ABSTRACT
The daily and seasonal temperature changes result in imposition of cyclic horizontal displacements on the continuous bridge deck of integral bridges and thus on the abutments, backfill soil, steel H-piles, and cycle control joints at the ends of the approach slabs. Due to these seasonal temperature changes the abutments are pushed against the approach fill and then pulled away, causing lateral deflections at the tops of the piles that support the bridge as observed from Fig. 1 (French et al. 2004). The magnitude of these cyclic displacements is a function of the level of temperature variation, type of the superstructure material and the length of the bridge. As the length of the integral bridges gets longer, the temperature-induced cyclic displacements and forces in steel H-piles components may become larger as well. This may result in the reduction of their service life due to low-cycle fatigue effects (Dicleli & Albhaisi 2003, Arsoy et al. 2004). Lateral deflections at the tops of the piles. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig272_1.tif"/>
In this study, the field measurements obtained for integral bridges are used to determine the amplitude and the number of temperature induced cycles on steel H-piles in integral bridges. Using the obtained measurements, the number of large strain cycles per year due to seasonal temperature changes and the number and relative amplitude (relative to the amplitude of large displacement/strain cycles, i.e. β = small strain cycle amplitude/large strain cycles amplitude) of small strain cycles per year due to daily or weekly temperature changes are determined. Additionally, the number of small cycles (secondary cycles) between the maximum and minimum cycle above and/or under the large strain is counted. Using the available data on the number and amplitude of temperature induced displacement-strain cycles, a new cycle counting method is developed to determine the number and amplitude of large and small displacement/strain cycles (small strain cycles are composed of primary and secondary strain cycles). Then, a new equation is obtained to determine a displacement/strain cycle amplitude representative of a number of small amplitude cycles (primary and secondary) existing in a typical temperature induced displacement/strain history in steel H-piles of integral bridges.
It is found that, the secondary strain cycles have a negligible effect on low cycle fatigue life of steel H piles in integral bridges.
