Fully reversible reinforcement of softwood beams with unbonded composite plates

Marco Corradi,Antonio Borri,Giulio Castori,Emanuela Speranzini

doi:10.1016/j.compstruct.2016.04.014

Marco Corradi, Antonio Borri + Show 2 more

Open Access

https://doi.org/10.1016/j.compstruct.2016.04.014

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Abstract

In this paper, results of flexure tests aimed at improving the structural behavior of softwood beams reinforced with unglued composite plates and at developing an effective alternative to the use of organic resins are presented. The addition of modest ratios of GFRP (Glass Fiber Reinforced Polymer) composite strengthening can prevent tension failure in timber beams. However the application of organic matrices presents problems of reversibility, compatibility and durability with timber and poor performance at high temperatures. The increment in capacity and stiffness and the analysis of the failure modes is the central focus of this paper. The experimental campaign is dealing with a significant number of un-reinforced and reinforced beams strengthened with unbonded GFRP plates. A 3-dimensional finite element model is also presented for simulating the non-linear behavior of GFRP-reinforced softwood beams. The ability of the numerical model to reproduce experimental results for the load–deflection curves is validated.

Highlights

Softwood is from gymnosperm plants and it is the basis of approx. 85 % of the world’s production of wood elements
GFRP plates were reduced to a length of 1400 mm and were symmetrically applied on the beam’s tension side using different types of steel screws
The composite plates were anchored at the bottom of softwood beams using metal screws or bolts

Summary

INTRODUCTION

Softwood is from gymnosperm plants and it is the basis of approx. 85 % of the world’s production of wood elements. Softwood beams are usually replaced or reinforced with traditional methods involving the use of standard building materials such as steel or aluminum plates, or composite materials. For example the use of FRP composites to reinforce timber beams without organic oil-based adhesives (e.g. epoxy resins) is less established. The results of flexure tests on firwood beams reinforced using GFRP plates, applied on the tension side without the use of an organic adhesive, are presented in this paper. GFRP plates were reduced to a length of 1400 mm and were symmetrically applied on the beam’s tension side using different types of steel screws. These beams were reinforced with a single GFRP pre-drilled plate (Fig. 2). The mechanical properties of these plates are the same of the ones used for reinforcement of small beams

EXTERNAL STRENGTHENING

SHEAR CONNECTORS

METHODOLOGY AND TEST RESULTS

Findings

CONCLUSIONS