Some of the Latest Active Strengthening Techniques for Masonry Buildings: A Critical Analysis

Ferretti, Elena; Pascale, Giovanni

doi:10.3390/ma12071151

Cited by 22 publications

(22 citation statements)

References 32 publications

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“…Being aware of this last statement is of paramount importance for a structural engineer, as one of the main consequences of replacing Figure 6a with Figure 6b is that the value of stress in the straps becomes upper bounded. In other words, there is an upper limit value of the strap stress, which we cannot overcome without damaging the masonry [5]. integral part of the CAM patent, filed in 1999 by Dolce and Marnetto.…”

Section: Some Basic Notions Of the Cam Systemmentioning

confidence: 99%

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Combined Strengthening Techniques to Improve the Out-of-Plane Performance of Masonry Walls

Ferretti¹,

Pascale²

2019

Preprint

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The purpose of this study is to improve the performance of walls under out-of-plane loads, particularly when subjected to the hammering action of the floors. The idea behind the paper is to provide the masonry walls with a device that behaves like a buttress, without having to build a traditional buttress. The solution presented here consists of a mechanical coupling between the three-dimensional net of steel ribbons of the CAM system and the CFRP strips. Since the steel ribbons of the CAM system have a pre-tension, the mechanical coupling allows the steel ribbons to establish a semi-rigid transverse link between the CFRP strips bonded on two opposite sides of a wall. Therefore, two vertical CFRP strips tied by the steel ribbons behave like the flanges of an I-beam and the flexural strength of the ideal I-beam counteracts the out-of-plane displacements of the wall. The experimental results showed that the combined technique inherits the strong points of both constituent techniques: the delamination load is comparable to that of the specimens reinforced with the CFRP strips and the overall behavior is ductile as for the specimens reinforced with the CAM system. They also allowed us to design a more performing combined technique.

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Section: Some Basic Notions Of the Cam Systemmentioning

confidence: 99%

“…In [5], we have shown that the nodes of the rectangular CAM net are subjected to pairs of equal and opposite forces in the plane of the wall (Figure 5a). Consequently, they do not receive any in- plane force from the retrofitting system and do not have neither horizontal nor vertical displacements.…”

Section: Some Basic Notions Of the Cam Systemmentioning

confidence: 99%

Combined Strengthening Techniques to Improve the Out-of-Plane Performance of Masonry Walls

Ferretti¹,

Pascale²

2019

Preprint

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“…In its original use, where buttresses were structures built against or projecting from a wall, this ancient technique is effective but highly invasive and causes great increases in mass. As a result, with the advent of new technologies, buttresses were gradually abandoned in favor of more recent strengthening techniques, some of which are base isolation, seismic dampers, surface treatments, mortar joint treatments, external steel reinforcement, post-tensioning, mesh reinforcement, reticulatus system, confinement with ring beams, tie bars, and fiber/textile-reinforced mortar [2,[30][31][32]. The straps/strips combined technique recuperates the simple strengthening scheme of the buttress, but minimizing invasiveness and mass increases.…”

Section: Of 35mentioning

confidence: 99%

“…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]. The key-idea of the combined technique is to exploit friction in order to achieve a mechanical coupling between different strengthening devices.…”

Section: Introductionmentioning

confidence: 99%

“…The main target of the CAM system, patented in 1999 by Dolce and Marnetto, is to provide the wrapped masonry with an additional state of hydrostatic stress, which increases the safety factor of the masonry building. Nevertheless, a more accurate analysis of the actual stress-transfer mechanism from the CAM net to the masonry wall [2,3] showed that the additional state of stress provided by the CAM system is not hydrostatic. In the specific case of a rectangular CAM net, for instance, the nodes of the CAM net receive pairs of equal and opposite forces in the plane of the wall and not balanced forces in the thickness of the wall (Figure 3).…”

Section: Introductionmentioning

confidence: 99%

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

Ferretti¹

2019

Preprint

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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 strips, to increase the out-of-plane strength 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 placed on the two faces of the masonry wall gives rise to an I-beam behavior of the facing CFRP strips, which begin 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 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 actions provided by the floors on the perimeter walls, during an earthquake. Lastly, after the building went out of service, the box-type behavior offered by the three-dimensional net of straps prevents the building from collapsing, acting as a device for safeguarding life.

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Numerical assessment of a slender structure damaged during October 30, 2020, İzmir earthquake in Turkey

Demir

Altıok

2021

Bull Earthquake Eng

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Some of the Latest Active Strengthening Techniques for Masonry Buildings: A Critical Analysis

Cited by 22 publications

References 32 publications

Combined Strengthening Techniques to Improve the Out-of-Plane Performance of Masonry Walls

Combined Strengthening Techniques to Improve the Out-of-Plane Performance of Masonry Walls

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

Numerical assessment of a slender structure damaged during October 30, 2020, İzmir earthquake in Turkey

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