Design Procedure for the FRCC Strengthening of Beam-Column Joints

Abstract

AbstractExisting reinforced concrete buildings were mainly designed with old code provisions. This resulted in lack of proper seismic details and, in turn, the occurrence of premature brittle failures as frequently observed in the aftermath of recent seismic events. The shear failure of the joint panel is one of the main reason limiting the seismic performance of existing structural systems. Several retrofit solutions were proposed in the recent years to improve the joint panel shear strengthening and, nowadays, composite materials are frequently used in the common design practice. The widespread use of fibre-reinforced cement composites (FRCC) and high-performance fibre-reinforced cementitious composites (HPFRCC) opened new frontiers in the design of the shear capacity of RC members. The high tensile strength, toughness, and tolerance for damage make these materials attractive for the use in earthquake-resistant structures, with emphasis on RC members with shear-dominated response. Although several experimental tests demonstrated the effectives of these materials in the seismic retrofit of existing beam-column joint a proper design formulation is still lacking.This research paper presents a novel procedure for the design of the exterior FRCC jacketing of poorly detailed on beam-column joints. A mechanical model based on the principal tensile stress approach is proposed. The model is later validated against a comprehensive database of experimental tests at global and local level. The proposed procedure allows the designers to calculate the thickness of the FRCC jacketing to avoid the joint panel shear failure and promoting a more ductile failure mode.KeywordsFRCUHPFRCFibre reinforced concreteSeismic retrofitBeam-column joints