European Network for Durable Reinforcement and Rehabilitation Solutions

Contract Number: MC-ITN-2013-607851

FRP and MBC Strengthening of RC Walls with Openings

Cristian Sabau

Luleå University of Technology



Structures are continuously degrading due to environmental actions, lack of maintenance, or mechanical damage. Mechanical damage can be intended (e.g. demolishing a wall to enlarge a room) or accidental (e.g. explosions). In the last decades, the safety and functionality requirements for buildings have changed considerably, rendering a large part of the existing building stock unsuitable to current demands of the society. Upgrading existing buildings to new functional requirements may require new openings for windows, doors, or paths for ventilation that can weaken the structure and prompting the need for strengthening. In such cases traditional strengthening solutions such as creating a reinforced concrete or steel frame around the opening, imply long term restrictions in the use of the structure compared to solutions that use externally bonded composites such as fibre reinforced polymers (FRP). However, the latter have several inherent disadvantages, mainly related to the working environment toxicity and poor fire resistance.

Fabric-reinforced cementitious matrix (FRCM) composites are a new generation of externally bonded composites that can be an alternative for FRPs for strengthening buildings. FRCM is comprised of fibers, usually in the form of a fabric/textile with an open-mesh configuration, embedded in an inorganic mortar matrix. FRCM composites are relatively new compared to FRP composites thus their behavior is not completely understood.

The aim of this project was to investigate the applicability and efficiency of FRCM composites for strengthening reinforced concrete walls damaged by openings of different sizes. An experimental campaign on axially loaded reinforced concrete walls with openings strengthened with FRCM composites was conducted. The study was focused on the influence of openings size and FRCM composite properties on the axial capacity of the tested walls. Three dimensional image correlation systems were used to monitor the experimental tests to better understand the behaviour of strengthened members.

The experimental results revealed the FRCM composites are effective for strengthening reinforced concrete walls with openings. The FRCM strengthening can restore or even increase the capacity of walls with small openings above that of the initial solid wall. However, for walls with large openings the capacity increase provided by the FRCM composites is not enough to match that of the solid wall. Before FRCM solutions can be safely used in practice, future studies are required to study the durability of FRCM composites and the influence of sustained loads on the strengthening solutions.


Different types of test set-up, FRP bars and failure surfaces


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