UmarMakhzumi

For a non-structural member attached as cladding, unless limits or drifits are specified by vendor brochure, you are left with wind code provided limits only as your criteria. You also need to make sure that your wind loads are reasonable. Your loading looks high to me. Plus your are looking at displacements where as limits are imposed for drifts. As long as you are satisfying code specified criteria your checker cant say anything, i still think he wants you to do what I posted above in the pdf.

You need to see the vendor catalogue for the attached aluminium louvers to see what displacements do they specify. In absence of that, you can use wind inter-story drift limits for cladding attached to columns.

Yasir, like posted above the max midspan for element is controlled by the maximum deflection acceptable at that point by attached non structural member. What I cann't understand is that why are you checking max deflection at midspan when your checker is asking you to satisfy interms of story drifts?

Yeah thats a good observation. But Asad wants to model as-is. If he moves the column he can lose his accuracy on other things. Nothing is wrong, structural engineering is like that. "Structural engineering is the art of molding materials we don't wholly understand, into shapes we can't fully analyze, so as to withstand forces we can't really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance." ...James E. Amrhein - Masonry Institute of America (Retired) LQEngineer (talk) 03:58, 1 September 2009 (UTC)

Yasir, see the attached file. Make sure, your wind & settlement are in one direction. In the attached sketch, I didn't have enough space to draw everything systematically, so I just randomly drew stuff. Your settlement at C should be Delta 1 + Delta 2 Make sure you run all your combos for wind @Sir Zeeshan, I think his checker wants him to calculate the effect of story drifts on the member itself. Same as we used to talk about designing members that not part of lateral force resisting system but are attached to lateral force resisting system, and will undergo a delta equal to story drift that will induce moment & shear in them. SEFP yasir.pdf

Yasir, post a image of your complete frame, identifying the column you are talking about. What kind of lateral force resisting system you have? Generally, for columns, drift is checked at the story of interest rather than deflection at midspan; so you can not do a correlation by modelling it as a beam. Anyhow, what is your utilization of the column? And are there any beams framing in to the column at different levels? Post images so that situation can be assessed. Also post member sizes. About the wind: what is the difference of your manual calculations from software generated total wind load? Post calculations.

1) Inter-story drift limit depends upon type of lateral loading, i.e., wind and seismic. The following two articles explain how to check them for both kind of lateral loading. http://www.sepakistan.com/topic/1341-ubc-seismic-drift-limits/ http://www.sepakistan.com/topic/109-building-drifts-in-etabs/ Maximum deflection are allowed based on codes too. A Column with axial load and later loading is a beam-column. You can use a limit of L/360 as per UBC for that. This is for local member. For overall structure, you need to satisfy wind and seismic limits. See the links above. 2) Yes it does and no it doesn't. There is a trade off between pinned and fixed support and both have reasons for that e.g., impact on foundation. You as a engineer should value reasons, then analyze the same type in the model and finally make sure your connection is fabricated so that what you idealized is real too. Also, you need to see your framing to see what kind of connection would serve best. 3) To some extent it is what you are saying. If you assume pin, your anchor bolts need to be inside flanges along the webs as you wouldn't develop any moment in base plate. So your base plate wont be that thick. If you go other way, your base plate would be thick with stiffeners and anchor bolts located outside to make that happen. But, assuming pin or fix will have an impact on frame member sizes. It is not just location of anchor bolts. You quantity of steel may bump up if you move from fix to pin and vice versa depending upon framing. 4) Wind should be same for both types. I have done both and my drifts were same. Check your calculation and do a comparison of shears and drifts to see you calculated forces correctly.

Could your tell us about details of the structure? There is no pure frame action in the longitudinal direction except for 1 bay. Is this thing tall? Thanks

Line loads are better than slabs. You don't really need to model slabs. Just assign all kind of loading and diaphragms manually. Have you meshed your walls? From the image posted above by asadishaq, I can see that they aren't. And that is infact 1 reason you are having very high reactions under shear walls, as loads are concetrated at two points just under walls, where, infact there should be quiet 'linear'. Do that, and we will look at the next step.

I would not. Should be modelled as spandrels. Plus I would not use columns at end of walls too. For me, the bad thing is that I don't have access to Etabs anymore. Here in my office, I can only use SAP2000 and Risa3d. I thought I could import the $et file but looks like you need a seperate file to export from ETABS for SAP2000. Anyways, as posted above by AQ, the building is wide spread, and making cores shear walls would end up drawing more torsion. AQ: Can you please upload framing, showing what column sizes you are using? Thanks.

Yes, you can upload in these formats.

See the attached image. Is your system clean? The only thing that comes to my mind is that my AV doesn't let it open. I cann't turn it off as I am at work. You should always design your structures for every possible limit state. Unless you "calculate" both wind and seismic, you cann't ignore any load & there is no thumb rule to include or exculde wind or seismic as both depend on different parameters. For the sake of argument, if we say that seismic controls for a high category tall buildings, you will be surprised that some members in your structure would be goverened by wind. So do both. Please post your summary output file from Etabs.

Can't open up the zip file ? @Waqar, he might be doing that becuase of the basement.

You can use recommendation of UBC or ACI. My numbers are from Table 6.5, FEMA 356.

Salam Everyone! We are a steadily growing community now. I thought about posting forum rules which are always a good idea to keep new members streamlined to forum decorum. Please do share your thoughts on any modifications to the rules. Read the forums rules and guidelines before posting for the first time. Please use first names to address people & don't address anyone with a prefix. Calling someone Sir is prohibited. Search the other posts to see if your topic is already covered. Use a meaningful title for your thread and topic tag. Do not use a forum to promote your product, service or business. Be civil. Personal differences should be handled through email or IM and not through posts displayed to everyone. Stay on topic. Ignore spammers, respond to them personally and not through the board, or report them. Use plain text over HTML if you want your post to be readable by everyone. In order to be understood by most people, use correct spelling, grammar and avoid slang unless you know the word or phrase will be understood by other members. Do not double post (post the same message twice in one thread) or cross post (place the same message across several forums). Act in a give and take manner; help others as often as or more than you ask for help. Do not use all caps or SHOUT in your posts. In addition, one exclamation point is enough. When replying to a post, do not quote more from the previous post than you have to. Do not post new problems on someone else's thread and interrupt a topic of discussion. Do not use someone else’s thread for a private conversation. SEFP prohibits warez, cracks or illegal downloading of software and similar topics. Watch your sense of humor, posts may be read by people from a variety of backgrounds and ages. Do not use a huge and annoying signature, a modest signature is fine, moderators may remove large ones anyway. Do not post any information that you want private. Posts should not contain personal, identifiable information or content embarrassing to others. Do not post content that violates a copyright. Do not post ”empty” or useless responses, such as just ”lol” or ”cool.” Only post responses when you have something to contribute. Write concisely and do not ramble. Do not use words like ”urgent” or ”important” in your subject line, be patient. Post stuff on the forum rather than sharing through other means(email etc). If your desired attachment type is not supported, inform the moderators so that changes to board can be made. You can always zip files and upload them. Do not chastise newbies.

*SEFP Consistent Design* *UBC Seismic Drift Limits* *Doc No: 10-00-CD-0003* *Date: June 04, 2013* The goal of this tutorial is to demonstrate how to evaluate building drifts and story drifts using UBC 97 guidelines. The philosophy behind Story Drift Limits is “Deflection Control”; In UBC 97, deflection control is specified in terms of the story drift as a limit on the lateral displacement of one level relative to the level below. The story drift is determined from the maximum inelastic response, ΔM. Let’s start by defining the design-level response displacements. The elastic deflections due to strength-level design seismic forces are called design-level response displacements. These are denoted by ΔS, where the subscript ‘s’ stands for strength design. Design level response displacements are what you get out of your software, when you run analysis. Please note that structural analysis softwares may provide these values in different formats; say a percentage of height or a direct output. Well, to calculate your story drifts, first you need to find maximum inelastic response displacements from your design-level response displacements. The maximum inelastic response displacement is defined as: ΔM = 0.7RΔS Where, R is the structural system coefficient, the subscript ‘m’ in ΔM signifies that we are calculating a maximum value for the deflection due to seismic response that includes inelastic behavior. 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. Seismic drift limits are 2% & 2.5% of the story height for long and short -period buildings. For a floor to floor height of 12 feet the max., allowable inelastic drift value would be 2% of 12 feet= 0.02*12*12 in=2.88 in. 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 emphasized in seismic design. 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. Use a reliability/ redundancy factor= 1 to calculate seismic forces. Whenever the dynamic analysis procedure of §1631 is used, story drift should be determined as the modal combination of the story drift for each mode. Determination of story drift from the difference of the combined mode displacements may produce erroneous results because maximum displacement at a given level may not occur simultaneously with those of the level above or below. Differences in the combined mode displacements can be less than the combined mode story drift. Example: A four-story special moment-resisting frame (SMRF) building has the following design level response displacements.(See attached Image) R= 7.0, I= 1 Time period= 0.6 sec (See the attached image for Story Information) Calculate: Maximum Inelastic response displacements. Story drift in story 3 due to ΔM. Check story 3 for story drift limit. Maximum Inelastic response displacements ΔM = 0.7RΔS ΔM = (0.7) (7) ΔS = (4.9) ΔS (See the attached image for Maximum Inelastic response displacements) Story drift in story 3 due to ΔM Story 3 is located between Levels 2 and 3. Thus ΔM drift = 5.39 - 3.43 = 1.96 in. Check story 3 for story drift limit. For structures with a fundamental period less than 0.7 seconds, §1630.10.2 requires that the ΔM story drift not exceed 0.025 times the story height. For story 3: Story drift using ΔM = 1.96 in. Story drift limit = 0.025 *(12*12) in = 3.6 in. > 1.96 in. Therefore, Okay.

*SEFP Consistent Design* *1997 UBC vertical earthquake term* *Doc No: 10-00-CD-0002* *Date: May 30, 2013* *Article is ripped: Good one to share though* For Strength Design, Ev has the effect of increasing compression and tension/uplift effects on vertical load carrying systems. Ev is not applicable for Allowable Stress Design. The new term, Ev, was introduced in the 1997 UBC. UBC Section 1630.1 defines Ev as the load effect resulting from the vertical component of the earthquake ground motion. For Strength Design, Ev is defined as 0.5CaID. For Allowable Stress Design, Ev is defined as 0. Ca= seismic coefficient from UBC Table 16-Q I = importance factor from UBC Table 16-K D = dead load UBC Section 1630.1.1 defines the earthquake load, E, as the earthquake load on an element of the structure resulting from the combination of the horizontal component Eh and the vertical component Ev. E = Rh*Eh + Ev (UBC 30-1)Rh= redundancy factor defined in UBC Section 1630.1.1Eh = earthquake load resulting from either the base shear, V, or the design lateral force, FpSubstituting the definition of Ev into this equation results in:E =Rh*Eh + 0.5CaID (Modified 30-1)The 1997 UBC defines load combinations in Section 1612. Strength load combinations 12-5 and 12-6include E.1.2D + 1.0E +(f1L + f2S) (UBC 12-5)0.9D (1.0E or 1.3W) (UBC 12-6)Substituting modified equation 30-1 into these equations results in:1.2D + 1.0 Eh + 0.5CaID + (f1L + f2S) (Modified 12-5)(0.9 + 0.5CaI)D + Eh (Modified 12-6a)(0.9 - 0.5CaI)D - Eh (Modified 12-6b) All terms with Eh are effects of horizontal earthquake components. These loads can be in any direction, for example, vertical loads on rigid frame columns, horizontal loads on columns, and diagonal loads on braced frames. Similarly, all terms with D, L, or S are effects of vertical loads or components. These loads can be in any direction, for example, vertical loads on beams, horizontal loads on rigid frame columns, and diagonal loads on braced frames. Example:For typical California values of Ca = 0.40 and I = 1, the modified equations become:1.4D + 1.0Rh*Eh + (f1L + f2S)1.1D + Rh*Eh0.7D + Rh*Eh The impact of the vertical earthquake component on modified Strength Design equations 12-5 and 12-6a is to increase compression effects on columns and foundations. The impact of the vertical earthquake component on modified Strength Design equations 12-6b is to increase tension and uplift effects on columns, anchorage, and foundations. There is no impact of the vertical earthquake component on Allowable Stress Design load combination equations.

Good question. I see Engineering Ethics more than just applied ethics and system of moral principles for engineering. It is a detailed subject. Here in Canada, they stress on Engineering Ethics & Construction Law; infact you have to take an exam for Engineering Ethics before obtaining your Professional Engineer designation. Understanding of ethics helps a lot in understanding your liabilities as an engineer too.

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.

See this: SEFP Consistent Design: Design for Torsion

*SEFP Consistent Design* *Torsion: Reinforced Concrete Members * *Doc No: 10-00-CD-0001* *Date: May 24, 2013* Torsional forces, generally speaking, occur in combination with flexural and transverse shear forces. From a design perspective, we need to understand difference between two torsion types: Compatibility Torsion Equilibrium Torsion Compatibility Torsion Compatibility Torsion is when a member twists to maintain deformation compatibility; its induced in structural members by rotations (twists) applied at one or more points along the length of member. The twisting moments induced are directly dependent on the torsional stiffness of the member. These moments are generally statically indeterminate and their analysis necessarily involves (rotational) compatibility conditions(click on the image to enlarge). For the floor beam system shown above, the flexure of the secondary beam BD results in a rotation ǾB at the end B. As the primary (spandrel) beam ABC is monolithically connected with the secondary beam BD at the joint B, deformation compatibility at B implies an angle of twist, equal to ǾB at spandrel beam ABC, and a bending moment will develop at the end B of beam BD. The bending moment will be equal to, and will act in a direction opposite to the twisting moment, in order to satisfy static equilibrium. The magnitude of ǾB and the twisting/ bending moment at B depends on the torsional stiffness of the beam ABC and the flexural stiffness of beam BD. Now here is the fun part, the torsional stiffness of a reinforced concrete member is significantly reduced by torsional cracking. So, if you don’t design your spandrels for compatibility torsion, they will crack, increasing ǾB and reducing the induced twisting moment. To paint the same picture while using ETABS, set your torsional stiffness of the main beam to zero. This will also increase the amount of flexural reinforcement in your secondary beams. Moreover, considering design practice in Pakistan (since we never design beams without shear reinforcement), compatibility torsion can be ignored for regular structures, as minimum shear reinforcement in most cases would stand up to cracking torque. From ACI 318 commentary R11.6.1, Do note that there are some situations (such as circular beams supported on multiple columns) where both equilibrium torsion and compatibility torsion coexist. Also, eccentrically loaded beams, member curved in plan, and member of space frames will be subjected to torsion. See the attached “Timesaving-TorsionDesign-IA.pdf” as a go-by. Timesaving-TorsionDesign-IA.pdf Equilibrium Torsion In simplest words, Torsion is a limit state in this condition; a structure is subjected to equilibrium torsion when it can maintain equilibrium only by resisting the torsion. In such a case, torsional moment cannot be reduced by redistribution of internal forces since the torsional moment is required for the structure to be in equilibrium. From ACI- 318 (click on the image to enlarge). Moreover, see the structures below that defy gravity when subjected to different kind of loads by standing up to equilibrium torsion. Overall Building Torsion For overall building torsion, the torsional effects can be minimized by reducing the distance between the center of mass and center of rigidity. Center of Mass is the point where the mass of an entire story is assumed to be concentrated. The center of mass is crucial as the location of seismic force at a particular level depends upon it. The distance between the Center of Mass and the Center of Rigidity should be minimized, but may not be possible due to building geometry. Invariably, effects of torsion are present in at all buildings although analysis may show that in some buildings torsional effects are negligible.

@AQ, SAP has a template for water tanks. You can do it manually too using above quoted document. What load combos are you planning to use? You won't have 100% live with earthquake. FYI; In water tanks, sloshing acts to dampen vibrations of the water tank in an earthquake.

You can use this to design water tank walls. http://www.sepakistan.com/topic/16-rectangular-concrete-tanks/

Salaam All, Looking forward to develop a series of articles under the title of "SEFP Consistent Design". The aim is to provide simple and lucid examples for our Pakistani Engineers that use UBC 97; examples will serve as quick reference and try to clarify misconceptions prevalent in design offices. Anyone, who would like to volunteer on this is most welcome. As the name indicates, "consistent design" is meant to spread common understanding of complex code clauses that a design engineer faces on a day to day basis. e.g., calculating story stiffness, or designing a flexible diaphragm. Examples would be pure, and written by authors with copyrights to SEFP. Current target is to have at least 2 examples published per month. I hope this will help young engineering to develop a rock-solid understanding and design the right thing rather than saying yes to whatever they are told to follow.That's my goal. Any ideas, input, volunteering in appreciated. Thanks.

Good Job Rana!