Ductile Detailing of Walls

 

Reinforced concrete (RC) ductile walls are commonly used to resist lateral-loads in multi-storey construction.

 

The Problem

The series of earthquakes hitting the Canterbury region between 2010 and 2011 resulted in unexpected failure of several reinforced concrete (RC) walls. Following the earthquakes, SESOC and CERC recommended several changes that will soon be published as a third amendment to the New Zealand Concrete Structures Standard NZS 3101:2006. These have had insufficient literature and experimental validation. Examples of wall damage and failures:

 

 

The Objective

To further develop and validate the improved detailing provisions in NZS3101 for RC ductile walls. The objective can further be broken down into the following deliverables:

1. A database of tests performed on RC walls around the world

2. Identify the typical New Zealand design and construction practice used in walls

3. Use database to test the hypotheses put out by the SESOC and CERC recommendations

4. Gaps in knowledge identified by mapping the demands and detailing of NZ practice with tests in the database.

5. Develop and conduct a test programme to address the gaps

6. A set of recommendations to be proposed as amendments to NZS3101:2006.

 

The Outcome

The outcome will consist of improved wall provisions proposed as amendments to NZS3101:2006 to be used by engineers in New Zealand. The provisions will comprise wall detailing specification to enable RC walls to reach their full design ductility through wide spread of plasticity and good energy dissipation characteristics. Walls complying with these provisions will have predictable and repairable damage allowing restored building functionality.

 

As this topic is of international interest, the findings from this project can be shared to be incorporated into standards used by countries such as the United States, Japan and Chile.

 

Wall Database

A database has been developed at the University of Auckland that includes rectangular RC walls tested under uni-axial, pseudo-static conditions. The table and graphs below summarise the scope of the database and the coverage across a range of test parameters. 

 

Database Summary

Number of Specimens144
Number of test programmes26
Number of descriptive parameters124

 

Parameter Summaries from Wall Database

 

Validation of NZS3101:2006

Recommendations proposed by SESOC and CERC to be included in NZS3101:2006 Amendment 3 have been investigated using the database. The results are shown below.

 

 

 

Planned Testing

6-10 large-scale wall tests will be constructed and tested at the University of Auckland in quasi-static, reverse cyclic protocols. The testing program will likely be split up into two testing phases. The specimen detailing and geometry will be representative of a wall in a typical multi-storey building located in Wellington. The test setup is presented below.

 

 

The tests will investigate a selected parameters from the list below. These tests will aim to fill the gaps in knowledge in RC wall design as well as address some of the uncertainties and challenges faced in the industry.

  • Length of confinement
    • Vertically
    • Horizontally
  • Test performance difference between:
    • Ductile
    • Limited ductile
  • Effect of lap splices in the plastic hinge
    • Fully spliced
    • Staggered splice
    • Continuous (no splice)
  • Cross-sectional shape
    • Thinner web, enlarged boundary elements
    • Rectangular
    • C-shape, I-shape
  • Axial load
  • Exploring innovative concepts
    • Steel encased wall base

 

 

Timeline

Nov 2015 - Test Design First Phase Complete 

Dec 2015 - Specimen Construction Complete

Jan 2016 - Testing begins 

Mar 2016 - Testing of First Phase Complete

Apr 2016 - Testing of Second Phase begins

Aug 2016 - Testing of Second Phase Complete 

Nov 2016 - Recommendations proposed

 

Acknowledgements

The project team wishes to acknowledge the financial support provided the Quake Centre partners and the MBIE Building Performance Branch for enabling the project to proceed.

   

 

 

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Last updated: 24/09/15
 

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