What type of members are collar ties?

Collar ties are members used in roof construction that are specifically designed to resist tension forces. They are typically installed horizontally in the upper part of a roof structure, connecting opposing rafters. By doing this, collar ties help to prevent the rafters from spreading apart due to gravity and lateral loads, which can lead to structural failure.

When tension is applied to the collar ties, they effectively pull the rafters together, maintaining the integrity and shape of the roof. This action is crucial, particularly in steeply pitched roofs where the risk of rafter spread is significant. The primary function of collar ties is to counteract these forces, making them essential components in ensuring the durability of roofing systems.

In contrast, compression members, shear members, and combination members serve different structural roles. Compression members bear loads that push down on them, while shear members are essential for resisting forces that slide past one another. Combination members incorporate aspects of both tension and compression but do not serve the same function as collar ties. Therefore, classifying collar ties as tension members accurately reflects their role in structural engineering.