Degree

Doctor of Philosophy (PhD)

Department

Civil Engineering

Document Type

Dissertation

Abstract

Link slabs in bridges can be a cost-effective solution to increase the service life of bridge structures. The partial continuity condition in link slab bridges, however can be challenging to quantify. In this work link slab performance is studied by means of a parametric study, a long-term Structural Health Monitoring (SHM) System, and a detailed finite-element model.

The parametric study was conducted using mathematical and a two-dimensional (2D) finite element model. The study considers bridge design factors such as number of spans, span length, span length ratio, girder separation, and temperature settings, in conjunction with the corresponding girder and support characteristics to explore the relationship between the different factors that affect link slab performance, as well as develop a simplified expression to represent Link Slab behavior within a system. The effects of live load and temperature gradient were taken into account during the analysis and bearing pad support design recommendations were made.

A long-term behavior of a newly constructed bridge was also investigated. Data from a SHM system installed on the Ouachita River Bridge was used to assess the performance of link slabs under varying continuity and support conditions. The performance of the bridge was assessed under live load, temperature gradient and uniform temperature loading conditions. Cracking of the link slab was observed regardless of whether crack control grooves existed or not. It was found that the link slab force are directly affected by link slab cracking. By comparing link slab forces from field data and from a 2D line model, it was found that support conditions are the major factor affecting the magnitude the link slab forces, and hence its performance. Therefore, special attention should be given to bearing pad design under link slabs and to avoid unintentional locking at these location (e.g. due to debris accumulation).

A detailed three-dimensional (3D) finite element model was also developed using commercial software package ANSYS to better understand the force transfer mechanism and interactions between the link slabs, the girders and the supports. The results from these analyses contribute toward having a much better understanding of link slab performance, as well as the aspects of bridge design that are affected by the presence of a link slab. The 3D model showed that bearing pads are subjected to higher demands in partially continuous bridges (link slabs) in comparison to fully continuous bridges.

Date

8-1-2019

Committee Chair

Okeil, Ayman

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