7048x

2017-11-14

Downstand Beams, Ribs, T-Beams: Shear Between Web and Flanges

In order to ensure the effects of panels, which should act as tensile or compression chords, it is necessary to connect them to the web in a shear-resistant manner. This connection is obtained in a similar way as the shear transfer in the joint between concreting sections by using the interaction between compressive struts and ties. In order to ensure the shear resistance, it must be verified that the compressive strut resistance is given and the tie force can be absorbed by the transverse reinforcement.

Design According to EC2-1-1

It is necessary to verify that the effective shear force v_Ed does not exceed the absorbable shear forces v_Rd,max and v_Rd,s:

v_{Ed} \leq v_{Rd, \max} and v_{Ed} \leq v_{Rd, s}

Formula 1

The longitudinal shear force vEd is determined by the relation

v_{Ed} = \frac{{ΔF}_{d}}{h_{f} \cdot Δx}

Formula 2

. ΔF_d corresponds to the longitudinal force difference, which occurs in a one-sided chord section on the length Δx. To determine this longitudinal force difference, the compression chord force F_cd,a and the tensile chord force F_sd,a are required. The maximum value that may be assumed for Δx is half the distance between the section where the moment is 0 and the section where the moment is maximum. In the case of applying point loads, the length Δx should not exceed the distance between point loads.

Formula Symbols for Connection Between Chords and Web (Source: [1])

The reinforcement for absorbing the tensile forces in the plate that is transverse to the web is determined as follows:

(\frac{A_{sf} \cdot f_{yd}}{s_{f}}) \geq \frac{v_{Ed} \cdot h_{f}}{\cot θ_{f}}

Formula 3

Furthermore, it must be verified that the load-bearing capacity of the compressive strut (A in Image 01) is not exceeded in the flange. For this, Equation

v_{Ed} \leq ν \cdot f_{cd} \cdot \sin θ_{f} \cdot \cos θ_{f}

Formula 4

applies.

If there is transverse bending of the plate and longitudinal shear between the web and flange at the same time, you should use the larger steel cross-section, which results from the two designs for the upper position in the plate. This also means that the upper transverse bending reinforcement can be completely compensated for the upper position of the shear reinforcement.

Considering Shear Between Web and Flange in RF-CONCRETE Members

Shear joints can be considered in RF‑CONCRETE Members, in Window 1.6 Reinforcement under the "Shear Joint" tab.

Activation of Consideration of Shear Forces Between Web and Chords in RF-CONCRETE Members

Results of Shear Joint Design

Windows 2.1 to 2.4 show the resulting required reinforcement. These results can be displayed by cross-section, by set of member, by member, or by x-location.

Result Output for Shear Joint Design

The result of the required reinforcement for the shear joint is displayed together with the result of the shear reinforcement by section length a_sf. In the "Detailed Results" table, you can see some intermediate values of the shear design between flange and web. These intermediate values are listed under the results of "Shear Between Web and Flanges of T-Sections".

Literature

[1]	Fingerloos, F., Hegger, J., & Zilch, K. (2016). Eurocode 2 für Deutschland - Kommentierte Fassung (2nd ed.). Berlin: Beuth.
[2]	Manual RF-/CONCRETE Members. (2017). Tiefenbach: Dlubal Software. Download

Author

Mr. Hörold takes care of the Dlubal Software website, creates press releases and marketing materials, and moderates the German and English webinars.

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Videos

FAQ

FAQ 004431 | Where can I set partial safety factors for design in RF‑CONCRETE Members?

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FAQ

FAQ 005472 | In the table of the objects to be designed in the Concrete Design add-on, punching nodes are...

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FAQ 005432 | How can I set user-defined points for result values on surfaces in RFEM 6?

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When it comes to wind loads on building type structures as per ASCE 7, numerous resources can be found to supplement design standards and aid engineers with this lateral load application. However, engineers may find it more difficult to find similar resources for wind loading on non-building type structures. This article will examine the steps to calculate and apply wind loads as per ASCE 7-22 on a circular reinforced concrete tank with a dome roof.

Screenshots

Formula Symbols for Connection Between Chords and Web (Source: [1])

Activation of Consideration of Shear Forces Between Web and Chords in RF-CONCRETE Members

Result Output for Shear Joint Design

GT 000456 | Analysis and Design Based on Building Information Modeling (BIM) Tools - Study of Bridge with Prestressed Beams

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Errors in Design Resulting from Incorrect Entry

Incorrectly Defined Reinforcement with 0.00 cm²/m in Subareas of Surface

Correctly Defined Reinforcement on Entire Surface

Switching to "Manual Definition of Reinforcement Areas"

Note when Opening Previous Program Version

Product Features

Feature 002801 | Punching Shear Design for All Section Shapes

Do you have individual column sections and angled wall geometries, and need punching shear design for them?

No problem. In RFEM 6, you can perform punching shear design not only for rectangular and circular sections, but for any cross-section shape.

Feature 002722 | Sensitivity Coefficient

For a response spectrum analysis of building models, you can display the sensitivity coefficients for the horizontal directions by story.

These key figures allow you to interpret the sensitivity to stability effects.

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The MRF is displayed by mode shape in the result table under Stability Analysis → Results by Members → Effective Lengths and Critical Loads.

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Frequently Asked Questions (FAQ)

When performing "manual definition of the reinforcement areas" in RF‑CONCRETE Surfaces, do I have to completely reinforce the entire structural component manually? Or does RF‑CONCRETE Surfaces apply the required reinforcement in the areas where I have not performed the manual definition?

When opening an RFEM file, the entries in RF‑CONCRETE Surfaces are lost. Is this possible?

Where can I set partial safety factors for design in RF‑CONCRETE Members?

Which products do you recommend for the structural analysis and design of reinforced concrete structures?

In the table of the objects to be designed in the Concrete Design add-on, punching nodes are listed in the not valid/deactivated column, although I have defined them as punching nodes. How can I fix this?

How can I generate an area load on members via cells in RFEM 6 or RSTAB 9?

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