Low Damage Seismic Design Technologies for Precast Concrete Bridges

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Low Damage Seismic Design Technologies for Precast Concrete Bridges

 

Submitted by:  University of Canterbury

Owner:  University of Canterbury

 

Summary:

The traditional monolithic construction of bridges has been common among many bridge practitioners in New Zealand. During the Canterbury earthquakes, many of the monolithic bridges around Christchurch performed structurally well, but some critical bridges on the city’s arterial routes lost their functionality and were closed. The bridge repair works caused major traffic disruptions around the city.

The current societal needs require advancing the bridge practice, adding novel construction technologies, and enhancing seismic performance of the bridges. Research carried out at the University of Canterbury aimed to develop technologies for prefabricated bridges which offer the following advantages compared to monolithic construction:

  1. Faster project delivery
  2. Limited traffic disruption  
  3. Reduced weight  
  4. Formwork cost savings  
  5. Higher accuracy in construction of elements 
  6. Better quality control  
  7. Lower machinery and equipment costs  
  8. Improved safety during construction
  9. Immediate functionality of a bridge after an earthquake
  10. Minimal residual displacement in the bridge following the earthquake
  11. Minimal to no post-earthquake repairs of the bridge
  12. Higher durability of the bridge elements
  13. Less environmental impacts and Carbon footprints

A half-scale fully precast multi-column bridge pier (bent) specimen was developed. The specimen was based on a typical highway bridge in New Zealand with 16 m span. The specimen was the largest of its kind ever tested in the Southern Hemisphere. The specimen weighed over 22 tons and was loaded with an additional 40 tons to simulate gravity loads. The specimen was prefabricated at the Bradfords Precast Ltd. in Ashburton. After assembly, the bent was tested under quasi-static cyclic loading. The bent incorporated Dissipative Controlled Rocking (DCR) connections between the precast elements. The DCR connections are also called PRESSS Hybrid. In a DCR connection, unbonded post-tensioned tendons provide self-centering while the external dissipaters absorb seismic energy. During a seismic event, the structure starts rocking at the detailed connections.