DAD Post-Tensioned Concrete Connections with Lead Dampers: Analytical Models and Experimental Validation

J. B. Mander

Department of Civil Engineering, Texas A&M University, College Station, TX, USA

Kevin M Solberg and Rajesh P Dhakal

Department of Civil Engineering, University of Canterbury, New Zealand

J. Geoffrey Chase and Geoffrey W. Rodgers

Department of Mechanical Engineering, University of Canterbury, New Zealand

Jointed precast concrete systems typically have low inherent damping and are thus well suited for the use of supplemental damping systems. This work examines the analytical modeling and experimental validation of full-scale beam-column connections constructed utilising Damage Avoidance Design (DAD) principles with un-bonded post-tensioned tendons and rocking interfaces. These test articles also utilise high force-to-volume extrusion-based energy dissipaters to provide supplemental energy dissipation and modify joint hysteretic performance. Independently validated analytical models of both the joint and devices are combined to create a full system model. In particular, analytical modelling is utilised to characterise the damper augmented beam-to-column rocking connections, using a rate-dependent tri-linear compound version of the well-known Menegotto-Pinto rule. The analytical model is verified against a number of experimental results over inter-story drifts of 1-4%. The relative contributions to the overall force-displacement behaviour of the structural, post-tensioning and damper elements are also delineated, indicating the significant role of the damping devices in mitigating structural response energy. Overall, the precast system behaviour is improved by the addition of the extrusion based damping system, showing increases in hysteretic energy dissipation of up to 300% while maintaining static re-centring capability.

Jointed precast concrete systems conforming to Damage Avoidance Design (DAD) typically have low inherent damping. They are thus well suited for supplemental damping systems. Recently, considerable attention has focused on yielding steel fuse-bars to provide hysteretic energy dissipation and modify overall joint hysteresis (Li, 2006; Solberg 2007). Concomitantly, research into extrusion-based damping devices has resulted in the development of high force-to-volume lead extrusion dampers (Rodgers et al 2006a,b). These dampers provide equivalent or higher forces than yielding steel fuses, and do so on every response cycle. They are also sufficiently compact to allow placement directly into structural connections.

This research outlines the experimental testing and analytical modelling of a prototype jointed precast beam-to-column sub-assemblage detailed according to the Damage Avoidance Design (DAD) philosophy. To supplement the damping, the specimen was fitted with high force-to-volume lead extrusion dampers. The primary focus is the effect of these dampers on the overall joint hysteresis. Analytical modelling of the experimental results utilises a compound rate-dependent version of the Menegotto-Pinto rule. The resulting experimentally validated model will enable easy consistent implementation design, when used in conjunction with spectral analysis-based design guidelines (Rodgers et al 2007).

References

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