Vol.2, No 10, 2000 pp. 1329-1348
UDC 624.074.43:624.041(045)
NONLINEAR FINITE ELEMENT ANALYSIS OF R/C SHELLS
Demosthenes G. Talaslidis 1, Aristotle Ch. Tokatlidis 2
1 Mete Sysm S.A., Th. Sofouli 56, 54655 Thessaloniki, Greece
E-mail: metesysm@otenet.gr
2 Department of Civil Engineering, Aristotle University, 54006 Thessaloniki, Greece
E-mail: talaslid@civil.auth.gr
Abstract. The paper focuses on the development and implementation of an appropriate finite element formulation and a macrolevel material model for the efficient and reliable nonlinear analysis of reinforced concrete (R/C) shell structures. Towards this aim, an element formulation is presented based on the Hu-Washizu principle. Independent approximations of displacements (bilinear), strains and stresses (piecewise constant) provide a consistent mechanism for describing the progressive variation of the material properties through the element. Furthermore, re-evaluations of stiffness coefficients and internal forces as well as correction of imbalances at successive increments become very simple, thus leading to a significant reduction of computational effort. The employed material model is based on the assumptions of the "Modified Compression Field Theory". This model in conjunction with a layered approach can in an expedient and economical way predict in a global sense the overall ultimate load behavior. Test examples are analyzed using the proposed approach and comparisons are made with measurements obtained from experimental investigations.
Key words: Finite Elements, Nonlinear Analysis, Reinforced Concrete, Shells.
NELINEARNA ANALIZA
KONAČNIH ELEMANATA R/C LJUSKI
Ovaj rad je usredsređen na razvoj i implementaciju odgovarajuće formulacije konačnog elementa i materijalnog modela makronivoa za efikasnu i pouzdanu nelinearnu analizu pojačanih konkretnih (re/inforce concrete R/C) ljuskastih struktura.U tom cilju formulacija elementa je predstavljena na osnovu Hu-Washizu-ovog principa. Nezavisne aproksimacije pomeranja (bilinearne), napona i naprezanja (konstantni po delovima) obezbeđuju konzistentni mehanizam za opisivanje progresivnih promena svojstava materijala kroz element. Sem toga, ponovna ocena koeficijenata krutosti i unutrašnjih sila, kao i korekcija neravnoteže u uzastopnim inkrementima postaju vrlo jednostavne, čime se ostvaruje smanjenje vremena izračunavanja. Korišćeni model materijala zasniva se na pretpostavkama "Modifikovane teorije kompresije polja". Ovaj model zajedno sa slojevitim pristupom može na ekspeditivan i ekonomičan način predvideti u globalnom smislu ukupno konačno ponašanje opterećenja. Test primeri su analizirani korišćenjem predloženog pristupa i izvršena su upoređivanja sa merenjima dobijenim na osnovu eksperimentalnih istraživanja.