João R. Correia

GFRP sandwich panels with PU foam and PP honeycomb cores for civil engineering structural applications

Purpose – The purpose of this paper is to present experimental investigations on the structural behaviour of composite sandwich panels for civil engineering applications. The performance of two different core materials – rigid plastic polyurethane (PU) foam and polypropylene (PP) honeycomb – combined with glass fibre reinforced polymer (GFRP) skins, and the effect of using GFRP ribs along the longitudinal edges of the panels were investigated.Design/methodology/approach – The experimental campaign first included flatwise tensile tests on the GFRP skins; edgewise and flatwise compressive tests; flatwise tensile tests on small‐scale sandwich specimens; and shear tests on the core materials. Subsequently, flexural static and dynamic tests were carried out in full‐scale sandwich panels (2.50×0.50×0.10 m3) in order to evaluate their service and failure behaviour. Linear elastic analytical and numerical models of the tested sandwich panels were developed in order to confirm the effects of varying the core mater...

Buckling Behavior and Failure of Hybrid Fiber-Reinforced Polymer Pultruded Short Columns

AbstractThis paper addresses the buckling behavior and strength of hybrid pultruded short profiles subjected to uniform compression. Since the design of glass fiber-reinforced polymer (GFRP) pultruded profiles is often governed by deformations and buckling phenomena, the introduction of carbon fibers in GFRP (hybrid) profiles has been proved to increase both strength and stiffness of flexural members. In the context of short compression members (columns), experimental, numerical, and analytical studies were carried out, with particular attention being given to the local buckling. Two series of 660-mm-long I-section profiles (200×100×10  mm) were tested under uniform compression. In order to evaluate the advantages of introducing carbon fiber reinforcement in the flanges, two profile types were tested: bare GFRP profile (reference column) and carbon fiber reinforced polymer (CFRP) strengthened GFRP profile (hybrid column). Shell finite-element (SFE) models were developed and validated, based on experimenta...

Creep behaviour of sandwich panels with rigid polyurethane foam core and glass-fibre reinforced polymer faces: Experimental tests and analytical modelling

This paper presents experimental and analytical investigations about the creep behaviour of sandwich panels comprising glass-fibre reinforced polymer faces and rigid polyurethane foam core for civil engineering applications. A full-scale sandwich panel was tested in bending for a period of 3600 h, in a simply supported configuration, subjected to a uniformly distributed load corresponding to 20% of the panel’s flexural strength. Additionally, specimens of polyurethane foam core were tested in shear for a period of 1200 h, for three different load levels corresponding to 10%, 20% and 30% of the foam’s shear strength. Experimental results were fitted using Findley’s power law formulation. Creep coefficients, shear modulus reduction factors and time-dependent shear moduli were obtained for the polyurethane foam in shear. A composed creep model is proposed to simulate the sandwich panel’s long-term creep deformations by considering the individual viscoelastic contributions from (1) the core material in shear and (2) the glass-fibre reinforced polymer faces in tension/compression. The composed creep model predictions adequately reproduced the full-scale panel’s experimental results. In addition, a good agreement was found between the composed creep model predictions and the extrapolation of the power law fitting obtained from the full-scale panel test, for a 50-year period.

Glass fibre reinforced polymer pultruded flexural members: assessment of existing design methods

Glass fibre reinforced polymer (GFRP) pultruded profiles are being increasingly used in bridge and building construction as an alternative to traditional materials because of their several favourable properties that include high strength, low self-weight, short installation times, low maintenance requirements and improved durability. In spite of these advantageous characteristics, there are some factors delaying the widespread use of GFRP pultruded profiles in civil infrastructure, one of which is the lack of widely accepted design codes. This paper presents the results of analytical, experimental and numerical investigations on the structural behaviour of GFRP pultruded profiles, the objective of which was to evaluate the relative accuracy of existing design methods. A survey of analytical formulae available for the design of GFRP pultruded flexural members at both service and ultimate limit states is first presented. Subsequently, results of a test programme carried out at Instituto Superior Técnico (IST) are briefly discussed—the experiments included material characterization tests and full-scale flexural tests on I-section simply supported beams and cantilevers. These tests allowed for the evaluation of the service behaviour of GFRP flexural members and some of their most relevant failure mechanisms and respective ultimate loads. Results from experimental tests are compared with those obtained from analytical formulae and numerical models in order to evaluate the relative accuracy of existing design methods.

Management system for road bridge structural bearings

Support bearings used in road bridges frequently account for a major part of the maintenance budget of the corresponding bridges. In addition, there are considerable indirect costs and inconveniences resulting from rehabilitation operations and consequent interruption of traffic. This paper presents an innovative management system for support bearings used in road bridges. The system encompasses the development of a classification system of bridge support bearings, their anomalies and possible causes, inspection and diagnosis methods, and maintenance and rehabilitation techniques, linked by appropriately validated correlation matrixes. Based on a set of parameters that define degradation levels, the system allows evaluating each defect in terms of physical and functional deterioration and social impact. Priorities for action can then be set according to the parameter considered most critical: anomaly, bearing, bridge or road section.

Creep of Sandwich Panels with Longitudinal Reinforcement Ribs for Civil Engineering Applications: Experiments and Composite Creep Modeling

AbstractComposite sandwich panels with reinforcement ribs or webs are being increasingly considered for structural applications in civil engineering. Such panels are prone to creep when subjected to significant permanent loads and therefore the effects of this phenomenon must be duly accounted for in their design. Data regarding the viscoelasticity of sandwich panels and their constituent materials is still scarce and often cannot be directly used for creep predictions in design practice. To address this issue, this paper presents the experimental assessment and the analytical modeling of the viscoelastic response of two types of sandwich panels, with and without reinforcement ribs. Panels comprising glass fiber–reinforced polymer (GFRP) faces, cores of polyurethane (PU) foam, and longitudinal GFRP ribs are considered. The ribs increased the flexural strength and stiffness of the panels by a factor of two, while providing a threefold reduction in their creep compliance. A composite creep modeling (CCM) ap...

Experimental investigations on continuous glass-GFRP beams : preliminary nonlinear numerical modelling

This paper describes results of experimental and numerical investigations about the structural behaviour of composite beams made of annealed glass panes and GFRP pultruded profiles. A brief description of flexural tests previously carried out on simply supported glass and glass-GFRP composite beams is first presented. Then, results of flexural tests on two-span glass-GFRP composite beams, bonded with three different structural adhesives, are described in detail. Finally, a preliminary numerical study of the glass-GFRP composite simply supported beams is presented. In this study, two-dimensional finite element models were developed in order to simulate and analyse the serviceability and post-cracking behaviour of those beams. Experimental and numerical results presented in this paper prove the advantages and technical viability of glass-GFRP composite beams.

Elastic and viscoelastic behaviour of sandwich panels with glass-fibre reinforced polymer faces and polyethylene terephthalate foam core

This paper presents experimental and analytical investigations about the elastic and viscoelastic (creep) behaviour of sandwich panels made of glass-fibre reinforced polymer faces and a polyethylene terephthalate foam core, produced by vacuum infusion for civil engineering structural applications. First, the elastic response of the panels’ constituent materials (glass-fibre reinforced polymer and polyethylene terephthalate) in tension, compression and shear was experimentally assessed; shear tests on the foam were carried out using a novel test method, the diagonal tension shear test. The creep behaviour in shear of the polyethylene terephthalate foam was evaluated for different load levels. The effective flexural properties of the full-scale sandwich panels as well as their flexural behaviour up to failure were experimentally assessed. Flexural creep and subsequent recovery experiments were also conducted for different load levels, to characterise the viscoelastic behaviour of the full-scale sandwich panels. Creep deformations of the polyethylene terephthalate foam and of the sandwich panels were found to be significantly lower than those corresponding to polyurethane foam and balsa wood reported in the literature; unrecoverable viscoelastic deformations were observed in the full-scale panels. In the analytical study, the creep response of the panels was modelled using Findley’s power law and the composite creep modelling approach. The composite creep modelling predictions were reasonably accurate and allowed assessing the relative contributions of bending and shear deformations to the total sandwich panel creep deflections.

Lifetime Performance of GFRP Pultruded Profiles for Structural Applications

This paper presents results of an ongoing experimental research performed at IST on two critical topics, regarding the use of glass fibre reinforced polymer (GFRP) pultruded profiles in structural applications: the long-term durability and the fire behaviour. The first part of this paper presents test results on the changes suffered by GFRP pultruded profiles under accelerated exposure to moisture, temperature and UV radiation. Although some reduction was observed in the mechanical properties, the durability tests proved the generally good long-term behaviour of this material. The second part of this paper presents results of experiments on the fire behaviour of GFRP profiles. Large-scale fire resistance tests on both unprotected and protected GFRP profiles (with different active and passive protection systems) were conducted to investigate the thermal and mechanical response of the material under fire and to determine the fire resistance and applicability of the investigated systems.

Structural Assessment of Reinforced-Concrete Arch Underpasses Subjected to Vehicular Overloads

In most countries, the maximum dimensions and weights of vehicles that circulate on national roads and highways are legally reg- ulated. However, several economic activities imply the circulation of exceptional vehicles or overloads, raising concerns not only about road surface deterioration but also about the structural safety of the bridges that are to be crossed. In a previous publication, the authors proposed a methodology for permit checking of vehicular overloads applicable to girder bridge decks that involves a comparison of code design-load effects with those resulting from the special vehicle being analyzed. The software developed therein (Bridge Investigation for Special Trucks (BIST))performsastructuralsafetyanalysisof thebridgesthataretobecrossed,providingsimplifiedsafetyfactors associatedwithaparticular overload, based on which the permit decision is made. This paper presents an update of the BIST software that extends the permit-checking methodology to underpass arch bridges. The first part of the paper describes the general methodology of BIST and its application to RC underpass arch bridges. Extension of the methodology involved the development of two- and three-dimensional finite-element (FE) models of a wide range of arch underpasses that were validated and calibrated based on full-scale experimental tests and the assumption of a set of proper conservative simplifications. The second part of the paper presents a study carried out to evaluate the conservativeness and accuracy of the method proposed by comparing the safety factors provided by BIST with those obtained from numerical models of real arch underpasses subjectedtoawiderangeofrealvehicularoverloads.ThesafetyfactorsprovidedbytheBIST softwarewerealwaysconservativeandreasonably accurate,therebyvalidatingthemethodologyproposedandenablingfast,economical,andsafepermitdecisionmaking.DOI:10.1061/(ASCE) CF.1943-5509.0000410.