Kristian Schellenberg

A Dynamic Design Method for Rockfall Protection Galleries

Galleries are common structures to protect roads and railways from rockfall hazards. The design concepts in recent guidelines are based on the application of a static equivalent impact force. This approach is simple to use for practicing engineers. However, the dynamic behavior of the structure is not adequately taken into consideration. An analytical model based on a system of multiple degrees of freedom is proposed, which enables predicting shear and bending failure of the gallery due to the impact of a falling block of rock. Several simplifications allow numerically solving the basic equations by means of a spreadsheet. In large-scale tests reinforced concrete slabs, measuring 3,5 m × 4,5 m and with two different thicknesses, were subjected to increasing impact loads up to failure. The measured decelerations in the block and the reaction forces at the supports provide the required data to verify the analytical model. The evaluation of an existing structure shows that for dimensions of average Swiss galleries failure is governed by punching shear.

The Impact of the Sunniberg Bridge on Structural Engineering, Switzerland

Abstract The Sunniberg Bridge close to the village of Klosters, Switzerland, was completed in 1998 and commissioned in 2005, after having served as an access to the adjacent tunnel construction site. It has gained worldwide recognition as a symbol for technical excellence and a representative of new bridge types. The successors of the designer and the owner representative at that time retell the history of authorship, design, planning, execution, commissioning and recognition from an outsider’s perspective and assess the structural behaviour in the first ten years. The impacts of the bridge on the development of bridge types, on the prestige of the various parties involved and the influence and the perception of erection costs are assessed. Finally, some issues of durability and maintenance that will occupy the responsible authorities in future are mentioned.

Impact Behavior of Reinforced Concrete Slabs Subjected to Rock Fall Loading

This research aims at providing a better understanding of the dynamic behavior of rock fall protection galleries. Analytical, numerical, and experimental research tests were conducted in order to improve the prediction accuracy in determining the impact load capacity. According to a survey of galleries in Switzerland, relevant geometries for the tests were chosen in a scale of about 1:2. Concrete slabs with lateral dimensions of 3.5 x 4.5 m and a thickness of 0.35 m were subjected to falling weight impacts with increasing falling height. Measuring the reaction forces as well as strains in the reinforcement and on the concrete surface, the required data to validate an analytical model was obtained. The observed crack patterns of the slabs due to the impacts are discussed; the impact load and strains can be predicted using an analytical model consisting of 3 masses and 3 nonlinear springs. As a comparison, the values given by the design guidelines of Switzerland and Japan are illustrated as well.