Resource
Impact-Echo Testing of Precast T-Beams
Release time:
2025-09-29 11:48
Project Overview
This project involved impact-echo testing of prestressed precast T-beams to assess the internal integrity of tendon ducts and identify potential defects that could affect long-term performance. Prior to testing, the duct alignment was marked on the beam sides based on design drawings, and test zones were established.
Testing Procedure
Beam Details: Total beam length: 30 m
End zones (0–3 m range): Thickness varying from 50 cm to 30 cm
Midspan: Constant thickness of 30 cm
Calibration: Wave velocity calibrated using a single-channel method at ~3906 m/s.
Test Coverage:
Beam #1: 3 ducts tested (left and right sides)
Beam #2: 2 ducts tested (left and right sides)
Method: Sequential impact-echo measurements were conducted at all designated points, with real-time preliminary analysis carried out on site.
Testing Principle
If the energy distribution in the spectrogram does not concentrate near the actual thickness of the beam, it indicates that stress waves may have undergone diffraction or reflection at defect interfaces (such as cracks or voids) instead of propagating directly to the bottom surface.
Results
Beam #1:
Duct 2 (both sides near the beam end): small-scale minor defects detected
Duct 3 (right side, 1.95 m–2.25 m): continuous minor defects detected
Other test areas: no significant anomalies observed
Beam #2:
Duct 1 (both sides near the beam end): small-scale minor defects detected
Duct 2 (right side, 0.3 m–0.45 m): minor defect detected
Other test areas: no significant anomalies observed
Evaluation
Engineering Assessment: Both beams were generally sound, with only localized minor defects near duct ends and limited zones of continuous light defects. These anomalies should be monitored but do not significantly compromise overall structural performance.
Testing Method Performance: The impact-echo technique successfully identified subtle internal irregularities, demonstrating its value for non-destructive evaluation of precast elements.
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