Nico Herrmann

PACE-1450 - An Experimental Test Setup for the Investigation of the Crack Behaviour of Prestressed Concrete Containment Walls

Among other topics the crack initiation and the leakage through prestressed concrete walls of reactor containments are matters of particular interest for the safety of nuclear facilities. Experimental investigations under different loads which also include the limit state under accidental conditions are the basis for the implementation of these problems in finite element codes. The validity of models that are used in nonlinear calculations has to be verified by comparing their performance with experimental results. In order to determine the capability of simulations to predict the structural behaviour of realistic and representative structural parts these kind of complex tests are indispensable. The PACE 1450 experimental project is an intermediate sized experiment to investigate the behaviour of a curved specimen which is representative for the prestressed containment of a 1450 MWe nuclear power plant. The specimen is loaded by air pressure simulating the internal pressure within the reactor containment under inspection and accidental conditions. The resulting ring tensile stresses of the cylindrical part of the containment are applied externally by eight hydraulic jacks. The initial prestressing of the specimen is realised in such a way that a decreasing of the prestressing force for the purpose of simulating the aging of the structure is possible.© 2008 ASME

The PACE-1450 Experiment – Investigations Regarding Crack and Leakage Behaviour of a Pre-stressed Concrete Containment

The subject of the project “PACE-1450 – Experimental Campaign” was to complement the variety of research programs dealing with the leakage behaviour of concrete containments of nuclear power plants under accidental conditions. The test campaign has been run with a specimen of realistic dimensions, reinforcement and pre-stressing. Supplementary investigations on the crack pattern of the used specimen are underway. Leakage tests have been performed under different temperature and pressure conditions with varying media mixtures of air and steam. This paper summarizes the results of the air leakage investigations at different temperatures.

The PACE-1450 Test Campaign - Leakage Behaviour of a Pre-Stressed Concrete Containment Wall Segment

Investigating nuclear power plant containments under accidental conditions obviously leads to the question of possible leakage through cracks of the pre-stressed concrete containment. In the last decades a number of civil engineering R&D programs dedicated to theoretical and experimental analyses have been performed. For the PACE-1450 experiment a leakage testing facility for pre-stressed curved specimen has been built in the laboratory of the Materials Testing and Research Institute (MPA Karlsruhe) at the Karlsruhe Institute of Technology (KIT). The test campaign has now been successfully finished with the evaluation of gained results still ongoing. The first half of the campaign was mainly dedicated to the cracking of the realistically reinforced specimen while the second half was focussing on the leakage behaviour of the cracked specimen. In the tests cold air, heated air and air-steam mixtures were used.

Impact of soft missiles – evaluation of load-time functions

The threat spectrum of safety-related structures has severely changed since 11 September 2001. The deterioration capability of large aircrafts impacting on structures has become aware in a dramatic manner. Simplified calculation models for aircraft impact are available but have not been verified for large commercial aircrafts. Based on this background, experimental studies are performed at the Materials Testing and Research Institute (MPA) Karlsruhe of the Karlsruhe Institute of Technology (KIT) to examine the shape and the peak loads of load-time functions induced by an impacting soft missile where the mass and stiffness distribution is similar to a commercial aircraft. The characterisation of the impact phenomena and their variation due to changing test parameters is the goal of these experiments. The experimental set-up, measurement results and their evaluation will be presented. First numerical simulation results will be shown and briefly compared to the prediction using the analytical Riera method.

Evaluation of Load-Time Functions Due to Impact of Soft Missiles

The threat spectrum of safety related structures has severely changed since September 11, 2001. The deterioration capability of large aircrafts impacting on structures has become aware in a dramatic manner. Simplified calculation models for aircraft impact are available but have not been verified for large commercial aircrafts. Based on this background, experimental studies are performed at the Materials and Testing Research Institute (MPA) Karlsruhe of the Universitat Karlsruhe (TH) to examine the shape and the peak loads of load-time functions induced by an impacting soft missile with a mass and stiffness distribution along the missile’s axis similar to a commercial aircraft onto a rigid target. Different levels of water filling for simulating the kerosene tanks can be realised to investigate their influence on the load-time function. The characterisation of the major impact phenomena and their variation due to changing test parameters is the foremost goal of these experiments. The missiles are accelerated up to the impact velocity using an air-pressure gun. Impact forces are measured with a piezoelectric measuring platform as well as with accelerometers positioned on the target. The impact is filmed using a high-speed video camera. The experimental setup, measurement results and their evaluation will be presented in detail. The experimental study forms the reference for accompanied numerical calculations using the explicit finite element code LS-DYNA. Thus, a numerical model validated on the experiments shall be generated in order to provide an enhanced confidence level for the future calculation of real impact scenarios. First simulation results will be shown and briefly compared to the solution using the Riera method. A possible enhancement of this analytical method based on the experiments is beyond the scope of the project.Copyright