Steel Composite Bridge Design

March 4, 2021

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In February 2019,  we hosted a webinar, "Case Study of Steel Composite Bridge Design" by Marco Bonomo, Senior Bridge Engineer, Atkins, UK


The webinar shows a case study of designing steel composite bridge.



Key Points


In this webinar, through a case study of a steel composite bridge based in the UK we will discuss about:


1. Friendly environment for composite structure analysis and design in midas Civil

2. How to set a moving load analysis

3. How to set a construction stages analysis

4. How to set combinations of actions for design and/or check of elements

5. Study of composite sections from classification to design/check results

6. Comparisons of results between midas Civil and presenter’s personal spreadsheet

7. How to use the dynamic report generator tool



Let's take a little bit of a deeper dive into what our webinar covered. 


Steel composite bridges are widely used in the UK, so it is quite important to know how to model and design such kind of structures. The steel section’s classification is vital to structure both the modelling and the design approach. For class 1 and 2, plastic analysis of sections is allowed, so that construction sequences are not important for sections’ checks. For class 3 and 4, sections show an elastic behavior including buckling effects for the latter. Because of that, construction phases need to be taken into consideration while sections’ checks.


Flowchart for steel section classification



Flowchart for steel section classification

There are many advantages to using the midas Civil's steel composite girder bridge wizard feature. The wizard helps to model the initial steel bridge and it is also used as a template for other initial steel bridge. Layout, section, loads and construction stage can be easily generated by making automatically groups of them.



Lots of vehicle loads should be defined according to several different codes. In midas Civil, vehicles automatically placed to maximise or minimise forces on elements and long/short term effects automatically managed during the construction stage.



Define traffic line lane and traffic load



In order to perform the construction stage analysis, following data is required.


Step 1 : Groups

Step 2 : Time dependent material properties

Step 3 : Link time dependent and general materials

Step 4 : Construction stages and time steps

Step 5 : Composite sections for construction stage

Step 6 : Set up construction stage analysis option

Step 7 : Perform analysis




Construction Stage Analysis Inputs







Advantages in using composite girders:

- Reduction of buckling effects in comparison to full steel girder

- Reduction of weight and cracking in comparison to a reinforced concrete girder

- Easy and fast construction method with traffic disturbance reduced to min

- Reduction of deflections


Aspects to take into special consideration during design:

- Section : full plastic (class 1-2), elastic-plastic (class 3) and elastic (class 4)

- Construction stage analysis : relevant only for section class 3 and 4

- Bracing system : vital to spread forces between girders due to torque

- Stud : crucial element to allow the section to act compositely


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About the author
Marco Bonomo | Senior Engineer | Atkins SNC Lavalin

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