A carregar...
Publicação
Optimisation and design of post-tensioning anchorage corner blisters in concrete box girder bidges
| Nome: | Descrição: | Tamanho: | Formato: | |
|---|---|---|---|---|
| 23.9 MB | Adobe PDF |
Autores
Orientador(es)
Resumo(s)
The design of anchorage blisters of internal continuity post-tensioning tendons of bridges
built by the cantilever method, presents some peculiarities, not only because they are
intermediate anchorages but also because these anchorages are located in blisters, so the
prestressing force has to be transferred from the blister the bottom slab and web of the
girder.
The high density of steel reinforcement in anchorage blisters is the most common reason
for problems with concrete cast in situ, resulting in zones with low concrete compacity,
leading to concrete crushing failures under the anchor plates. A solution may involve
improving the concrete compression and tensile strength.
To meet these requirements a high-performance fibre reinforced self-compacting mix-
ture (HPFRC) was used in anchorage corner blisters of post-tensioning tendons, reducing
the concrete cross-section and decreasing the reinforcement needed.
To assess the ultimate capacity and the adequate serviceability of the local anchorage
zone after reducing the minimum concrete cross-section and the confining reinforcement,
specified by the anchorage device supplier for the particular tendon, load transfer tests
were performed.
To investigate the behaviour of anchorage blisters regarding the transmission of stresses
to the web and the bottom slab of the girder, and the feasibility of using high performance
concrete only in the blister, two half scale models of the inferior corner of a box girder
existing bridge were studied: a reference specimen of ordinary reinforced concrete and a
HPFRC blister specimen. The design of the reinforcement was based in the tensile forces
obtained on strut-and-tie models.
An experimental program was carried out to assess the models used in design and to
study the feasibility of using high performance concrete only in the blister, either with
casting in situ, or with precast solutions.
A non-linear finite element analysis of the tested specimens was also performed and
the results compared.
Descrição
Palavras-chave
Post-tensioning Anchorage zones High-performance concrete Self-compacting concrete Box girder bridge Steel fibres