Geotechnical investigation of 33 pole bridge structure in Isfahan using Ground- Penetrating Radar method

2-D finite-difference algorithm is used to simulate the GPR responses of synthetic models resembling common geotechnical targets including layered earth (slab), horizontal cylinders and 2-D prisms. Through using a 500 MHz GPR system equipped with shielded antennas, 46 profiles comprising 36 transverse profiles in the east-west direction perpendicular to the main bridge axis, 7 longitudinal profiles in the north-south direction along the main bridge axis and 3 transverse profiles from the bases of the bridge were surveyed. Processing and interpretation of longitudinal and transverse radargrams revealed various in-homogeneities including reinforcing joists and rebars, blocks of stone and wooden timbers as well as ruptures and subsidences in several locations. Concrete slabs reinforced with joists and rebars, are mainly associated with recent repairs of the bridge while reinforced sections by stone blocks and wooden timbers are related to the ancient construction works which have suffered several fractures and subsidences.