Hinge deformations

Missing screws or rivets on steps Damaged, loose, or broken hinges Deformed, loose, or broken spreaders Damaged or missing support feet Side rails for cracks and damage... 

References 7, 64, and 72 through 75 discuss expected consequences at various levels of stmctural response deformation ratios or plastic hinge... 

Damage Level Deformation Ratio Plastic Hinge Rotation... 

The first step in developing a resistance function is to determine the plastic section capacities, such as plastic moment, Mp, as shown in Figure 7.1. The next step is to determine the sequence of plastic hinge formation and the corresponding load and deformation values. This is done by incrementally applying loads until a collapse mechanism is formed as illustrated in Figure 7.2 for a fixed end beam with a uniform load. 

Elastic Region - The deformation range from zero up to the formation of the first plastic hinge., ... 

Structural dements resist blast loads by developing an internal resistance based on material stress and section properties. To design or analyze the response of an element it is necessary to determine the relationship between resistance and deflection. In flexural response, stress rises in direct proportion to strain in the member. Because resistance is also a function of material stress, it also rises in proportion to strain. After the stress in the outer fibers reaches the yield limit, (lie relationship between stress and strain, and thus resistance, becomes nonlinear. As the outer fibers of the member continue to yield, stress in the interior of the section also begins to yield and a plastic hinge is formed at the locations of maximum moment in the member. If premature buckling is prevented, deformation continues as llic member absorbs load until rupture strains arc achieved. 

The details discussed or illustrated in this chapter are some of those that have been found to be cost effective and easily constructed. Structural steel connections are designed to move plastic hinge formation away from the connection and into the member. Reinforced concrete connections must provide full development of reinforcing with ties to permit extended plastic deformations, The design details included are not intended to limit the use of alternate designs. 

Hinge Rotation - A measure of the energy absorbing capacity of a structural member. This is the angle of deformation at a plastic hinge. 

In closing one should reemphasize an important point. We have stated that (dS/dz ) - 0 for all deformation coordinates, including mole numbers this in turn hinged on the experimental fact Cz - T (a 1). In Section 1.18 it was shown that Cz — T(8S/8T)Z therefore, (3S/3T)Z — T -1 must likewise approach zero. In other words, near the absolute zero of temperature the entropy, for anv process whatsoever, as far as its dependence on temperature T is concerned, approaches its lowest value with zero slope. 

When the force on the polymer material exceeds the fully plastic moment of the weakest element of the cell structure, plastic collapse occurs (characterized by region C in Figure 6.22). In effect, the weakest elements become a plastic hinge and deform to create a collapsing cell that responds to nearly constant stress (opl) with large deformations (see Figure 6.28). 

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