Using the moments of inertia, the response of the beam to various forces can be evaluated. If the same T beam as above were inverted, its moment of inertia would be calculated as follows: Application Of The Moment Of Inertia Of A T BeamĪ T beam is a common structural element used in engineering designs. In the event that a T beam is used in an inverted orientation, the moment of inertia about the x-axis will be different than that about a traditional T beam orientation. In fact, since the pieces are identical, it is only necessary to calculate the moment of inertia for one section, and then use the same numerical value and the distance from the centroid on both sides. In the case of a double T beam, n will be two, but the same concept can be applied for calculating the total moment of inertia for objects that are divided into more than two pieces, so long as the individual moment of inertia of each piece is calculated about the same centroid. The above equation may look familiar, as it is a slight variation on the parallel axis theorem. To calculate the moment of inertia of such a beam, it is necessary to split it into two identical pieces and sum the individual moments of inertia about the centroid of the complete structure, using the following equation: Double T Beam Moment Of InertiaĪ double T beam is made up of three plates, as shown in the following figure: Using the same T beam, the moment of inertia about the y-axis is as follows: Extension Of T Beam Moment Of Inertiaīeginning with the moment of inertia of a T beam, there are further extensions, which are introduced below. Therefore, the moment of inertia of section A is calculated as follows:Īnd the moment of inertia of section B is calculated as follows:įinally, adding the two together, the total moment of inertia of the T beam is calculated as follows: Example Calculation To calculate the moment of inertia of a T beam about its y-axis, the beam must again be divided into two sections, as follows: Calculate the moment of inertia about the x-axis:.Calculate the distance between the x-axis and the y-axis centroid for each section:.Calculate the location of the y-axis centroid:.Calculate the area of each section of the T beam:.Calculate the moment of inertia of the two sections about their individual x-axis:.To calculate the moment of inertia about the x-axis, the following steps are taken: To demonstrate the calculation of the moment of inertia about the x-axis for a T beam, assume a T beam with the following dimensions: Using the above equation, the centroid of the entire beam is calculated using the individual centroids of the components that the beam was split into. To calculate the value of ȳ c, the following equation is used: ȳ c is the centroid of the entire beam, with SI units of mm.
It describes how far from centroid the area is distributed. The dimensions of radius of gyration are. Where I the moment of inertia of the cross-section around the same axis and A its area. Radius of gyration R g of a cross-section, relative to an axis, is given by the formula: The area A and the perimeter P of a tee cross-section, can be found with the next formulas: