Abstract
The present paper deals with an improvement of the strengthening technique consisting in the combined use of straps—made of stainless steel ribbons—and CFRP (Carbon Fiber Reinforced Polymer) strips, to increase the out-of-plane ultimate load of masonry walls. The straps of both the previous and the new combined technique pass from one face to the opposite face of the masonry wall through some holes made along the thickness, giving rise to a three-dimensional net of loop-shaped straps, closed on themselves. The new technique replaces the stainless steel ribbons with steel wire ropes, which form closed loops around the masonry units and the CFRP strips as in the previous technique. A turnbuckle for each steel wire rope allows the closure of the loops and provides the desired pre-tension to the straps. The mechanical coupling—given by the frictional forces—between the straps and the CFRP strips on the two faces of the masonry wall gives rise to an I-beam behavior that forces the CFRP strips to resist the load as if they were the two flanges of the same I-beam. Even the previous combined technique exploits the ideal I-beam mechanism, but the greater stiffness of the steel wire ropes compared to the stiffness of the steel ribbons makes the constraint between the facing CFRP strips stiffer. This gives the reinforced structural element a greater stiffness and delamination load. In particular, the experimental results show that the maximum load achievable with the second combined technique is much greater than the maximum load provided by the CFRP strips. Even the ultimate displacement turns out to be increased, allowing us to state that the second combined technique improves both strength and ductility. Since the CFRP strips of the combined technique run along the vertical direction of the wall, the ideal I-beam mechanism is particularly useful to counteract the hammering action provided by the floors on the perimeter walls, during an earthquake. Lastly, when the building suffers heavy structural damage due to a strong earthquake, the box-type behavior offered by the three-dimensional net of straps prevents the building from collapsing, acting as a device for safeguarding life.
Highlights
This paper is part of a research project on improving the out-of-plane behavior of masonry walls by combining different strengthening techniques [1,2,3,4]
Some flat steel bars allowed us to distribute the load along the middle cross-section, without compressing the straps and the upper carbon fiber reinforced polymer (CFRP) strip (Figure 46)
The combined technique discussed in this paper originates from the experimentation on a previous combined technique, useful for increasing the out-of-plane strength of masonry walls
Summary
This paper is part of a research project on improving the out-of-plane behavior of masonry walls by combining different strengthening techniques [1,2,3,4]. This modifies the limit surface of the interface bond—which becomes a cohesive physical bond—allowing the FRP strips to withstand higher shear forces before delaminating from the wall under bending loads. By providing compression forces only along the thickness of the wall, the straps of the CAM system, deprived of their original use, find a new employment in the combined technique as devices to system, deprived of their original use, find a new employment in the combined technique as devices push the strips against the masonry wall. On the stretched side of a bent wall, this modifies the interface bond of the FRP chemical to a chemical cohesive physical bondphysical (Figure 1), increasing theincreasing delamination load by meansload of the strips from to a cohesive bond (Figure 1), the delamination by frictional means of effect.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
