The section modulus of a built-up member refers to the measure of a cross-sectional area's ability to resist bending. On the other hand, the plastic modulus is the measure of a cross-sectional area's ability to resist plastic deformation. In simpler terms, the section modulus determines a member's strength against bending, while the plastic modulus determines its ability to maintain shape without permanent deformation.
The section modulus of a built-up member is calculated by dividing the moment of inertia of the cross-sectional area by the distance from the neutral axis to the outermost edge of the section. This calculation can vary depending on the shape of the member, as well as the orientation of the load and support.
The section modulus is an important factor in structural design because it helps determine the strength and stiffness of a member against bending and other types of loads. It is used to select the appropriate size and shape of a member to ensure that it can withstand the expected loads and maintain its structural integrity.
The plastic modulus plays a crucial role in the behavior of a built-up member, especially in cases where the load exceeds the member's yield strength. It allows the member to undergo significant plastic deformation without failure, which can be beneficial in certain structural designs. However, excessive plastic deformation can lead to permanent deformation and compromise the structural integrity of the member.
Yes, the section and plastic modulus can be increased in a built-up member by modifying its cross-sectional shape or adding materials to increase its resistance to bending and deformation. This can be achieved through the use of reinforcement, such as adding steel plates or braces, or changing the shape of the member to increase its moment of inertia and distance from the neutral axis.