Slab

About: Slab is a research topic. Over the lifetime, 31617 publications have been published within this topic receiving 318693 citations.

The role of hydraulic fractures and intermediate-depth earthquakes in generating subduction-zone magmatism

Abstract: The presence of magmatism and intermediate-depth (70–300 km deep) seismicity at subduction zones is at first sight surprising. Magmatism is unexpected because the subduction of cool oceanic lithosphere makes these regions the coldest in the mantle. The current model for subduction-zone magmatism is that water released from the subducting slab enters the relatively warm mantle wedge, leading to a reduction in melting temperature and magmatism1, 2, 3, 4. But there is a problem with this scheme because it is thought that water cannot leave the slab by porous flow to enter the wedge. The occurrence of intermediate-depth earthquakes is surprising because of the inhibitory effect of the very high frictional stress on faults expected from the high pressure at these depths. One proposal put forward to explain intermediate-depth seismicity is that high pore-pressure might facilitate faulting by decreasing the friction5, 6, 7. The hypothesis presented here is that non-percolating water provides the high pore-pressure, that the consequent faulting temporarily interconnects the water pores and, when a sufficient vertical height of water is interconnected, a hydrofracture is produced which transports the water out into the mantle wedge, thereby generating subduction-zone magmatism.

Performance of connections for prefabricated timber-concrete composite floors

Abstract: Timber–concrete composite beams and slabs require interlayer connectors, which provide composite action in the cross-section. A range of mechanical connectors is available on the market with an extensive variety of stiffness and strength properties, which are fundamental design parameters for the composite structure. Another crucial parameter is the cost of the connector, including the labour cost, that if too high may prevent the use of the composite system. In order to reduce the construction cost and make timber–concrete structures more widespread on the market, it is believed that a high degree of prefabrication should be achieved. For a simple and cost effective construction process, the use of “dry” connections, which do not require the pouring and curing of concrete on site, may represent a possible solution. This paper reports the outcomes of an experimental programme aimed to investigate a number of different mechanical “dry–dry” connectors previously embedded into a prefabricated concrete slab. Direct shear tests on small blocks made of a glulam segment connected with a prefabricated concrete slab were performed. The shear force-relative slip relationships were measured and all the relevant mechanical properties such as slip moduli and shear strengths were calculated. It was found that some of the new developed connection systems for prefabricated concrete slab can perform as satisfactorily as those for cast-in-situ slabs, with the additional benefit of being relatively inexpensive.