INFLUENCE OF THE RESPONSE OF A SHALLOW FOUNDED REINFORCED CONCRETE FRAME STRUCTURE ON SOIL LIQUEFACTION POTENTIAL

Nakon katastrofalnih posljedica potresa na Aljasci i u Niigati 1964. godine, Seed i Idriss su razvili i objavili metodu za procjenu otpornosti tla na likvefakciju pod nazivom „pojednostavljeni postupak“. Dugo vremena se smatralo kako prisutnost građevine smanjuje opasnost od pojave likvefakcije, no nakon nedavnih potresa (Kobe 1995. i Kocaeli 1999.) uočeno je kako se likvefakcija pojavila ispod temelja građevina, iako nije došlo do njezinog pojavljivanja na slobodnim površinama tla u okolici građevina. U ovome radu analiziran je i uspoređen likvefakcijski potencijal tla neopterećenog objektom i tla ispod građevine, za dva profila relativno mekog tla u Osijeku pri djelovanju dva potresa različitog frekventnog karaktera i magnitude. Linearno-elastične analize vremenskim zapisom provedene su koristeći računalni program SAP2000 za slučaj neopterećen objektom i za slučaj prisutnosti i utjecaja odziva plitko temeljene armiranobetonske okvirne konstrukcije. Dodatno su prikazani i osnovni dinamički odzivi same konstrukcije u interakciji s tlom, te je dana kratka usporedba s općeprihvaćenim modeliranjem apsolutno krutih oslonaca konstrukcije.Following disastrous earthquakes in Alaska and in Niigata in 1964, Seed and Idriss developed and published a method for evaluating liquefaction resistance of soils termed the ‘‘simplified procedure’’. For a long time it has been considered that the presence of the building reduces the risk of liquefaction, but after the recent earthquakes (Kobe 1995. and Kocaeli 1999.) it was observed that the liquefaction occurred under the foundations of buildings, although it has not been observed in the free field around buildings. This paper analyzes and compares soil liquefaction potential in the free field and beneath the building, for two relatively soft soil profiles under the influence of two strong motions with different frequency character and magnitude. A linear-elastic time history analysis was conducted using computer program SAP2000 for the free field case and case with presence and response impact of a shallow founded reinforced concrete frame structure. In addition, basic dynamic response of the structure in interaction with the soil is presented and a short comparison is made opposite to the widely accepted rigid-base structure assumption