GSA – Getting it Right

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What's New GSA 8.7?• New Steel Design Codes 

• New RC slab design codes 

• New Footfall Analysis Codes — BS 6841:1987; BS 6472-1 - 2008; User defined frequency weighting curve.

• Non-linear Shell Elements

• Assemblies and Assembly Results 

• Modal and Seismic Analysis Improvements

• New Mesh Generation Engine — quicker processing, producing smaller and better conditioned meshes.

• Curved Members 

• Faster processing — including faster grid load expansion, faster response spectrum analysis, faster post processing, and faster RC Slab calculations.

• New GsRevit Functionality — improved coordination, improved section mapping and Revit 2014 compatibility.

• Patterned Load — a set of tools for the analysis of generalised patterned floor loading.

ExamplesWhen things go wrong

Sleipner A Tacoma Narrows

I-5 Skagit River Bridge Savar Building, Banglaseh

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Sleipner A Offshore Platform

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Sleipner A Offshore Platform

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Sleipner A Offshore Platform

What can go wrong?And how can you fix it?

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Did you really mean to do that?

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The key thing to remember is…

GSA MODEL

RUBBISH OUT

RUBBISH IN

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What is the matrix?

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What is the matrix?

54321

………………………………………………….

…………………. … = …

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Please release me…

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Please release me…• Restraints

• All nodes are free to move, though controlled by the attached elements, unless they are restrained in some way

• Typical use – support points

• Rigid Constraints• Rigid Constraints / Links / Joints

Means for adding infinite stiffness between nodes without problems in the stiffness matrix

• Typical use – floor diaphragms

• Releases• All elements are fully fixed to the nodes and hence other

elements, unless they are released in some way• Typical use – beam connections

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Units

If you don’t get what you expect:check your units

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Materials

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What a difference that shear makes

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What a difference that shear makes

• Giving a property a zero stiffness will lead to instability in the matrix

• Except zero shear stiffness, as this switches of shear deflection…

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Location, Location, Location

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Location, Location, Location

• 1.234567890• 12345678.90

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FEA is not CAD

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FEA is not CAD• The main purpose of CAD is to represent the physical

requirements of the structure and communicate it to others

• The main purpose of FEA is to mathematically predict the physical behaviour of the structure and to facilitate the design of the elements

Do you really need the offsets…?

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Loads of problems

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Loads of problems

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Loads of problems

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Stability

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Stability

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Stability

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I know that the answer is around here somewhere

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I know that the answer is around here somewhere

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I know that the answer is around here somewhere

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Size matters

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Size matters

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Another fine mesh…

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Another fine mesh…

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Another fine mesh…

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Tricks and Tools

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Tricks and Tools• Look at the deflected shape• If you are doing a static analysis

• Run a dynamic one as well

• If you are doing a dynamic analysis• Run a static one as well

• If something is just not right• Run a Model Stability

Diagnostic analysis

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Many a slip…

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Lessons from the floor

GSA – Getting it Right