Estimating the Loading Pattern Factor of Modal Pushover Analysis (MPA) for Integrated Bridges Using IDA Responses

Document Type : Technical Note

Authors

Islamic Azad University, Science and Research Branch, Tehran

Abstract

In this paper, a new applied relationship is introduced for the analysis of integrated bridges where no expansion joint embedded on the deck. It can be used to investigate the seismic behavior and actual performance of integrated bridges under earthquake force and, in spite of its simplicity, its accuracy is acceptable. In fact, this relationship can be considered as a combination of incremental dynamic analysis and modal pushover analysis, benefiting from the advantages of both approaches, i.e. an appropriate loading pattern factor of Modal Pushover Analysis can be obtained by using Incremental Dynamic approach. To this end, the average acceleration - displacement and average acceleration - shear base of 120 earthquake records applied on the bridge are calculated and then the obtained incremental dynamic curve is plotted in the coordinates of displacement and shear base. For the obtained modal pushover curve, the sum of the first three SRSS modes is selected. The literature shows no record of the study conducted on the comparison of the two curves. In this paper, the aforementioned comparison was made using Incremental Dynamic Approach through examining six regular and irregular integrated bridges and applying 120 earthquake records in 10 acceleration levels. It was observed that the accuracy of the proposed relationship in predicting the bridge displacements and shear forces of columns' piers was high, and the calculation output showed negligible differences with dynamic analyze results. In this study, the soil-structure interaction is ignored.

Keywords


Isakovic, T. and Fischinger, M. (2006) Higher modes in simplified inelastic seismic analysis of single column bent viaducts. Earthquake Engineering
and Structural Dynamics, 35(1), 95-114.
Maalek, S., Akbari, R., and Ziaei-Rad, S. (2010) The effects of the repair operations and replacement of the elastomeric bearings on the modal
characteristics of a highway bridge. Structure and Infrastructure Engineering, 6(6), 753-765.
Pinho, R., Monteiro, R., Casarotti, C., and Delgado, R. (2009) Assessment of continuous span bridges through nonlinear static procedures. Earthquake
Spectra , 25(1), 143-159.
AASHTO, T. (2007) Resistance of Compacted Bituminous Mixture to Moisture Induced Damage for Superpave. American Association of State Highway and Transportation Officials, Washington, DC.
Caltrans, S.D.C. (2010) Caltrans Seismic Design Criteria . Vol. 1.6. California Department of Transportation, Sacramento.
Miles, J.C. and Moore, C.J. (1991) An expert system for the conceptual design of bridges. Computers and Structures, 40(1), 101-105.
Priestley, M.N., Seible, F., and Calvi, G.M. (1996) Seismic design and retrofit of bridges, California.
Mander, J.B., Priestley, M.J.N., and Park, R. (1988) Theoretical stress strain model for confined concrete. Journal of Structural Engineering, 114(8), 1804-1826.
Menegotto, M. and Pinto, P.E. (1973) Method of analysis for cyclically loaded R.C. plane frames including changes in geometry and non-elastic behaviour of elements under combined normal force and bending. IABSE Symposium on Resistance and Ultimate Deformability of Structures Acted on by Well-Defined Repeated Loads, 15-22.