TB-Lecture12-Seismic-Forces-on-Buildings

# TB-Lecture12-Seismic-Forces-on-Buildings - EGN-5439 Design...

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EGN EGN -5439 Design of Tall Buildings 5439 Design of Tall Buildings Lecture 12 Lecture 12 Seismic Forces © L. Prieto-Portar, 2008

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Seismic Loads. Seismic loads are a combination of some formulas and factors that help you find each floor contribution to the reduction of the seismic load. Seismic loads do not have specific direction patterns. Seismic loads make structures sway back and forth like and inverted pendulum. Seismic loads subject the structures to lateral forces that are proportional to their weights.
Formulas Used (UBC): V = (ZIC/Rw)W C =1.25 S/T2/3 T = Cth3/4 Fx = (V-Ft) wxhx / (Swihi) Ft = 0.07TV Where: V: Design Base Shear Z: Seismic Zone Factor C: Coefficient Factor T: Period of Vibration W: otal Seismic Weight Rw: Numerical Coefficient I: Importance Factor S: Soil Factor Fx: Seismic Forces Ft: Top story Floor (Force) hx: Height of Each floor wrt Ground level hi: Summation of all floor heights

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Under seismic loads a building acts like an inverted pendulum:
The distribution of the seismic loads is at each story floor:

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Calculations for the seismic load at each story: F lo or Le ve ls W x= W i (k ips) hi= hx (ft) W ihi V (kip s) F x 1 4 15.96 9.84 3 356 298 2 370 .9 5 2 .5 3 2 4 15.96 1 9.68 3 356 298 2 370 .9 5 5 .0 7 3 4 15.96 2 9.52 3 356 298 2 370 .9 5 7 .6 0 4 4 15.96 3 9.36 3 356 298 2 370 .9 5 10.13 5 4 15.96 49 .2 3 356 298 2 370 .9 5 12.67 6 4 15.96 5 9.04 3 356 298 2 370 .9 5 15.20 7 4 15.96 6 8.88 3 356 298 2 370 .9 5 17.74 8 4 15.96 7 8.72 3 356 298 2 370 .9 5 20.27 9 4 15.96 8 8.56 3 356 298 2 370 .9 5 22.80 10 4 15.96 98 .4 3 356 298 2 370 .9 5 25.34 11 4 15.96 108 .2 4 3 356 298 2 370 .9 5 27.87 12 4 15.96 118 .0 8 3 356 298 2 370 .9 5 30.40 13 4 15.96 127 .9 2 3 356 298 2 370 .9 5 32.94 14 4 15.96 137 .7 6 3 356 298 2 370 .9 5 35.47 15 4 15.96 1 47.6 3 356 298 2 370 .9 5 38.01 16 4 15.96 157 .4 4 3 356 298 2 370 .9 5 40.54 17 4 15.96 167 .2 8 3 356 298 2 370 .9 5 43.07 18 4 15.96 177 .1 2 3 356 298 2 370 .9 5 45.61 19 4 15.96 186 .9 6 3 356 298 2 370 .9 5 48.14 20 4 15.96 1 96.8 3 356 298 2 370 .9 5 50.67 21 4 15.96 206 .6 4 3 356 298 2 370 .9 5 53.21 22 4 15.96 216 .4 8 3 356 298 2 370 .9 5 55.74 23 4 15.96 226 .3 2 3 356 298 2 370 .9 5 58.27 24 4 15.96 236 .1 6 3 356 298 2 370 .9 5 60.81 25 4 15.96 246 3 356 298 2 370 .9 5 63.34 26 4 15.96 255 .8 4 3 356 298 2 370 .9 5 65.88 27 4 15.96 265 .6 8 3 356 298 2 370 .9 5 68.41 28 4 15.96 275 .5 2 3 356 298 2 370 .9 5 70.94 29 4 15.96 285 .3 6 3 356 298 2 370 .9 5 73.48 30 4 15.96 2 95.2
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TB-Lecture12-Seismic-Forces-on-Buildings - EGN-5439 Design...

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