Civil MDC

2020, Concrete Segmental Bridges: Theory, Design, and Construction to AASHTO LRFD Specifications by Dongzhou Huang, Bo Hu

Segmental concrete bridges have become a preferred choice for major transportation projects
throughout the world because they meet the prevailing need for expedited construction with minimal
traffc disruption, lower life cycle costs, appealing aesthetics, and the adaptability to accommodate
curved roadway alignments. Although there is an abundance of literature pertaining to the
design and construction of concrete segmental bridges, most of it is focused on construction and
is directed toward experienced concrete segmental bridge designers. However, it is important for
bridge engineers and university seniors with little or no experience in designing complex segmental
bridges to have a comprehensive, well-written book that can be used as a reference tool for both
design and for self-study. This book is intended to assist all levels of practicing bridge engineers and
university seniors in fully understanding concrete segmental bridge design techniques, analytical
methods, design specifcations, theory, construction methods, and common industry practices. It
presents comprehensive design theories, practical analysis, and key construction methods used for
segmental bridge design in a systematic, easy-to-follow manner while highlighting the importance
of key design checks. The design principles presented are further reinforced with a design example
based on the AASHTO LRFD design specifcations for each of the main segmental bridge types.
The examples encompass both hand solutions as well as computer modeling techniques that are
currently used in practice.

Chapter 1 is intended to familiarize readers with the basic concepts needed to design concrete
segmental bridges. First, the types of materials and their mechanical properties used in concrete
segmental bridges are introduced. Then, the basic components, the types of concrete segmental
bridges, and their typical construction methods are briefy discussed. At the end of this chapter,
the selection of different types of segmental bridges, bridge general design procedures, and bridge
aesthetics are discussed.
It is especially useful for bridge designers to clearly understand bridge design philosophy, types
and magnitudes of bridge loadings, and the safety and reliability characteristics required during
the service life of a bridge. In Chapter 2, the different types of highway bridge design loadings and
their analytical methods are introduced. Then, the basic theoretical background of the AASHTO
LRFD method is discussed. Finally, design limits, load combinations, load, and resistance factors
are presented.
Though bridge designers are formally trained in the theories of structural design and analysis, it
requires considerable knowledge and skill to recall, utilize, and implement these theories in bridge
design. For this reason, Chapter 3 frst presents the basic theory of prestressing concrete structures
and the design theories of bending, shear, torsion, and compression. Then, the current AASHTO
design equations are briefy presented and interpreted.

Concrete segmental bridges are generally statically indeterminate structures, and their analytical
methods are less familiar to bridge engineers than those of simply supported bridges. To help
readers fully understand the design theory and behavior of concrete segmental bridges, detailed
bridge analytical theories are given in Chapter 4. First, the basic analytical theory of indeterminate
structures is briefy reviewed. Then, the longitudinal analysis of segmental bridges is discussed,
including secondary forces due to post-tensioning, temperature, support deformation, shrinkage,
and creep. Finally, the transverse analysis of segmental box girder bridges is presented.
The design of span-by-span concrete segmental bridges is discussed in Chapter 5. The common
details, elements, and analytical methods of concrete segmental bridges are presented, including the
different types of segments, tendon layouts, diaphragms, as well as blister design and analysis. At
the end of the chapter, a design example is given that is generated based on an existing segmental
bridge. It is recommended that this chapter be understood prior to reading about the design of other
types of segmental bridges.

In Chapter 6, the design of balanced cantilever segmental bridges is presented. The distinguishing
design characteristics and details of this type of bridge are frst presented. Then, the design theory
and detailing of curved segmental bridges are discussed. At the end of the chapter, an example
of a balanced cantilever segmental bridge design based on an existing bridge is provided.
Designs of incrementally launched segmental bridges, post-tensioned spliced girder bridges,
arch bridges, cable-stayed bridges, and substructures are addressed in Chapters 7, 8, 9, 10, and 11,
respectively. In each of these chapters, the distinguishing design theories, details, and behaviors
of each individual bridge type are presented. For each type of bridge and substructure, a design
example is generated based on an existing bridge.
In Chapter 12, some typical construction methods in concrete segmental bridge construction
are presented. These include typical segment cast methods, geometrical control, construction tolerances,
and post-tensioning tendon installation and grouting.
The AASHTO LRFD Bridge Design Specifcations, 7th edition, 2014, is used throughout the text
as the design code. The English system of measuring units used in the book is consistent with the
code and the bridge building industry in the United States. For the convenience of those accustomed
to the metric system, a table, “Unit Conversion Factors for English and Metric Units,” is provided.
Because of the tremendous work effort involved in writing this book, I invited my colleague
Dr. Bo Hu, Ph.D., P.E., P.Eng., to be a co-author to fnish this book. I wrote Chapters 1 to 11 and
part of Chapter 12, while Dr. Hu wrote part of Chapter 12, performed literature reviews, and drew
most of the fnal fgures contained in this book.

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