Saad Pervez

Can you share your model? because I have never seen this warning before.

Then don't connect them? Stop your wall before this joint?

If you can design this slab with a 7" thickness, there is no need to provide a beam in the step region, because again a 14" depth won't be sufficient for a 30' span. And your beams would be projecting out on top of the wall, which is not very good from an aesthetic point of view. Drop below the slab can also obstruct MEP services. This is a personal point of view by the way, technically you can provide beams in the steps region.

1) Its behaviour would be one way or two way? Depends on your design but 6" slab over a 20'x30' span is not fulfilling ACI's minimum depth requirements. 2) Is there any special detailing required in steps region? yes 4) The left side beam is rectangular-beam and right side beam is T-beam? left side is an inverted beam

No specific information is available on this topic. However, judging by CSI's answer to this question: https://wiki.csiamerica.com/display/kb/Subdivide+frame+objects each frame is treated as a discrete element, and by default, auto meshing is done at internal points and/or intersecting frames which can also be turned off.

First, be sure of the units. Second, there is no difference between two. ETABS 13 and onwards, they increased the non linear capabilities so it 'wont effect most of the users' as they say in their manuals. You can refer to release notes to find the new enhancements/changes. Also make sure, the design code, reduction factors and load combinations you are using in newer version are right.

Response spectrum analysis is a linear-dynamic statistical method of analysis. Use the flow chart below to determine if you need to do dynamic analysis for your structure or not.

Slab element number during analysis and slab area labels are different. Slab number during analysis is the position of that element in the database, slab area labels have the notation F### and usually indicate when this particular element was drawn, slab area labels can also be repeated in different stories, slab element number is unique. Exporting to EXCEL will also not help because EXCEL will slab area labels, not slab element number. Exporting the model to .e2k and the importing it back might help, OR you can do a manual check of all your model by studying the mesh. In my experience, this error is caused by a shell element with 2 nodes only, which happens when you move one set of points to already existing points by move command, this will merge the points but the element defined between them stays in the database. Hope this helps.

Section 14.3.2 and the minimum limit of 0.0015 applies to walls that are not resisting shear. If the wall is resisting horizontal shear forces in the plane of the wall, section 11.9.9.4 applies, and vertical reinforcement should be minimum 0.0025 times the gross concrete area.

Glad to be on board

You should do center to center modelling for this structure and to capture the eccentricity, you can either model the column as shell element like Sir Rana said or you can use insertion points for beams, always look at the extruded view to know the actual arrangement of the elements you're modelling. I'll illustrate the use of insertion points, you can use the approach you find suitable. Insertion points will capture real world behavior by keeping your Finite Element model closer to reality. Consider the 2 beams below, the are exactly the same, they look exactly the same. We'll select the beam on the right hand side and go to assign>frame>insertion points. And "insert" the beam with eccentricity of 250 mm at both ends. End-I with a positive eccentricity and End-J with a negative eccentricity, (don't forget to uncheck the box!) Then we look at the extruded shape again, we notice that the beam is inclined now (which matches your case). If we look at the "unextruded" view, both beams will look the same. We run the model, we can see that the values for shear force are different because ETABS is calculating forces based on inclined length. If eccentricity is captured, there should be a moment in 2-2 direction. Which we can see is there and is numerically equal to P*e = 30103.99*0.25 = 7526 kN-m Hope this helps.

Sag rods will restrain translation, you can draw points where sag rods are connected, divide the frames at those points and apply vertical translation point restraint only.

According to ACI 318-08 Cl 10.5.3, you can ignore the minimum reinforcement requirement if As(provided)>1.33 As(required). You can use this provision in your favor if you want.

thickness of base slab itself, isn't 6 ft the height of your retaining wall?

You can take off quantities from etabs as well, I have worked on BlueBeam Revu, quantity take off is severely limited, you still have to draw and mark everything on plan, it is not automatic.

lesser W means lesser base shear, reduced design forces. Life is easier when forces are less.

flowchart is from a presentation given to Govt of Dubai by SK Ghosh, found it on Scribd. Other images are from NEHRP Seismic Design Technical Brief No 3 "Seismic Design of Cast-in-Place Concrete Diaphragms, Chords, and Collectors" In my opinion this requirement is specific to Seismic Zone 3&4, are you designing for Zone 3 or 4? In my understanding this relates to structures having torsional irregularity where the wings might vibrate in different directions when eccentricity is amplified as per UBC clause 1630.7. Some collector elements will have more compression and less tension if torsion is amplified. According to the information provided your staircase is forming part of the lateral force resisting system. And again the one-third stress increase is Zone 3&4 specific requirement, and yes if you are using overstrength factor, then your allowable stress increases. If your structural system doesn't require using Omega then don't use it.

A: In my opinion, both sides, this is to exclude an architectural projection e.g. a patio roof from this definition. A: ACI318-11 R21.11.7.5: "....collector elements of diaphragms are designed for force amplified by a factor Ω ..." so collector elements will be designed using overstrength factor in strength design method. A: diaphragm chord and drag members are not separate elements, they are part of the diaphragm. The components at the diaphragm boundary acting in tension and compression are known as tension chord and compression chord. Drag members have 2 types, collectors and distributors. Both are part of the diaphragm, a collector is an element that takes distributed load from the diaphragms and delivers it to the vertical element, a distributor takes force from the vertical element and distributes it into the diaphragm. See attached images. A: Motion of projecting wings can be ignored if dynamic analysis is performed along with finite element analysis aka ETABS model. A: If your stair case is not forming part of the lateral force resisting system and is not connected to diaphragm you can ignore this. A: Please see the attached flowchart published by SK Ghosh, it is very helpful.

What is the confusion? sin(radians(6.8)) in excel will convert 6.8 to radians, and then perform the trig function. Result should be equal to sin(6.8) on the calculator.

In Excel, default unit for trigonometric functions is Radians. You're using the formula SIN(RADIANS(VALUE)). You're forcing excel to assume that the value already in radians is in degrees. SIN(6.28 radians) should be zero, using your formula the value is 0.11. Remove the RADIANS(), use SIN(VALUE) instead.

Sir @Rana, can we use dummy lines? A dummy line can be drawn replicated every unit length and tributary triangular load applied to that line.

What exactly is your problem? Check your story drift if you are worried about flexibility, if it is within limits then you're good to go.

Which version of ETABS?

you're importing a text file that has a different syntax to the one recognized by ETABS '16. Nothing serious.

which software are you using?