Members

In the Members tab of the 'Ultimate configuration' dialog, you can make basic settings for the ULS design checks of members and member sets.

Edit Ultimate Configuration – Members

The 'design parameters' are divided into several categories.

Consider internal forces for concrete design

In this category, you can control the member internal forces N, M_y, M_z, V_y, V_z, and M_T for the design and define which internal forces are considered in the design checks. By default, all forces and moments are considered if they exceed a certain 'tolerance'. You can define this value individually for each internal force type.

Considering Internal Forces for Concrete Design

This makes it possible, for example, to neglect the torsional moment from compatibility conditions when designing a rib. To do this, define a new ultimate configuration, deactivate the torsional moments M_T,Ed, and use this configuration for the rib.

Reduction of internal forces in z-direction

In this category, you can make settings for the 'redistribution of moments', 'reduction of moments' or 'moments at support edge', and the 'reduction of shear forces'.

Reduction of Internal Forces in z-Direction

The relevant sections of the standard are given for the individual options. The check boxes control whether the design moment M_y is modified or the shear force V_z is reduced in the design.

The chapter Design supports and deflection describes how to proceed when defining supports for the concrete design and how to make the settings for a monolithic support or the ratio δ for the redistribution of moments at an inner support.

The following image shows the utilizations for the shear force design UL0200.02 with reduction of the shear force V_z (upper curve) and without reduction of the shear force V_z (lower curve).

Distribution of Design Ratio for Shear Design with(out) Vz Reduction

For more information on the shear force reduction in the member design, see the following technical articles in our Knowledge Base:

• Reduction of shear force V_z (for RFEM 5, concept also applies to RFEM 6)
• Definition of design supports

Required longitudinal reinforcement

Reinforcement Layout for Determination of Required Longitudinal Reinforcement

Reinforcement layout

The reinforcement layout allows you to influence the determination of the required longitudinal reinforcement. Various options are available in the list (see image reinforcement layout).

The 'reinforcement layout' affects the distribution of the required longitudinal reinforcement, which is always output after the design – regardless of whether individual design checks are fulfilled or not. If a member is not sufficiently dimensioned after the design with the defined longitudinal reinforcement, you can compare this distribution of the required reinforcement with the distribution of the provided reinforcement and determine the 'uncovered reinforcement' from this. This is available as a result.

Distribute reinforcement uniformly over entire plate width

With this option, you can define whether the entire plate width of the rib member (entire flange width) or only the width of the rectangular cross-section should be used when determining the required longitudinal reinforcement.

Include tensile force due to shear in required longitudinal reinforcement

The check box controls whether the tensile force component from the shear force (curtailment of the longitudinal tension reinforcement) should be included when determining the required longitudinal reinforcement or not.

Design rules

Detailing and Particular Rules

Optionally, the member design also checks design specifications regarding the 'minimum longitudinal reinforcement', 'minimum reinforcement ratio', or 'minimum shear reinforcement'. If one of these design checks is not fulfilled with the specified reinforcement, you can either exclude the design check here or adjust the reinforcement.

Required shear reinforcement - shear resistance

Three options are available for determining the required shear reinforcement.

Required Shear Reinforcement - Shear Capacity

In the default setting, the statically required longitudinal reinforcement is used to determine the shear resistance V_Rd,c. Since with this option the longitudinal reinforcement percentage ρ_l differs from x-location to x-location of the member, the shear resistance along the member is not constant either, but depends on the required longitudinal reinforcement.

Alternatively, you can use the provided longitudinal reinforcement to determine the shear resistance V_Rd,c. If a constant longitudinal reinforcement was defined along the member, the applied longitudinal reinforcement percentage ρ_l is also constant.

With the third option, you can increase the required longitudinal reinforcement to avoid shear reinforcement. Thus, the required longitudinal reinforcement is influenced not only by the bending design but also by the shear force design: The program increases the required longitudinal reinforcement until V_Ed = V_Rd,c.

Shear and torsion

In the Shear and torsion | calculation settings category, you define which cross-section area is used for the shear and torsion design checks and how the torsional resistance before crack formation is determined.

Shear and Torsion – Calculation Settings

Consider flange in parametric T- and I-sections for shear and torsion calculation

This check box controls whether the flange is considered in the shear and torsion calculation for parametric T- and I-sections.

• Activated: The flange is considered in addition to the web.
• Deactivated: Only the web is used.

The option applies to the following parametric sections:

For the shear design checks, the program automatically determines the cross-section properties in the direction of the acting shear force V_Ed. For this purpose, the cross-section is divided into a tension chord and a compression chord (two-chord method).

The position of the two chords results in the following values:

• Effective static depth d_VEd: distance between the tension chord and the most compressed point of the shear cross-section in the V_Ed direction

• Internal lever arm z_VEd: distance between the tension and compression chord in the V_Ed direction

• Web width b_w: smallest cross-section width perpendicular to V_Ed between the tension and compression chord

Two-Chord Method – Cross-Section Properties for Shear in T-Beam with Two Webs

Which cross-section area is used depends on the cross-section type:

• Rectangular and circular cross-sections: entire cross-section
• Parametric T- and I-sections: web or web with flange, depending on the option Consider flange in parametric T- and I-sections for shear and torsion calculation
• Sections from RSECTION: entire cross-section

Geometric determination

In the following cases, the program determines the cross-section properties geometrically:

• The cross-section is completely compressed or completely tensioned, so there is only one resultant.
• The angle between V_Ed and the neutral axis is smaller than 20°.
• The direction of V_Ed is not unique.

In these cases, the program determines the chords solely from the geometry of the reinforcement, without considering the stress and strain state:

1. A line perpendicular to V_Ed through the center of gravity of the shear cross-section divides the cross-section into two parts.
2. In each part, the geometric center of gravity of the reinforcement is determined from the area and coordinates of the bars. These centers of gravity form the two chords.
3. From these chords, d, z, b_w,t, and b_w,t,c are determined.

Geometric Two-Chord Method

Torsional resistance before crack formation

In this list, you select the torsional section modulus used to determine the torsional resistance of the uncracked cross-section T_Rd,c. The setting also applies to the maximum torsional resistance T_Rd,max according to EN 1992-1-1, 6.3.2.

Torsional Resistance Setting

• By torsional section modulus | W_t: The torsional section modulus W_t is taken directly from the cross-section properties.

• By thin-walled cross-section | A_k: The torsional section modulus is determined from the thin-walled equivalent cross-section with the core area A_k. This option is preset.

• Minimum resistance by W_t and A_k: The smaller of the two values is used.

Shear joint

Shear Joint

Shear transfer in joints

By checking the design of the shear joint check box, the design of joints is activated, such as those present in concrete additions for precast elements. This also makes the remaining fields accessible for entering the parameters for the design check according to EN 1992-1-1, 6.2.5.

This design check has so far only been available for the "rib" member type. The required input parameters for classifying the surface roughness and joint width can be entered for this purpose in the member dialog in the "rib" section.

Further information is provided in the chapter shear transfer in joints.

Classification of Surface Roughness and Joint Width for Ribs

Shear transfer between beam web and flange

By checking the check of the flange connection.. check box, the design for the shear transfer between the beam web and the flange according to EN 1992-1-1, 6.2.4 becomes accessible.

The fundamentals of this design check can be understood in the chapter shear transfer between beam web and flange.

Limitation of neutral axis depth

Neutral Axis Depth Limitation

According to EN 1992-1-1, the check of the compression zone limitation must be performed depending on the calculation method (elasticity or plasticity theory). Whether this design check is performed by default depends on the national annex. For example, when designing according to DIN EN 1992-1-1, the design check is activated.

Calculation setting

As a rule, the gross concrete cross-section is used for the cross-section checks. However, if you want to consider a net cross-section (gross cross-section minus reinforcement cross-section) in the cross-section checks due to higher reinforcement ratios, for example, check the 'net concrete area' check box.