Experimental Analysis of Dynamic Amplification Factor Under Traffic Load

Eden od parametrov, ki igra pomembno vlogo pri oceni prometne varnosti obstoječih premostitvenih objektov, je koeficient sunka.Kljub številnim raziskavam na tem področju še vedno prihaja do razhajanj, ali so za oceno varnosti obstoječih premostitvenih objektov bolj primerni koeficienti sunka, izračunani iz deformacij, ali iz pomikov. In do razhajanj, kateri izmed njih so večji. V magistrski nalogi je analiziran obstoječi armiranobetonski cestni most z obojestranskim previsom brez dilatacij, ki s ploščasto prekladno konstrukcijo premošča razpetino 10 metrov. Na mostu je bilo tekom meritev nameščenih skupno 24 merilnikov deformacij, pomikov in pospeškov, s katerimi je bil merjen odziv mostu pri prečkanju kalibracijskega vozila med popolno prometno zaporo. Z namenom simulacije neravnine na vozišču mostu je pri nekaj vožnjah kalibracijsko vozilo pred oziroma nad mostom prevozilo oviro. Povzete so ugotovitve nekaterih prejšnjih študij, ki so se ukvarjale z določitvijo koeficienta sunka, predstavljen pa je tudi postopek za določitev koeficienta sunka, ki je bil uporabljen v tem delu. Prikazani so tipični signali iz različnih merilnikov, kjer je opisan postopek odstranitve začetnega odmika in glajenja signalov. Za vse signale iz merilnikov deformacij in pomikov so prikazane največje izmerjene vrednosti in pripadajoči koeficienti sunka v odvisnosti od pozicije senzorja in v odvisnosti od hitrosti kalibracijskega vozila. Primerjava izračunanih koeficientov sunka iz deformacij in pomikov je opravljena z izračunom koeficienta korelacije r z namenom ugotovitve, pri kateri kombinaciji hitrosti kalibracijskega vozila so koeficienti najbolj povezani. Meritve iz merilnikov pospeškov so bile uporabljene za izračun pomikov. Maksimalne vrednosti izračunanih pomikov so bile primerjane z izmerjenimi pomiki. Za ugotovitev, pri katerih hitrostih kalibracijskega vozila je izbrana metoda za izračun pomikov iz meritev pospeškov najnatančnejša, je bila povezanost izračunanih in izmerjenih pomikov določena za različne kombinacije hitrosti kalibracijskega vozila.One of the parameters that plays an important role in assessment of existing bridges is the dynamic amplification factor (DAF). Although many studies have already been performed in this field, it is still unclear if DAFs, calculated from displacements, are larger than those, calculated from deflections and which one of the two are more appropriate for assessment of existing bridges. An existing simple highway road concrete slab bridge with double-sided overhang without dilatation, that bridges a span of 10 meters, was analysed in this thesis. During measurements, 24 strain, deflection and acceleration sensors were installed, the purpose of which was to determine the bridge behaviour during several passages of a calibration vehicle. In order to simulate surface unevenness, some of the passages included having a vehicle drive over a bump that was positioned in front of the bridge or on the bridge. Findings from selected previous studies that dealt with determination of the DAF are summarised and the procedure, used for determining the dynamic amplification factor in this thesis is presented. Typical signals from different sensors are shown, where the process of initial shift elimination and signal smoothing is described. Maximum measured values together with their corresponding calculated DAFs are presented depending on the speed of calibrated vehicle and sensor position. Comparison between DAFs, calculated using strains and deflections, is performed with calculation of the correlation coefficient r in order to identify at which speeds the most significant relationship/connection of the calculated DAF from strains and displacement is observed. Measurements from acceleration sensors were used to calculate deflections. Maximum values of the calculated deflections were compared with the values, obtained from deflection sensors. In order to find out at which speeds of calibrated vehicle the method used for deflection calculation is the most accurate, the relationship strength between calculated and measured values was calculated for different speed combinations of the calibration vehicle