Roof Drift Ratio

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Roof drift ratio.

D e 5 rdr c h 2 similarly the maximum inelastic inter story drift ratio isdr is given as 1 1 max isdr i e i c h d s i 3. Such a measure of displacement is a good proxy for measuring the damage done to the building as it should be reasonable that the greater the displacement of a building the more damage is caused during the. The magnitude of this maximum was similar in both principal building axes. Story drift determination asce 7 16 figure 12 8 2.

Expected drift ok since roof rafters are prismatic 35 gable drifts others. Failure was eventually dominated by shear as shown in figure 3. The maximum story drift calculated earlier using mrsa reached a maximum value at the roof level equal to 89 percent of the 0 010 h sx limit prescribed in standard section 12 12 1. For the wind design the interstory drift ratios under 1 10 year storms were less than 1 400 and the roof drift ratio was less than 1 500 which was achieved through the 2 added damping from the vcds in the primary mode of vibration.

The roof drift ratio is the ratio of the displacement of the roof of a building relative to the ground compared to the height of the building as illustrated in the figure below. The response quantities utilized in the comparisons of the case study smrfs were the inter story drift ratio roof drift ratio base shear coefficients and time history of displacement in. The maximum top story i e roof inelastic drift ratio rdr is calculated by dividing the top story inelastic deflection by building height. The maximum roof drift ratio reached was 13 4.

The elastic displacement is the absolute lateral displacement of any point in the structure relative to its base under strength level design earthquake forces. For seismic load applications section 12 12 1 of asce7 10 states that the design story drift of the structure shall not exceed the allowable drift listed in table 12 12 1. Actually the model parameters lateral stiffness ratio α damping ratio ξ and number of modes m of buildings which are equivalently taken as shear flexural beams affect the generalized interstory drift spectrum subjected to three representative near fault ground motions in table 1 with the close pga i e. For light frame buildings the maximum permitted drift is 2 5 of the story height.

The story drift is calculated as the relative elastic displacement of a story to the story below as shown in figure 1. Code suitable relation for drift ratio dr 4 53 w 2 1 66 p g 262 l u 295 drift size becomes drift size ftwidth dr pglu drift size 4 53 w 2 1 66 p g 738 l u 705 51 winter. Shear deformation became significant when the roof drift ratio reached 1.