A Fast Automated Impact Hammer Test Method for Modal Parameter Extraction: Implementation on a Composite Bridge Beam

The experimental modal properties of subs-structures of larger civil engineering structures are rarely measured on-site. In fact, usually, their dynamic characteristics are only evaluated numerically. There are a number of reasons for the lack of experimental verifications, but most probably these are due to the time and cost required to obtain the experimental modal parameters accurately within the context of challenging environmental on-site conditions. For smaller civil engineering structures, experimental dynamic testing significantly increases the overheads of the overall cost of the construction. This paper presents a dynamic identification method based only on experimental and statistical procedures, which highlights and solves some of the practical aspects of experimental identification, allowing extraction of the main modal properties speedily with a reduced cost of human resources and instrumentation. The methodology is described using as an example a composite bridge-beam, made of concrete and fibre-reinforced composite material, which constitutes the first composite bridge applied on a motorway in Europe. The use of the reciprocity of the transfer functions combined with some self-checks of the measurements is shown to be an efficient way to speed up the signal processing, without reducing the accuracy of the results. The Impact Hammer test method described here, uses a list of functions developed as a MATLAB toolbox, and is part of the SERIES project.JRC.G.5-European laboratory for structural assessmen