## 6 Conclusions  
This paper proposes a method to quantify the prestress force in the precast prestressed segmental beams based on the strain measurement and neutral axis location. Under the plane-remains-plane assumption, neutral axis location is obtained by using the strain measurements. The static force equilibrium of a specific cross-section of the precast segmental beam is established to calculate the prestress force. The accuracy and reliability of the proposed method are verified through experimental and numerical studies on a prestressed segmental beam. The experimental results verify that the prestress forces can be predicted by using the strain measurement during the post-tensioning process, or during service through a dynamic test. The results show that the theoretical prediction results have certain differences when compared with the experimental measured results obtained near the segmental joints. Discussions on the possible sources, such as the concrete modulus of elasticity and uncertainty of strain measurements that may lead to the inaccurate predictions of the prestress force, are provided. However, using the strains measured in the middle of the segment of the beam for calculating the prestress force shows a good correlation with the theoretical prediction. In the numerical verification, five prestress levels from 62 kN to 100 kN are used to verify the credibility of the proposed method. Similar to the experimental verifications, the results at the middle of the segment match well with the experimental results than that obtained from the location near the joints of the beam. Discussions are provided by showing stress distribution contour in the longitudinal direction of the cross-section obtained in numerical simulations. It is found that the plane-remains-plane assumption is not valid at sections near the segmental joints, which explains why a relatively big difference is observed when measured data near the joint between the segments are used in the analysis. The results suggest that the measurements should be made at locations away from the joints in segmental beams for quantifying the prestress force. The reliability of the proposed method in identifying the prestress force of segmental beams in service condition through a dynamic test is also verified. The results demonstrate that the proposed method can be used for identifying the prestress force. To sum up, both the experimental test and numerical simulation results demonstrate that the proposed approach can reliably identify the change in prestress force, and well quantify the prestress force level when selecting the strains away from the joints. Conceptualization, H.H., J.L. and H.L. ; methodology, H.L., J.L., Y.X. and H.H. ; validation, H.L., T.D.L. and T.M.P. ; formal analysis, H.L. and Y.X. ; investigation, J.L. and T.M.P. ; data curation, H.L. and T.D.L. ; writing--original draft preparation, H.L. and Y.X. ; writing--review and editing, J.L., H.H. and T.M.P. ; visualization, H.L. ; supervision, J.L. and H.H. ; project administration, J.L. and H.H. ; funding acquisition, H.H. All authors have read and agreed to the published version of the manuscript. This research was funded by: Australian Research Council, grant number: FL180100196. The data presented in this study might be available on reasonable request from the corresponding author. The work described in this paper was supported by the Australian Research Council Laureate Fellowship project FL180100196: Development of multi-hazard resilient and sustainable infrastructure. The first author would like to acknowledge the Australian Research Training Program Scholarship for supporting her PhD study at Curtin University. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Applied Prestress Force in the** & **Identified Average Prestress** & **Relative Error (\%)** \\
**Numerical Model (kN)** & **Force (kN)** & **Relative Error (\%)** \\ \hline
107 & 108.41 & 1.32 \\ \hline \hline \end{tabular}
\end{table}