- Dingman Drive Bridge: Reinstatement of severed strands on prestressed concrete girders damaged by vehicle impact
- A.F. Turnbull ; W.F. Young ; C. Lam
- PCI Journal, Winter 2013, pages 45-54.
- Book Title / Journal:
- Year: 2013 , Volume: , Series:
- Repair and Retrofit of Structures
- Keywords: Bridges
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- In-situ health assessment of a poorly executed pre-stressed in-service concrete bridge and suggesting a rehabilitation strategy – A case study
- S.A. Rizwan ; F.A. Najam ; M.A. Qureshi
- Procedia Engineering, Vol. 54, pages 636-647
- Book Title / Journal:
- Year: 2013 , Volume: , Series:
- Repair and Retrofit of Structures
- Keywords: Bridges
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- Comparison of the Seismic Performance of Equivalent Straight and Curved Bridges due to Transverse Seismic Excitation
- E. Khan ; M.J. Kowalsky ; J.M. Nau
- Book Title / Journal: 15th World Conference on Earthquake Engineering
- Year: 2012 , Volume: , Series:
- Bridge management ; Bridges ; Earthquake engineering
- Keywords: Direct Displacement Based Design ; Bridges ; Transverse Seismic Design of Curved Bridge
- Description
- This study compares the transverse response of equivalent straight and curved bridges to investigate the hypothesis made by the AASHTO Guide Specification for LRFD Seismic Bridge Design that curved bridges may be analyzed as if they are straight, provided the bridge is regular. For this purpose curved bridges with subtended angles of 15, 30, 45, 60, 75, and 90 degrees, having the total arc length equal to the length of the equivalent straight bridge, are considered. Other parameters considered in this study are the number of spans
(two, four and six), and abutment restraints (9 different conditions). The equivalent straight bridges are designed using the Direct Displacement Based Design (DDBD) procedure including these parameters. The resulting designs are then analyzed with Inelastic Time History Analysis using both straight and curved geometry. Each bridge was subjected to 7 spectrum compatible time histories. Individual as well as average results are tabulated.
It is observed that deviation in the response of the curved bridge from the equivalent straight bridge increases as the subtended angles become larger and the number of spans reduces. It was also found that the type and degree of abutment restraint is a rather critical parameter in controlling the response of the bridge, the most significant being longitudinal abutment restraint which had a profound impact on results.
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- Investigation of the behaviour of small-scale bridge models using shake table tests
- Z. Chegini ; A. Palermo
- Book Title / Journal: New Zealand Society for Earthquake Engineering (NZSEE) Annual Technical Conference
- Year: 2014 , Volume: , Series:
- Earthquake engineering
- Keywords: shake table testing ; Bridges ; skew angle
- Description
- The skew angle of a bridge is an important boundary condition that affects its behaviour under seismic loading. Although some research has been carried out to identify these effects, such investigations for the most part remain analytical with a few instances including experimental testing. In an effort to understand the effects of skew on the seismic behaviour of bridges, a number of shake table tests have been performed on a skew and a non-skew bridge model and the results have been compared. These smallscale models are representative of two-bay short-span concrete bridges and consist of
precast deck and pier elements which have been assembled using threaded bars. The results of the tests show that although the amount of deck rotation is not higher in the skew deck, this rotation is non-symmetric and may lead to unseating of the deck. It is also discussed that the results of these tests can be used in the design of ‘controlled rocking’ connections in precast bridge structures.
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- Dynamic properties of an eleven-span motorway bridge at different levels of excitation
- G-W Chen ; S. Beskhyroun ; P. Omenzetter
- Book Title / Journal: New Zealand Society for Earthquake Engineering (NZSEE) Annual Technical Conference
- Year: 2014 , Volume: , Series:
- Bridge management ; Bridges ; Structural dynamics
- Keywords: Bridges ; dynamic properties
- Description
- Bridge dynamic properties measured under a given vibration intensity condition would give a true picture of the behaviour for that particular condition. However, the use of the model derived from such data may not be reliable when applied
for the prediction of response under a different vibration intensity condition. Therefore, it is necessary to investigate the structural dynamic behaviour at different levels of excitation in detail. This paper focuses on the experimental investigation of modal property variability at different levels of excitation. Both weak ambient vibration tests
(induced by nearby traffic, wind and possibly microtremors) and forced vibration tests
with different applied input force induced by eccentric mass shakers were performed on
the Nelson St off-ramp bridge (an 11-span post-tensioned concrete, box girder structure forming a part of the motorway network in Auckland’s CBD). Three separate system identification methods, namely peak-picking (PP), the frequency domain decomposition (FDD) and the data-driven stochastic subspace identification (SSI) method, were applied
for accurate structural modal parameter identification. It was found that the three output
only identification techniques are able to extract natural frequencies of the structure reliably, while the time domain SSI method yields the best mode shape estimates and PP may not be able to give accurate mode shape estimates for some modes. The variability of the dynamic properties for the 1st vertical and lateral bending modes was examined. A
general trend of decreasing natural frequencies and increasing damping ratios was observed with increased level of vibration intensity.
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