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Published byAgatha York Modified over 9 years ago
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Design and Rating for Curved Steel I- and box-girder Bridge Structures
C. C. Fu, Ph.D., P.E. the BEST Center Department of Civil Engineering University of Maryland June 2003
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Approximate Analysis Method
Bridge deck Live load distribution factor Effective flange width(shear lag) Live load influence line Software package
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Refined Analysis Methods
Grillage analogy method Orthotropic plate method Articulated plate method Finite strip method Finite element method Software package
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DESCUS - I & II Design, Analysis & Rating of Curved Steel
I-Girder and Box-Girder Bridge System
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DESCUS I & II Development
Began in 1976 & 1980, respectively Microcomputer version (DOS) with graphic interface in 1988 used in numerous projects by FHWA, state agencies & consulting firms SI & Rating version in 1994 WINDOWS, WINDOWS/NT & Network version in 1997 LRFD live loading version in 1998 New AASHTO Guide Specifications in 2003 Future; including LRFD curved bridge code
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DESCUS-I Banner Page
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DESCUS-I Input Utility
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DESCUS-II Input Utility
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DESCUS AutoMESH Utility
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DESCUS-I Input for Example
= 0 If no shear connector in M-; = 1 If shear connector and rebar in M-, but no composite action in the analysis = 2 If shear connector and rebar in M-, plus composite action in the analysis
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DESCUS-I Input for Example
Zr, based on the number of cycles
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DESCUS-I Input for Example
IMPORTANT: For rating with non-AASHTO truck, ‘1’ to separate AASHTO and non-AASHTO loadings is required
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DESCUS-I Input for Example
If shear connector option =1 or 2, rebar in the M- is considered
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DESCUS-I AutoDF Input for Example
=0 Loading every lane width for no. of lane trucks; =1 Loading within the design lanes for no. of lane trucks;
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DESCUS-I AutoDF Input for Example
Wheel fraction is used for the consideration of centrifugal force and superelevation effects
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DESCUS-I Input for Example
Haunch will affect the section properties and weight Detailed factor applied to steel section only
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DESCUS-I Input for Example
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DESCUS-I Input for Example
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DESCUS-I Input for Example
HS loading can be from 1 to 99 If =2 proportional to the HS loading For fatigue use
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DESCUS-I Example
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DESCUS-I Example
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DESCUS-I Input for Example
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DESCUS-I Input for Example
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DESCUS-I Example Graphs
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DESCUS-I Input for Example
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DESCUS-I Input for Example
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DESCUS-I Input for Example
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DESCUS AutoDF Utility
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DESCUS Print & Graphic Utilities
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DESCUS-STAGE
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DESCUS-STAGE
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Flowchart for the Curved Steel Bridge Design and Load Rating
Geometry & Loading Data Input DESCUS Preprocessor Revise Graphic Verification DESCUSPRE DL & SDL Application LL Influence Surface Generation DESCUS Main processor LL Application by Inf. Surface 6 infl. Files Stress Allowables Load Rating
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DESCUS-I Example Problem Framing Plan
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DESCUS-I Moment Influence Lines for Joint 3 of Girder 2
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DSCUS-I Moment Influence Lines for Joint 6 of Girder 2
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Placement of Live Load on Influence Surface
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Components of Normal Stresses
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Load Factor Design (LFD) & Load & Resistance Factor Design (LRFD)
2A Compact Section 2A.a - For compression flange braced by cross-frames or diaphragms, fb Fbu (Eq. 5) 2A.b - For tension flange or compression top flange within hardened concrete fb Fy (Eq. 6)
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LFD/LRFD (cont.) 2B. Noncompact Section
2B.a - For compression flange braced by cross- frames or diaphragms, fb Fby (Eq. 7) & fb + fw Fy (Eq. 8) 2B.b - For compression top flange within hardened concrete, fb + (fw)DL Fy (Eq. 9) 2B.c - For tension flange, fb + fw Fy (Eq. 10)
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2003 New Load Factor Design (LFD) & Load & Resistance Factor Design (LRFD)
For compact compression flange braced by cross-frames or diaphragms, fb Fcr1 or Fcr2 (Eq. 5-4 & 5-5) For non-compact compression flange braced by cross- frames or diaphragms, fb Fcr1 or Fcr2 (Eq. 5-8 & 5-9)
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2003 New LFD/LRFD (cont.) 5.3 - For partially braced tension flange braced by cross- frames or diaphragms, fb Fcr1 or Fcr2 (Eq & 5-11) 5.4 - For continuously braced tension flange encased in concrete, fb Fcr = Fy
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Rating for Curved Steel Bridges
RF = [C-A1D]/[A2 L(1+I)] (Eq. 11) where RF = the rating factor for the live load carrying capacity C = the capacity of the member For WSR: Inventory or operating level allowable stress For LFR: Nominal capacity of structural steel including loss of section For LRFR: Capacity based on as-inspected section properties multiplied by the resistance factor
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DESCUS-I Code Check Output
Moments Moments and Torsion Shears Diaphragm Axial Forces and Stresses Reactions Dead Load Deflections at Tenth Points Maximum Live Load Deflections Stress Ranges with Acceptable Categories Shear Connector Spacing Transverse Stiffener Requirements Maximum and Allowable Stresses Rating Factors by Girders Bridge Rating Summary
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