Dynamic response of rooftop billboards excited by fluctuating wind loads

Abstract

As typical wind-sensitive structures, the wind-induced dynamic response of rooftop billboards and their dynamic interaction with the host building are critical issues in wind-resistant design. This study systematically investigates the dynamic response of steel billboards situated on multi-story reinforced concrete buildings by establishing a three-dimensional finite element model of the coupled billboard-building system. Fluctuating wind loads are simulated using the harmonic superposition method, and dynamic responses are analyzed through time-history analysis. The feasibility of a stiffness-proportional damping model is evaluated. A comparison with a sole billboard system reveals the significant influence of the building on the billboard’s dynamic response and its underlying mechanism. The results demonstrate a non-negligible dynamic interaction between the host building and the rooftop billboard, with the influence coefficient for the peak base bending moment exceeding ±20%. This dynamic interaction is identified as modal coupling within the coupled system. When the first and second natural frequencies of the system are close, strong modal coupling occurs, leading to a redistribution of energy that can significantly amplify or diminish the billboard’s dynamic response. The findings imply that the conventional design practice of analyzing rooftop billboards as isolated structures with fixed bases may be inaccurate, and the dynamic interaction within the coupled billboard-building system should be considered.