5923 3RD DR W 2018-01-02 MF Import

Pitzer & Assoziates 07-178 2SL IBC ver6-4.xmcd 4/16/2007 10_0 Overturninq Force Sample Calculation : NT IBC Section 16p.r.: /: -/ 1 The following example illustrates the calculations used to determine the overturning forces imposed on a shear wall under design forces. The shortest individual The design force applied at the top Elate of the shear wall is of interest. This is panel length on a grid line. calculated as the unit force (plf) in the wall multiplied by its length, representing vs;=5ft the design force applied. vWallLine.1 250. ft V:= vWallLine.1'ws v= 1250 lb Resistance to the applied design force comes from the dead load tributary to the wall. The following variables define the tributary w;dth of the Roof and Floor loads that act at this level. Dead loads from the level above are neglected as they were already considered in the calculations for the wall above. The tension from the wall above is added directly to the tension of the wall being calculated. Tm:= 10-ft Tributary Width of Roof supported by the wall Tfs:= 0.67•ft Tributary Width of Floor supported by the wall Tr2s:= 10-ft Tributary Width of Roof supported by the uplift section Tf2s:= 0.67-ft Tributary Width of Floor supported by the uplift section The level at which the design force is applied (top plate) was defined previously for the seismic mass. In the event that the plate height varies through sections of any given level, the height can be redefined to reflect the actual condition. Hmots.= H1 Height of Wall Hmols = 8 ft In order for a wall section to experience uplift, adjacent walls must be lifted as well. Assuming a 45 degree angle of failure from the lop plate, extending away from the shear panel, the equivalent length of wall to be lifted is assumed to be one half the height of the wall. We refer to this as the Uplift Section. Hmats Lo :-- _ Length of wall resisting uplift during overturning Le=4ft The dead load of the wall consists of contributions from the roof, floor, and wall. W - (Hmots'w's'WDL) - (Tfs'ws'FOL) - (Trs'ws'RD) W = 11841b The dead load of the uplift section also consists of contributions from the roof, floor, and wall. P (Lo.Tr21 RD) . (Lo Hmots WDL) - (Lo'Tf2s'FDL) P = 9471b TWaIILine.2 95lb An overturning moment is calculated by summing all forces about the compression corner of the shear panel. The result is the tension force required to resist uplift. Note the tension that is applied from the wall above. Top story wall calculations do not have an overturning tension from above. w rJV) Hmets' TWaIILine.2 ws� - 0.67 n .W - 0.67 P ws TWalll-ine.1 - w's TWaIILine.1 = 1064 lb Although not shown on the following pages, these same equations follow each set of data for each wall. They were placed in a minimized area of the calculations to shorten the calculation package, note the arrow and text "Overturning Calculations". At each of these locations, calculations (as above) are performed. 2SL Version 6.4 rage 10