Test center for support structures
At the Faculty of Civil Engineering and Geodesy of the University of Hannover
Experimental studies on a large scale
Large-scale experimental studies are necessary to investigate the fatigue and load-bearing behavior of wind turbine foundations and support structures. Simulation results are validated based on the results. The test center is involved in numerous research projects and carries out extensive test campaigns here on large structural components of onshore and offshore wind turbines.
Foundation test pit
With its dimensions, the foundation test pit is the largest test facility of its kind in the world. In it, large-scale foundation elements can be realistically tested statically and cyclically. Hydraulic cylinders are used to apply the loads uni-axially and multi-axially. A vertical span along the long side of the pit with a height of 8 m extends the loading possibilities.
In order to achieve homogeneous soil conditions for the tests, the sand is first removed from the pit and then re-installed in compacted layers. The storage density is documented in the process. A targeted amount of water in the soil can be adjusted by four wells. Thus, almost homogeneous boundary conditions can be created for the tests. Different soil layers, such as with clay, can also be viewed.
The size of the test pit also allows different types of pile installation, such as percussive or vibrating driving, to be investigated. During installation and testing, the structural behavior can be analyzed to validate the calculation and simulation model.
3D clamping field
In the clamping field, large-scale components and large models can be tested under static, dynamic and cyclic loads. The test stand consists of a 200 m² solid floor slab, which is bounded on two sides at right angles by a prestressed and flexurally rigidly connected reinforced concrete wall. The specimen can be loaded uni-axially or multi-axially via hydraulic cylinders. The test cylinders generate forces between 100 and 2,000 kN. The test frequency varies between 0.1 and 5 Hz. A realistic loading of the structures is thus possible.
The geometry of the span and the height of the abutment walls connected to it enable the testing of a wide variety of structural components, such as grouted joints or hollow section nodes. They can be tested standing and lying on the clamping field. In an international comparison, this span is definitely a unique feature due to its three-dimensionality and size.
Due to the extensive equipment of the test center, it is possible to realize a variety of different test setups on the 3D tensioning field and in the foundation test pit. This places equally high demands on the test peripherals and measurement data acquisition.
The load introduction structures make it possible to realize the most diverse variants for an installation of the test cylinders and thus load introduction. Test specimens can be loaded vertically and horizontally in multiple axes. A total of 13 test cylinders with test forces from 100 kN to 2 MN are available to load the structures. Up to six axes can be operated in one test on the 3D clamping field and simultaneously in the foundation test pit. Both large-scale test rigs each have an independent control and regulation unit and their own measurement data acquisition.
Experimental possibilities and focal points
- large-scale static and dynamic tests on components and structural elements
- Further development of construction techniques for installing the supporting structure and its foundation elements (e.g. driven, drilled and screwed piles)
- Tests with high numbers of load cycles to investigate the fatigue strength of relevant joining techniques, such as bolted, welded, adhesive and hybrid mated joints.
- Large-scale testing of structural health monitoring (SHM) procedures.
- high-frequency durability tests on material samples and components
- Investigation of soil-structure interaction in soil conditions that are as real as possible.
- Investigation of the behavior of large-scale foundation elements in soil conditions as real as possible under cyclic loading.
- Soil mechanics tests to ensure reproducible placement of the test soil.
- Investigation of triaxial stress states in soil samples
- Investigation of the strength development and processing properties of highly hardened mineral fine-grained concretes
- Development of repair processes with composite materials