shashank b's Activities

Seismic load with springs- Repeat load case

shashank b — Tue, 21 Aug 2018 04:54:06 GMT

i am currently designing an irrigation channel which requires application of compression springs along with seismic loads. i have defined seismic loads first (load no. 4). i have used repeat load cases to combine all the loads.

In summary, i can see the moments being introduced due to seismic forces but it seems they are not being combined with other load cases. For eg. the forces summary for load cases excluding and including seismic forces is exactly the same (shown in figure below)?

i am unable to exactly pin point the problem as to why earthquake effect is not combining?

Load case definitions

load case (without seismic load)

load case (with seismic effect)

Staad 3D plate model

shashank b — Mon, 23 Jul 2018 18:31:41 GMT

Dear all,

i am trying to model 3D plate model with the application of compression springs both at base and side walls and have some doubts regarding that:

1) Initially i was trying to apply "load combination" command to add the respective loads but after going through staad literature i found that "repeat loads" were to be used in this case.

Upon the application of repeat loads i noticed close to 50% decrease in the bending moment . Isn't this decrease too large or am i making some mistake?

2) In order to reduce bending moments, i applied joints using the release option in plate specifications for the whole structure. But to my dismay, i see no perceptible decrease in the maximum bending moment (rather an increase in bending moments?? why is this happening?

3) Also regarding application of release, i am confused about direction in which they are to be applied. Figures below show 2 directions in which releases can be applied, which one of them is correct?

4) Also, i would need some advice on the support conditions to be employed. Should i use fix boundary conditions at corners of base (with intermediate nodes being attached to spring) or should i go for Pinned/fixed boundary condition on top of side wall as shown below

3D plate model

shashank b — Mon, 23 Jul 2018 13:33:57 GMT

Dear all,

i am trying to model 3D plate model with the application of compression springs both at base and side walls and have some doubts regarding that:

1) Initially i was trying to apply "load combination" command to add the respective loads but after going through staad literature i found that "repeat loads" were to be used in this case.

Upon the application of repeat loads i noticed close to 50% decrease in the bending moment . Isn't this decrease too large or am i making some mistake?

Spring constants application-Staad

shashank b — Wed, 14 Feb 2018 16:15:59 GMT

Dear all,

Currently i am modelling tunnel lining for a project in Staad Pro. This requires the application of compression springs both on sides as well as invert. i have doubts regarding direction of radial and tangential stiffness to be applied in the model.

1.As far as i understand, the KFX, KFY and KFZ values are to be specified along the current global axis of the model or is it a convention that radial stiffness always has to be specified as KFX irrespective of the global axis?

2. Directions of radial stiffness shall be different for the invert (Global vertical) and side walls (Global horizontal). Do we have to consider different directions( KFX(radial for side walls) and KFY(radial for invert)) while specifying stiffness or they shall remain same (e.g. as KFX(radial for sidewalls as well as invert)) throughout the model?

Regards

Compression springs-Staad pro

shashank b — Thu, 15 Feb 2018 04:18:38 GMT

Dear all,

i have some doubts regarding allocation of compression springs in the Staad model. My model essentially consists of an invert floor with vertical sidewalls and i need to provide compression springs both at invert-soil and sidewall-soil interface. All the surfaces have been modelled and meshed as plates.

1. In order to define the compression spring i have chosen a reference joint opposite to the plate where the spring is to be attached.Is this the correct way of doing it?

2.I have a number of nodes along each sidewall of the structure. Do i have to define reference points for each horizontal line of nodes and refer them with a node at opposite end? Is it not possible to select all the nodes lying on a sidewall at once and simultaneously refer them to some node at opposite wall. i tried using both the approaches and got different results

3.Also , in the invert, i have chosen the 'Ref' option in the inclined reference point menu? Is it the right way of defining reference points of invert slab or is there any other way

Thanks and Regards

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