7920x

001492

Dipl.-Ing. (FH) Andreas Hörold

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, moderates the German and English webinars, and creates newsletters and marketing materials.

Links

Structural Engineering Software for Concrete Structures

Downloads

RFEM Model File

596 KB

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