What is Prestressing Force after Immediate Loss given the Initial Prestress? The initial force coefficient (FC. Area of concrete is defined as concrete area in beam or column excluding reinforcement. A high degree of workmanship and control is required. 1) Initial : It can be subdivided into two stages. g g g 2 i g i cir cir I M e I P e A P f K = + (Eq. How to calculate Prestressing Force after Immediate Loss given the Initial Prestress? Back to Structural Bridge Design Category. The value of the initial prestress force Pm0(x) (at time t = t0) applied to the concrete immediately after tensioning and anchoring (post-tensioning) or after transfer of prestressing (pre-tensioning) is obtained by subtracting from the force at tensioning Pmax the immediate losses Pi(x) and should not exceed the following value: A high degree of workmanship and control is required. The sum of the top and bottom prestressing forces is 2874.3975kN (2432.1825 + 442.215) - so where is the value of 2855kN coming from? Modulus of Elasticity of Steel Reinforcement is a measure of its stiffness. Two types of prestressed concrete can be distinguished depending on when the steel is tensioned. This page has been translated for your convenience with an automatic translation service. Therefore the initial stressp.ef, s = 160 / 415.27 s = 385.3 MPa Hence, as described earlier, a prestressing force of 160 kN was induced onto the section, and using the theoretical prediction equation 3.9 the ultimate stress can be found. Modulus of Elasticity of Steel Reinforcement: Chandana P Dev has created this Calculator and 600+ more calculators! Mithila Muthamma PA has verified this Calculator and 800+ more calculators! c) at time of prestressing A ps = 3 - " dia. Force (kips) Initial Percent of Ultimate Load (%) Residual Load at 72 Hours (kips) Percent Stress Loss At 72 Hours (%) 34 82.3 26 23.5 28 67.8 27 3.6 This example indicates that strand, when kept in an overstressed condition (greater than 0.75 f' s), results in a significant reduction of prestressing force due to the change in creep . Thanks. The disadvantages of prestressed concrete include: How to Calculate Initial Strain in Terms of Initial Prestressing Force? 7 losses in prestress 1. In this formula, Initial strain uses Initial prestress force, Area of prestressing steel & Modulus of Elasticity of Steel Reinforcement. Expensive equipment is needed and there are complex safety requirements. (8) provides values between 320 and 600 (see Fig. The values of k7 and k8 are used to check the prestressing stresses at transfer after all immediate losses are considered and if these are exceeded then the initial prestressing needs to be reduced. In this formula, Prestressing force Po uses Initial prestress force, Area of concrete & Transformed area of prestress section. With reference to the attached screenshots, I was hoping someone could explain how ASBD is calculating the total initial prestressing force (without reductions). We can use 1 other way(s) to calculate the same, which is/are as follows -, Initial Strain in Terms of Initial Prestressing Force Calculator. Initial Strain in Terms of Initial Prestressing Force Solution, Modulus of Elasticity of Steel Reinforcement. To use this online calculator for Prestressing Force after Immediate Loss given the Initial Prestress, enter Initial prestress force (Pi), Area of concrete (Ac) & Transformed area of prestress section (At) and hit the calculate button. The Initial Strain in Terms of Initial Prestressing Force in the above equation is found out by considering the initial prestress force over the cross sectional area of steel(tendons) and is represented as. Special alloy steels are more expensive than traditional steels used in reinforced concrete. Prestressing is most often carried out using tensioned cables embedded in concrete. Normally prestressing wires are arranged in the a) upper part of the beam b) lower part of the beam c) center d) anywhere Ans: b 140. 3) Final : It can be subdivided into two stages. Initial strain is denoted by pi symbol. Can't find what you're looking for? To use this online calculator for Initial Strain in Terms of Initial Prestressing Force, enter Initial prestress force (Pi), Area of prestressing steel (Ap) & Modulus of Elasticity of Steel Reinforcement (Es) and hit the calculate button. Initial Strain in Terms of Initial Prestressing Force calculator uses Initial strain = Initial prestress force/(Area of prestressing steel*Modulus of Elasticity of Steel Reinforcement) to calculate the Initial strain, The Initial Strain in Terms of Initial Prestressing Force in the above equation is found out by considering the initial prestress force over the cross sectional area of steel(tendons). a) During tensioning of steel b) At transfer of prestress to concrete. Area of prestressing steel is the total cross sectional area of tendons. Let me start with your last point in that there is no way to alter the initial prestress. To use this online calculator for Initial Strain in Terms of Initial Prestressing Force, enter Initial prestress force (Pi), Area of prestressing steel (Ap) & Modulus of Elasticity of Steel Reinforcement (Es) and hit the calculate button. If within tolerance, no worries. Initial Strain in Terms of Initial Prestressing Force Solution, Modulus of Elasticity of Steel Reinforcement. Area of prestressing steel is the total cross sectional area of tendons. What is Initial Strain in Terms of Initial Prestressing Force? Mithila Muthamma PA has verified this Calculator and 800+ more calculators! The Prestressing Force after Immediate Loss given the Initial Prestress defines the relation between the initial prestressing force on the section and the force immediately after the stress loss is calculated using. Here is how the Initial Strain in Terms of Initial Prestressing Force calculation can be explained with given input values -> 0.05 = 200000/(2E-05*200000000000). Area of prestressing steel is the total cross sectional area of tendons. Stages of Loading The analysis of prestressed members can be different for the different stages of loading. Thanks also for including a couple of screen shots to help explain your query, but if you have any further questions on this it is better if you also zip up a copy of your data file and attach it to the post as it makes it easier to directly replicate your issues. How to Calculate Prestressing Force after Immediate Loss given the Initial Prestress? The stages of loading are as follows. Expensive equipment is needed and there are complex safety requirements. The reduced value of prestress you are seeing (2756kN from 2855) is the reduced value of prestress before immediate losses. Load condition Erection time Formula Average Initial prestress 1 + [C.sub.a] 1.96 Prestress loss [[alpha].sub.a] (1 + 1.00 [chi] . Assuming the force at transfer is 0.75*270 ksi the initial prestress force on the section is 0.75*270*1.5 = 303.75 kips. An initial tension load of between 5% and 25% of the final load is applied to the strands to take out slack and establish an initial point for the measurement of elongation. Initial Strain in Terms of Initial Prestressing Force, Residual Strain in Terms of Prestressing Force after Immediate Loss, Prestressing Force after Immediate Loss given the Initial Prestress, Initial prestress when prestress after immediate loss is given, Strain in Concrete in Terms of prestressing Force after Immediate Loss, Prestress Force After Immediate Loss when Prestress Drop is Given, Prestress Drop when Pressure After Immediate Loss is Known, Modular Ratio when Prestress after Immediate Loss is Known, Residual Strain in Steel for Known Strain due to Elastic Shortening, Initial Strain in Steel for Known Strain due to Elastic Shortening. Autodesk does not warrant, either expressly or implied, the accuracy, reliability or completeness of the information translated by the machine translation service and will not be liable for damages or losses caused by the trust placed in the translation service. In practice, the force in post-tensioned members at transfer is not constant owing to friction. Initial prestress Fig. 7.6.4.2.3 Form Finding Modulus of Elasticity of Steel Reinforcement is a measure of its stiffness. Prestressing force Po = Initial prestress force*Area of concrete/Transformed area of prestress section Po = Pi*Ac/At This formula uses 4 Variables Variables Used Prestressing force Po - (Measured in Newton) - Prestressing force Po is the prestressing force after immediate losses. The determination of initial cable forces in a prestressed concrete cable-stayed bridge for a given vertical profile of deck under its dead load is an important but difficult task that affects. 2). The initial prestress force of a cable is calculated using below empirical formula: where F is the initial prestress force, is the yield stress of the cable, and A is the cross-sectional area of the cable. The Initial Strain in Terms of Initial Prestressing Force in the above equation is found out by considering the initial prestress force over the cross sectional area of steel(tendons) and is represented as. Special alloy steels are more expensive than traditional steels used in reinforced concrete. How to calculate Initial Strain in Terms of Initial Prestressing Force? The sum of the top and bottom prestressing forces is 2874.3975kN (2432.1825 + 442.215) - so where is the value of 2855kN coming from? The cables can be tensioned before concreting the element - pre-tension - or after - post-tension. Initial strain here refers to the initial or immediate amount of strain in steel. How many ways are there to calculate Initial strain? Solved by dave_geeves. force in the strand by two inde-pendent methods. The disadvantages of prestressed concrete include: It is also called as the reduced value of prestressing force after elastic shortening, anchorage slip and loss due to friction. Modulus of Elasticity of Steel Reinforcement: Chandana P Dev has created this Calculator and 600+ more calculators! The prestress force was estimated indirectly by a formula calculating the loss of prestress using the hydraulic pressure measured externally at the jacked end of the structure and the change in the length of the tendon before and after prestressing [6-8]. The prestressing stress (or force) applied to . A high degree of workmanship and control is required. 186 230 230 168 Initial prestressing force = 173.3 k: From Figures 2-5 and 2-6, the distance from the bottom of the beam to the centroid of Group 3 is 4.0 in. Initial Strain in Terms of Initial Prestressing Force, Residual Strain in Terms of Prestressing Force after Immediate Loss, Prestressing Force after Immediate Loss given the Initial Prestress, Initial prestress when prestress after immediate loss is given, Strain in Concrete in Terms of prestressing Force after Immediate Loss, Prestress Force After Immediate Loss when Prestress Drop is Given, Prestress Drop when Pressure After Immediate Loss is Known, Modular Ratio when Prestress after Immediate Loss is Known, Residual Strain in Steel for Known Strain due to Elastic Shortening, Initial Strain in Steel for Known Strain due to Elastic Shortening. Special alloy steels are more expensive than traditional steels used in reinforced concrete. Prestressing force Po is denoted by Po symbol. 2) Intermediate : This includes the loads during transportation of the prestressed members. How many ways are there to calculate Prestressing force Po? Initial Strain in Terms of Initial Prestressing Force calculator uses Initial strain = Initial prestress force/(Area of prestressing steel*Modulus of Elasticity of Steel Reinforcement) to calculate the Initial strain, The Initial Strain in Terms of Initial Prestressing Force in the above equation is found out by considering the initial prestress force over the cross sectional area of steel(tendons). Most common method of prestressing used for factory production is a) Long line method b) Freyssinet system c) Magnel-Blaton system Initial strain here refers to the initial or immediate amount of strain in steel. The loss of stress in the tendon is therefore still given by Equation 4.1. The Prestressing Force after Immediate Loss given the Initial Prestress defines the relation between the initial prestressing force on the section and the force immediately after the stress loss and is represented as. The Initial Strain in Terms of Initial Prestressing Force in the above equation is found out by considering the initial prestress force over the cross sectional area of steel(tendons) is calculated using. Prestress Loss 2. This is not an official translation and may contain errors and inaccurate translations. For practical cases, Eq. I believe the software does this until an appropriate convergence is reached and then reports a %age of the initial prestress that needs to be used (an information message pops up when the calcs are performed). The final strand force (measured as gauge pressure) is obtained from the shop drawings or plant engineering. Thanks for an interesting question, and it is good to know that the printed output is being checked occasionally to verify the results. So, to limit the initial prestress (before any loss whatsoever) to 70% of fpk, you would set k1 to 0.7 (where the recommended value is 0.8). a) At service, during operation. Prestressing Force after Immediate Loss given the Initial Prestress calculator uses Prestressing force Po = Initial prestress force*Area of concrete/Transformed area of prestress section to calculate the Prestressing force Po, The Prestressing Force after Immediate Loss given the Initial Prestress defines the relation between the initial prestressing force on the section and the force immediately after the stress loss. What is Initial Strain in Terms of Initial Prestressing Force? I must admit that the calculations are not as clear as they could be for this case, which I have raised with the developers before, but I do believe they are essentially correct. 10+ Pre-Tensioned Axial Members Calculators, Initial Strain in Terms of Initial Prestressing Force Formula. Expensive equipment is needed and there are complex safety requirements. Prestressing tendons are installed and jacked to provide an initial prestress of 200 psi and final prestress of 175 psi across the transverse joints of the slabs. How to calculate Initial Strain in Terms of Initial Prestressing Force? The formula to determine the initial equilibrium is. The prestressing stress (or force) . Initial Strain in Terms of Initial Prestressing Force calculator uses. prestressing force immediately after the prestress has been applied to the concrete. Initial Strain in Terms of Initial Prestressing Force calculator uses Initial strain = Initial prestress force /( Area of prestressing steel * Modulus of Elasticity of Steel Reinforcement ) to calculate the Initial strain, The Initial Strain in Terms of Initial Prestressing Force in the above equation is found out by considering the initial prestress force over the cross sectional area of . 2. In this formula, Initial strain uses Initial prestress force, Area of prestressing steel & Modulus of Elasticity of Steel Reinforcement.
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