The study is concerned with the experimental and numerical investigations of brace configurations on steel buildings in terms of dynamic characteristics. A three-storey steel building model with 1/2 scale of a real building, which was constructed at the laboratory of Civil Engineering Department of Karadeniz Technical University, was selected for investigations. A series of ambient vibration tests were conducted on the building model for bare frame and braced cases. Four different brace types were applied to the model: cross type, Lambda type, V type and K type. The natural frequencies and their associated mode shapes and modal damping ratios were identified for each different case in the frequency domain by the Frequency Domain Decomposition method. Also, finite element models for these cases were developed to simulate dynamic behavior. The effect of brace configurations was evaluated by comparing the braced dynamic characteristics with those of the bare case. Also, the experimental and numerical dynamic characteristics were compared with each other, the differences between results were revealed by considering experimental results as exact. The study showed that the stiffness of steel buildings can be increased by applying brace elements considerably and the effects of braces vary depending on brace configuration. The cross type bracing produced the highest stiffness both experimentally and numerically. From the finite element analysis, it was observed that the numerical results were bigger than the experimental results in all cases; therefore the initial finite element models need to be updated. (c) 2010 Elsevier Ltd. All rights reserved.