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Improved Interface Bond Relationships of FRP-Strengthened Masonry Structures through Experimental and Numerical Simulations

Hashemi, S. M. (2023). Improved Interface Bond Relationships of FRP-Strengthened Masonry Structures through Experimental and Numerical Simulations. (Unpublished Doctoral thesis, City, University of London)


Masonry walls are vulnerable to extreme loading and fibre-reinforced polymer (FRP) composites are a good solution for the reinforcement of un-reinforced masonry (URM) walls exposed to in-plane or out-of-plane loads. Collapse of walls in masonry structures is one of the main reasons for material damage and people’s injury due to earthquakes. Thus, the investigation of effective and inexpensive methods for strengthening masonry walls is crucial. FRP composites have many benefits, such as a high strength-to-weight ratio, and ease of application in terms of workforce and time. The behaviour of masonry walls can be improved by retrofitting with fibre reinforced polymeric (FRP). Reinforcement of masonry walls with FRP, can increase strength and ductility and thus reduce the risk of failure under extreme loading. However, the reinforcement of cracked masonry walls and the interface and bond behaviour between brick and mortar, especially in the case of retrofitting with FRP, has not been carefully studied.

The main aim of this research is to investigate the bond behaviour of different carbon fibre-reinforced polymer (CFRP) configurations on masonry structures when subjected to compressive and shear loads. Also, the experimental shear tests on cracked triplet masonry strengthened with different configurations of CFRP were carried out which had not been studied before. The experimental work was carried out with seven different CFRP configurations and layers on triplet masonry and each test was repeated four times. In addition, finite element modelling by the commercial software Ansys and verification against results from experimental tests were carried out.

The present study has shown the strength of masonry triplets with CFRP under compression loads was increased up to 3 times and under shear loads, all types of reinforced triplets were at least 4 to 6 times stronger than triplets without CFRP. Comparing one and two layers of CFRP wrap or CFRP strips on triplet masonry showed that there is no significant bond improvement between one layer and two layers. Depending on CFRP configurations, two layers make triplets 5% to 15% stronger, which is not sufficient. The cracked triplet samples repaired with CFRP and tested under shear loading showed significant improvement in bond strength and the load capacity of triplet masonry increased by 3 to 5 times in comparison with samples without initial damage.

Finally, based on test results to predict the shear strength of masonry triplets with and without CFRP new formulas for bond behaviour were developed. In addition, for an accurate finite element modeling (FE), these formulas were added as the new user-defined functions (UDF), in the commercial software Ansys. The outcome of this thesis improves the current knowledge on the use of CFRP to reinforce masonry walls with brick and mortar which will contribute to the understanding of the effect of CFRP on masonry structures. Conclusions are provided and future research needs in the area of masonry strengthening with CFRP are outlined.

Publication Type: Thesis (Doctoral)
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Departments: School of Science & Technology > Engineering > Civil Engineering
School of Science & Technology > School of Science & Technology Doctoral Theses
Doctoral Theses
[thumbnail of Hashemi Thesis 2023 PDF-A.pdf] Text - Accepted Version
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