Abstract
Rockfall protection barriers are connected to the ground using steel cables fixed with anchors and foundations for the steel posts. It is common practice to measure the forces in the cables, while to date measurements of forces in the foundations have been inadequately resolved. An overview is presented of existing methods to measure the loads on the post foundations of rockfall protection barriers. Addressing some of the inadequacies of existing approaches, a novel sensor unit is presented that is able to capture the forces acting on post foundations in all six degrees of freedom. The sensor unit consists of four triaxial force sensors placed between two steel plates. To correctly convert the measurements into the directional forces acting on the foundation a special in-situ calibration procedure is proposed that delivers a corresponding conversion matrix.
Highlights
Fence-like steel structures are often used to protect against rockfall
The so-called flexible rockfall protection barriers consist of a main steel wire net that is spanned by steel cables and posts
Given the fixed installation in the field, we propose an in situ calibration procedure, which allows a regular surveillance of the measurement system and fulfils the calibration requirements given in [1] for the approval tests of rockfall protection systems
Summary
Fence-like steel structures are often used to protect against rockfall. The so-called flexible rockfall protection barriers consist of a main steel wire net that is spanned by steel cables and posts (see Figure 1). The estimations are based on the forces measured in the ropes that are attached to post heads and at the post bases or in adjacent ground plates This approach may be sufficient to account for the main pressure loading that is transferred to the ground by hinge supported posts. It does not account for the high tensile forces sustained by post foundations and anchorages commonly used for clamped posts. Another reason for more detailed measurements is the increasing number of numerical simulations of such flexible protection systems as described in [4,5,6,7]. Given the fixed installation in the field, we propose an in situ calibration procedure, which allows a regular surveillance of the measurement system and fulfils the calibration requirements given in [1] for the approval tests of rockfall protection systems
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