بررسي انرژي كرنشي دروني سازه در زلزله‌هاي حوزه‌ي نزديك‌

STRAIN INPUT ENERGY IN NEAR-FAULT GROUND MOTIONS

The effect of near-field eart hquake record s on th e strain inpu t energy of st ructures is investigat ed in this paper . Near-field records differ from other types of record by special characte rist ics. Long-period pulses , which are added to background records, are examples of those special features that are st udied in this paper. Although both pulses and background record s are stat istical objects , th e pul ses usually behave more deterministi cally tha n und erlying records. Considering this poin t , it is reason able to compute the response of a st ruct ure to such eart hquakes in two ste ps (i.e. deterministic and probabil istic phases) and, th en , supe rimpose the resul t s. Handling responses to near-field record s in thi s way lead s to more accur at e response evaluations, because of ext racting the deterministic part of the result s from th e st at ist ical procedure. For thi s purpose, th e response of different struct ures to near-field record s is evalua ted and the resul ts are proposed in the form of energy spec tra. The findings show t hat, in near-fault zones , an increase in ground mot ion magn itude results in higher spectral peak strain energy and, also, a higher period of occnrren ee , respecti vely. It is found th at , close to th e fault , ʹo the response is primarily govern ed by the pulse characteristic rather than by the background record. This trend inverts gr adually as the distance to th e fault increases. In int erm ediate regions , th e energy sp ectra experience two major peaks, which corresp ond to the site dominant period and the pulse period, correspondingly.