1. Statement of Problem
1.1 The Need for Safer Design of Nonstructural Components and Contents
The Canterbury Earthquake Sequence of 2010 to 2011 caused billions of dollars’ worth of damage to the buildings of Christchurch and surrounding towns. However, a significant portion of the dollar and downtime losses incurred, contributing over 80-90% of a buildings value in most cases, can be attributed to the losses from damages to nonstructural components and contents.
|Damage to ceiling systems
||Damage to walls and linings
|Damage to window panels
||Damage to office components
Fig1. Nonstructural damage to components and contents (Dhakal 2010)
Earthquake damage to nonstructural components and contents poses direct and indirect threat to safety of people as well as loss of critical function and economy. However, until recently, the importance of nonstructural damage has not been appropriately investigated, and the engineering solutions required to prevent this type of damage has not been provided. In this context, a focused research is required to:
- Better understand the performance of nonstructural components and contents
- Quantify the extent of nonstructural damage expected after an earthquake event and attributed losses
- Prepare safe design methodologies and installation procedures
1.2 Challenges and Issues
The final aim is to fully understand the scale of the problem in respect to deaths, dollars and downtime (3Ds). Currently, the risk exposure related to nonstructural damage is only poorly understood amongst territorial authorities, property owners, commercial tenants, engineers and contractors. Quantifying the risk will allow prioritization of investment and technical solutions.
1.3 The Quake Centre’s Initiative
It is important that the Quake Centre focuses its attention on providing the best outcome for its investment partners and New Zealand. Given the important role of nonstructural components and contents in building performance, and in particular the economic imperative, the Quake Centre has chosen the seismic performance of nonstructural components and contents as a key strategic area for development. As part of this initiative, two areas are selected to be focused: • Seismic loss assessment of nonstructural components and contents • Investigation of seismic response of nonstructural walls This research addresses the former topic.
2. Investigation Methodology
2.1 Performance-Based Earthquake Engineering Methodology
The methodology considered in this research is based on the Pacific Earthquake Engineering Research Center’s (PEER’s) framework for Performance-Based Earthquake Engineering (PBEE) methodology. Elements of the process include seismic hazard analysis, structural analysis resulting in quantification of engineering demands, damage analysis and identification of damage to building components and contents, and loss analysis. This methodology is underpinned by a consistent probabilistic framework which can implicitly represent the inherent uncertainties exists in the performance assessment process.
Fig2. Underlying probabilistic framework for loss analysis (Moehle 2004)
2.2 Archetype Buildings
This research examines a set of archetype building structures comprising of reinforced concrete moment frame structures, reinforced concrete shear wall structures, steel moment resisting frame structures, steel braced frame structures, and base-isolated structures. The intention is to consider a wide range of New Zealand modern code-conforming building structures, and investigate and compare the performance of nonstructural elements within these buildings. The economic analysis of seismic loss associated with these archetype representations will provide a comprehensive understanding of risk exposures related to the nonstructural damage within New Zealand building stock. The outcomes can be then presented to territorial authorities, property owners, commercial tenants, engineers and contractors to facilitate design decision making.
2.3 Seismic Loss Assessment Tool (SLAT)
SLAT, a computation tool developed by Associate Prof. Brendon Bradley of the University of Canterbury will be utilized in the performance and loss assessment process intended. Based on the PBEE, SLAT has been adopted by several research groups in New Zealand and overseas to perform case-studies to understand the economic losses in seismic event in relation to damage and downtime. SLAT is currently limited by the lack of a graphical user interface (GUI) to provide simplicity in use for the uninitiated. A GUI will be developed to allow broad uptake of the tool. It is envisaged that the source-code for the ‘engine’ of SLAT will remain open-source (as this allows researchers to continue to contribute to it), but that there will be a small cost for licencing of the GUI in order to provide funding for its continued development. The SLAT is seen as a major contributor both nationally and internationally to the development of all aspects the seismic response of nonstructural elements.
3. Project Outputs and Deliverables
Major benefits from conducting this research are:
- Quantification of the risk associated with poor building fit-out within the New Zealand building stock
- Development of an enhanced bases for decision making in regards to whether further efforts to be considered for improving performance of nonstructural components and contents
- Provision of an assessment tool for consultants to make improved design and retrofit decisions
- Development of a robust framework to investigate how significantly the overall system performance can be improved by using low-damage solutions for walls and ceiling
4. Project Timeline
The following timelines indicate feasible timelines for the initial phases of the SLAT and Walls and Ceilings projects
July 2015 - Engagement of research engineer
October 2015 - Engagement of software engineer
October 2015 - Engagement of engineering steering group
March 2016 - Beta testing of SLAT GUI
July 2016 - Launching SLAT live
March 2016, Oct. 2016 - Presentation of results associated with concrete structures
Dec 2016, June 2017 - Presentation of results associated with steel structures
Dec. 2017 - Presentation of results associated with base-isolated structures
The project team wishes to acknowledge the financial support provided by the Quake Centre partners and the great technical support provided by Associate Professor B. Bradley (University of Canterbury) and Professor K. Elwood (University of Auckland) enabling the project to proceed.