Flexure diaphragm

Another problem that arises when using fiber element has to do with the selection of the control point. The original N2 method was developed for shear frames and can be easily applied to frames with floor diaphragms which are rigid in their plane. When the beams are modeled with fiber elements, floor diaphragms cannot be used, because they introduce artificial compression due to the fact that the beams cannot freely extend. Because the beams are normally axially suffer, almost any point can be selected. However, in older buildings with few beams and thin slabs the floor can become quite flexible in its plane and thus some differences can be expected in the horizontal displacements over a floor. Also, slabs have to be modeled with either shell elements or with equivalent bar elements (which ignore the flexural stiffness of the slabs). 

Flexural characteristics are of paramount importance in applications involving movement or vibration of parts. Valve diaphragms are an example of a part in which the membrane experiences repetitive movement. Flexural or flex life is defined as the number of cycles that a part can endure before catastrophic fatigue occurs the higher the molecular weight the higher the flex life. Increased crystallinity has a detrimental effect on the flex life the higher the crystallinity the lower... 

Three different levels of detail are shown in Fig. 2, for the NRHA of an unreinforced masonry (URM) house. Figure 2a shows an equivalent frame model, in which masonry pier flexural and shear responses are modeled with nonlinear spring or link elements. For this model, the mass is lumped at an equivalent roof height, and a rigid diaphragm connects the mass to the tops of each... 

Normally a cast-in-place solid slab qualifies as a diaphragm, if it is monolithically coimected to the elements of the lateral-force-resisting system and has thickness and two-way reinforcement which meet the requirements of design codes concerning the flexural strength under factored gravity loads, the limits on deflection and crack width under service loads, and the minimum slab reinforcement. 

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