Dynamic testing of a truss bridge using a vibroseis truck

Abstract

Dynamic characterization of a bridge structures can often provide a more reliable and quantitative description of its performance and condition than possible from conventional bridge inspection and rating procedures. Such characterizations are typically accomplished at the global level using either controlled or ambient vibration testing methods. Ambient vibration testing is by far the more commonly employed approach for bridges due to numerous practical and logistical advantages it has over controlled dynamic testing methods. However, ambient vibration testing relies on a number of assumptions and can be subject to limitations that may not be readily apparent in the absence of an alternative characterization result. The writers recently conducted a dynamic characterization program on an in-service truss bridge and utilized both controlled and ambient vibration test methods. The structure that was evaluated is a three-span, Parker pony truss bridge that was constructed in 1930. The forced-vibration testing was performed using a vibroseis truck. The controlled vibration tests included both burst random and sine-sweep excitations at several locations in each span. This paper describes the results of the controlled vibration tests. The results are also compared with results from ambient vibration testing of the bridge. The advantages and limitations of each characterization method are discussed. © The Society for Experimental Mechanics, Inc. 2012.