System Identification & investigation of Human-Structure-Interaction (HSI) phenomena in differing biomechanical loading situations

Lead Research Organisation: University of Bristol
Department Name: Civil Engineering

Abstract

Human-Structure Interactions (HSI) is a severely misunderstood research area in engineering with a serious lack of full-scale experimental data from existing structures. It is of serious importance in the Civil and Structural disciplines due to the surprising complex behaviours observed in previous recorded incidents. For example, the sudden onset of lateral vibrations, wobbling, of the London Millennium Footbridge on its opening day and weekend. This has postulated the question of whether structures within and throughout cities are being constructed in the best manner. As advancements are constantly being made throughout the Science, Technology, Engineering & Mathematical (STEM) communities the need to understand unknown phenomena drives us to create a better world to live in. Civilian safety is of the upmost importance in the infrastructure of a city. Hence, the serviceability and maintenance of structures is crucial in ensuring it.

This research area is very unique in that it draws from a large spectrum of engineering disciplines, integrating a variety of concepts and principles, to get a complete understanding of the phenomena observed in HSI. The fields of biomechanics, nonlinear dynamics and crowd dynamics are of crucial importance. Can we effectively model human responses through biomechanical principals to identify and quantify the mechanisms observed between structures and people? How is it possible that the dynamic feedback in HSI produces complex and unexpected resonances?

This study aims to investigate the HSI phenomena in differing human loading situations. Specifically, in bridge and grandstand structures during human gait, jumping and bobbing. The framework of this study will comprise both theoretical and experimental work. Analysis of full-scale data from a crowd loading event of a bridge will be completed. System identification techniques will be used to effectively process and classify the data. It will be used to better understand and categorise the underlying mechanisms involved. Also, to validate and fine tune current biomechanical models. The theoretical scope will look at the application of nonlinear dynamics in the examination of these models. This will be supported by an in-depth parametric study using computational software, MATLAB, to simulate responses. The intention is to simplify them in a definitive way to hold the main characteristics and fundamentals whilst still providing accurate results. The objective is to develop this into a global system structure which can be used as a general case for design purposes.

The outcome of this research will create accurately refined dynamic models aiding in the design, construction and maintenance of civil and mechanical structures. It could lead to the advancements in system compensators such as inerters; for example, J Dampers in Formula One.

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509619/1 30/09/2016 29/09/2021
1963538 Studentship EP/N509619/1 03/09/2017 30/08/2022 Rory White
EP/R513179/1 30/09/2018 29/09/2023
1963538 Studentship EP/R513179/1 03/09/2017 30/08/2022 Rory White
 
Description Experimental study 1: Investigation of lateral human-structure interactions during crowd loading of a footbridge
The dynamic forcing of pedestrian's on a lively footbridge, from full-scale measurements, has been characterised for two seperate crowd loading events (Clifton Suspension Bridge). The dynamic, motion-dependent, mass force component of pedestrians has been quantified from full-scale measurements of a civil structure for the first time.

Experimental study 2: Investigation of non-linear dynamics of a human performing rhythmic jumping
The leg stiffness at significantly low jumping frequencies is observed to non-linear. A softening spring is observed, i.e. an increase in centre-of-mass compression corresponds to a small increase in force. After large deflections the force begins to decrease.

Experimental study 3: Investigation of human-structure interactions of a human performing rhythmic jumping on a perceptibly moving surface
The leg stiffness of a human has been quantified from direct measurements of force and displacement of the jumper and structure for this specific loading scenario. At low jumping frequencies, the force-displacement curves are approximately linear. At high jumping frequencies, the leg stiffness was observed to have two distinct stiffness profiles, one corresponding to the compressing stage and the other corresponding to the extending stage of the contact phase of the jump.

A double-jump phenomenon during different jumping frequency tests (for jumping frequencies above and below a moving surface's natural frequency) was observed and characterised from measurements of the jumper's centre-of-mass and foot displacements. This indicates that the jumping strategy of a person is very broad and can evolve during different jumping frequencies on a flexible structure. This is an example of emerging non-linear interactions arising from perceptible ground/surface input vertical vibrations. Experimentally validated for multiple test subjects over full experimental study.
Exploitation Route The evaluation of leg model parameters for jumping on both a rigid and moving surface (leg stiffness and damping) can aid the development of reduced-order models which capture the unique dynamics of a human performing rhythmic jumping. These models can be put forward to assist in design codes and regulations for construction of floors within civil buildings and tiers of grandstand structures.
Sectors Construction

Environment

 
Title https://doi.org/10.5523/bris.1y1ajsjpkpzom2qt10eg6pnjo0 
Description The data presented in this data repository corresponds to each individual figure from: White, R.E., Alexander, N.A., Macdonald, J.H.G. (2020) Characterisation of crowd lateral dynamic forcing from full-scale measurements on the Clifton Suspension Bridge, Structures, from Figure 2 to Figure 12. The csv file corresponds to each Figure which has been shortened to Fig. DOI: 10.5523/bris.1y1ajsjpkpzom2qt10eg6pnjo0 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact This database/dataset has provided supporting data for both Journal and conference papers published under the experimental investigation of the Clifton Suspension Bridge subject to crowd loading 
URL https://data.bris.ac.uk/data/dataset/1y1ajsjpkpzom2qt10eg6pnjo0