# State-of-the-Art Review on Determining Prestress Losses in Prestressed Concrete Girders
## 2 Works Conducted by Researchers Worldwide
### Testing Methods  
Testing methods are in general required for estimating prestress losses, and include five typologies (Table 3): (1) static load testing to determine crack initiation or crack re-opening loads to obtain the available compressive stress in the bottom flange of a PC girder [23; 28; 54; 55]. (2) Severing the prestressing tendon by cutting it into a representative exposed length after placing strain gauges on the tendon [23; 56]. (3) Relating the tension in the tendon to a vertical deflection recorded when known weights are suspended from it on a representative exposed length [54; 57]. (4) Determining the side pressure to close the induced crack in a small cylindrical hole drilled adjacent to the tendon in the bottom flange of a PC girder [55; 58]. (5) Vibration testing to determine the natural frequencies and/or dynamic responses of a PC girder [59; 60; 61; 62; 63; 64; 65]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Author** & **Year** & **Numerical Solution** & **Dynamic Model** & **Result and Finding** \\ \hline [PERSON] and [PERSON] [39] & 2000 & Analytical & UnCracked PC girders & \begin{tabular}{c} Increase in prestress \\ force slightly decreases \\ the natural frequencies \\ \end{tabular} \\ \hline [PERSON] et al. [43] & 2004 & \begin{tabular}{c} Analytical simulation of \\ tests performed \\ by [PERSON] et al. [32] \\ \end{tabular} & UnCracked PC girders & \begin{tabular}{c} Increase in prestress \\ force slightly increases \\ the natural frequencies \\ \end{tabular} \\ \hline [PERSON] and [PERSON] [44] & 2005 & Analytical & UnCracked PC girders & \begin{tabular}{c} Increase in prestress \\ force slightly decreases \\ the natural frequencies \\ \end{tabular} \\ \hline [PERSON] and [PERSON] [45] & 2006 & Analytical & UnCracked PC girders & \begin{tabular}{c} Increase in prestress \\ force does not affect the \\ natural frequencies \\ \end{tabular} \\ \hline [PERSON] [46] & 2008 & FE & UnCracked PC girders & (as above) \\ \hline [PERSON] et al. [47] & 2016 & Analytical & UnCracked and Cracked PC girders & (as above) \\ \hline [PERSON] et al. [48] & 2019 & \begin{tabular}{c} FE simulation of tests \\ performed by \\ [PERSON] et al. [37] and \\ [PERSON] et al. [49] \\ \end{tabular} & Cracked PC girders & \
\begin{tabular}{c} Increase in prestress \\ force slightly increases \\ the natural frequencies \\ \end{tabular} \\ \hline [PERSON] et al. [50] & 2019 & Analytical & UnCracked PC girders &
\begin{tabular}{c} Increase in prestress \\ force does not affect the \\ natural frequencies \\ \end{tabular} \\ \hline [PERSON] et al. [53] & 2020 & Analytical & UnCracked and Cracked PC girders & (as above) \\ \hline [PERSON] et al. [51] & 2021 & Analytical & UnCracked PC girders & (as above) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Numerical investigations on the relation between prestress force and dynamics of PC girders. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Method** & **Reference** & **Testing on a PC Girder** & **Result and Finding** \\ \hline \multirow{4}{*}{(1) Destructive} & & Static test to determine crack & \\  & & initiation or crack re-opening & \\ \cline{1-1}  & & loads to obtain the compressive & \\ \cline{1-1}  & & stress in the bottom flange & \\ \hline \multirow{4}{*}{(2) Destructive} & & \multirow{4}{*}{[23; 56]} & Severing the prestressing tendon & \\ \cline{1-1}  & & by cutting it into an exposed & \\ \cline{1-1}  & & length after placing strain gauges & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Testing methods for determining prestress losses in PC girders. **Methods 1 and 2** are destructive approaches which cause damages. In Method 1, a large amount of vertical loads must be applied to involve crack initiation, or to force a main crack to form in the same location as a monitored crack. **Method 3** is a semidestructive test for exposed tendons, and involves accurately determining the exposed length for calculations. **Method 4** is a NDT approach for embedded tendons which involves a negligible local damage along the PC span girder.