Structural Damping of Glazed Facades and Resulting Risk of Vibration under Along Wind Excitations

Abstract

The authors investigate the dynamic factor dependency on the major wind excitation parameters, including mean wind velocity, turbulence factor and system dynamic properties, by means of the Single Degree of Freedom (SDOF) simplification. The reason of the research is the controversial limit stated in the EN1991-1-4:2005, set to 5Hz, which represents the minimum value of the system first natural frequency allowing to ignore dynamic amplification factors to incorporate into the equivalent static approach. While the largest part of the scientific community aims at reducing this value, to avoid additional useless reinforcements and checks, other researchers have identified testing conditions for which vibrations occurred even for natural frequencies up to 14Hz. The authors start from the analysis undertaken in their previous work, identifying damping as the decisive parameter. Differently from what is reported in several literature studies, working conditions of glazed façades result often in equivalent structural damping larger than the minimum values assumed in numerical calculations. By means of other experimental data, it will be shown that an indiscriminate reduction of the 5Hz limit would be probably unsafe. Recommendations will be given in order to run specific experimental investigations to solve the inconsistent literature experiences and to the address the limit in future standards in dependency on specific combinations of wind and system dynamic properties.