【Daily Discussion】Utilities - Civil Engineering - 20210514

This is the phenomenon of \"over-tensioning\" in the application of prestressed engineering; since prestressed steel bars experience prestress relaxation after tensioning, in order to overcome this relaxation caused by tensioning, the tensioning force applied to the prestressed bars must exceed the controlled stress by 5%, and the load must be maintained for a specified period of time.

This is the phenomenon of \"over-tensioning\" in the application of prestressed engineering; since prestressed steel bars experience prestress relaxation after tensioning, in order to overcome this relaxation caused by tensioning, the tensioning force applied to the prestressed bars must exceed the controlled stress by 5%, and the load must be maintained for a specified period of time. Generally, a strain of 2% or 3% is used, and the load is held for two minutes. This is because when the reading on the oil pressure gauge reaches the design value, the steel strands are still in motion due to friction within the ducts; this movement occurs in the direction of tension. As the steel strands move in this tensioning direction, the oil pressure gauge shows a decrease in pressure, so it is necessary to replenish the oil pressure promptly, which is why the load is held for two minutes. The maximum limit is set because, after tensioning, the beam will experience creep, which results in an elastic arching effect; this is required by regulations. Additionally, steel strands have a certain tensile strength, and if over-tensioned, the strands may break. Moreover, to ensure that the beam retains a certain degree of elasticity, the steel strands should not be tensioned to their ultimate tensile strength – there needs to be some elastic margin.

This is the phenomenon of \"over-tensioning\" in the application of prestressed engineering; since prestressed steel bars experience prestress relaxation after tensioning, in order to overcome this relaxation caused by tensioning, the tensioning force applied to the prestressed bars must exceed the controlled stress by 5%, and the load must be maintained for a specified period of time.

The main purpose is to accelerate the early development of prestress tendon relaxation under high stress conditions, in order to reduce the prestress loss caused by stress relaxation.

In the tensioning procedure for heat-treated rebar or steel strands, an over-tensioning of 5% is applied followed by holding the load for 2 minutes; the purpose of this is to accelerate the early development of stress relaxation in the prestressed members under high-stress conditions, thereby reducing the loss of prestress caused by stress relaxation.

This is the phenomenon of \"over-tensioning\" in the application of prestressed engineering; since prestressed steel bars experience prestress relaxation after tensioning, in order to overcome this relaxation caused by tensioning, the tensioning force applied to the prestressed bars must exceed the controlled stress by 5%, and the load must be maintained for a specified period of time.

This is the phenomenon of \"over-tensioning\" in the application of prestressed engineering; since prestressed steel bars experience prestress relaxation after tensioning, in order to overcome this relaxation caused by tensioning, the tensioning force applied to the prestressed bars must exceed the controlled stress by 5%, and the load must be maintained for a specified period of time. Generally, a strain of 2% or 3% is used, and the load is held for two minutes. This is because when the reading on the oil pressure gauge reaches the design value, the steel strands are still in motion due to friction within the ducts; this movement occurs in the direction of tension. As the steel strands move in this tensioning direction, the oil pressure gauge shows a decrease in pressure, so it is necessary to replenish the oil pressure promptly, which is why the load is held for two minutes. The maximum limit is set because, after tensioning, the beam will experience creep, which results in an elastic arching effect; this is required by regulations. Additionally, steel strands have a certain tensile strength, and if over-tensioned, the strands may break. Moreover, to ensure that the beam retains a certain degree of elasticity, the steel strands should not be tensioned to their ultimate tensile strength – there needs to be some elastic margin.

The main purpose is to accelerate the early development of prestress tendon relaxation under high stress conditions, in order to reduce the prestress loss caused by stress relaxation.

In the tensioning procedure for heat-treated rebar or steel strands, over-tensioning by 5% and holding the load for 2 minutes is intended primarily to accelerate the early stage of relaxation of the prestressed members under high stress conditions, thereby reducing the loss of prestress caused by stress relaxation.

This is the phenomenon of \"over-tensioning\" in the application of prestressed engineering; since prestressed steel bars experience prestress relaxation after tensioning, in order to overcome this relaxation caused by tensioning, the tensioning force applied to the prestressed bars must exceed the controlled stress by 5%, and the load must be maintained for a specified period of time. Generally, a strain of 2% or 3% is used, and the load is held for two minutes. This is because when the reading on the oil pressure gauge reaches the design value, the steel strands are still in motion due to friction within the ducts; this movement occurs in the direction of tension. As the steel strands move in this tensioning direction, the oil pressure gauge shows a decrease in pressure, so it is necessary to replenish the oil pressure promptly, which is why the load is held for two minutes. The maximum limit is set because, after tensioning, the beam will experience creep, which results in an elastic arching effect; this is required by regulations. Additionally, steel strands have a certain tensile strength, and if over-tensioned, the strands may break. Moreover, to ensure that the beam retains a certain degree of elasticity, the steel strands should not be tensioned to their ultimate tensile strength – there needs to be some elastic margin.