Wire Ropes and CFRP Strips to Provide Masonry Walls with Out-Of-Plane Strengthening

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.

Active Confinement of Masonry Walls with Stainless Steel Straps: The Effect of Strap Arrangement on the in-Plane Behavior of Strength, Poisson’s Ratio, and Pseudo-Ductility

“…Seismic events impose two types of dominant loads on structures-the in-plane shear load (Figure 2a) and the out-of-plane bending load (Figure 2b)-which causes two types of dominant failure modes in URM structures [33,34]: the in-plane shear mechanisms and the out-of-plane bending mechanisms. The CAM ® system with a rectangular arrangement (Figure 1) is suitable for increasing the out-of-plane strength of masonry walls when used in conjunction with other strengthening systems [29,35,36]. In the plane of the wall, however, the rectangular arrangement does not bring any increase in strength or stiffness.…”

“…As anticipated in Section 1.1, the CAM ® system uses stainless steel rounded angles and funnel plates (Figure S1), which have the task of diffusing the action transmitted by the straps to the masonry. This experimental program replaced the stainless steel protective elements of the CAM ® system with the same protective elements as in [29,35,36], that is, 3D-printed elements made from a PLA (polymerized lactic acid) filament. The PLA filament is one of the most eco-friendly filaments in FDM (fused deposition modeling) 3D printing.…”

Seismic and Thermal Retrofitting of Masonry Buildings with Fiber Reinforced Composite Systems: A State of the Art Review

“…The plaster or mortar materials and fibers mixture consistency and therefore their usability is usually verified by the standard shaking table tests as reported in (Raut and Gomez, 2016;Formisano et al, 2017;2019). In addition, other physical properties are studied like Bulk density in (Raut and Gomez, 2016); the water absorption in (Benmansour et al, 2014;Raut and Gomez, 2016;Formisano et al, 2019) and the apparent porosity in (Raut and Gomez, 2016).…”

“…Strategies for seismic retrofitting(Ferretti, 2019) Preparation of composite plaster (Aizi and Kaid-Harche, 2020) Polypropylene fiber(Mustafaraj et al, 2020) Ferrocement retrofitting scheme (Wang et al, 2018) Shotcrete spraying process(Wang et al, 2018) …”

Improving stability of an ecological 3D-printed house- A case study in Italy

“…The Crane WASP house is simulated with rammed earth characterized by a horizontally striped and compacted layer by layer [21], and the basic principles of seismic justification are similar to unreinforced mansory. According to many scholars, There are many techniques to improve the strength of Unreinforced Mansory (URM) like Wire Ropes and Carbon Fiber Reinforced Polymer strips (CFRP) [22,23]. In our study After defining the characteristics values of geotechnical parameters for the material, Robot Structural Analysis Software is used to analyze the Mechanical resistance of the studied structures and Response spectrum analysis which measures the Maximum acceleration influenced by the different frequency and damping coefficient is put to test, we propose also a new design in terms of positioning natural columns and beams inside the earthen wall with a test of seismic stability for each one of them in order to demonstrate that adding circular wall can improve the stability of the building.…”