14 Understanding Staged Construction
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Transcript of 14 Understanding Staged Construction
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hewson consulting engineers civil, structural and bridge engineering
Third International Bridge Seminar
Understanding Staged Construction
Integration of staged construction and time
dependent effects into the design of bridges
Andrew Hodgkinson
hewson consulting engineers civil, structural and bridge engineering
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A brief history
Staged construction is not new
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A brief history
Engineers have been using staged construction to build bridges for centuries
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civil, structural and bridge engineering
Staged Construction
Engineers must assess the significance of staged construction on the final forces and deflections in the structure.
Time dependant effects of creep and shrinkage must be taken into account through idealised models e.g. CEB-FIP78, CEB-FIP90, ACI etc.
Checks of adequacy of the structure during construction may also be required.
Determination of precambers to ensure correct final structure geometry is often needed.
Can be utilised to alter and optimise force distribution in structures
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Bridge Construction Methods
The most common bridge construction methods include:
Composite beam and slab (precast or steel beams)
Full Cantilever Method (FCM) integral or bearings
Span by span insitu or precast
Incrementally launched
or a combination of these methods
Greatly influences the final force and stress distribution
throughout the deck
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Bridge Construction Methods Composite Methods
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Bridge Construction Methods FCM Method
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Bridge Construction Methods Full span or Span+1/4 method
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Bridge Construction Methods Incremental launching
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Analysis Methods
Methods have developed over time
Engineers have been used to developing a series of analysis models for the significant construction stages and combining the
results.
Creep redistribution idealised using hand calculated upper/lower bound creep (f) factors.
Prestressing usually idealised as manually calculated equivalent loads
Many bridge designers have developed spreadsheets in an attempt to make the analysis more efficient.
Nothing wrong with these methods as they have served us well over
many years but there are now alternatives
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Analysis Methods
In-situ stitches
balanced
cantilever
Cantilever
Dead load
BMD
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Analysis Methods
As-built BMD
Instantaneous
BMD
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Analysis Methods
Final
BMD
Over time the bending moment distribution creeps from the as-built
condition towards the instantaneous condition. Masbuilt
Minstant
f eMMMM 1.)( asbuiltinstantasbuiltfinal
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Integrated Analysis Method
Results require no post-processing to combine separate analyses
Calculation of creep/shrinkage automatically based on actual construction time-line
Combination with in-service static and dynamic loadings on structure can be undertaken within the analysis
Iterations to achieve economic design are quick to implement.
A greater level of accuracy is achievable.
Precambers readily determined
A method by which all construction stages, all loading
(including prestress) and time dependant effects (where
applicable) are integrated into a single analysis
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Example 1 Composite Precast Beam and Slab
N6 Galway to Ballinasloe PPP Scheme ST26
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Example 1 Composite Precast Beam and Slab
N6 Galway to Ballinasloe PPP Scheme ST26
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hewson consulting engineers
civil, structural and bridge engineering
Example 1 Composite Precast Beam and Slab
N6 Galway to Ballinasloe PPP Scheme ST26
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Example 2 Insitu PT voided, top-down
M3 Clonee to North of Kells PPP Scheme S20
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Example 2 Insitu PT voided, top-down
M3 Clonee to North of Kells PPP Scheme S20
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hewson consulting engineers
civil, structural and bridge engineering
Example 2 Insitu PT voided, top-down
M3 Clonee to North of Kells PPP Scheme S20
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hewson consulting engineers
civil, structural and bridge engineering
Example 2 Insitu PT voided, top-down
M3 Clonee to North of Kells PPP Scheme S20
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hewson consulting engineers
civil, structural and bridge engineering
Example 2 Insitu PT voided, top-down
M3 Clonee to North of Kells PPP Scheme S20
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hewson consulting engineers
civil, structural and bridge engineering
Example 2 Insitu PT voided, top-down
M3 Clonee to North of Kells PPP Scheme S20
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Example 3 Curved FCM Bridge on bearings
Johor Ramps
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Example 3 Curved FCM Bridge on bearings
Johor Ramps
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Example 3 Curved FCM Bridge on bearings
Johor Ramp A
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Example 4 165m FCM Bridge integral piers
Coastal Highway from Johor Bahru to Nusajaya Bridge 2
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Example 4 165m FCM Bridge integral piers Coastal Highway from Johor Bahru to Nusajaya Bridge 2
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Example 4 165m FCM Bridge integral piers Coastal Highway from Johor Bahru to Nusajaya Bridge 2
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Example 5 Concrete Cable Stayed Bridge
Bonny River Cable Stayed Bridge, Nigeria
overall length 930m with 350m main span
single plane of stays
diamond pylons
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Example 5 Concrete Cable Stayed Bridge
Bonny River Cable Stayed Bridge, Nigeria
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Example 5 Concrete Cable Stayed Bridge
Bonny River Cable Stayed Bridge, Nigeria
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Example 6 Concrete/Steel Cable Stayed Bridge
New Wear Bridge, Sunderland
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Example 6 Concrete/Steel Cable Stayed Bridge New Wear Bridge, Sunderland
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Example 6 Concrete/Steel Cable Stayed Bridge New Wear Bridge, Sunderland
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Concluding thoughts
Integrated analysis can save time (and money) where staged construction is important
Accurate analysis of structure deflections and required precambers
Efficient analysis provides opportunities for design refinement
Careful implementation needed to ensure that active elements, boundary conditions and loads accurately represent each construction stage
Not to be treated as a black box careful checking of results is needed.
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A final word of warning