Glass Fibre Reinforced Polymer Connectors Research Articles

Structural performance of precast concrete sandwich panels with bolt-steel plate connection subjected to axial loading

A new precast concrete sandwich panel with glass fiber-reinforced polymer connectors was proposed, utilizing bolt-steel plate connections. A compressive experiment was carried out to investigate the performance. The main damage was concrete crushing in the bolt connection region, at the panel bottom, and above the joint. The connector type, solid concrete rib, slenderness ratio, and thickness affected the failure mode and bearing capacity. The use of GFRP connectors and solid concrete ribs enhanced the ultimate bearing capacity and stiffness of the panels while reducing the lateral deflection. Higher slenderness ratios leading to reduced axial bearing capacity and increased lateral deflection. Finally, the results of the existing empirical calculation formulae were compared with experimental ones, and they were overly conservative. A new formula for predicting the bearing capacity was proposed, and the difference percentages between the proposed formula and experimental results were −0.4 %–2.8 %, which was the most accurate prediction formula.

Structural performance and section optimization of precast concrete sandwich panels with pin-type GFRP connectors

A precast concrete sandwich panel (PCSP) offers a good potential in the application of façade wall due to the improved energy efficiency. In this study, the structural performance of PCSP with pin-type glass fiber reinforced polymer (GFRP) connectors was investigated, and an optimization characterized by ribbed structural wythe was proposed and studied. Firstly, the pull-out and shear capacity of the pin-type connector were evaluated through direct tensile test and direct shear test, respectively. Thereafter, seven PCSP specimens were fabricated and tested under four points flexural load. The investigating parameters included the structural wythe thickness, loading direction, insulation bond, and section type of the structural wythe. The load-deflection relationship, crack pattern, failure mode, load-strain relationship, and degree of composite action of the PCSP were studied and compared. It was concluded that: (1) the tested PCSPs presented ductile failures; (2) the structural wythe thickness, loading direction and insulation bond would influence the cracking, yielding, and peak loads of the tested PCSP; (3) the PCSP with pin-type GFRP connectors could be designed as non-composite type owing to the low composite action; and (4) the proposed ribbed structural wythe could achieve a lightweight PCSP while considerable flexural stiffness and capacity could be retained.

Development of sandwich panels for multi-functional strengthening of RC buildings: Characterization of constituent materials and shear interaction of panel assemblies

This paper presents an experimental and numerical study aiming at the development of a sustainable and multifunctional composite sandwich panel for the rehabilitation of reinforced concrete (RC) buildings from the 1960s to the mid-1980s. The sandwich panel, which was designed for the structural, thermal and acoustic refurbishment of building facades, comprises three main components: (i) thin outer layers of Recycled Steel Fibre Reinforced micro–Concrete (RSFRC) that fulfil the strength, ductility and durability requirements of the panel; (ii) a lightweight core made of polystyrene that provides thermal insulation; and (iii)internally distributed glass fibre reinforced polymer (GFRP) connectors that join the different layers of the panel, providing an adequate structural behaviour to the composite system. The mechanical characterization tests highlighted the viability of using RSFRC for the production of structural sandwich facade panels, as relatively high post-cracking tensile capacity was obtained for thin RSFRC layers. Pushout and pullout tests were carried out on intermediate-scale specimens representative of the sandwich panel solution for assessing the overall composite behaviour of the sandwich panels and analysing the influence of the type of core insulation layer (expanded/extruded polystyrene cores, with different surface finishing), of the anchoring conditions (25 and 35 mm of embedment depth) and diameter of the GFRP connectors (8 and 12 mm). These tests showed that the structural GFRP connectors with diameters of 8 and 12 mm are able to ensure shear load transfer between RSFRC layers, exhibiting better composite behaviour when combined with anchorage depths of 25 and 35 mm, respectively. The numerical part of this study aimed at modelling the failure mechanisms observed at the interface between RSFRC and polystyrene, showing good agreement between experimental and numerical results, with important conclusions being drawn regarding cohesion and friction angle between these materials.

Accelerated ageing test and durability prediction model for mechanical properties of GFRP connectors in precast concrete sandwich panels

Glass fiber-reinforced polymer (GFRP) connectors are the key components in precast concrete sandwich panels, because they not only provide continuity between two concrete wythes but also promote thermal efficiency of the panels. This paper presents an experimental study on durability of GFRP connectors in alkaline solution (simulated concrete environment) with variable parameters of temperature (40, 60, and 80 °C) and conditioning time (3.65, 18, 36.5, 92 and 183 days). A total of 160 specimens were immersed in the alkaline solution with a composition specified in ACI 440.3R-12 at elevated temperatures. Scanning electron microscope (SEM) was used to observe the degradation mechanism of the specimens, and the phenomenon of debonding between fibers and resin could be observed more obvious with the increase of erosion time and temperature. The test results also showed that, after 183 days of immersion at 60 °C, tensile strength and modulus of elasticity of the specimens decreased about 38.85% and 21.45% respectively, while compressive strength and modulus of elasticity of the specimens decreased about 40.18% and 27.62%. Finally, a prediction model of tensile and compressive strength after conditioning over time at varied temperatures was proposed based on Arrhenius equation.

Verification of the Structural Performance of Textile Reinforced Reactive Powder Concrete Sandwich Facade Elements

As a part of the SESBE (Smart Elements for Sustainable Building Envelopes) project, non-load bearing sandwich elements were developed with Textile Reinforced Reactive Powder Concrete (TRRPC) for outer and inner facings, Foam Concrete (FC) for the insulating core and Glass Fiber Reinforced Polymer (GFRP) continuous connectors. The structural performance of the developed elements was verified at various levels by means of a thorough experimental program coupled with numerical analysis. Experiments were conducted on individual materials (i.e., tensile and compressive tests), composites (i.e., uniaxial tensile, flexural and pull-out tests), as well as components (i.e., local anchorage failure, shear, flexural and wind loading tests). The experimentally yielded material properties were used as input for the developed models to verify the findings of various component tests and to allow for further material development. In this paper, the component tests related to local anchorage failure and wind loading are presented and coupled to a structural model of the sandwich element. The validated structural model provided a greater understanding of the physical mechanisms governing the element’s structural behavior and its structural performance under various dead and wind load cases. Lastly, the performance of the sandwich elements, in terms of composite action, was shown to be greatly correlated to the properties of the GFRP connectors, such as stiffness and strength.

Experimental Study of Structural Performance of Precast Concrete Insulated Sandwich Panels with Cruciform Cross Section GFRP Connectors

This study investigated the structural performance of precast concrete insulated sandwich panels with cruciform cross section glass fiber-reinforced polymer (GFRP) connectors, based on tensile and shear tests. 5 tensile specimens and 4 shear specimens were fabricated and tested. The load-displacement relation and failure mode of the specimens were analyzed. The results revealed that the average ultimate tension load of the tested specimens with single GFRP connector was 13.14kN with concrete splitting or concrete partial cone failure. For the shear specimens, the average ultimate shear load was 14.83kN with rupture failure of GFRP connector. Furthermore, durability of sandwich panels was investigated, by fabricating and testing 48 tensile specimens with GFRP connectors immersed in tension load had sufficient safety in different design situations.

Direct shear tests of glass fiber reinforced polymer connectors for use in precast concrete sandwich panels

The precast concrete sandwich panel (PCSP) is a popular structural type used for prefabricated construction. In this study, three kinds of glass fiber reinforced polymer (GFRP) connector, including a flat plate, a corrugated plate, and a hexagonal tube connector, were investigated for potential use in PCSPs. In-plane direct shear tests were conducted to evaluate the performance of the connectors based on a typical push-out configuration (i.e., three concrete wythes linked with connectors and two rigid foam layers in between). Twenty-five specimens were tested, and the parameters investigated consisted of GFRP laminate thickness, projected length, and shear force direction. The shear force vs. relative slip relationships and failure modes of all types of connector were compared and are discussed in detail in this paper. Meanwhile, finite element (FE) analysis was conducted to reproduce the test results. All three types of GFRP connector exhibited a progressive failure manner in spite of the linear brittle nature of the FRP materials; the corrugated plate connector achieved higher deformability than the flat plate connector, particularly when the GFRP laminate thickness was small; and the hexagonal tube connector exhibited similar behavior along two orthogonal directions, making them well suited for use as two-way connectors. The developed FE model was able to well predict the peak shear load and stiffness of all types of connector based on comparisons with the test results.

Pull-out behaviour of Glass-Fibre Reinforced Polymer perforated plate connectors embedded in concrete. Part I: Experimental program

The Glass Fibre Reinforced Polymer (GFRP) connectors studied in this work were previously proposed by the authors for connecting the outer Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC) layers of sandwich panels for prefabricated modular housing. In this building system, SFRSCC was used to totally eliminate the need for conventional reinforcement and to decrease the thickness of the panel’s outer layers, with consequent reduction of the global self-weigh of the panels, while GFRP connectors aimed to significantly decrease thermal bridging effects. For a reliable design of the structural elements that make use of these connectors, the mechanical behaviour of this connection should be known and taken into account. The present paper summarizes the results obtained in an experimental research devoted to the assessment of the behaviour of GFRP-SFRSCC connection by performing pullout tests with specimens representative of the developed sandwich panel. The specimens were designed to examine the influence of the number and geometry of holes executed in the GFRP connector that assure the connection between these two materials.

Structural performance of GFRP connectors in composite sandwich facade elements

To take structural aspects into consideration in the SESBE research project, focusing on the development of “smart” facade elements a systematic testing and modelling program has been developed for the verification of the structural performance of the facade sandwich elements. The present paper mainly focuses on the verification of the mechanical performance of the glass fibre reinforced polymer (GFRP) connectors of the novel type of facade element composed of reactive powder concrete (RPC) panels with foam concrete insulation between them. Because of the reduced thickness of the large facade elements, the performance of the connectors is critical for the entire structural concept. The first series of the testing programme concerning connector performance are presented here. The results suggest that sufficient strength and ductility of the connectors can be ensured using GFRP in the proposed thin light-weight facade elements.

Development of sandwich panels combining fibre reinforced concrete layers and fibre reinforced polymer connectors. Part II: Evaluation of mechanical behaviour

In the first part of this paper the authors describe an innovative sandwich panel that comprises Glass Fibre Reinforced Polymer (GFRP) connectors and two thin layers of Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC). This second part of the paper reports the investigation performed by the authors based on the numerical simulation of these sandwich panels. The simulations use the Finite Element Method (FEM) software implemented by the second author (FEMIX). Through linear static analyses and consideration of Ultimate Limit State loading scenarios, parametric studies were performed in order to optimise the arrangement of the GFRP connectors and the thickness of the SFRSCC layers. Moreover, models considering a specific nonlinear behaviour of SFRSCC were also constructed in order to simulate the progressive damage of the panel induced by cracking. In the scope of the nonlinear analyses, emphasis is given to parameter estimation of fracture modelling parameters for the fibre reinforced concrete based on both inverse analysis and the fib Model Code.