Determining the behavior of the structure Rigid or Semi-Rigid

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engineer_yildiz

New Member
Dear form users and the idecad family, who always try to help us, we say that the engineer should decide how the structure will behave (rigid or semi-rigid). So what should the engineer reference about making this decision? Are there experimental findings? Have practical experiences? Are there theoretical studies and articles? So, are the results of these studies (experimental/practical/theoretical) accredited? Do the Standards and regulations made to make a structure whose behavior is not fully known and know what to do, leave us alone in this regard? What should we do? Is there anything the program can guide us about? Thank you and have nice work.
 
Re: Determining the behavior of the structure Rigid? Is it Semi-Rigid? Hello,
We say that the engineer should decide how the structure will behave (rigid or semi-rigid)
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We do not say that the engineer should decide how the structure will behave (rigid or semi-rigid).[/b ]Rigid diaphragm and semi-rigid diaphragm solution calculation methods. Both accounts contain different admissions. In these assumptions, the axial force cannot be calculated in the beams in the rigid diaphragm acceptance. Deformations in the floor plane are neglected. In the semi-rigid diaphragm assumption, the finite element model, which is created by dividing the floors into shell elements, is to be included in the global stiffness matrix of the structure together with beams, columns, ribs, shears, foundation beams and raft foundations, and static and dynamic analysis is performed. In the model, floor masses are considered as distributed masses along the floor. As a result, semi-rigid diaphragm (elastic diaphragm) gives much more accurate and sensitive results than analyzes made with a rigid diaphragm in all conditions.
So what should the engineer refer to when making this decision?
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You can take the New Earthquake Code published as a draft as a reference.
 
Re: Determining the behavior of the structure Rigid? Is it Semi-Rigid?
Are the results of these studies (experimental/practical/theoretical) accredited? Do the Standards and regulations made to make a structure whose behavior is not fully known, know what to do and leave us alone in this regard?
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In the New Earthquake Regulation published as a draft, which calculations will be made according to the building types are explained with the articles. In the New Earthquake Regulation published as a draft; According to article 3.7.2.2 In buildings with A2 and A3 type irregularities, two-dimensional sheet (membrane) shall be modeled with finite elements to show that floor slabs can safely transfer earthquake forces between vertical carrier system elements in their own planes. According to 4.5.6.2 According to 3.7.2.2, reinforced concrete floors in buildings where A2 and A3 type irregularities exist and/or floors are not intended to function as rigid diaphragms, two-dimensional slab (membrane) to include degrees of freedom regarding in-plane displacements will be modeled with finite elements. In this case, three degrees of freedom will be considered at each node. If desired, shell finite elements with six degrees of freedom at each node can also be used, including degrees of freedom for out-of-plane displacements. According to article 4.5.7.1 As stated in 3A.6.4, the transition that takes place in the transition from normal floors to very rigid basement floors and has to transfer all or most of the inertial forces occurring in the upper floors to the perimeter walls of the basement floors suddenly It is essential to provide sufficient in-plane rigidity and strength in floors of floors. This condition is also valid for other transition floors where sudden stiffness changes are made for other reasons. According to 4.5.7.2 According to 7.2.2., regardless of the presence of A2 and A3 type irregularities, the floors of the transitional floors will be modeled according to 4.5.6.2 by taking sufficient floor thicknesses. (that is, the shell will be modeled with elements) According to article 7.11.3 In-plane axial and shear stresses in the floors of buildings with and without beams shall be calculated with the assumption of an elastic diaphragm.(Elastic diaphragm means semi-rigid diaphragm.) [b ]According to article 7.11.4[/b] In buildings with beamed slabs where there are A2 and A3 irregularities where it is necessary to show that the earthquake loads are transferred from the floors to the vertical load-bearing elements safely, the conditions given in article 7.11.3 will be met for the floors. (Refers to the semi-rigid diaphragm solution.) [ quote]Do the Standards and regulations made to make a structure whose behavior is not fully known and know what to do at the maximum leave us alone in this regard?[/quote] The articles I have explained above in the New Earthquake Regulation published as a draft guide you clearly.
What should we do? Is there anything that the program can direct us to in this regard?
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You can examine the New Earthquake Code published as a draft, articles, foreign regulations and theses written on this subject.
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Re: Determining the behavior of the structure Rigid? Is it Semi-Rigid? Dear M. Berat Denli, thank you for your comment. Your comment: "We are not saying that how the structure will behave (rigid or semi-rigid) the engineer should decide. Solution with rigid diaphragm and semi-rigid diaphragm ]calculation methods.Both calculations contain different assumptions.Axial force cannot be calculated in beams in Rigid diaphragm assumption under these assumptions.Deformations in floor plane are neglected. In the semi-rigid diaphragm assumption, the finite element model created by dividing the floors into shell elements, beams, columns, ribs, shears, foundation beams and raft foundations together with the structure is included in the global stiffness matrix, and the static and dynamic analysis is done in the model. are considered as masses. shaped. Don't you think there is a situation about which situations we should prefer "Rigid diaphragm and semi-rigid diaphragm solution calculation methods"? If we had to answer the subject with an example: Do you think it would be right to solve a structure with 3m column axis spacing and 50 cm slab thickness to be solved as semi-rigid? Or which one (rigid or semi-rigid solution) is correct? Not using the initiative? Thank you and have nice work.
 
Re: Determining the behavior of the structure Rigid? Is it Semi-Rigid? Your Question: Is there a situation regarding the conditions under which we should prefer "Rigid diaphragm and semi-rigid diaphragm solution calculation methods"? Answer : There are situations where we have to choose. Review the questions and answers below. Your question: Do you think it would be right to solve a semi-rigid structure with a column spacing of 3m and a slab thickness of 50 cm? Answer: Yes, that is correct. If you were to ask the question: Would a structure with column spacing of 3m and slab thickness of 50 cm be solved with the assumption rigid diaphragm? Answer: Yes, that is correct. Or if you were to ask the following question: Would it be correct to solve a structure with a column axis distance of 3m and a slab floor thickness of 5 cm as a semi-rigid diaphragm? Answer: Yes, that is correct. Or if you were to ask: Do you think it would be right to solve a structure with 3m column spacing and 5 cm slab thickness with the assumption of rigid diaphragm? Answer: No, it is not true. If we summarize in general; Regardless of the slab thickness, 5 cm 12 cm 50 cm, whether the slab contains gaps or not, these structures should always be solved with the assumption of "elastic diaphragm". In order to be able to calculate with a rigid diaphragm assumption, the upholstery must behave completely rigid. Having sufficient thickness, no gaps, etc.
 
Re: Determining the behavior of the structure Rigid? Is it Semi-Rigid? We love ideCAD and the forum for that. You're welcome. Unver ÖZCAN
 
Re: Determining the behavior of the structure Rigid? Is it Semi-Rigid? Thank you for your help. Due to my job, I am responsible for controlling Static projects. The questions I asked are the issues that we could not reach an agreement with Idecad users where I am. Now, I will ask Idecad users to choose the "Semi-Rigid" option, regardless of their flooring systems (types)?
 
Re: Determining the behavior of the structure Rigid? Semi-Rigid? But you will want it from all other program users as well. You will say go solve this system with semi-rigid, that is, elastic diaphragm acceptance. ideCAD users will solve it and bring it. Other program users will not be able to bring it if the program they use does not have this feature. And they will tell you, there is no new regulation yet. In this case, how we will act at this stage determines the regulatory sanctions. Regulations are binding for administrations. The current earthquake code does not require the elastic diaphragm solution. But if the Engineer solves it with an elastic diaphragm and brings it, you shouldn't say that it won't happen and come and solve the rigid diaphragm. Because the elastic diaphragm gives more accurate, more advanced and more sensitive results in all conditions. However, if the structure contains A2, A3 irregularities, the rigid diaphragm solution will not give accurate results. Moreover, in these systems, especially in beamless floors and rib cassette systems, calculating with the assumption of a rigid diaphragm will detract from the truth. Semi-rigid solution takes more computer time and requires more memory than rigid solution. In other words, while a normal 15-storey 200 m2 building is calculated in 2 minutes with the rigid diaphragm method, the semi-rigid solution will take 25, 30 minutes, maybe longer. In particular, flooring systems with low thickness, hollow block systems, elastic diaphragm solution will give results that are not close at all compared to the rigid diaphragm solution. If you ask which of these solutions is correct; The semi-rigid diaphragm solution is much more accurate. The differences between the semi-rigid and rigid solution of the ideCAD program are valid for each program. It is natural that there is a difference, because they are two different calculation methods. However, in some systems the differences may be less, in some systems more. Due to your position, you should approach each engineer at an equal distance and under the same conditions. But once the regulation comes into force, you will want every structure to be solved semi-rigidly. There is no point in prolonging this matter any further. You asked your questions, and I wrote an answer in terms of both ideCAD and regulations and scientific issues. Thank you for your interest and support.
 
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