Interaction between Walking Humans and Structures in Vertical Direction: A Literature Review

Interaction between Walking Humans and Structures in Vertical Direction: A Literature Review Erfan Shahabpoor,1 Aleksandar Pavic,2 and Vitomir Racic3,4 1INSIGNEO Institute for In Silico Medicine, The University of Sheffield, Department of Civil & Structural Engineering, Sir Frederick Mappin Building, Mappin Street, Sheffield S1 3JD, UK 2College of Engineering, Mathematics and Physical Sciences, Vibration Engineering Section, University of Exeter, North Park Road, Exeter EX4 4QF, UK 3Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza di Leonardo Da Vinci 32, 20133 Milan, Italy 4Department of Civil & Structural Engineering, The University of Sheffield, Sir Frederick Mappin Building, Mappin Street, Sheffield S1 3JD, UK Received 19 March 2016; Accepted 27 April 2016 Academic Editor: Tai Thai Copyright © 2016 Erfan Shahabpoor et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Realistic simulation of the dynamic effects of walking pedestrians on structures is still a considerable challenge. This is mainly due to the inter- and intrasubject variability of humans and their bodies and difficult-to-predict loading scenarios, including multipedestrian walking traffic and unknown human-structure interaction (HSI) mechanisms. Over the past three decades, several attempts have been made to simulate walking HSI in the lateral direction. However, research into the mechanisms of this interaction in the vertical direction, despite its higher likelihood and critical importance, is fragmented and incoherent. It is, therefore, difficult to apply and codify. This paper critically reviews the efforts to date to simulate walking HSI in the vertical direction and highlights the key areas that need further investigation. 1. Introduction The vibration serviceability of many modern structures, such as footbridges, stadia, and long-span floors under human loading, increasingly governs their design and determines their cost. Inadequate consideration of the effects of walking pedestrians on structural performance can lead to a considerable financial loss, such as in the case of the infamous London Millennium Bridge in 2000 [1, 2]. It is particularly an issue today, with high aesthetic demands and new lightweight materials of increasing strength affecting the vibration serviceability performance. Regardless of its importance, recurring incidences of vibration serviceability failures due to walking pedestrians, in both the vertical and horizontal directions, have highlighted the inability of current design methods to reliably estimate the structural response [3, 4]. This unreliable performance is primarily due to virtually all design methods ignoring the human-structure interaction (HSI) and sometimes dismissing the natural inter- and intrasubject variability of people [4–8]. The excessive lateral vibration of the Paris Solferino Bridge and the London Millennium Bridge on their opening days triggered a wave of research on HSI in the lateral direction after 2000 [9]. However, the interaction of walking people with structures in the vertical direction, despite being much more frequent and relevant to everyday design practice, has sparsely been explored. HSI was initially considered to be nonexistent for moving humans [10]. However, it was subsequently demonstrated that it could have significant effects on the structural response [11]. Recently, a more realistic estimation of the structural vibration response was made possible by taking into account the inter- and intrasubject variability of the pedestrians in the form of statistical models of their walking force [6, 12–17]. This has considerably increased the fidelity of the walking force models, but they still struggle to capture key features of human-structure interaction (HSI) [4, 8]. The main reason is the lack of credible experimental data to understand and model HSI. In the context of the vibration serviceability of structures, HSI is defined here as the continuous mutual dynamic effects of a human and structure on each other that acts in a feedback loop as long as the structure and human on it are in contact. HSI is dependent on the human body posture and the type of activity [18] and can affect structural response through different mechanisms and in different directions. Based on the classification proposed by Sachse [19] and assuming the human body as a mass-spring-damper (MSD) system, HSI mechanisms can be divided into two categories. The first category comprises the effects of the human body (perceived as a dynamic system) on the dynamic properties of the structure, namely, mass, stiffness, and damping. The second category comprises the effects of the structural vibrations on the forces induced by human occupants. For walking people, this includes effects of the st (...truncated)