Beam Torsion Design Example Using ASDIP CONCRETE

January 25, 2023

ASDIP CONCRETE is a structural engineering software for design of concrete members, such as continuous beams for bending, shear, and torsion, based on the latest ACI 318 and CSA A23.3 provisions.

But how do you enter the information in the program? How do you check the results? How do you optimize the design? The following is a step-by-step beam torsion design example using ASDIP CONCRETE.

Beam torsion design example

As an example, design the flexural, shear, and torsion reinforcement for an edge continuous beam of 30'-0" span. The joist system framing into the edge beam produces a uniform torsional load along the length of the beam, as shown below. The beam is part of the second floor of a multistory building.

Enter the geometry and material properties

In the Geometry tab select the Spandrel beam type and enter the dimensions given in the statement of the problem. Since this is a continuous beam with many spans, model three spans 30'-0" each and specify fixed supports at the ends. This will represent the current condition closely.

In the Materials tab enter the material properties, such as f'c and fy. In this example we will specify the parabolic Hognestad's curve for concrete, and the Elasto-plastic bi-linear distribution for steel.

ASDIP CONCRETE generates a condensed presentation of the results, with a more detailed information organized by topic and load combination, for a quick granular check of the beam design as you go. The screen shot below shows the Materials tab and the Condensed tab. Note the section for torsion design.

Use the Loads tab to enter the applied loads on the beam. In this case the loads are given as D = 121 psf and L = 100 psf, so let's select the Load cases option at the top of the page and enter the uniform load values. The tributary width of the spandrel beam is the joist span / 2 = 20'-0".

To consider the torsion, enter the eccentricity perpendicular to the axis of the beam, which was calculated in the statement of the problem as e = 4.5' = 54", and then check the corresponding Torsion box as shown below. In addition, since this is an indeterminate structure, torsional moments can be redistributed. Check the box "Torsion may be reduced" and the program will use the minimum of Tu and φTcr for torsion design. Finally, copy these loads to all segments by clicking the corresponding button.

ASDIP CONCRETE generates a detailed presentation of the results, showing step-by-step calculations organized by topic and load combination, with exposed formulas and references to the ACI code. This is excellent for a deep granular check of the design. The screen shot below shows the Loads tab and the Detailed tab. Note the design calculations of the beam for torsion.

Designing Beams for Torsion

The design of beams for torsion includes the checking of the interaction with bending and shear. ASDIP CONCRETE generates all the required calculations per the ACI and CSA provisions.

The Design Manager is a tool that will design the reinforcement based on the specified loads and design criteria. In the Reinforcement tab select the Design Manager at the top of the page, and then specify the preferred bar sizes. In this example let's specify rebars #9 and stirrups #4. This can be changed later if necessary. Click on the Design button and the software will generate the required reinforcing steel. Then you can modify whatever you see fit to fine tune your design.

The image below shows the Reinforcement tab and the generated shear and moment diagrams for the continuous beam. Note that the software shows the structural capacity in blue for visual comparison purposes. In the Construction tab ASDIP CONCRETE generates a beam elevation with the set of rebars and stirrups, as shown below.

Takeaway

ASDIP CONCRETE includes the design of beams for bending, shear, and torsion. This step-by-step design example shows how fast the design can be completed and optimized using the simple and intuitive user interface. The results are shown instantly in both text and graphics format for an immediate granular check.

For our collection of blog posts about concrete design please visit Structural Concrete Design.

Best regards,

Javier Encinas, PE

ASDIP Structural Software