TN Seminar Feb 27 15
32
Construction Engineering of Steel I - Girder Bridges Thanh Nguyen Georgia Tech Feb 27 2015
Transcript of TN Seminar Feb 27 15
Construction Engineering of Steel I-Girder Bridges
Thanh Nguyen Georgia Tech
Feb 27 2015
Why Steel I-Girder Bridges?
2
What changed & not changed?• More flexible structures
o 70 grade steel
o Designers pushing geometry limits
• Designers doing what they have always
done o Mostly 1D Line Analysis & 2D Traditional Grid
o Selection of critical design parameters based on long-established practices
o Not accounting for Lack-of-fit effects. When they rarely do, it is often not rigorous
o Erection engineering left to erectors
3
Key Objectives• Improved design guidelines to ensure
reliable fit-up
• Provide a clear understanding of
implications ofo Framing arrangements
o Cross-frame detailing methods
o Erection procedures
4
Outline1. Fit conditions
2. Bridge Construction Simulations
3. Fit-up Estimation
4. Parametric Studies
o Selection of Bridges & Erection Sequences
o Variation of Framing Arrangements
o Variation of Detailing Methods
5. Synthesis of a few Results
6. Streamlined Calculation of the LOF effects
5
1. Fit Conditions
6
No Load Fit (NLF)
Steel Dead Load Fit (SDLF)
No Load
Steel Dead Load
Total Dead Load
No Load
Steel Dead Load
Total Dead Load
Total Dead Load Fit (TDLF)
No Load
Steel Dead Load
Total Dead Load
2. Bridge Construction Simulations
7
Concrete Deck (S4R, Shell)
Flanges (B31, Beam)
Cross-frame Chords (B31, Beam)
Web(S4R, Shell)
Transverse Stiffener (B31, Beam)
Cross-frame Diagonals (T3D2, Truss)
Bearing Stiffener (B31, Beam)
3. Fit-Up Estimation• Fit-up forces: external forces required to put the
steels togethero CF Fit-up
o Field Splice Fit-up
• Unanticipated fit-up forces can lead to delay, increased cost & bridges not constructible
• First study to provide first-level of engineering estimates of fit-up
8
3. Fit-Up Estimation• A simple span bridge erection sequence
9
3. Fit-Up Estimation
10
Stage 2-1 Stage 2-2
Stage 2-3 Stage 2-4
3. Fit-Up Estimation
11
Stage 3-1 Stage 3-2
Stage 3-3 Stage 3-4
3. Fit-Up Estimation• Fit-up calculation: the forces developed at the
connection being made
• Elevations can be varied for holding cranes, lifting cranes and shoring towers
• Knocked-down CFs: Top and bottom connections
12
3. Fit-Up Estimation• First and second connection fit-up forces (F1 &
F2)
13
StageDetailingMethod
Holding Elevations
Minimum Fit-Up
Forces as a
Function of the
Crane Holding
Elevations
Comments on Configuration Pertaining to the Minimum Fit-Up Force
Holding Crane:
NLLifting
Crane: NL
Holding Crane:
SDLLifting
Crane: SDL
Holding Crane:
NLLifting
Crane: NL + 40
% SDL Camber
(upward)
Holding Crane:
NLLifting
Crane: NL + 80
% SDL Camber
(upward)
Holding Crane: NL
Lifting Crane: NL
- 40 % SDL Camber
(downward)
Holding Crane: NL
Lifting Crane: NL
+ 160 % SDL
Camber (upward)
F1 F2 F1 F2 F1 F2 F1 F2 F1 F2 F1 F2 F1 F2
2-3A
NLF 0.4 NA 6.5 NA 0.9 NA 1.4 NA 0.9 NA 2.6 NA 0.4 NA Lift-off at G2 supports
SDLF 2.5 NA 8.5 NA 1.9 NA 1.5 NA 3.4 NA 1.1 NA 1.1 NA Lift-off at G2 supports
TDLF10.
2NA
14.6
NA 9.4 NA 8.8 NA10.6
NA 7.7 NA 7.7 NA Lift-off at G2 supports
2-3B
NLF 1.7 1.8 7.0 1.7 2.0 2.0 2.4 2.3 4.6 4.3 3.3 2.8 NA 1.7 Slack cables on lifting crane (G2)
SDLF 8.9 7.411.
85.5 7.2 6.1 7.2 6.3
11.9
10.0
7.2 6.9 NA 5.5 Slack cables on lifting crane (G2)
TDLF28.
622.
327.
517.
328.
622.
325.
619.
728.6
22.3
24.6
19.6
NA 17.3 Slack cables on lifting crane (G2)
3-3A
NLF 2.8 NA 4.9 NA 3.3 NA 3.5 NA 2.3 NA 3.7 NA 2.3 NA Lift-off at G3 supports
SDLF 0.7 NA 6.6 NA 0.6 NA 0.9 NA 1.1 NA 1.3 NA 0.6 NA Lift-off at G3 supports
TDLF10.
0NA
10.4
NA 9.3 NA 8.7 NA10.0
NA 7.5 NA 7.5 NA Slack cables on lifting crane (G3)
3-3B
NLF 3.3 2.3 4.7 0.2 3.6 1.9 3.8 1.7 3.2 2.7 4.0 1.9 NA 0.2 No slack cables or lift-off
SDLF 7.0 6.7 9.5 4.9 6.2 6.1 5.7 5.7 7.7 7.2 5.2 5.2 NA 4.9Slack cables on lifting crane (G3) and on
holding crane (G1)TDLF24.
019.
123.
517.
724.
019.
124.
019.
124.0
19.1
22.5
18.2
NA 17.7
3. Fit-Up Estimation• Critical fit-up forces
• Critical crane loads
14
Detailing Method
F1 F2 Fmax
NLF 2.3 1.7 2.3
SDLF 1.1 5.5 5.5
TDLF 7.7 17.7 17.7
DetailingMethod
Lifting Crane Holding Crane
MaxLoad
Min Load
Max Load
Min Load
NLF 22.8 0 22.5 0.2
SDLF 21.2 0 18.7 0
TDLF 12.4 0 12.2 0
4. Parametric Studies 4.1. Bridges & Erection Schemes
• Leveraging NCHRP 12-79 research
• Selection of a subset of bridge designs & erection schemes from 12-79o From inside to outside vs. outside to inside on several curved
spans
o Phased construction
15
4.1.A. Curved Radially-Supported Bridges
16
Ls = 90 ft Ls = 150 ft Ls = 150 ft
Ls = 225 ft
Ls = 329 ft
Ls = 350 ft
4.1.B. Straight Skewed Bridges
Looc = 211 ft Ls= 150 ft
Ls= 300 ft
Ls= 150 ft
Ls= 150 ft
Looc = 259 ft17
4.1.C. Curved and Skewed Bridges
Lmax= 340 ft
Lmax= 366 ft
Lmax= 164 ft
Lmax= 195 ft
Lmax= 192 ft
18
4.1.C. Curved and Skewed Bridges
19
Lmax= 214 ft
Lmax= 279 ft
Lmax= 326 ft
4.2. Variation in Framing Arrangements
• Offsets & CF spacing near skewed bearing lines
20
4.2. Variation in Framing Arrangements
• Avoid connecting intermediate CFs directly into bearing locations
21
4.2. Variation in Framing Arrangements
• Stagger the intermediate CFs along lines parallel to the skew
22
4.2. Variation in Framing Arrangements
• Continuous CFs in curved-radially supported and curved and skewed bridges
23
4.3. Variation of CF Detailing Methods• All 3 detailing methods considered for the
completed bridges
• NLF is not considered for erection studies of straight skewed bridges
24
5. Synthesis of a few Results• Max Fit-up forces, curved radially-supported bridges
25
NLF SDLF TDLF
(A) EISCR1 90 17.5 200 3 0.45 5.1 3.3 7.4 22.3
(B) NISCR2,
Scheme 1150 24.0 438 4 0.34 6.2 16.6 28.7 54.0
(B) NISCR2,
Scheme 2A" " " " " " 84.4 82.5 80.2
(B) NISCR2,
Scheme 2B" " " " " " 40.4 19.4 50.5
(C) NISCR7 150 74.0 280 9 0.54 2.0 21.3 35.9 75.3
(D) NISCR10 225 74.0 705 9 0.32 3.0 18.6 20.4 21.8
(E) EICCR11 322/417/329 40.4 4 0/0/0.80 8.0/10.3/8.1 37.5 86.3 130.0
(F) NICCR12 350/350/280 74.0 909 9 0.39/0.39/0.31 4.7/4.7/3.8 28.4 38.6 57.4
(G) EICCR4219/260/211/
162/256/19036.7
968/3@1108
/968/4
0.198/0.235/0.190/
0.146/0.264/0
6.0/7.1/5.7/
4.4/7.0/5.212.3 12.6 16.0
Max Fit-Up Forces (kip)Bridge Ls (ft) wg (ft) R (ft) ng Ls/R Ls/wg
5. Synthesis of a few Results• Max Fit-up forces, straight skewed bridges
26
SDLF TDLF
(H1) EISSS57 211 63 61.0 69.5/-4.4 7 0.77 3.5 1.0 5.0 15.0
(H2) EISSS57 " " " " " " " " 5.0 14.2
(I1) NISSS14 150 150 74.0 70 9 1.36 2.0 2.0 3.6 15.3
(I2) NISSS14 " " " " " " " " 2.5 7.5
(J1) NISSS54 300 300 74.0 70 9 0.68 4.1 4.1 9.2 73.5
(J2) NISSS54 " " " " " " " " 8.4 47.9
(K1) EICSS12 150/139 150/139 41.0 59.6 6 0.47/0.50 3.7/3.4 3.7/3.4 0.6 6.3
(K2) EICSS12 " " " " " " " " 0.4 7.7
(K3) EICSS12 " " " " " " " " 1.2 17.0
(L) NICSS16 120/150/150 120/150/150 74.0 70 9 1.69/1.36/1.36 1.6/2.0/2.0 1.6/2.0/2.0 0.8 36.9
(M1) EICSS2 259/255/220 241/183/220 66.6 58/61.8/38/38 8 0.48/0.49/0.23 3.9/3.8/3.3 3.6/2.7/3.3 4.9 46.9
(M2) EICSS2 " " " " " " " " 0.8 2.8
Max Fit-Up
Forces (kip)Bridge Lmax (ft) Lmin (ft) wg (ft) q (deg) ng Is Lmax/wg Lmin/wg
5. Synthesis of a few Results• Final girder elevations
27
Curved radially-supported bridge Straight skewed bridge
6. Streamlined Calculation of LOF effects
• Due to SDLF and TDLF
• Engineers rarely include these effects
• Most rigorous & accurate method is to calculate the initial strains
28
-10
-5
0
5
10
15
20
25
30
0 0.2 0.4 0.6 0.8 1
fl(k
si)
Normalized Length
TDLF SDLF NLF
6. Streamlined Calculation of LOF effects
Engineering strain ε𝑖𝑛𝑖𝑡𝑖𝑎𝑙 =𝐿2 ∗cos(α)−𝐿1
𝐿1
Rotated engineering strain ε𝑖𝑛𝑖𝑡𝑖𝑎𝑙 =𝐿2 −𝐿1
𝐿1
Log strain ε𝑖𝑛𝑖𝑡𝑖𝑎𝑙 = 𝑙𝑛𝐿2
𝐿1
29
𝐿1 𝐿2
6. Streamlined Calculation of LOF effects
• Time consuming by hands
• Considerable efforts via analysis software
• A tool has been developedo Efficient and accurate
o Gives the same results as analysis software
• Tool features:o Curved and/or skewed bridges
o Common CF types
o Common strain types
o Variation in bridge geometries (section changes, number of spans...)
o Bearing fixities
o 2D grid (fixed end forces) and 3D FEA (initial strains)
30
Final Observations• Supports some of the current industry
recommendations
• Understanding of curved and/or skewed
bridge behavior
• Recommendations/guidelines on:o CF framing arrangements
o Detailing methods
o Erection sequence
• First study that provides detailed first-level estimates of fit-up
• Tool for streamline calculation of LOF effects
31
Questions?
