Seminar Katrien Van Nimmen
Numerical and Experimental study of Dynamic Pedestrian-Structure Interaction
Location
Seminar room Boku 03.22
(Department of Civil Engineering, Kasteelpark Arenberg 40, B-3001 Heverlee)
Abstract
Due to the trend towards greater slenderness, footbridges are very often lively structures, prone to human induced vibrations. These footbridges are characterized by low natural frequencies, often in combination with low damping ratios, which may result into disturbing vibration levels under pedestrian excitation. Predicting the dynamic response of civil engineering structures due to crowd induced loading has become a critical aspect of the vibration serviceability design.
Current codes of practice enable the designer to perform a vibration serviceability check by predicting acceleration levels and providing corresponding comfort criteria. However, these guidelines apply highly simplified load models and there is a need for in situ validation together with an evaluation of their methodologies. In literature, different force models are available for one pedestrian and are combined in an attempt to represent crowd loading. The performance of these force models is however not representative for realistic loading conditions due to observed human-structure interaction. Two aspects of pedestrian-bridge interaction are important to consider: the effects of structural movement on human-induced dynamic forces and the influence of human occupants on the dynamic properties (mass, stiffness and damping) of the structures they occupy. An adequate experimental and analytical approach has to be taken to account for the complexity of the dynamic forces induced by pedestrians.
To include the aspects of human-structure interaction in the numerical simulation, the pedestrian is modeled as a mechanical system interacting with the flexible structure. The integrated (coupled) equations of the pedestrian-structure interaction are built by substituting for the dynamic interaction forces (an approach inspired by studies of vehicle-bridge interaction). Simulations show that existing dynamic human body models e.g. for standing and seated persons, originating from biomechanical and aerospace engineering, lead to very different results in comparison to the moving load model. The objective of the ongoing research, is the development of a mechanical model representing the human body in normal walking conditions, suited for civil engineering applications. An accurate model for the forces induced by one pedestrian is an essential step in the development of a mechanical model representing crowd-structure interaction.
The experimental approach is based on the cooperation with the Faculty of Kinesiology and Rehabilitation Science (FaBeR - Ilse Jonkers) and the Production Engineering, Machine Design and Automation (PMA Section - Friedl De Groote), and includes direct and indirect force measurements. In addition, the possibilities of the newly available 3D motion tracking measurement technique, originating from the movement science and entertainment industry, towards the behavior analysis of the pedestrian and the crowd in situ, are illustrated together with some initial results.
