You mention that you could manually change k7and k8, but in fact it is more common to limit k1 and/or k2 (Cl 5.10.2.1), which is not exposed in the materials form. The value of prestress that you have calculated, using k7 and k8, is the value that you would expect when all immediate losses have been considered. 3) Final : It can be subdivided into two stages. I hope this has helped and if this has answered your query then please mark my reply as an answer so that others may benefit. 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. Area of prestressing steel is the total cross sectional area of tendons. The disadvantages of prestressed concrete include: If there is, apply the ratio of the difference to correct the values. Initial strain is denoted by pi symbol. The definition of the variables in the above equation and their values for this example are as follows: A ps = area of prestressing steel (in 2) . Initial Strain in Terms of Initial Prestressing Force Calculator 2. Prestressing Force after Immediate Loss given the Initial Prestress calculator uses. The stages of loading are as follows. 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. How many ways are there to calculate Prestressing force Po? A high degree of workmanship and control is required. 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. 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 force is then checked by measur-ing strand elongation and comparing this measured value with a theoretical (calculat- Initial Strain in Terms of Initial Prestressing Force Calculator How to calculate Initial Strain in Terms of Initial Prestressing Force? 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. 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. (7.29) where [ KL] 0 is the initial linear stiffness matrix, [ KL] 0 is the initial nonlinear stiffness matrix, { U } 0 is the variation of the coordinate, { P } 0 is the prestressed force, and { R } 0 is the residual force or imbalance force at each node. The reduced value of prestress you are seeing (2756kN from 2855) is the reduced value of prestress before immediate losses. Stages of Loading The analysis of prestressed members can be different for the different stages of loading. Solved: Initial prestress calculations - Autodesk Community The prestressing stress (or force) applied to . Mithila Muthamma PA has verified this Calculator and 800+ more calculators! 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. The equation given is as follows: % SR = [lift (R 0.55) X 100 (1) for R > 0.55 where % SR = % stress relaxation t = test time in hrs. What are the stages of loading in prestressing process? ELASTIC SHORTENING - Loss of prestress force 4.1 INTRODUCTION - 1library 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. Special alloy steels are more expensive than traditional steels used in reinforced concrete. PDF Transfer Length of Prestressing Strand as a Function of Draw-In - PCI In this formula, Initial strain uses Initial prestress force, Area of prestressing steel & Modulus of Elasticity of Steel Reinforcement. The elongations for the side of initial prestress is 8mm for both beams, and for the other side, 70%fpu beam has 20mm, 35%fpu beam has 12mm. Prestressing is most often carried out using tensioned cables embedded in concrete. Area of prestressing steel is the total cross sectional area of tendons. How to calculate Prestressing Force after Immediate Loss given the Initial Prestress? R = ratio of initial stress to yield stress This description of stress relaxation is a simple, straight line semi-log curve with 0% SR at 1.0 hr., and with the slope dependent upon the initial stress level . Initial prestress force = Prestressing force Po*Transformed area of prestress section/Concrete Area Go Strain in Concrete in Terms of prestressing Force after Immediate Loss Strain in concrete = Prestressing force Po/ (Concrete Area*Modulus of Elasticity Concrete) Go Prestress Force After Immediate Loss when Prestress Drop is Given 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. EQUATION SET DEVELOPMENT The use of these equations requires a preliminary estimate of the effective-ness ratio,R. Share your knowledge, ask questions, and explore popular Structural Bridge Design topics. By my calculation this should be: I have included the material properties for the prestressing tendons as a screenshot. Likewise, the calculation for the reduced value of the prestressing force (2756.466kN) does not appear to align with the requirements of EC2 Cl 5.10.3(2). The loss of the first prestressing force by the second prestressing force is 8.702% of the prestressing force, 4.286tf. By the first prestressing the hoop tension of the cylinder under internal water pressure was reduced to 25.228% at the node 23. Expensive equipment is needed and there are complex safety requirements. i) at the point of no movement = 0.802. The initial force coefficient (FC. Prestressing Force after Immediate Loss given the Initial Prestress It is not, however, necessary to as-sume all losses will have . 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 Prestressing Force after Immediate Loss given the Initial Prestress using this online calculator? Initial Strain in Terms of Initial Prestressing Force calculator uses. 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). Welcome to Autodesks Structural Bridge Design Forums. prestressing force immediately after the prestress has been applied to the concrete. PDF Lecture 24 - Prestressed Concrete - Learn Civil Engineering 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). 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. This is not an official translation and may contain errors and inaccurate translations. 7 losses in prestress - SlideShare g g g 2 i g i cir cir I M e I P e A P f K = + (Eq. PDF Design Step 5 - Design of Superstructure Prestressed - Indiana in., dividing the total initial force by this area results in a compressive stress over the total transformed area of 303.75/109 = Beam length 3.5m. 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). Steel is not necessarily in direct contact with concrete. Load condition Erection time Formula Average Initial prestress 1 + [C.sub.a] 1.96 Prestress loss [[alpha].sub.a] (1 + 1.00 [chi] . 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. Thanks for your thorough response - much appreciated. 1) Initial : It can be subdivided into two stages. Introduction In prestressed concrete applications, most important variable is the prestress. 3 - See Section 5.5 for prestressing forces Sample Calculations for Flexural Stresses at Transfer Definitions: P t = Initial prestressing force taken from Table 5.5-1 (kips) A g = Gross area of the basic beam (in2) e = Distance between the neutral axis of the noncomposite girder and the center of gravity of the prestressing steel (in.) Initial prestress force is the force which is applied to the tendons by the jack. 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. What are the disadvantages of prestressed concrete? Mithila Muthamma PA has verified this Calculator and 800+ more calculators! 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. In this formula, Initial strain uses Initial prestress force, Area of prestressing steel & Modulus of Elasticity of Steel Reinforcement. Comprehensive Design Example for Prestressed Concrete (PSC) Girder Increases in Prestressing Force - Results and Discussion A high degree of workmanship and control is required. Expensive equipment is needed and there are complex safety requirements. What is initial prestressing force? 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. 7 losses in prestress 1. 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). Let me start with your last point in that there is no way to alter the initial prestress. Mithila Muthamma PA has verified this Calculator and 800+ more calculators! A high degree of workmanship and control is required. Understanding Prestressing: Pre-tension or Post-tension? - FORCE Prestressing Force after Immediate Loss given the Initial Prestress Initial Strain in Terms of Initial Prestressing Force Solution, Modulus of Elasticity of Steel Reinforcement. The disadvantages of prestressed concrete include: How to Calculate Initial Strain in Terms of Initial Prestressing Force? What is Prestressing Force after Immediate Loss given the Initial Prestress? If all iterative calculations were shown in the output then there would be 10s of pages, so only the last converged value is used in the printed results. Most common method of prestressing used for factory production is a) Long line method b) Freyssinet system c) Magnel-Blaton system Ratio of transfer length to draw-in vs. initial prestress and power of bond stress-slip relationship. Initial prestress force is the force which is applied to the tendons by the jack. What is Initial Strain in Terms of Initial Prestressing Force? Design Step 5.4.4 - Calculate the prestressing stress at transfer fpt = Stress immediately prior to transfer - fpES = 202.5 - 13.7 = 188.8 ksi Design Step 5.4.5 - Calculate the prestressing force at transfer Pt = Nstrands(Aps)(fpt) = 44(0.153)(188.8) = 1,271 kips (initial loss = 6.77%) 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). Initial prestress force applied to the concrete Special alloy steels are more expensive than traditional steels used in reinforced concrete. 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. Prestress does not remain constant (reduces) with time. Special alloy steels are more expensive than traditional steels used in reinforced concrete. Handling out-of-tolerance strand elongations D 186 230 230 168 What are the disadvantages of prestressed concrete? PDF APPENDIX E - EXAMPLE CALCULATIONS - California Department of c) at time of prestressing A ps = 3 - " dia. This page has been translated for your convenience with an automatic translation service. Transformed area of prestress section is the area of the member when steel is substituted by an equivalent area of concrete. The stages of loading are as follows. Civil Engineering Questions (1-178) Subject/Chapter::Concrete However, the immediate losses are calculated as a function of the initial prestress, so this becomes an iterative procedure. Prestress Force Identification for Externally Prestressed Concrete Beam When I was first introduced to Eurocodes, I found this quite difficult to fathom, especially when comparing it to the simpler approach we adopted in BS5400 but I have now got used to it. How many ways are there to calculate Initial strain? Ask the community or share your knowledge. Modulus of Elasticity of Steel Reinforcement is a measure of its stiffness. Initial strain is denoted by pi symbol. a) During tensioning of steel b) At transfer of prestress to concrete. Modulus of Elasticity of Steel Reinforcement: Chandana P Dev has created this Calculator and 600+ more calculators! Thanks for an interesting question, and it is good to know that the printed output is being checked occasionally to verify the results. 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). Prestressing - an overview | ScienceDirect Topics Finally, on a similar point, I have not yet found a way to directly amend the initial prestressing force applied to the tendons other than manually amending the values for k7 and k8. Go to Solution. 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. With reference to the attached screenshots, I was hoping someone could explain how ASBD is calculating the total initial prestressing force (without reductions). 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. 7.6.4.2.3 Form Finding 10+ Pre-Tensioned Axial Members Calculators, Initial Strain in Terms of Initial Prestressing Force Formula. = 0.20, K = 0.0002 (informational only). Stages of Loading The analysis of prestressed members can be different for the different stages of loading. Prestressing Force after Immediate Loss given the Initial Prestress Solution. The final strand force (measured as gauge pressure) is obtained from the shop drawings or plant engineering. 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. 2) Intermediate : This includes the loads during transportation of the prestressed members. 10+ Pre-Tensioned Axial Members Calculators, Initial Strain in Terms of Initial Prestressing Force Formula. 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.

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