Retrofitting materials for enhanced blast performance of Structures: Recent advancement and challenges ahead

Goswami, Abhiroop; Adhikary, Satadru Das

doi:10.1016/j.conbuildmat.2019.01.188

“…Therefore, as for the first combined technique, the second combined technique acts as a reinforcement system before the structural damage occurs and a life-protecting device after the structural damage has occurred. This makes the second combined technique very effective in offering protection against damage caused by the hammering actions provided by earthquakes [55], as well as by impact [56][57][58][59][60] and blast [61][62][63][64][65].…”

Section: Discussionmentioning

confidence: 99%

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

Ferretti¹

2019

Preprint

0

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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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“…Therefore, as for the first combined technique, the second combined technique acts as both a reinforcement system and a protection device. This makes the second combined technique very effective in offering protection against damage caused by the hammering actions provided by earthquakes [58], as well as by impact [59][60][61][62][63] and blast [64][65][66][67][68].…”

Section: Discussionmentioning

confidence: 99%

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

Ferretti¹

2019

Preprint

1

0

View full text Add to dashboard Cite

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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“…The blast load is characterized by the instantaneous release of an enormous amount of energy, and depends on the explosive materials and the basis of their physical state [42]. Explosions are classified as far-range explosions when the offset distance is equal to or greater than 1.2 m/kg 1/3 ; and are classified as near-range explosions when the offset distance is less than 1.2 m/kg 1/3 .…”

Section: Pressures On the Structural Surfacesmentioning

confidence: 99%

Numerical Analysis for Critical Structures Protection against Blast Loading Using Metallic Panels

Alogla

¹

,

Helal

²

,

Elshafey³

et al. 2020

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The need for building protection against blast loads is a crucial issue nowadays due to the escalating threat of terrorist attacks, which affect people’s lives and critical structures. Consequently, design of protective panels to segregate building façades from the effect of a nearby explosion is required. Such design mainly depends on the ability of protective panels to mitigate and diffract the blast wave before reaching building façades. Five protective panel models with different designs, referred to as the Combined Protection System (CPS), are introduced in this paper. The main objective of this research was to achieve a design that could sustain a blast load with minimum plastic deformations. The introduced CPS designs included two steel plates linked by connector plates. The CPS dimensions were 3 m × 3 m × 0.35 m, representing length, width, and height, respectively. After that, the successful panel design was supported by placing these panels onto a masonry wall in different configurations. The protective panels were tested against 50 kg of trinitrotoluene (TNT) with a standoff distance of one meter. The final run of the optimum model was carried out using a blast load equivalent to 500 kg of TNT. The air–structure interactions were simulated using finite element analysis software called “ANSYS AUTODYN”, where the deformation of the panel was the governing parameter to evaluate the behavior of different designs. The analysis showed minimum deformation of the CPS design with vertical and horizontal connecting plates in a masonry wall distanced at 500 mm from the panel. However, the other designs showed promising results, which could make them suitable for critical structural protection on different scales.

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Retrofitting materials for enhanced blast performance of Structures: Recent advancement and challenges ahead

Cited by 56 publications

References 31 publications

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

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

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

Numerical Analysis for Critical Structures Protection against Blast Loading Using Metallic Panels

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