Longitudinal Shear Bond Research Articles

Longitudinal shear bond strength of profiled deck composite slab: An experimental and analytical investigation

In recent years, composite slabs with concrete topping and profiled/ re-entrant decking sheets have gained popularity as they are faster, more economical, and lightweight construction techniques. In a composite floor, profiled/re-entrant decking sheets serve a dual purpose: they serve as permanent formwork during the construction phase and as main reinforcement after the concrete topping has hardened. Horizontal shear bond strength is a crucial parameter in the design of the composite floor. Presently, the m-k and PSC methods are the most commonly used techniques to calculate the horizontal shear bond strength of the composite slab. In this study, four full-scale composite slabs were cast and tested for four distinct shear spans under four-point loading conditions. The influence of shear span was investigated. Short and long shear span specimens were investigated. Three alternative approaches (the modified partial shear connection method, the force equilibrium method, and the composite beam partial shear connection method) were adopted to evaluate the horizontal shear bond strength of the profiled deck composite slab. Load- displacement behavior, horizontal shear bond strength, and failure modes were used to assess the structural performance of composite slab specimens. The results of all three methods were compared. The horizontal shear bond stress evaluated by the slenderness and force equilibrium methods were in close agreement, whereas the composite beam partial shear connection method approach may underestimate the longitudinal shear bond strength, but it may still be employed as an alternative method.

Push-off and Pull-out Bond Behaviour of CRC Composite Slabs – An Experimental Investigation

Longitudinal shear bond governs the load carrying capacity and performance of profiled steel reinforced composite slabs. Despite testing the load carrying capacity of composite slabs in large-scale size, many researchers have attempted to investigate the shear bond characteristics of composite slabs in small-scale experiments with direct shear load due to its cost effectiveness. With partial replacement of fine aggregate by crumb rubber in conventional concrete (CC), crumb rubber concrete (CRC) has the excellent feature of ductility, which increases the compatibility of deformation with the profiled steel deck and hence is expected to improve bond performance. In this paper, the direct shear test was implemented on small-scale composite specimens using both horizontal push-off and pull-out loads to investigate the bond characteristics between 0.75 mm-thick re-entrant profiled steel deck (Bondek) and CRC/CC with targeted compressive strength of 25 MPa. The push-off specimens were tested with and without clamping force, while pull-out specimens were tested against different sides of the deck embossment. The overall performances of CRC specimens in the elemental tests were very close to CC specimens, with only 5% difference in the ultimate bond strength. CRC material showed reduced vertical separation from the steel deck, which mitigated the longitudinal slippage between the concrete-steel interfaces. Compared to the push-off setup, the pull-out test setup showed overestimation of the bond stress which was explained from FEM model that the higher deformation in ribs and soffit of steel deck was produced. Hence, the pull-out setup is not recommended for determining bond characteristic for future study.

Shear bond behaviour of elemental composite beams with different configurations

In this study, an experimental program for testing steel concrete composite slabs subjected to symmetrical double line loads has been carried out to investigate the longitudinal shear bond behaviour. Different configurations of steel concrete composite slabs with and without embossments were studied. The flexural characteristics, ultimate strength and bond strength (end slip test) of composite slabs were determined. Partial connection (PC) approach was used to predict the longitudinal shear bond. The embossments in the profile decks slightly enhanced the longitudinal shear resistance and load carrying capacity (especially, at the end of the plastic stage), and also delayed debonding. Two failure modes, brittle and ductile phases, were observed during the tests. The experimental results demonstrated that the embossments do not have promising contributions to longitudinal shear strength and ductility of the composite slab elements, especially to elastic and plastic behaviour stages prior to the ultimate load carrying capacity. This study proposes a semi empirical formula (SEF) to evaluate the shear stress using simplification of the m-k method. The proposed SEF method was validated with data obtained from literature, showing an acceptable level of reliability and therefore, it could represent a good alternative for m-k and PC methods.

The longitudinal shear bond behavior of an innovative laminated fiber reinforced composite slab

Abstract Composite slabs with ordinary concrete and typical profiled steel sheeting are widely used in construction industry due to their obvious advantage in casting as well as in structural performance. This paper proposes a new laminated pouring technique, and presents a series of full-scale tests conducted on a new type of composite slab produced using both lightweight aggregate concrete and polymer fiber reinforced lightweight aggregate concrete with a closed-type (non-embossed dovetailed) steel sheeting profile (LFRCS). A total of 12 simply supported specimens were tested to investigate the structural behavior of this new type of composite slab with special emphasis on the lamination thickness. Test results were used to obtain an effective range for the laminated pouring technique. It was observed that plane cross-sections remain plane in LFRCSs but the longitudinal shear bond strength dominates the failure mode regardless of lamination thicknesses. In addition to linear regression methods and PSC based methods that are typically used for accessing the longitudinal shear bond strength for composite slabs with normal weight and lightweight concretes, rational modifications and relevant formulas for the specified LFRCS configurations including the effects of tensile reinforcement have been proposed. Results predicted using the proposed analytical techniques were compared those obtained experimentally, and the comparison showed good agreement.

Partial shear connection in light steel composite beams

A new form of light steel composite beam has been developed that uses C sections acting in tension with shear connectors in the form of screws or bolts or perforations in the web of the C section. The shear and bending resistance is also increased by using side C sections to the beams. Bending tests on point-loaded beams of 0.8, 1.1 and 1.7 m span showed that for the short span beams, the longitudinal shear bond strength of the base C sections is 1.4 N/mm2 for plain C sections and 2.3 N/mm2 for perforated C sections when expressed over the horizontal plane. Plain side C sections added 80% and perforated side Cs added 130% to the load-bearing capacity of the composite beams with base Cs. The theory is extended to cover elastic design taking account of partial shear connection in which the shear stiffness of the perforated web of the C section is approximately 10 N/mm3 (per unit web area) and that of the plain web is approximately 3 N/mm3.

Experimental study on the longitudinal shear bond behavior of lightweight aggregate concrete – Closed profiled steel sheeting composite slabs

Composite slabs with ordinary concrete and typical profiled steel sheeting are quite common in construction industry. This paper presents full-scale experiments conducted on a new type of composite slab produced from lightweight aggregate concrete and closed profiled steel sheeting (LCCS). A total of 11 simply supported specimens were tested to investigate the structural behavior of this new type of composite slab with special emphasis on their failure modes. Whilst shear bond failure is the common failure type for typical composite slabs with sheet sheeting, a new type of failure was observed herein where slabs failed with showing remarkable bending capacity, and significant end slips was observed in long-span slabs. In addition to m-k method and PSC method, which are typically used for composite slabs with normal weight concrete, three other techniques such as slenderness method, PSC composite beam method and force equilibrium method were used to assess the longitudinal shear bond strength of LCCS. The ultimate carrying capacity and the shear bond stress predicted using slenderness method and force equilibrium method showed very good agreement with test results; PSC composite beam method may underestimate the longitudinal shear bond strength, but still can be used as an optional method.

Longitudinal shear resistance of PVA-ECC composite slabs

Including polyvinyl alcohol (PVA) fiber to develop a ductile engineered cementitious composite (ECC) is an effective way to overcome the brittle behavior of conventional concrete and to increase the efficiency of composite slab construction. Two groups of full-scale composite slabs were prepared, cast and tested until failure. Each group consists of three PVA-ECC composite slabs and one control specimen made with normal concrete topping. The first group has been tested with long shear span of 900mm while for the second group, the shear span was 450mm. Test results have been analyzed and the longitudinal shear bond strength has been computed using both methods of m–k and partial shear connection (PSC). In addition, comparison with other types of composite slabs using the same profiled steel sheeting was also carried out. The longitudinal shear bond strength was found to be 0.46MPa and 0.387MPa using m–k and PSC, respectively, with difference of 15.87%. The results showed that the failure modes of the PVA-ECC composite slabs are ductile with enhanced load carrying capacity. Therefore the use of PVA-ECC composite slabs in the construction industry would consider a better economic solution.

Influence of Dentin Deproteinization on Bonding Degradation: 1-year Results

The decalcification protocol of dentin surface with sodium hypochlorite removes the exposed collagen fibrils and could improve the longevity of the bonding interface. This study evaluated the influence of collagen removal with 10% sodium hypochlorite (10% NaOCl) on the longitudinal shear bond strength (SBS) of adhesives to dentin. Seventy-two extracted human molars were sectioned and the buccal and lingual surfaces were flattened and acid etched with 37% phosphoric acid for 15 seconds. The specimens were divided into six groups (n = 12 teeth - 24 sections), according to adhesive and collagen removal protocol: group 1: UNO Dentastic; group 2: Prime and Bond NT; group 3: Single Bond; group 4: 10% NaOCl + UNO Dentastic; group 5: 10% NaOCl + Prime and Bond NT; group 6: 10% NaOCl + Single Bond. Composite Z100 buildup was prepared, and the SBS test was assessed after 24 hours and 1 year. Data were submitted to three-way analysis of variance (ANOVA) and Tukey tests (p < 0.05). The mean values (MPa) were for 24 hours: G1: 22.45B; G2: 7.90DE; G3: 12.56CD; G4: 19.85BC; G5: 33.73A; G6: 20.77B; and for 1 year: G1: 2.43E; G2: 2.26E; G3: 4.3DE; G4: 18.79BC; G5: 26.49AB; G6: 22.73B. Dentin deproteinization treatment with 10% NaOCI influenced the SBS compared with conventional treatment. The negative influence on SBS detected for conventional groups at 1-year interval was not detected for deproteinized groups. The longevity of hybrid layer is critical due to the hydrolysis process at the adhesive interface over time. The use of 10% NaOCl deproteinization protocol might improve the longevity of bonding in adhesive restorations.

Simulation Analysis of Longitudinal Shear Bond Performance of Lightweight Aggregate Concrete Composite Slab

Because of the experiment can only reflect the overall performance of composite slabs under the various parameters combined action, and to ensure the materiality level of one single parameter, ANSYS, one of the finite element analysis software, was used in analogue simulation. According to selected reasonable elements and generated contact elements where between profiled steel sheet and lightweight aggregate concrete, appropriate mathematical model was been built. With full Newton-Raphson method to calculate nonlinear equation, the relevant data and curves were been obtained. Through the comparison between simulation analysis results and experiment results, the mathematical model was verified that it could reflect experiment correctly. These studies could provide assistance in the lightweight aggregate concrete composite slab project finally.

Experimental investigations on composite slabs to evaluate longitudinal shear strength

Cold-formed steel profile sheets acting as decks have been popularly used in composite slab systems in steel structural works, since it acts as a working platform as well as formwork for concreting during construction stage and also as tension reinforcement for the concrete slab during service. In developing countries like India, this system of flooring is being increasingly used due to the innate advantage of these systems. Three modes of failure have been identified in composite slab such as flexural, vertical shear and longitudinal shear failure. Longitudinal shear failure is the one which is difficult to predict theoretically and therefore experimental methods suggested by Eurocode 4 (EC 4) of four point bending test is in practice throughout world. This paper presents such an experimental investigation on embossed profile sheet acting as a composite deck where in the longitudinal shear bond characteristics values are evaluated. Two stages, brittle and ductile phases were observed during the tests. The cyclic load appears to less effect on the ultimate shear strength of the composite slab.

Design of composite slabs with profiled steel decking: a comparison between experimental and analytical studies

This paper presents the structural behavior of composite concrete slabs with CRIL DECKSPANTM (Colour Roof India Limited (CRIL), Mumbai, INDIA) type profiled steel decking by experimental and analytical studies. The slab is created by composite interaction between the concrete and steel deck with embossments to improve their shear bond characteristics. However, it fails under longitudinal shear bond due to the complicated phenomenon of shear behavior. Therefore, an experimental full-size tests has been carried out to investigate the shear bond strength under bending test in accordance to Eurocode 4 - Part 1.1. Eighteen specimens are split into six sets of three specimens each in which all sets are tested for different shear span lengths under static and cyclic loadings on simply supported slabs. The longitudinal shear bond strength between the concrete and steel deck is evaluated analytically using m-k and partial shear connection (PSC) methods and compared the values. The experimental results is verified and compared with the results of both m-k and PSC methods. Comparison of experimental and analytical results of the load-carrying capacity of composite slabs revealed that agreements between these values are sufficiently good. As a result, m-k method proved to be more conservative than PSC method.

Shear bond mechanism of composite slabs — A universal FE approach

The strength of concrete slabs composited with cold-formed profiled steel decks is normally governed by the longitudinal shear bond failure at the steel concrete interface. The design methods for the longitudinal shear bond strength adopted in the current construction practice such as the m-k method and partial interaction method all based on the full-size tests, which are expensive and time consuming, however are also semi-empirical. A universal FE approach of composite slabs is presented, in which the shear bond interaction between the steel deck and the concrete is treated as a contact problem considering adhesion and friction. Both geometrical and material nonlinearities are all considered in the FE model. The preliminary FE analysis is verified in simulation of the pull-out tests as far as the cohesion and the frictional bond of the contact interface are considered. The fine FE analysis using the contact model is further carried out in study of the composite slabs in flexural bending. The FE analysis based on the nonlinear contact concept is verified and validated by comparing the test results for both the pull out and bending tests of the composite slabs. Comparisons of the experimental and the FE analytical results indicate that the FE analysis based on the interface contact model, agree well with the test results, and is capable of predicting the performance and the load carrying capacity of composite slabs.