惯性力和塑性铰_香港科技大学余同希讲座.pdfVIP

CHAPTER 4. INERTIA FORCE ANDINERTIA FORCE AND PLASTIC HINGE 44.11 RelationRelation betweenbetween wavewave propagationpropagation andand global structural response 4.2 Inertia forces in slender bars 11 4.3 Plastic hinges in a pulse-loaded rigid- plastic free-free beam 4.1 RELATION BETWEEN WAVE PROPAGATION AND GLOBALPROPAGATION AND GLOBAL STRUCTURAL RESPONSE 22 INTRODUCTION Response of a structure  TTo quasii-sttatitic lloadiding: ddefformatition, sttraiin andd sttress  To intense dynamic loading: wave propagation; inertia effecteffect For beams, arches, plates, shells, one dimension (thickness) main dimension (length or radius etc.)  First, a transverse dynamic load causes elastic and plastic wave propagation through the thickness, which may lead to a failure by spalling 33 possible spalling INTRODUCTION (CONT’D)  Time scale:  WaveWave propagationpropagation occursoccurs onlyonly inin thethe samesame orderorder ofof timetime thatthat itit takestakes a stress wave to propagate through the thickness of the structure  typically few microseconds  AftAfter ththroughh-thithickkness wave reflflectts severall titimes, ththe sttress allong thickness direction dramatically reduces, while each cross-section moves as an entirety. This long-term dynamic behavior is called (global)(global) strstructcturalral responseresponse  several milliseconds or much longer  ForFor structuralstructural responseresponse  early time wave propagation is disregarded  but the inertia of the structure still plays essential role  ththe extternal