Pll

12 EIb

3. The third assumption, which attempts to account for the flexibility of panel zones, results in bending moment and shear force diagrams for external and unit loads as shown in Figs. 8.31c(4), (8), (5), and (9). Integration of bending moment and shear force diagrams leads to the following expressions in Ac, Ab, and Ap:

The effect of panel zone continuity plates may be determined by performing a finite element analysis of a typical frame unit, as shown in Fig. 8.31d. A series of finite element analyses can be performed to relate the effect of panel zone to basic section properties of beam and columns of the typical unit. Halvorson (Ref. 64) indicates that for a typical

Figure 8.31d. Finite element idealization of typical frame unit.

13.08-ft-high by 15-ft-long (4- by 4.57-m) unit consisting of W 36 x 300 columns and W 36 x 230 beams, the frame stiffness is approximately 8, 15, or 22% stiffer than for a stick element model depending upon whether no, AISC minimum-, or full-continuity plates are provided, respectively.

Using the virtual work expressions given above, or by performing a finite element analysis, it is relatively easy to compute the contribution of panel zone deformation to frame drift. The author recommends that before undertaking the analysis of large tubelike frames, representative frame elements, say, at one-fourth, one-half, and three-fourths the height of the building, be analyzed to get a feel for the contribution of panel zone deformation to frame drift. Armed with the results, it is relatively easy to modify the properties of beam and columns such that the overall behavior of the frame is properly represented in the model.

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