Contact Force Reconstruction from the Lower-Back Accelerations during Walking on Vibrating Surfaces

Jeroen Van Hauwermeiren,Benedicte Vanwanseele,Katrien Van Nimmen,Peter Van Den Broeck

doi:10.3390/vibration4010015

Abstract

Current models describing the effect of crowd-induced loading require a full-scale validation. To measure the lower-back accelerations during such validation, low-cost accelerometers are used to ensure a sufficient scalability. The goal is to verify to what extent the low-cost sensors can be used for the contact force reconstruction in case the pedestrian walks on a vibrating surface. First, a data set is collected comprising the simultaneous registration of the lower-back accelerations and the contact forces. Three contact force reconstruction methods are presented to accurately reconstruct the contact force in case of walking on a rigid surface. Second, the focus is on the contact force reconstruction in case of walking on a vibrating surface. A numerical study is performed adopting quantities of the Eeklo Benchmark Dataset providing a realistic framework. The additional lower-back accelerations as a result of the vibrating surface are estimated numerically. It is found that directly reconstructing the total contact force leads to inaccurate results. Instead, it is more suited to reconstruct the contact force one would induce on a rigid surface and combine this with an independent model to account for human–structure interaction. The conclusions of this numerical example are case-specific while the presented methodology is generic and can be readily extended to virtually any other structure.

Highlights

As a result of ever increasing lighter and stronger materials, footbridge design today is often dominated by its vibrations’ serviceability [1]
The cross-validation is performed with a transfer function that is established on other participants than those of the cross-reference group
The reconstruction error is nearly identical for all reconstruction methods, and is low compared to the sensitivity of the response to mechanical human–structure interaction (HSI)

Summary

Introduction

As a result of ever increasing lighter and stronger materials, footbridge design today is often dominated by its vibrations’ serviceability [1]. Mechanical HSI comprises the phenomenon that a walking crowd on a footbridge induces forces, and adds stiffness, damping, and mass to the structure. Normative design codes neglect the effect of mechanical HSI or only account for the added mass effect [5,6] This is a result of the absence of fullscale validation of this phenomenon [2]. Given the scale of the application with up to 148 participants, low-cost accelerometers were employed instead of the conventional sensors. The scope of the present work is to investigate how the employed low-cost sensors can be used to reconstruct the contact forces while accounting for the fact that the pedestrians are walking on a vibrating instead of a rigid surface

Methods

Results

Conclusion