Excessive pedestrian-induced swaying in code-compliant walkways

Human-induced dynamic loads may trigger noisy vibrations on slender structures, affecting even their serviceability and compromising their use. This paper shows that current code-based design may not be effective enough in preventing excessive lateral vibrations of footbridges. By referring to the case history of the Assago-Forum walkway (Italy), it is shown that the widely adopted ES-ISO-10137 International Standard may, in fact, lead to underestimating-even significantly-the actual peak lateral accelerations in walkways and, consequently, it may erroneously consider structures safe against human-induced lateral vibrations when they are not actually so. The reason can be found in the extent to which the horizontal load code-based model is affected by the design scenario. By considering the horizontal actions relating to different code-compliant scenarios, a numerical dynamic analysis of the Assago-Forum walkway has been carried out. The results have then been compared with those obtained through a recently published, more advanced study. This investigation provides evidence that the design guidance given by ES-ISO-10137 against pedestrian-induced lateral vibrations of walkways may not be adequate. The paper also advances some suggestions on how code-based design might be improved.