DYNAMIC BEHAVIOR AND VIBRATION ASSESSMENT OF A MULTISECTOR INTEGRAL BRIDGE: INSIGHTS FROM TRAFFIC AND PEDESTRIAN FIELD TESTS
Mahendra Kumar H M,
G P Chandradhar,
Goud Mallesh,
Vinayak Naik
Abstract: Integral bridges eliminate expansion joints and bearings, which improves durability but produces complex dynamic behavior that must be verified under real operating conditions. This study combines field testing with three-dimensional finite element (FE) modelling in MIDAS Civil to characterize five integral bridges with one to five spans, clear spans of 5 to 18 m, and solid or voided slab decks. Tests were carried out under ambient traffic and synchronized human jumping by 3, 6 and 9 participants. Natural frequencies were identified by Fast Fourier Transform, damping ratios by the logarithmic decrement method, and dynamic amplification factors (DAF) from double-integrated acceleration records. At the single-span Patnem Bridge, the measured fundamental frequency of 10.09 Hz agreed with the FE value of 10.17 Hz (0.8% difference). Its damping ratio was 8.16% and its DAF was 1.21, below the IRC (1.225) and BD 37/01 (1.322) values. Jumping by nine people produced a near-resonant response at 10.50 Hz, within 4% of the traffic-derived frequency. Across all bridges, measured frequencies ranged from 9.67 to 26.2 Hz, damping ratios from 4.59% to 8.16%, and DAF from 0.97 to 1.69. Equivalent stiffness ranged from 5.63 to 65.75 MN/m and agreed within 5–9% with the classical EI/L³ relationship, generally decreasing with span length. The exception was the four-span, 18 m Thippegondanahalli Bridge (32.55 MN/m), where continuity, integral abutments and a voided haunched deck raised the stiffness. This bridge also showed the highest DAF (1.69), exceeding both code values. For the multi-span bridges, FE frequencies differed from the measured values by 13 to 30% and FE DAF by 0.04 to 0.25. These results show that bridge-specific testing and experimentally calibrated FE models are needed for reliable vibration serviceability assessment of integral bridges.
Keywords: Integral bridges, Vibration serviceability, Natural frequency, Damping ratio, Dynamic amplification factor, Human structure interaction, Ambient traffic excitation, Finite element modelling
DOI: 10.24874/PES08.03B.019
Recieved: 20.07.2026 Revised: 22.08.2026 Accepted: 04.09.2026
UDC:
Reads: 15 
