Building-specific seismic resilience assessment frameworks considering content sliding and injury

Posted 21 Mar 2017 by GovtEQC
Posted in EQC , EQR

Trevor Zhiqing Yeow (supervised by Greg MacRae) University of Canterbury (EQC funded project 14/U685)

A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy was accepted as a final report.

Non-Technical Abstract

Buildings should be designed to limit earthquake-related losses. One method to achieve this is to identify and encourage structural forms which are likely to have better performance and lower losses than others in order to improve resilience. This thesis develops and implements frameworks to (i) quantify the severity of content movement, (ii) predict injuries, and (iii) assessing earthquake-losses. The specific developments of the thesis were:

  1. Validating current sliding analytical models using experimental shake-table tests.

  2. Predicting the severity of content sliding.

  3. Development of an indoor building-specific injury prediction framework.

  4. Outlining a loss assessment framework for different structural forms.

The major findings were that:

  1. Existing sliding analytical models gave a reasonable indication of the experimental sliding shaking severity.

  2. A parametric equation for predicting the severity of content sliding, developed in this thesis, has better accuracy compared to existing methods.

  3. The outputs of the injury prediction framework developed in this thesis, which considers injuries caused by people falling and content movement, were consistent with actual injury data; indicating that the model’s outputs are reasonable.

  4. Application of loss assessment methodologies to a range of structural forms showed that stiffer buildings often have better overall performance compared to more flexible buildings in general.

Technical Abstract

To improve the seismic resiliency of a region, buildings should be designed to limit earthquake-related losses . Losses associated with damage/repair, death/injury, and downtime are often interlinked, as decreasing damage generally leads to a reduction in the number of injuries and duration of downtime. Recent shaking events, such as the 22 of February 2011 Canterbury earthquake, showed that some structural forms had better performance and lower losses than others. Therefore, identifying these structural forms and encouraging their use will improve regional seismic sustainability.

This thesis develops and implements frameworks to (i) quantify the severity of content movement, which was one of the main sources of injury in recent shaking events, (ii) predict injuries, and (iii) assess structural damage and injury losses to aid in decision-making. These methodologies were used to evaluate scenario and probabilistic losses considering both injury and direct-damage repairs. Specific developments include:

  1. Validating current sliding analytical approaches using experimental shake-table testing of generic office-type building contents (i.e. desks, drawers) on realistic flooring materials.

  2. Predicting the extent of content sliding which is applicable to a wide range of structural forms.

  3. Development of an indoor building-specific injury prediction framework.

  4. Outlining of the loss assessment framework for different structural forms considering damage repair-related losses, contents movement, and injuries.

It was found from the shake-table tests that the content’s response was reasonably well approximated by Amonton’s and Coulomb’s friction laws on average. Simple analytical models based on these laws therefore give a reasonable indication of the experimental sliding shaking severity.

A parametric equation was developed for predicting the maximum sliding displacement of contents. This was applied to an analytical case study of buildings of varying height, strength, stiffness, and structural system; where this equation was found to have superior efficiency and sufficiency compared to existing methods.

A mechanics-based injury prediction framework was developed to considering people falling and content movement, which were the two main sources of indoor injuries during the 22 February 2011 Canterbury earthquake event. This model also considers the posture and location of occupants, as well as the varying severity and associated-cost of injuries. Findings from a case study of injuries within a 10-storey building using this framework were consistent with actual injury data; indicating that the model’s outputs are reasonable. The framework was also used in a cost-benefit study of fixing contents prone to moving during earthquakes; where the expected annual benefits was equal to the increase in implementation costs, indicating that this mitigation approach is economically justifiable.

Application of existing damage-repair cost assessment methodologies, content sliding analytical models, and the injury prediction framework, to a range of structural forms showed that stiffer buildings often have the best performance overall despite experiencing higher acceleration response. This was due to (i) decreased interstorey drift response, (ii) a lower probability of requiring full-replacement or collapsing, and (iii) lower damage to non-brittle acceleration-sensitive building components due to the importance of frequency/velocity. This shows that stiffer buildings are likely to have better overall performance compared to more flexible buildings in general.

 

Issue date: 
01 March 2017
Category: 
Engineering
Paper number: 
402
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