node local coordinate system


Dear sir,

Refer to the model attached.

I defined the nodal local coordinate system at the abutment supports such that it lines up with the bridge skew.

I then defined the restraints at these nodes to be free in local x.

When I ran the analysis, I see some reaction in local x, say, under "testing lateral load".  How could this be possible?




It is happening because of numerical error caused by huge modulus of elasticity of material "4: Rigid". It is 2e+15 kN/m2. Usually, it is rigid enough if you define 1000 times of normal modulus of elasticity. For example, the modulus of elasticity for Conc C30 is 2.497e+7 kN/m2. Then, 2e+10 kN/m2 would be sufficient to represent rigid material property and also it can avoid the numerical error.

After the change above, I can see zero reactions in the local x direction as shown below.

DK Lee 
Creation date: 8/30/2018 8:10 PM      Updated: 8/31/2018 5:41 AM
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Model 3.mcb
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