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Hi guys just to discuss with you my understanding of crack widths in Environmental structures according to ACI. --------------------------- Normal structures --------------------------- 1. ACI 318-95 based on statistical method of Gergely & Lutz 1968 limits Z based on exposure. We are calculating crack widths here. (Normal structures) 2. ACI 318-99 proposed limiting the spacing and removed actually calculating the width and also removed the exposure conditions. For example for beams and one-way slabs s (in) = 540/fs -2.5cc or in other words limiting the fs=0.6fy (For normal structures) 3. ACI 224R-01 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 water-tight 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 I mean its just a suggestion and by the way this method 1 is obsolete now since ACI 318-99 (see point 2 above). --------------------------- Water tight structures --------------------------- 1. ACI 318-08 states clearly that for watertight structures ACI 350-06 codes should be used. 2. ACI 224.4R-13 also specifically states that for watertight structures walls in section 7.4, we should use ACI 350-06. 3. ACI 350-06 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

Thanks Dear Waseem and Umar................... I ll add a picture soon................

Wa-alaiku-assalam! Here are a few start points: 1. ACI 318-08 sections 11.11.6 and 13.4 deal with openings in slabs. Openings in structural diaphragms are discussed in section 21.11. 2. Effect of openings in slabs on shear strength, has been elaborated in chapter 16 (Page 16-11) of PCA Notes on ACI 318. Whereas, effect of openings on flexural strength has been explained in chapter 18 (pages 18-6 to 18-8) of PCA Notes. 3. Have a look at the following documents: a. https://www.structurepoint.org/publication/pdf/PCA-Concrete-Floor-Slab-Openings.pdf b. http://cement.org/buildings/tech_note_floor_openings.pdf c. http://mak.ac.ug/documents/Makfiles/aet2011/Tayebwa.pdf d. https://pure.ltu.se/ws/files/30966569/LTU-EX-05200-SE.pdf 4. You may model a slab in SAFE software and experiment by providing openings of different size, and at different locations (with respect to slab edges), to see effect on variation of stresses around the openings, in order to decide the amount and placement of required reinforcement. Regards.