Unlike the most of conventional model-based damage detection methods using the discrepancy between the FE model response and field-tested dynamic response as evaluation criteria,the new approach is formulated to search for the damage element by minimizing the discrepancy between the model responses difference and field-tested dynamic response difference under healthy and damaged conditions.Using the discrepancy between the modeled difference and the field measured difference as evaluation criteria facilitates the elimination of the uncertainty that may exist in or be caused by the FE model or the dynamic testing system.In order to be effective,the method is further formulated to search for a given maximum number as K of possible damage elements among all the elements N,where K << N.Therefore,the new formulation dramatically reduces the dimension of the problem and enables the effective and efficient damage detection for the large civil structure systems.The novel approach was applied to the damage detection of the I-40 Bridge.