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To study corrosion effects on real structures, three prestressed concrete (PC) girders salvaged from a decommissioned 27-year-old bridge in Alberta, Canada, were studied numerically and compared to experimental tests. Nonlinear finite element (FE) models were developed to simulate the degraded flexural and shear behaviour of PC girders. The FE models were used to infer the possible unknown deterioration conditions (i.e., forensic analysis) by comparing FE-predicted and experimental behaviour of the girders. Based on the developed FE models, comprehensive parametric studies considering various corrosion-induced deteriorations at a wide range of corrosion levels were also conducted. Insights gained from the parametric study assisted assessing other girders under similar conditions. It was found that corrosion defects, such as reinforcement area loss, prestress force loss, and bonding loss in the end anchorage, affect PC girder behaviour significantly and the developed FE models of corroded PC girders can assist girder condition assessment.

Mass timber panel (MTP)-concrete composite floors are gaining increasing interest from builders and designers due to their optimized structural performance, light self-weight, and aesthetic...

Mass timber panel–concrete (MTPC) composite floor systems are currently the preferred choice of designers for multistory modern mass timber construction. An analytical model for one-way-act...

The American Concrete Institute recently updated their one-way shear provisions for steel–reinforced concrete (RC), and it is time to consider updating provisions for one-way shear in fibe...

Lack of design standards and guidelines is the most important barrier limiting widespread use of mass timber panel–concrete (MTPC) composite floor systems, a preferred choice by designers i...

The flexural response of 12 2-m-long and 152-mm-diameter fiber-reinforced polymer (FRP) skinned members with foam cores was investigated. Nine cylinders with various flax-FRP (FFRP) laminat...

In order to consider the interactive behavior of flexure and shear, an enhanced displacement-based fiber beam element is developed by utilizing multi-axial material constitutive models for fibers, in particular, with the Modified Compression Field Theory (MCFT) for fibers representing concrete with smeared stirrups in RC/PC beams/girders. The potential shear-locking problem is avoided by adopting a mixed interpolation form with a bubble term for the displacement field, and the validity of the approach is verified by a classic example. The proposed element is first validated through a classic test series of shear-critical RC beams from the literature and then applied to a PC girder recently tested under both shear-critical and flexure-dominated scenarios. It is shown that the proposed element can be used to predict the structural behavior of RC beams and PC girders satisfactorily, after enhancing the conventional fiber beam element by considering the coupling of flexure and shear. In addition, the proposed element provides a tool to predict both flexure and shear capacities of concrete beams with adequate accuracy.

Precast concrete sandwich panels are usually comprised of two concrete layers surrounding rigid insulation. The most commonly used insulation types are extruded (XPS) and expanded (EPS) polystyrene or polyisocyanurate (PIR). Studies have shown that walls with EPS insulation develop higher composite action than walls with XPS insulation because of EPS's surface roughness. In this study, notched insulation is investigated using double shear push-through tests on 24 specimens (18 notched and 6 un-notched). Specimens were constructed with X-shaped GFRP bar shear connectors . Test parameters include GFRP bar diameter (9.5 and 16.0 mm), insulation type (XPS, EPS, PIR), and notch type (trapezoidal, rectangular). Notches allow XPS to reach higher capacities since bond failure is mechanically prevented. On average, when the 9.5 mm connector was used with XPS, adding rectangular notches resulted in 37% and 50% increase in the connection proportional limit and peak load respectively, while trapezoidal notches gave lesser respective increases of 21% and 27%. These increases were not apparent in samples made with larger (16 mm) connectors since stiffer connectors attract more proportion of the load nor in samples with EPS or PIR insulation where the foam's surface roughness combined with stress concentrations at notches promoted diagonal shear failure.

The effect of thermal cycling between −24 and + 24 °C on the electrical resistivity of five concrete mixtures was investigated at early-ages. Each mixture was subjected to two thermal cycles (initiated either 1 or 14 days after casting) wherein temperatures were changed by 1 °C/h. Electrical resistivity increased as temperature decreased. This relationship followed the Arrhenius equation until the phase transition temperature (i.e. initial freezing of the pore solution), at which point electrical resistivity increased greatly. A method of determining the phase transition temperature is presented that could be used in place of existing methods using mortar cubes. The phase transition temperature was higher during thawing cycles compared to freezing cycles for all mixtures. Mixtures with ground slag replacing cement had higher resistivity and lower phase transition temperatures than mixtures using only cement due to the change in the ionic combination of the concrete pore solution. The phase transition temperature decreases as concrete ages.

An analytical model was developed to predict the flexural response, and determine the impact of various shear connector parameters on the behavior, of architectural partially-composite precast concrete insulated panels. The sandwich system incorporates two concrete wythes with expanded polystyrene foam and angled shear connectors in between. The model accounts for material nonlinearity and cracking and incorporates idealized load–slip relationships to determine the amount of shear force transferred between wythes, which controls the degree of composite action. The model agrees well with experimental results of a large database from literature, having an average difference in peak loads of −1.0% with a standard deviation of 13.4%. A comprehensive parametric study investigated the effect of connector spacing, diameter, insertion angle, shear modulus of insulation, and connector material, namely steel and fiber-reinforced polymer, on the degree of composite action and hence on the load–deflection response. These parameters were also shown to critically affect failure mode, where a transition from a connector’s material or pull-out failure to a flexural failure of the reinforced concrete wythe occurs. It was also shown that insulation bond alone contributes substantially, about 47% composite action by strength. Finally, for design purposes, the model can estimate the size and spacing of shear connectors to give a desired degree of composite action.

The response of non-slender flax fibre reinforced polymer (FFRP)-skinned foam filled tubes under axial compression was investigated using 39 specimens. Different cross-ply fibre arrangements and foam densities (33–65 kg/m3) were tested; the responses were compared to hollow FFRP tubes and Glass-FRP (GFRP) skinned tubes. Although axial behaviour was not significantly affected by changing foam density, hollow tubes were weaker than foam filled sections. This suggests that low density foam is effective at preventing premature failure. FFRP-skinned tubes with a skin thickness of 6.4 mm behaved similarly to GFRP-skinned tubes with a skin thickness of 3.4 mm in terms of strength and stiffness but were considerably better at absorbing energy. Specific strength and stiffness were highest with the lightest foam. The best performing FFRP-skinned tubes had specific strengths about 75% that of GFRP-skinned tubes with similar dimensions and equivalent foam cores.

Precast concrete Insulated Wall Panels (IWP) are thermally and structurally efficient systems used in buildings. Although their flexural behaviour has been studied in detail, there is limited research on thermal bowing of IWP. Bowing causes undesirable deflection and stresses that are not well addressed in design guides. Four 6.1 m long panels with Glass Fibre Reinforced Polymer (GFRP) shear connectors were tested using a thermal enclosure that induced temperature differentials over 20 °C. The stiffness of the 9.5–16 mm diameter shear connectors used in the full panels was found with 18 push-through tests on representative segments of the larger panels. The connector stiffness ranged between 26 and 59 kN/m and is stiff relative to other connector systems reported in the literature. Thermal load caused bowing that ranged between 39 and 44% of the Canadian concrete design standard (A23.3–14) acceptable service load deflection at a 20 °C temperature differential. Thermal load cracked the IWP and loaded connectors beyond their proportional limit. The amount of thermal bowing at a 20 °C temperature differential increased 16% with an 82% increase in connector stiffness. Results of these tests indicate that bowing is significant in panels with high connection stiffness and may be a concern in long panels designed to carry axial loads.

Mass timber panel-concrete composite floors efficiently combine the structural merits of timber and concrete and are gaining interests from builders and designers. Among different connection systems in the composite floors, the notched connection is both structurally superior and cost effective. However, due to the lack of design methodology, the use of notched connection in mass timber panel-concrete composite floor systems is hindered. This study investigated some important factors that could affect the structural performance of notched connections through experimental studies. Ten types of notched connections were made with varying factors including geometry of the connection, orientation of timber and presence of additional steel fasteners in the connection, and tested under shear load. Test results show that stiffness, load-carrying capacity and failure pattern vary among different configurations, and geometry of the connection and orientation of timber are the most important factors that influence the connection performance. Results from this study could serve as an important reference for the optimal design of the notches in the composite floors, as well as improving the existing design rules and verifying the analytical models for the notched connections.

Glass fiber–reinforced polymer (GFRP) shear connectors provide much reduced thermal bridging in insulated concrete sandwich panels compared to steel connectors. In this study, 50 specimens with dimensions of 254×254×900 mm representing segments of a precast sandwich wall comprising two concrete wythes and a concrete stud surrounded by insulation foam have been tested in a double-shear configuration. Three types of GFRP connectors produced from available sand-coated and threaded rods were tested and compared to conventional steel and polymer connectors. GFRP connector diameters varied from 6 to 13 mm, and spacing varied from 80 to 300 mm. Both circular and rectangular cross sections were examined, along with various end treatments to compare with simple straight embedment. The shear strength of GFRP connectors, including the effect of friction between concrete and foam, ranged from 60 to 112 MPa, significantly higher than polymer connectors but lower than steel connectors. As the connectors bridge...

This paper presents a numerical model developed to predict the response of partially composite load bearing concrete sandwich panels under axial loads applied to the structural wythe at any eccentricity. The model accounts for material nonlinearity, second-order effects, and cracking of concrete and plasticity of steel reinforcement, and can also model fiber-reinforced polymer (FRP) connectors. The analysis uses a bond-slip model to simulate partial composite action between the two wythes resulting from various configurations of insulation and shear connectors. A variety of failure modes can be detected, including concrete crushing, flexural yielding, connectors yielding, pullout or rupture, and stability failures. Progressive failure of connectors is also modeled. The degree of composite action (κu) can be calculated for a given design. The model was verified against experimental data and used to conduct a comprehensive parametric study. It was shown that κu increases with panel length. Connector...

In this study, 38 push-through tests were performed on a precast concrete insulated sandwich panel design using combined angled and horizontal connectors. Basalt fiber-reinforced polymer (BFRP) and steel connectors were tested and compared. The key parameters were various inclination angles and diameters of connectors; orientation of the diagonal connector relative to loading (i.e., tested in tension or compression); and panels with or without an active foam-to-concrete bond. Steel connectors failed by yielding in tension and inelastic buckling in compression. Larger-diameter BFRP connectors usually pulled out under tension and crushed in compression. Smaller-diameter BFRP connectors ruptured in tension and buckled in compression. Strength and stiffness increased with the connector angle and diameter. The insulation foam bond was found to contribute similarly regardless of connector material. An independent theoretical model accounting for material, bond, and stability failure modes, as well as ge...

The axial and flexure combined loading performance of a slender partially-composite concrete insulated wall design constructed using basalt fiber-reinforced polymer (BFRP) shear connectors and longitudinal BFRP reinforcement is investigated. The load-bearing wall panel sections, 600 mm wide and 2,700 mm long, were first subjected to axial loads ranging from 0 to 900 kN applied to the structural wythe only. The panels were then loaded to failure in four-point bending to develop the axial load-bending moment interaction diagram of the partially-composite system, which was compared to theoretical fully-composite and noncomposite curves. As axial load increased, failure under transverse loading changed from shear-compression of the structural wythe to diagonal splitting of insulation foam and rupture of BFRP connectors, then to crushing of the structural wythe. Composite action by the strength criterion reduced from 47 to 3% as axial load increased from 150 to 900 kN; while that by the stiffness crite...

There is a great demand to improve both the structural and thermal characteristics of insulated precast concrete sandwich panels. This paper addresses the potential of using a number of Glass Fibre Reinforced Polymer (GFRP) connectors developed in this research program as an alternative to metallic connectors. The objective is to reduce thermal bridging in the sandwich panels, while transferring shear forces to develop composite action within the panel. The panel incorporates a new system of concrete wythes and studs connected by the GFRP connectors, where the studs are not in direct contact with the wythes. The load-slip response of the system has been established through shear tests. It was also shown that adhesion between the insulating foam and concrete provides significant shear resistance prior to engaging the GFRP connectors.