Strengthening Timber Structural Members with CFRP and GFRP: A State-of-the-Art Review

Abstract

The application of fibre-reinforced polymers (FRP) for strengthening timber structures has proven its efficiency in enhancing load-bearing capacity and, in some cases, the stiffness of structural elements, thus providing cost-effective and competitive alternatives both in new design and retrofitting existing historical buildings. Over the last few decades, several reinforcing materials and techniques evolved, and considerable progress was made in numerical modelling, especially using the finite element method. As this field of research has become extensive and diversified, as well as numerous contradicting results have emerged, a thorough review is necessary. This manuscript covers the topics of historical preliminaries, reinforcing with carbon and glass fibre composites, bond characteristics, main reinforcing techniques, modelling of knots, and the effects of the fibre waviness on the composite behaviour. A detailed overview is given on the experimental and numerical investigation of mechanics of strengthened beams. A one-of-a-kind table that compares the stiffness improvement observed in several studies with analytical estimates. Attention is drawn to a number of challenges that have arisen, e.g., the moderate stiffness enhancement, composite-to-wood interface, modelling of knots, and strengthening of defected timber members. This paper can be used as a starting point for future research and engineering projects.

Experimental, Analytical, and Numerical Assessments for the Controversial Elastic Stiffness Enhancement of CFRP-Strengthened Timber Beams

“…Several authors reported a low or moderate increase in stiffness resulting from FRP reinforcement. In a number of cases, the measured and predicted values significantly differ, as shown in a review article [ 26 ]. Therefore, we propose to improve the modelling by considering different moduli for tension ( ) and compression ( ) in timber.…”

“…It is apparent that results are scattered in a wide range and sometimes contradict expectations. A review comparison between the measured stiffness increase and the theoretical values obtained from calculations using classical beam theory was shown in [ 26 ] based on several research works processed. In some studies, the increase agreed with the theoretical estimates, e.g., [ 17 , 27 , 28 ], while the results contradicted the theoretical expectations in many other studies, e.g., [ 23 , 29 , 30 ].…”

High Performance Composites Based on Highly Filled Glass Fiber-Reinforced Polybenzoxazine for Post Application

“…CFRP can be used in some engineering with high bearing capacity and harsh corrosion environments due to its very excellent mechanical properties, fatigue resistance, and corrosion resistance even though it is a high price. While GFRP showed good mechanical properties with a low price, however, the long-term corrosion resistance and fatigue resistance are weak when facing some complex environmental exposure [ 1 , 2 , 3 ]. Over the past few years, the desire for fiber-reinforced polymer composites (non-metallic) has increased for dental fiber post applications such as carbon fiber, quartz fiber, and glass fiber posts to replace metallic posts due to the drawbacks of metallic posts, including their propensity for corrosion, root fractures, and loss of retention, as well as the rising desire for cosmetic restorations, all ceramic crowns must be supported by aesthetic posts [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ].…”

Reliability-based numerical analysis of glulam beams reinforced by CFRP plate

“…CFRP is durable, easily stick to timber and they are low-density materials. Besides, when they are used on the tension side of timber element, a significant amount of tensile stress is transferred from timber under bending which is allowing the timber compression side to yield 32 .…”