Date of Award
Doctor of Philosophy (PhD)
M. Z. Naser
Building contents include all the components that are not attached to the building which the owners place after the construction phase, such as furniture, electrical equipment, glassware, and other personal items. Loss and damage assessment of building contents proved to be challenging in performance-based earthquake engineering frameworks because of the data sparsity. Damages to building contents during an earthquake not only cause monetary losses; tumbling and over-toppling of heavy building contents could result in injuries and even deaths of occupants. While major advancements have been made in performance-based earthquake engineering; however, the focus is mainly on damages and collapse risk of the main structures (e.g. structural components and lateral force resisting system). Therefore, it is crucial to conduct research to improve current knowledge base of building content risks to property loss and life safety. Also, it is of a paramount importance to study and explore the various techniques to protecting these components in order to mitigate future loss and life hazards. Performance-based earthquake engineering principles are used to estimate content dollar loss and life safety. The FEMA P-58 (P58) framework is a component-based loss assessment framework that provides damage metrics for different building components in terms of fragility and consequence functions. However, P58 only has a limited number of content components where the consequence functions are left to users to define. Additionally, in terms of seismic casualty assessment, even when P58 is suitable for predicting the total number of fatalities and critical injuries, the current proposed P58 framework does not differentiate between different injury severity levels rendering it not as useful for applications such as estimating insurance premium for earthquake induced injuries. In order to overcome the shortcoming in terms of estimating content monetary losses and injury consequences. This work aims to provide a detailed framework for (1) assessing content damage, and monetary loss, (2) evaluating the influence of different content protection strategies on content risk and performance.
In the first study, this dissertation develops analytical fragility functions for rigid block-type contents based on nonlinear time history analysis of different dynamic models to represent building contents under two boundary conditions: freestanding and anchored; and two failure modes: sliding and overturning. A parametric equation is proposed to estimate content fragility parameters, covering a wide range of contents in commercial buildings. And it is easy to adopt in the P58 framework. Further, this dissertation studies the effectiveness of restrainers to reduce content dollar loss. As an illustrative example, the parametric equation for determining content fragility parameters is evaluated for its practical application by implementing it in a 4-story light wood frame office building to estimate content loss using two risk metrics: vulnerability function and Average Annual Loss (AAL). The content losses estimated using the parametric equation show good agreement with that computed using the analytical solution from non-linear time history analyses. A quantitative loss assessment is developed and used to estimate the losses for multiple mitigation scenarios by anchoring different content types such as heavy items, expensive items, electrical appliances, furniture, or glassware to investigate content risk mitigation. It is found that restraining expensive components was the optimal mitigation scenario, which resulted in a 74% reduction in AAL compared to freestanding contents. And decision-makers should design restrainers based on a combination of block-like content and restrainer characteristics and loss protection.
In the second study, a probabilistic injury model is proposed; the proposed model adopts the P58 framework for risk assessment and considers six injury severity levels (minor, moderate, serious, severe, critical, and fatal), following the Abbreviated Injury Scale (AIS). Two sources of injuries to occupants are considered: occupant-content impact and falling. The framework uses an occupant-time location model and a set of building content fragility curves. The framework evaluates the fatality and injury risk with five modules: seismic hazard analysis, structural analysis, building collapse simulation, damage assessment caused by building and content components, and injury severity assessment. The proposed model is implemented into two case studies of a 4-story office building: a reinforced concrete moment frame and a steel moment frame. It is found that the number of injuries depends on the intensity level of the earthquake where the frequency of injuries resulting in hospitalization can be up to 30 times more than that of the fatal injuries at intensity levels less than MCE level (Maximum Considered Earthquake, 50%/50year) and may amplify by 20 times at higher intensity shaking more than MCE level. Also, the minor, moderate, and serious injuries resulted from shifted freestanding contents are higher than the anchored content. On the other hand, anchoring components did not affect the severe, critical, and fatal injuries because building collapse will dominate.
The third study evaluates the influence of long duration ground motions on content losses. During the writing of this dissertation, research on long duration ground motions mainly focused on the impact of long duration on buildings' collapse performance. Only a scant body of knowledge exists on in the impact of earthquake duration on building non-collapse damage and, in particular, contents damage. Consequently, this dissertation studied the influence of long duration earthquakes on the seismic risk of steel moment frames with different heights (2- 4-, 8-, 12-, and 20-story). At first, a modified version of FEMA P-695 ground motion scaling tailored for seismic loss estimation purposes incorporating two sets of spectrally matched bi-directional short and long-duration ground motions is proposed. A set of 25 long-duration and 25 short-duration ground motions are selected and scaled using the proposed scaling approach. The results of incremental dynamic analysis (IDA) show the long duration ground motions have a significant impact on collapse risk — on average 28.0% . After that, a component-based loss estimation framework (for building and content losses) is used to predict seismic losses sustained by these buildings impacted by short- and long-duration ground motions. The result shows building height has limited influence on both building and content losses when subjected to either short or long-duration earthquakes. Seismic risk analysis reveals that earthquake duration has a significant influence on the collapse risk while it influence on building and content losses is less significant.
In summary, this dissertation fills the knowledge gap in predicting earthquake induced content losses and injuries. Also, it evaluates the effectiveness of anchoring contents in buildings to protect content from damage and protect occupants from content impact. The proposed models are flexible and easy to integrate into current building-specific seismic risk frameworks.
Majdalaweyh, Sereen, "Seismic Performance Assessment of Building Contents: Monetary Losses and Injuries" (2021). All Dissertations. 2923.