Flexural behavior of stone beams reinforced with prestressed NSM CFRP bars

This paper is devoted to experimentally evaluate the efficiency of prestressed near surface mounted (NSM) carbon fiber reinforced polymer (CFRP) bars for reinforcing stone beams to improve their flexural performance. A total of nine stone beams, classified into three test sets (Set A, Set B, and Set C) according to the beam span and the cross-sectional dimensions, were reinforced with prestressed NSM CFRP bars and tested under monotonic loading. In each test set, one bare stone beam was also tested for comparison. In Set C, the reinforced stone beams were strengthened with CFRP-strip wrapping in the shear span to increase the shear capacity. The test parameters included the amount of NSM CFRP reinforcements and the prestressing force. It was found from the test results that the use of prestressed NSM CFRP bars shifted the failure of stone beams from abrupt fracture to a more ductile mode and the load capacity was significantly increased. Failure of the reinforced stone beams in Set A and Set B occurred either by slip of the CFRP reinforcement or CFRP debonding or flexural-shear failure. The reinforced stone beams with CFRP-strip wrapping in Set C failed in the flexural-shear mode accompanied by rupture of the CFRP strips. The load-deflection responses of the reinforced stone beams exhibited a three-stage behavior which was similar to that of the reinforced concrete (RC) beams. The CFRP-strip wrapping effectively enhanced the shear capacity of the reinforced stone beams and avoided the abrupt failure when the first crack occurred in the shear span. For the stone beams reinforced with a same amount of NSM CFRP reinforcements, the increase in the prestressing force resulted in an increase in the load capacity accompanied by a reduction in the deformation capacity when the failure was governed by CFRP debonding.