Design and seismic response suppression performance of an adaptive damping system for prefabricated structures based on PID closed-loop control

Prefabricated concrete frame structures exhibit inherently low damping ratios and are susceptible to joint stiffness degradation under seismic loading, both of which limit the effectiveness of conventional passive and model-dependent semi-active control strategies. This study presents an adaptive damping system based on a solenoid-valve-controlled hydraulic damper, governed by a piecewise gain-scheduled PID closed-loop control strategy specifically designed for the low-damping and frequency-drift characteristics of prefabricated frames. The novelty lies in tailoring a model-free, output-feedback PID controller with drift-triggered three-stage gain scheduling to the joint-degradation behavior of precast frames, so that no online structural model or state estimation is required and a fail-safe passive fallback is retained on power or sensor loss. An eight-story numerical model incorporating semi-rigid beam-column joints with Modified Ibarra-Medina-Krawinkler hysteretic behavior is established in OpenSees, and the proposed system is evaluated against passive optimal damping and classical clipped-optimal semi-active control under 14 ground motion records at three intensity levels. Under the design-basis earthquake, the PID system achieves mean peak displacement, acceleration, and base shear reductions of 26.8%, 22.1%, and 20.8%, respectively, with a damper energy dissipation ratio of 46%. Robustness analyses demonstrate that under ±20% joint stiffness perturbation, the performance fluctuation of the PID system is approximately 40% to 43% of that of the clipped-optimal scheme. The results confirm that the proposed strategy matches the suppression performance of clipped-optimal control while roughly halving its performance sensitivity to joint-stiffness uncertainty, and does so without any structural model, state observer, or optimization at run time—demonstrating a practical, robust, and low-complexity route to semi-active seismic protection of prefabricated frames.