Hammering Actions

The purpose of this study is to improve the performance of walls under out-of-plane loads especially 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 in this paper consists of a mechanical coupling between the three-dimensional net of steel ribbons of the CAM (Active Confinement of Masonry) system and the CFRP (Carbon Fiber Reinforced Polymer) 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 the 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. In fact, the delamination load is comparable to that of the specimens reinforced with the CFRP strips and the overall behavior is as ductile as for the specimens reinforced with the CAM system. They also inspired a more performing combined technique.

Cetaceans (whales, dolphins and porpoises) rely heavily on sound for communication, foraging, predator avoidance, orientation, and navigation. Noise generated by offshore construction work, such as piling during wind-farm construction and conductor hammering during explorationdrilling operations, has the potential to cause behavioural changes, masking of communication signals or, in extreme cases, a temporary loss of hearing in marine mammals. Numerous countries have issued individual standards for offshore noise monitoring before, during and after construction, but few standards specify actual noise thresholds, due to the complexity of underwater environments. Underwater noise measurements were taken from an offshore support vessel, stationed at distances of 750 m, 1 km, and 2 km away from a drilling-rig conductor hammering site in the North Sea. Results were then compared with the only official threshold value, which was issued by the German Federal Environment Agency (UBA). Sound Pressure Level (SPL) at various measurement locations, and beyond was predicted. The Sound Exposure Level for conductor hammering noise was monitored in real time, and did not reach 160 dB re 1 µPa at a distance of 750 m, in accordance with the UBA. Given the known behaviour of porpoises around offshore installations, it is unlikely that animals were exposed to levels of sound that might be potentially detrimental in the single and brief 2 h period that conductor hammering occurred.

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: ...

One of the major concerns in the seismic retrofitting of masonry walls is that of increasing the ultimate load for out-of-plane forces. In multi-story buildings, these forces may originate from the hammering actions of floors, when the earthquake direction is orthogonal to the wall. A possibility for counteracting the out-of-plane displacements is retaining the wall by building some buttresses, that is, some beams lean against the wall and disposed vertically. Another possibility is to make the buttress in the thickness of the wall. In this second case, we must cut the wall for its entire height, realize the buttress, and restore the masonry wall around it. In both cases, the interventions are highly invasive. The first intervention also leads to increments of mass that enhance the attraction of seismic forces. The aim of this paper is to find a less invasive and lighter alternative for realizing buttresses. We proposed to use FRP strips and steel ribbons in a combined fashion, so a...

The present paper focuses on an in-situ testing programme recently developed in the Messina area, Italy, aiming at the assessment of the in-plane shear behaviour of traditional masonry structures retrofitted with the innovative CAM system (a system of 3D pre-tensioned stainless steel ties). The typical masonry of Messina area, is characterised by low mechanical properties, for its texture (bond) and for the bad quality of mortar, as well as lack of transverse connections. The high seismic risk characterizing the zone, amplifies the need for in-plane strengthening and transverse connection improvement. The CAM system, which uses masonry ties and active confining of masonry allows one to realise a 3D pre-tensioned tying system which is able to compact stones and mortar and improve the masonry mechanical characteristics. A full scale arch was cut from an ancient building and in-situ tests were carried out. First, the arch was horizontally in-plane loaded until first cracking appeared, ...

The present paper focuses on an in-situ testing programme recently developed in the Messina area, Italy, aiming at the assessment of the in-plane shear behaviour of traditional masonry structures retrofitted with the innovative CAM system (a system of 3D pre-tensioned stainless steel ties). The typical masonry of Messina area, is characterised by low mechanical properties, for its texture (bond) and for the bad quality of mortar, as well as lack of transverse connections. The high seismic risk characterizing the zone, amplifies the need for in-plane strengthening and transverse connection improvement. The CAM system, which uses masonry ties and active confining of masonry allows one to realise a 3D pre-tensioned tying system which is able to compact stones and mortar and improve the masonry mechanical characteristics. A full scale arch was cut from an ancient building and in-situ tests were carried out. First, the arch was horizontally in-plane loaded until first cracking appeared, then it was reinforced with CAM and reloaded until failure. The results of the experiments carried out have highlighted the advantages in using CAM, specially its ability to provide a large increase in terms of strength and ductility.

The purpose of this study is to improve the performance of walls under out-of-plane loads especially 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 in this paper consists of a mechanical coupling between the three-dimensional net of steel ribbons of the CAM (Active Confinement of Masonry) system and the CFRP (Carbon Fiber Reinforced Polymer) 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 the 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. In fact, the delamination load is comparable to that of the specimens reinforced with the CFRP strips and the overall behavior is as ductile as for the specimens reinforced with the CAM system. They also inspired a more performing combined technique.

One of the major concerns in the seismic retrofitting of masonry walls is that of increasing the ultimate load for out-of-plane forces. In multi-story buildings, these forces may originate from the hammering actions of floors, when the earthquake direction is orthogonal to the wall. A possibility for counteracting the out-of-plane displacements is retaining the wall by building some buttresses, that is, some beams lean against the wall and disposed vertically. Another possibility is to make the buttress in the thickness of the wall. In this second case, we must cut the wall for its entire height, realize the buttress, and restore the masonry wall around it. In both cases, the interventions are highly invasive. The first intervention also leads to increments of mass that enhance the attraction of seismic forces. The aim of this paper is to find a less invasive and lighter alternative for realizing buttresses. We proposed to use FRP strips and steel ribbons in a combined fashion, so as to realize an ideal vertical I-beam embedded into the wall, without requiring to cut the masonry. We also provided some experimental results for verifying the effectiveness of the model.

The Cell Method (CM) is applied here in order to investigate the failure mechanisms of masonry walls under shear force. The direction of propagation is computed step by step by the code, and the domain is updated by means of a propagation technique of nodal relaxation intraelement with re-meshing. The crack extension condition is studied in the Mohr/Coulomb plane, using the criterion of Leon. The direction of propagation is computed as the slope of the line joining the Mohr’s pole to the point tangent to the Leon limit surface.