Integral bridge abutment and backfill behaviour
type: CreativeWork
description: Integral bridges do not contain the bearings or expansion joints found in conventional bridges. Interaction between the abutments and backfill due to thermal movements of the bridge deck leads to the accumulation of soil strain — known as strain ratcheting — which results in increased lateral earth pressures along with settlement at the bridge approach. Uncertainty surrounding strain ratcheting is reflected through design restrictions. This research investigated strain ratcheting and ways it can be limited through smarter design. Geotechnical centrifuge modelling was the main research method used in this project. The reference configuration consisted of a full-height abutment atop a spread footing, supported on and retaining a dense granular sand, with thermal cycles simulated at the deck level using a high precision mechanical actuation system. The actuator was developed for this project, operating in displacement control and capable of applying a 12 kN force in 25 µm increments. The standard loading pattern simulated 120 cycles of ±20 mm representing seasonal thermal movements of a 150 m long concrete bridge over its design life, compliant with the UK design document PD 6694-1 (BSI, 2020). Sensors included an LVDT and load cell measuring applied movement and axial force in the bridge deck, strain gauges to capture abutment bending moments, a Tekscan sensor measuring lateral earth pressures, and a camera to track soil and structural movements. A total of seven tests were carried out with alterations made to the thermal loading, abutment stiffness, backfill density, and backfill constitution. Four tests were initially compared to investigate the mechanisms driving strain ratcheting, in which the behaviour under different cycle magnitudes, backfill densities, and loading histories was considered. Strain ratcheting was found to be dependent upon densification and dilation within the backfill, driven by settlement at the backfill-abutment interface. A similar developme…
abstract: Integral bridges do not contain the bearings or expansion joints found in conventional bridges. Interaction between the abutments and backfill due to thermal movements of the bridge deck leads to the accumulation of soil strain — known as strain ratcheting — which results in increased lateral earth pressures along with settlement at the bridge approach. Uncertainty surrounding strain ratcheting is reflected through design restrictions. This research investigated strain ratcheting and ways it can be limited through smarter design. Geotechnical centrifuge modelling was the main research method used in this project. The reference configuration consisted of a full-height abutment atop a spread footing, supported on and retaining a dense granular sand, with thermal cycles simulated at the deck level using a high precision mechanical actuation system. The actuator was developed for this project, operating in displacement control and capable of applying a 12 kN force in 25 µm increments. The standard loading pattern simulated 120 cycles of ±20 mm representing seasonal thermal movements of a 150 m long concrete bridge over its design life, compliant with the UK design document PD 6694-1 (BSI, 2020). Sensors included an LVDT and load cell measuring applied movement and axial force in the bridge deck, strain gauges to capture abutment bending moments, a Tekscan sensor measuring lateral earth pressures, and a camera to track soil and structural movements. A total of seven tests were carried out with alterations made to the thermal loading, abutment stiffness, backfill density, and backfill constitution. Four tests were initially compared to investigate the mechanisms driving strain ratcheting, in which the behaviour under different cycle magnitudes, backfill densities, and loading histories was considered. Strain ratcheting was found to be dependent upon densification and dilation within the backfill, driven by settlement at the backfill-abutment interface. A similar developme…
author: Morley, Douglas
language: eng
keywords: Integral bridge, Strain ratcheting, Centrifuge modelling, Field monitoring
license: https://www.repository.cam.ac.uk/bitstreams/97ce0d6b-ad82-4dd9-a8de-21cb331a94d5/download
license: http://purl.org/NET/rdflicense/allrightsreserved
date published: 2025-10-19
date modified: 2026-07-22T22:24:28Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.124967