Abstract:
A key element of an effective asset management system for bridges
is the ability to undertake cost-effective load assessment and
evaluation of the current state of bridges and to be able to understand
the causes and quantify the rate of their deterioration. Whilst proofload
testing and health monitoring procedures provide valuable tools,
such procedures are generally too complex and too costly to be applied
across the entire inventory of short span timber bridges. Such testing
is costly to conduct, requires equipment and expertise not readily
available to many local government bodies and has significant inherent
uncertainties in regard to the assumed relationship between stiffness
and strength of timber girders.
This paper describes procedures that have been specifically developed to address the need for relatively inexpensive load assessment,
costing less than 25% of the expenditure required for static load tests,
(and no more than 1%-5% of the replacement cost of the asset) that
will provide reliable, quantitative information on the performance of
short and medium span bridges. These procedures contain two
significant innovations - the first is accurate determination of the global
deck stiffness of a timber deck using dynamic frequency analysis; the
second is prediction of load capacity of a bridge deck, using a
probabilistic relationship between bending strength and gross stiffness
(EI) of timber girders.
