Tensile failure zones

Beyond the shear failure zones, there are tensile failure zones caused by tensile stresses, which can be generally grouped into two distinct types, circumferential tensile failure zones and radial crack zones. 

Following the crashed zone, circumferential tensile failure zones with gray color in Figure 2 occur. This failure zones consist ofjustone surface of a crack. This crack could occur in any axial cross section planes around the tunnel axis and it is caused by the circumferential stress. Figure 4 shows the curves of dynamic stresses (a, a, ... 

The failure surface has been basically formed in past peak stage of axial stress, plastic zones of internal sample mainly focus on secondary failure surface. In past-peak 95%, shown in Fig. 5(c), the main failure surface of upper of specimen connects with secondary failure surface, failure surfaces of upper and bottom that connected with outer wall dmost connect. In past-peak 90%, shown in Fig. 5(d, e), due to failure surfaces connecting from upper of specimen to bottom, strength of specimen reduce. Compression is the main cause of failure surface, and failure zones of tension or shear mainly focus on the connected surface, the rest is rarely. In residue level, shown in Fig. 5(f), the change of tensile or shear is not very obvious. 

Figure 37 shows the bending stress distribution in a glulam beam and in a bipartite beam. The former has only one tensile peak zone, whilst the latter shows two peaks in the critical tensile zone. Thus the volume of the bipartite beam which suffers high tensile stresses is practically doubled as compared to the glulam beam. Assuming that the beam volume with 90-100% peak stresses to be critical, the timber volume subjected to peak stresses is increased from about 5% to 10%. Since the test results of this study indicate the same failure stresses for both cases, this may be an indication of a curved (and not linear) relationship between the failure stress level and the volume involved in the case of combined loading. 

Select low-temperature steels for fracture-critical structural members designed for tensile stress levels greater than a ksl (40 MPa) and specify a minimum Charpy V notch Impact energy absorption of 20 ft-lb (27 J) for base metal, heat-affected zones (HAZs), and welds when the structures are exposed to low-ambient temperatures. Fracture-critical members are those tension members whose failure would have a significant economic impact. 

The failure of PC in compression was violent. Compression cylinders would shatter violently and the remaining core of the cylinders had either a cone shape or a near vertical failure surface. Flexural beam specimens also failed in a violent manner as a tensile crack developed in the zone of maximum moment near mid-depth. The specimens were broken into almost two identical pieces and the failure surface was near vertical. The tensile bond strength between the PC overlays and the portland cement concrete substrate was found to be strongly dependent on the type of resin used. In overlay or repair applications, it is usually desirable to have tensile bond failures occurring in the portland cement concrete substrate rather than at the interface between the two materials. 

Effective stresses are affected in two different ways, an increase in total stress due to the mechanical loading of the ice sheet and a decrease in effective stress due to the increase in pore pressure. Consequently, changes in effective stresses are much less than expected from the mechanical stresses due to the weight of the ice sheet. Even in the dead-ended horizontal fracture zone in Section 2 Configuration 6 there is no hydraulic Jacking, i.e., no effective tensile stress. No shear failure has been predicted. There is practically no rotation of principal effective stresses. 

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