IMPACT FACTORS FOR SIMPLE-SPAN HIGHWAY GIRDER BRIDGES

Vibrational behavior of simple-span highway girder bridges with rough surfaces due to heavy trucks is discussed. The causes of vibration and dynamic characteristics of bridge structures are investigated in the time and frequency domains. An appropriate vehicle model for vibrational analysis of bridges is found by comparing dynamic responses from four different vehicle models, and impact factors are calculated using the suggested vehicle model with different speeds, deck roughnesses, and span lengths. The results are compared with the values specified by several standard codes, and it is found that the current design codes tend to underestimate impact factors especially in long-span bridges with rough decks. Finally, empirical formulas for impact factors represented in terms of span length, vehicle speed, and surface roughness of a bridge deck are suggested from the multiple linear regressional using the data obtained from this study.