Abstract
Geotechnical centrifuge models necessarily involve simplifications compared to the full-scale scenario under investigation. In particular, structural systems (e.g. buildings) generally cannot be replicated such that complex full-scale characteristics are obtained. Hybrid testing offers the ability to combine capabilities from physical and numerical modelling to overcome some of the experimental limitations. In this paper, the development of a coupled centrifuge-numerical model (CCNM) pseudo-dynamic hybrid test for the study of tunnel–building interaction is presented. The methodology takes advantage of the relative merits of centrifuge tests (modelling soil behaviour and soil–pile interactions) and numerical simulations (modelling building deformations and load redistribution), with pile load and displacement data being passed in real time between the two model domains. To appropriately model the full-scale scenario, a challenging force-controlled system was developed (the first of its kind for hybrid testing in a geotechnical centrifuge). The CCNM application can accommodate simple frame analyses as well as more rigorous and non-linear simulations using Abaqus. A novel data-exchange method between Abaqus and LabView is presented, which provides a significant enhancement compared with similar hybrid test developments. Data are provided from preliminary tests which highlight the capabilities of the system to accurately model the tunnel–building interaction problem.
Highlights
The complexity and level of sophistication of physical models tested within geotechnical centrifuges has developed considerably in recent years
The field programmable gate array (FPGA) controller loop was run at a real-time frequency of ≈ 500 Hz and used to (a) perform high-speed acquisition from the centrifuge instrumentation, comprised of four load cells, five LVDTs and 12 limit switches; (b) control the actuators to achieve target forces derived from the personal computer (PC) LabView program by implementing automatic load control using a proportional, integral, derivative (PID) algorithm; (c) communicate the system state to the PC LabView program; and (d) maintain mechanical system safety by limit switch monitoring and safe shut down protocol on failure of the intermittent keep-alive signal from the PC
This paper presented the development of the coupled centrifuge-numerical model (CCNM) hybrid test equipment and methodology
Summary
The complexity and level of sophistication of physical models tested within geotechnical centrifuges has developed considerably in recent years. In the area of tunnelling and tunnel–structure interaction, centrifuge modelling has enabled a better understanding of the parameters that control settlement trough shape (Mair et al, 1993; Marshall et al, 2012) as well as the interactions between tunnelling-induced ground displacements and buried infrastructure or foundations (Farrell et al, 2014; Franza and Marshall, 2018; Jacobsz et al, 2004; Marshall and Mair, 2011) These experiments have all included simplified models of structural systems. The purpose of this paper is to present the development of a hybrid testing methodology that takes advantage of the relative strengths of physical modelling using a centrifuge (focusing on the geotechnical domain) and numerical modelling (focusing on the structural domain) such that an accurate analysis of a tunnel–soil–pile–building interaction scenario can be achieved. Results are presented which demonstrate the effectiveness of the hybrid testing approach compared to a conventional centrifuge test for the tunnel–building interaction problem
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