The use of Eurocode EN 1991-1-4 procedures 1 and 2 for building dynamics, a comparative study

The design of tall buildings has to ensure adequate reliability but it also has to ensure that people in the building feel comfortable particularly when subject to wind-induced vibrations. Fulfilling vibration criteria for human comfort is often decisive in the structural design of flexible tall buildings. The new Eurocode EN 1991-1-4 provides two different procedures to calculate the structural factor and the comfort level under along-wind forces. Both procedures are based on the same theoretical background but use different simplifications. On the basis of this the two procedures are compared. For the structural factor the differences between the two procedures and the theoretically correct values appear to be small. For the comfort level, however, larger differences occur. With respect to an accurate numerical evaluation of the theoretical expressions procedure 1 provides smaller values for the resonant response. This deviation increases for fundamental flexural modes with exponent larger than 1.0. For normal buildings the differences are considerable, but especially for wind-sensitive tall structures where resonant effects are important, procedure 2 is preferable for the determination of the comfort level.