Amount Of Shear Reinforcement Research Articles

The Impact of Shear Reinforcement Amount and Arrangement on the Shear Capacity of Shallow RC Beams: An Experimental Study

This study investigates the impact of shear reinforcement amount and arrangement on the shear capacity of shallow/wide RC beams. Seven specimens of shallow/wide beams with different ultimate shear reinforcement stress (μ.Fys), longitudinal spacing to depth ratio (S/d), and transversal spacing to depth ratio (S’/d) were tested under a monotonic three-point bending test. All the specimens were designed to fail at shearing. The results showed that the shear reinforcement was fully functioning until it yielded; also, the amount of shear reinforcement had the major impact on the shear capacity; in addition, the transverse spacing had more influence on the shear capacity than the longitudinal spacing. The measured shear capacities were compared to six design codes, in which the results ranged from 95% to 110%, with the Japanese code (JSCE) being the closest to the experimental results. Two AI-based predicting equations, “Genetic Programming” (GP) and “Evolutionary Polynomial Regression” (EPR), were also compared to the experimental, with accuracies of 78% and 86% of the measured capacities, respectively. Initial stiffness, final stiffness, dissipated energy, and ductility were all discussed for the seven specimens, with ultimate shear reinforcement stress being the most impactful on the total shear capacity of the wide beams. Doi: 10.28991/CEJ-2023-09-12-013 Full Text: PDF

Predicting the shear behavior of reinforced concrete beams with Fe-Based shape memory alloy stirrups

Existing studies using Fe-based shape memory alloys (SMAs) for shear reinforcement have focused on strengthening aged structures. Studies on using Fe-SMAs as shear reinforcements for new structures have not been reported. Accordingly, this study performed experiments to evaluate the shear behavior of reinforced concrete (RC) beams with Fe-based SMA stirrups. Ten specimens were prepared for the experiments. The activation of the Fe-SMA stirrup, stirrup spacing, and shear span-to-depth ratio were considered as variables. The Fe-SMA stirrups were activated via electrical resistance heating. Activating the Fe-SMA stirrups applied compressive forces to the specimen, reduced the occurrence of diagonal shear cracks, and improved shear stiffness. However, it did not significantly affect the shear strength. The shear contribution of the Fe-SMA stirrup increased with an increase in the shear span-to-depth ratio and amount of shear reinforcement. In addition, the simulation results using the modified compression field theory (MCFT)-based section analysis model were consistent with the experiment results. Therefore, the model can predict the shear behavior of RC beams with Fe-SMA stirrups.

Emergency stop lane design on national road in West Sumatra (case study: Panorama 1 Sitinjau Lauik)

West Sumatra Province has geographical conditions consisting of lowlands and highlands. These geographical conditions certainly affect the geometric conditions of the road, especially on the Panorama 1 Sitinjau Lauik National Road Section. One of the factors that cause accidents is a vehicle that has failed brakes. This study aims to calculate the length of the emergency stop lane; plan the structure of the building; and plan a modeling design. The results of the Emergency Stop Route Design research showed that the overall dimensions were 240 m. Preliminary design results are as follows: Beam (600 mm width and 1100 mm height), Amount of flexural reinforcement: Compression reinforcement 8 D – 25 mm; Tensile reinforcement 4 D – 25 mm; Amount of shear reinforcement: Area of support 2Ø13-100 mm, Area of field 2Ø13-150 mm. Cross beam width 300 mm and height 600 mm. Amount of flexural reinforcement: compression reinforcement 3 D 16 mm; Tensile reinforcement 3 D 16 mm. Number of shear reinforcement: Support area 2Ø13-100 mm and field area 2Ø13-150 mm. For longitudinal reinforcement, the diameter is ø10 – 200 mm, the tie reinforcement has a diameter of ø10 – 200 mm and the vertical reinforcement has a diameter of ø16 – 150 mm.

Finite Element Analysis of Punching Shear of Reinforced Concrete Slab–Column Connections with Shear Reinforcement

Shear reinforcement is one of the common measures used to strengthen slab–column connections. It can make the joint’s load capacity increase. However, when the connection is subjected to an unbalanced bending moment, the reduction effect of the shear reinforcement on the bending moment is worth investigating. Nonlinear finite element analysis was performed on reinforced concrete slabs with shear reinforcement for various moment-to-shear (M/V) ratios. The effects of the number and diameter of shear reinforcement and different loading methods on the slab were investigated, as along with a correction to the ACI-318 and China Concrete Structure Design code GB50010 formula for the moment transfer coefficient. The 3D finite element modeling was performed using appropriate element types and a constitutive model for concrete. The concrete damage plasticity model parameters were calibrated using the experimental results of a specimen. The amount of shear reinforcement had a certain contribution to the strength of the slab, but the diameter of the shear reinforcement had little effect. The plate’s bearing capacity decreased as the M/V increased. The corrected moment transfer coefficient formula demonstrates that M/V is positively correlated with the coefficient and that the calculated values specified in ACI-318 and GB50010 are overly conservative.

Enhanced service life of existing infrastructure buildings by use of concrete screw anchors as post-installed shear reinforcement

In the last decades, traffic on railways and roads has increased significantly in Central Europe. On the other hand, the existing infrastructure mainly origins from the late 1950s to the 1970s. This applies also for the existing bridge and tunnel infrastructure which is now up to 60 years old. Due to this age and new standards in the current codes, quite often the amount of shear reinforcement does not fulfil the current design code rules. As a replacement of existing structures is often highly unsustainable, methods to improve the shear strength are needed. Therefore, a new system for post-installed shear reinforcement by the use of concrete screws was developed at the University of Innsbruck in the last years. The idea is to use concrete screw anchors - already known as anchoring element - aspost-installed reinforcement. In over 60 shear tests with girders and slabs the excellent applicability of concrete screw anchors as post-installed shear reinforcement has been proven. Also shear tests with cyclic loading were performed prove the use for dynamically loaded structures, such as bridges. Based on these test results a design approach was determined to meet the Eurocode-2 assessment standards.Several pilot-projects with concrete screws have been realised in Austria and Germany. For example a rail-road-bridge over a German highway with a remaining service life of zero years was strengthened to a new service life of over 20 years. Also a city-centre tunnel in Munich which was erected below a historic building is currently strengthened under ongoing traffic in the tunnel using concrete screw anchors as post-installed reinforcement.

3D Finite Element Model for Shear-dominant Failure of Reinforced Concrete Beams

This study explores the 3D FE modelling approach in determining the behaviour of shear-dominant responses of RC beams. Five RC beams (A1, A2, B1, C2 and C3) with different cross-sections, amount of tension reinforcement area, amount of shear reinforcement and the length of the span was analysed and the results were compared with the results of the experiment and 2D analysis available in published literature. RC beams analysed in this FE study were constructed as a discrete model using ABAQUS software. The concrete and the plate for loading as well as for supports were modelled using the C3D8R element while longitudinal steel bars and stirrups were modelled with the T3D2 element. The interaction between the steel bar and the concrete in the FE model was assumed perfectly bond. The material behaviour of concrete was modelled with the damage plasticity model where the yield or failure of the material was governed by the tensile cracking and the compressive crushing of the concrete by introducing the hardening variables. The results showed that crack propagation in the FE analysis matched the cracks observed in the test. The crack pattern on Beam A1, A2, B1 and C2 indicated that the specimens experienced flexure and shear failure while Beam C3 experienced less brittle behaviour. Estimates of strength and the load–deformation response of 3D analysis were certainly achieved with reasonable accuracy compared to that of 2D analysis. The difference of experiment-to-2D strength (Pu,exp - Pu,2D / Pu,exp) had a mean of 4.53 whereas the difference of experiment-to-3D strength (Pu,exp - Pu,3D / Pu,exp) had a mean of 1.83. Furthermore, the displacements at ultimate load gained in the 3D analysis were comparable to those of experiments. The difference of experiment-to-2D (du,exp - du,2D / du,exp) and experiment-to-3D (du,exp - du,3D / du,exp) midspan displacement had a mean of 19.91 and 10.89, respectively.

Numerical and analytical evaluation of stirrup-induced confinement on resistance of RC beams using lower bound limit analysis

In this paper, a modified three-dimensional element is introduced for limit analysis of RC structures, which considers more aspects of structural behaviour. Using the introduced element, the influence of stirrup confinement on the shear and moment resistance of RC beams is evaluated by lower bound limit analysis. To analyse and solve the relevant optimization problem, the semidefinite programming method, SDP, is employed. The modified Mohr–Coulomb yield criterion is utilized to constrain the concrete stress state. Beams with a constant amount of shear reinforcement per unit length, with different values of stirrup spacing, are studied. It means that they only differed in the effect of confinement induced by stirrup reinforcements. The performance of the proposed element is verified by comparing the results of numerical limit analyses with experimental results. This comparison revealed the efficiency and accuracy of the proposed model and the capability of the introduced element to take the effect of stirrup-induced confinements into account. After modelling and investigating the effect of stirrup confinement in load bearing of RC beams, a simplified equation for the design and practical purposes is proposed. Using this equation, the shear resistance of the beams could be modified for different stirrup space choices. The results obtained from this simplified equation are compared with numerical limit analysis and experimental results. The comparisons indicate the reasonable accuracy of the proposed equation.

Contribution of concrete and shear reinforcement to the punching shear resistance of column bases

The punching shear capacity of reinforced concrete flat slabs and column bases without shear reinforcement as well as with failure on the level of maximum punching strength has been analyzed extensively in the past. For shear-reinforced slabs, most punching shear models follow an additive approach assuming a combination of a contribution of concrete and a contribution of shear reinforcement (steel contribution). However, a systematic evaluation of concrete and steel contributions depending on the amount of shear reinforcement has not yet been adequately possible since only a few test series with low and medium amounts of shear reinforcement investigating the failure within the shear-reinforced zone have been available.In this paper, the development of concrete and steel contributions in shear-reinforced column bases is investigated in detail based on eleven punching tests with systematically varying shear reinforcement ratios. Significant differences between various punching design approaches regarding the interaction of concrete and steel contributions are revealed and a new method for evaluation is presented. The development of both contributions depending on the amount of shear reinforcement is discussed and compared to the design provisions according to Eurocode 2, Model Code 2010 and the draft for the next generation of Eurocode 2 which has been undergoing an optimization process in recent years.

Punching Shear Strength of Reinforced Concrete Flat Plates with GFRP Vertical Grids

In this study, the structural behavior of reinforced concrete flat plates shear reinforced with vertical grids made of a glass fiber reinforced polymer (GFRP) was experimentally evaluated. To examine the shear strength, experiments were performed on nine concrete slabs with different amounts and spacings of shear reinforcement. The test results indicated that the shear strength increased as the amount of shear reinforcement increased and as the spacing of the shear reinforcement decreased. The GFRP shear reinforcement changed the cracks and failure mode of the specimens from a brittle punching to flexure one. In addition, the experimental results are compared with a shear strength equation provided by different concrete design codes. This comparison demonstrates that all of the equations underestimate the shear strength of reinforced concrete flat plates shear reinforced with GFRP vertical grids. The shear strength of the equation by BS 8110 is able to calculate the punching shear strength reasonably for a concrete flat plate shear reinforced with GFRP vertical grids.

Performance of reinforced concrete slabs under punching loads

The experimental program of this study consisted of 12 slab specimens. The parameters investigated include ratio of reinforcement in compression and tension, amount of shear reinforcement and arrangement of shear reinforcement. Flexural reinforcement ratio especially in tension had a noticeable effect on the mode of failure and ultimate punching capacity of slabs. The enhancement in the ultimate loads due to increasing tensile reinforcement ratio was ranging between 26.0 and 42.0%. Slightly enhancement (up to 12%) in ultimate loads was observed as a result of increasing compressive steel ratio. Provision of shear reinforcement was shown to be increased the perimeter of the failure. The ultimate loads were increased with the addition of single leg stirrups as shear reinforcement particularly in case of radial arrangement of shear reinforcement. The ECCS shows the most conservative prediction for punching shear capacity specially in case of using shear reinforcement and the mean predicted-to-experimental ultimate load is shown to be 0.7. The predictions following the ACI and CSA are closet to the experimental results. The mean predicted-to-experimental ultimate load is shown to be 0.8 for ACI and 0.96 for CSA. The BS provisions for punching shear analysis were shown to be overestimated in some cases, where the mean predicted-to-experimental ultimate load is shown to be 1.19.

Shear resistance analytical evaluation for RC beams with transverse reinforcement with two different inclinations

An analysis-oriented mechanical model for shear strength evaluation of Reinforced Concrete (RC) beams with transverse reinforcement with two different inclinations, which required a numerical analysis, is turned into a design-oriented analytical model that can easily be utilized for practical purposes. The model assessed the shear resistance, according to the “lower-bound solution”, employing a numerical procedure that maximizes the element shear strength varying the stresses in the two sets of transverse reinforcement and the magnitude and inclination of the web concrete compressive stress field. The model is formulated with the aim of representing an extension of Eurocode 2 framework to RC beams with two orders of stirrups. In this paper, an analytical procedure is derived, substituting the former numerical maximization procedure, in order to obtain the optimal values of the aforementioned parameters, for any layout and amount of shear reinforcement. Comparison between shear strength predictions provided by the model and test results available in the literature confirms the model’s efficiency.

Shear behavior of two-span fiber reinforced concrete beams

The presented study was conducted to assess the shear capacity and the mechanical behavior of fiber reinforced concrete two-span beams in a five-point bending test. Experimental research was focused on observing changes in the behavior of tested elements depending on the amount of shear reinforcement (stirrups) and the fiber type used. The beams had varied stirrup spacing and two sorts of fibers were used as dispersed reinforcement. The steel fiber content was 78.5 kg/m3 and the basalt fiber content was 5.0 kg/m3. Concrete beams without addition of fibers were also examined as reference ones. The effectiveness of both sorts of fibers as shear reinforcement was assessed on the basis of strain development and crack pattern analysis. The digital image correlation technique was used to monitor the development of cracks around the central support of beams. It was shown that fibers control the cracking process and deformations in reinforced concrete beams and they can be effectively used as additional or the only shear reinforcement. The results of shear capacity obtained in the experiment were also compared with the shear capacity calculated according to current design approaches. This analysis has shown that fibers enhance the ultimate shear strength of reinforced concrete beams.

Precast bridge construction with UHPFRC—Shear tests and railway bridge pilot application

AbstractDue to the favorable material properties, Ultra‐High Performance Fiber‐Reinforced Concrete (UHPFRC) opens up new potential for precast options in PC bridge construction. On that matter, this article outlines the application, the load‐bearing behavior and advantages of two different possibilities: slender prestressed bridge girders and a prestressed trough‐shaped bridge element. Prestressed bridge girders made of UHPFRC allow for the realization of very slender cross‐sections with thin webs. For these beams, the shear capacity is the governing design issue. Hence, further investigations on the shear behavior with a variation of the fiber content, the prestressing level as well as the amount of shear reinforcement were undertaken. In this context, also size effects were examined using specimens with different construction heights up to 1.0 m. To enable testing of a high number of specimens with realistic cross‐sectional dimensions and at reasonable effort, an innovative experimental setup was developed and used for the investigations. Apart from these laboratory tests the present article deals with the pilot application of a railway bridge made of UHPFRC in Germany. The design and construction process as well as measurement results of the load and deformation behavior of the prestressed precast bridge element are presented and discussed.

Punching Shear Behavior of Shear Reinforced Slab\u2013Column Connection with Varying Flexural Reinforcement

The effects of flexural reinforcement and shear reinforcement on the punching shear strength of slab–column connections are analyzed in this study. For the study, six slab–column connection specimens were constructed with varying flexural reinforcement and shear reinforcement, and were subjected to gravity load tests. Experimental results showed that all specimens were destroyed by punching failure, and that the slab–column connection behaved differently depending on the amount of shear reinforcement and flexural reinforcement. Particularly, the flexural reinforcement in the slab–column connection improved the punching strength of the specimens with or without shear reinforcement. In addition, in this study, a design formula that considers the flexural reinforcement ratio in the calculation of the punching shear strength of the shear reinforced slab–column connection was proposed and was verified using experimental results and existing test data.

Effect of coarse aggregate content on shear friction of concrete

Shear friction behaviour of normal- and high-strength concretes made with different amounts of coarse aggregate was investigated in this study. A total of 48 push-off specimens were made and tested. Twenty-four of the specimens were made with normal-strength concrete; the rest were made with high-strength concrete. The test variables included the concrete strength, coarse aggregate content and amount of shear reinforcement. The results show that an increase in coarse aggregate content would increase the splitting strength of concrete cylinder, ultimate shear friction strength and shear ductility of the push-off specimens for normal-strength concrete. However, there should be an upper bound of 950 kg/m3 to ensure better ultimate shear friction strength and ductility for high-strength concretes. The same amount of coarse aggregate could be the lower bound for normal-strength concretes to achieve the code-specified splitting strength. The ACI code shear friction strength calculations are conservative. The λ modification factor for normal-weight concrete as specified in the code may be raised up to 1·3, which was the lower bound found in this study.

Failure Mode of Basalt Fibre Reinforced Concrete Beams

The experimental tests were carried out to assess the failure model of basalt fibre reinforced concrete beams. Experimental research was focused on observing the behavior of the tested elements depending on the amount of shear reinforcement and the content of fibres. Model two-span beams with a cross-section of 80x180 mm and a length of 2000 mm were tested. The beams had a varied stirrup spacing. The following amounts of basalt fibres in concrete were used: 2.5 kg/m3 and 5.0 kg/m3. At the same time, the concrete beams without fibres were examined. The beams were loaded in a five-point bending test until they were destroyed. Shear or bending capacity of the element was determined. Fibre reinforced concrete beams were not destroyed rapidly. Failure mode of beams varied in dependence on the amount of shear reinforcement and fibre content in concrete. Larger number of diagonal cracks with a smaller width were observed in fibre reinforced concrete beams. Failure of beams of concrete without fibres was rapid with a characteristic brittle cracking. Basalt fibres revealed the ability to transfer significant shear stress after cracking in comparison to plain concrete.

Shear Performance of Optimized-Section Precast Slab with Tapered Cross Section

The optimized-section precast slab (OPS) is a half precast concrete (PC) slab that highlights structural aesthetics while reducing the quantity of materials by means of an efficient cross-sectional configuration considering the distribution of a bending moment. However, since a tapered cross section where the locations of the top and bottom flanges change is formed at the end of the member, stress concentration occurs near the tapered cross section because of the shear force and thus the surrounding region of the tapered cross section may become unintentionally vulnerable. Therefore, in this study, experimental and numerical research was carried out to examine the shear behaviour characteristics and performance of the OPS with a tapered cross section. Shear tests were conducted on a total of eight OPS specimens, with the inclination angle of the tapered cross section, the presence of topping concrete and the amount of shear reinforcement as the main test variables and a reasonable shear-design method for the OPS members was proposed by means of a detailed analysis based on design code and finite-element analysis.

Failure mode in shear of steel fiber reinforced concrete beams

Experimental tests were carried out to assess the failure model of steel fiber reinforced concrete beams. Experimental research was focused on observing changes in the behavior of the tested elements depending on the amount of shear reinforcement and the fiber. Model two-span beams with a cross-section of 80x180 mm and a length of 2000 mm were tested. The beams had varied stirrup spacing. The following amounts of steel fibres in concrete were used: 78.5 kg/m3 (1.0%) i 118 kg/m3 (1.5%). Concrete beams without fibres were examined at the same time. The beams were loaded in a five-point bending test until they were destroyed. Shear or bending capacity of the element was observed. Fibre reinforced concrete beams were not destroyed rapidly, but they kept their shape consistent under load. Larger number of diagonal cracks with a smaller width were observed in fibre reinforced concrete beams. Failure of concrete beams without fibres was rapid, with a characteristic brittle cracking. Steel fibres revealed the ability to transfer significant shear stress after cracking in comparison to plain concrete.

The Maximum Punching Capacity of Flat Slabs

Two ways how to determine maximum punching resistance of flat slabs with shear reinforcement are currently used. The first way is verification of the concrete strut capacity at the column periphery defined as VRd,max. The second limit is defined as kmax multiple of the punching shear resistance without shear reinforcement VRd,c. The values of kmax are proposed usually in between 1.4 and 2.0. Results of the experimental tests are presented in the paper that were focused on above mentioned limits, whether failure of the struts can precede any other form of punching failure that is limited by kmax*VRd,c. Two experimental slab samples reinforced with high amount of shear reinforcement that increased punching capacity above capacity of the concrete struts were tested together with two slab samples cast without shear reinforcement. Comparison has shown that punching resistance of flat slab with shear reinforcement has been 1.7 times higher than resistance without shear reinforcement. While some standards allow for use kmax value of 1.9 in this case. This indicates that limits based only on the kmax factors may overestimate actual maximum punching shear resistance.

Experimental investigation of existing non-conforming RC shear walls

This work forms part of a research program to assess and strengthen existing non-conforming reinforced concrete walls, namely walls designed according to older seismic codes that do not meet the modern seismic provisions. For this purpose, a series of four shear walls, representing typical medium-rise walls, was designed and tested as cantilevers under static cyclic loading. The wall specimens are characterized by various reinforcement arrangements, focusing mainly on different amounts of shear reinforcement and on the buckling of compressive longitudinal rebars. The experimental results are compared with the assessment provisions included in Eurocode 8 – Part 3 for estimating the strength and deformation capacity of existing reinforced concrete members.