Continuous Reinforced Concrete Beams with Various Carbon Fiber-Reinforced Polymer Systems under Soil Settlement

This paper presents the behavior of two-span continuous reinforced concrete beams strengthened with carbon-fiber reinforced polymer (CFRP) composites subjected to differential settlement. Two types of strengthening schemes are employed (externally bonded [EB] sheets and near-surface-mounted [NSM] strips), and the beams are loaded under monotonic and cyclic conditions. To preclude the premature bond failure of EB CFRP, U-wrap anchors are adhered to both ends of the sheets.

Ancillary tests are conducted to study the grain distribution and settlement response of supporting soils. When soil movement takes place, the beam stiffness (flexural) of the settled span is reduced and the applied load is redistributed to the other span with rigid supports. The loading and unloading responses of the EB beam are more influenced by the differential settlement compared with those of the NSM beam, which exhibits insignificant residual displacement

. While both EB and NSM strengthening methods are effective in alleviating the negative moment of the continuous beams, the integrity of the strengthening systems is degraded as the soil settlement and cyclic loading are simultaneously engaged, including the progressive slip of the EB sheet and the end-debonding of the NSM strip. The degree of force transfer from the loading points to the soils controls the extent of support-settlement. The negative moment of the beams caused by settlement is quantified, and the role of end-anchorage is emphasized. From a practical perspective, the performance of the strengthened beams is appraised against design limits concerning angular distortion.

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