2013 Session: 499

• Seismic Retrofit and Ductility Enhancement of Thin-Walled Steel Tubular Bridge Piers
  Abstract: This paper deals with the seismic retrofit and ductility enhancement of thin-walled steel tubular bridge piers. The basic characteristics of the thin-walled steel tubular bridge piers are noted and the importance of various retrofit techniques in improving strength and ductility capacity of such structures is explained. A seismic design method for ultimate strength and ductility evaluation of the new and retrofitted, thin-walled, steel tubular bridge pier is presented. The application of the method is demonstrated by comparing the computed strength and ductility of some bridge piers with test results. The method is applicable for both the design of new and retrofitting of existing thin-walled steel tubular bridge piers. The effects of some important parameters such as width-to-thickness ratio, column slenderness ratio, height of infill concrete, residual stress, arrangement of additional longitudinal stiffeners and inclusion of energy absorption segment on the ultimate strength and ductility of thin-walled steel tubular bridge piers are presented and discussed.
  Authors: Mamaghani, Iraj H. P.
  Authors: Mamaghani, Iraj H. P.
  Year: 2013
  Document Type: Paper
  Subject: Bridges and Other Structures; Design
  Session: 499
  Paper Number: 13-1304
• Seismic Retrofit of San Francisco BART Aerial Stations
  Abstract: Considering the high risk of earthquakes in the San Francisco Bay Area and the essential role of the Bay Area Rapid Transit (BART) system in the region, the BART Earthquake Safety Program (ESP) has attracted great public attention from the beginning. This paper covers the seismic evaluation and retrofit of a total of eleven aerial stations within the BART System. All eleven stations are being retrofitted to meet Safety Performance requirements; and three stations have been additionally retrofitted to meet Operability Performance requirements. The details of the analysis approaches, seismic vulnerability of as-built stations, and retrofit measures proposed for the BART retrofit effort are presented in this paper. It was found that existing bent cap beams and footing caps are insufficient to resist the overstrength demands from the columns. Joints between columns and bent caps and joints between columns and footings are required to be strengthened as well. By various retrofit measures, including bent cap bolsters, in-fill walls, column FRP wrapping, footing partial overlays, and footing enlargements, the stations can be upgraded to achieve Safety and Operability Performance requirements.
  Authors: Wang, Huanzi; Ng, Shirley; Abdel-Karim, Ahmad M; Weston, Dan
  Authors: Wang, Huanzi; Ng, Shirley; Abdel-Karim, Ahmad M; Weston, Dan
  Year: 2013
  Document Type: Paper
  Subject: Bridges and Other Structures; Design
  Session: 499
  Paper Number: 13-0566
  Practice-Ready: Yes
• Performance of Bridge Superstructure Restrainer Systems Under Multihazard Effects
  Abstract: Superstructure unseating was judged as one of the major causes of bridge collapse during the 1971San Fernando earthquake, by the California Department of Transportation (Caltrans). Similarsuperstructure unseating has been observed subsequent to the 2005 Hurricane Katrina, the 2004Indian Ocean tsunami and the 2011 Japanese earthquake and tsunami. Bridge decks submergedduring the later events experienced substantial superstructure damage due to hydrodynamic upliftforces due to wave action and hydrostatic uplift forces due to buoyancy coupled with entrapped airbelow the bridge deck. These events have tested deck to pier restrainer systems.In this paper, the performance of some traditional restrainer systems is assessed through thereview of bridge reconnaissance work done subsequent to; (1) hurricane Katrina 2005, (2) Chileearthquake 2010, (3) Japanese earthquake and tsunami 2011, and (4) Indian Ocean earthquake andtsunami 2004. The objective of this paper is to point out weaknesses of traditional restrainersystems and provide some recommendations to improve these systems based on successfulrestrainer applications.The assessment indicate that properly designed shear keys as restrainer systems againsthorizontal effects due to hurricane induced storm surges and earthquake ground motions are fairlyeffective for that purpose. Restrainer systems for vertical effects due to storm surges and tsunamiinduced forces appear to be less successful due to various reasons including failure of anchor boltsconnecting restrainers to the structure. The author further recommends a more robust approach tosolving the problem of superstructure unseating.
  Authors: Charles, Winsbert C.
  Authors: Charles, Winsbert C.
  Year: 2013
  Document Type: Paper
  Subject: Bridges and Other Structures; Design
  Session: 499
  Paper Number: 13-5382
• Performance of Bridge Superstructure Restrainer Systems Under Multihazard Effects
  Authors: Charles, Winsbert
  Authors: Charles, Winsbert
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Bridges and Other Structures; Design
  Session: 499
  Paper Number: 13-5382
• Seismic Retrofit of San Francisco BART Aerial Stations
  Authors: Wang, Huanzi
  Authors: Wang, Huanzi
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Bridges and Other Structures; Design
  Session: 499
  Paper Number: 13-0566
• Integral Bent Cap for Continuous Precast Prestressed Girder Bridges
  Abstract:

  Ductile behavior of bridge systems is desirable under earthquake loadings. The ductility of precast prestressed girder bridges can be achieved by proper detailing of intermediate pier diaphragm through extended strands, column bars, and joint reinforcement. Extended strands at intermediate crossbeams are used to connect the ends of girders with diaphragms and resist loads from creep effects, shrinkage effects, and seismic positive moments. The objective of extending the strands is to ensure that the tensile force carried by the strand can be transferred to the opposite side of the diaphragm. The use of ASTM A706 Grade 80 reinforcing steel with this higher capacity can provide benefits to concrete bridge construction by reducing member cross sections and reinforcement quantities. The use of high-strength steel reinforcement with high-strength concrete should result in more efficient use of both materials. This paper provides guidance for the design of fixed pier connections of continuous prestressed girder bridges extended strands at fixed pier connections of continuous prestressed girder superstructures.

  Authors: Khaleghi, Bijan
  Authors: Khaleghi, Bijan
  Year: 2013
  Document Type: Paper
  Subject: Bridges and Other Structures; Design
  Session: 499
  Paper Number: 13-1723
  Practice-Ready: Yes