Punch type failure

The specimen is mounted in a punch-type shear fixture, and the punch (1 in. diameter) is pushed down at a rate of 0.05 in./min until the moving portion of the sample clears the stationary portion. Shear strength is calculated as the force per area sheared. Shear strength is particularly important in film and sheet products where failures from this type of load may occur (Fig. 2-21). This property can be used for comparison with other materials and for determination of the forces needed for punching openings (holes, etc.). 

The test is carried out by properly positioning the sample in the shear fixture and lowering the punch onto the specimen until a complete shear-type failure is observed. Shear strength is calculated as follows ... 

In most non-ductile frames, however, columns lose the capacity to sustain gravity loads due to shear and subsequent axial-load failures, and as a result, the coUapse mechanism is controlled by the loss in vertical load-bearing capacity. As outlined in Baradaran Shoraka (2013), this type of collapse of older concrete buildings may be precipitated by axial-load failure of coluirms, punching shear failure of slab-column coimec-tions, failure of slab-diaphragm connectitMis, or axial-load failure beam/column joints. 

Select 5 from the FTAPSUIT menu and BUILD starts by requesting the punch fi le name (e.g., dgn.pch or dg.pch depending on whether you want to run the original fault tree or the postprocessed fault tree. It requests the name to be given the importance input file (e.g., dg.ii) to select the type of input. Option 5 is pure probability, option 1 is failure rate. BUILD generates file FN.II for editing. 

Table (3) shows the results of punching tests. This results show that the upper layer of the system type 1 (8 mm mat) was already damaged at a fall height of 6 m the failure bound of this system was then estimated to be about 6 m. In the system type 5, however, the upper layer remained intact at a fall height of 6 m and was not yet damaged. 

When a fill layer of limited thickness is placed on top of a soft soil (e.g. very soft clay), a slice of the fill can be pushed downward into this soft layer. This punch through type of failure is sketched in Figure 8.15. Punch through may occur when... 

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