Page 158 - Bridge and Highway Structure Rehabilitation and Repair

4 Section Overview

• Developments in theory,
design, rating, and
An Analytical code methods used in
computer software.
• Strength and
Approach to serviceability methods
for structural evaluation
and rating, which form
the basis for repair and
resonstruction.
Fracture and • AASHTO load
combinations for live
loads and extreme
Failure conditions are extended
to construction
conditions.

4.1 THEORETICAL CONCEPTS USED IN DEVELOPING
COMPUTER SOFTWARE
4.1.1 Analysis for Engineering Maintenance

One of the continuous duties of an engineer is maintenance. Maintenance
is not just patching concrete. It includes preventing failure by managing,
disciplining, and applying structural mechanics to the structural domain of
bridge components, made up of single or composite materials.
Chapter 3 covered reasons for failure. It is important to understand both
the mechanics/mechanisms behind a failure and the applicable theory of
yielding and fracture so that future designs can be made safer. Retrofi t of
bridge components, widening or replacement usually require use of computer Strengthening and Repair Work
software. Theories of both elasticity and plasticity are required to understand
the behavior of a bridge or a given member. In general, at failure nonlinear Section 2
behavior due to large deformations or due to formation of plastic hinges
(nonlinear stress) will take place.
In this chapter, facilitated computer-based analysis based on understanding
of the component behavior. In addition the review of fundamental concepts,
finer points in analysis such as arching action in deck slabs, theories of yield-

ing of steel (due to Tresca and Von Mises), modified compression fi eld theory
(MCFT), and simplified bending and shear formulae under moving loads for

single span girders are addressed. It will be noted that the more accurate the
analytical methods, besides safety, the greater the economy in design.
Hand calculations are kept to a minimum since in the design offi ce the
culture of obtaining numerical solutions is shifted to software usage.

4.1.2 Diagnostic and Preservation Approach to Analysis

Criteria for effective performance can best be satisfied by a diagnostic
and preservation approach. All diagnostic or preservation design is based on
analysis of the deficient structure and the remodeled or rehabilitated structures.

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