Rehab-GFRP – Rehabilitation of Building Floors with Lightweight High Performance GFRP Sandwich Panels

National Science Foundation (FCT) Project PTDC/ECM/113041/2009

Partners IST, UM
Total funding 181,896.00€ IST funding 94,774.00€
Period 2011-2014




The rehabilitation of floors in old masonry buildings is a necessity in many rehabilitation projects. The use of traditional materials for this purpose, such as concrete or steel, introduces significant dead loads in constructions, increasing their seismic vulnerability, and posing constructive problems associated to transport, elevation and placement operations on narrow accesses. Composite sandwich construction may be used as an alternative to traditional materials, presenting several potential advantages, namely, higher strength-to-weight and stiffness-to-weight ratios, significantly lower overall weight, better behaviour in terms of insulation, lower maintenance needs, higher durability and lower life cycle costs.

The main goal of this project was the development of innovative composite sandwich panels for the replacement of degraded building floors, providing an easy solution for their rehabilitation. The design of the sandwich panels was carried out in accordance to structural and construction physics requirements for the envisaged application.

Two main types of sandwich panels were studied: (i) glass-fibre reinforced polymer (GFRP) panels, and (ii) hybrid GFRP-UDFRM (ultra-high ductility fibre reinforced mortar) panels. Prototypes of the sandwich panel designs were manufactured using an innovative vacuum infusion (VI) production process.

A comprehensive experimental campaign was carried out to study the mechanical behaviour of the panels and their constituent materials, and evaluate the best solutions for the sandwich panel floor system. During the course of the project, the experimental programme was adapted/extended, namely with the inclusion of additional tests that had not been considered in the original planning. These were related to aspects of the sandwich panels’ behaviour that proved to be very relevant for the envisaged application and were not sufficiently characterised in the literature: these include the creep behaviour of the sandwich panels and their constituent materials, and the effects of temperature on both their elastic and viscoelastic behaviour; due to their very high importance for the overall behaviour and design of the composite sandwich panels, the experimental programme needed to be adapted in order to allow also for a thorough characterisation of the materials and panels regarding the above mentioned aspects.

The experimental results were used to validate analytical and numerical models, which were developed to simulate the mechanical behaviour of the sandwich panels. Such models are essential to accurately predict the response of the panels, being particularly useful in their design and optimisation.

Connection solutions were also developed, designed, experimentally assessed and modelled using numerical methods. The studied connections included those between adjacent panels (panel-to-panel connections) and connections between the floors and the supporting masonry walls (panel-to-wall connections).

Additionally, the construction physics characteristics of the composite sandwich panel floors were also studied. In fact, their thermal and acoustic behaviour is of very high importance for the particular application in building floors, due to the requirements that must be met for the constructive solution to be considered viable. Analytical models for the prediction of the thermal and acoustic behaviours were developed and validated using the experimentally obtained data.

Finally, a user’s manual was developed for the design of sandwich panel floors, their production and on-site installation, thus guaranteeing the practical dissemination of the experience and knowledge gathered during the execution of this project. This document is intended to enable the use of this constructive solution by current civil engineering and construction practitioners.


Main publications

M.R.T. Arruda, M. Garrido, L.M.S. Castro, A.J.M. Ferreira, J.R. Correia, “Numerical modelling of the creep behaviour of GFRP sandwich panels using the Carrera Unified Formulation and Composite Creep Modelling”, Composite Structures, DOI: 10.1016/j.compstruct.2017.01.074, 2017.

M. Garrido, J.R. Correia, “Elastic and viscoelastic behaviour of sandwich panels with GFRP faces and PET foam core”, Journal of Sandwich Structures and Materials, DOI: 10.1177/1099636216657388, 2016.

M. Garrido, J.R. Correia, T. Keller, S. Cabral-Fonseca, “Creep of sandwich panels with longitudinal reinforcement ribs for civil engineering applications: experiments and composed creep modelling”, Journal of Composites for Construction, DOI: 10.1061/(ASCE)CC.1943-5614.0000735, 2016.

M. Garrido, J.R. Correia, T. Keller, “Effect of service temperature on the shear creep response of rigid polyurethane foam used in composite sandwich floor panels”, Construction and Building Materials, Vol. 118, pp. 235-244, 2016.

M. Garrido, J.R. Correia, T. Keller, “Effect of service temperature on the flexural creep of vacuum infused GFRP laminates used in sandwich floor panels”, Composites Part B: Engineering, Vol. 90, pp. 160-171, 2016.

M. Garrido, J.R. Correia, F.A. Branco, T. Keller, “Connection systems between composite sandwich floor panels and load-bearing walls for building rehabilitation”, Engineering Structures, Vol. 106, pp. 209-221, 2016.

M. Garrido, J.R. Correia, F.A. Branco, T. Keller, “Adhesively bonded connections between composite sandwich floor panels for building rehabilitation”, Composite Structures, Vol. 134, pp. 255-268, 2015.

M. Garrido, J.R. Correia, T. Keller, “Effects of elevated temperature on the shear response of PET and PUR foams used in composite sandwich panels”, Construction and Building Materials, Vol. 76, pp. 150-157, 2015.

M. Garrido, J.R. Correia, F.A. Branco, T. Keller, “Creep behaviour of sandwich panels with rigid PU foam core and GFRP faces: experimental tests and analytical modeling”, Journal of Composite Materials, Vol. 48, No. 18, pp. 2237-2249, 2014.

J.R. Correia, M. Garrido, J.A. Gonilha, F.A. Branco, L. Reis, “GFRP sandwich panels with PU foam and PP honeycomb cores for civil engineering structural applications: effects of introducing strengthening ribs”, International Journal of Structural Integrity, Vol. 3, No. 2, pp. 127-147, 2012.