Design Parameters

The composite steel general section can be defined in Section Property Calculator.
The following steps must be performed:
1. Draw the geometry of the section ( Autocad import is supported).
2. Define two material properties.
3. Generate a composite section with two parts.
4. Add parts (Steel and Concrete) to the composite section.
5. Export the section to the midas Civil as a midas civil section file.
6. Import the section in the Composite Tab of midas Civil under the composite general type.

midas Civil supports the following type of Design Checks for Composite Steel Plate Girder Design:

Ultimate Limit States:

1. Bending Resistance
2. Resistance to Vertical Shear
3. Resistance to Longitudinal Shear
4. Resistance to Lateral Torsional Buckling
5. Resistance to Transverse Force
6. Resistance to Fatigue

midas Civil supports the following type of Design Checks for Composite General Section Design:

Ultimate Limit States:

1. Bending Resistance
2. Resistance to Vertical Shear
3. Resistance to Longitudinal Shear
4. Serviceability Limit States:
5. Stress Limitation
6. Longitudinal Shear

midas Civil supports the following type of Design Checks for Composite Steel I Girder, Tub Girder and Box Girder Design:

Strength Limit State:

1. Flexure Resistance
2. Shear Resistance

Serviceability Limit State.

Constructibility:

1. Flexure Resistance
2. Shear Resistance

Fatigue Limit State.

Shear Connector, Longitudinal Stiffeners and Bearing Stiffeners.

Strength Resistance Factor

Girder Type for Box/Tub Section

Single Box Sections : If the Single Box Sections option is selected, St.Venant torsion and distortion stresses need to be taken into account. The value of distortion stress is determined based on the input value of "Warping Stress Range" option in Fatigue Parameter.

Multiple Box Sections

Consider St. Venant Torsion and Distortion Stresses : Check on to consider St. Venant torsion in accordance with distortion stress. In case of multiple box sections, St. Venant torsion and distortion stresses may be neglected if the relevant conditions (Article 6.11.2.3) are satisfied. The value of distortion stress is determined based on the input value of "Warping Stress Range" option in Fatigue Parameter.

Option for Strength Limit State

Appendix A6 for Negative Flexure Resistance in Web Compact/Noncompact Sections : Check on to apply Appendix A6 for the flexure strength of straight composite I-sections in negative flexure with compact/ noncompact webs. Use of Appendix A6 is optional in accordance with the code.

Mn≤1.3RhMy in Positive Flexure and Compact Sections(6.10.7.1.2-3) : If the three conditions below are not satisfied for the compact sections under positive flexure in a continuous span, the Mn value is restricted to 1.3RhMy.

- The span under consideration and all adjacent interior pier sections satisfy the requirements of Article B6.2,
- The appropriate value of θRL from Article B6.6.2 exceeds 0.009 radians at all adjacent interior-pier sections
- In which case the nominal flexural resistance of the section is not subject to the limitation of Eq. 6.10.7.1.2-3.

Post-buckling Tension-field Action for Shear Resistance (6.10.9.3.2) : Check on to consider post buckling resistance due to tension field action in the nominal shear resistance of an interior stiffened web panel.

Long-term Section Property of Cracked Composite Section: Rebar Area/3 : Check on to devide rebar area by 3 to determine long-term section properties of cracked composite section. Otherwise, the whole rebar area will be added to the steel beam area.

Include Normal Stress due to Torsional Warping

Normal stress due to restrained warping can be introduced in the design of steel composite section to AASHTO LRFD 17. Both Consider Warping Effect (7th dof) option from the Section dialog box and Warping normal stress option from the Design Parameter dialog box should be checked on. Warping normal stress is calculated using bi-moment (B), warping constant (Cw) and warping function (Ψ).

Warping constant (Iw) and warping function (w) can be viewed from the image below.

midas Civil supports the following type of Design Checks for Composite Steel I Girder, Tub Girder and Box Girder Design:

Ultimate Limit State:

1. Flexure

2. Shear

3. Flexure & Shear & Torsion for Box Girders with Longitudinal Stiffeners

4. Constructibility (I-section only)

Serviceability Limit State.

1. Crack Control of Slab

2. Longitudinal Shear

Capacity Reduction Factor

In AS 5100.6 (Australian Bridge Design Standard – Steel and Composite Construction), the capacity reduction factor is applied to account for uncertainties in material properties, fabrication quality, and structural behavior. This factor ensures a conservative and safe design by reducing the nominal capacity of structural components.

ULS

Member subject to bending for flexure : 0.9

Member subject to bending for web in shear : 0.9

Member subject to bending for stiffener : 0.9

SLS

Member subject to bending for shear connectors: 1.0

midas Civil supports the following type of Design Checks for Composite Steel I Girder, Tub Girder and Box Girder Design:

Strength Limit State:

1. Flexure Resistance
2. Shear Resistance

Serviceability Limit State.
Constructibility:

1. Flexure Resistance
2. Shear Resistance

Fatigue Limit State.
Shear Connector and Stiffeners.

Strength Resistance Factor

Girder Type for Box/Tub Section

Single Box Sections : If Single Box Section is selected, the following clauses of CSA S6-19 are applied for the box/ tub girder design.

10.12.8.4 Moment resistances

10.12.8.5 Combined shear and torsion

Multiple Box Sections: If Multiple Box Section is selected, the above clauses are not applied for the box/ tub girder design.

Option for Construction Stage

Check Construction Stage Resistance : Check on this option to check moment and shear resistance for the steel section only during construction.