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Top content from across the community, handpicked by us.
Forum Update
UmarMakhzumi posted a topic in Website Announcements/ Problems/ Login/ Registration Issues,
The forum has been updated today with a lot new features.
You can find the list of all the new improvements by visiting this website.
Some highlights are:
1) Improved Search Features
2) Emoji
Emoji support is now available in all editors.
Do check out the link posted above for the complete list.
One additional announcement that I would like to make is that with reference to last forum update post (read below), @Rana and @BAZ are forum Admins now. I think it was important to do as it brings more transparency for the forum and also helps spread the responsibility. The forum belongs to the members so it never made sense for one person to be Admin,
As always, feedback is much appreciated.
Thanks for taking the time out to read this update.
Cheers!
 2 replies
Crack Width For Watertight Requirements According To Aci
Rana posted a topic in Concrete Design,

Normal structures

1. ACI 31895 based on statistical method of Gergely & Lutz 1968 limits Z based on exposure. We are calculating crack widths here. (Normal structures)
2. ACI 31899 proposed limiting the spacing and removed actually calculating the width and also removed the exposure conditions. For example for beams and oneway slabs s (in) = 540/fs 2.5cc or in other words limiting the fs=0.6fy (For normal structures)
3. ACI 224R01 references method 1 and 2 above and 3 european codes.
The most confusing part is the table in which Nawy suggests 0.1mm crack width for watertight structures. The whole document is for normal structures except this line. And people are following this line and refer to this document for water tight structures. I mean its just a suggestion and by the way this method 1 is obsolete now since ACI 31899 (see point 2 above).

Water tight structures

1. ACI 31808 states clearly that for watertight structures ACI 35006 codes should be used.
2. ACI 224.4R13 also specifically states that for watertight structures walls in section 7.4, we should use ACI 35006.
3. ACI 35006 for water tight structures does not recommend calculating a number for crack width but rather limiting max steel stress in bars to be 20k ksi or fs=0.33fy for normal conditions.

To sum it up,
Philosophy of crack width control is not to calculate probable crack widths but to limit the max stress in steel bars.
For normal structures: fs=0.6fy and for water tight structures fs=0.33fy
 1 reply
Diaphragms
Shariful Islam posted a topic in Concrete Design,
I want to know the use of diaphragms in etabs. i discus many people who are use etabs but i can't get justified answer about the application of etabs.
I read the Technical reference of Etabs, where they write about Diaphragms. i get two type of diaphragms (plate or shell and joint or beam).
My question.
1. When do i use Shell diaphragms (if floor present )
2.When do i use joint diaphragms ( grade beam level where no slab are provide)
NB: Diaphragms use to transfer the lateral load to the resisting element ( frame such as column. beam,shear wall)
 2 replies
Pile Design
UmarMakhzumi posted a topic in Journal/ Articles/ Tutorials,
This article is intended to cover design of piles using Ultimate Limit State (ULS) method. The use of ULS method is fairly new for geotechnical design (last decade). The method is being used in multiple countries now (Canada, Australia etc). The following items shall be discussed:
Overview
Geotechnical Design of Piles (Compression Loads, Tension Loads and Lateral Loads)
Structural Design of Piles (Covering both Concrete and Steel)
Connection of Pile with the foundation (Covering both Concrete and Steel)
Pile Group Settlement
Things to consider
1. Overview
Piles provide a suitable load path to transfer superstructure loads to foundation where shallow foundation are not suitable  this can be due to a number of reasons like existing space constraints or suitable soil strata is not present immediately below structure. Other uses can be to meet design requirements like to have reduced settlement etc.
This article shall cover the use of straight shaft castinplace concrete piles and straight shaft driven steel pipe piles. There are a number of additional piles types like belled concrete piles, precast concrete piles, screw / helical steel piles etc but the discussion to choose a suitable pile type is not in the intended scope of this article. The article is intended to discuss design requirements for straight shaft piles only (both concrete and steel) . The aforementioned topic about pile selection is a very diverse subject and requires a separate discussion on its own.
Click on the link to read the full article.
 9 replies
Pile Design For Machine Foundation
Mohammad Yaseen Yousafzai posted a topic in Foundation Design,
I ll appreciate your help in terms of guidance & provision of notes...
Thank you..
 36 replies
Quote from J.G. MacGregor
BAZ posted a topic in General Discussion,
based on an elastic theory which assumes that structures display a linear response throughout their loading history, ignoring the postyielding
stage of behavior. Current design practice for reinforced concrete structures is a curious blend of elastic analysis to compute forces and moments, plasticity theory to proportion crosssections for the moment and axial, load, and empirical mumbojumbo to proportion members for shear.
From the book "Design of Concrete Structures with Stress Fields" by A. Muttoni, J. Schwartz and B.Thurliman.
 0 replies
9th International Civil Engineering Conference (ICEC 2017), December 2223, 2017, Karachi, Pakistan
Fatima Khalid posted a topic in Shout Box,
NED University of Engineering & Technology in collaboration with Institution of Engineers Pakistan (IEP) is organizing 9th International Civil Engineering Conference (ICEC 2017) on December 2223, 2017 at Karachi, Pakistan.
The congress details are available at its website www.neduet.edu.pk/icec
Also attached is congress flyer for information and dissemination among your peers.
Abstracts submission deadline has been extended till October 31, 2017.
Please click on the link to see the full description.
 0 replies
Picked By
UmarMakhzumi,Construction/Cold joint location in RC Column/walls
EngrJunaid posted a topic in General Discussion,
Is it mandatory to do column concreting upto the soffit of the beam in a single pour ?
What code says about the construction/cold joint location in column ?
Majority of the contractors are pouring the column concrete upto the soffit of the beam (full height of the column), some contractors leave the column height about 9" to 12" below the beam level and then fill this 9" to 12" column height with the beams & slab concreting. On one site column concreting was stopped at the mid height and the remaining half was filled on the next day.
Thanks
 5 replies
Shear wall design
farooqbro posted a topic in Concrete Design,
i am facing problems in shear wall design .what are the pier and spandral ?what will be the difference when we assign pier or spandral? without assigning these the shear wall design is incomplete .
i am taking about etabsv16
someone have document about shear wall design plz provide it
thank you
 10 replies
Washigton Accord !!!
waqar saleem posted a topic in Shout Box,
Congratulations to Engineers, PEC has become full signatory of Washington Accord, what are the benefits to Pakistani engineers for this agreement.
Regards
 3 replies
PDelta & Selenderness Effects in ETABS
Ali Shan posted a topic in Concrete Design,
1. If we run Pdelta analysis in ETABS, then should we ignore stiffness property modifiers for beams and columns? I have heard that if we perform Pdelta analysis and apply stiffness modifiers at the same time then the moment magnification process is doubled...?
2. ETABS considers selenderness of a column by applying moment magnification factors. If we run Pdelta analysis also, does it mean that the selenderness of column is being overestimated? I mean once the moments are magnified in Pdelta analysis process and again through moment magnification process?
Please help me understand the software myth and clarify above confusions.
 1 reply
Development Length Of Standard Hooks
Waqas Haider posted a topic in Concrete Design,
According to ACI 12.5.2,
development length for fc' = 3000, fy=60000, for normal weight concrete and epoxy less reinforcement, The required development length comes out to be
for #3 = 8.2 inch
for #4 = 10.95 inch
for #6 = 16.42 inch
for #8 = 21.9 inch
And if in my case, ACI 12.5.3 is not fulfilled, it means now i have to provide ldh as mentioned above. ldh is STRAIGHT EMBEDMENT LENGTH + RADIUS OF BEND + ONE BAR DIAMETER as shown in figure attached. Now my question is, if in my case, main reinforcement of beam is of #6 and #4, minimum column size required will be 18 inch and 12 inch respectively. Lets say by any means, i can not select #4, #3 bars and size of column where bars are to be terminated is 12 inch, how to fullfil this development length???
 11 replies
ShearWall  Temperature Design in ETABS
rummaan17 posted a topic in Concrete Design,
I am trying to design shearwalls through ETABS with temperature load applied over shell. At various location, spandral section fails in Shear due to temperature and piers (sometime in shear, mostly in flexure). (See Attached Image)
Certainly all the problem in Shearwalls are due to temperature. I don't want to increase cross section of spandral or pier at some location just due to temperature load case as it will appears nonuniform with rest of the wall.
I have seen stiffness modifier affect distribution of forces and also rigid/semi rigid daiphragm assumption.
Can anybody guide how to properly design the shear wall with temperature load applied in ETABS or share any similar experience. Thanks in Advance.
 15 replies
Etabs Manual Meshing Problem
mhdhamood posted a topic in Concrete Design,
I WILL LOOSE MY BRAIN FROM ETABS.
I DECIDED TO MAKE MANUAL MESHING FROM AREA ELEMENTS BESIDE EACH OTHER AND EVERY HING WAS FINE .
BUT AFTER DEVISION SAY 7*7 ELEMNTS FOR EVERY BIG ELEMENT AND MAKING ETABS CHECH..................THEN 500 ERROR MESSAGE THAT ALL ELEMNTS ARE CLOSE TO EACH OTHER. WHAT ARE GOING...... SOMEONE TELL ME PLEASE...... I WILL LOST MY WORK
 6 replies
Shear Reinforcement In Etabs
Waqas Haider posted a topic in Software Issues,
I have just designed a frame structure with SMRF. The out put of shear seams weird to me. Column reports design shear Av/s as 0.045. (Images are attached). but when i right click the member, it must show me the most critical case HIGHLIGHTED AUTOMATICALLY. But it highlights load combo 38 (autogenerated combos have been used) which reports Av/s as 0.038. And 0.045 value is at combo 32. Is their any logic behind it?? More over how to interpret this Av/s?? means 0.045 in kipin units means what? How can i convert this into spacing??
 9 replies
Response Spectrum Analysis in ETABS
saleem khan posted a topic in Software Issues,
 5 replies
Problem In Etabs Design Summary
khalid posted a topic in Software Issues,
First of all I would like to express my sincere thanks to the initiators of this forum for establishing such an exceptional atmosphere for knowledge/experience sharing, I it is really useful, In fact since I have found the forum I am mostly online and busy reading the posts. I would also like to thank the members for their professional comments and advice.
As my first post in this forum I would like to ask the following queries:
1After running the analysis and design when I check the DESIGN DATA through Display >> Show Tables >> DESIGN DATA >> Concrete Frame Output, there is no specific message in Column Summary Data and Beam Summary Data, but in Joint summary data it is showing that “Joint B/C check not done”. Does anyone has any idea? I am sharing the ETABS model for your information and easy reference.
ETABS MODEL.zip
2 ETABS provides greater area of steel in the upper column than the column at BASE, perhaps due to higher moment. Could someone explain why this is so? In practice should we maintain maximum steel in both stories? Or we shall follow what the software suggests?
3 Beside considering the minimum thickness required for deflection control of Beam as per Table 9.a Chapter 9 ACI318 , using concrete crack behavior in ETABS and checking story drift, Do we have to check the deflection of beams for the serviceability propose elsewhere in ETBAS? If yes, Could anyone explain it?
Regards, and look forward to any explanation
 13 replies
Etabs/sap2000 Dome Geometry
UmarMakhzumi posted a topic in Software Issues,
 22 replies
Connection Of Truss To Supporting Beam Column
Hasan Tariq posted a topic in Steel Design,
I am designing the mosque in zone 4 . The roof of the mosque is a Truss.I have following questions
1. Do truss rest on the beam ? if yes .? do i have to assign any support conditions ? or etab will selelct by default.
2. what will be the grade of steel for the truss ? yield or tensile strength. some one told me go for A 36 ( 36,58)
 15 replies
Seismic Assessment And Retrofit Design
Ayesha posted a topic in Seismic Design,
6Storey Mixed Use Building in Karachi.pdf
10Storey Office Building in Karachi.pdf
RS4 Storey Academic Building in Karachi.pdf
Five Storey Residential Apartment.docx
Please visit the thread to download the attachments.
 2 replies
Diaphragm Flexibility
BAZ posted a topic in Journal/ Articles/ Tutorials,
*Diaphragm Flexibility*
*Doc No: 1000CD0004*
*Date: August 07, 2014*
I am writing this article about a very important, but mostly neglected topic of flexibility of diaphragm. I used to assume that all reinforced concrete slabs can be treated as rigid diaphragms. But as it turns out, only the slab with spantodepth (depth is length of slab in direction of lateral loads) ratio of less than 3 and without horizontal irregularity can be treated as rigid diaphragm. The more important thing is that the spantodepth ratio and horizontal irregularity is not the only criteria and one other factor also needs to be kept in mind before assigning rigid diaphragm to concrete slabs in numerical model of building.
Another important concept that I learned, and it was a moment of epiphany for me, is about TRANSFER diaphragms. I had posted a topic “Amplification Of Forces In Etabs” earlier in this forum but we were not able to reach at a satisfactory conclusion. Now, I have the answer to that query: Back Stay effect. Another article is required to explain it , and this concept is not discussed in this article. This article is about flexibility of diaphragm.
Diaphragms are horizontal members of the lateralforce resisting system of building structures. Their function is to distribute inertial forces, generated at its own level, as well as other levels, to vertical members of lateralforce resisting system.
One kind of diaphragm only distributes inertial forces generated at its own level. This kind of behaviour is observed in buildings where there is a continuity of vertical members of lateralforce resisting system: building should not have a setback or podium at lower levels, or below grade levels. The other kind of diaphragm, known as “Transfer diaphragm”,
Read more: http://www.sepakistan.com/topic/1480diaphragmflexibility/
 4 replies
KPK Seismic Field Practicing Manual (Urdu)
EngrJunaid posted a topic in Journal/ Articles/ Tutorials,
KPK Seismic Field Practicing Manual is attached.
Field Practice Manual on basics of good construction practices.pdf
Thanks.
Please visit the forum link to download the attachment.
Link: http://www.sepakistan.com/topic/2179kpkseismicfieldpracticingmanualurdu/
 4 replies
1997 Ubc Vertical Earthquake Term Ev
UmarMakhzumi posted a topic in Journal/ Articles/ Tutorials,
*1997 UBC vertical earthquake term*
*Doc No: 1000CD0002*
*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 16Q
I = importance factor from UBC Table 16K
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 301)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 301)The 1997 UBC defines load combinations in Section 1612. Strength load combinations 125 and 126include E.1.2D + 1.0E +(f1L + f2S) (UBC 125)0.9D (1.0E or 1.3W) (UBC 126)Substituting modified equation 301 into these equations results in:1.2D + 1.0 Eh + 0.5CaID + (f1L + f2S) (Modified 125)(0.9 + 0.5CaI)D + Eh (Modified 126a)(0.9  0.5CaI)D  Eh (Modified 126b)
Please visit the forum link to view the complete article.
Link : http://www.sepakistan.com/topic/13391997ubcverticalearthquaketermev/
 4 replies
Comments/Observations regarding modelling in ETABS
BAZ posted a topic in Journal/ Articles/ Tutorials,
*Doc No: 1000CD0006*
*Date: May 06, 2017*
Some of the observations made during extraction of results from ETABS (v 9.7.4), for design of reinforced concrete members, are being share in this article.,
1) Minimum Eccentricity
ETABS always considers the minimum eccentricity for selecting the design moment of columns irrespective of the probable behavior of the column, whether short or long column. See section 10.10.6.5 and its commentary of ACI 31808 which deals with minimum eccentricity of long columns. You should always check the design moments that ETABS uses for columns if you want to bring down the cost of construction.
2) Unbraced/ Braced Preference
ETABS always performs analysis of frame as if it is unbraced. You should investigate if the storey under consideration is braced, or unbraced (10.10.5.2), and decide appropriate design moments of columns.
3) Time Period
ETABS has a tendency to select a time period of the building that is considerably less than the value obtained by the approximate method, Method A, of the section 1630.2.2 of UBC 97. To quote the FEMA 451 document: ''Because this formula is based on lower bound regression analysis of measured building response in California, it will generally result in periods that are lower (hence, more conservative for use in predicting base shear) than those computed from a more rigorous mathematical model". So, there is no need to use the value of time period that is lot less than Ta. One should always check the time period used by the software; ETABS can overestimate the seismic force by more than 2 times.
Visit the forum link to read the complete article.
Link: http://www.sepakistan.com/topic/2300commentsobservationsregardingmodellinginetabs/
 0 replies
Ubc Seismic Drift Limits
UmarMakhzumi posted a topic in Journal/ Articles/ Tutorials,
*UBC Seismic Drift Limits*
*Doc No: 1000CD0003*
*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 designlevel response displacements. The elastic deflections due to strengthlevel design seismic forces are called designlevel 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 designlevel 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.
Visit the forum link to view the complete article.
Link: http://www.sepakistan.com/topic/1341ubcseismicdriftlimits/
 10 replies

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