Sliding Keys on Inclined Deflecting-cantilevers (SKID) device for application with Post-Tensioned (PT) frames

Abstract

This thesis presents a novel frictional damping device for application with Post-Tensioned (PT) frames. A conceptual system named a Frictional Sliding on a Sprung Slope (FSSS) system is proposed first. Its mechanical schematisation is presented, and the theoretical hysteretic behaviour is discussed. The FSSS system has a triangular-shaped hysteretic curve with an amplitude-increasing resistance and a zero-activation threshold. Then, an innovative physical realisation of the conceptual FSSS system is presented and named a Sliding Keys on Inclined Deflecting-cantilevers (SKID) device. The device uses the end stiffness of cantilever bars as the “sprung-slope” for generating an amplitude-dependent normal force. The reliability of using cantilever bars is discussed. (Chapter 3)

To demonstrate the SKID device, two 1/4 scale-reduced prototypes are designed and manufactured. They have negative unloading stiffness (SKID A) and positive unloading stiffness (SKID B), respectively. By conducting quasi-static cyclic tests, it is found that they exhibited stable and repeatable triangular-shaped hysteretic curves, verifying a satisfactory consistency between the theoretical behaviour and the test results. In addition, SKID configurations having different manufacturing parameters (i.e., friction materials, cantilever bar stiffness and slope angle) are built and tested by both cyclic and fatigue tests to investigate the behaviour sensitivity. (Chapter 4)

Chapter 5 presents the application of the SKID device in PT frames (the PT-SKID frames). The theoretical hysteretic performance of the PT-SKID frame is discussed by deriving its analytical formulations. The PT-SKID frame has a dual-triangular-flag-shaped hysteretic curve, featuring a full self-centring capability. Then, three PT frames with and without the SKID device are analysed numerically using OpenSees as a numerical proof-of-concept. Incremental dynamic analyses (IDA) are carried out to explore the contribution of the SKID device. The results show that the device significantly reduces the seismic response of the PT frame and no residual deformations are observed after the earthquake excitations. Additionally, more than 700 one-story one-bay PT frames with different SKID devices (PT-SKID frames) are numerically tested to investigate the dynamic characteristics of the structural system affecting the seismic response.

Chapter 6 investigates the linear equivalence of the PT-SKID frames for estimating peak seismic displacement response. The linear equivalent system is constructed by its secant stiffness and the equivalent damping ratio estimated by Jacobsen’s method. Such linearisation is the basis of Direct Displacement-Based Design (DDBD). Then, the accuracy of the linearisation to assess the peak seismic displacement response is evaluated by numerically testing 5,880 mid- to long-period PT-SKID frames. The results show that the linear equivalence frequently underestimated the peak displacement response, leading to an unconservative design in the DDBD. To eliminate the influence of this error, a correction factor is suggested for the design spectrum used in the DDBD of the PT-SKID frames.

Chapter 7 proposes a novel Post-Tensioned Precast Warehouse structure with the Sliding Keys on Inclined Deflecting-cantilevers Device (the PTPW-SKID Structure) following the concept of the PT-SKID frame for industrial buildings. The structure comprises a PT outer frame and a SKID inner frame. The PT outer frame supports the roof and cladding systems; and the SKID inner frame supports the SKID devices and crane system. The design and seismic performance of the PTPW-SKID structure are presented by a case frame located in L'Aquila, Italy. The Direct Displacement-Based Design (DDBD) method is utilised for the seismic design. A 3D numerical model is built in OpenSees. Both quasi-static and seismic dynamic analyses are carried out to investigate its hysteretic behaviour and the seismic response.

Date of Award	5 Dec 2023
Original language	English
Awarding Institution	University of Bristol
Supervisor	Nicholas A Alexander (Supervisor) & Raffaele De Risi (Supervisor)