HAZARD ASSESSMENTS FOR EXTREME DYNAMIC LOADINGS

Abstract

THIS ARTICLE DISCUSSES THE ROLE OF THE PLASTIC METHODS OF ANALYSIS IN THE DESIGN PROCESS FOR THE PROTECTION AND SAFETY OF STRUCTURAL SYSTEMS SUBJECTED TO EXTREME IMPACT, EXPLOSIVE AND DYNAMIC LOADINGS. THESE POTENTIAL HAZARDS WOULD CAUSE LARGE DEFORMATIONS AND LARGE INELASTIC STRAINS IN STRUCTURAL COMPONENTS AND RUPTURE AND FAILURE OF THE MATERIAL IN EXTREME CASES. THE DUCTILE BEHAVIOUR AND FAILURE OF STRUCTURES IS INTRODUCED BRIEFLY FROM THE PERSPECTIVE OF HAZARD PROTECTION. THE ACTUAL STRUCTURAL MEMBERS OF A SYSTEM CAN BE DESIGNED TO ABSORB A PORTION OF THE EXTERNAL DYNAMIC ENERGY, OR DEDICATED ENERGY ABSORBERS MAY BE INCORPORATED INTO A STRUCTURAL SYSTEM. THE ELASTIC AND PLASTIC STRESS WAVES GENERATED BY AN IMPACT LOADING ARE FOUND TO EXERCISE SIGNIFICANT EFFECTS ON THE DYNAMIC RESPONSE OF THIN-WALLED STRUCTURES. THEY ALTER THE DEFORMATION MODE AND THE CRUSHING DISTANCE, WHICH IS AN IMPORTANT PARAMETER IN THE DESIGN EQUATIONS RELATED TO THE HUMAN IMPACT INJURY CRITERIA. THE SCALING LAWS FOR RELATING THE DYNAMIC RESPONSE OF A SMALL-SCALE TEST MODEL TO THE BEHAVIOUR OF A FULL-SCALE PROTOTYPE ARE SATISFIED, APPROXIMATELY, FOR THE LARGE DUCTILE DEFORMATION BEHAVIOUR OF THE SEVERAL STRUCTURAL COMPONENTS WHICH HAVE BEEN STUDIED. HOWEVER, THE LAWS ARE NOT SATISFIED AND, IN FACT, ARE NON-CONSERVATIVE, WHEN MATERIAL FAILURE OR RUPTURE INTERVENES IN THE RESPONSE.