Spring 2004

Dynamic Analysis and Experimental Verification of Bridge Vibration

Md. Sorowar-E-Morshed

 The main objective of this work is to study the dynamic behavior of two- and three-dimensional bridges under moving vehicular loads. The two-dimensional straight bridges are studied both by numerical analysis and experimental verification, while the three-dimensional curved bridges are only studied numerically.

A bridge model is developed at the Structural Mechanics and Strength of Materials laboratory of UAP. The experimental works use an aluminum bridge deck about 10-ft long. A laboratory arrangement consisting of vehicular loading with different wheels, superimposed load and vehicular velocity and a computerized data acquisition system are also developed for this study. The data collected for simply supported and three-span continuous bridge includes the deflection at particular reference points. The experimental and numerical results show reasonable agreement, with the experimental values being within 0.60 to 1.33 times the numerical values. But the vehicular velocities generated in the laboratory are found to be inadequate to cause significant dynamic effect on the bridges, and the deflections obtained for various velocities are not significantly different.      

The work on three-dimensional RCC bridges concentrates on numerical studies to investigate some important deflection and force parameters for two-span straight bridge, arch bridges, horizontally curved bridge and three-dimensional curved bridge. The HS20 loading is used for the dynamic analyses, which are performed for vehicular velocities of 44 ft/sec and 88 ft/sec.

The impact factors obtained from this study are within the limits specified by AASHTO for the absolute maximum deflections and forces but far exceed the AASHTO specified values for maxima in the reverse directions. This can be crucial for the structural design of the bridges made of RCC in particular, whose behavior under tension and compression are entirely different.