Role of Physical Testing in Impact Analysis of Concrete Structures

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Title: Role of Physical Testing in Impact Analysis of Concrete Structures

Author(s): Peter H. Bischoff

Publication: Special Publication

Volume: 175

Issue:

Appears on pages(s): 241-260

Keywords: blast loads; concretes; impact tests; stresses; strains

Date: 12/1/1998

Abstract:
Reliable analitical methods are needed to aid the analysis and design of concrete structures under impact and blast loading. Calculated results from such an analysis are often compared and fitted with physical test results to validate the method of analysis employed. Material models used in the analysis must, account for strain-rate sensitive behavior, and these material models are also based on results from experiments. Hence, reliable development of material models and analytical techniques is contingent upon correct, observation of experimental results. This paper focuses on effects which could alter the test results and influence their subsequent interpretation, such as testing machine characteristics, inertia, time delays in measured signals caused be analogue filters, and vibrational energy. All of these effects can lead to incorrect, measurement of a test response under high strain-rate loading. Examples are given of incorrect measurement, of the compressive stress-strain response of concrete at strain-rates in the order of 0.1 s -1 , where results from such tests have been obtained with hydraulic testing machines. Failure to account. for inadequacies in the testing technique affected conclusions about changes in deformation behavior (such as stiffness and axial strain at peak stress). and also led to an apparent loss of ductility. Results from impact tests on a flexural member demonstrate how vibrational effects from a falling mass can lead to incorrect conclusions about the measured contact. load.