Experiments On Concrete Under Shock Loading
Free (open access)
N Herrmann, J Eibl & L Stempniewski
On detonations or hypervelocity impacts concrete structures are loaded with shockwaves. These shockwaves cause a steep increase in pressure within the wavefront which propagates at high velocity. For a numerical simulation of such process a constitutive material law F = f (e, e, T) is needed which adequately describes concrete under these conditions. As basis for such a constitutive law tests on concrete under explosive loads were performed and different material parameters were investigated. We report our approach to measure material parameters during tests with different explosive charges on concrete and our model tests for demolition work. We got first experience in using a new temperature sensor, called the atomic layer thermopile, to measure the temperature raise caused by the adiabatic compression. This sensor was developed for performance measurement of high energetic laser pukes, The mode of operation of this sensor is based on the temperature gradient between the sensor surface and the base of the device. Very fast response time is possible, because there is no need of getting a complete heat transfer from the ambient concrete temperature to the whole sensor. Responsible for the output voltage proportional to the temperature rise is the thermal Seebeck-effect which can be splitted in a longitudinal and a transversal component due to the orientation of the layers. For stress measurement manganin gauges and for strain measurement ordinary strain gauges were used. For the application of these methods at high velocity loads in concrete special encapsulations are needed in order to save the functionality and to provide fast rise times of the output signals. Results of the measurements will be shown and remaining problems will be discussed.