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,... 

Rear wall loading is normally used only to determine the net overall frame loading. Because the rear wall load is opposite in direction to the front wall load, its inclusion tends to reduce the overall lateral blast force. Rear wall effects are many... 

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. 

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. 

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. 

M 5-1300 provides criteria computing the rear wall load as though it were an extension of the roof. Though graphs are provided to determine the rise time and duration, for most typical control builidngs, the positive phase will have a rise time of approximately S/U followed by a duration of td (Figure 3.1 Ob). 

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... 

Use tributary width method for applying load to frame for initial sizing (refer to Section 6.2.3). The tributary width will be equal to the frame spacing of 20 A (610 cm). Blast loads will consist of the externally applied roof and wall loads (refer to Section 12.3.3). 

Roof and wall loads are determined by the lowest resistance for each of the members. The roof deck has a resistance of 1.5 psi (10.3 kPa) while the purlins have a resistance of 0.5 psi (3.45 kPa). Thus the greatest load which can be transmitted to... 

The phosphors in the tricolor lamp show another advantage over the halophosphate phosphors, viz. a much better maintenance during lamp life. In Fig. 6.IS the output decrease after 2(KX) hours of burning is plotted as a function of the wall load. The higher stability of the rare-earth activated phosphors is translated into a higher maintenance. The value of the wall load is determined by the tube diameter (see Fig. 6.18). Tricolor and Special Deluxe lamps are now available in a tube diameter of 25 mm, to be compared with the 36 mm of the halophosphate tube. It even proved to be possible to reduce the tube diameter to 10 mm. With this small diameter the discharge tube can be fold up and the compact luminescent lamp is bom. 

Fig. 6.18. Ratio of the lamp outputs after 2000 and 100 hours of burning as a function of the wall load. Crosses are for a halophosphate lamp, circles for a tricolor lamp. Commercial lamp diameters are indicated. Reproduced with permission from Ref. [3]...

Columns and beams are important structural elements that support the loads placed on a building. A column is a vertical structural member that transfers loads to the structure s foundation. A beam is a horizontal structural member that supports roof or wall loads. 

The prediction of wall loads in bins is an important piece of information for their design. It is necessary to estimate the pressures at the wall which are generated when the bin is operated, in order to design the bin structure efficiently and economically. The approaches to the study of bin wall loads are varied and involve analytical and numerical techniques, such as finite-element analysis. Despite these varied approaches, it is clear that the loads are directly related to the flow pattern developed in the bin. The flow pattern in mass-flow bins is reasonably easy to predict but in funnel-flow bins such prediction becomes quite a difficult task. For this reason, unless there are compelling causes to do otherwise, bin shapes should be kept simple and symmetric. 

Laboratory Exercise Evaluation of Wall Loads in Silos... 

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