Application of a dynamic photoelasticity technique for the study of twoand three-dimensional structures under seismic shock and explosive loads effect

摘要

Abstract: This paper considers the examples of the experimentalsolution of some engineering dynamic problems studiedat the Photoelasticity Laboratory of Moscow CivilEngineering Institute: the stress state of the holeslocated either near the free surface or deep in themedium under the impulsive and seismic loadings; thestress state of concrete gravitational dams; thedefensive effect of screens under the loading bysurfacing explosives; and three-dimensional dynamicstress state of forging hammer striking elements. Thepresent dynamic photoelasticity techniquestate-of-the-art allows for study of variousengineering constructions and structures in elasticconditions under the effect of wave loads. Through thepast years, technique development was mainly directedto experiment facility perfection (utilizing newhigh-speed cameras; development of effective ways ofloading the models, as well as three-dimensional andvolumetric structures with the help of magneticinductors; application of holographic interferometrywith mono- and multipulse lasers) and researchprocedure development of stress waves in the plane andvolumetric elastic problem, anisotropic andviscoelastic media. In the problems of wave mechanics,one basic parameter determining the stress state ofstructures or constructions is the relation betweenconstruction geometric characteristics and the lengthof the wave effect. A dynamic photoelasticity techniqueallows wide variation of this relation and an easychange of a construction geometric configuration, thusdetermining the laws of wave phenomena taking place inthe models studied. In simulating underground holes,lateral dimensions of which are comparable with thedistance from the free surface and with the length ofpropagating waves, a seismic stress state is defined inwave conditions by a direct experiment. In this case wehave to take into account a variety of wave typesaffecting the cavity and the basic stress change of theenvironment in the construction range (i.e., a dynamicstress state of the corresponding point of theenvironment, the construction being absent). For a holelocated in the pre-surface zone the stress state wasstudied at the contour caused by a longitudinalcompression wave interacting with the free surfaceunder different angles of incidence and Rayleigh wavepropagating from a surface source.!5