An Investigation of Sources of Asymmetric Thermal Expansion Behavior in Semi-Integral Bridges

The typically poor long-term performance of deck expansion joints and the high cost of maintenance of these bridge components have led to an increased utilization of jointless bridge systems such as integral and semi-integral bridges. However, the elimination of expansion joints leads to some adverse secondary effects due to the cyclic interaction of the bridge with the abutments. This soil-structure interaction can cause gradual settlement of the backfill, backfill earth pressure increase, and lateral loading of the foundations. In addition to these issues, it has been observed that integral and semi-integral bridges do not necessarily experience the symmetrical thermal expansion and contraction that is typically assumed in design, even if the structure appears symmetrical in design. As a result, jointless bridges may expand more toward one abutment than the other in response to daily and seasonal changes in temperature. In this paper, some of the potential causes of the asymmetrical expansion of integral and semi-integral bridges are identified and discussed through analysis of some of the past field monitoring data as well as the available data published in literature. The identified causes include minor differences in foundation soil stiffness, depth of the foundation, environmental forces, and more.