WR1

How do I know what is your confusion without you writing it down for me?

On 11/17/2017 at 10:42 AM, Ahsan Kazmi said:

Does code recommends any minimum limit for bearing capacity if the bearing capacity of actual soil is known?

I dont think code dictates that but yes common sense sure does. I wouldnt design foundation unless from some source I have the bearing capacity information. Even if it is preliminary design and you put a note that "the foundations have been designed assuming.....capacity", you should do some research of nearyby buildings. You cant just guess, i think.

First off, is your Limcon cracked or purchases? If cracked, there are certain variables in the software that are "FIXED". They do not change if you change values. So beware!

Depends if the sheet is correct? Does the sheet take into account moments?

On 1/5/2018 at 11:44 AM, asadishaq said:

If the frame is located in zone 3 or 4 it should be SMRF, and if it is in zone 2 it should be IMRF.

Really?

Moment frame type has nothing to do with location except some limitations in codes. Can't you have special moment frame in Zone 2? Yes, you can!

Type depends on the ductility and framing of building system. Do you think it has enough ductility? If yes then it could be special even in Zone 0. But obviously it will cost more to provide that ductility and detailing for zone 0.

But generally speaking, you could design special frames in zone 2B or ordinary in higher zones, depends on the framing.

On 12/11/2017 at 4:31 PM, miqureshi77 said:

temperature load can be assigned to the members that affected with the temperature variation only (like exterior members)

not true in all cases. uncontrolled internal temperature has the same effects like outside sun heat on the structure.

On 12/12/2017 at 12:09 PM, ZOHAIB SATTAR NAGRA said:

For islamabad how much temperature (degree celcius) should I apply to my external members because in islamabad temperature varies from five degre in winter and upto  46 degree in summer.........also what if internal temperature (in rooms) is also not controlled then in this case we have to take temp affect on internal members also???

 

There are usually documents stating weather station data. You should use mean yearly average highs and lows not daily.

On 12/12/2017 at 5:01 PM, SALMAN CH said:

You can ignore expansion joints till "60m" as per PCA

It also depends on approval authority. For example in Dubai, limit is 45m.

On 12/13/2017 at 12:42 PM, SALMAN CH said:

I would recommend to provide expansion joint

Expansion joints are nice from structural point of view only. As a structural engineer, Id try my best to avoid them. Construction isnt that easy for expansion joints. What about water leakage?

On 12/13/2017 at 4:39 PM, SALMAN CH said:

Applying temperature to vertical elements (Wall) will hardly effect your design, this is my observation.

Except ground floor columns and walls that will have huge forces due to restrain (supports).

On 12/13/2017 at 2:17 PM, ZOHAIB SATTAR NAGRA said:

will come an extra reinforcement to balance the forces due to temperature in addition to seismic and gravity reinforcement

This is my opinion. I don't think T+E should be added.

On 11/17/2017 at 10:42 AM, Ahsan Kazmi said:

Does code recommends any minimum limit for bearing capacity if the bearing capacity of actual soil is known?

Known or unknow?

Yes, more bars less dia is better. Also check what is commercialy viable. There is commercial as well as health & safety aspect to it as well. For example using less bars of dia 40 reduce congestion and easy handling and placing but is it safe for workers to carry such huge bar? Accidents?

You could also use concrete society report no. 34 for plastic design of industry ground slabs.

22 hours ago, Omar Khalid said:

1- Place shear walls opposite to each other, let's say you put a wall at the far right of a building, put another one with the same length and thickness at the far left one, .. etc that is to ensure the center of rigidity ( governed by walls mostly) coincides with the center of mass of the building to eliminate torsional movement of the building.

2- The far the wall is placed from the center of the building the better, as walls near the center doesn't resist much shear force as walls at the outer perimeter and the latter is good to prevent torsional movement.

3- The following is copied directly from the ACI design hand book:

''

Shear walls should be located within a building plan to efficiently resist lateral loading. Locating shear walls in the center half of each building is generally a good location for resisting lateral forces. This arrangement, however, can restrict architectural use of space.

Although shear walls are commonly located at the ends of a building, such wall locations will increase slab restraint and shrinkage stresses, especially in long buildings and buildings such as parking structures that are exposed to large temperature changes. Symmetrical wall arrangements provide good flexural and torsional stiffness. Walls at the perimeter resist torsional forces most effectively. Walls away from the perimeter, however, could have a higher tributary area and, consequently, larger gravity axial force to resist uplift or overturning. They are, however, less efficient in resisting horizontal torsion

An unsymmetrical arrangement, however, does not usually provide predictable torsional stiffness due to their eccentricity. Such a shear wall layout should be designed explicitly for torsion. A symmetrical arrangement is preferable to avoid designing walls for torsion.''

Good point again. In such cases, you have to deal with the notorious huge nerve sapping temperature forces.

18 hours ago, Saiful Islam Zaber said:

while all the beam are connected concentrically to column how can there be such large minimum moment ?? See the Column in grid E4 

8.bmp

You are not getting the point. Have you referred to the codes? Aci or bs or whatever? An interior column with huge axial load multiplied by minimum e can produce huge moment even if the original moment from frame is 0.

2d analysis is never recommended with walls above.

https://wiki.csiamerica.com/m/view-rendered-page.action?spaceKey=safe&title=Modeling+uplift+and+foundations+on+soil+supports

Hey man, hold on. Your building isnt symmetrical. Also the theres difference between axial stiffness of cols vs walls. This will effect z direction deflections from bottom to top stories.

2nd thing..safe..in safe deflections will be different than in etabs. This has been discussed no of times here and you can search.

If the building is regular as you said with same column sizes, axial shortening should be same provided loading and gemoetry all are same and symmetrical. Gravity deflection on same combination should be same at each level. And by deflection i mean z deflection not x.

10 under the root factored load in kN is the thickness required in mm (tried & tested here).

Decrease the distance between CR & CM. It will not eliminate 100% due to inherent torsion.

Signup with IStructE and start your road toward chartership.

In addition to above, to get an idea how point load is distributed, see PCI Handbook.

Answer is simple. Top columns have less axial load and more moment. That means more in the tension region of interaction diagram.

8 hours ago, Ahsan Kazmi said:

@ILYASweather you analyze it for 2D or 3D it doesnot matter.

It does. Simply use 3d.

Expansion joints in superstructure are provided for lateral movements e.g. from wind/earthquake/temperature/geometry. No need in foundations as soil has sink down effect for temperature and earthquake and winds and geometry effects are above ground.

You need to size the slabs for long term deflections. Forget these tables.

It will still design for minimum eccentricity. Refer to ACI chapter 10 I think. You can turn it off (not recommended) if you want in ETABS design overwrites.

It depends on the ratio of local area vs total area. It also depends on the location and importance of localized stress area among other factors. This is engineering judgement beyond the number crunching drudgery. I cant provide this as I am not aware of the project details. You could refer to your seniors for this.

And remember do not stop at this. There is always a solution no matter how hard the problem is.

For example may be your geotech engineer might suggest a lesser soil stiffness value at this location which will help reduce the stresses. You might increase the local thickness to better distribute the pressure. You could optimize the load combinations or even the load path of superstructure not to have the concentration here.

An important point here is if this is localized compression at corner then is it due to lateral loads? If yes then watchout for the reverse that is tension (blue color contours). This will be another whole new problem.

1. Depending on how much the value is exceeding you could increase thickness of the footing.

2. Soil improvement.

3. Reduce loads/stories.