ABSTRACT
ABSTRACT: A specific static bridge test provides a direct, or individual, benefit for that structure itself; such a benefit is called 'individual' in the paper because it usually cannot be related to other structures. The term 'indirect benefit' or 'collective benefit' is used herein for the benefit identified by tests on one or few bridges, but which is available for the other structures as well. A re-assessment of the impact factor, or the dynamic load allowance (DLA), with the help of dynamic testing can provide indirect benefit for the evaluation of all existing bridges. It is demonstrated that the DLA, not given to direct measurement, is an interpreted entity, drops with increase in the vehicle weight. Since the values ofDLA are always determined under vehicles carrying no more than the legally-permissible loads, a question is raised in the paper about the validity of these values for the much heavier design and evaluation loads corresponding to the ultimate limit state (ULS). It is recognized that the dynamic magnification of load effects above their static values takes place at an 'intermediate' strain rate, under which the strengths of most materials are at least 25% higher than the strengths determined at 'low' strain rates, or in 'static' tests. It is recommended that for the ULS evaluation by the Canadian Highway Bridge Design Code, the DLA should be reduced by at least 50%.
