A steel bridge was subjected to loads which are over its capacity load. Strengthening works were done to allow passing of the required load. To ensure that the strengthened works gained enough increase in flexure stiffness, a dynamic test using controlled traffic technique was performed. The bridge dynamic characteristics before and after strengthening work and just after passing of load were determined. Experimental studies were carried out on two spans for a multiple simple spans bridge using a certain vehicle passing over the bridge. The bridge acceleration response was measured and the bridge fundamental frequency was determined for each span before and after strengthening and after passing of load. The results were used to evaluate the bridge flexure stiffness.