Segmental post-tensioned (PT) bridges are major structures that carry significant traffic.
Recent investigations of these bridges have identified voids in their ducts. and some of
these exposed strands at these void locations are undergoing corrosion. The corrosion of
strands may lead to the failure of tendons. As such, an effective inspection process for
identifying these voids is needed. From a literature review, several non-destructive
testing (NDT) methods are compared for applicability in inspecting voids in external
tendons. The impact echo (IE), ultrasonic pulse velocity (UPV), and sounding inspection
methods were selected and assessed for identifying voids in preliminary test setup. The
sounding inspection method is further assessed for its effectiveness in identifying voids
in a full-scale, external tendon system. The results indicate that the sounding inspection
slightly underestimates the size of the voids. However, the inspected size and locations
of voids have a close correlation with actual voids in ducts. Thus, the sounding
inspection can be an effective tool for identifying voids because of its easy application in
the field.
Recently, the investigated failures of segmental post-tensioned (PT) bridges
called attention to the rehabilitation and mitigation methods of voided ducts in PT
structures. Although controversy exists on how to best protect PT tendons from
corrosion, filling these voids with grout may be one option. An optimized grouting procedure for repairing these voids is needed how best to protect the strands from
corrosive environments. This research investigates three grouting methods for
efficiently repairing the voids in PT duct systems. These methods are (1) vacuum
grouting (VG), (2) pressure grouting (PG), and (3) pressure-vacuum grouting (PVG).
Each method is being evaluated for filling capability, filling performance, and economic
feasibility. Also, three different pre-packaged grouts for repair are assessed in this
research to propose the most suitable material for repairing voided PT ducts. The results
indicate that the PG and PVG methods are more constructible and likely more
economical than the VG method. However, the PVG and VG methods seem to be more
effective than the PG method in filling the voids. As a result of these tests, the PVG
method is recommended for filling voids in tendons. The results also show that C-1 and
C-2 grouts have better filling capability than C-3 grout.
Although experimental tests using prototype specimens of external PT tendons
are performed to propose an effective repair grouting method and material, the
experimental conditions cannot cover all voids types, duct types, and other effects of
repair grouting methods in the field. Thus, the grout flow in voided ducts is predicted
using a commercial Computational Fluid Dynamics (CFD) program. The simulation of
the flow is challenging due to the complicated geometry of voided ducts, but the
simplified model in this research shows close correlations with experimental results.
Thus, various parameters of repair methods and materials are assessed in this research,
and the PVG method with grouts having low viscosity exhibited the best performance. If
it is determined that filling voids with grout is appropriate and prevents future corrosion,
it is recommended that voids in the field be filled using the PVG method with grouts
exhibiting low viscosities.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-12-7561 |
| Date | 2009 December 1900 |
| Creators | Im, Seok Been |
| Contributors | Hurlebaus, Stefan, Trejo, David |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | application/pdf |
Page generated in 0.0022 seconds