Ultimate Load Conditions

1 The ultimate load characteristics of structures type 1 and 2 were obtained using an ln- house computer program. This program examines a number of possible failure mechanisms In order to find the one associated with minimum potential energy of the vessel. The mechanisms are deflected In Increments, and at each step the vessel pressure which would maintain the mechanism In equilibrium Is found. Shears, deflections, prestress strains and crack sizes are output at each step so that the progressive plastic behaviour of the vessel may be monitored. Three failure criteria are recognised and overall vessel failure Is assumed to occur when one of the three Is violated. 

3 In modelling structure type 2 for the ultimate load analysis It was assumed that the planes of weakness zone could not carry tension. Any reinforcement tdilch was In this zone In the original structure was moved to a position just outside the planes of weakness zone. 

4 Results of the ultimate load analysis are presented In table 1. It will be seen that for structure type 2, a 20% Increase In the area of bonded reinforcement at the haunches (now moved outside the planes of weaknesb zone) Is necesary to achieve the same load factor as structure 1. In each of the three cases listed In table 1 the ultimate lo ul Is determined by the longitudinal barrel crack width reaching the allowable limit at the Interface with the vessel liner. Further work was carried out to determine the ultimate load behaviour of the vessel with all the bonded reinforcement removed. It was found that to achieve the same factor an Increase In the quantity of prestressing steel of over 30% was required. Whilst this might ease the decommissioning problem It would be very expensive. The gas In cracks condition has not been considered. 

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FIGURE 9.7 Free-head, short rigid piles—ultimate load conditions, (a) Rigid pile, (b) Cohesive soils,... 

The ultimate load condition, in which the vessel is incapable of sustaining any further increase of internal pressure, is a further limit state. Evaluation of the ultimate load provides a measure of the factor of safety above design conditions. 

It is assumed that smaller crack developed in major crack zones is progressively increased to 2 inch (50 mm) width at ultimate load and it is necessary to check the bursting stress in the bar and the bond length required at that stage, in Section 8.2.1.5, analysis is carried out to check the minimum GK-60 inch bond length of steel provided in the vessel. Previous research indicates that at ultimate load 15" (40 mm) dia. GK + 60 bar can span over 2" (50 mm) crack for a stress differential of 40,000 psi. Thus, at ultimate load conditions 2 no. 11" (30 mm) dia bars will still be a reasonable number to control the crack. The number of bars from Brice theory in this area comes out to be 3. Thus, in major crack zones, this number is maintained in either direction as shown in Fig. 8.1 and Table 8.1. 

For preliminary disposition of main bonded reinforcement, it is necessary to study carefully the vessel behaviour during elastic and ultimate load conditions and a proposed construction technique. After careful study of the vessel , general criterion for main bonded reinforcement is established. This criterion is indicated in Fig. 8.2. It covers preliminary requirements for general vessel areas and specific haunch and equatorial regions. A tensile stress of 1500 Ib/m (3.45 MN/m ) at working conditions, worse case of 600 psi (4.15 MN/m ) at ultimate load is also considered. 

Table 4.1 Factors of safety for ductile and brittle materials and various loading conditions (values shown in brackets from 1905, without brackets from 1965) (,S = ultimate tensile strength,, Sy = yield strength)...

In yet another example for a different commercial solid WPC board, the ultimate load at ambient conditions was 1521 28 lb (moisture content 0.34 0.04%) at support span of 16", flexural strength was 3,692 + 55 psi, and flexural modulus was... 

The English work was not without its critics. Jourawski did not consider it satisfactory to judge the strength of a construction by comparison with the magnitude of the ultimate load, since, as the load approaches the ultimate value, the stress conditions of the members of the structure may be completely different from those which occur under normal working conditions [49]. This comment typifies the confusion which existed at that time as to the best way of measuring the safety of a structure. 

Of greater importance is how well the physics-inspired model framework represents the governing micromechanisms, and ultimately, how well the model can predict the behavior of a given material under different loading conditions than that for which the model was originally calibrated. The simulations of the small punch test demonstrate that the HM provides satisfactory and valid predictions of large-deformation multiaxial behavior of conventional and highly crosslinked UHMWPEs. 

The results are shown in Figures 6 and 7. The panels were basically designed for a load level of 6623 N and the test shows that this value is much lower than the actual failure load obtained experimentally, which is around 35 to 45 kN (depending on the loading conditions). This means that the design load was around 20% of the ultimate value. One important feature of the curves obtained is that they exhibit a large linear portion up to quite high deflections. 

The structural Implications of Introducing planes of weakness Into the activated zone of a typical PCRV have been assessed under service load conditions, seismic loading and ultimate load. 

All of above computer methods are similar to the loaded process of static load testing, and the ultimate loads are estimated on the load-displacement curves of computations. Because the physical model of soils is different from the objective condition of... 

Shear strength reduction technique is also named as Strength Reduction Method (SRM), which is used in the stability analysis of slop. The essence of SRM is that the power parameters of geotechnical material (c, q>) decrease and slopes failure appear. At the condition of gravity force, Griffiths 0999) deduce the SRM formula of the slope and build the failure criterion. For pile foundation, the external force is transferred by the complex soil-pile interaction, the theory of pile foundation of SRM is different from slope of SRM, so the estimation of ultimate loading may need to revise or build the new limit analysis theory. 

At the limit condition, the ultimate load of pile was expressed by equation 4. 

The ultimate loads of pile, which were assessed by the static load test of pile, strength reduction method of FEM and increment load method of FEM, were given in Table 3. The limit condition of... 

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