EngrUzair

Wa-alaikum-assalam! Please refer to following thread, to know about the relevant code requirements: http://www.sepakistan.com/topic/1859-special-seismic-data-input-in-etabs/?hl=%2Bspecial+%2Bseismic Regards.

This may be done by increasing resistance to lateral deformation i.e., lateral stiffness of the structural system. Yes. You may also overcome it, by increasing the column size and/or by providing shear walls. Regards.

You will need to increase lateral stiffness of the relevant story in the direction of drift. This may be done by increasing column dimension in that particular direction, providing shear walls or the both. Regards.

If you could provide some photos & sketches about the site situation, it would be easier for the people here, to advise you in a better way. In general, you would also have to check load carrying capacity of existing support structure and foundations, to know whether these are capable of taking the proposed additional load safely, or they will also need strengthening.

Can you upload ETABS Input file (.$ET or .EDB) of your structural model, to see where the problem might be?

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.

I second waqar saleem. IMHO, it would be a better option, in case there are no restrictions to avoid an expansion joint at that location. Regards.

Here are a few links: 1. http://www.engineering-international.com/ (Here you may find spreadsheets for many types of structural calculations, commonly required by a structural engineer in routine design work. For Eccentric Footing, see serial No.2 in Foundation Design Group) 2. https://www.excelcalcs.com/repository/strength/structural-details/rectangular-spread-footing-analysis/ 3. http://www.inducta.com.au/footing.htm Regards.

I second waqar saleem. Keeping in view our normal construction which is either loosely supervised or unsupervised, soil support is never expected to remain under the plinth beams (PB), unless the PB is resting on the masonry with a footing underneath. Therefore, IMHO it is better, rather necessary, to design PB for the full beam span in almost all situations, without bothering about the soil support, Regards.

Very good dig. Thanks for sharing. BTW... Is it not too early to admit such a serious mistake, JUST AFTER 53 YEARS? Regards.

You may look at the following links, among others, for the relevant data: 1. http://www.ngdc.noaa.gov/nndc/struts/form?t=101650&s=34&d=34 2. http://authors.library.caltech.edu/26270/ 3. http://authors.library.caltech.edu/26335/ 4. http://ngawest2.berkeley.edu/ 5. http://www.ngdc.noaa.gov/hazard/smcat.shtml 6. http://worldwidescience.org/topicpages/e/earthquake+accelerograms+digitized.html You may search the internet, in case you do not find the desired data on the above mentioned links. HTH Regards.

IMHO, the solution was not hard at all. Just smoothing of top bearing surfaces of the corbels, and provision of double layer of good quality building paper over them, would have avoided the damage observed.

Following links might help, in this regard: 1. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwi6x8X0pK7JAhUJCI4KHQwdB4kQFggeMAA&url=https%3A%2F%2Fwww.rbkc.gov.uk%2FidoxWAM%2Fdoc%2FRevision%2520Content-1046354.pdf%3Fextension%3D.pdf%26id%3D1046354%26location%3Dvolume2%26contentType%3Dapplication%2Fpdf%26pageCount%3D1&usg=AFQjCNElzOX9GSKGIU3uULq4gIjoOheXeg 2. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0ahUKEwi6x8X0pK7JAhUJCI4KHQwdB4kQFgg2MAQ&url=http%3A%2F%2Fwww.deepex.com%2Fen%2Fsecant-pile-example&usg=AFQjCNEKLh7WVEphHC8mxrsQ5_1sOo38TA 3. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwi6x8X0pK7JAhUJCI4KHQwdB4kQFggkMAE&url=https%3A%2F%2Fwww.ucviden.dk%2Fstudent-portal%2Ffiles%2F9914648%2FFinal_Proj..&usg=AFQjCNGFzo39V25ec7U1gdwLK7NaiY-OWg 4. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&cad=rja&uact=8&ved=0ahUKEwi6x8X0pK7JAhUJCI4KHQwdB4kQFghEMAc&url=http%3A%2F%2Fwww.geobest.nl%2Fdocs%2FDesign%2520and%2520construction%2520of%2520a%2520secant%2520pile%2520wall%2520in%2520Glasgow_paper%2520Athens_2011.pdf&usg=AFQjCNE6elXbUuZFGX_8vcQZEd6jeSZvfg 5. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&cad=rja&uact=8&ved=0ahUKEwi6x8X0pK7JAhUJCI4KHQwdB4kQFghTMAk&url=http%3A%2F%2Fwww.geosystemsbruce.com%2Fv20%2Fbiblio%2F243%2520Design%2520Construction%2520-%2520Cut-Off%2520Walls%2520under%2520the%2520Arapuni%2520Dam.pdf&usg=AFQjCNF-UnJHvYKW_WB5nCHcrjbwiLsOBw 6. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&cad=rja&uact=8&ved=0ahUKEwi6x8X0pK7JAhUJCI4KHQwdB4kQFghMMAg&url=http%3A%2F%2Fwww.fletcherconstruction.co.nz%2FResources%2FSecant_Pile_Retaining_Wall_Construction_in_NZ_(Wharmby%2C_Concrete_Conf.2010).pdf&usg=AFQjCNF1aDjairpcw9TkjbbBJ_PgNn__8Q Regards.

IMO, it is not an error, rather it is a warning message indicating that UBC wind analysis results might not be reliable, if the building being analyzed is more than 400 feet high. This is in accordance with requirements of UBC-97 section 1615, which requires that approved national standards (e.g., ASCE 7 etc), shall be used for wind design of buildings over 400 feet in height, among others. Moreover,AFAIK, you may still run your model (even after display of this warning message), by pressing OK button again and again (although analysis results might not be acceptable). Regards.

I 'm curious to learn more about the expected improvements. However, personally I would like to have your attention to following points: 1. One feature I would like to be added (if not already planned) to the text editor, is user controlled 'Save' button. The present 'auto save' feature, did not work well for me several times in past, as I had to lose considerable data at several occasions (especially in longer posts), because of frequent power outages in our area. 2. It would be better if the user could have control, in setting the time period for 'auto save' function as well. Regards.

Nor to me, keeping in view the fact that Abbottabad is in seismic zone 3, and as the pictures indicate, wall height is not less than 12 ft. It appears that the workmanship during wall construction must have been very good, as the walls have resisted the earthquake jolts in a much better way, not expected from common stone masonry buildings constructed in our country, ordinarily. Regards.

Dear shaker, The information provided by you so far, does not clarify what type of structural system you are using for your building. It is not clear about your structure, whether it is a framed structure (using beams and columns for load transfer), or load-bearing wall system. Moreover, you have not attached Text Input File of your model, therefore my comments are general, and keeping in view the information you have provided, as well as whatever I am able to extract from it. As far as ETABS warning messages are concerned, you may use any of the following approaches: 1. Go to all the locations indicated warnings about, and correct them one-by-one manually. 2. Re-organize your model, as explained in following steps: a. Establish the locations of all the columns and beams, if it is frame-type structure (or slab supports, if you are using a load-bearing wall system). Make sure that your columns properly aligned in each grid along both horizontal axes. That is, all columns in one line or along one grid are exactly in line with each other. (You may verify this by viewing the columns in each grid, using two windows side-by-side, one showing Plan view and the other Elevation views one-by-one.) b. Once all of your columns are aligned, check the grid elevations one-by-one to make sure that all the beams along a grid line are connected exactly to the column joints at both ends. (If you are using load-bearing system, you will need to align all the 'slab edge supports', instead of columns & beams.) c. Now, it would be better to delete the slabs, not aligned with supports or beams, and redraw them carefully, using proper snap options. d. Use auto-meshing options, or if necessary, mesh the slab manually. In manual meshing, you must be very careful in that: (1) Number of elements, selected for each slab edge is such that the element shape is as near to the square shape as possible. (2) There should be preferably even (multiples of 2) elements on each edge. (3) You should have equal number of same width elements, in the length common to two adjacent slabs. (4) End points of adjacent elements on both side of slab edge, perfectly match (VERY VERY IMPORTANT). (5) Dimensions of mesh elements should be within the limits, prescribed by ETABS. I personally like & recommend the second option, whenever there are a lot of warning messages, similar to your case. HTH Regards.

shaker, Your attached image gives a very strange look, as it does not appear to have a regular pattern of supports for slabs. Moreover, I don't see any kind of regular building frame system in it. What kind of structure it is? Can you attach text input (.$ET) file of your model?

Can you share some details about your model here? For example, images of meshed roof to see what type of slab arrangement it is, and how you have meshed it.

Wa-alaikum-assalam! Yes. For reference, see section 2.9 and Appendix B of the Concrete Frame Design Manual of ETABS for ACI 318-08. 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.

For seismic zone 2B and RCC, you may adopt Concrete 'Intermediate Moment Resisting Frame (IMRF)' for your building, with an R value of 5.5. This would require RCC member detailing as per section 21.3 of ACI 318-08. Alternately, you may also adopt 'Special Moment Resisting Frame (SMRF)' system for you structure. However, it would require a more stringent detailing, in accordance with ACI code Sections 21.5 onwards. Regards.

Wa-alaikum-assalam, Dear Mubeen, Selection of the structural system for a building would generally depend upon the seismic zone or category of the area where building is to be constructed and the preferred material of construction. For a B+G+5 building with Reinforced Concrete as preferred material of construction, my obvious choice would be a Concrete 'moment resisting system (MRF). Which MRF (IMRF, SMRF etc) would actually be used, will depend upon the selected 'Lateral Force Resisting (LFR) System' corresponding to the seismic design category (or seismic zone) of the area, and the code (UBC-97 in the present case) requirements / restrictions applicable for that area. Value of overstrength factor 'R', would correspond to the 'LFR System', adopted for the building. Types of various Building Systems, LFR Systems, their corresponding R values and restrictions on the use of these building / LFR systems are available in Table 16-N of UBC-97. BTW... Where is you building located? And, what is your preferred material of construction. Regards.

omar, Load path for a structure is decided by the structural engineer, and it depends upon which kind of structural system, he or she (the structural engineer) selects for the building under consideration, in order to properly transfer the design loads from the slabs to the ground. Generally speaking, there are two types of structural systems you may adopt for your building; a load-bearing wall system, or a moment resisting frame system. In load-bearing wall system, your gravity loads are directly supported by slabs, resting on load-bearing walls (or isolated beams, provided to divide larger slabs to suitable size smaller slabs, for economical design of slabs). The beams, if provided in this system, also transfer the slab loads to walls, which in turn transfer these loads to the footings, resting on ground. In this case, your load path will be: Slabs to Walls (or beams, if provided), Walls to footings & footings to ground. On the other hand, if you opt to adopt a moment resisting frame system, the slabs will transfer loads to beams provided along the slab edges, beams will transfer loads to columns (instead of walls) and the columns (rather than walls) transfer the loads to footings, to be finally supported by the ground. In this case, your load path will be: Slabs to beams, beams to columns, columns to footings & footings to ground. Regards.

shaker, IMO, you should check values of maximum outdoor and maximum indoor temperatures for Dubai, from the internet (or some other authentic source), and use them for the top and bottom faces of the slab, respectively. Alternately, 'Record high' and 'Record low' temperatures from the following source, may also be used for the purpose : https://en.wikipedia.org/wiki/Climate_of_Dubai Regards.