A Case Study of the Retrofitting of the Great Fish River Bridge

Nerave Moodley,Graham Moore,David Wylie,M.G Alexander,H Beushausen,P Moyo,F Dehn

doi:10.1051/matecconf/201819910006

Abstract

In developing countries and economies such as South Africa, retrofitting is a vital tool to maximise and extend the service life of existing infrastructure. The transportation sector plays a pivotal role in stimulating economic growth, and retrofitting existing bridges to meet the growing capacity needs of South Africa’s roads supports continued economic growth and development. This paper outlines the technical and practical challenges encountered and the solutions developed by the design team to retrofit the existing 215 m long, 9-span, Great Fish River Bridge in the Eastern Cape of South Africa. These challenges included jacking up the existing bridge under traffic loading to replace 108 existing bearings and erecting 32.5t precast beams at heights of 10.5m above a major river whilst accommodating high volumes of traffic on a busy National road.

Highlights

The existing 215m long, 9-span, bridge was constructed in 1959 and spans the width of the river valley
The existing superstructure comprises prestressed, precast I-beams with an in-situ deck slab, supported on concrete hinge bearings resting on reinforced concrete wall-type piers and reinforced concrete abutments
The South African National Road Agency Limited (SANRAL), as the owner of the structure commissioned an upgrade to Section 13 of the N2 which included the retrofitting of this bridge

Summary

Introduction

The existing 215m long, 9-span, bridge was constructed in 1959 and spans the width of the river valley. The superstructure is 10.5m above the river and is located at km 103.5 along Section 13 of the N2 between Peddie and Grahamstown in the Eastern Cape of South Africa. It is constructed on an S-bend curve with supports at skews varying between 25° and 30°. WBHO was the appointed contractor responsible for the construction of the first phase of this project, which included the widening of this bridge. Mott MacDonald Africa (Pty) Ltd, in a joint venture with Bosch Holdings were the consulting engineers appointed for the design and construction monitoring of the widening of this bridge

Concept Design

Construction Challenges

Jacking and Existing Bearing Replacement

Beam Manufacture and Erection

Findings

Conclusion