Steel frame used to support coefferdam

[cn07akj]

Hi,

I have a question with regards to a part to my assignment,
I have a steel frame with central cross strut which must be designed to resist a lateral design load of 50kn/m. I have to calculate the max bending moment, shear force and axial load for each of the long and short waling memebers plus the central strut

The steel frame is 10m x 5m, with the central strut halfway along the 10m length(at 5m), a UDL is applied to all sides of the frame
The long waler is continuous over the central strut but all other joints are pinned.

I am unsure whether (wl^2)/8 would work for the max bending moment, and the shear force would be wl/2.

Would anybody beable to help with my query?

 

[Qshake]

Unfortunately cofferdam analysis and design can be a complicated undertaking. The reason being is that because of it's risk to the contractor, many engineers for contractors will design cofferdam frames based on pinned designs even though the members are continuous. The joints are then designed to develop the capacity of the member and not a specific reaction.

In reality, cofferdam frames are continuous around the perimeter. However, it is conservative to use wl^2/8 for the design of the walers thereby neglecting any moment reductions due to continuity.

You need to discuss this analysis/design with your senior engineer and follow his/her recommendations for how they want it designed and also ask them to explain the 'real' structural behavior of the frame so you can understand better the structure under investigation.

Regards,
Qshake

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