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The Interstorey Drift Sensitivity Coefficient in Calculating Seismic Building Frames



Author(s)

J. M. Martínez Valle, J. M. Martínez Jiménez and P. Martínez Jiménez

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DOI:10.17265/2328-2193/2016.01.001

In calculating the seismic response of a building, the Spanish Instructions NCSE-02 and CTE, paragraph 3.7.7 (also EUROCODE 8 paragraph 1.2 part 1-1), establish that if for all storeys the interstorey drift sensitivity coefficient, ξ, is less than or equal to 0.1, then it will not be necessary to consider the effects of the 2nd order ( P-Δ effects). In this paper the authors review this claim, because even for ξ ≤ 0.1 , increases of the bending moment at the ends of the columns due to the inclusion of second order effects can account for between 15% and 34% of its value for static service loads. This is significant since most adverse effects are shown in the lower height buildings (up to 5 floors) which it is precisely the range in which most of the housing stock of Spain is located. Finally, the authors delimit the coefficient for buildings of lesser height (up to 5 floors), proposing to lower it generally to ξ ≤ 0.06 .

Seismic analysis, interstorey drift sensitivity coefficient.