Reforzamiento de nudos exteriores viga-columna de estructuras de concreto armado mediante aleación con memoria de forma

Abstract

This project develops a seismic retrofit methodology for exterior beam–column joints in reinforced-concrete frames using Fe-SMA, aimed at increasing strength, ductility, and the system’s strength hierarchy. The hypothesis states that a thermally activated Fe-SMA strengthening to induce prestress increases joint shear strength and rotational capacity, mitigating brittle mechanisms. It is justified by the vulnerability of deficient joints in existing buildings and by the lack of standardized modeling and design procedures. A typical joint and a three-story frame with nine joints were modeled in SeismoStruct, considering material nonlinearity. The joints were represented with bilinear moment–rotation links and were evaluated through pushover analysis per ASCE/SEI 41-17, applying gravity loads and incremental lateral loads at master nodes with a rigid diaphragm. The strengthening was defined with Near Surface Mounted Fe-SMA bars, anchorage grout, and thermal activation; for Fe-17Mn-5Si-10Cr-4Ni-1(V,C), a recovery stress σ_prestress=350 MPa with 2% prestraining was adopted. Joint capacity increased from 8.3 to 51.0 kN·m. In the frame, peak base shear rose from 52.24 to 85.82 kN (≈64%) and shear failure in first-story columns was delayed relative to yielding. In conclusion, the methodology enables sizing and verification of Fe-SMA strengthening for exterior joints and shows how local improvements translate into global gains in capacity and ductility, leaving a basis for experimental validation. Keywords: Fe-SMA, beam–column joint, three-story frame, pushover analysis, seismic retrofit.