RESEARCH PROJECT (PN-II-ID–PCE ID_193/2008)
Contract Number 605/2009
(January 2009-December 2011)
DESIGN AND SEISMIC PERFORMANCE EVALUATION OF 3D FRAME STRUCTURES USING ADVANCED NONLINEAR STATIC ANALYSIS METHOD
Prof.dr.ing. George M. Barsan
Conf.dr.ing. Zsongor F. Gobesz
Drd.ing. Szabolcs Varga
Sef.lucr.dr.ing. Mihai Nedelcu
IN RECENT YEARS, NON-LINEAR INELASTIC ANALYSIS METHODS OF STEEL AND REINFORCED CONCRETE FRAME STRUCTURES HAS BECOME THE FOCUS OF INTENSE RESEARCH EFFORTS BECAUSE OF RAPID DEVELOPMENT OF COMPUTER TECHNOLOGY AND THE NEED OF IMPLEMENTATION IN THE NEW DESIGN CODES, THE MORE RATIONAL ADVANCED ANALYSIS TECHNIQUES AND PERFORMANCE-BASED SEISMIC DESIGN PROCEDURES. WITH THE RAPID ADVANCEMENT OF COMPUTER TECHNOLOGY, RESEARCH WORKS ARE CURRENTLY IN FULL SWING TO DEVELOP THE ADVANCED INELASTIC ANALYSIS METHODS. IN SPITE OF THE AVAILABILITY OF SOME FEM ALGORITHMS AND POWERFUL COMPUTER PROGRAMS, THE NON-LINEAR INELASTIC ANALYSIS OF REAL LARGE-SCALE FRAME STRUCTURES STILL POSSES HUGE DEMANDS ON THE MOST POWERFUL OF AVAILABLE COMPUTERS AND STILL REPRESENTS UNPRACTICAL TASKS TO MOST DESIGNERS. ON THE OTHER HAND, STRUCTURAL RESPONSE TO STRONG EARTHQUAKE GROUND MOTIONS CANNOT BE ACCURATELY PREDICTED DUE TO LARGE UNCERTAINITIES AND THE RANDOMNESS OF STRUCTURAL PROPERTIES AND GROUND MOTION PARAMETERS. CONSEQUENTLY, EXCESSIVE SOPHISTICATION IN STRUCTURAL ANALYSIS IS NOT WARANTED. THE NEED FOR ACCURATE YET COMPUTATIONAL EFFICIENT TOOLS FOR THE NON-LINEAR ANALYSIS OF 3D FRAME STRUCTURES FORMS THE MAIN MOTIVATION BEHIND OF THIS WORK. THE RESEARCH PROJECT IS INTENDED TO OVERCOME THE EXISTING INCONVENIENCES AND DEVELOP AN INTEGRATED SYSTEM FOR ADVANCED STRUCTURAL ANALYSIS AND SEISMIC PERFORMANCE EVALUATION OF 3D STEEL AND REINFORCED BUILDING FRAMEWORKS WITH RIGID OR FLEXIBLE CONNECTIONS.
In recent years, non-linear inelastic analysis methods of steel and reinforced concrete frame structures has become the focus of intense research efforts because of rapid development of computer technology and the need of implementation in the new design codes, the more rational advanced analysis techniques and performance-based seismic design procedures [1-29]. Accurate and computationally efficient numerical models that represent the nonlinear behavior in beam-columns elements are thus required to simulate the seismic response and evaluate the performance of structural system.
With the rapid advancement of computer technology, research works are currently in full swing to develop the advanced inelastic analysis methods which can sufficiently represent the behavioral effects associated with member primary limit states such that the separated specification member capacity checks are not required. The reason for this is that, since advanced analysis [1-3] can directly asses the strength and stability of the overall structural system as well as interdependence of member and system strength and stability, separate member capacity checks are not required. A plastic zone analysis that includes:
- the spread of plasticity (gradual yielding of cross sectional fibbers and gradual developing along the member length)
- three dimensional plastic interaction curves
- local and global geometrical nonliniarities
- lateral-torsional buckling effects
- local buckling effects
- bowing effect
- nonlinear behavior of semi-rigid connections
- local and global geometrical imperfections
- physics imperfections, for instance the residual stresses in the case of hot-rolled steel members
- elastic unloading
- shear deformations effects
- and any other second-order behavioral effects,
would certainly be suitable to be classified as advanced inelastic analysis in which the checking of beam-column interaction is not required. As a result a plastic-zone solution is considered “exact”. Although the plastic-zone solution my be considered “exact”, it is not yet conducive to daily use in engineering design, because it is too computationally intensive and too costly in the case of 3D real-large scale frame structures. A number of computational models and computer programs have been developed, on this theory, in recent years by researchers [4-8; 12-14]. Unfortunately, the currently available methods are not user friendly for practical applications. These methods ignore many important characteristics and requirements for practical design, consistency between the linear and nonlinear models due to the need to use several elements per member to model the nonlinear effects and enhances the computational effort .
Since Kobe and Northridge earthquakes, a static inelastic analysis (pushover analysis) becomes an accepted and simple method for the seismic evaluation of high-rise buildings. The purpose of the pushover analysis is to evaluate the expected performance of a structural system by estimating its strength and deformation demands in design earthquakes using inelastic analysis, and comparing these demands to available capacities at the performance levels of interest. In this direction, the new design documents [24-26] have developed modeling procedures, acceptance criteria and analysis procedures for pushover analysis. In this context, the accuracy of demand prediction is desirable. On the other hand, pushover analysis has its limitations because it is based on static loading, so it cannot represent dynamic phenomena as well as a nonlinear dynamic analysis. A fundamental assumptions made for pushover analysis is that first mode dominates, and that the higher mode effects are not significant. To follow more closely the time variant distribution of inertial forces the adaptive force distribution or modal pushover procedures can be applied [19,22].
For three dimensional reinforced concrete frame structures inelastic behavior is dominated by the gradual yielding across the cross-sections and along the member length, associated with bi-axial bending and axial force, shear and torsional deformations, local and global second order effects. Although the methods based on plastic hinge concepts provide a good insight into the basic elasto-plastic behavior of structures a crucial drawback encountered in these methods is the neglect of gradual plastification across the cross-sections and along the member length which are important factors in the overall response of RC member and must be considered in an valuable pushover analysis.
The need for accurate yet computational efficient tools for the non-linear analysis of 3D frame structures (steel and reinforced concrete) forms the main motivation behind of the proposed research project. The research project is intended to overcome the inconveniences highlighted above and propose an efficient integrated system for both advanced structural analysis and performance based seismic evaluation tool for approaching real large-scale 3D semi-rigid steel and reinforced concrete frameworks, fulfilling the practical and advanced analysis requirements. The flexibility based approach will be used because is more accurate than the displacement-based methods because internal work is derived from an assumed force distribution function that relates the internal forces along the member length to the member end forces. The proposed non-linear static formulation is intended to model the geometrically non-linear inelastic behavior of steel and reinforced concrete beam-columns using only one element per member. This is an essential requirement to approach real large spatial frame structures, combining modeling benefits, computational efficiency and reasonable accuracy.
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18. Papanikolau, K.V., Elnashai, A.S., Pareja, J.F., Evaluation of conventional and adaptive pushover analysis II: Comparative results, Journal of Eartquake Engineering, 10 (1), 127-151, 2006.
19. Almeida,R., Carneiro-Barros, R., A "new" multimode load pattern for pushover analysis: The effect of higher modes of vibration, Advances in Eartquake Engineering, 13., 3-13, 2003.
20. Fajfar,P., P., Gaspersic, The N2 method for the seismic damage analysis of RC buildings, Eartquake engineering &Structural Dynamics, 25 (1), pp.31-46, 1996.
21. Krawinkler, H., G.D., Seneviratna, Pros and cons of a pushover analysis of seismic performance evaluation, Engineering Structures, 20(4-6), 452-464, 1998.
22. Chopra, A.K., R.K., Goel, A modal pushover analysis procedure to estimate seismic demands for buildings: summary and evaluation (Keynote Lecture), Fifth National Conference on Eartquake Engineering, Istanbul, Turkey, 2003.
23. Gupta, A., Kunnath S.K.,, Addaptive Spectra-based pushover procedure for seismic evaluation of structures, Eartquake Spectra, 16, 367-392, 2002.
24. Postelnicu, T., si col., P100/2006, UTCB, 2006.
25. Eurocode 8, Design of structures for earthquake resistance, January, 2003, European Committee for Standardization, 2003.
26. FEMA 356 — Prestandard and Commentary for the Seismic Rehabilitation of Buildings, Federal Emergency Management Agency, 2000.
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28. Rosati, L., Marmo, F., Seroieri, R., Enhanced solution strategies for the ultimate strength analysis of composite steel-concrete sections subject to axial force and biaxial bending, Computer Methods in Applied Mechanics and Engineering, 197(9-12), 1033-1055, 2008.
29. Long, H.V., Nguyen, D.H, Limit and shakedown analysis of 3D steel frames, Engineering Structures, in press, doi.10.1016/j.engstruct.2007.12.009., 2008.
(A) Refereed papers in international journals
1. Chiorean, C.G., A Computer Method for Nonlinear Inelastic Analysis of 3D Composite Steel-Concrete Frame Structures, Engineering Structures, Vol. 57, pp. 125-152, Elsevier Science Publisher, Oxford, UK, 2013.
2. Chiorean, C.G., A Computer Method for Rapid Design of Composite Steel-concrete Cross-sections, Open Civil Engineering Journal, Vol 7(1), pp. 1-17 Bentham Science Publisher, 2012.
3. Chiorean, C.G., Computerised Interaction Diagrams and Moment Capacity Contours for Composite Steel-Concrete Cross-Sections, Engineering Structures, Vol 32, No. 11, pp. 3734-3757, Elsevier Science Publisher, Oxford, UK, 2010.
4. Chiorean, C.G., A Computer Method for Nonlinear Inelastic Analysis of 3D Semi-Rigid Steel Frameworks, Engineering Structures, Vol. 31, No.12, pp. 3016-3033, Elsevier Science Publisher, Oxford, UK, 2009.
(B) Refereed papers in international conferences
1. Chiorean,C.G., Chira, A., Buru, M., A computer method for design and M-N-Phi analysis of composite steel-concrete cross-sections, Proceedings of the Fifth International Conference on Structural Engineering, Mechanics and Computation (SEMC 2013), Cape-Town, South Africa, 2013.
2. Chiorean,C.G., Buru, M., Chira A., Marchis I., Nonlinear inelastic analysis of 3D composite steel-concrete frameworks, Proceedings of the Fifth International Conference on Structural Engineering, Mechanics and Computation (SEMC 2013), Cape-Town, South Africa, 2013.
3. Chiorean C.G, Tarta G., Marchis I, Buru M., Computer-Based Nonlinear Analysis Method for Seismic Performance Assessment of 3D Steel Frameworks, The Eleventh International Conference on Computational Structures Technology, CST 2012, Civil Comp Proceedings, Stirlingshire, UK 2012.
4. Chiorean, C.G. A fast incremental-iterative procedure for ultimate strength analysis and design of composite steel-concrete cross-seections, Proceedings of International Conference STESSA 2012, Chile.
5. Chiorean C.G., Tarta G., Barsan G.M., Gobesz ZS, Nedelcu M., Computer based nonlinear analsysi method for seismic performance assesment of 3D frameworks, Proceedings of International Conference STESSA 2012, Chile.
6. Chiorean, C.G., Barsan, G.M., Ciplea C, A fast iterative procedure for ultimate strength analysis and design of composite cross-seections, Proceedings of International Symposium IABSE-IASS, Taller, Longer, Lighter, London, UK.
7. Chiorean, C.G., Barsan G.M., Varga S., Ciplea, C, Nedelcu, M., Large deflection distributed plasticity analysis pf 3D composite steel-concrete frameworks, Proceedings of International Symposium IABSE-IASS, Taller, Longer, Lighter, London, UK.
8. Chiorean C.G., A Fast Incremental-Iterative Procedure for Ultimate Strength Analysis and Design of Composite Steel-Concrete Cross-Sections, Thirteen International Conference on Civil, Structural and Environmental Engineering Computing, Civil-Comp Press, 2011.
9. Chiorean, C.G., Barsan, G.M., Varga, S., Large deflection distributed plasticity analysis of 3D composite steel-concrete frameworks, Proceedings of International Conference on Computational & Experimental Engineering and Sciences (ICCES 2010), Las Vegas, USA, Technical Science Press Publisher, 2010.
10. Chiorean, C.G., Barsan, G.M., Large deflection distributed plasticity analysis of 3D semi-rigid steel frameworks, IJSSD Symposium, Progress in Structural Stability and Dynamics, Proc. Of International Journal of Structural Stability and Dynamics, Hong Kong, China, 16-18 Dec., 2009 http://www.hkisc.org.
11. Chiorean C.G., A fast incremental-iterative procedure for ultimate strength analysis of composite cross-sections of arbitrary shape, Transactions on Modelling and Simulation, WIT Press Publisher, UK, 2011. www.witpress.com
(C) Papers in national/international conferences
1. Chiorean, C.G., Metoda numerica eficienta pentru trasarea curbelor de interactiune plastica a sectiunilor compozite otel beton, Simpozionul “Structuri metalice solicitate la actiuni extreme”, ZAT Timisoara, Romania, 2009.
2. Chiorean, C.G., Gobesz, Zs., Varga, S., Efficient structural analysis modelling of 3D frameworks, 14th International Conference on Civil Engeneering and Arhitecture , ÉPKO 2010, Șumuleu Ciuc, Romania, June 3-6, 2010.
3. Chiorean, C.G., Gobesz, Zs., Varga S., Efficient structural analysis of 3D frameworks. Examples, 14th International Conference on Civil Engeneering and Arhitecture , ÉPKO 2010, Șumuleu Ciuc, Romania, June 3-6, 2010.
4. Varga S., Chiorean, C.G., Determination of the target displacement using pushover analysis and directly generated inelastic spectra from Vrancea earthquake records, 14th International Conference on Civil Engeneering and Arhitecture , ÉPKO 2010, Șumuleu Ciuc, Romania, June 3-6, 2010.
5. Chiorean C.G., Analiza si Dimensionarea la Starea Ultima de Rezistenta a Sectiunilor Compozite Otel-Beton, A 12-a Conferinta Nationala de Constructii Metalice, 26-27 Noiembrie 2010, Timisoara, Romania.
6. Chiorean C.G., Petran I., Varga Sz., Analiza Statica Neliniara A Structurilor Compozite Otel-Beton Spatiale, A 12-a Conferinta Nationala de Constructii Metalice, 26-27 Noiembrie 2010, Timisoara, Romania.
II. SOFTWARE DEVELOPED
III. SCIENTIFIC REPORTS
cosmin dot chiorean at mecon dot utcluj dot ro
Professor C.G. CHIOREAN
Faculty of Civil Engineering
15 C Daicoviciu Str. , RO-400020