非破壞性檢測近年來已被應用於混凝土構件檢測，例如預力橋梁維護與更新等方面的評估。本篇研究提出兩種藉由變位量測來進行預力識別之方法。這些方法是基於Euler梁理論，透過考量邊界影響後的梁上任一點變位來估計預力大小，且兩個方法都需知道構件之撓曲剛度。梁的變位部分則是透過數次加載垂直側向力的實驗，利用短期的變位量測而得。同時，變位量測的精準度也是影響識別結果的關鍵。並且在服務狀態下，試驗後拉法預力梁仍滿足壓力軟化理論。此外，兩種識別方法皆可應用於任何邊界條件的細長混凝土梁。

This article describes two static methods which can be used for the axial load estimation in truss bridges. In both procedures, flexural displacements must be measured in a short–term at given cross sections along the beam under investigation and subjected to an additional vertical load. The proposed methods were verified by numerical and laboratory tests on beams of a small–scale truss bridge prototype made by aluminum alloy and rigid nodes. Generally, if the higher second-order effects are induced during testing and the corresponding flexural displacements are precisely measured, it is easy to identify the tensile and compressive forces. The two methods can be valuable techniques in situ since safety inspections will progressively become very important in the near future.