Towards error‐free hybrid simulation using mixed variables

Abstract

Two procedures are developed and implemented in a hybrid simulation system (HSS) with the aim of enhancing the accuracy and reliability of the online, i.e. pseudo-dynamic, test results. The first procedure aims at correcting the experimental systematic error in executing the displacement command signal. The error is calculated as the difference between command and feedback signals and correlated to the actuator velocity using the least-squares method. A feed-forward error compensation scheme is devised leading to a more accurate execution of the test. The second procedure employs mixed variables with mode switching between displacement and force controls. The newly derived force control algorithm is evaluated using a parametric study to assess its stability and accuracy. The implementation of the mixed variables procedure is designed to adopt force control for high stiffness states of the structural response and displacement control otherwise, where the resolution of the involved instruments may favour this type of mixed control. A simple pseudo-dynamic experiment of steel cantilever members is used to validate the HSS. Moreover, two experiments as application examples for the two developed procedures are presented. The two experiments focus on the seismic response of (a) timber shear walls and (b) reinforced concrete frames with and without unreinforced masonry infill wall.

Hybrid Simulation Theory for Continuous Beams

“…The error in the rotation, shear force, and bending moment can also be studied with the use of Sobolev-seminorms on the displacement field (Johnson 2009). Understanding the error in these quantities is as important as understanding the error in the displacement because in some situations these quantities can be of equal or even greater importance to the structural and mechanical behavior of a system than the displacement (Elkhoraibi and Mosalam 2007).…”

Seismic evaluation of 1940s asymmetric wood‐frame building using conventional measurements and high‐definition laser scanning

“…application of level 5 in runs 16 and 17 of phase II. These values are approximately 5% (used in the hybrid simulation [2]) before severe shaking and 2% after severe shaking. This reduction in the damping ratio is attributed to less energy dissipative mechanisms after the building has experienced significant damage (due to loosening of connections caused by crushing of wood around fasteners) with increased tendency to twist (discussed later) after the application of level 5 in phase II.…”

“…only 4.25%, suggesting a concentration of damage in the first story of the test building. Therefore, the hybrid simulation study of the longitudinal walls in [2] focused on the first story walls only. The slight increase of the secant stiffness, in terms of peak-to-peak story shear, from run 33 to run 37 is attributed to the pinching, Figure 13, caused by nails pull out of the ship-lap siding from the studs.…”

Hybrid simulation theory for a classical nonlinear dynamical system

“…The entire exercise is easily repeatable with alternate control methodologies; see e.g. [23,11]. The controller that one should employ in an actual experiment is based on the experimental setup that is used and one that minimizes errors that are important to problem at hand (amongst those metrics that we highlight in the paper and perhaps others of physical significance to the researcher).…”