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A reinforced concrete beam with a recess is an example of a non-prismatic beam, which develops stress concentrations at the corner of the recess owing to the abrupt change in its depth. This entails appropriate detailing of internal reinforcement in order to avoid premature failure. This study presents the load transfer mechanism employing the strut-and-tie model (STM) for four non-prismatic beams with recesses in the shear span zone at both compression and tension sides, tested under a four-point loading scheme. The proposed STMs for the tested beams were developed based on both the cracking patterns near failure of experimentally tested beams and the developed stress contours based on linear static analysis. In addition, a simplified method is proposed to estimate the maximum mid-span deflection of simply supported beams with recesses. The results obtained reveal that the STM gave good predictions, with an average of about 86% of the ultimate experimental loads. Based on the results of the parametric study conducted, it was found that the most significant parameter was the recess depth from the viewpoint of stress concentration factor, cracking load and maximum crack width. Finally, recommendations and guidelines for the design of reinforced concrete beams with recesses are presented. [ABSTRACT FROM AUTHOR]

This paper presents the results of both experimental and numerical investigations on the overall structural performance of two-equal-span reinforced concrete perforated (castellated) beams subjected to external pre-stressing. First, the effects of providing castellated openings along with the application of external pre-stressing on both the ultimate capacity and the percentage of moment redistribution were investigated experimentally. Then, after validation of the numerical modelling, the effects of controlling the parameters on the percentage of moment redistribution were investigated numerically. Experimental results showed that providing castellated openings accelerated the appearance of both flexural and shear cracks, and decreased the ultimate capacity by about 24% compared to that of a solid beam. Moreover, application of external pre-stressing on the castellated beam compensated for the reduction in ultimate capacity and outperformed it by about 9% compared to that of a solid beam. Based on the numerical results, it appears to be better to increase the amount of main tensile steel and strand eccentricity at the hogging moment zone, as well as increase the effective pre-stressing force, to reduce the percentage of moment redistribution at both sagging and hogging moments. [ABSTRACT FROM AUTHOR]

Fibre-reinforced polymer bars are rapidly becoming an approved alternative to conventional reinforcing steel bars, especially for severely exposed structures such as bridges. This paper reports on an experimental study on the bond characteristics of both sand-coated and ribbed-surface glass-fibre-reinforced polymer bars embedded in high-strength concrete (HSC). A total of 145 pull-out tests were conducted to examine the effect of varying parameters on the bond characteristics, namely embedment length, bar diameter, surface treatment and concrete cover. In addition, 45 pull-out tests were conducted to investigate the effect of providing headed-end anchorage for the sand-coated bars. The experimental results showed that the sand-coated bars exhibited better bond strength than the ribbed-surface bars, which entailed lower development lengths. Thus, based on the experimental results, expressions for the development length of both sand-coated and ribbed-surface bars embedded in HSC were developed and compared against the results of formulae in available design standards. The comparison revealed that ACI 440-1R-06 produced lower conservative results than CAN/CSA S806-12. [ABSTRACT FROM AUTHOR]

Two configurations of closure strips between precast reinforced concrete (RC) slab panels were fabricated and filled with either non-shrink grout or ultrahigh-performance strain-hardening cementitious composite (UHP-SHCC) material. The strips were then strengthened with externally bonded carbon-fibre-reinforced polymer (CFRP) sheets in order to compensate the drawback associated with decreasing the amount of connected steel reinforcing bars required to transfer the bending moment between panels. In total, 12 specimens divided into three groups were cast and tested under short-term non-reversed repeated patch loads simulating wheel load at the central joint. The test results showed that the UHP-SHCC filling material enabled the connected panels to exhibit more ductile behaviour compared with the panels whose closure strips were filled with non-shrink grout. On the other hand, the CFRP strengthening sheets for the first configuration of the closure strip failed to restore the ultimate capacity of the un-strengthened monolithic specimen. However, the second configuration, using UHP-SHCC filling material, enabled the connecting panels to restore lost capacity, with a performance improvement of about 14% compared with the un-strengthened monolithic specimen. [ABSTRACT FROM AUTHOR]

This paper presents the experimental findings for different strengthening techniques applied on defected reinforced-concrete cantilever slabs to restore lost flexural capacities owing to insufficient bond length of the main tensile steel. The restoration technique was based on compensation of the main tensile steel by near-surface mounted steel bars, externally bonded steel plates or externally bonded carbon fibre-reinforced polymer sheets. In addition, new hybrid techniques are presented, which merge the traditional techniques with a 20 mm thick ultra-high-performance strain-hardening cementitious composites (UHP-SHCC) layer. It was found that the strengthening technique based on the embedded steel bars on the UHP-SHCC overlay enabled the strengthened slab to restore its lost capacity and outperformed it by about 5% compared to that of the properly detailed slab. Nevertheless, this restoration was at the expense of the exhibited ductility. Conversely, the strengthening technique based on the application of externally bonded steel plates on a transition layer of the UHP-SHCC material enabled the strengthened slab to restore the lost capacity by about 96% as well as to outperform its ductility by more than 29% compared to those of the properly detailed slab. [ABSTRACT FROM AUTHOR]

Impact loading could impair the entire structure or a part of it, thus making the human life at stake. In this study, to improve the impact resistance of reinforced concrete slabs under drop-weight loading, a thin layer of strain-hardening cementitious composites was added at either tension or compression side of the slab. The main parameter of this study was the three contact surface conditions, namely grinding, grinding plus steel dowels, and grinding plus epoxy adhesive, between the substrate slab and the strain-hardening cementitious composites layer. Therefore, 63 reinforced concrete slabs were prepared and tested under the effect of drop-weight falling from three different heights: 1, 1.5, and 2 m. In addition, for comparison purposes, additional seven slabs were tested under central incremental static loading until failure is presented. It was found that the strain-hardening cementitious composites–strengthening layer enhanced the impact and static response of the strengthened slabs when added at either tension or compression side. Besides, to achieve the outermost impact resistance showing ductile performance, it is better to provide a thin layer of the strain-hardening cementitious composites at the tension side of the slab connected to the substrate slab by epoxy resin applied on pre-prepared grinded surface. [ABSTRACT FROM AUTHOR]

The main target of this article is to find out the most applicable strengthening technique to change the brittle punching shear failure of slab–column connection to a ductile one. The considered strengthening technique uses the combined effect of the internal single-leg stirrups and a thin layer of ultra-high-performance strain hardening cementitious composite material provided in either tension or compression side. Thus, 12 slab specimens divided into four groups were prepared and configured. It was found that the slab provided with properly anchored single-leg stirrups with a cross-shaped thin layer of ultra-high-performance strain hardening cementitious composite material at the compression side proved the most efficient technique among all the considered configurations. This technique enabled the slab to sustain a punching load of about 2.38 times that of the control unstrengthened slab. In addition, it exhibited ductile failure showing strain hardening and softening plateaus. Finally, the experimental shear resistances of all the strengthened slabs were compared against the design resistances stipulated by different design standards such as the ECP 203-2007, ACI 318-14, DIN 1045-1, and EC2-2004 codes. It can be concluded that the failure characteristics stipulated by the DIN 1045-1 code showed the most rational results compared with those of the experimental findings. [ABSTRACT FROM AUTHOR]

Experimental findings and detailed analyses of the overall structural performance of properly detailed and strengthened reinforced concrete (RC) frame structures with defects are presented. Two strengthening techniques were implemented on the faulty frame structures in order to restore lost capacity due to improper detailing of the main tensile steel for both closed- and open-jointed frame systems. The strengthening techniques implemented were near-surface mounted (NSM) steel bars and external un-bonded prestressed steel bars. Three defects were considered, two of them pertaining to frame structures with closed joints and one pertaining to open-jointed frame structures. In total, 11 RC frame specimens divided into four groups were configured, casted and then tested until complete collapse under monotonic incremental loading. It was found that strengthening based on external prestressed bars had a significant effect on both the ultimate capacity and developed ductility of strengthened open-jointed frame structures, while its effect on closed-jointed frame structures was small. For the closed-jointed frame structures, strengthening with NSM steel bars produced greater enhancement in ultimate capacity than the prestressed bar strengthening technique. [ABSTRACT FROM AUTHOR]

This paper investigates experimentally and analytically the shear performance of RC beams made of recycled coarse aggregate (RCA). Previous studies showed that the partial replacement of the virgin coarse aggregate by recycled one results in decrease the shear strength of RC beams. Consequently, the main target of the this research was to compensate such decrease in the shear strength by providing internal short fibers and using cured recycled coarse aggregate instead of crude recycled coarse aggregate. A total of eleven simply supported RC beams made of recycled coarse aggregate along with one conventional concrete beam were tested under incremental four-point loading scheme. The considered parameters were the recycled coarse aggregate replacement ratio (15, 30 and 45%), the shear span-to-depth ratio (1, 2 and 3) and the fiber volumetric ratio (1, 1.5 and 2%). In addition, to improve the physical and mechanical properties of the recycled coarse aggregate (RCA), two curing methods for the RCA were implemented using cement slurry and Styrene Butadiene Rubber (SBR) compound. The experimental results showed that increasing the replacement ratio of the RCA resulted in decrease the shear capacity proportionally. The percentages of decreases in the shear capacities were about 8%, 14% and 19%, respectively, for RC beams provided by RCA replaced by 15%, 30% and 45%. In addition, it was shown that providing internal short fibers by volumetric ratios of 1%, 1.5% and 2% enabled the RC beams made of 30% partial replacement of the recycled coarse aggregate to compensate the decreases in the shear capacities (14%) and to increase their shear capacities by about 13%, 15% and 22% compared to those of the control beam, respectively. Furthermore, for RC beams made of 30% partial replacement of the RCA, the shear capacities decreased by about 2%, 14% and 37%, respectively, for beams having shear span-to-depth ratio of 1, 2 and 3. Besides, it was shown that, the cured recycled coarse aggregate enabled the RC beams made of 30% partial replacement to exhibit improved shear performance. However, the curing method based on cement slurry showed higher improvement since the restored shear capacities were about 15% and 3% for beams provided by cured coarse aggregate based on cement slurry and compound SBR, respectively compared to that of the beam made of crude RCA. Finally, an equation for estimating the shear capacity of RC beams made of recycled coarse aggregate was proposed and it showed satisfactory results when verified against the experimental findings of the current research as well as of other researches where the maximum variations were about 8.5% and 22%, respectively. [ABSTRACT FROM AUTHOR]

The current paper presents an experimental study in order to verify the flexural performance of a new developed perforated beam system. This system facilitates passing the pipes of utility services through its perforations as well as it has a good-looking appearance. Three main factors were studied; namely, the percentage of mass loss (14% 19% and 26%) due to the provided perforations, the reinforcement configurations around the perforations (orthogonal reinforcement, circular stirrups, and cross-bars) and the perforations shape (circular and oval). Therefore, three perforations sizes were studied having perforation diameter to the beam total depth ratio (D/t) of 0.38, 0.50, and 0.62. Accordingly, six perforated beams along with one solid reference beam were prepared and configured then tested under repeated loading till complete collapse. It could be concluded that the perforated beams of 200 mm perforations diameter (D/t = 0.5) reinforced by circular stirrups and cross-bars showed approximately the same flexural capacity as that of the solid beam but cross-bars stirrups enabled the perforated beam to develop approximately the same ductility as that of the solid beam. While, the beam with circular perforations (D/t = 0.5) provided by orthogonal reinforcement manifested increased flexural capacity by about 31% compared to that of the solid beam, while the developed ductility was lower than that of the solid beam by about 55%. In addition, the ductility could be outperformed by about 21% keeping the same ultimate capacity compared to those of solid beam provided that the mass loss of 14% was achieved as showed by the perforated beam with 150 mm perforations diameter (D/t = 0.38). [ABSTRACT FROM AUTHOR]

Multi spine composite concrete-deck steel-box girder bridges became a very popular choice in highway bridges due to their high torsional and wraping stiffness as well as for economic and aesthetic reasons. This study presents an experimental investigation on both elastic and ultimate behavior of composite box girder bridges in order to study the effect of internal cross bracing between box girders along with the curvature effect at different loading stages. Three composite concrete deck-steel simply-supported twin-box bridge models, two curved and one straight, were fabricated, and tested. First, the response of each model was monitored under free-vibration excitation, then an eccentric loading was applied and the corresponding deflections were recorded in the elastic range. Finally, the bridge models were tested up to collapse. The structural behavior of the three bridge models was compared at the three loading stages. It was noticed that the presence of an external cross bracing system between the steel boxes had an insignificant effect on the developed deflection and the fundamental natural frequency in the elastic range of loading. On the other hand, these external bracings assisted in decreasing the developed deflection approaching failure and in increasing the load carrying capacity by about 8.9%. In addition, the external bracing ensured a better distribution of the stresses under ultimate loading conditions. Moreover, the experimental findings were verified numerically using finite element modeling. A good agreement was noticed to exist between the experimental findings and the numerical results. [ABSTRACT FROM AUTHOR]

Because of columns loads, reinforced concrete (RC) continuous beams in skeleton structures are subjected to transverse compressive stress at support locations. Such lateral pressure can enhance the bond between the main top reinforcing bars and the surrounding concrete because of the confinement effect. Thus, the development length can be reasonably decreased compared to the case of no lateral pressure. However, different codes of practice, such as the Egyptian code standard ECP 203-2007 and the American Concrete Institute (ACI) code standard ACI 318-11, stipulate increasing the reinforcement location factor for upper reinforcement implemented in the calculation of the development length of such bars. On the other hand, the Comite Euro-International du Béton (CEB-FIP) model code standard CEB-FIP 2010 considers this enhancement in bond stress calculations as being due to transverse compression stress. To assess such effects, pull-out tests were performed on reinforcing bars embedded in short RC columns subjected to different levels of axial pressure. The experimental findings showed the same trend as manifested in the CEB-FIP 2010 results, where increasing the lateral pressure on the reinforcing bar resulted in decreasing the development length for both smooth and deformed steel bars. In contrast, the results of development length calculations based on both ECP 203-2007 and ACI 408R-03 were constant regardless of the level of lateral pressure on the reinforcing bar. This highlights the need for both ECP 203-2007 and ACI 408R-03 to consider the effect of transverse lateral pressure on development length calculations due to varying lateral pressure on the reinforcing bar. [ABSTRACT FROM AUTHOR]

Precast prestressed double-tee (DT) girders are considered a crucial element of modern infrastructure used to accelerate building construction worldwide. These girders can be deficient because of local damages and develop cracks as a result of improper transportation and handling. Therefore, it is very important to develop an efficient retrofitting technique in order to restore the lost capacity and/or even outperform it. The objective of this paper is to develop retrofit strategy of the deficient girders using the externally bonded carbonfiber- reinforced polymer (EB-CFRP) technique and verify it using field data. A field test was conducted on three actual-size precast pretensioned DT girders having different levels of damage and retrofitted using CFFP sheets. The girder stems for two of them were strengthened in flexure using unidirectional U-shaped CFRP sheets, while all girders were shear-strengthened at their dapped ends. Each girder was loaded incrementally up to collapse while the deflection of the girder and normal strains developed on both concrete surface and the CFRP sheets were recorded at each load increment. Test results assured the adequacy of the adopted strengthening technique with respect to both ultimate capacity and ductility. In addition, the experimental flexural and shear resistances of the retrofitted girders are far greater than those obtained from equations available in design codes by at least 60%. [ABSTRACT FROM AUTHOR]

This paper presents experimental and analytical studies on the flexural behavior of fully composite steel-concrete I-girders strengthened by externally bonded carbon fiber reinforced polymer (EB-CFRP) sheets. The experimental program consisted of four reduced-scale specimens composed of a hot-rolled steel I-girder section acting compositely with topping reinforced concrete slab using two rows of properly designed shear studs along the entire length of the girder flange. One girder was un-strengthened to act as a reference girder, while the remaining three girders were strengthened with 2, 3 and 4 layers of CFRP sheets mounted on the bottom side of the steel girder's tension flange considering complete anchorages of the CFRP sheets at both ends. The composite girders were tested under a four-point loading system in order to obtain a comprehensive overview of the flexural behavior of both un-strengthened and the CFRP-strengthened girders. Finally, an analytical design procedure was proposed in order to obtain the moment of resistance of the composite girders. Then, the proposed methodology was verified against the current experimental results as well as the experimental results obtained by other researchers. The comparison showed good agreement between the proposed analytical results and the experimental findings with a maximum variation less than 10%. Thus, the proposed equations for moment of resistance of CFRP-strengthened composite girders can be used by design engineers with confidence. [ABSTRACT FROM AUTHOR]

Reinforced concrete broken slab presents a crucial element that exists in all multi-story buildings. Normally, it can be used as the flight of the stair. In many cases such element is in urgent need for strengthening or upgrading due to change of the usage or any construction errors. The current paper presents three different strengthening strategies for opened-joint broken slabs in the aim of doubling their flexural resistance. The adopted strategies were the application of Externally Bonded Carbon Fiber Reinforced Polymer (EB-CFRP) sheets, adding thin layer of Ultra High-Performance Strain-Hardening Cementitious Composites (UHP-SHCC), and the application of hybrid system integrated both former techniques. The studied parameters were the anchorage system of the CFRP sheets at the opened-joint as well as the connection between the substrate slab and the UHP-SHCC layer. Based on the overall structural performance and exhibited ductility, the application of properly anchored EB-CFRP sheets on a well-connected UHP-SHCC layer enabled the substrate broken slab to exhibit the most favorable behavior. Finally, a new stitching procedure was proposed in order to construct a precast slab similar to a monolithic one and then strengthened using the same strengthening strategies. Its performance showed comparable results against the results of the monolithic broken slab. [ABSTRACT FROM AUTHOR]

This paper aimed to develop and evaluate an efficient strengthening method for reinforced concrete beams, based on engineered cementitious composites (ECC) to be applied as a transition layer prior to the application of the carbon fibre-reinforced polymer (CFRP) strengthening sheet. The role of the proposed transition layer is to control the cracking of concrete and detain or even avoid premature de-bonding of the strengthening CFRP sheets. As the ability of the transition layer to exhibit a strain hardening behaviour is mainly dependent on the used fibre volumetric ratio, three ECC mixes with three different polypropylene fibre volumetric ratios were used (fibre volumetric ratio of 0.5%, 1% and 1.5%). The experimental results showed that while the used CFRP strengthening sheet can increase the ultimate load by about 28.8% compared with the control un-strengthened beam, this increase can reach about 48.5% by applying the same CFRP sheet to the proposed ECC transition layer that contains a fibre volumetric ratio of 1.5%. Moreover, this layer integrated with the mention ratio of the fibre content enabled the CFRP sheet to be in a complete contact with the strengthened beam without any de-bonding up the rupture of the CFRP sheet at failure. [ABSTRACT FROM AUTHOR]

Glass Fiber Reinforced Polymer (GFRP) bars as a proper substitute for traditional reinforcing steel bars not only eliminate the durability problem due to corrosion of reinforcing steel, but also provide remarkably enhanced capacity due to their high tensile strength compared to that of the steel bars. This paper presents the experimental findings of 180 pullout tests conducted on GFRP bars embedded into high-strength concrete blocks covering different parameters. The studied parameters were bar diameter size (12 or 16 mm), embedment length (4 or 6 times the bar diameter), bar end condition (straight and headed), and concrete cover (1.5, 2.5, and 5 or 7 times bar diameter for straight bars and 8 or 10.5 times bar diameter for headed bars) in addition to a case of no embedment length except the head length for headed-end bars. In total, 30 variables were studied, while each variable was conducted on 6 identical specimens in order to increase the reliability of the results. Based on the results of the parametric study, the bond stress was shown to be inversely proportional to the embedment length and bar diameter as expected. In addition, the smaller concrete cover appeared to have significant effect on bond stress, leading to side blow-out failure rather than bar pullout or concrete splitting in the case of headed-end GFRP bars. In addition, the GFRP bar with headed-end showed significant increase in pullout strength compared to that for the straight-end bars. Finally, an empirical expression was proposed to calculate the development length of GFRP bars with either straight or headed-end, and then compared with the available design standards such as CSA-S806-02, CSA S6-06, ACI 440-1R-06, and JSCE-97. The comparison showed that the results developed by CSA S6-06 standards was the closest to the experimental findings showed about 2% safety margin exceeding the obtained development length by the proposed expression. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an experimental study for the structural performance of reinforced concrete (RC) exterior beam–column joints rehabilitated using carbon-fiber-reinforced polymer (CFRP). The present experimental program consists of testing 10 half-scale specimens divided into three groups covering three possible defects in addition to an adequately detailed control specimen. The considered defects include the absence of the transverse reinforcement within the joint core, insufficient bond length for the beam main reinforcement and inadequate spliced implanted column on the joint. Three different strengthening schemes were used to rehabilitate the defected beam–column joints including externally bonded CFRP strips and sheets in addition to near surface mounted (NSM) CFRP strips. The failure criteria including ultimate capacity, mode of failure, initial stiffness, ductility and the developed ultimate strain in the reinforcing steel and CFRP were considered and compared for each group for the control and the CFRP-strengthened specimens. The test results showed that the proposed CFRP strengthening configurations represented the best choice for strengthening the first two defects from the viewpoint of the studied failure criteria. On the other hand, the results of the third group showed that strengthening the joint using NSM strip technique enabled the specimen to outperform the structural performance of the control specimen while strengthening the joints using externally bonded CFRP strips and sheets failed to restore the strengthened joints capacity. [Copyright &y& Elsevier]

• The most efficient reinforcement configuration for RC castellated beams is outlined. • The behavior of RC castellated beams having large castellation is investigated experimentally. • The effect of external pre-stressing is studied experimentally. • Effects of castellation size and web post length are investigated numerically. • Empirical expression for the ultimate capacity of RC castellated beams is proposed and verified against numerical results. Introducing web openings in reinforced concrete (RC) beams became a common practice in order to provide easy passage ways for facility services. These openings can take any shape; however the most popular shapes are the square, the rectangular and the circular ones. In spite that the hexagonal shape (castellated) is normally used in steel beams, it is rarely used in reinforced concrete beams. Owing to the good appearance of the hexagonal shape, the flexural behavior of RC beams having multi-hexagonal openings (castellated beams) has been investigated. First, the most efficient reinforcement configuration of the castellated beams was chosen based on numerical sensitivity analysis. Then, the overall flexural performance of both monolithic and pre-stressed concrete castellated beams has been studied experimentally. Finally, a parametric study on the castellation size and web-post length has been carried out numerically in order to obtain a rational expression for estimating the ultimate capacity of castellated beams taking into account the controlling parameters. The numerical simulation of castellated beams provided the best internal reinforcement configuration from the viewpoint of both the ultimate capacity and the developed ductility. Besides, the experimental findings showed that providing castellated opening reduced the ultimate capacity, however, this reduction could be compensated by the application of external pre-stressing. Finally, an empirical expression was proposed in order to estimate the ultimate capacity of castellated beams subjected to external pre-stressing and their results showed good agreement with the numerical findings. [ABSTRACT FROM AUTHOR]

• Precast cement-based composite plates (PCBCPs) have been prepared and cured. • PCBCPs composed of SHCC material reinforced with internal mild steel plates. • PCBCPs have been used for Strengthening of shear-deficient RC beams. • Experimental tests results confirmed the capability of the adopted technique. • Inclined arrangement of the PCBCPs resulted in outstanding performance for RC beams. Precast cement-based composite plates (PCBCPs) have been prepared, cured and then used to strengthen shear-deficient reinforced concrete (RC) beams. The used PCBCPs have rectangular cross-sections of 100 mm width and 20 mm thickness made of strain-hardening cementitious composite (SHCC) material and reinforced with mild steel plates of 1 mm thickness having variant reinforcement ratios (1.4, 2.8, and 4.2%). The motivation of using such reinforced composite plates is to make use of the mutual benefits between the used materials where the internal steel plate alleviates the cracks localization manifested by plain SHCC material after cracking, while the SHCC material protects the steel plates against corrosion. Experimental test results showed that the use of PCBCPs significantly increased the ultimate shear capacity of the strengthened beams. Besides, inclined configuration of the PCBCPs showed higher shear performance compared to that exhibited by the vertical configuration from both the ultimate capacity and shear cracks characteristics viewpoints. Beam B 3-56-100-45 strengthened by inclined PCBCPs showed the best performance among all tested beams. It exhibited about 126% increases in the ultimate capacity compared to that of the control un-strengthened beam. On the other hand, the corresponding increase of counterpart beam reinforced with vertical plates was about 88%. [ABSTRACT FROM AUTHOR]

• SHCC-strengthened slabs are tested under the effect of drop weight loading. • The location of the SHCC layer at either tension or compression side is investigated. • The effect of surface preparation condition is mainly studied. • Impact energy of SHCC-strengthened slabs is obtained numerically using ABAQUS software. • The most favorable surface preparation condition is identified. In this paper, a thin layer of Strain-Hardening Cementitious Composites (SHCC) is provided in either tension or compression side of RC slabs aiming to improve their impact resistance under the effect of drop weight loading. The main parameter of the current study is the condition of the contact surface between the substrate slab and the SHCC overlay that was prepared by grinding, grinding plus steel dowels or grinding plus epoxy adhesive. Accordingly, 63 RC slabs were prepared and tested under the effect of drop weight falling from three different heights; 1, 1.5 and 2 m. It was found that the SHCC strengthening layer enhanced the impact resistance of the strengthened slab when added at either tension or compression side. However, in order to attain the outermost impact resistance showing ductile performance, it is better to provide a thin layer of the SHCC at the tension side of the slab connected to the substrate slab by epoxy resin applied on pre-prepared grinded surface. Furthermore, numerical simulations based on ABAQUS software package were performed on the strengthened slabs. Their results showed good agreement with the experimental findings from the viewpoint of the kinetic energy. Besides, the impact failure loads were determined numerically for the studied slabs and compared with those obtained from incremental static loading tests. [ABSTRACT FROM AUTHOR]

This paper presents an experimental program to justify the barrier design at the barrier-deck junction when compared to the factored applied transverse vehicular loading specified in the Canadian Highway Bridge Design Code (CHBDC). Compared to the dimensioning and the glass fibre reinforced polymer (GFRP) bar detailing of a recently crash-tested GFRP-reinforced barrier, the adopted barrier configurations in this paper were similar to those specified by Ministry of Transportation of Québec (MTQ) for TL-5 barrier except that the base of the barrier was 40 mm narrower and the deck slab is of 200 mm thickness, leading to reduction in the GFRP embedment depth into the deck slab. Four full-scale TL-5 barrier specimens were tested to collapse. Correlation between the experimental findings and the factored applied moments from CHBDC equivalent vehicle impact forces resulting from the finite-element modelling of the barrier-deck system was conducted followed by recommendations for use of the proposed design in highway bridges in Québec. [ABSTRACT FROM AUTHOR]

Curved composite concrete-steel I-girder bridges provide an exceptional solution to the problems of urban congestion, traffic, and pollution, but their behavior is quite complex due to the coupled bending and torsion response of the bridges. Moreover, dynamic behavior of curved bridges further complicates the problem. The majority of curved bridges today are designed using complex analytical methods; therefore, a strong need exists for simplified design methods in the form of empirical equations for the structural design parameters. In this paper, a sensitivity study is conducted to examine the effect of various design parameters on the free-vibration response of curved composite concrete-steel I-girder bridges. In order to determine their fundamental frequency and corresponding mode shapes, an extensive parametric study is conducted on 336 straight and curved bridges. ABAQUS software package was employed to carry out the numerical simulation for the considered bridges in order to obtain the fundamental frequencies. From the results of the parametric study, simple-to-use equations are developed to predict the fundamental frequency of curved composite concrete-steel I-girder bridges. It is shown that the developed equations are equally applicable to curved composite steel I-girder bridges of simple span or multi-spans with equal span lengths. [ABSTRACT FROM AUTHOR]

This article presents the results of an experimental study conducted in order to investigate the behavior of Type-I beam-column joints, where the beam was subjected to shear stresses due to combined effect of shear force and torsional moment (beam eccentric loading). Eight beam-column joint specimens were constructed and tested up to failure in order to better understand the complicated behavior due to combined loading transmitted from the beam to the column. The studied parameters were the eccentricity of beam load (torsional-moment-to-shear-force ratio Mt/Q), the configuration of beam side and compression reinforcing steel, the existence of the joint reinforcing stirrups, and the beam rigidity. Generally, the shear failure at the beam zone or at the joint panel was noticed to be the governing mode of failure for all tested specimens. The test results highlighted the importance of the configuration of both longitudinal side and compression reinforcing steel of the beam, where the inadequate embedded length of both of them into the joint panel including stirrups decreased the beam ultimate capacity but it kept the failure zone away from the joint panel. Finally, a threedimensional truss model was presented and analyzed. The results of the three-dimensional model showed good agreement with the experimental findings. [ABSTRACT FROM AUTHOR]

An experimental and analytical study on 15 specimens of lap splices embedded in nonconventional concrete without confining reinforcement was performed under direct tension. The experimental program involved two groups of straight‐ended and anchored‐ended bars; three different techniques were employed with different splice lengths. For straight‐ended bars, conventional lap splice was studied as a benchmark. The anchored‐ended steel bars were hooks, hooks intersecting with cross bars, and plate‐end bars. It was found that, the used techniques not only achieved higher tensile stress at failure, but also different modes of failure were observed. Besides, a splice length of five times bar diameter was found to be sufficient to achieve the nominal yield stress of the reinforcing steel bar in the case of anchored‐ended bars. Finally, an analytical model was proposed in order to predict the ultimate tensile stress of the straight‐ended spliced bars. The accuracy of the proposed model was verified against the test results of 137 existing specimens from previous research. The comparison showed good agreement between the results of the proposed model and the test results. [ABSTRACT FROM AUTHOR]

• New lap splicing technique for tensile steel bars has been developed. • The developed technique was based on anchor-ended bars using steel end plats. • Experimental tests confirm the adequacy of the adopted technique under the effect of repeated loading. • Based on the findings of the numerical simulation, a proposed equation was obtained to predict the ultimate splice strength of the anchor-ended bars. In the current paper, a newly developed technique in tension lap splices of steel bars is presented and investigated to verify its efficiency. Consequently, an experimental and numerical study on sixteen high-performance concrete (HPC) specimens containing lap splices without confining reinforcement were performed. The experimental program comprised two phases; the first one was a preliminary study that involved concrete prisms containing the developed splices and tested under axial tension, while the second phase was four-point flexural testing of RC beams having the adopted tension splices and subjected to repeated loading. Both phases included two sub-groups; a reference sub-group having conventional straight-ended splices and the other sub-group implicated in the newly developed technique based on anchor-ended splices. Experimental tests showed that by applying the developed technique, not only higher tensile stress at failure was achieved but also a bond-induced failure was switched to a flexural failure. Furthermore, a splice length of five times bar diameter was found to be sufficient to achieve the full tensile strength of the reinforcing steel bars in the case of the anchor-ended technique. Finally, numerical modeling was employed to study further parameters about the anchor-ended splices. As a result, a proposed equation was obtained based on statistical analysis to predict the ultimate strength of the anchor-ended splice. [ABSTRACT FROM AUTHOR]