Analytical and Numerical Investigation of Detachable Short Links with Flush and Extended-End Plate Connections

Abstract

Along with the increasing utilization of steel in -capacity design of structures, an eccentrically braced frame (EBF) is one of the structural typologies introduced with links acting in bending and/or shear to resist horizontal forces. With efficiency considerations in post-seismic repair of structures, detachable seismic links have also been introduced. With these devices, only the links need to be replaced while the other members continue to be structurally appropriate to function. Studies have shown that there is significant development of axial force in links, but they are not considered in established design procedures. Considering this gap, this parametric study aims to achieve a more thorough grasp of shear overstrength and axial force as influenced by different parameters such as length ratio, strength of connection, stiffness, and boundary conditions. Twenty-five flush-end plate (FEP) and 15 extended-end plate (EEP) connections for short links are designed using the component method until Method 1 of link verifications are satisfied. The same configurations are also verified according to Methods 2 and 3. Numerical analyses are performed on the 40 models using FE software Abaqus 6.14 considering two boundary conditions: with fully rigid restraints and with deformable springs. From the analytical perspective, FEP connections have design limitations and cannot be used for all length ratios of HEB profiles, nor for 0.75es and es of HEA profiles. On the other hand, EEP connections have a wider range of application. For all analyses of assemblies performed, the values of shear overstrength at 0.08 rad link rotation are consistently close to 1.5 (1.4 to 1.66). The shear overstrength is also observed to decrease along with the increase of profile depth and/or length ratio. Moreover, wide-flange profiles have higher shear overstrength than narrow-flange profiles. In terms of axial force, there are also several parameters that affect the behaviour of its development. The imposed boundary conditions that represent the stiffness of the frame has significant effect on the level of axial forces, with higher forces for fully rigid BC and lower values for deformable springs. Short length ratio, low strength of connection, and high stiffness have been observed to affect the level catenary action in links, resulting to large compressive arches and lower tensile force (if the tension zone is reached). Lastly, tensile forces are found to be more detrimental than compressive forces in terms of bending resistance of the link-connection assembly.

Along with the increasing utilization of steel in -capacity design of structures, an eccentrically braced frame (EBF) is one of the structural typologies introduced with links acting in bending and/or shear to resist horizontal forces. With efficiency considerations in post-seismic repair of structures, detachable seismic links have also been introduced. With these devices, only the links need to be replaced while the other members continue to be structurally appropriate to function. Studies have shown that there is significant development of axial force in links, but they are not considered in established design procedures. Considering this gap, this parametric study aims to achieve a more thorough grasp of shear overstrength and axial force as influenced by different parameters such as length ratio, strength of connection, stiffness, and boundary conditions. Twenty-five flush-end plate (FEP) and 15 extended-end plate (EEP) connections for short links are designed using the component method until Method 1 of link verifications are satisfied. The same configurations are also verified according to Methods 2 and 3. Numerical analyses are performed on the 40 models using FE software Abaqus 6.14 considering two boundary conditions: with fully rigid restraints and with deformable springs. From the analytical perspective, FEP connections have design limitations and cannot be used for all length ratios of HEB profiles, nor for 0.75es and es of HEA profiles. On the other hand, EEP connections have a wider range of application. For all analyses of assemblies performed, the values of shear overstrength at 0.08 rad link rotation are consistently close to 1.5 (1.4 to 1.66). The shear overstrength is also observed to decrease along with the increase of profile depth and/or length ratio. Moreover, wide-flange profiles have higher shear overstrength than narrow-flange profiles. In terms of axial force, there are also several parameters that affect the behaviour of its development. The imposed boundary conditions that represent the stiffness of the frame has significant effect on the level of axial forces, with higher forces for fully rigid BC and lower values for deformable springs. Short length ratio, low strength of connection, and high stiffness have been observed to affect the level catenary action in links, resulting to large compressive arches and lower tensile force (if the tension zone is reached). Lastly, tensile forces are found to be more detrimental than compressive forces in terms of bending resistance of the link-connection assembly.