Shear Span-depth Ratio Research Articles

EFFECT OF SHEAR SPAN TO DEPTH RATIO ON THE STATICAL BEHAVIOR OF HSCB SUBJECTED TO TRANSVERSE LOADING

Many researches were carried out to investigate the properties and structural performance of high strength concrete for many decades. While these researches have produced relevant and useful results, there are several properties of high strength concrete like compressive and tensile strengths, stiffness, durability, modulus of rupture, cracking shear load and ultimate load that need to investigate to determine an accurate evaluation of beams made of high strength concrete. This study investigates the effect of shear span-depth ratio (a/d) on the statical behavior of HSCB subjected to transverse loading. The effect of shear span to depth ratio includes some main mutual factors such as grade of concrete and stirrups spacing. The studied statical behavior includes: evaluation of pattern of cracks, modes of failure, concrete and steel strains, maximum deflection, flexural cracking load (Pcr), modulus of rupture, cracking shear load (Vcr) and finally ultimate load (Pu). For this purpose, an experimental test program was performed which included testing twenty four large scale simply supported rectangular high strength concrete beams under one concentrated transverse load at mid span. The values of the main factors were; the shear span to depth ratio (a/d) were taken (3, 2, 1.5 and 1), the cube compressive strength (fcu) were (575, 766 and 890) kg/cm2and the stirrups spacing were (20, 14.28, 11.11and without stirrups) cm, while the longitudinal reinforcement was kept constant for all tested beams. For all tested beams, max. Deflections, strains in the longitudinal reinforcement, and strains in concrete were measured and recorded. Also, the initiation and propagation of cracks were recorded. Cracking patterns and failure modes were observed. Cracking and failure loads were recorded. The test results were compared with different codes and formulas. Based on this, conclusions were drawn out for induced measured maximum deflection, steel and concrete strain, the cracking load the modulus of rupture, shear cracking load and ultimate load for beams with and without stirrups. In addition, ultimate shear load for beams without stirrups utilizing different code provisions was predicted and compared with the obtained test results.

Shear Span–Depth Ratio Effect on Behavior of RC Beam Shear Strengthened with Full-Wrapping FRP Strip

AbstractShear span-to-effective depth ratio (av/d) is known to affect the shear behavior of RC members. However, this effect has not been appropriately addressed in existing design guidelines for the fiber-reinforced polymer (FRP) strengthening of RC structures. This paper focuses on the effect of av/d on the behaviors of RC beams shear strengthened with full-wrapping FRP strips. A total of six strengthened beams and six normal beams are tested, with av/d ratios ranging from 1.0 to 3.5. The experimental results indicate that the FRP shear contribution increases initially with the av/d ratio, but decreases when the ratio is beyond 2.5. The FRP strain along the critical shear crack distributes in different manners for different av/d ratios. The authors’ experimental results and the test results from the literature are compared with predictions from available design guidelines. Although some recent design guidelines always provide a safe value, it can be overconservative. Conversely, other recent design guid...

Variable Shear Span-Depth Ratios for Reinforced Concrete Beams Strengthened with Various CFRP Configurations

Variable Shear Span-Depth Ratios for Reinforced Concrete Beams Strengthened with Various CFRP Configurations

Inverted T-Beams: Experiments and Strut-and-Tie Modeling

Contrary to rectangular deep beams, inverted-T beams are loaded on a ledge at the bottom chord of the beam. This loading configuration induces a tension field into the web and the resulting complex strain distribution renders sectional design provisions inadequate. The applicability of strut-and-tie modeling (STM), developed for rectangular deep beams and simpler, two-dimensional designs, was evaluated. An experimental study was conducted in which 33 tests were performed on 22 large-scale reinforced concrete inverted-T beams and the effects of the following variables were investigated: ledge geometry, quantity of web reinforcement, number of point loads, member depth, and shear span-depth ratio. It was concluded that strut-and-tie modeling, although developed for much simpler structural components, offers a simple and accurate design method for the more complex strain distributions in inverted-T beams. The STM provisions developed for rectangular beams accurately captured both failure mode and ultimate capacity and are recommended for use in inverted-T beam design, as a major conclusion of this research.

Effect of Steel Fiber Content on Behavior of Concrete Beams with and without Stirrups

An experimental study is conducted on a series of 12 reinforced concrete (RC) and steel fiber-reinforced concrete (SFRC) beam specimens to study their shear and flexural strengths, failure mechanisms, and ductility response under monotonic loadings. The main parameters varied in this study are the concrete compressive strength, percentage of longitudinal reinforcement, fiber content, shear span-depth ratio, and amount of transverse stirrups. End-hooked steel fibers of volume fraction ranging from 0.5 to 1.5% are used in the specimens. Test results showed that the addition of steel fibers enhanced the flexural and shear strengths and the ductility of the flexural members. The addition of a minimum of 0.5% fiber content in the beams with shear stirrups changed the mode of failure from brittle to ductile, whereas a minimum fiber content of 1.0% is required to achieve the ductile response of the beams without shear stirrups. Using a curve-fitting method on the available test data, simple expressions are also derived to predict the shear strengths of medium- to large-scale flexural members with varying fiber contents.

Depth Effect in Deep Beams

An experimental study was performed to examine the effect of section depth on the strength and serviceability of reinforced concrete deep beams. Full-scale tests were conducted on simply supported beams with the following cross sections: 21 x 23 in. (533 x 584 mm), 21 x 42 in. (533 x 1067 mm), and 21 x 75 in. (533 x 1905 mm). Tests were performed on each section type at the following shear span-depth ratios (a/d): 1.2, 1.85, and 2.5. Diagonal cracking loads, diagonal crack widths, and shear at failure were recorded for each test. The strength results indicated that the shear capacity of a deep beam is governed by the strength of the nodal regions, which are not directly proportional to the member depth. When deep beams are designed with strut-and-tie models, the strength of the nodal regions are addressed explicitly and no depth effect on the shear capacity of the member is apparent.

Prediction of Failure Loads of RC Dapped-End Beams

Shear failure remains the governing mode of failure for reinforced concrete (RC) dapped-end beams. Dapped-ends are commonly classified as disturbed regions (D-regions). Strut and tie model (STM) is a simple and rational way that can be applied to analyze D-regions. The current design codes such as ACI-318-08, Euro Code 2 and BS 8110 facilitate STM to predict the failure loads. In addition, the failure loads may be also predicted using the empirical method proposed in PCI Design Handbook. In this paper, the failure loads were predicted for 24 RC dapped-end beams following different codes. The significant parameters such as concrete compressive strength, dapped-end section size, shear span-depth ratio, type and effective range of stirrups, bent form of the longitudinal reinforcement, amount of dapped-end reinforcements and hanger reinforcements were varied to study their effects against the predicted failure load for RC dapped-end beams according to different codes. These predicted results were compared with the available experimental results to investigate the ability of various codes to predict the failure load reliably. In this study, the comparison shows that PCI Design Handbook and ACI-318-08 can predict the failure loads for RC dapped-end beams more accurately.

스터럽이 없는 GFRP 보강근 콘크리트 보에 대한 실험적 연구

This paper evaluates the shear strength, behavior and failure mode of reinforced concrete beams with deformed GFRP reinforcing bar. Four concrete beam specimens were constructed and tested. It was carried out to observe failure behavior and load-deflection of simply supported concrete beams subjected to four-point monotonic loading. In order to eliminate of the uncertainty by the shear reinforcements, any stirrups were not used. Variables of the specimens were shear span-depth ratio, effective reinforcement ratio. The dimensions of specimen is 3,300 or . Clear span and shear span were 2,900mm, 1,000mm respectively. Shear span-depth ratios were 6.5 and 2.5. Effective ratios of Longitudinal GFRP reinforcing bar were , , and . All beam specimens were broken by diagonal-tension shear and the ACI 440.1R, CSA S806 and ISIS, which was used to design test beams, showed considerable deviation between prediction and test results of shear strengths.

Shear Behavior of Reinforced Geopolymer Concrete Thin‑Webbed T-Beams

This paper describes the experimental studies on shear behavior of reinforced geopolymer concrete (RGPC) thin-webbed T-beams. The proportion of KOH to K(2)SiO(3) in alkaline activator solution, the shear span-depth ratio (a/d = 1.9 and 2.5), and percentage of web reinforcement were the test parameters for beam specimens. All the beams were provided with the same flexural reinforcement and were tested under two-point loading. This paper presents the details of the mixture designs of geopolymer concrete (GPC) mixtures, preparation of RGPC beams, testing and evaluation of structural behavior with respect to cracking and limitultimate load, deflections at various stages, and failure modes. The shear strengths of GPC beams obtained in the tests have been compared with the provisions for shear strength of reinforced concrete beams given in ACI 318. It was observed that the performance of the beams was influenced by their compressive strength and stirrup spacing. The results of the study indicate that the performance of RGPC is similar to that of reinforced portland cement concrete beams and the ultimate loads are in the same order.

Shear performance of prestressed ultra high strength concrete encased steel beams

Due to the high compressive strength and durability properties of ultra high strength concrete, prestressed ultra high strength concrete beam was used extensively in bridge engineering, but it possessed obvious brittle behavior. Encasing structural steel into it was a good way for alleviating the problem of brittleness. The purpose of this study was to investigate shear performance of prestressed ultra high strength concrete encased steel beams. A total of fifteen prestressed ultra high strength concrete encased steel beams and seven prestressed ultra high strength concrete beams were tested to shear failure under simply supported three-point loading conditions. The primary variables of this investigation included the presence or not of structural steel, shear span-depth ratio, degree of prestress, ratio of stirrup and thickness of web. The shear performance was evaluated based on cracking pattern, load–deflection behavior and shear ductility. Test results showed that prestressed ultra high strength concrete encased steel beams had higher residual shear capacity and post-cracking stiffness as well as by far better shear ductility than prestressed ultra high strength concrete beams. In addition, influence of experimental parameters on the shear performance of prestressed ultra high strength concrete encased steel beams and prestressed ultra high strength concrete beams also was discussed and compared, respectively.

Mechanical Behaviors of Steel Reinforced ECC or ECC/Concrete Composite Beams under Reversed Cyclic Loading

Engineered cementitious composite (ECC) is a class of high performance cementitious composites with pseudo strain hardening behavior and excellent crack control. Substitution of concrete with ECC can avoid the cracking and durability problems associated with brittleness of concrete. In this paper, two series, totaling six steel reinforced beams with various transverse reinforcement ratios, ECC thicknesses, and shear span-depth ratios were tested under reversed cyclic loading. According to the test results, steel reinforced ECC beams show better seismic performance in terms of load carrying capacity, shear resistance, energy dissipation capacity, and damage tolerance compared with steel reinforced concrete beams. The extent of load capacity improvement strongly depended on the failure mode. Beams failed in shear showed more significant improvement than those failed in flexure. For the ECC/concrete composite beam, strategic application of ECC can lead to an increase of energy dissipation capacity. For the steel reinforced ECC beam without stirrups, final failure occurs in shear. However, the ultimate load capacity and deformation are comparable to the steel reinforced concrete beam with properly designed stirrups, and the failure process is ductile due to the strain hardening behavior of ECC materials.

Enhancement of shear strength and ductility for reinforced concrete wide beams due to web reinforcement

The shear behavior of reinforced concrete wide beams was investigated. The experimental program consisted of nine beams of 29MPa concrete strength tested with a shear span-depth ratio equal to 3.0. One of the tested beams had no web reinforcement as a control specimen. The flexure mode of failure was secured for all of the specimens to allow for shear mode of failure. The key parameters covered in this investigation are the effect of the existence, spacing, amount and yield stress of the vertical stirrups on the shear capacity and ductility of the tested wide beams. The study shows that the contribution of web reinforcement to the shear capacity is significant and directly proportional to the amount and spacing of the shear reinforcement. The increase in the shear capacity ranged from 32% to 132% for the range of the tested beams compared with the control beam. High grade steel was more effective in the contribution of the shear strength of wide beams. Also, test results demonstrate that the shear reinforcement significantly enhances the ductility of the wide beams. In addition, shear resistances at failure recorded in this study are compared to the analytical strengths calculated according to the current Egyptian Code and the available international codes. The current study highlights the need to include the contribution of shear reinforcement in the Egyptian Code requirements for shear capacity of wide beams.

Rotation capacity and stress redistribution ability of R-UHPFRC–RC composite continuous beams: an experimental investigation

The results of tests on two continuous composite beams combining a reinforced concrete (RC) beam with a layer of reinforced ultra-high performance fiber reinforced concrete (R-UHPFRC) are presented. The R-UHPFRC element acts both as a tensile membrane and a flexural element. The tests show the element’s contribution to the member capacity by allowing the redistribution of the internal forces. The continuous beams are placed on two intermediate supports; the shear span-depth ratios and stirrup content are chosen to provoke two successive formations of local flexure-shear collapse mechanisms, forming a plastic hinge at each support. With the formation of the first support hinge, the stresses redistribute. As the applied actuator displacement increases, the member continues to resist the increasing force up to the formation of a second support hinge that causes the member to collapse. The member deflection and resistance at collapse were respectively 4.5 and 1.3 times greater than the corresponding values at the formation of the first hinge. The response demonstrates the redundancy in RC beams with additional R-UHPFRC reinforcement, which can be used for designing structures against progressive collapse.

Minimum Web Reinforcement in Deep Beams

An experimental study was performed to examine current code requirements for minimum web reinforcement of reinforced concrete deep beams. Twelve full-scale tests were conducted in which the shear span-depth ratio (a/d) was 1.2, 1.85, or 2.5. At each a/d, the quantity of web reinforcement was the primary variable. Web reinforcement ranged from 0 to 0.3% in the vertical and horizontal directions. The compressive strength of concrete of the test specimens ranged from 3200 to 5000 psi (22 to 34 MPa). Diagonal cracking loads, diagonal crack widths, and failure shears were recorded for each test. The results indicated that a larger quantity of web reinforcement was needed to adequately restrain the width of diagonal cracks than to provide adequate deep beam shear capacity. Based on the strength and serviceability results, a minimum web reinforcement of 0.3% in each orthogonal direction was recommended for deep beams.

Strength Modeling of Concrete Deep Beams Reinforced with Internal Fiber-Reinforced Polymer

It is well-known that arch action in deep concrete members provides a beneficial increase in strength. However, while specific design code provisions are available for steel-reinforced deep members that account for this influence, current design code provisions for members containing internal fiber-reinforced polymer (FRP) reinforcement do not consider the capacity obtained from arch action. Strut-and-tie-based modeling approaches for FRP reinforced members were developed through the adaptation of existing models for steel-reinforced concrete deep members. When compared to test results for large-scale members with small shear span-depth ratios (a/d), the recommended strut-and-tie model (STM) is shown to be in better agreement than existing shear provisions for FRP-reinforced members. The proposed STM is also shown to accurately account for influences on capacity from the reinforcement ratio, reinforcement stiffness, and overall member height.

Estimation of Shear Behavior of Ultra High Performance Concrete I Girder without Shear Stirrups

Thinner and lighter members can be designed by utilizing the high stiffness and toughness, and high compressive strength of Ultra High Performance Concrete (UHPC), which reaches up to 180MPa. This high strength and ductile tensile behavior of UHPC makes it possible to design the web of the UHPC I Girder without conventional shear stirrups, which makes the UHPC I girder slender, light and economical. However, establishing shear design procedure for UHPC I girders without stirrups requires additional theoretical and experimental studies. This paper investigated shear behavior of UHPC I girder without shear stirrups. The test results show, in spite of no shear stirrups, test specimens have high ductility due to the bridging action of steel fibers against crack opening. UHPC I girders without shear stirrups tested show gradual increase of strength after initial cracking instead of brittle loss of strength as expected from the ordinary reinforced concrete I girders without stirrups. The decrease of the shear span-depth ratio increase the shear strength of the UHPC I girder without stirrups.

Shear strength of palm oil clinker concrete beams

This paper presents experimental results on the shear behavior of reinforced concrete beams made of palm oil clinker concrete (POCC). Palm oil clinker (POC) is a by-product of palm oil industry and its utilization in concrete production not only solves the problem of disposing this solid waste but also helps to conserve natural resources. Seven reinforced POCC beams without shear reinforcement were fabricated and their shear behavior was tested. POCC has been classified as a lightweight structural concrete with air dry density less than 1850kg/m3 and a 28-day compressive strength more than 20MPa. The experimental variables which have been considered in this study were the POCC compressive strength, shear span–depth ratio (a/d) and the ratio of tensile reinforcement (ρ). The results show that the failure mode of the reinforced POCC beam is similar to that of conventional reinforced concrete beam. In addition, the shear equation of the Canadian Standard Association (CSA) can be used in designing reinforced POCC beam with ρ⩾1. However, a 0.5 safety factor should be included in the formula for ρ<1.

Shear Behavior of Self-Consolidating Concrete Beams

This study investigates the shear behavior of beams made with different types of self-consolidating concrete (SCC). The first type of SCC (SCC1) contained a greater amount of coarse aggregate, than the second type (SCC2). A total of 24 beam specimens were tested: 8 were SCC1 beams, 8 were SCC2 beams and 8 were normal concrete (NC) beams. The parameters included the concrete strength, shear span-depth ratio (a/d), shear reinforcement strength, and spacing of shear reinforcement. Results showed that the overall performance of SCC1 beams is better than or as good as NC beams, but SCC2 beams have inferior structural performance than NC beams in many aspects. Both types of SCC beams have smaller crack widths than NC beams. SCC1 beams had higher diagonal cracking strengths and ultimate strengths than NC beams. The shear ductility of SCC1 beams is comparable with that of NC beams. SCC2 beams had less strength than NC beams. The diagonal cracking and ultimate strengths predicted by ACI 318-08 are conservative for this study. The ACI limit on design yield strength of shear reinforcement may be increased for SCC1 beams based on crack width criterion. These findings indicate that the amount of coarse aggregate can have a significant effect on the shear behavior of SCC in terms of stiffness, strength and ductility. An amount of coarse aggregate greater than 900kg/cu m (56.1 lb/cu ft) is suggested.

Effective Capacity of Diagonal Strut for Shear Strength of Reinforced Concrete Beams without Shear Reinforcement

The appropriate evaluation of the effective capacity of a concrete strut is an important factor in the analysis and design of concrete members using the strut-and-tie model. Current design codes for the strut-and-tie model introduce this factor using the effective compressive strength of concrete in a strut or nodal zone. This study considers that the mechanism of diagonal cracking reduces the width of a concrete strut and hence causes a reduction in the capacity of the concrete strut. Based on this approach, models for predicting the diagonal cracking strength and ultimate shear strength of simply supported beams without shear reinforcement are proposed, with the concrete strength, shear span-depth ratio (a/h), and longitudinal reinforcement ratio as the primary parameters. The predicted values are compared with proven test data from various published experiments and codes of practice to show the validity of the proposed models.

Shear Capacity Prediction of Reinforced Concrete Beams without Stirrups Using Fracture Mechanics Approach

This study presents an analytical shear strength prediction equation for lightly reinforced slender concrete beams without stirrups based on the phenomenological experiment observations. The concept of the loss of bond performance between concrete and longitudinal reinforcement was used in these beams to explain the potential cause for the sudden release of longitudinal reinforcement from wrapping concrete. In the proposed equation, shear capacity was related to bond fracture resistance by introducing a new parameter: Mode II fracture toughness KIIc. The equation showed the size effect with effective depth to the power of -1/2 and was evaluated using test data published in other sources. Comparisons between the proposed formula and other prediction equations indicated that, for lightly reinforced slender concrete beams without stirrups, this developed formula can estimate the shear strength of beams with varying concrete strengths, shear span-depth ratios (a s/d), longitudinal reinforcement ratios, and beam depths with reasonable accuracy.