of fibres is one of the most complex cases in structural engineering applications. Developing generalised, precise and consistent prediction models are necessary and very limited. This paper investigates the impacts of various types of fibres on shear strength and presents proposing four new prediction models, utilising artificial neural networks and empirical nonlinear regression analysis, and modifying the combination of available models based on a collected database of 49 shear test results of FRP-RC members with various types of fibres. The comparison of the developed models with the available equations from the literature indicates that the developed models yielded excellent performance, great efficiency and a high level of accuracy over all other existing models. Additionally, the parametric study confirmed that all the developed models have great abilities to accurately predict the actual response of each parameter, in spite of its complexity, on the shear strength of FRP-reinforced fibrous concrete beams without stirrups.

Effectiveness of flange plates on torsional behaviors of ultra-high-performance fiber-reinforced concrete hollow beams

This study investigates the effectiveness of flanges with various types of stirrup and cross-sectional dimensions on the torsional behaviors of ultra-high-performance fiber-reinforced concrete (UHPFRC) hollow beams. A finite element model was developed and validated for simulating the torsional behavior. The impact of the essential parameters of flanges was investigated through experimental and numerical methodologies. The results showed that the inclusion of flanges substantially influenced the torsional strength of UHPFRC hollow beams, attributed to the section torsional plastic resistance moment and UHPFRC tensile capacity in flanges. The effectiveness of flange plates was considerably influenced by the web wall thickness. The stirrup type and the increase in flange reinforcement ratio, flange width, and thickness had a favorable effect on the torsional behaviors of thick-walled UHPFRC beams but minimal effect on thin-walled UHPFRC beams. The failure of thin-walled beams was determined by the web thickness and web reinforcements.

SHEAR CAPACITY OF REINFORCED CONCRETE BEAMS WITHOUT SHEAR REINFORCEMENT: A REVIEW

Shear failure in reinforced concrete beams has gained excessive study, particularly beams without stirrups. Because shear failure is considered the most serious due to it occurring suddenly without warning. Because of the seriousness of the matter concerning shear failure, many researchers are looking to use additive materials that differ from traditional concrete constituents in order to improve the shear resistance of the beams, such as the use of silica fume, steel fiber, metakaolin, and many others. The current studies focused on understanding the resistance provided by the interlocking forces between the aggregate and that provided by the non-cracked compression zone, with the use of some materials that are intended to improve the properties of concrete. This paper presents a review of the previous literature that included studying the mechanism and behavior of shear failure of concrete beams without web reinforcement and also includes a presentation of the most important equations used to predict the shear capacity of concrete beams, especially those without stirrups, to understand the mechanism of failure and to know the most important factors affecting the failure of shear.

Strength and Behavior of Glass Fiber-Reinforced Polymer-Reinforced Concrete Box Girders without Web Reinforcement under Pure Torsion

Strength and Behavior of Glass Fiber-Reinforced Polymer-Reinforced Concrete Box Girders without Web Reinforcement under Pure Torsion

Shear behavior of self-consolidating concrete deep beams reinforced with hybrid of steel and GFRP bars

This paper experimentally investigates the dowel action contribution of longitudinal reinforcement, a hybrid of steel and GFRP bars (usually adopted for avoiding corrosion of steel bars), in concrete deep beams for different reinforcement schemes. The self-consolidating concrete without and with steel fibers (0.9 % and 1.2 % by volume) was used. Sixteen simply supported deep beams of 140 × 300 (depth) × 1500 mm were tested under the two-point loads. A model is developed to predict the shear capacity of deep beams without web reinforcement, taking into consideration the dowel action contribution of longitudinal reinforcement, which is a hybrid of steel and GFRP rebars. The results showed a significant dowel action contribution of steel as well as GFRP rebars to beam shear strength. However, the use of a hybrid system of steel and GFRP bars caused a reduction in the dowel action of steel bars due to their combined action.

Experimental Study of the Shear Performance of Combined Concrete-ECC Beams without Web Reinforcement.

Shear damage of beams is typically brittle damage that is significantly more detrimental than flexural damage. Based on the super-high toughness and good crack control ability of engineered cementitious composites (ECC), the shear performance of concrete-ECC beams was investigated by replacing a portion of the concrete in the tensile zone of reinforced concrete beams with ECC and employing high-strength reinforcing bars to design concrete-ECC beams. The purpose of this investigation is to elucidate and clarify the shear performance of concrete-ECC beams. Experimental and FE analyses were conducted on the shear performance of 36 webless reinforced concrete-ECC composite beams with varied concrete strengths, shear-to-span ratios, ECC thicknesses, and interfacial treatments between the layers. The results indicate that the effect of the shear-to-span ratio is greater, the effect of the form of interface treatment is smaller, the effect is weakened after the ECC thickness is greater than 70 mm (i.e., the ratio of the replacement height to section height is approximately 0.35), the shear resistance is reduced when the hoop rate is greater, and the best shear resistance is obtained when the ECC 70 mm thickness and the hoop rate of 0.29% are used together. This study can serve as a technical reference for enhancing the problems of low durability and inadequate fracture control performance of RC beams in shear and as a guide for structural design research.

Size effect tests on shear strength of Basalt FRP-RC deep beams with different shear-span ratios

Basalt Fiber Reinforced Polymer (BFRP) bars appear effective in reducing corrosion-related damage and are gradually used as substitute for Steel bars in engineering practices. However, most of available efforts are focused on the size effect of BFRP-reinforced concrete (BFRP-RC) deep beams without web reinforcement, while less efforts have been studied on BFRP-RC deep beams with web reinforcement. Moreover, the quantitative influence of the shear-span ratio on the shear capacity of BFRP-RC deep beams is always in dispute. The purpose of the work is to investigate the quantitative influence of beam depth and shear-span ratio on the shear behavior of BFRP-RC deep beams with web reinforcement. A total of sixteen specimens were tested by considering the beam depth (i.e., 300 mm ∼ 1200 mm) and the shear-span ratio (i.e., 0.8, 1.3 and 1.8) as test variables. Twelve beams were reinforced with BFRP bars while the other four beams were reinforced with steel bars to act as controls. The corresponding size effect of BFRP-RC deep beams with web reinforcement was quantitatively studied, and the applicability of current design codes and scientific calculation methods were discussed. The results indicate that: 1) the increase of shear-span ratio reduces the nominal ultimate shear strength but has an ignorable influence on the size effect; 2) the nominal ultimate shear strength of BFRP-RC deep beams declinebyabout 46% as the beam depth increases from 300 mm to 1200 mm (both horizontal and vertical web reinforcement ratio are 0.51%); 3) the size effect of FRP-RC deep beams is not reasonably considered in current design codes, while, Jin’s theoretical model can scientificallyreflect the effect of beam depth and shear-span ratio on the nominal shear strength.

Behavior under lateral cyclical load of thin reinforced concrete walls of the industrialized system

Reinforced concrete wall buildings of the industrialized system widely used in Colombia for housing construction in recent years present particular characteristics that make them a research subject. The reduced thicknesses of their walls that give rise to high slenderness ratios, the use of nonductile reinforcement arranged in a single curtain, and the absence or low level of confinement at the ends of the walls are some of the most relevant characteristics. This article presents the results of five quasi-static cyclical tests of thin-reinforced concrete walls (TRCW) on a full-scale, which are representative of the industrialized system. Wall properties were selected from a database of 136 existing buildings. These specimens were built with different cross-sections, lengths, and reinforcement contents at the ends. The experimental results confirm the importance of the properties and amount of web reinforcement and the effect of the use of properly confined boundary elements. The observed response and analysis of the experimental database of TRCW suggest that some walls could present a limited displacement capacity compared to the maximum drifts allowed by the design code.

Shallow and Wide RC Beams, Definition, Capacity and Structural Behavior – Gap Study

Wide beam, shallow beam, and banded beam are almost equivalent terms for beams with limited depth and large width. They are often embedded in ribbed slabs to facilitate the formwork. The contribution of web reinforcement in the shear capacity of this type of beam is still a gray area, and all design codes neglected this contribution. The aim of this research is to introduce a general overview of this topic and detect the unstudied gaps in this topic. Nine design codes and about forty previous researches were collected, summarized, analyzed, classified, and mapped with respect to the considered parameters, utilized methodologies, recorded observations, and concluded outcomes to detect further research opportunities. The results indicated that design codes have no unified definition for the shallow or wide beams; most of them neglected the contribution of the shear reinforcement. On the other hand, the analysis of the collected research considering 32 points of the study showed that only 19 points are well studied; it also indicated an extreme shortage in both theoretical studies (using “Finite Element Method” FEM) and predictive models (mathematically using “Artificial Intelligence” AI) for the shear capacity besides the effect of creep and cyclic loading, especially for beams with web openings.

Behavior of high-strength concrete (HSC) box girders reinforced with GFRP bars, ties, and spirals under torsion

To date, the torsional behavior of high-strength concrete (HSC) box girders reinforced with glass fiber-reinforced polymer (GFRP) reinforcement has not been investigated. This study reports on the experimental results of HSC box girders reinforced with GFRP bars, ties, and spirals under pure torsion. Seven full-scale reinforced concrete (RC) box girders with a total length of 4,000 mm, width of 380 mm, height of 380 mm, and wall thickness of 100 mm were examined over a clear span of 2,000 mm. The test parameters included the type, configuration, and amount of the web reinforcement and the concrete type. All specimens have the same longitudinal reinforcement ratio. The test specimens comprised three box girders reinforced with GFRP bars and individual ties, three specimens reinforced with GFRP bars and continuous spirals, and one box girder entirely reinforced with steel reinforcement as a reference specimen. Two girders were fabricated with normal-strength concrete (NSC)—one reinforced transversally with GFRP spirals; the other reinforced with ties—to investigate the influence of concrete type on torsional behavior. The test findings indicate that, at the same web reinforcement ratio and reinforcement configuration, the HSC specimens achieved higher pre- and post-cracking torsional strength and stiffness than their counterpart NSC specimens. The continuous spiral configuration instead of individual ties improved the overall torsional performance of the tested box girders. Moreover, the stirrup's capacity strongly influenced the torsional strength of the GFRP- and steel-reinforced concrete box girders, but the stirrup stiffness did not affect the ultimate torque.