How to calculate the single strand tension control force P
Control stress x total cross-sectional area of steel strand = tension control force. The relationship between control stress and control force is linear regression, and the condition is within the elastic range, that is, not more than 0.8x1860
Control stress x total cross-sectional area of steel strand = tension control force. The relationship between control stress and control force is linear regression, and the condition is within the elastic range, that is, no more than 0.8x1860
both the control stress and the tension force outside the anchor are corresponding to the oil meter reading of the jack (the control reading of the oil meter is to bring the tension force outside the anchor into the equation of roof calibration). The control stress under the anchor is the control stress at the beginning of the calculation of the steel strand, that is, the control stress outside the anchor minus the loss of the anchor mouth (generally, the loss of the anchor head is taken as 6%)
the equation of top calibration is actually the relationship between the force of LKN when the jack is calibrated and the reading of one grid on the dial
In other words, the external control stress of the anchor is the value on the oil pressure gauge divided by the area of the steel bundle, and the control stress under the anchor is the value of the external control stress of the anchor after decting the loss of the anchor head 
extended data:
the value of tension control stress is related to the method of prestressing. For the same steel grade, the value of pretensioning method is higher than that of post tensioning method. This is because the pre tensioning method and post tensioning method have different ways to establish prestress. Pretensioning method is to tension the steel bar on the pedestal before pouring concrete, so the tension stress established in the prestressed steel bar is the tension control stress σ con
the post tensioning method is to tension the steel bar on the concrete member. At the same time, the concrete is compressed. The tension control stress indicated by the jack of the tensioning equipment has dected the steel bar stress after the elastic compression of the concrete. For this reason, the design of post tensioned component is very important σ Con value should be lower than pretension method
The determination oftension control stress value is also related to the steel grade of prestress. As the prestressed concrete is made of high-strength steel bars, its plasticity is poor, so the control stress can not be too high
Pp=(P1- e-( kx + μθ)/ kx+ μθ
PP - average tensile force of steel strand (n), P - tensile force at the tensile end of steel strand (n); K - friction coefficient of local deviation per meter of ct length; μ— The friction coefficient between the steel strand and the channel wall; θ— The sum of the included angles (RAD) from the tension end to the tangent of the ct part of the calculation section curve; X-length of channel from tension end to calculation section< br />
1. Calculation parameters:
1. K-coefficient of influence of local deviation per meter of ct on Friction: 0.0015
2 μ— Friction coefficient between prestressed reinforcement and ct wall: 0.25
3. Ap - measured cross-sectional area of prestressed reinforcement: 139 mm2
4. EP - measured elastic molus of prestressed reinforcement: 1.95 × 105 n / mm2
5 σ k=0.75Ryb=0.75 × 1860 = 1395 n / mm2
7. Tension control force of single strand tension end: P= σ KAP = 193905n
8. Calculation length of Jack: 35cm
9. Length of tool anchor: 5cm
2. Calculation of theoretical elongation ring tension:
take N1 strand as an example:
elongation at one end of N1 strand:
P = 0.75 × one thousand eight hundred and sixty × 139 = 193905n
x = 11.322m; X curve = 1.018m
L straight = 11.322 + (0.35 + 0.05) = 11.722m
L curve = 1.018m
θ Qu = 4 °×π/ 180 = 0.0698rad
k x curve+ μθ= zero point zero zero one five × 1.018+0.25 × 0.0698=0.019
Pp=193905 × 1-e-0.019/0.019=192074N
Δ L = PP L / (AP EP) = 192074 × 1.018/139 × one point nine five × 105=7.2mm
Δ L straight = ppl straight / (AP EP) = 192074 × 11.722/139 × one point nine five × 105=83.1mm
( Δ L-tune+ Δ L (straight) × 2=(7.2mm+83.1mm) × 2=180.6mm
Tension calculation of prestressed steel strand Φ J15.24 prestressed steel strand, tension control stress σ Con = 0.75ry = 1395mpa, single tension control force F = 1395 × 140=195.3KN
100% σ The calculation formula of con theoretical elongation is as follows:
- tensile force of steel strand at tensile end (n); K
- if you have any questions about the calculation of elongation value
see Volume II of concrete design principles< br />..
generally there will be over tension of 3%
OK
stress = stress * area * tidal rise coefficient
even no score
the answer is not interesting