Design of Steel Tied Arch Bridges

98 Pages·2010·11.77 MB·English

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AN ALThRNATI VI:;
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By Dann H. Hall' and A. Rlchard LaWln'
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Far American Institute Of Steel CalstructlOO
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I July '985
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, Bri<i3e SOftware Del/elopnent International Ltd.
Coo[ersl:urg, Pennsy ll/ania
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TABLE OF CINl'ENl'S
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1.0 SlMlARY 1
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1 .1 Introduction
1.2 Problem statement
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1.3 Objective
1.4 AWroach
I 1.5 Alternate ~thod
2.0 INTOOOOCl'IGl 5
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2.1 Present Practice
2.2 Problems With Present Practice
I 2.3 Proposed Alternate ~thod
2.3.1 General
2.3.2 Erection of the Arch Ribs
2.3.3 Erection of Deck Units
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2.3.4 Jldvantages of Alternate ~thod
3.0 DESIQI EXAMPLE BY ALTffiNATE ME:llICD 17
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3.1 General
3.2 Design Considerations
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3.2.1 Live Load
3.2.2 Dead Wad
3.2.3 Construction Loads
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3.2.4 'lhermal Wad
3.2.5 Post Tensioning
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4.0 Analysis Using Finite Element Models 25
I 4.1 General
4.2 Floor Beam
4.3 Placement of Deck Units
I 4.3.1 Arch Rib
4.3.2 Hangers and Dead Wad Tie Cable
4.3.3 Precast Deck Units
I 4.3.4 Bearings
4.3.5 Procedure
I 4.4 Integrated Model
4.4.1 General
4.4.2 Tie Beam
I 4.4.3 Deck
4.4.4 Floor Beams
4.4.5 Procedure
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5.0 RESULTS 38
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5.1 General
5.2 Floor Beam
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5.3 Arch Ribs
5.3.1 General
5.3.2 Deck Unit Staging
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5.3.3 Superimposed Dead Load
5.3.4 Temperature
5.3.5 Live Load
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5.4 HarY:Jers
5.4.1 General
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5.4.2 Deck Unit staging
5.4.3 Superimposed Dead Load
5.4.4 Temperature
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5.4.5 Live Load
I 5.5 Dead Load Tie Cable and Reactions
5.5.1 General
5.5.2 Deck Unit staging
I 5.5.3 Superimposed Dead Load
5.5.4 Temperature
5.5.5 Live Load
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5.6 Tie Beams
5.6.1 General
I 5.6.2 Deck Unit Staging
5.6.3 Superimposed Dead Load
5.6.4 Temperature
I 5.6.5 Live Load
5.7 Deck
I 5.7.1 General
5.7.2 Deck Unit Staging
5.7.3 Superimposed Dead Load
I 5.7.4 Temperature
5.7.5 Live Load
I 5.8 Post Tensioning
5.8.1 General
5.8.2 Deck
I 5.8.3 Tie Beam
6.0 CIN:llJSlOOS 86
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7.0~
I 8.0 BIBLI(X;RAPHY 89
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LIST OF FIQJRES
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FIGURE TITLE
2.1 Typical Tied Arch Brici3e
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2.2 Alternate Design - Deck am Tie Beam Unit
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2. 3MB Alternate Design - Arch Erection Schemes
2.4 Dead Load Tie cable Anchorage
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2.5 Erection Schane for Deck Units
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2.6 Deck Unit layout
2.7 Arch Rib to Tie Beam Detail
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3.1 Design Study Example
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3.2 Design Study Arch Rib Cross Section
3.3 Design Study Deck Unit
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3.4 Design Study Deck Cross section
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4.1 Floor Beam am Deck /ot:ldel
4.2 Arch Rib am Staging /ot:ldel
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4.3MB Staging sequence - Stage 2 - Stage 3
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4.4 Integrated /ot:ldel - Overview
4.5 Integrated /ot:ldel - Details
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5.1 Floor Beam M:rnent Envelope
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5.2 Floor Beam Shear Envelope
5.3 Floor Beam Elevation
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5.4 Floor Beam Influence Line
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5.5 Accumulated M:rnents in Arch Rib D.le to
Deck Units
5.6 Accumulated 'll1rusts in Arch Rib D.le to
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Deck Units
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LISI' OF FIGJRES (O:xltinued)
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FIGURE TITLE
5.7 Stress Envelopes in Arch Rib DJe to
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Deck Units
5.8 Dead Load ~ts in Tie Beam
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5.9 Locatioo of Recorded Deck stresses
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5.10 stresses in top of Deck DJe to Superimp:>sed Dead
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Load 'l'e!1;lera ture - Design 1
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5.11 Stresses in top of Deck DJe to Superimp:>sed Dead
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Load 'l'err{lerature - Design 2
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5.12 Stresses in bottan of Deck DJe to Superimposed Dead
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Load 'l'e!1;lerature - DeSign 2
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LIST CF TABUS
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TABLE TITLE
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3.1 Design Example CCInparison
4.1 M:ldel Explanation for Fig 5
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5.1 Dead Load M:Inents in Arch Rib lAJe to Deck Units
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5.2 Dead Load Thrusts in Arch Rib lAJe to Deck Units
5.3 Accunulated M:Inents in Arch Rib !Ale to Deck Units
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5.4 AccuIlulated Thrusts in Arch Rib lAJe to Deck Units
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5.5 Accunulated Stresses in Arch Rib !Ale to Deck Units
5.6 SUmnary of Arch Rib /obrents
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5.7 S\mnary of Arch Rib Thrusts
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5.8 Factored /obrents in Arch Rib
5.9 Factored Thrusts in Arch Rib
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5.10 SUmnary of stresses in Arch Rib
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5.11 Hanger Forces for Dead Load
5.12 AccuIlulated Forces in Hangers for Dead Load
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5.13 SUmnary of Forces in Hangers
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5.14 Reaction and Tie cable Forces
I 5.15 Tie Beam stresses at Hanger - Design 1
5.16 Tie Beam Stresses at Hanger - Design 2
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5.17 Tie Beam stresses Between Hangers - Design 2
I 5.18 Deck Stresses Top Line "A"
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LIST OF TABLES (Ccntirued)
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TITLE
5.19 Deck stresses Botton Line "A"
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5.20 Deck stresses Top Line "B"
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5.21 Deck Stresses Botton Line "B"
I 5.22 Deck stresses Top Line "C"
5.23 Deck stresses Botton Line "C"
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1.0 Stmnary
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1 .1 Introduction
I '!he tied arch brici:Je is canposed of an arch rib 00 each side
of the roadway, a tie beam associated with each arch rib which
takes the thrust fran the arches arrl a deck system supported
by the tie beams. The deck system is most <X1i11ccl.y canposed
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of a concrete deck supported by lo~itudinal str~ers in turn
supported by transverse floor beams. Cable ~ers cconected
I between the arch ribs arrl the tie beams transfer the vertical
loads fran the tie beams to the arch ribs. Thus traffic passes
between the arches at the lowest elevation of the arch ribs.
I Usually the arches are parabolic arrl braced overhead for
stability.
1 Thrust fran the arch ribs is resisted by the tie beams.
'!he deck system is isolated fran the tie beams to insure that
tensile stresses are not introduced into the deck when the tensioo
I in the tie beam increases. This is dooe by segmen~ the deck
using stress relief joints. Lateral loads are carried by a brac~
system which works with the tie beams. It is <X1i1'O' to construct
I brac~ at both top and bottan flange levels of the floor beams.
The arch ribs principally resist thrust; rut bending <X1iip:uents
I can be rather large. If the arch ribs are loaded evenly, the
berrling is minimized. Berrling in the arch rib is reduced for
a given concentrated load if stiffness of the tie beam is increased.
I This is most easily envisioned by thinking of the tie beam as
a beam on elastic foundations, i.e. the ~ers and arch ribs
act as the foundatioos. The stiffer the tie beam, the !lOre evenly
I distriruted is the force in the This leads to !lOre
~ers.
even loadi~ of the arch ribs. Since the deck has been structurally
isolated fran the tie beams, neither it nor the lo~itudinal
I stringers cootriOOte stiffness to the tie beams.
'!he structures are ruilt fran falsework. Spans range between
I 200 arrl 1000 feet for this type of brici:Je. They are used where
single spans are required. If cootinuity fran adjacent spans
is available, tied arches are at a disadvantage canpared to cooti
I nuous trusses, cable stayed or even girder brici:Jes.
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1 .2 Problan Statement
Tied arch bridJes have becane less p::lpular because the tie I
beams are cx:nsidered n::lI'l-redurrlant. AASID'O BridJe Specifications
define a n::lI'l-redundant member as a tension member which, if it
fails, is likely to lead to collapse of the structure. Although I
few, if any, tied arch bridJes have actually failed, the tie
girders have suffered cracks in one or two instances (Ref,2).
It is clear that failure of such a member could be catastrophic. I
Further, the cost of tied arch bridJes is high when canpared
to more modem bridges such as the cable stayed bridge and the
segmental cx:ncrete box girder bridJe. I
There are several reason assigned to the high cost:
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o 'lbere are teo many parts in tied arches;
o Field labor is expensive; I
o '!be deck does not work with other CXl1ifXll,ents in
the bridJe; I
o '!be stress relief joints in the deck are
expensive; I
o Ncn-redundant members are defined as fracture
cri tical and must be designed and manufactured to I
more stringent requiranents;
o Falsework is often not needed on other types I
of bridJes.
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1.3 Objective
'!be objective of this study is to examine other p:lssible I
means of constructing a tied arch bridge using modem techniques
that WOlld reduce or eliminate the undesirable 11Cl1-redundant
members, nake the structure less expensive to cx:nstruct; nake I
more of the CXl1ifXll,ents work efficiently, eliminate as many of
the pieces of the structure as possible and to reduce the amount
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of field labor, particularly, the elimination of falsework.
Several enabling technologies have been developed over the
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last decade that are believed to meet the above objectives.
First was the advent of inexpensive high speed electrcnic
cx:mputers which pennit the examination of structural behavior
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in detail that was not eccnanical in the past.
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