Presence Of Shear Reinforcement Research Articles

Influence of aggregate size on shear mechanism of reinforced concrete beam subjected to impact load

This study presents the influence of aggregate interlock, in terms of aggregate size, on shear mechanism of reinforced concrete beam under a drop-weight impact using a non-linear finite element model. Four aggregate sizes (8-, 16-, 24-, and 32-mm) were used to study the variation of the shear force at the critical section. Large shear force was recorded at the critical section for the specimens with the 32-mm aggregate size regardless of the impact mass and velocity. This is expected since larger aggregates create rougher surfaces and transfer larger shear forces than smaller ones. As the impact mass increased from 868 to 1700 kg, the critical section shear force decreased on average by 5.3%, regardless of aggregate size. Increasing the impact velocity by 41% decreased the critical section shear force by 58%, 56%, 45%, and 41.5% for the 8 mm, 16 mm, 24 mm, and 32 mm aggregate size specimens, respectively. The influence of aggregate size on the shear transfer mechanism was also studied in the presence of shear reinforcement and increased span-to-depth ratio. The difference in shear force at the critical section among the specimens with the different aggregate sizes is negligible in the presence of shear reinforcement indicating that the presence of stirrups reduced the contribution of aggregate interlock in shear resistance. Increasing the span length by 67% (from 3 to 5 m) decreased the effect of aggregate size by 95% on average.

Shear Strengthening of Reinforced Concrete Beam Using Wire Mesh–Epoxy Composite

This experimental research aims to study the use of wire mesh–epoxy composite (WMEC) as a shear-strengthening technique for reinforced concrete (RC) beams by focusing on the following parameters: (1) presence of shear reinforcement in the shear span; (2) type of strengthening technique (U-jacketing, vertical U strip, or inclined strip); and (3) number of wire mesh layers (three or six layers). Nine simply supported rectangular RC beams were tested under two monotonic point loads. The testing specimens were divided into two groups: (1) five beams without shear reinforcement and (2) four beams with shear reinforcement. Load–deflection relationship, shear ductility index, beams’ stiffness, energy absorption, crack propagation, mode of failure, and strain were studied for all testing specimens and compared with those of the control beams to measure the improvement from WMEC addition. Results showed that all WMEC types enhanced the shear capacity. Among the three shear-strengthening types, the continuous U-jacket scheme had a higher effect, increasing the shear capacity between 33.4 and 95.9% and the shear ductility index by 23% relative to those of the reference specimens. The shear capacity improvement by WMEC for the beams without shear steel reinforcement was greater than that for the beams with shear reinforcement under the same shear-strengthening configuration. When the number of wire mesh layers was doubled, the ultimate load was further increased from 33.4 to 57.8%. This research showed that WMEC is a practical and excellent shear-strengthening technique for RC beams. Doi: 10.28991/CEJ-2022-08-06-09 Full Text: PDF

Influence of link spacing on concrete shear capacity: experimental investigations and finite element studies

This paper investigates the influence of varying the spacing of shear reinforcement on the response of six geometrically identical reinforced concrete beams. Each beam was designed with differing longitudinal and transverse reinforcement configurations to provide improved understanding of the importance of providing sufficient shear reinforcement following guidance provided in Eurocode 2. Three different cases of varying transverse reinforcements were tested: one without the presence of shear reinforcement, one with shear reinforcement non-compliant to the design provisions and one where the design of the beams fully complies with the design guidance. In order to verify the experimental results, an open source digital image correlation software was utilised to allow for a computational crack mapping, along with the use of nonlinear finite element analysis software to enable a more thorough investigation of the individual beam response. The results obtained highlighted that shear links non-compliant to Eurocode 2 consequently led to unpredictable modes of failure, whereas beams containing shear links at the required amount and spacings displayed significant improvements in the mode of failure and ductility. Beams with the omittance of shear links resulted in the lowest load capacity, due to the sudden, brittle shear failure.

Lateral cyclic behavior of interior two-way concrete slab–column connections reinforced with GFRP bars

In flat plates, the use of high-strength concrete (HSC) in the slabs, and the presence of shear reinforcement in the vicinity of columns are considered effective, economical, and practical solutions for enhancing the punching shear performance of slabs. This paper presents the first-ever experimental results for interior concrete slab–column connections reinforced with glass-fiber-reinforced-polymer (GFRP) bars subjected to a combination of gravity and lateral reversed cyclic loads. Four full-scale slabs measured 2500 × 2500 mm with a thickness of 200 mm, and 300 mm square column extending 700 mm above and below the slab surfaces specimens were constructed and tested until failure. The main test variables were (i) flexural-reinforcement type (GFRP and steel bars); (ii) slab’s concrete compressive strength (NSC and HSC); and (iii) the use of GFRP shear reinforcement. All the tested specimens demonstrated adequate strength, deformation capacity, drift ductility indices, dissipated energy, and connection stiffness. The GFRP-reinforced NSC specimen without shear reinforcement showed adequate ability to withstand interstory drift up to 2.25% without punching failure. The GFRP-reinforced HSC specimen without shear reinforcement had a 33% higher lateral deformation and moment-transfer capacities compared to the GFRP-reinforced NSC specimen. The provision of GFRP-stirrups in the slab–column connection significantly influenced slab overall performance. The shear-reinforced specimen was able to sustain lateral drifts as high as 5% with no more than a 20% decrease in the moment carrying capacity. Moreover, the shear-reinforced slab was able to sustain the gravity load until the end of testing and only exhibited softer punching-shear failure with a gradual decrease in lateral loads.

Nonlinear Finite Element Analysis Formulation for Shear in Reinforced Concrete Beams

This study suggests a novel beam-column element formulation that utilizes an equilibrium-driven shear stress function. The beam shear is obtained from the bi-axial states of micro-planes, through matrix condensation and zero vertical traction assumptions. This properly remedies the shear stiffening of a one-dimensional beam-column element, keeping its degrees of freedom to a minimum. For verification of the proposed method, a total of seven shear test results of reinforced concrete (RC) beams were collected from the literature, in which the key variables were the reinforcement ratio, the presence of shear reinforcement, and section shape. The advantages are clearly shown in the shear stresses distributions being accurately described and the global load-displacement relations being successfully obtained and matching well with various test results. The proposed model shows satisfactory descriptions of the monotonic load-displacement response of the RC beams failing in multiple modes that vary from diagonal-tension to flexural-compression. In addition, more accurate and reliable information of sectional responses including sectional shear deformation and stresses is collected, leading to better prediction of a potential shear failure mode. Finally, the advantages of the proposed model are demonstrated by comparing the analysis results of an RCT-beam by using the different shear assumptions that include the constant and parabolic shear strains, constant shear flow, and the proposed shear stress function.

Mechanism of distributed composite GFRP bars in circular concrete members with and without spirals under shear

This paper presents experimental data and theoretical studies on the effect of distributed glass fiber-reinforced-polymer (GFRP) bars in circular concrete members. Th experimental program reports the test results of eight full-scale circular reinforced-concrete (RC) specimens with a total length of 3020 mm and a diameter of 508 mm were constructed and tested under shear load up to failure. The test specimens comprised three specimens reinforced with GFRP bars and spirals, three specimens with only longitudinal GFRP bars, and two reference specimens reinforced with conventional steel bars, with and without steel spirals. The various experimental parameters included the longitudinal reinforcement ratio, the type of reinforcement (GFRP versus steel), and presence of shear reinforcement. The shear strengths of GFRP circular concrete specimens, obtained from the experimental results, were compared to current codes and design guidelines as well as to the recently available shear design equations on circular concrete members in the literature. The test results indicate that the use of more GFRP bars distributed uniformly in the cross section, of the specimens with and without spirals, reduces the loss of flexural stiffness after cracking and increase the shear strength. The comparison indicates that some of the available design methods provide reasonable predictions.

Shear capacity of high performance fiber reinforced concrete I-beams

An experimental program was carried out to investigate the shear capacity of High-Performance Fiber-Reinforced Concrete (HPFRC) I-beams. The main parameters were assigned as the fiber content and presence of shear reinforcement. To study the effect of these main parameters on the shear capacity, testing of six I-beams and other control specimens was conducted. It can be observed from the results of the experimental study that the presence of fibers and shear reinforcement significantly improves the ultimate capacity and structural behavior of HPFRC members. Finally, the experimental results are discussed, and the shear capacity of HPFRC can be estimated by extending the code provisions stated in AFGC-Sétra 2013.

Numerical Investigation of the Shear Strength of RC Deep Beams Using the Microplane Model

AbstractAlthough much work has been done on the shear behavior of RC elements, current design provisions are still based on empirical data and their predictions, especially for deep beams, are not always reliable and can lead to unconservative results. This paper presents an extensive numerical investigation on the role of key parameters on the shear performance of RC deep beams using the microplane M4 material model. The model is validated against experimental results of 20 RC deep beams. A parametric study is then carried out to investigate the effect of shear span to depth ratio and concrete compressive strength for RC deep beams with and without shear reinforcement. Although a single strut mechanism is generally mobilized in deep beams, the presence of shear reinforcement can enable a more uniform distribution of shear stresses within the shear span and enhance the effectiveness of concrete cracked in tension. The study confirms that both shear span to depth ratio and concrete strength are the key par...

Study on Influence of Column Size and Slab Slenderness on Punching Strength

This paper presents the results of a systematic experimental campaign consisting of 13 symmetric punching tests on interior slab-column connections. The study focuses on the influence of varying the size of the supported area and the slenderness of the slab. Other investigated parameters are the flexural reinforcement ratio and the presence of shear reinforcement. The results of the present campaign and of previous tests are compared to the predictions of different codes of practice and to the critical shear crack theory (CSCT). The comparison shows that the CSCT and fib Model Code 2010 give the most consistent predictions, whereas the results of Eurocode 2 for small support sizes have a large scatter. The predictions of ACI 318 are observed as overall conservative in the investigated range. This study shows that slenderness has an important influence on the punching strength of slabs with shear reinforcement, despite the fact that it is neglected in many codes of practice.