Modeling masonry walls under far-field and contact detonations

Michaloudis, Georgios; Gebbeken, Norbert

doi:10.1016/j.ijimpeng.2018.09.019

“…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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“…Li et al [26] investigated through experimental and numerical studies the response of un-reinforced clay brick masonry walls subjected to vented gas explosions. More recently, Michaloudis and Gebbeken [34] analysed the response of unreinforced masonry walls constrained to rigid supports and subjected to far-field and contact explosions. The approach was both experimental and numerical.…”

Section: Introductionmentioning

confidence: 99%

“…Blast loads are computed using a dynamic library which accounts for the effect of surface rotation of building blocks as well as the evolution in time of their relative distance with respect to the impinging blast wave, as discussed in Section 3. In Section 4, the model is validated with the available experimental results in [34], and, in Section 5, numerical tests are performed to investigate the influence of the micro-mechanical and geometric parameters on the response of a curvilinear masonry structure to surface blasts. Finally, we explore the appropriateness of a rigid blocks assumption in the DE simulations in Section 6.…”

Section: Introductionmentioning

confidence: 99%

A Discrete Element Method based-approach for arched masonry structures under blast loads

Masi

¹

,

Stefanou

²

,

Maffi-Berthier

³

et al. 2020

Engineering Structures

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Masonry structures are often characterized by complex, non-planar geometries. This is also the case for historical and monumental structures. Here we investigate the dynamic behaviour of non-standard, curvilinear masonry geometries, such as vaults, subjected to blast loading. We use the Discrete Element Method (DEM) for modelling the dynamic structural response to explosions. The approach allows considering the detailed mechanical and geometrical characteristics of masonry, as well as the inherent coupling between the in-and out-of-plane motion. The proposed modelling approach is validated with existing experimental tests in the case of planar masonry geometries, walls, subjected to far-field explosions. The DEM model is found to satisfactorily capture the dynamic response of the system and the form of failure within the body of the masonry structure. Then the response of an emblematic curved masonry structure subjected to blast loading is investigated. The influence of various micro-mechanical parameters, such as the dilatancy angle, the tensile strength and the cohesion of the masonry joints on the overall dynamic structural response of the system is explored. The effect of the size of the building blocks is also studied. Masonry joints with zero dilatancy lead to increased out-of-plane deformations and reduced membrane ones, with respect to associative case. Cohesion and tensile strength are found to have negligible influence on the structural response. The size of the building blocks shapes the overall strength of the system. Finally, the performance of a discrete model with infinitely rigid blocks is explored and evaluated through detailed comparisons of the parametric numerical tests using deformable blocks. The rigid blocks model predictions, for the loading conditions and geometries here investigated, are found to be affected by the rotational locking effect.

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Modeling masonry walls under far-field and contact detonations

Cited by 34 publications

References 16 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

A Discrete Element Method based-approach for arched masonry structures under blast loads

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