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Dear All, Just a brief introduction about the Diaphragm Design for Lateral Forces in case of Major Earthquake Areas: Please correct me where I am wrong: There are two types of forces in a member 1- Out of Plane Forces (out of plane behavior) 2- Inplane Forces (inplane behavior) Followings are the major components for design purpose in any structure a- Foundation b- Shear wall c- Column d- Beam e- Slab Foundation : We design it mostly for out of plane forces Shear wall : We design it for purely inplane forces because we neglect its out of plane stiffness Slab : We design it for out of plane as well as for inplane bending. Slab: Out of Plane In slabs, we normally provide the flexural reinforcement and check the thickness of slab which is out of plane behavior. This design should be conducted on gravity load basis even the building is located in severe earthquake areas. In case of Slab supported on beams we need to design for out of plane forces based on gravity loading. In case of Flat Slab we also need to design it on gravity loading but we just need to satisfy one requirement of ACI code 21.13.6 (b ). Actually code asks this condition to be satisfied due to the rotation limit of slab due to punching at these joints. One option is to satisfy this requirement (ACI 21.13.6 (b ) or second option is we can check the actual D/C ratio of these junctions by using PEER/ATC 72 guidelines. PEER/ATC 72 guideline is attached here. Both are equally reliable just the later is a guideline not a codal provision. Inplane The second design for a slab which is MUST in severe earthquake areas and normally nobody perform is inplane design. As we know, earthquake acts on a structure laterally, and diaphragm is used to transfer lateral forces to vertical members. We need to assign the proper diaphragm to the slab. Proper means the diaphragm which can distribute the forces to vertical members as well as it transfer the forces through slab. So we have two options. a- Rigid Diaphragm and b- Semi Rigid Diaphragm. So we ll assign semi rigid diaphragm. There is one question why, we ll put this question to some other topic. So when we assign semi rigid diaphragm it will transfer the forces through slab member and in ETABS we can see the forces in the slab. Followings are the reinforcements which we need to design for inplane forces 1- Shear Reinforcement at basement Slab Level and Ground Floor Slab Level. 2- Shear Reinforcement at Podium Levels 3- Tension Reinforcement 4- Chord Reinforcement 5- Shear Friction Reinforcement All of these reinforcements are used to guide the inplane forces from retaining wall to shear wall at basement levels and from shearwall to slab at upper levels. for example tension or collector reinforcement collects axial inplane force and transfer to shearwall. Slab shear reinforcement is used to avoid lateral cracking of slab in case of earthquake. So we must design the slab for these two forces and both have different design practices. The attached NEHRP file is very use full guideline to understand diaphragm design. In ETABS, we can check the inplane forces from F11, F12 and F22 and then making the section cuts from slab. From these section cuts we can obtain shear forces and axial force and flexural force. In addition to slabs, we need to check the retaining wall shear reinforcement (distribution reinforcement) and flexural reinforcement (vertical reinforcement) for these inplane forces. We also need to provide the reinforcement at the junction of basement slab and retaining wall in the form of U bars. This is also based on inplane forces Thanks Muneeb PEER-ATC-72.pdf NEHRP Guideline for Diaphragm Design.pdf

Dear colleagues, Polling for Elections of PEC (Pakistan Engineering Council) Governing Body for the Term 2015-18 are being held on 14th of June 2015 (day after tomorrow). Since the PEC is the controlling authority for all professional matters of engineers in Pakistan, it is certainly necessary that the people voted for running this organisation for the next few years, should have highest engineering degrees and vast professional experience. However, in addition, it is more important that they must be honest, have real urge and proven reputation of promoting engineering as a profession and being real practitioners of merit (in true sense) at each level within their areas of responsibilities. If we could select the candidates, having above mentioned qualities, it would certainly lead towards a better future for not only professional engineers but also for the Pakistan itself. Let us make contribution towards betterment of our beloved country, by selecting those people only, who really want to and can strive to develop Pakistan for making it a better country. Regards.

yeah im talking about this solid block thing! Anyway yes please share. I myself also starting on DIANA and little bit exp on Strand7

One more thing, this is a plain strain problem, where we consider out-of-plane strain to be 0. But there still exists out-of-plane stress that is equal to Poisson's ratio ( normal stress in 1 direction + normal stress in 2 direction). But as you are modelling brick elements, thats not any more a case. Now you are not assuming that certain strain is zero or not! You are now dealing with all stress and strain components turned on!

Fatima, I am not much exp in brick elements. What brick element you are using? Hex8? If yes then try using higher order elements like Hex16 for example. Because if this is happening due to shear locking then any element that has mid nodes can correct this problem. I think you cannot use plate elements here, but if you were to use plate elements, then there would not be any out-of-plane shear forces Sxy & Syz.

Dear Rana, Please check the reference from ETABS Concrete design manual. This is what I am saying. Thanks Muneeb