zenith.international

Please first refer to the ACI documents for Design of Concrete Structures using FRP BARS. Simply using the software does not guarantee the correctness of structural design. I see you are in Nanjing University in China. Are you doing graduate work there or working in a design office ?

The information provided by Mjnasar is correct: ACI 318 says that the torsion reinforcement is additive to the required flexural reinforcement in your case, u can distribute the steel in 2 top corner bars + 1 side bar + 2 bottom corner bars ( Addl to top & bottom Flexural reinforcement )

I will develop the Text for KBCA bylaws to replace the current clause in Chapter 11 of KBCA by laws. In the mean while need volunteers to develop list of Enginners with email addresses so the revised Text can be sent to them and they Endorse it. We start with local Bodies, like KBCA and then towards PEC for revising the Building Code of Pakistan Seismic Provisions 2007. Prof.Dr. Shoaib Ahmad

Let's develop a group of like minded Engineers and make a petition to PEC and KBCA and ACEP. I will lead but but need numbers.

That is the intention

Dear All: [1] Please note that Structural Designers in Pakistan are still using DEFUNCT UBC-97. I am a one person team trying to change this practice. [2] In addition, by using ETABS, they use UBC-97 and latest ACI & ASCE CODES, which is incorrect.

In seismic analysis, the issue of picked up RC columns need careful consideration. Please share your experience for tall (G+40) RC structure..

All references are to ACI 318-05. Minimum flexural reinforcement is not controlled by the provisions of ACI 10.5.1 and 10.5.2 as they do not apply to structural slabs and footings of uniform thickness, rather the minimum flexural reinforcement is determined by 10.5.4 as 0.0018bh. For a structural slab having top and bottom reinforcement both of which exihibit flexural tension, this minimum flexural reinforcement of 0.0018bh for each layer would control over the temperature and strinkage reinforcement of 0.0009bh for each layer (0.0018bh). The questio is whether the provision of 10.5.3 applicable also? The If not, As minimum would always be 0.0018bh for each layer. If so, and in the situation where the required As is small enough, the minimum flexural reinforcement determined by 10.5.3 as 4/3 * As, reg could be less than that determined by 7.12 as 0.0009bh for each layer, thus As minimum being 0.0009bh for each layer. Another way to write it (applies to slabs and footings having top and bottom steel): If As > 0.0018bh, use As If As < 0.0018bh < 4/3As, use 0.0018bh If 0.0009bh < 4/3As < 0.0018bh, use 4/3As If 4/3As < 0.0009bh, use 0.0009bh

For new constrcution, It is recomended that on sites, instead of cubes, cylinders should be cast. The recommended cylinder size is 4x8 inches. The cylinders cast on site should be cured in the same fashion as the strcutural members. These cylinders should be tested in an accredited lab. For exsisting construction, the scheme and location for coring should be decided, coring should be done by trained professionals and the Interpreting Compressive Strength Results should be completed by a professional engineer (PE). The results should not be limted only to the strength test, it should also include the stiffness (modulus of elasticity)

Agree with Rana Waseem.

Please note that this book uses the Canadian Code. One must also look at a companion book that uses the ACI code.

Ghulam Abbas Gazer: It is recognized that you have lot of experience in construction of poultry shed slabs and that commonly structural engineer design 4" thick slabs with steel reinforcement 6 mm dia bars @ 6" c/c that comes to 0.18 to 0.20 % reinforcement. It is not clear why the minimum limits 0.60 % is followed ? Your other part of the question is not clear. Please clarify. Best wishes Zenith International

In our opinion, the observation made below is correct and thus a designer is allowed to increase the minimum steel ratio depending upon the restraint of the structure. "Where structural walls or columns provide significant restraint to shrinkage and temperature movements, the restrain of volume changes causes tension in slabs, as well as displacements, shear forces, and flexural moments in columns or walls. In these cases, it may be necessary to increase the amount of slab reinforcement required by 7.12.2.1 due to the shrinkage and thermal effects in both principal directions (see References 7.7 and 7.16)." Thus for crack control (as serviceability limit) one can use the following "For a maximum design crack width of 0.3 mm (as is commonly specified in codes of practice), it appears that for the restrained slabs tested in this study a reinforcement area of greater than about 270 mm2 (ρ = 0.0045) would be satisfactory" Best wishes Zenith International

The answer by Waseem is correct and clear. Best wishes Zenith International

The response of Umar Makhzuni is comprehensive, clear and correct. In addition, following should be noted. It is advisable that all designs in Pakistan adhere to IBC rather than UBC-97, which is now considered defunct. Use of UBC-97 with latest resistance codes for structural concrete (like ACI 318-05, 318-08, 318-11) and AISC codes with publication dates after 1997 is technically incorrect and must be avoided. I hope that structural design community should adapt to the IBC and the appropriate use of resistance codes.