Date of Award

May 2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Engineering

First Advisor

Sam Helwany

Committee Members

Al Ghorbanpoor, Konstantin Sobolev, Istvan Lauko, Bruce Ramme

Keywords

Abutments, Bridges, CLSM, Full-scale Test, Pull-out Test, Rapid Construction

Abstract

The required time for building bridge abutments is one of the key obstacles facing rapid bridge construction. For typical span bridges, this can be remedied by using Controlled Low Strength Materials (CLSM) as backfill materials placed behind full-height precast concrete panels that are integrated with the CLSM backfill via steel anchors. CLSM bridge abutments can be constructed in a short time as they do not require heavy machinery for excavation, compaction, and piling equipment. The main objective of this study was to examine the behavior of an instrumented laboratory large-scale CLSM bridge abutment with full-height precast concrete panels that was subjected to a monotonically increasing sill (foundation) pressure. The experiment showed that the CLSM bridge abutment, with a relatively short cure time of 7 days, is capable of carrying typical bridge loads with a reasonably large safety margin, and with minimal deformations.

To select a suitable CLSM mixture proportion, several mixtures were developed and tested in the laboratory for engineering properties including flowability, density, compressive strength and stress-strain behavior. The main performance criteria for selection of a potential CLSM mixture were compressive strength to support the bridge loads, excavatability and flowability to fill the entire abutment in one continuous pour. Since it was a critical area of concern in design of the CLSM bridge abutment, the bond strength performance of the CLSM to steel anchors was also investigated. In pullout tests, a CLSM mixture with higher compressive strength resulted in higher bond strength and more brittle slippage. A numerical simulation of pullout tests indicated that the bond strength decreases with increase in bar size and embedment length.

Finite element method (FEM) of analysis was implemented to simulate and explore the performance of CLSM bridge abutments based on bearing pressure capacity, displacements, and the developed axial force in anchors, and to provide an assessment of safety of the design. The accuracy of the finite element results for the response and failure behavior of a CLSM mass was evaluated by a comparison with the experimental results. Good agreement was obtained between the numerical and experimental results. The validated finite element (FE) model was then used for conducting a series of parametric studies to define the effects of CLSM compressive strength, curing age, environment temperature and construction details on response of the abutments. It was also learned that the computed and measured lateral displacements for the facing panels were negligible up to about 70% of the bearing pressure capacity of the abutment when a longitudinal crack developed in the CLSM backfill close to the facing wall.

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