Loss due to relaxation of strands is categorized as a long-term pre-stress loss in a pre-stressed concrete member.

Explanation:

Pre-stressed concrete is a construction material that is widely used in the construction industry due to its ability to withstand high compressive forces. It is created by introducing pre-compressive stresses into the concrete before it is subjected to external loads. This pre-compressive stress helps to counteract the tensile forces that the concrete would otherwise experience under load.

However, over time, the pre-stress in a pre-stressed concrete member may decrease due to various factors. These factors can be categorized into two types: short-term losses and long-term losses. Short-term losses occur immediately after the pre-stressing force is applied, while long-term losses occur over an extended period.

Long-term pre-stress losses can be further divided into several categories, including:

1. Loss due to relaxation of strands: This is the category that is relevant to the given question. In pre-stressed concrete, steel strands or wires are commonly used to apply the pre-compressive force. These strands are initially tensioned and anchored to the concrete member. However, over time, the steel strands may experience relaxation, causing a decrease in the pre-stress. This relaxation is primarily caused by the creep and shrinkage of the concrete, as well as the relaxation of the steel itself. The loss due to relaxation of strands is a significant long-term pre-stress loss and needs to be considered in the design and analysis of pre-stressed concrete members.

2. Loss due to creep of concrete: Creep refers to the time-dependent deformation of concrete under sustained load. When pre-stressed concrete is subjected to sustained loads, the concrete will gradually undergo creep, resulting in a decrease in the pre-stress over time.

3. Loss due to shrinkage of concrete: Shrinkage refers to the reduction in volume of concrete due to the evaporation of water. As the concrete shrinks, the pre-stress in the steel strands will decrease.

4. Loss due to relaxation of steel: Steel used in pre-stressed concrete may also experience relaxation, which can lead to a decrease in the pre-stress.

In summary, loss due to relaxation of strands is categorized as a long-term pre-stress loss in a pre-stressed concrete member. This loss occurs over time as the steel strands used to apply the pre-compressive force in the concrete relax due to factors such as creep, shrinkage, and relaxation of the steel itself. It is important to consider these long-term losses in the design and analysis of pre-stressed concrete members to ensure their structural integrity and performance over time.