Punching Shear Resistance of Slab-Column Connections under Monotonic and Reversed Cyclic Loading
Event details
| Date | 18.10.2010 |
| Hour | 12:15 |
| Speaker | Prof. Gustavo J. Parra-Montesinos, Univ. of Michigan |
| Location |
GC F1 11
|
| Category | Conferences - Seminars |
Flat plates or flat slabs are commonly used in reinforced concrete framed construction. The achievement of a uniform floor bottom surface and greater clear story height compared to regular beam-column frames makes this type of construction economical and architecturally appealing. The lack of beams, however, requires that special attention be paid to preventing punching shear failures in the connections between the slab and the supporting columns. For several decades the use of drop panels or capitals was the preferred option to increase the punching shear strength of slab-column connections. In the past few years, however, solutions that do not require a change in the slab thickness have become popular, such as the use of shear reinforcement in the form of headed studs.
Results from experimental research aimed at evaluating the effectiveness of two types of shear reinforcement in slab-column connections, headed studs and hooked steel fibers, will be presented. (...)
Test results indicate that hooked steel fibers are effective as punching shear reinforcement in slab-column connections. Under monotonically increased load, the use of fiber reinforcement in the connection region led to a substantial increase in shear strength with the potential of changing the slab failure mode from brittle shear failure to ductile flexural failure. Contrary to observations made by other researchers, the use of shear stud reinforcement did not lead to an increase in connection shear strength compared to slabs without shear reinforcement. After punching, however, the slabs with headed studs exhibited a relatively gradual strength decay compared to a nearly total loss of strength in the slabs without shear reinforcement.
Under a gravity shear ratio of ½ and bi-axial lateral displacement reversals, the use of fiber reinforcement allowed the slab to exhibit substantial flexural yielding prior to failing in punching shear, which occurred at drifts on the order of 3%. On the other hand, the slab-column connection with shear stud reinforcement failed in punching shear at a drift of approximately 1.6%. This failure was characterized by a breakout failure of the concrete engaged by the second line of studs, accompanied by severe bending of the rail supporting the studs.
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