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Crack Width For Watertight Requirements According To Aci
Rana posted a topic in Concrete Design,
Hi guys just to discuss with you my understanding of crack widths in Environmental structures according to ACI.

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 I mean its just a suggestion and by the way this method 1 is obsolete now since ACI 31899 (see point 2 above).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,
Hi
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,
*SEFP Consistent Design*<br style="color:#272a34">*Pile Design*<br style="color:#272a34">*Doc No: 1000CD0005*<br style="color:#272a34">*Date: Nov 21, 2017*<br style="color:#272a34">
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 am suppose to design a pile foundation for a machine weighing approximately 50 tons and with an operational loading of 100 tons.
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,
Material behavior can be idealized as consisting of an 'elastic' domain and a 'plastic' domain. For almost 200 years, structural design has been
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,
Dear Fellow Researchers, Academicians, and research students,
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
Promoted By
UmarMakhzumi, 
Construction/Cold joint location in RC Column/walls
EngrJunaid posted a topic in General Discussion,
AoA all,
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,
AOA
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,
Salam Members,
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,
Please clarify the following confusions one by one:
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



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