Stiffened frames

The back system s main function is to provide the transfer mechanism between the load shoulder straps and hip belt. Critical in this function, as with shoulder straps and hip belts, is the fit of the back system to the user, ideally using appropriate anthropometric data. The inclusion of stiffened frames (which mechanically join the shoitlder straps and hip belt) has been shown to be one of the most critical inclusions in a LCS design for mitigating injury potential. 

Structural adhesives are ideal for building up stressed skin or mono-coque assemblies, or just for applying stiffening frames to flat panels. It is a wise precaution to rivet points at which peel separation is a possibility whether under normal stress conditions or overload, as in unforeseen impact situations. 

Green, A K. and Bowyer, W. H., The development of improved attachment methods for stiffening frames on large GRP panels. Composites, January 1981, 49-55. 

FIG. 11-44 Typical construction of a tube bundle with plug headers (1) tube sheet (2) plug sheet (3) top and bottom plates (4) end plate (5) tube (6) pass partition (7) stiffener (8) plug (9) nozzle (10) side frame (11) tube spacer (12) tube-support cross member (13) tube keeper (14) vent (15) drain (16) instrument connection. (API Standard 661.)... 

Comer braces- Diagonal braces at the comers of the framed structure designed to stiffen and strengthen the wall. 

A high proportion of aerospace structures consist of relatively thin panels that are stiffened by stringers and frames or ribs. These panels are prone to buckle under compressive load and, in order to prevent delamination due to interlaminar shear stress, buckling is usually prevented up to ultimate levels of load. 

Frames. Two-dimensional parts consisting of wehs, stiffeners, and caps carrying bending and shear loads... 

Some representative structural elements are shown in Figure 6.1. As already mentioned, this classification is a matter of convenience. It does not mean that one cannot subdivide some of these elements into smaller components. For example, a stiffener or a frame can be broken down into webs and flanges. Nor does it mean one cannot lump some of these to form more complex elements, such as stiffened skins (Figure 6.1(b)). 

In this example, the Bayesian model updating method is applied to update the finite-element model of a three-dimensional six-story braced frame, which is based on a model of an actual laboratory test structure. It is square in plan with width a = 5 m. There are four columns for each floor, one at each comer. Each of them have interstory stiffnesses of 10 MN/m and 15 MN/m in the x and y directions, respectively. Furthermore, each face in each floor is stiffened by a brace and its stiffness is taken to be 20 MN/m. As a result, the interstory stiffness is 80 MN/m and 100 MN/m in the x and y directions, respectively. The floor mass is taken to be 10 metric tons for each floor. As a result, the first five modal frequencies of the stmcture are 3.432, 3.837, 6.305, 10.10 and 11.29 Hz. 

The panels, of overall dimensions 1.85 mxl m, are reinforced by closely spaced longitudinal glass FRF stiffeners, together with widely spaced transverse small glass FRF frames. Tests were carried out at two levels ... 

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