Flexural Reinforcement Research Articles

Experimental investigation of the compressive and shear resistance of laminated steel-reinforced glass beams

This paper presents an experimental investigation into the compressive and shear resistance of triple-layered laminated steel-reinforced glass beams. Two types of tests are performed: (a) local compressive tests (force over a support) and (b) bending tests (force close to a support). In total, six local compressive tests and eight bending tests are performed. Overall, beams with a shear span-to-effective depth ratio (a/d) approximately equal to 0, 0.63, and 1.0 are tested. Two different types of flexural reinforcement are used separately: solid (S) and hollow (H) reinforcement. The behaviour of the outer glass panes, and top and bottom reinforcement is monitored using strain gauges and Digital Image Correlation (DIC). The test results are elaborated in terms of load-displacement curves, the evolution of strains and crack patterns. Three failure modes are observed: yielding of the reinforcement (PF), crushing of glass (CF), and rupture of the reinforcement (RR). Shear failure occurred due to the crushing of glass in the compressed diagonal strut in the shear span. It was found that the shear resistance increases with a smaller shear span-to-effective depth ratio and stronger reinforcement. The dominant shear transfer mechanism was the direct strut action. It was found that the post-fracture capacity had a relatively constant value for all the tests with a slight increase for smaller a/d. The actual tensile strains in the bottom reinforcement measured by DIC are compared with the calculated strains based on the curvature of uncracked and cracked cross-sections, assuming plane section behaviour. It was observed that the actual strains are systematically larger than the calculated ones because, in reality, the section does not remain plane. After the appearance of the first crack, the beams essentially behave like strut-and-tie systems, where the strut is the diagonally compressed laminated glass and the tie is the bottom reinforcement.

Structural performance of hybrid reinforced concrete beams containing polyvinyl alcohol fibers under thermal loads

This study focused on the efficiency of concrete beams containing polyvinyl alcohol fibers (PVA) under thermal loads. The eighteen concrete beams were reinforced with hybrid bars or a combination of GFRP bars and steel reinforcement bars (hybrid scheme). The main experimental variables were the level of temperature (25o, 300o, and 600o C), PVA fiber volume (0 %, 0.50 %, and 1.0 %), and the flexural reinforcement bars. The experimental test results are discussed in terms of the first crack load, flexural capacity, and load-deflection curves. Moreover, the initial and post-crack stiffness, ductility factor, and failure modes are discussed. The test results demonstrated a significant increase in the capacity of PVA concrete beams reinforced with hybrid reinforcement bars. At a temperature of 300o C, the inclusion of 0.50 % and 1.0 % PVA ratios improved the flexural capacities by 11 % and 24 %, respectively. Furthermore, the addition of PVA fibers enhanced the toughness by 34 % and 67 %, respectively, when compared to normal concrete beams. The results also demonstrate that using PVA fibers prevents the spalling of concrete beams after exposure to elevated temperatures. At 600 °C, beams containing 0.50 % and 1.0 % PVA fibers exhibited flexural capacities that were 9 % and 6 % higher, respectively, compared to normal concrete beams. Additionally, the inclusion of PVA fibers increased the toughness by 27 % and 21 % for the respective fiber ratios. Finally, a nonlinear finite element analysis (NLFEA) simulation was performed to verify the experimental test results and supplement experiments by predicting the results that are difficult to accomplish through experiments. With an average ratio of 1.02 between experimental and NLFEA ultimate capacity, the numerical results were an exact match of the patterns observed in the experimental results.

Test and Analysis of Concrete Beams Reinforced by Polyurethane Concrete–Prestressed Steel Wires (PUC–PSWs)

In order to solve the problems of low tensile strength of composite mortar prone to cracking when reinforced concrete beams are strengthened by traditional methods, this paper proposes a new polyurethane concrete–prestressing wire (PUC–PSW) reinforcement method using polyurethane concrete (PUC) as the wire embedding material. Twelve reinforced concrete T-beams were tested for PUC–PSW flexural reinforcement. These consisted of one unreinforced beam, four PSW-reinforced beams and seven PUC–PSW-reinforced beams. The wire embedding material, wire anchorage form, PUC material depth, amount of wire and loading type were used as variables. The test results show that PUC–PSW reinforcement can significantly increase the yield load and ultimate load of the reinforced beams by 24.1% and 44.6%, respectively, compared with PSW reinforcement. When the load reached 90 kN, the crack widths of PSW-reinforced beam A2 and PUC–PSW-reinforced beam A8 were 0.17 mm and 0.1 mm, respectively. The ability of PUC–PSW reinforcement to limit crack development is better than that of PSW reinforcement, especially after the main beam steel yield. The strength, stiffness and crack-limiting ability of the reinforced beam increase with the PUC thickness of the reinforced layer.

The Consequence of the Involvement of Flexural, Compression, and Punching Reinforcement Upon Punching Strength

Flat slabs have an important role in concrete buildings due to their architectural flexibility and speed of construction. Punching shear is one of the most important phenomena to be considered during the design of reinforced concrete flat slabs, as this type of failure is brittle and does not predict previously raised alarms before failure. The main factors that affect punching strength in concrete are compressive strength, flexural reinforcement, and punching reinforcement in the form of stirrups, shear studs, or other shapes. This paper is part of a research program operated at the reinforced concrete laboratory of the Faculty of Engineering, Cairo University, to evaluate the contribution of horizontal flexural reinforcement, horizontal compression reinforcement, and vertical punching reinforcement on the punching strength of reinforced concrete flat slabs. In this research, fifteen half-scale specimens are cast and tested. The specimens had dimensions of 1100×1100 mm and a total thickness of 120 mm. All specimens were connected to a square column of dimensions 150×150 mm and loaded at the four corners with a supported span of 1000 mm. The main parameters considered in this research included spacing between stirrups, width of the stirrups, number of stirrup branches, ratio of the compression reinforcement, and ratio of the tension reinforcement. During testing, ultimate capacity, steel strain, cracking pattern, and deformation were recorded. The experimental results were analyzed and compared against values estimated from different international design codes. Doi: 10.28991/CEJ-2024-010-09-014 Full Text: PDF

Local structural behaviour of the outer containment of an NPP against hard missile impact

An aircraft crash and missile impact on a nuclear containment structure is currently described as an event beyond design basis; however, soon, it will be qualified as a primary design criterion. In the present study, the structural and dynamic behaviour of the outer containment of a nuclear power plant (NPP) has been studied to substantiate its structural integrity against the rigid missile impact. Scaled experiments (at a 1:4 and 1:3 ratio with respect to shell thickness) have been performed to study the localized behaviour of the containment structure against 10 and 20-kg rigid steel projectiles. The reinforced cement concrete (RCC) targets of thicknesses 150 and 200 mm have been subjected to impact at incidence velocity close to the landing and taking of velocity of the aircraft. The flexural reinforcement ratio was considered 1.25 % for a 150 mm thick target and 1.53 % for a 200 mm thick target. The effect of shear reinforcement on the penetration and perforation resistance has been studied for a 200 mm thick RCC target. A detailed post-test examination was conducted to evaluate the localized physical damage characteristics such as spalling and scabbing of concrete, penetration, perforation, crack propagation, and the damage induced in both flexural and shear reinforcements. The mechanics of deformation and failure modes of the target were investigated under varying incidence velocities, 60–115 m/s. The reinforcement characteristics under dynamic loading, such as strain time histories, strain rate sensitivity, and dynamic material properties, were also investigated. The presence of transverse reinforcement in 200 mm thick targets improved the ballistic performance by 12.50 %. Furthermore, the transverse reinforcement also played a crucial role in restricting the bending of the rear face flexural reinforcement and controlling the rear face damage propagation.

Performance Prediction of GFRP-Reinforced Concrete Deep Beams Containing a Web Opening in the Shear Span

This study aimed to investigate the nonlinear structural behavior of concrete deep beams internally reinforced with glass fiber-reinforced polymer (GFRP) reinforcing bars and containing a web opening of various sizes and locations within the shear span. Three-dimensional (3D) numerical simulation models were developed for large-scale GFRP-reinforced concrete deep beams (300 mm × 1200 mm × 5000 mm) with a shear span-to-depth ratio (a/h) of 1.04. Predictions of the numerical models were validated against published experimental data. A parametric study was conducted to examine the effect of varying the opening size and location on the shear response. Results of the numerical analysis indicated that the strength of the deep beam models with an opening in the middle of the shear span decreased with an increase in either the opening width or height. The rate of the strength reduction caused by increasing the opening height was, however, more significant than that produced by increasing the opening width. Placing a web opening in the compression zone close to the load plate was very detrimental to the beam strength. Conversely, a negligible strength reduction was recorded when the web opening was placed in the tension side above the flexural reinforcement and away from the natural load path. Data of the parametric study were utilized to introduce simplified analytical formulas capable of predicting the shear capacity of GFRP-reinforced concrete deep beams with a web opening in the shear span.

Blind competition on the numerical simulation of slabs reinforced with conventional flexural reinforcement and fibers subjected to punching loading configuration

AbstractThis paper describes the 3rd Blind Simulation Competition (BSC) organized by the fib WP 2.4.1 which aims to assess the predictive performance of models based on the finite element method (FEM) for analysis and design of fiber reinforced concrete (FRC) structures submitted to loading and support conditions that promote punching failure mode. Fiber reinforcement is used in an attempt to eliminate conventional punching reinforcement and provide technical and economic advantages. The two tested real‐size prototypes represent a column‐slab interior region of an elevated steel‐fiber reinforced concrete (E‐SFRC) slab where anti‐progressive collapse reinforcement is disposed in the alignment of columns/piles. Despite a punching failure surface being formed in both experimentally tested prototypes at the rupture stage, fiber reinforcement was able to mobilize the yield capacity of the conventional flexural reinforcement, providing high deformation capacity, and ductility to the prototypes. The average post‐peak load‐carrying capacity of the tested prototypes at a deflection seven times higher than the deflection at yield initiation of the conventional reinforcement was still 90% of the average peak load. Regarding the BSC, a total of 26 proposals were received and involved 94 participants from 29 institutions and 17 countries, with 53.9% using smeared crack models (SCMs), 30.8% a concrete damage plasticity (CDP) model, 3.8% discrete crack models (DCMs) and 11.5% considered as “other models.” From these simulations it was verified, in average terms, that SCM assured the best predictive performance apart from the average strain in the SFRC and the maximum crack width which were better predicted by DCM. More accurate predictions were obtained by using in‐house software than by adopting commercial software.

Influence of manufactured sand, recycled aggregate, reinforcement ratio and wire mesh on the response of reinforced concrete slabs under impact loading

Targeting towards the sustainable goal, the emergence of manufacturing sand (M-sand) and recycled coarse aggregate (RCA) as an alternate for natural aggregates has unfolded new prospects for constructional practices in the world. Therefore, the investigation is focused to study the influence of RCA, M-Sand, Combination of RCA and M-sand, wire mesh and steel reinforcement under impact loading. The reinforced concrete slabs (1 layer @ 25 mm c/c) slabs [S1-S4, S9, S11, S13 and S15] was studied using M-sand (100 %) and recycled coarse aggregate (25 %) with a concrete compressive strength of 40–50 MPa. Also, the flexural reinforcement was varied as 0.23, 0.32 and 0.39 % of the cross-section area. The experimental results were presented in terms of failure pattern, impact force-reaction force, midpoint displacement and energy absorption capacity. It was observed that the spalling of concrete to the conventional slab (S1) whereas, the spalling of concrete as well as formation of radial cracks were observed on slab with RCA (S2). It was also observed that the severe spalling with formation of radial cracks in the slab with M-sand and RCA (S4), however the impactor did not perforate. The peak impact force on control slab, S1, S2, S3 and S4 was 145, 187, 122 and 167 kN, respectively. The significant increase in peak impact force in S2 is due to the use of micro silica fume treatment which enhanced the mechanical properties of RCA. The peak impact force in slab S3 by M-sand found reduced by 15 %, whereas the same was found increased by 15 % in case of slab S4 by RCA and M-sand, as compared to S1. The maximum crack width in slab S15 was limited to 1–2 mm whereas same was found to be 9–10 mm in case of slab S13. The use of wire mesh found to enhance the global bending deformations as well as crack width in the slab. It is concluded that the utilization of wire mesh along with steel reinforcement proves to be an effective method to diminish the permanent deformation. Further, finite element software ABAQUS was used to model the slab under impact loading and the results were compared with the experimental results. The predicted peak impact force of slab S1 was found to be good agreement with the experimental results. However, the predicted peak impact force on slab S2-S4 found to have maximum deviation 11 % as compared to experimental results.

Effect of Recycled Concrete Aggregates on the Concrete Breakout Resistance of Headed Bars Embedded in Slender Structural Elements

Recycled concrete aggregates are potentially interesting for the precast concrete industry as they provide a new use for high-quality waste from its products’ life cycle. In precast concrete structures, it is common to use headed bars in several connection types between structural members. This paper presents the results of experimental tests to investigate the impact of replacing coarse natural aggregates with coarse recycled concrete aggregates in the concrete breakout strength of cast-in headed bars embedded in slender structural elements. Results of 12 tests on 16 mm headed bars embedded in 500 × 200 × 900 mm concrete members with an effective embedment depth of 110 mm are presented. The percentage of replacement of natural aggregates by recycled concrete aggregates was 0%, 30%, and 100%, and the flexural reinforcement ratio of the structural elements varied from 0.5% to 3.5%. The behavior and strength of the tested specimens are discussed, and comparisons with theoretical strength estimates are presented. The results showed that the concrete breakout strength of the headed bars was not affected by the use of recycled concrete aggregates and that the flexural reinforcement ratio significantly impacts the load-carrying capacity of the headed bars as they control the crack widths before failure.

Enhancing Flexural Behavior of Reinforced Concrete Beams Strengthened with Basalt Fiber-Reinforced Polymer Sheets Using Carbon Nanotube-Modified Epoxy.

The external bonding (EB) of fiber-reinforced polymer (FRP) is a usual flexural reinforcement method. When using the technique, premature debonding failure still remains a factor of concern. The effect of incorporating multi-wall carbon nanotubes (MWCNTs) in epoxy resin on the flexural behavior of reinforced concrete (RC) beams strengthened with basalt fiber-reinforced polymer (BFRP) sheets was investigated through four-point bending beam tests. Experimental results indicated that the flexural behavior was significantly improved by the MWCNT-modified epoxy. The BFRP sheets bonded by the MWCNT-modified epoxy more effectively mitigated the debonding failure of BFRP sheets and constrained crack development as well as enhanced the ductility and flexural stiffness of strengthened beams. When the beam was reinforced with two-layer BFRP sheets, the yielding load, ultimate load, ultimate deflection, post-yielded flexural stiffness, energy absorption capacity and deflection ductility of beams strengthened using MWCNT-modified epoxy increased by 7.4%, 8.3%, 18.2%, 22.6%, 29.1% and 14.3%, respectively, in comparison to the beam strengthened using pure epoxy. It could be seen in scanning electron microscopy (SEM) images that the MWCNTs could penetrate into concrete and their pull-out and crack bridging consumed more energy, which remarkably enhanced the flexural behavior of the strengthened beams. Finally, an analytical model was proposed for calculating characteristic loads and characteristic deflections of RC beams strengthened with FRP sheets, which indicated a reasonably good correlation with the experimental results.

Fatigue Behavior of Flexural Reinforced Concrete Beams under Corrosion Conditions

Fatigue Behavior of Flexural Reinforced Concrete Beams under Corrosion Conditions

Effect of GFRP bar length on the flexural behavior of hybrid concrete beams strengthened with NSM bars

Abstract This project aims to investigate the effect of near-surface-mounted glass fiber reinforced polymer (GFRP) bars strengthening on the flexural behavior of hybrid reinforced concrete beams. Seven beams were made; one of these specimens had no strengthening and is considered as a reference beam. The other models were strengthened using near-surface-mounted GFRP bars at the bottom of beams with different lengths (0.5, 0.75, and 1) of effective span beams and diameters (8 and 12 mm) of GFRP bars. The beam length was 2,200 mm with 150 mm width and 240 mm depth. The flexural reinforcement consists of 2 φ12 steel bars at the tension zone and 2 φ12 at the compression zone for all beams. Furthermore, to resist shear forces, φ12 steel bars were used, distributed along the length of the beams spaced at 125 mm c/c; two-point loads on the beams with 500 mm between them were applied at the mid-span. The investigated characteristics were cracking and failure load, crack width, deflection, and failure patterns. By examining the models, it was found that there is an improvement in failure load range from 11.54 to 53.84% relative to the control.

A design methodology for fibre reinforced concrete elements in serviceability conditions integrating tension softening and stiffening effects

This paper proposes a design methodology to derive an analytical bilinear moment‒curvature diagram (Mana–χana) for the cross-section of fibre reinforced concrete (FRC) elements that also includes conventional steel flexural reinforcement (R/FRC). This bilinear diagram is obtained by determining the post-cracking tensile capacity of FRC (NtcFRC), which integrates not only the tensile stiffening capacity of the FRC surrounding the conventional flexural reinforcement due to the bond stress transference between this reinforcement and FRC, but also the tensile softening of the cracked FRC out of this zone. This Mana–χana is defined by two points, the first corresponding to the cracking moment and its corresponding curvature (Mcrana,χcrana), while the bending moment of the second point of this diagram (Muana) is a multiple of the analytical cracking moment (CuMcrana), where Cu is dependent on the fibre volume percentage (Vf). The curvature corresponding to Muana,χuana, is obtained by assuming the flexural stiffness of a fully cracked RC section. Therefore, the Mana–χana is determined by geometric and material properties of directly assessed by a designer.For demonstrating the applicability of the proposed design methodology, a database of beams of distinct cross-section aspect ratios and compressive strength classes, reinforced with different percentages of steel fibres and reinforcement ratios of conventional steel bars was established. By using the bilinear Mana–χana, and applying the principle of virtual work, the deflection of these beams was estimated with sufficient accuracy for design purposes, when compared to experimental records. Although the formulation has been applied to beams made by steel fibre reinforced concrete (SFRC), it is conceptually general and applicable to elements of concrete reinforced with other types of fibres.

Elasto-Plastic Analysis of Two-Way Reinforced Concrete Slabs Strengthened with Carbon Fiber Reinforced Polymer Laminates

This study explores a technique for enhancing the punching strength of reinforced concrete (RC) flat slabs, namely carbon fiber reinforced polymer (CFRP). Four large-scale RC flat slabs were fabricated, to assess the efficacy of this strengthening method. One slab served as a reference and the three other specimens were strengthened with CFRP, as a method of external strengthening. These slabs, featuring identical overall dimensions and flexural steel reinforcement, underwent testing until failure, under the influence of concentrated patch loads. A concrete plastic damage constitutive model (CDP) was developed and employed to examine the strength of two-way RC slabs. Additionally, to enhance the strength of existing RC slabs, carbon fiber reinforced polymer (CFRP) strips are affixed to the tension surface of the sections. The research begins with the calibration of a numerical model, based on data from laboratory tests. The objective of this study is to constrain the plastic behavior of two-way RC slabs reinforced with CFRP, with a focus on establishing an optimal elasto-plastic analysis, aimed at controlling concrete damage plasticity using CFRP, and employing a plastic limit load multiplier. Subsequently, a series of numerical simulations, incorporating different variables, are conducted to investigate shear behavior. The numerical results indicate that an increase in the strengthening ratio has a significant impact on shear strength. Finite element simulations are carried out using Abaqus CAE®/2018.

Seismic Response of RC Beam-Column Joints Strengthened with FRP ROPES, Using 3D Finite Element: Verification with Real Scale Tests

A 3D-finite element analysis within the numerical program ABAQUS is adopted in order to simulate the seismic behavior of reinforced concrete beam-column joints and beam-column joints strengthened with CFRP ropes. The suitability of the adopted approach is investigated herein. For this purpose, experimental and numerical cyclic tests were performed. The experiments include four reinforced concrete (RC) joints with the same ratio of shear closed-stirrup reinforcement and two different volumetric ratios of longitudinal steel reinforcing bars. Two joints were tested as-built, and the other two were strengthened with CFRP ropes. The ropes were applied as Near Surface Mounted (NSM) reinforcement, forming an X-shape around the joint body and further as flexural reinforcement at the top and bottom of the beam. The purpose of the externally mounted CFRP ropes is to allow the development of higher values of concrete principal stresses inside the joint core, compared with the specimens without ropes, and also to reduce the developing shear deformation in the joint. From the results, it is concluded that X-shaped ropes reduced the shear deformation in the joint body remarkably, especially in high drifts. Further, as a result of the comparisons between the yielded outcome from the attempted nonlinear analysis and the observed response from the tests, it is deduced that the adopted method sufficiently describes the whole behavior of the RC beam-column connections. In particular, comparisons between experimental and numerical results of principal stresses developing in the joint body of all examined specimens, along with similar comparisons of force displacement envelopes and shear deformations of the joint body, confirmed the adequacy of the applied finite element approach for the investigation of the use of CFRP-ropes as an efficient and easy-to-apply strengthening technique. The findings also reveal that the connections that have been strengthened with the FRP ropes demonstrated improved performance, and the crack system preserved its load capacity during the reversal loading tests.

Punching shear tests in flat slabs supported on re-entrant corner columns

The punching strength and deformation capacity of slab-column connections is governing for design at ultimate limit state of flat slabs. This phenomenon has been investigated since decades with experimental programmes in an effort to derive empirical or mechanical design approaches. Such efforts, due to the complexity of the phenomena, have mostly been addressed to axisymmetric inner slab-column connections, which correspond to the simplest academic case and are not directly covering a large variety of practical situations. Although some tests are also available for other configurations, such as edge or corner connections, no experimental evidence is found on relevant cases for practice such as re-entrant corner columns. The lack of experimental data in this latter case raises questions on the design of such connections, as extrapolating results from other cases is not a simple task due to the complexity of the phenomena implied (such as redistributions in the shear field and moment transfer between slab and column). In order to advance the knowledge on the response of re-entrant connections and to provide a sound design approach for them, this paper presents the results of an investigation specifically addressed at this case. To that aim, seven specimens were tested under different conditions, varying the load eccentricity, flexural reinforcement and shear reinforcement arrangement at the edges. The tests were instrumented with refined measurements, allowing to understand in a detailed manner the response of the slabs during testing in the shear-critical region. The experimental results are later compared to current design codes, leading to a number of conclusions with practical relevance. Finally, on the basis of the knowledge acquired from the tests, a mechanical approach is proposed based on the Critical Shear Crack Theory to assess the punching response. This approach is shown to lead to accurate and reliable predictions of the punching strength, improving those of current design codes.

Mechanical performance and structural application of a novel basalt‐fiber‐reinforced ultra‐high‐performance seawater‐sea‐sand concrete (UHPSSC) with basalt coarse aggregate

AbstractAs unlimited resources, seawater and sea sand (SS) could be used as alternatives for fresh water and river sand in concrete constructions in areas with limited resources, such as mega‐cities and islands. To further improve the material efficiency, SS have been used to fabricate the ultra‐high‐performance seawater‐sea‐sand concrete (UHPSSC) in the literature. This work proposes a new type of UHPSSC, which incorporates basalt fibers to enhance the tensile property and coarse aggregate (CA) to improve the modulus. To investigate the contributing factors to the mechanical performance, 12 mixes of different fiber lengths, fiber volumes, and CA contents were designed and tested under compression and flexure. To verify the validity of the proposed UHPSSC in structural elements, six beam specimens reinforced with basalt‐fiber‐reinforced polymer (BFRP) bars were designed and tested. The influence of the tensile properties of the proposed UHPSSC and BFRP flexural reinforcement designs was analyzed. This research shows that with a proper mix design, the proposed UHPSSC has a maximum compressive strength of 140 MPa, exceeding the benchmark strength of 120 MPa for ultra‐high‐performance concrete. With different mix designs, the compressive strength of the proposed UHPSSC varies from 101.5 to 140.5 MPa and the flexural strength varies from 10.8 to 15.4 MPa at 28 days. At different curing ages, the basalt fiber length and volume have more significant impacts on the flexural strength but have limited impact on the compressive strength. Although an optimal CA content of 400 kg/m3 was found for the compressive strength and the CA content could amplify the influences of the fiber length and volume on the flexural strength. With the flexural reinforcement ratio varying from 0.58% to 1.29%, the UHPSSC beam specimens failed with expected flexural failure and the ultimate capacities varying from 118 to 183 kN, showing a predictable manner. Improving the tensile strength of the proposed UHPSSC could effectively enhance the cracking load and expand the stiffness degradation phase.

SHEAR RESISTANCE OF OIL PALM SHELL REINFORCED CONCRETE BEAMS CAST WITH SHEAR REINFORCEMENT

Research on the use of Oil Palm Shell (OPS) to replace coarse aggregates in concrete to date has been focusing on the material properties of oil palm shell concrete (OPSC). So far, there has been a very limited amount of work conducted to investigate the shear performance of the OPSC beams indicating similar shear strength to that of normal-weight concrete (NWC) beams. This study investigates the shear failure mechanism of OPSC beams cast with shear reinforcement. The test results recorded from 11 OPSC beams and 5 NWC beams, simply supported with two-point loads, are presented. The variables considered include the concrete compressive strength, flexural reinforcement, shear-span, and shear-link spacing. The observed shear failure mechanism of OPSC beams was found to be similar to that of an NWC beam while the shear crack formation and shear resistance of OPSC beams are slightly higher (3% to 14%) and (4.2% to 8.5%), respectively. Comparative studies using the current provisions of EC2 and BS8110 have been performed and found that both codes’ predictions, show good agreement with only a slight overestimation (VTest/VBS of 0.988) on the shear resistance, were consistent with the tests.

Performance of the Pivot Hooks to Enhance the Flexural Capacity of Bamboo Reinforced Concrete Beams

Some researcher missed the role of hooks in their bamboo reinforcement. Consequently, the bamboo reinforcement and concrete used to have slip and failure to composited, this make the concrete and bamboo working independently to sustain the given loading and the bond failure become the main issue than the beam failure. This research studied about the role of the pivot hooks that capable to enhance the loading capacity higher than the beams without the pivot hooks. Experimental test performed in order to identify the effect of the pivot hooks presence which added to the flexural reinforcement which made by bamboo materials to avoid the bond slip failure that mostly occur in the bamboo reinforced concrete beams. The experimental test which verified by the numerical analysis by FEA NX commercial software proof that the pivot hooks are able to increase the loading capacity of a concrete beam 33% - 40% higher than the bamboo reinforcement without the pivot hooks. Architectural façade and budget efficiency caused the bamboo become unavoidable material in construction, by adding the structure modification such as the pivot hooks for the bamboo reinforcement, the failure can be reduced, then the entanglement of bamboo in construction become more functional.

ONE-WAY SLABS IN TRANSITION BETWEEN ONE-WAY SHEAR AND PUNCHING: EXPERIMENTS AND RECENT INSIGHTS FOR EVALUATION

Bridge deck slabs are members on which one-way reinforced concrete slabs are found frequently loaded by concentrated loads. Although the one-way shear failure mechanism has gathered more attention in the past years, both one-way shear and two-way shear mechanisms may be critical for such loading conditions. This paper addressed the ultimate capacity of thin one-way reinforced concrete slabs subjected to concentrated loads and yielding of the flexural reinforcement. In practice, the test setup studied was devised to represent short-span rural bridges frequently found in Brazil. The experimental program included 12 tests performed on 6 slabs applying the concentrated loads at varied positions. All tests started to fail by punching shear. Nevertheless, both one-way shear and punching shear cracks were observed at ultimate states after shear redistribution. The reinforcement yielding followed by excessive flexural cracking hampered the arching action activation for loads closer to the support. The comparison of experimental and calculated resistances using standard code-based expressions suggests that improvements in unitary shear capacity could be supported as a result of slabs' transverse load distribution capacity. Alternatively, increasing the effective shear width can help estimate one-way shear capacity for loads near to the support.