Experimental study on compressive behavior of intermediate slender timber columns with local damage and the retrofitting techniques for the damaged columns

The existing historic timber constructions are often affected by local damage such as decay, and their mechanical properties are significantly reduced. In order to explore the influence of local decay on the compression behavior of timber columns, this work conducted experimental investigations of 10 intermediate slender columns with different damaged conditions under axial compression. Damaged areas, damaged positions and damaged forms of the columns were considered. Based on the failure mechanism of damaged timber columns, the retrofitting technique for locally damaged columns using the combination of wood block, profile and carbon fiber reinforced polymer (CFRP) wrap was proposed, compared with the traditional methods of using wood block only, and both wood block and CFRP wrap. Experimental investigations of 10 retrofitted columns with 4 retrofitting techniques were also conducted. The compressive performances and effect among these retrofitting techniques had been compared based on the failure modes and ultimate load-carrying capacity stiffness and ductility. The results indicated that the compressive performance of the damaged columns was significantly reduced which magnified with the increase of damaged area, and the loss of the load-carrying capacity was much larger than the loss of the cross-section area. The load-carrying capacity and stiffness of the damaged columns were appreciably restored by these retrofitting techniques. The load-carrying capacity of the bilaterally damaged column retrofitted by the combination of wood block, GFRP profile and CFRP wrap was the highest, reaching 98.30% of the intact column.