What is Flexible, Semi-Rigid and Rigid Diaphragm

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engineer_yildiz

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Re: What are Flexible, Semi-Rigid and Rigid Diaphragms? Dear Nurgul Kaya, first of all, I would like to thank you for sharing your references. In the documents you shared, for Semi-Rigid: "Rigidity calculation is calculated depending on slab thickness, dimensions and material parameters". If you have a formulation or reference samples for which we can calculate the stiffness, I would appreciate it if you could share it. I wish you good work
 
Re: What is Flexible, Semi-Rigid and Rigid Diaphragm? Hello; First of all, let me introduce myself, ideYAPI AŞ. I am working as an R&D and Technical Support Engineer in the team. The R&D team is a crowded team under the management of Mr. İsmail and consists of Civil Engineers and Software engineers. Mr. İsmail ( İsmail Hakkı BESLER ideYAPI Founder and Chairman of the Board of Directors) has been working on the 'Finite Element Method' for 35 years since 1982, and thanks to these studies, ideCAD software products have made great progress and reached their current state. R&D studies continue under the supervision of our advisors from ITU. Our software products use the same analysis methods and have similar facilities as worldwide programs such as SAP2000, Etabs. Having a local structural analysis program and continuing to work with a team open to developments; at the same time, it is thanks to the feedback, guidance and useful criticisms and technical documents from the users. As a return to our transparent structure in information sharing, we expect you to share your information as well, only making use of ready-made information will not improve you and us. It is not correct to see the aforementioned 'Finite Element Method' and 'Shell Theory' as methods for determining stiffnesses, forces or displacements with just a few simple four operations, or for easily designing slabs. There are many theses and articles published around the world until they reach their current state, and with the process of adapting them to the regulations, they have been made available to engineers practically. Before the practical application, it is important for the engineers to have a grasp of the general logic, in terms of the accuracy, controllability and reliability of their design. For this reason, there are sample publications from studies for both theory and practical engineering applications below. - When analyzing the structure (static, dynamic, linear and nonlinear), the diaphragm analytical model is created in accordance with the 'Finite Element Method - Shell Theory'. - 'Linear and Nonlinear Analysis' for the 'Shell Theory' described in the visuals For this purpose, how to obtain stiffness matrices and how to use the thickness, size and material parameters of the flooring is available. These images are taken from the pages after page 57 of the ideCAD Finite Elements Manual. You can find the full guide at the link below. ideCAD Finite Element Elements Guide :
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Apart from the above sources, many documents can be found when a simple research is done on the internet. Regarding this subject, first of all, it is necessary to know the theoretical knowledge and general logic about Finite Element Method and Shell Theory. There are many publications in Turkish on this subject. You can find the books of the Chamber of Mechanical Engineers and the Chamber of Civil Engineers, the books of the universities and the lecture notes. I do not share the links to the books because they contain publisher and sales information. You can obtain it by searching the publications of the Chamber of Civil Engineers on the Finite Element Method. 1) Yıldız Technical University -
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2) Chamber of Mechanical Engineers -
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3) Chamber of Civil Engineers - Istanbul Branch -
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Commonly searched for are FEMA, NEHRP Seismic Design, PEER publications. Apart from these, there are additional documents created for engineers by AISC and EUROCODE regulations. These documents describe practical applications for design engineers. Some of the links are below. 1) NEHRP -
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2) NEHRP -
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3) American Wood Council -
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4) UBC -
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5) UBC -
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6) For nonlinear analysis -
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7)
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We hope the information and publications we provide will be useful. Good work.
 
Re: What is Flexible, Semi-Rigid and Rigid Diaphragm? Hello; What I understand from the points you mentioned is that we cannot obtain whether the slab has a semi-rigid behavior or not with a ready-made practical formula. Whether it has this behavior can be determined after applying the finite element method. I know that even if Idecadte prefers either semi-rigid or rigid, floors are still solved according to finite elements. Have I understood correctly what is being said so far? If that's the case, I'll ask a question. I will be glad if you return.
 
Re: What is Flexible, Semi-Rigid and Rigid Diaphragm? Hello; When you select Semi-rigid or rigid diaphragm in the program; Finite Element Method is used. This part is well understood. Looking at the different publications and regulations previously given while making the selection, the situation that has been accepted worldwide is that the semi-rigid diaphragm is the most appropriate approach to real behavior. For this reason, semi-rigid diaphragms are included in common regulations such as AISC 360-10, ASCE/SEI 7-10, Eurocode 8. As we mentioned, semi-rigid diaphragm will be used for most cases in the draft of the Earthquake Code to be published. However, since semi-rigid diaphragm calculation is a more challenging process, regulations allow the choice of rigid diaphragm in some structures for practical design. For example; - If it has reinforced concrete or composite flooring in regular structures in the plan *** The important point is that TDY 2007 is in force until the New Earthquake Regulation is valid, it is not legal to directly impose a sanction on the engineers you supervise, such as dissolve semi-rigid diaphragm or fully rigid diaphragm. ***When the new Earthquake Code comes into effect, semi-rigid diaphragm solutions will be required due to the irregularities outlined earlier. In this case, the design reports you receive should show that semi-rigid diaphragm solution has been made, regardless of which program is used. I hope it was a more concise and clear explanation. If your question is still valid, send it to us and we'll try to answer it.
 
Re: What is Flexible, Semi-Rigid and Rigid Diaphragm? Hello; To summarize the process: We wanted to determine the operation of the diaphragm so that we can make the closest assumption (rigid, semi-rigid, flexible). When we talked about whether there is a practical formulation for the determination of this, it was mentioned that "it was mentioned that the İdecad program can be determined according to the test analysis results used for the A2 and A3 irregularity calculations.", then "its semi-rigid behavior is connected to the finite element method (1)". (1)In the calculation logic of the Finite Elements method in İdecat: How to obtain the rrigidity matrices for the 'Linear and Nonlinear Analysis' for the "Shell Theory" and how the thickness, size and material parameters of the slab are used[/ u] But I couldn't find an answer to which assumption this tiling behavior in the finite element method used in ideacad will lead us to. Even if I choose either rigid or semi-rigid as a solution method in the program, it uses the finite element method. So I choose the behavior first and then apply the finite analysis method according to the selected assumption.It is suggested that we compare the analysis results on the screen, but since the results are calculated according to the assumption that I prefer, it does not solve the question at the very beginning(In order for me to make the correct assumption (rigid, semi-rigid, rigid, flexible) How can I determine the rigidity of the floor and the system?) As a result, there is no situation to guide the user. only from Idecad statements: "There is also this verification in ideCAD. You can do these checks and calculate with rigid diaphragm acceptance. This verification was added to the program in versions 5 and earlier, in versions where ideCAD does not have the ability to calculate with a semi-rigid diaphragm yet." "The control that Mr. Ismail mentioned is the A2 - A3 report. With this report, a warning is given when the Moment/Strength moment in the slab section investigated for the critical section you will determine in the project is less than the tensile strength of the concrete. The amount of As given as a result of the calculation can be placed above and below the slab section. According to the results of the A2 A3 irregularity report, if additional reinforcement is found in critical slabs, it is concluded that the slab rigidity is not sufficient, and it would be appropriate to analyze such structures with the "Semi-rigid diaphragm" option.[/ u] Also, you can always solve with a semi-rigid diaphragm without any need to do this investigation." CONCLUSION: The user will first make a rigid solution, and then additional reinforcements in critical slabs according to the results of the A2 A3 irregularity report [color= If #FF0000] is not output[/color] RIGIT SOLUTION OR if additional reinforcements appear in critical slabs according to the results of the A2 A3 irregularity report, place the reinforcements at these points and RIGID SOLUTION will end the calculation OR if additional reinforcements appear in critical slabs according to the results of A2 A3 irregularity report[/ u] tiling It will be able to solve semi-rigid by saying its rigidity is not enough. IF THERE ARE MISTAKES SO FAR, I WOULD BE GRATEFUL IF YOU CORRECT IT. IT IS NOT MY PURPOSE TO UPGRADE OR DOWNLOAD A PROGRAM. ACCORDING TO THEIR CAPABILITY, YOU CAN USE THE PROGRAM RIGHTLY. Thank you and I wish you a good work.
 
Re: What are Flexible, Semi-Rigid and Rigid Diaphragms? Dear engineer_yildiz,
"engineer_yildiz":6jnxr2qv" said:
But I couldn't find an answer about what assumption this tiling behavior in ideacad used finite element method would lead us to. It uses the finite element method even if I choose either rigid or semi-rigid in the program as the solution method.
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The program does not specifically guide you about which method to choose. It builds a model according to the method you choose. If the analysis method is full rigid diaphragm, it uses the finite element method in the earthquake calculation ( dynamic and time history ) analytical model is established by creating a rigid diaphragm.How the rigid diaphragm model is built in finite element logic is explained in the ideCAD finite element guide. In summary, ideCAD uses the finite element method under all conditions. degrees are connected analytically.[/b] Result -Structure If there is no A2-A3 irregularity and the system is not a beamless slab, a solution can be made with the assumption of a rigid diaphragm. No further checks are required. -If there is A2-A3 irregularity in the structure and 7 versions are used, whether full rigid or semi-rigid solution is made, if the A2-A3 irregularity is checked as in the given document, it will also be checked whether the earthquake forces are transferred safely. If there is A2-A3 irregularity or a beamless slab system a semi-rigid solution would be appropriate. (Semi-rigid solution results in 7 versions can also be examined in terms of stress and reinforcement.) - If there is A2-A3 Irregularity in the structure and it is solved in ideCAD Static 8 version, it is appropriate to make a semi-rigid solution and check the floor, lower and upper reinforcement area needs from the visual design model. The image above is from the ideCAD Finite Element Guide page 93. ideCAD Finite Elements Guide : Good work
 
Hello, In the Analysis options, there is the option "Use Rigid Diaphragm for Vertical Loads" under the "Full Rigid Diaphragm Modeling" option. In what situations should this option be used? I did a research on this subject on the internet, but I couldn't find any theoretical information. I created a sample simple model to benchmark. I solved this model in two different ways. When I review the analysis results, there are minor differences in axial force, shear and moments in beams and columns, and these differences are on a negligible scale. Can you provide information on the use of this option?
 
"Protas":21fzdt5s" said:
Hi, There is "Use Rigid Diaphragm for Vertical Loads" option under "Full Rigid Diaphragm Modeling" option in Analysis options. In which situations should this option be used? I couldn't find any information. I created a simple model for comparison. I solved this model in two different ways. When I analyzed the results of the analysis, there are small differences in axial force, shear and moments in beams and columns, and these differences are negligible. Could you give some information about using this option? ?
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Hello, With this option, it is taken into account that the floors operate as a fully rigid diaphragm under horizontal loads, while floor stiffnesses are not taken into account for vertical loads. Under vertical loads, an outward opening effect occurs on the vertical carriers, especially in the lower floors, due to vertical loads. effect is tried to be held by floor joists and floors. Annual effects, in-plane tensile forces in floor slabs, outward bending moments under vertical load occur in outer columns. If it is assumed that the slabs operate as a fully rigid diaphragm under vertical loads, the nodal points are displaced to the floor plane. The vertical carriers displace exactly, in the same direction and at the same values, and in this way we do not take into account the outward opening effect. Since this effect is low in low-rise buildings, this effect can be neglected, but especially in high-rise buildings, buildings with eccentrically seated columns on the upper floors, structures with a ground floor plan that varies according to the upper floors, and structures with significant gaps in the floor diaphragm on the ground floor, the outward opening effect is greater. . You will get the most realistic results with the semi-rigid diaphragm solution by including the upholstery. You can see this effect in the screenshots I've attached (the deformation scale factor is exaggerated for clarity):
 
Hello, First of all, thank you for your information. As I mentioned in my question, I solved a simple 5-storey building with 2x2 openings for comparison, just to keep it simple. That's why there was not much difference in the analysis results,... Almost every floor of the project I'm working on has a different formwork plan, a total of 10 floors, duplex on the upper floors. there are flats and large floor gaps. The case of A2-A3 irregularity... This option will make a difference. It's good to learn... I wish you good work...
 
If you solve this project with the semi-rigid diaphragm option by including the floors, you will get much more precise and accurate results in both horizontal and vertical calculations.
 
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