The present research is motivated by the need for accurate simulation of structural steel behavior under strong reverse or cyclic loading conditions, associated with excursions into the plastic range of the steel material. Under such loading conditions, several plasticity related phenomena such as the Bauschinger effect or the accumulation of plastic strain (often reported as ratcheting or cyclic creep) take place and need to be accurately predicted. The study concerns relatively thin-walled structural steel members, with emphasis on cylindrical shells (tubes and pipes). Those structural components, due to their relatively small thickness, often fail due to buckling when excessive compressive stresses are developed. The phenomenon of buckling becomes quite more complicated when cyclic loading is applied; in such a case, a progressive accumulation of plastic deformation occurs, leading to buckling under a relatively low level of loading.
The study is aimed at developing a large-strain plasticity constitutive model, based on the concept of bounding-surface plasticity, and incorporating the model into a nonlinear step-by-step nonlinear finite element solution of the governing equations (e.g. ABAQUS/Standard software). The constitutive model will take into account the accumulation of plastic deformation and possible degradation in every cycle. Subsequently, the numerical formulation and solution technique will be used to solve benchmark problems related to structural behavior and failure of steel structural members, subjected to cyclic loading. The developed methodology is applicable to steel structural components of arbitrary geometry; however, in the present research special emphasis will be given to elongated cylindrical (tubular) members, such as members of tubular lattice structures (e.g. offshore platforms, towers etc.), industrial piping components, steel pipeline segments (onshore and offshore), or steel catenary risers.
George E. Varelis
Spyros A. Karamanos
Publications in International Journals
- Varelis, G. E., Karamanos, S. A., and Gresnigt, A. M., “Steel Elbow Response Under Strong Cyclic Loading.”, Journal of Pressure Vessel Technology, ASME, accepted for publication, to appear 2012.
Publications in Conferences
- Giannakopoulos, A.E., Varelis, G.E. and Roumelioti, A.D., “Instrumented Dynamic Indentation of Metal Substrates by Sharp Indentors”, 8th HSTAM International Congress on Mechanics, pp. 585-592, Patras, Greece, July 2007.
- Varelis, G. E., Vathi, M., Houliara, S., and Karamanos, S. A., “Effect of UOE Manufacturing Process on Pressure Buckling of Thick-walled Pipes.”, 2nd South-East European Conference on Computational Mechanics, SEECCM, paper SE151, Rhodos, Greece, June 2009.
- Varelis, G. E., Vathi, M., Houliara, S., and Karamanos, S. A., “Effect of UOE Manufacturing Process on Pressure Buckling of Thick-walled Pipes.”, 10th International Conference on Computational Plasticity, COMPLAS X, Barcelona, Spain, September 2009.
- Varelis, G. E., Pappa, P. and Karamanos, S. A., “Simulation of Industrial Elbow Response Under Strong Cyclic Loading.”, COMPDYN 2011 Conference, Corfu, Greece, May 2011.
- Varelis G. E., Pappa P., Karamanos S.A., 2011, “Simulation of Industrial Elbow Response under Strong Cyclic Loading”,III ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, COMPDYN 2011, Corfu, Greece, 26–28 May 2011.
- Varelis, G. E., and Karamanos, S. A., “J2 Bounding-Surface Plasticity Models for Simulation of Strong Cyclic Loading of Structural Steel Components.”, 7th GRACM International Congress on Computational Mechanics, Athens, Greece, June 2011
- Varelis G.E., Pappa P., Karamanos S.A., 2011, “Finite Element Analysis of Industrial Steel Elbows Under Strong Cyclic Loading”, Pressure Vessels and Piping Conference, ASME, PVP2011, Baltimore, Maryland, 17 – 21 July 2011.
- Pappa P., Varelis G. E., Karamanos S.A., Stefanou G., 2011, “Effects of Material Variability on the Seismic Performance of Steel Buildings” , 7th National Conference on Steel Structures , Volos, Greece, 29 - 30 September and 1 October 2011.
- Varelis, G. E., Pournara, A. E., and Karamanos, S. A., “Strength and Stability of High-Strength Steel Tubular Beam-Columns Under Static and Cyclic Loads.”, 6th Eurosteel Conference, Budapest, Hungary, August 2011.
- Varelis, G. E., Papatheocharis, Ch., Perdikaris, P. C., Karamanos, S. A., “Experimental and Numerical Investigation of High-Strength Steel Welded Tubular Connections Under Monotonic and Cyclic Loading.”, 6th Eurosteel Conference, Budapest, Hungary, August 2011.
- Papatheocharis, Ch., Perdikaris, P. C., Varelis, G. E., Karamanos, S. A., “High-Strength Steel Welded Tubular Connections Under Extreme Loading Conditions.”, 7th National Conference on Metal Structures, Volos, Greece, September 2011
- Varelis, G. E., Gresnigt, A. M., and Karamanos, S. A., “Steel Elbow Response Under Strong Cyclic Loading.”, 22nd International Ocean and Polar Engineering Conference, ISOPE12, Rhodos, Greece, June 2012
- Varelis, G. E., Gresnigt, A. M., and Karamanos, S. A., “Steel Elbow Response Under Strong Cyclic Loading.” Pressure Vessel and Piping Conference, ASME, PVP2012-78346, Toronto, Canada, July 2012
- Varelis, G. E., Papatheocharis, T., PerdikarisP.C. and Karamanos, S. A., “Structural Performance of High-Strength Steel Welded Joints Under Out-of-Plane Extreme Loading Conditions - Experimental And Numerical Investigation.”, 14th International Symposium on Tubular Structures (ISTS 14), Paper No. 98, London, UK, September 2012.