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Dear curlyq, try tiping all your variables (or formula fields) with one decimal number (for example 1.0, 2.0). Best regards, Sebastian

Dear mralhasani, when you use the merge command you are "joining" 2 or more shell elements (with the loss of precision that this implies). You can draw a single shell element with the real slab dimensions, and then make a division (in the same tool box as the merge command) in...

Dear mscme, you should look in ACI 207.2R "Effect of Restraint, Volume Change, and Reinforcement on Cracking Mass Concrete". You should design in accordance to ACI 318, and then check with the Lutz equation (taking into account the volume change tension in steel) the crack width...

Dear skicat, first of all make your model, with the proper stiffness and masses. If you want to consider same load as a mass for the dynamic analysis, go to define/mass source. When you run the analysis, activate "MODAL CASE" (as default is activated). Then you should go to...

Dear rodmanera, you should do the following: Go to: Define/Joint pattern/Add new... Select the shell you want to load, and the go to: Assing/Joint pattern/ Select the Joint pattern name and specify the function you want for the load (in global axes). Then go to: Assing/Area...

Dear 3doorsdwn, in my opinion for a plane-frame the charts could be valid (a frame can easily be modeled as a SDOF, in the horizontal direction). For a more complex structure, I would model the hole structure and the explosion as a load (in function of time). You should...

Search in here: http://www.concrete-accessory.com/coil-insert Best regards, Sebastian

I would search which mode includes vertical displacements, using the animation tool. Then you should use the equation with the first and "the vertical mode". The problem is that for vertical modes the damping could be lower, in my opinion.

Dear zhddz, Yes, I ment the natural frequency from the first two modes of modal analysis. But for this structure, maybe you need to use another natural frecuency (please read page 420 of the previous attach). In my opinion the natural periods of the structure are very high for a...

Dear zhddz, with SAP 2000 you can easily find out the first two natural frecuencies (without any damping). Using the solution of Chopra, you can calculate ao and a1, even if you don't known the mass or the stiffness matrix. Regards, Sebastian

Dear zhddz, SAP 2000 uses "Rayleigh Damping". It considers a mass-proportional and a stiffness-proportional damping in order to achive the real damping (lets say 5%). These two values are the coefficients ao and a1. C = ao.M + a1.K Where: C = damping matrix M = mass...

You can make several load combinations, with different types of load percentages. For example: LOAD COMBINATION 1: 0.10 x DEAD LOADS LOAD COMBINATION 2: 0.20 x DEAD LOADS Representing, 10 and 20% of the dead load. Best regards, Sebastian

In my opinion: Dynamics of structures - Theory and Applications to Earthquake Engineering by Anil K. Chopra

Dear vsator, I would model the slab as a thick shell element, and the beam as a frame element (you can use the concrete design tool). In order to obtain results close enough to the hand calculations, you should: 1) Set the torsional stiffness of the beams to zero, to model a pinned...

In my opinion for underground structures it's important to consider the seismic load. In this case the structure will move with the soil, the inercial forces aren't very important. There are various ways of considering this load case: 1) Analytical (models with springs or with forces and...

You are welcome!

Dear iotoma, the non-linear combination for the modal analysis (as seen in the last attachment), should have non-linear load cases. Take a look at the new attach.http://files.engineering.com/getfile.aspx?folder=8ee0b5f3-c9dd-428a-982e-347e0b860948&file=a.JPG

Dear iotoma, have you set the non-linear case in the modal analysis? Take a look at the attachment.http://files.engineering.com/getfile.aspx?folder=4a5fb4db-1b1d-4aa4-8e89-808fe8490f7e&file=1.JPG

I think that the problem is that SAP2000 doesn't introduce plastic hinges where the section fails. As a result, you have the same stiffness, the mass will obviously be the same... and that's why your period is exactly the same. You need to define the non-linear properties of the material in...

Dear itoma, in order to increase the period, the structure should: a) have more mass or b) be more flexible (lower stiffness). In your case, you want to subject the structure to an earthquake and simulate the damage that this one does to the structure.. and this damage should increase...