Waqas Haider

Thanks a lot for sharing...  

Dear Saiful Islam,
Immediate deflection vs long-term deflection is one issue.
Linear analysis vs non-linear analysis is another.
 
In ETABS, generally we are almost always performing linear analysis. That means deflection is directly related to the load applied without long-term non-linear effects. So let's ignore non-linear analysis for a moment.
In linear analysis, now the question is how do we get immediate and long-term deflection.
Immediate deflection could be non-cracked deflection or cracked deflection. Practically speaking, long-term deflection will always be on cracked sections. Although anything "cracked" is essential a non-linear problem, but here let's stick to out point of doing linear analysis only.
Now, generally we are not interested in immediate non-cracked deflection. This leaves us with cracked - short-term & long-term deflections in LINEAR analysis.
As you are doing LINEAR analysis in ETABS, you cannot get cracked deflections directly. For this, you may apply stiffness reduction modifier option available in ETABS.
As you are not applying any stiffness reduction modifier, that means, its NON-CRACKED. This is the answer to your question. However, exploring further, if you want to obtain long-term deflection, you can multiply the immediate deflection by a long-term factor given in ACI chapter 9.
-----------------------------
Now comes the non-linear analysis: You can use SAFE for non-linear analysis and get long-term cracked deflections (non-linear) without using modifiers. The cracked non-linear analysis in SAFE will give you long-term cracked deflection which will depend on the extent of cracking which will depend on the reinforcement which will depend on the moment applied. This moment again will depend on the stiffness of cracked section including the reinforcement. So you see, its a non-linear iteration problem.
To read further about, linear vs non-linear and elastic vs inelastic analysis, please refer to the book 'Modelling for structural analysis' by Powell.
 
 

I was browsing through my archives are noticed a bunch of articles written by NICEE (National Information Centre of Earthquake Engineering (NICEE) was established in IIT Kanpur with the mandate to empower all stakeholders in the building industry in seismic safety towards ensuring an earthquake resistant built environment. NICEE maintains and disseminates information resources on Earthquake Engineering. It undertakes community outreach activities aimed at mitigation of earthquake disasters. NICEE’s target audience includes professionals, academics and all others with an interest in and concern for seismic safety).
The articles are free to publish as long as original content stays unchanged. These articles are good for fresh structural engineers and Civil/ Structural Engineering Students. The best thing about them is that they are only 2 pages and full of images. It literally takes less than 5 min to go through each.
 
EQTip19.pdf
EQTip20.pdf
How architectural features effect buildings.pdf
How buildings twist during earthquakes.pdf
How do Beam-Column Joints in RC Buildings Resist Earthquakes.pdf
How do Brick Masonry behave during Earthquake.pdf
How do Columns in RC Buildings Resist Earthquakes.pdf
How do Earthquake Affect Reinforced Concrete Buildings.pdf
How Flexibility of Buildings affect their earthquake response.pdf
How the ground shakes.pdf
How to make building ductile for Good Seismic Performace.pdf
How to make Stone Masonry Buildings Earthquake Resistant.pdf
How to Reduce Earthquake Effects on Buildings.pdf
What are magnitudes and intensity.pdf
What are seismic effects on structures.pdf
What causes earthquake.pdf
What is seismic design philosophy of Buildings.pdf
Why are Buildings with Shear Walls Preferred in Seismic Regions.pdf
Why are horizontal bands necessary in masonry buildings.pdf
Why are Open Ground Storey Buildings Vulnerable in Earthquakes.pdf
Why are Short Columns more Damaged During Earthquake.pdf
Why is vertical reinforcement required in masonry buildings.pdf
Why should Masonry Buildings have simple Structural Configuration.pdf

Yeah. I always use to amaze who is funding this website except you sir. It really need fiances, time and extreme effort to arrange and manage such a website having a good interface along with updating options of social world. It is really good sir. You have initiated a chain and it is really making change in Pakistani community of engineers who rely on internet a lot for learning. We try our level best to spread this forum as much we can. At end, heartily thanks to the moderators and all other members of the forum who are sharing their knowledge and time with people.
Thanks.

it is good idea, even if limited ads for members is required to compensate the self supported forum site .

All,
Starting today, I would be experimenting with some advertisement options on the forum. That would include making ads visible to guests (non-registered members) only. It would also help me estimate the amount this site can pay for itself. Right now, the estimated projections are very low in-terms of revenue (5-10% max of yearly budget). Members would always see a clean forum (no ads).  Guests, however would be subjected to Ads.
Any suggestions or ideas are welcome.
Thanks.
 

Last month, i design a structure with shear walls. I will attach more documents. What i know/remember i will share with you.
In simple, Pier is similar to column and Spandrel is similar to beam. Shear wall is modeled in etabs as shell element. You are to assign it either pier label or spandrel label (Depending on situation of shear wall) to design a shear wall. If you want to design a shear wall, it mostly needs peir label to be assigned. But for the portions of shear wall above openings, as its behavior is somewhat like beam resting on two supports, you need to assign it a spandrel label. I have attached screen shots of my model where you can see i have assigned pier label to the vertical elements and i have assigned spandrel labels to the elements spaning horizontally above openings. The reason behind is detailing based. The detailing in vertical elements of shear wall is similar to wall (or column) and its design is based on considering it as an element resisting majorly AXIAL FORCES +  MOMENTS along with inplane shear forces. (Theoratically it acts as a cantilever beam spaning vertically which again represent behavoiur similar to column). I have also attached screen shot of design detail of pier which reports total vertical steel in wall with respect to section area for resisting moments, horizontal steel for resisting shear and some times boundry elemtns (i.e. special detailing at ends of shear wall exactly as in column i.e. shear rings confining vertical bars). I have also attached screen shot of design detail of spanderal which reports top steel, bottom steel, to resist moments similar to beam and vertical steel to resist shear along with DIAGONAL reinforcement some times needed to account for reversal of forces.
I will attach more documents throwing detailed light on shear wall design i found few weeks ago. Also my model is attached (it is in seismic zone 4 from where you can get idea about pier labeling and spanderal labeling)
One important thing is that, pier label and spanderal label also meant to integrate forces. i.e. if you assign same pier label to all walls in a floor connected with each other, the software will report results only for one and critical wall because all walls were assigned only one pier label. If you want to have multiple outputs at multiple walls, you should assign them different pier label.
in image number 5, note that i have not assigned any pier to the selected portion of wall. hence no reporting of results is done.
 





Etabs Center Portion.e2k

A very interesting and explanatory document along with example..... 
design of dome.pdf

A very interesting and explanatory document along with example..... 
design of dome.pdf

After running the analysis, one way is to look for the symbol that is used for displaying the deformed shape of your structure. The deformed shape will be displayed against a load case, or load combination. Once you have deformed shape, right click on the node where you want displacements.
Limits are already discussed in the forum. Use the search facility, either on google, or in the forum.

Shake table test for Buckling Resistant Braced frame is conducted in NEDUET today at Department of Earthquake Engineering.

Assalam o alaikum,
There is a job opening for structural draftsman in Kashif Aslam and Associates, Lahore, with minimum of 3 to 4 years of experience in structural drafting. Interested candidates may send their CV at waqas.haider@kaa.com.pk
Please forward to the concerned person in your circle also.
Thanks.

Assalam o alaikum,
There is a job opening for structural draftsman in Kashif Aslam and Associates, Lahore, with minimum of 3 to 4 years of experience in structural drafting. Interested candidates may send their CV at waqas.haider@kaa.com.pk
Please forward to the concerned person in your circle also.
Thanks.

I think its time now to categorize questions based on the difficulty level.
For example;
A toddler asking very basic question like what is mass source or time period, should be classified under lets say Easy or 0 or Beginner or Simple etc category. And as such specific moderators should be assigned to take care of that forum.
Then we can make other sections like moderate or difficult. Where one really need to relearn/review the question and think about the answer carefully.
I think all the internet is full of the same basic questions like time period, base shear etc. Isnt it the time to take SEFP a step ahead and not just another forum full of the same basic questions? How can we re-categorize the SEFP sections to give it a new feel, not just like concrete, steel, software issues etc. What do you think?

Dear waqar saleem,
 
Here are my 2 cents:
 
1. Section 21.5.3.2 of ACI 318-08 deals with flexural members i.e., beams and NOT columns. In case of columns of SMRF, ACI section 21.6.4.3 is applicable.
 
2.  For calculating the tie spacing, the applicable member parameter is 'minimum member dimension' of the column, which is 12 inches in case of 12"x15" column. So, the  controlling tie spacing for seismic zone 3 will be 12"/4 = 3" (and, NOT 2.625", as calculated in your post.)
 
3. A column tie spacing of 3" has generally no problem in concreting, even if commonly used nominal maximum aggregate size of 3/4 inch is used. I frequently use this spacing in concrete columns, for buildings located in seismic zones 3 & 4 areas, without getting a single complaint due to closeness of ties.
 
4. As clarified in the commentary section R21.6.4.3, this maximum tie spacing is for confinement of concrete, rather than for shear. As such, use of a larger size tie bar would not help increase required spacing of ties in case of an SMRF.
 
IMHO, The only parameter that may be helpful in increasing the required tie spacing, is the 'smaller dimension of the column'.  However, in a double storey building, I do not see a need to increase smaller dimension of the column beyond 12", solely for providing ties at a spacing larger than 3".
 
Regards.

Special seismic data in ETABS, is used for the enhancement of normally calculated seismic forces, in specific conditions as required by Division IV of Chapter 16, or Chapters 18 through 23 of UBC-97.
 
Inclusion of special seismic data, results in the use of special seismic load combinations of UBC section 1612.4, for the design of structural members. Parameter 'Em', used in these special load combinations, is described in section 1630.1.1 of the code. 
 
Generally, special seismic load effects should be included in ETABS models, for all those structural elements for which the code (UBC) requires the use of special seismic load combinations of section 16.12.4.
 
According to Division IV of UBC Chapter 16, special seismic load combinations are to be used in following cases, among others:
a. For elements supporting discontinuous systems, as described in Section 1630.8.2.
b. For collector elements, splices, and their connections, in accordance with Section 1633.2.6.
 
 
Regards.

You can assign end releases for moment to beam connecting at a joint with column, for that joint specifically. This will model the end condition transferring all the forces except moments from column to beam end.

CSI SAFE also has a Detailer. You may export ETABS results to SAFE and using the commands available under its 'Detailing' menu option, it will prepare structural drawings for you. You may give it a try to see whether it fulfills your requirements or not.
Regards.

Dear Umar
Thanks for your reply well i am gonna look into that auto line constraint i.e. what it does.
but i resolved the issue some other way around. this is what happened.
1. When i selected all shell objects to mesh them. it so happened that etabs also selected the slab in which i had marked opening. and after the meshing was done etabs subdivided the opening too.
2. when i selected all shell objects to apply loads etabs selected the opening too and applied load on it as well.
so when i ran the model check i found the slab label in which problem was present and well it was the opening and etabs could not transfer the load there.
so that was the problem.
Solution : i deleted the subdivided (Meshed) opening therefore the load applied on it was also gone. then i created the new opening. and there is not warning now..
 
Thank you again for replying 

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.
 

Yes you are right. If loading direction is X, check x displacements on point 1 and 2 on the edge that is perpendicular to loading direction.
Following will clarify;
1. Load in Y Direction
Source: FEMA; https://c.ymcdn.com/sites/www.nibs.org/resource/resmgr/BSSC/Topic09-SeismicLoadAnalysis.pdf

and
2. Load in X direction: Source: Reinforced Concrete Design by Tranath

"Ever since strength-level (as opposed to service-level) design earthquake forces were introduced in the 1997 Uniform Building Code (UBC), as indicated by a load factor of 1.0 on E in strength design load combinations, it has been required that drift computations be done directly under those strength-level forces. The drift limits were adjusted accordingly. You never reduce the strength-level design earthquake forces to service-level forces for the purposes of drift computation. This is true of the 1997 UBC, all editions of the IBC, and all editions of ASCE 7 since 1993." 
My original post is referring to use strength level load combos in the light of justification provided. In addition to that, using dead and live loads with earthquake is a good idea as they cover any lateral deflection due to gravity load (mostly observed in non-symmetric frames) which wouldn't be accounted if only earthquake load case is used. 
Thanks.
 

Inter-story drift limitation is intended to limit the damage. Abs disp of max point of upper stories wrt to base is to check for seismic separation. Both checks are must.

Good article; I will throw my two cents.
Seismic drift values are much larger than wind values. UBC uses maximum inelastic response displacements rather than the design level displacements to verify the performance of the building. As stated above, the seismic drift limits are 2% & 2.5% of the story height for long and short -period buildings. So, for a floor to floor height of 12 feet the max. allowable inelastic drift value would be 2% of 12 feet= 0.02*12*12inches=2.88 inches. For wind for a 12 story height, drift would be L/400=12*12/400 =0.36 inches, A comparison of both wind and seismic drift limits shows that earthquake inelastic displacements are quiet large compared to wind displacements. That is why proper detailing is emphasied in seismic design.
Moreover, when calculating ΔS for seismic, make sure:
you have included accidental torsion in your analysis. use strength design load combinations: 1.2D + 1.0E + 0.5L & 0.9D + 1.0E You are using cracked section properties for reinforced concrete buildings. Typical values are Icr walls= 0.5EcIg, Beams = 0.5EcI g & for Columns 0.5 - 0.7 EcIg.

Divide the structure into blocks with regular shape (like center portion with open yard being a block separate by joint). The multipurpose hall (only this has basement??? provide more sections) so separate it from rest of building. Then analyze and design it like regular frame structure for zone 4 and steady the results. Only then you can go for Shear Walls.