Page 306 - Bridge and Highway Structure Rehabilitation and Repair

7

Bridge Widening

and Deck

Replacement

Strategy

7.1 SELECTING BRIDGE WIDENING OR REPLACEMENT
7.1.1 Introduction
In Chapter 2 the five types of rehabilitation were discussed. Rehabilitation

may require continued maintenance and high cost since the greater the number
of bridges selected for repair, the greater the investment by the responsible
agency. Besides rehabilitation, only widening, widening with repair and

retrofit, and full or partial replacement are the other options. In this chapter, Strengthening and Repair Work

selection of either widening or widening with a retrofit or replacement method
are discussed. The procedures for superstructure and substructure replacement
are based on alternatives analysis and evaluation of life cycle costs. Section 2
Widening entails retaining and reconstructing an existing bridge. It gives
the bridge a new function and would cost only a fraction of the cost of a new
bridge. Over decades, demographic changes have increased the ADTT on
many important routes. To meet the growing traffic needs, both approach

highways and bridges need to be widened. One or more traffic lanes, shoulders

and/or sidewalks may be needed. Symmetric widening is not always possible
but preferred. Providing continuity over piers for the widened deck area and
new girders may not be easy due to lack of continuity over supports in the
original design. Resulting widening of abutments, piers, and their foundations
are unavoidable.
Major widening is new construction work for an existing bridge facility,
which may nearly double the deck area of the existing bridge and increases
the number of traffic lanes. It may be widening an existing substandard lane

width, or adding overhangs or sidewalks. In each case, the widened area to be
constructed is the transverse out-to-out dimension of the proposed deck.

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