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  Cable-stayed bridge during construction



 

Cable-stayed Bridge
Model Examples



Model description



Input



BIM model



Analysis model



Landscape model



ICDAS Basis of Design



Workflow of Software



Additional features



Rendering, Animation &
Vitural Reality
  


Case Study and 
Research




 








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Introduction


Cable-stayed bridges are construction-friendly with free cantilevering. The deck sections are erected symmetrically

starting from the two sides of a pylon while the balance is kept by themselves (all sections are considered equally

in weight and length in this particular case of study). The same principle applies on the other pylon in case the bridge has two pylons in longitudnal direction. However, bridges with long main span, short side spans, and significant slope

in longitudinal direction will have notable heavier main span than side span during erection. The worst situation during the construction phase is when the stage of maximum double cantilever is reached. In combination with an unexpected

wind speed, vibrations can rise important problems for both bridges before they are being locked together at the

centre of the main span.


This case study will set focuses on FEM model and analysis of cable stayed bridge, with:

 

§       Descriptions for creation of cable stayed bridges in LUSAS FEA

§       Initial tensions of the cables. Displacements and stresses of the deck girder.

§       Natural mode shapes and frequencies of the cantilever bridge during construction, and the final bridge.

 

Numerical model is assumed as

§       150+302+150m span, concrete pylons and steel streamlined line box girder are applied.

§       Semi-fan cable-stayed arrangement with 6% slope of the deck in longitudinal direction, and reduced to

      1% at the centre main span.

 

    

 

ICDAS Cable Stayed Bridges


FigureSemi-fan cable-stayed arrangement, 150+302+150m span










    

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Main system

ICDAS Cable Stayed Bridges

 

FigureNumber of the cables section number on deck, Left side of bridge

 

ICDAS Cable Stayed Bridges

 

FigureNumber of the cables section number on deck, Right side of bridge


  Deck cross section

 

Revit 3D using Civil Structures (Option 2)

The cross section is designed by input data in Excel BRIDGE sheet described in Geometry.

By running Add-Ins in Revit family file ICDAS_Profile_2D_Deck.rfa, the cross section is created automatically.

 

This Revit family file will then customize in a Revit project file Bridge.rvt to create the 3D bridge automatically.

Note that in Bridge.rvt the bridge's corridor overpass and corridor underpass must be in integration with

AutoCAD Civil 3D, where the bridge location is determined. This geometry work is the first important part of the

bridge project which is described in ICDAS Bridges Manual.

 

Lusas Analysis

The second part is to create a FEM model automatically. ICDAS CSB creates file LusasCSB.cmd file automatically when running Add-Ins in Revit. By importing this file in LUSAS one will get a 3D FEM model having a cross section as shown below. The cross section is designed with 5 longitudinal lines creating top left side of deck, line no. L1 to L5, and 5 longitudinal lines for top right side of deck, line no. R1 to R5. There are 9 longitudinal lines create the bottom of deck, line no. B1 to B9, see Analysis. Changing positions of these lines one will obtain a new cross section and a new bridge in both of Revit and Lusas models.

 

Thickness and density equivalent

The equivalent thickness for top and bottom plates of the deck is calculated to 175mm to present the stiffness

of the plate t1, the ribs t2 and the other dimensions as show below.


Alternative Text


Dimension of top and bottom plates (mm) 
Cross distance between ribs, c = 300

Upper rib dimension, c = 300

Lower rib dimension, b = 200

Height for the stiffener, h = 300

Distance to next two stiffeners, f = c/2

Upper plate thickness, t1 = 20

Rib plate thickness, t2 = 10


Figure: FEM cross section with equivalent plate thicknesses

 

The equivalent density is calculated to 0.191x7.85tons/m3.


However, to overcome the nonlinear analysis convergence the following input has been assuming for the top and

bottom plates of deck in this case study

 

(Thickness, Density) = (175mm, 7.85tons/m3)

 

 

 

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 Nonlinear Analysis Converge Deadload


Support conditions


Support conditions are very sensitive in nonlinear analysis convergence for the cable stayed bridge. To overcome convergence, the support conditions are assumed as described below.

 

§       For cantilever bridge during construction, there are two support conditions assumed for the first two

      loadcases. "Fixed UX, UZ" is needed in loadcase1 Initial Forces at both ends of deck. "Free all" is used

      in loadcase2 DeadLoad in order the deck to be entirely carried by the cables.

§       For the full bridge "Fixed UX, UY, UZ" assumed at both ends of deck for all load cases.

 

The steps of increments of load factors to convergence 1.00 are highlighted in Loadcases tab shown below.

These steps are set in Nonlinear and Transient control parameters.

 

Desktop i7-3820M 3.6GHz 16GB RAM has been used. Window 7 Enterprise is used.



 

150+302+150

 

Figure:

Support conditions for the cantilever bridge during erection

Vertical deflections at deadload convergence (m) 

 


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150+302+150

 

Figure:

Support conditions for the full bridge.

Vertical deflections at deadload convergence (m)

 

 

 

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ICDAS  •  Hans Erik Nielsens Vej 3  •  DK-3650 Ølstykke  •   
E-mail: th@icdas.dk   •  Tel.: +45 20 20 33 78  •  CVR no.: 34436169 
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