Operationalizing a seismic resilience index for road segments: The case of a road network in Surigao City, Surigao del Norte

• Main Author: Fernandez, Cris Angelo Chua
• Format: text
• Language: English
• Published: Animo Repository 2023
• Subjects: Roads—Earthquake effects—Philippines—Surigao City; Roads—Design and construction—Safety measures; Earthquake resistant design; Civil Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etdm_civ/30; https://animorepository.dlsu.edu.ph/context/etdm_civ/article/1032/viewcontent/Operationalizing2_a_Seismic_Resilience_Index_for_Road_Segments__Th_Redacted.pdf
• Institution: De La Salle University

Vital roads need to be operational most of the time due to its role in providing important access to goods and services, especially during emergencies. In the occurrence of a damaging seismic event, access to roads become more critical due to the need to provide medical and emergency services. Therefore, it is important for roads to be operational and fully restored as quick as possible if rendered inoperable. In view of this, a framework for road segments is proposed, operationalized, and applied to a road network in Surigao City, Surigao del Norte. There is a research gap in the seismic resilience assessment of roads in the country. As such the study fills this gap specifically for pre and post evaluation of road performance after an earthquake. Furthermore, inclusion of network redundancy is included in the study as a step to incorporate road network redundancy in a seismic resilience index. The developed framework for seismic resilience index evaluation considers three properties of resilience: Robustness, Rapidity, and Resourcefulness. Robustness is included by assessing the performance of the road segments by considering loss of functionality and performance impairment due to debris distribution of interfering to the road segments. It is assessed by comparing the load parameter which is the seismic hazard, and the capacity parameter through the developed acceleration threshold equation. Rapidity is considered in the framework by proposing an optimal restoration strategy that determines the minimum volume of debris to regain the functionality of road segments that are rendered inoperable and applying it in the resilience analysis. Resourcefulness is incorporated together with rapidity to generate the rate of debris clearing operations until road is functional for medical emergency response and full road restoration. The seismic hazard of the study is quantified through a Probabilistic Seismic Hazard Analysis (PSHA). The results of PSHA show that the peak ground acceleration (PGA) under a Maximum Considered Earthquake (MCE) Scenario (2% probability of exceedance in 50 years) is 0.55g. Furthermore, a Uniform Hazard Response Spectrum (UHRS) is generated that was subsequently used to simulate artificial earthquakes in SeismoArtif. The performance of the roads is evaluated using an acceleration threshold as a proposed road capacity parameter. This parameter focuses on the performance of roads with respect to the debris distribution of interfering buildings. The proposed acceleration threshold resulted in three cases (Case 1, Case 2, and Case 3). The acceleration threshold and the PGA from PSHA determines the road condition after the MCE. With this, an optimal restoration strategy is also proposed to maximize the debris clearing operations. From the acceleration threshold measure, PGA, and the optimal restoration strategy, resilience curves for all the roads in the study area are generated. The resilience curves are used to calculate the seismic resilience index of each road segment. The resilience indices are analyzed per road case based on acceleration threshold. Based on the investigation, qualitative descriptions among the three cases were provided. Case 1 roads are described as “Possible Road Closure” with resiliency varies on the performance of the considered parameters. Case 2 roads are described as “Continuously Operational” and is the ideal case for roads to have. Finally, Case 3 roads are described as “Not Fit for Emergency Response.” It is also proved in the study that for roads to be considered “resilient,” the resilience index must be greater than 0.5. Redundancy analysis is also performed in the study. One of the parameters in evaluating the redundancy of the nodes in the road network is the probability of relative isolation (PORI). Furthermore, conditional probability by situationally removing paths from analyzed node to source node is analyzed to determine the redundancy index. A node redundancy index map is provided.