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Precast concrete shear walls with unbonded post-tensioning, which resist seismic loads have attracted the attention of researchers over the past 20 years. This study provides a database of a special subset of precast concrete shear walls tested under monotonic or cyclic loading: rocking walls, hybrid walls, and walls with end columns. These shear walls experience joint opening, undergo rocking motion over the foundation, and utilize unbonded post-tensioning to self-center after load removal. Seismic energy is dissipated in distinct ways that vary from nonlinearity of concrete and post-tensioning strands (rocking walls) to yielding of mild steel reinforcement or external energy dissipaters (hybrid walls and walls with end columns). The experimental drift capacity, strength, and damage sequence of walls from the literature were compiled. Onsets of cover concrete spalling, yielding of energy dissipaters, yielding of post-tensioning strands, fracture of energy dissipaters, and crushing of confined concrete were reported. ACI guidance on shear walls were evaluated by comparing the lateral drift and strength measured by testing and predicted by ACI.
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Full-scale testing of precast tunnel lining segments under thrust jack loading: Design limits and ultimate response
In modern practice, precast segmental tunnel linings are typically installed via a tunnel boring machine (TBM), which advances by thrusting against the previously installed segmental ring. The forces applied through the thrust jack pads can induce significant bursting and spalling tensile stresses and strains in the segment, and improperly designed segments can suffer from cracking as a result. An experimental study has been conducted to evaluate the progression of damage from initial cracking to ultimate capacity for full-scale precast tunnel liner segments under thrust jack loading. The baseline segment design is composed of steel fiber reinforced concrete (SFRC), and the impact of supplemental conventional steel bar reinforcement and load application eccentricity were also investigated. Six full-scale tests were performed with a thrust jack load per pad up to 22.2 MN (which is ~3.8 times the maximum expected installation thrust force). At the maximum expected thrust jack load during installation (5.78 MN per pad), the segments were virtually undamaged, and hairline cracking initiated between the load pads on only one test. At the TBM’s ultimate jacking capacity (9.55 MN per pad) surface cracking was observed between and under the load pads; however, the crack width remained below 0.2 mm for all specimens. The formation of cracking limit states was accurately predicted by pre-test linear and nonlinear finite element (FE) models. At overload conditions, the baseline SFRC-only segment exhibited a radial bursting failure. The inclusion of supplemental conventional reinforcement does not reduce the level of cracking damage or strain development below the TBM’s ultimate jacking capacity; however, at overload conditions, the supplemental reinforcement mitigates cracking and prevents a radial bursting failure at 20.3 MN per pad. A load eccentricity of 38 mm towards the extrados surface increased the transverse strain and the formation of transverse cracking at a lower load level.
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- Award ID(s):
- 1950487
- PAR ID:
- 10481225
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Tunnelling and Underground Space Technology
- Volume:
- 142
- Issue:
- C
- ISSN:
- 0886-7798
- Page Range / eLocation ID:
- 105446
- Subject(s) / Keyword(s):
- precast segmental tunnel liner thrust jacking load tunnel boring machine steel fiber reinforced concrete tensile cracking limit states finite element modeling
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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null (Ed.)Precast concrete shear walls with unbonded post-tensioning, which resist seismic loads have attracted the attention of researchers over the past 20 years. This study provides a database of a special subset of precast concrete shear walls tested under monotonic or cyclic loading: rocking walls, hybrid walls, and walls with end columns. These shear walls experience joint opening, undergo rocking motion over the foundation, and utilize unbonded post-tensioning to self-center after load removal. Seismic energy is dissipated in distinct ways that vary from nonlinearity of concrete and post-tensioning strands (rocking walls) to yielding of mild steel reinforcement or external energy dissipaters (hybrid walls and walls with end columns). The experimental drift capacity, strength, and damage sequence of walls from the literature were compiled. Onsets of cover concrete spalling, yielding of energy dissipaters, yielding of post-tensioning strands, fracture of energy dissipaters, and crushing of confined concrete were reported. ACI guidance on shear walls were evaluated by comparing the lateral drift and strength measured by testing and predicted by ACI.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.tust.2023.105446
