What Is the Prestressed Concrete Prestress Losses & Effective Force Calculator?
Prestress losses represent the progressive reduction in tension stress experienced by prestressing tendons over the structural lifespan of a concrete member.
How Does the Prestressed Concrete Prestress Losses & Effective Force Calculator Work?
Summing instantaneous elastic shortening (ES) and long-term creep (CR), shrinkage (SH), and relaxation (RE) yields total loss Δf_p, leaving effective stress f_pe = f_pj - Δf_p.
Prestressed Concrete Prestress Losses & Effective Force Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Total lump-sum prestress loss sums elastic shortening, creep, shrinkage, and relaxation, leaving effective residual strand tension.
How to Use the Prestressed Concrete Prestress Losses & Effective Force Calculator
- Enter initial jacking stress in MPa.
- Specify individual loss components or use standard AASHTO/PCI estimates.
- Read total losses, percentage loss, and remaining effective prestress.
Step-by-Step Example Calculation
Grade 270 Low-Relaxation Strand in Bridge Girder
Input Values:
Understanding Your Result
Total Losses: Total reduction in tendon stress in MPa.
Effective Prestress (f_pe): Long-term residual stress available to resist external loads.
Loss Percentage: Fraction of jacking stress lost (typically 15% to 22%).
Factors That Affect the Result
- Concrete compressive strength f'c, ambient relative humidity, volume-to-surface ratio, and strand metallurgy.
When Should You Use This Calculator?
- Designing precast prestressed bridge girders, post-tensioned parking garage slabs, and precast hollow-core planks.
Assumptions & Limitations
- Uses lump-sum component method; detailed time-step analysis can track gradual humidity shifts.
Frequently Asked Questions
Calculation Accuracy & Reference Note
AASHTO LRFD Bridge Design Specifications and PCI Design Handbook compliant.