Analysis and Design For Torsion of Beams

The study guide shall focus on the analysis and design of torsion of rectangular beams. The topics include undestanding when to consider tension in structural members, calculating torsional stress and torsional reinforcing, and application of relevant codes pertaining to torsion.

threshold torsion

Torsional effects can be neglected when the factored torsional moment Tu is less than the following equations as shown in the left.

cALCULATION OF FACTORED TORSIONAL MOMENT

If the factored torsional moment Tu in a member is required to maintain equilibrium and exceeds the minimum value, the member shall be designed to carry Tu.
In a statically determinate structure where reduction of the torsional moment in a member can occur due to redistribution of internal forces upon cracking, the maximum Tu shall be permitted to be reduced to the following values.

equilibrium vs compatibility torsion

For a statically determinate structure, there is only one path along which a torsional moment can be transmitted to the supports. This type of torsional moment, which is referred to as equilibrium torsion or statically determinate torsion, cannot be reduced by a redistribution of internal forces or by a rotation of the member.
The torsional moment in a particular part of a statically indeterminate structure may be substantially reduced if that part of the structure cracks under the torsion and “gives,” or rotates. The result will be a redistribution of forces in the structure. This type of torsion, is referred to as statically indeterminate torsion or compatibility torsion, in the sense that the part of the structure in question twists in order to keep the deformations of the structure compatible

TORSIONAL MOMENT STRENGTH

DESIGN FOR TORSION

minimum torsion reinforcement

A minimum area of torsional reinforcement shall be provided in all regions where Tu exceeds the threshold torsion.
Where torsional reinforcement is required, the minimum area of transversed closed stirrups shall be computed using the equation shown on the left.

spacing of torsion reinforcement

The spacing of transverse torsion reinforcement shall not exceed the smaller of ph/8 or 300mm.
The longitudinal reinforcement required for torsion shall be distributed around the perimeter of the closed stirrups with a maximum spacing of 300mm. The longitudinal bars or tendons shall be inside the stirrups. There shall be atleast one longitudinal bar or tendon in each corner of the stirrups. Longitudinal bars shall have a diameter of atleast 1/24 times the stirrup spacing, but not less than 10mm.

SUPPLEMENTARY MATERIALS

20221126 - CENG132 Module 5.pdf

ACTIVITIES/COURSEWORK

Coursework #4-5 (CENG132_BARTOLOME).pdf

Module 5-Activity 1 (BARTOLOME) (2).pdf

REFLECTION:

After answering the coursework in torsion, I have grasped and learned some takeaways in this module. First, the effects of torsion are often neglected in analysis of structures. But they are the most common problem considering that structural members are made smaller. Second, disastrous events like earthquakes can cause dangerous torsional forces in all buildings. Thus, there have been more reports of structural failures attributed to torsion. As a result, a rather large amount of analysis should be focused on torsional resistance, and it is necessary for civil engineers to have a much-improved understanding of the behavior of structural members subjected to torsion. On the basis of extensive experimental work, the NSCP code includes very specific requirements for the design of reinforced concrete members subjected to torsion or to torsion combined with shear and bending. It is imperative for me to know that maximum shears and torsional forces may occur in areas where bending moments are small. Pertaining to structural analysis and design, I learned that interaction of shear and torsion are highly important.

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