Facilities for the transmission and production of electric power are erected in all regions of the world - also in such areas, where the occurrence of earthquakes cannot be excluded or should even be expected. In order to ensure plant security, here the verification of stability, integrity and function of systems and components is required considering earthquake-specific loads. These manifest themselves mainly in ground agitation spreading out to buildings and components as well as to individual devices. For its verification there are many different country- and region-specific standards and guidelines with different excitation spectra describing the occurring load factors. Which standards and degrees of inspection are relevant, depends on the question in which region and in which building and/or building level the component is to be used. Standard components which are to be qualified for world-wide employment without restrictions thus often have to meet numerous test specifications.
IABG provides consulting regarding the selection of the load types to be verified and with the definition of test specifications while covering all requirements to be considered. For over 30 years, IABG has been performing experimental verifications on the purpose-built servo-hydraulic multi-axis oscillation table (HyMAS) whose initial design has been continually improved. With this test stand, the seismic loads on components or overall systems can be simulated in real time up to a weight of 10 tons. To qualify them for employment under these extreme loads, the behaviour of the items under test can be monitored via various measurement systems.
If necessary, IABG accompanies and supplements the experimental verifications with calculation methods. In the preparatory phase, the test rigs are defined and optimised using modal analyses and linear finite element (FE) calculations, with which the items under test are attached to the oscillation table. Testing can be accompanied by calculated response analyses with respect to time and frequency to evaluate the relevance of various test requirements and to supplement and interpret the experimental results concerning the vibration behaviour and strength of the test items. The used models and methods are then verified and optimised via model updates. As a rule, a shock response analysis is carried out in the frequency range in a subsequent step. In addition, linear and non-linear analyses can be used in the time domain for more exact statements and comparisons of measuring data.
The combination of experimental and calculated analyses guarantees an optimised and economic verification process. After alignment of an FE model with test data regarding local stiffness, material data and absorption, the test results can be transferred - under certain conditions - to similar sized products and constructions via calculation methods.
The methodology outlined above was used with a step switch for power transformers in the course of a current project. After alignment of the FE model on basis of quasi-static tests as well as a modal analysis, high conformity of the characteristics was attained. A shock response analysis could thus be carried out on a secured basis. Due to the combined approach, ranges which in the test were difficult to access via instrumentation could be supported by means of an FE analysis. This ensured a local load analysis and strength evaluation also for cross-sections only accessible with difficulty.
Our test laboratories are accredited according to DIN EN ISO 17025 and fulfil the high quality requirements within the sectors of vibration testing and earthquake simulation. Beyond that, they are subject to regular quality control tests by the German Accreditation Body (DAkkS). In the context of our co-operation with product manufacturers and system operators in the area of oscillation testing, we have carried out over 800 individual tests in the past years. This impressively underlines our know-how as testing and development facility.
