Side wall loading

The side walls are defined relative to the explosion source as shown in Figure 3.6. These walls will experience less blast loading than the front wall, due to lack of overpressure reflection and to attenuation of the blast wave with distance from the explosion source. In certain cases, the actual side wall loading is combined with other blast induced forces (such as in-plane forces for exterior shear walls). The general form of side wall blast loading is shown in-Figure 3.8,... 

Side Wall Load (for shear wall interaction) equivalent peak overpressure, Pa = 5.7 psi (39 kPa) rise time, tr = essentially 0 sec time of duration, t = 0.05 sec peak load,... 

The side wall load has a rise time equal to the time it takes for the blast wave to travel across the element being considered. The overall duration is equal to this rise lime plus the duration of the free-field side-on overpressure. 

In terms of dead loads, the shape of the trench in which the pipe will be buried is also a factor. Generally speaking, a narrow trench with vertical sidewalls will impose less of a load on the pipe than will a wider trench with sloping side walls. It is necessary also to know the modulus of soil reaction (E), which is dependent on the type or classification of the native soil, the backfill material that is contemplated, and the desired consolidation of the backfill material. Soil consolidation is important, because it contributes to the strength of a flexible conduit in a buried pipe system. 

The loads from external near-surface burst explosions are based on hemispherical surface burst relationships. Peak pressure (P psi) and scaled. impulse Ci/W psi/lb ) are plotted vs. scaled distance (R/W ft/lb ). Roof and sidewall elements, side-on to the shock wave, see side-on loads (P and i ). The front wall, perpendicular to the shock wave, sees the much higher reflected shock wave loads (P and i ). An approximate triangular pressure-time relationship is shown in Figure 5a. The duration, T, is determined from the peak pressure and impulse by assuming a triangular load. Complete load calculations include dynamic loads on side-on elements, the effect of clearing times on reflected pressure durations, and load variations on structural elements due to their size and varying distance from the explosive source. 

For a building with a flat roof (pitch less than 10°) it is normally assumed that reflection does not occur when the blast wave travels horizontally. Consequently, the roof will experience the side-on overpressure combined with the dynamic wind pressure, the same as the side walls. The dynamic wind force on the roof acts in the opposite direction to the overpressure (upward). Also, consideration should be given to variation of the blast wave with distance and time as it travels across a roof element. The resulting roof loading, as shown in Figure 3.8, depends on the ratio of blast wave length to the span of the roof element and on its orientation relative to the direction of the blast wave. The effective peak overpressure for the roof elements are calculated using Equation 3.11 similar to the side wall. 

The shape of (he rear wall loading is similar to that for side and roof loads, however the rise time ami duration arc influenced by a not well understood pattern of spillover from the roof and side walls and from ground reflection effects. The rear wall blast load lags that for the front wall by L/U, the lime for the blast wave to travel the length, L, of the building. The effective peak overpressure is similar to that for side walls and is calculated using Equation 3.11 (Ph is normally used to designate the rear wall peak overpressure instead of P,). Available references indicate two distinct values for the rise lime and positive phase duration. 

The rear wall is proportioned the same as the front and side walls, spanning vertically from foundation to roof. Because the highest loads are on the front wall, a rear wall analysis would only be. necessary to determine a net loading on the overall building. The analysis will be for a wall segment 1 foot wide. 

Another possible protective scheme, although rarely used in the petrochemical industry, is a blast resistant barrier wall. A barrier wall can be used to provide protection from fragments and reduce reflected wall loads. However, it will not reduce overpressures on the roof and unprotected side walls. 

Load, psi (2 sides) (wall pane reaction, Ib/in] / (36 in girt spacing)... 

Load calculations braced frames 12-39—12-43 columns 11-37—11-40 exterior walls 11 4—11-10 foundations 11-41—11 45, 12-43—12-46 rigid frames 12-31 — 1 2-39 roof beams 1 1-27—1 1-31 roof decking 12-6—12-71 roof girders 1 1-36 roof putins 1 2-16—1 2-26 roof slabs, in-plane 1 1-1 1 — 1 1-16 roof slabs, out-ofplane 1 1-21—1 1-26 side walls, in-plane 11-16—11-20 wall girts 12-26—12-30 wall panels 12-12-12-16... 

The roof diaphragm is designed to transfer wall loads to the side shear walls. The diaphragm is fixed at both ends by continuous attachment to the walls. The center of mass coincides with the center of rigidity indicating no incidental torsion... 

Metal panels and girts along the long sides will load the main frames of the building, Loads on the back wall will be ignored to maximize Sidesway. Reactions form these members will be transferred to the frame. Loads on the side walls will be resisted by braced frames in the end bays. 

Since beverage cans, particularly two-piece cans, are made with very thin side walls, their ability to resist vertical top loads is limited. It is not until they have been filled with carbonated product and the product has reached room temperature that cans achieve full top-load strength. For non-carbonated products this can be a problem however, there are systems available which can inject a precise volume of liquid nitrogen into a filled can, just before the end is seamed on to the can body. As the liquid converts to a gaseous state, it expands. This helps to expel excess oxygen from the headspace, which may otherwise affect shelf life, and provides the internal pressure required for side-wall strength and package stability. 

Around 1890, oilseeds were pressed in manually loaded batch presses. Workers stacked layers of oilseed, separated by filter cloths and hollow pressing plates, into the press and applied pressure through a manually operated jack screw or a hydraulic cylinder. Oil flowed from the compressed material into the hollow plates and then out through the side walls of the press. After the oil stopped flowing, workers opened the press, placed the deoiled solids in a hopper, and recharged the press with fresh material. 

Experimental results were used to manufacture a fuUy bonded structural component of a rail vehicle side wall which was subsequently tested under static and dynamic loading conditions. FE-analysis was used for the design process of the component Test results are compared with FE-model predictions. 

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