ABSTRACT
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 as shown in Fig. 1. This may result in the reduction of their service life due to low-cycle fatigue effects. Although bridge engineers (Dicleli, 2000, French et al. 2004) have already predicted that low cycle fatigue may occur in the steel H piles of integral bridges due to thermal effects, only a few research studies and experimental test results have been found on this topic in the literature. Pile displacement due to thermal changes, (a) Thermal Expansion, (b) Thermal contraction. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig273_1.tif"/>
The main design resource for civil engineers, the American Association of State Highway and Transportation Official, explains the importance of the fatigue issue in structures only, but does not provide any guidelines for fatigue design and its consideration in the steel pile of integral bridges. As the length of integral bridges increases, the temperature-induced lateral cyclic displacements in the steel H-piles at the abutments become larger as well. As a result, the piles may experience cyclic plastic deformations. This may result in the reduction of their service life due to low-cycle fatigue effects. Thus, it is necessary to exactly understand the behaviour of piles under cyclic lateral loads and determine the most likely locations for crack initiation and propagation. However, in many cases these piles are covered with soil and it is very difficult to find the cracks in those locations. Thus, experimental measurements are often too expensive and time-consuming especially when integral bridge components (abutment, pile, etc.) are subjected to long arbitrary multi-axial cyclic loading histories in service life.
To avoid the huge cost and testing time required for conducting experimental tests, researchers often use some forms of FE analysis to carry out their research. FE analysis predictions have been widely used for evaluating the different models used for low cycle fatigue performance. In this study, 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. Furthermore, the aim is also to make a correlation and calibration between finite element models and experimental test results of the thermal induced cyclic displacements/strains on the low cycle fatigue performance of steel H-piles at the abutments of integral bridges.
