NUMERICAL ANALYSIS AND EXPERIMENTAL CORRELATION OF UNCOUPLED CONCRETE WALLS INCORPORATING SLB DEVICES

Pantoja M.; Flores M.; Bozzo L.; Gonzales H. · World Conference on Earthquake Engineering proceedings (2021)

Resumen

ACI 318-19 Code has substantially modified their ductility requirements for walls, resulting in an increment of cost and detailing. A different approach is to combine a bare reinforced concrete frame filled with concrete walls only connected to the frame at their base and their upper level by ductile connections such as SLBs. Since these devices do not transfer axial load, the solution is called “uncoupled” concrete walls. The combination of reinforced concrete frames and uncoupled walls with dissipators increases stiffness and ductility, but most importantly, allows the walls not to be aligned vertically, even in its full height, resulting in important architectural advantages. This work presents a comparison between an experimental and a numerical model of uncoupled reinforced concrete walls using Shear Link Bozzo (SLB) connections for a cyclic loading test performed at the UNAM laboratory in Mexico. In order to understand the structural behavior of the SLB connections, three 1:1-scale tests were performed: (1) a bare reinforced concrete frame, (2) a reinforced concrete frame with 50kN SLB devices (Type 1) on uncoupled walls and (3) a reinforced concrete frame with 100kN SLB devices (Type 2) in the same uncoupled walls. These test results are used to validate numerical simulations of the system through Finite Element Analysis software; in this case, ABAQUS CAE. Once validated, the main parameters of the SLB connections are varied to understand how these affect the general behavior of the system. The purpose is to analyze the influence of the different parameters in the behavior of the SLB connections to propose alternatives to improve their performance. For the bare reinforced concrete frame, the experimental force-displacement curve was quasi linear up to 14mm. For a similar level of lateral displacements incorporating SLB energy dissipators, a significantly stable nonlinear response with an initial yielding displacement of only 2mm was shown. After 14mm lateral displacement in test 2 and 3, type 1 and type 2 dissipators, reached lateral loads of 235kN and 320kN respectively. A significant measurement is that the hysteretic energy dissipation by types 1 and 2 devices was from 6 to 10 times greater than that of the bare reinforced concrete frame. Analytical results showed that reducing the total height of the devices may contribute to dissipating more energy, despite failure displacement being proportionally reduced. This means that a compact device could display a better performance using less material, which translates as a cheaper device, although it may not be feasible due to practical minimum lateral displacements requirements in codes. A model using horizontally fixed supports was implemented showing that it improves the behavior of the SLB connections, reaching up to 140% of the total load capacity of the system. Moreover, higher Von Mises stress distribution is displayed in the SLB connections, reaching high plastic deformations. However, the aforementioned theoretical improvements lost the “no vertical load transfer advantage” which is considered important for practical purposes. © The 17th World Conference on Earthquake Engineering.