Composite beam deflection calculation

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muratk

New Member
Re: Load transfer to composite flooring Hello, is it possible to operate the main beams as composite together with the secondary beams? When we look at the image, no shear reinforcement is placed on the main beams and only the secondary beams appear as composite in the calculations. According to the manual calculation, the deflection of these beams is also higher. Thanks
 
Re: Load transfer to composite flooring Hello; In the current version, the main beams are not designed as composite beams. R&D studies are carried out for the composite design of the main steel beams. Is the deflection of your main beams too high by hand? If you can send your model and manual account with a short description, we can review it and get back to you. Good work.
 
Re: Load transfer to composite floor The files are attached. The deflection of the secondary beams is 11.4 mm under service loads, and 46 mm with the program, so it does not save the section due to deflection.
 
Re: Load transfer to my composite flooring Mr. Murat, I checked your account. The deflection value of 46 mm calculated by ideCAD is correct. Please check your account manually by considering the following points. 1. Check the material inputs. The steel elasticity module you use in the calculation and the value used by the program are different. Structure Tree - Material - S235 You should edit it in the tab that opens with a double click. 2. You have accepted the composite rate of 50%, but in the model you entered, this rate (PCC) turns out to be 60.5% according to the shear force that the slip ribs can transmit. Accordingly, the pressure depth of the concrete block will change. 3. In the deflection calculation, you also consider the effect of the concrete inside the trapezoidal sheet. In the program, only the concrete area above the trapezoidal sheet is taken into account. 4. The load you use for deflection only belongs to the live load (Q). However, the total deflection (G+Q) is given in the program. Please see Section 15.1 of the Steel Structures Regulation. 5. When calculating the moment of inertia of the composite beam, you skipped the reduction with a coefficient of 0.75. Steel Structures regulation Equation (12.17b). 6. The lower limit moment of inertia (ILB) value is calculated in the program. In this calculation, the concrete area under pressure (not the entire concrete area) is converted to the equivalent steel area, the neutral axis is found, and the moment of inertia is calculated accordingly. This method is taken from the book Steel Design by William T. Segui. 7. Finally, the deflection is calculated as follows when manufacturing without struts. a) Fixed Loads (wD)
  • i) Steel self weight ii) Trapezoidal sheet weight iii) Concrete weight
b) Loads for Composite Beam
  • iv) Pavement fixed load(wC) v) Pavement live load (wL) vi) Snow load(wS)
Deflection calculation a) Deflection calculation for fixed loads (the moment of inertia(I) of the steel beam section is used): delta_D = (5*wD*L^4)/(384* E*I) b) Calculation for pavement constant load (lower limit moment of inertia (ILB) is used): delta_C = (5*wC*L^4)/(384*E*ILB) c) Calculation for live load (lower limit) moment of inertia (ILB) is used): delta_L = (5*wL*L^4)/(384*E*ILB) Total deflection = delta_D + delta_C + delta_L
 
Re: Load transfer to the composite floor Emre Bey, when I select the same value as the concrete elasticity module, increase the composite ratio to 60%, multiply the moment of inertia of the composite section by 0.75 and repeat the calculation, the deflection of the fixed + live load reaches 30 mm. The difference may be due to the fact that the concrete between the trapezoidal section is not taken into account as you said. Compared to L/300, it saves a section in manual calculation, but in my opinion, this section should be enlarged according to the result of the program in order to stay on the safe side. Thanks
 
Re: Load transfer to composite floor Hello Mr. Murat, Since the pitch direction of the trapezoidal sheet is placed perpendicular to the longitudinal axis of the steel beam in accordance with the Steel Structures Regulation 12.4.2.3(e), the contribution of the concrete below the upper level of the sheet metal should be neglected. In addition, as I wrote before, when calculating the lower limit moment of inertia (ILB), this value will be lower than the converted moment of inertia (Itr), since only the pressure-operated part of the concrete is used. This is a safe approach and results in a higher deflection value. Therefore, the deflection value of 30 mm that you calculated by hand is also not correct. good work
 
Re: Load transfer to composite flooring Hello Mr. Murat; By arranging the values such as the elasticity module in the program with the manual calculation values you sent, and using your exact methods, we obtain the following results when we perform the operations without using it to determine the neutral axis (as the program does), since the concrete inside the trapezoidal sheet is discontinuous. We think it will be more descriptive about how the program works. The results of the manual calculations I made here are very close to the value found by ideCAD. The difference is due to manual rounding. For the composite beam algorithm used by the program, click:
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With the composite beam account recorded video of the related webinar:
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Thank you for your question. Good work.
 
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