Stiffening beams

Assume a fabricator is required to make a stiffened beam from a C-Mn steel to BS EN 10 025 1990 Grade Fe510Dl. He has obtained... 

The tTcuisverse T-stiffeners welded to the inside of the box-column sections were considered to behave compositely with the box-section wall as a simply supported beam spanning from corner to corner. For analysis purposes the effective width of box-section acting with the T-stiffener was take equal to the width of the T-section. Two percent of the maximum compression force along the longitudinal struts (stiffeners) were considered as point loads acting on the transverse T-stiffened beam section. 

Ductility limits for structural steel members are established such that gross member collapse due to failure of the member itself or its connections is precluded. It is presumed that local and gross member instabilities are prevented by providing adequate bracing and stiffeners. Shear failure modes are also to be precluded by design. Determination of failure mechanisms and corresponding capacities for flexural members and beam-columns arc adequately covered by the LRFD specifications. 

Stiffener - A steel beam on the outside of a tank being lined. They often act as a heat sink and will have an influence on cure state. 

Supporting beams are used to stiffen the trays, and the trays must be fastened securely to prevent movement caused by gas surges. To allow for thermal expansion and to facilitate installation, slotted bolt holes should be provided in the supporting rings, and there should be adequate clearance between the tray and shell wall. 

A vessel supported on two saddles can be considered as a simply supported beam, with an essentially uniform load, and the distribution of longitudinal axial bending moment will be as shown in Figure 13.22. Maxima occur at the supports and at mid-span. The theoretical optimum position of the supports to give the least maximum bending moment will be the position at which the maxima at the supports and at mid-span are equal in magnitude. For a uniformly loaded beam the position will be at 21 per cent of the span, in from each end. The saddle supports for a vessel will usually be located nearer the ends than this value, to make use of the stiffening effect of the ends. 

To provide adequate stiffness to the walls, gusset plates or T-bars should be welded vertically to the sides from top to the bottom, on the same center as on the I beam support. The bottom periphery of the walls is kept from flexing by its weld to the bottom plate. Similarly, the top should be stiffened, preferably by a channel, or at the least, by a heavy angle, which should be continuously welded completely around the top. The gusset or T plates should be welded to the channel at the top and at the bottom to the centers of the I beam supports, exactly opposite the web, to give optimum stability. A sketch (Figure 34) shows exactly how this should be done. 

In one case total internal collapse resulted in another, shell cxacjdng occurred Successful cures induded reducing fractkmal hole area, stiffening siqiport beams, and avoiding low c raat-... 

In one case total internal llapse resulted in another, shdl cracking occurred. Successful cures induded reducing fiactional hde area, stiffening sui rt beams, and avoiding low operating rates. 

Vtqxn fiom a forced-circulation rdwUer CEuised vibration. This resulted in loosening of tray fasteners and trtQr failure. Increasing nozzle size and stiffening the support beams solved the problem. 

Design allowables and analysis methodologies for FSW beam and skin-stiffened panel structures... 

However, the fabricator is a cautious man and, although he is confident that he will need no preheat, he designs his joint simulation test so that he can include test welds made with some preheat. He therefore makes the fabricated beam 2 m long, so that he can include three stiffeners staggered on either side of the beam as shown in Fig. 2.9. He also selects the plates which have the maximum CE of... 

Collar beam- Nominal 1- or 2-inch-thick members connecting opposite roof rafters. They serve to stiffen the roof structure. 

For local loads where a partial ring stiffener is to be used to reduce local stresses, the beam on elastic foundation method provides an ideal method for sizing the partial rings or stiffener plates. The stresses in the shell must then be analyzed by another local load procedure. Shell stresses can be checked by the beam-on-elastic-foundation method for continuous radial loads about the entire circumference of a vessel shell or ring. 

This procedure is based on the beam-on-elastic-foundation theory. The elastic foundation is the vessel shell and the beam is the partial ring stiffener. The stiffener must be designed to be stiff enough to transmit the load(s) uniformly over its full length. The flexibility of the vessel shell is taken into account. The length of the vessel must be at least 4.9v Rt to qualify for the infinitely long beam theory. 

Nb = number of bolts used in tail beam or flange lug N = width of flange of tail beam with a web stiffener (N = 1.0 without web stiffener) nL = number of head or side lugs P =pick end load, lb Pe = equivalent load, lb Pl = longitudinal load per lug, lb Pr = radial load, lb Pt = transverse load per lug, lb Rb = radius of base ring to neutral axis, in. 

I Conspicuity systems do not need to be installed to discontinuous surfaces such as outside ribs, stake post pickets on platform trailers, external protruding beams, or items of equipment such as door hinges and lamp bodies on trailers and body joints, stiffening beads, drip rails, and rolled surfaces on truck tractors. 

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