Low-cycle fatigue performance of steel h-piles in integral bridges

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2014
Karalar, Memduh
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Integral bridges are jointless bridges where the superstructure is connected monolithically with the abutments. Due to seasonal temperature changes the abutments are pushed against the approach fill and then pulled away, causing lateral displacements at the top of the piles that support the abutments. This may result in the reduction of their service life due to low-cycle fatigue effects. In this research, both analytical and experimental studies are conducted to investigate the effect of thermal induced cyclic displacements/strains on the low cycle fatigue performance of steel H-piles at the abutments of integral bridges. First, a new cycle counting method is developed to determine the number and amplitude of large and small pile displacement/strain cycles due to seasonal and daily temperature fluctuations. Then, a new equation is developed to determine a displacement/strain cycle amplitude representative of a combination of a number of small and large amplitude cycles existing in a typical temperature induced displacement/strain history in steel H-piles of integral bridges. Then, nonlinear finite element models (FEMs) of the steel H-pile specimens used in the experimental part of this research study are developed using the computer program ANSYS. Next, FEM of these test specimens are subjected to a loading similar to that is used in the experimental testing. The main purpose of conducting such nonlinear analyses is to identify potential problems that may be encountered during testing and to improve the test apparatus if necessary. Low cycle fatigue tests are then conducted to investigate the fatigue life of steel H-piles subjected to thermal induced cyclic strains/displacements. The tests are designed to study the effect of several parameters, namely; (i) pile size (ii) equivalent length of the pile, (iii) orientation of the pile (strong axis or weak axis bending), (iv) small amplitude cycles (displacement history with and without small amplitude cycles), iv) amplitude of the small displacement/strain cycles with respect to that of large displacement/strain cycles and (vi) the magnitude of the axial load applied on the pile. Furthermore, nonlinear FEMs of the steel H-pile specimens are developed using the program ANSYS to numerically predict their low cycle fatigue performance under cyclic thermal induced displacements/strains. .
Bridges, Bridges, Piling (Civil engineering)., Steel
http://etd.lib.metu.edu.tr/upload/12618008/index.pdf
https://hdl.handle.net/11511/23914
Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats
M. Karalar, “Low-cycle fatigue performance of steel h-piles in integral bridges,” Ph.D. - Doctoral Program, Middle East Technical University, 2014.
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