Influence of reinforcing steel fracture on seismic performance of concrete structures : fracture simulation, earthquake duration effects, and design strategies
- Low-cycle fatigue and fracture of longitudinal reinforcing steel is a critical potential failure mode in concrete structures subjected to earthquake ground motions. Design to resist fracture depends on the reinforcing steel materials, the design details of the reinforced concrete members, and the cyclic deformation and strain demands imposed by the earthquake. Recently, concerns related to reinforcing bar fatigue and fracture have arisen due to two developments. One is the interest by the engineering and construction industry to utilize high-strength reinforcing steel materials in structures designed for regions with high seismic hazard. Since high-strength reinforcing bars tend to be less ductile and more prone to low-cycle fatigue, as compared to conventional Grade 60 bars, their adequacy for use in structures in high seismic regions needs to be confirmed. The second is related to concerns about long duration ground motions, which can increase the cyclic loading demands on steel reinforcement. Since current design methods do not explicitly consider the influences of ground motion duration, questions have been raised as to whether current seismic design requirements are adequate for structure in regions that may be affected by large magnitude earthquakes or geologic basin effects, which can lead to ground motion duration that are longer than considered in conventional designs. In the prevailing structural design and assessment methods, fatigue and fracture are only implicitly considered by checks of peak deformation measures (e.g., peak strain demand) or other proxy measures (e.g., cumulative plastic demand), which are not sufficient to resolve behavioral effects associated with material cyclic toughness and duration effects under random cyclic loading. This study (1) develops a reliable analytical framework and supporting computational tools for simulating fatigue and fracture in steel reinforcement, considering the steel material properties, reinforcing bar details in concrete structures, and random ground motion loading; (2) applies these methods to evaluate seismic design requirements for high-strength reinforcing bars, specifically Grade 80 and Grade 100 bars; (3) develops an analytical framework and algorithms for using nonlinear dynamic analysis results to systematically evaluate earthquake duration and ground motion spectral shape effects on structures; and (4) applies these methods to incorporate earthquake duration effects in the design of reinforced concrete bridge piers.
|Type of resource
|electronic resource; remote; computer; online resource
|1 online resource.
|Degree committee member
|Degree committee member
|Stanford University, Civil & Environmental Engineering Department
|Statement of responsibility
|Submitted to the Civil & Environmental Engineering Department.
|Thesis Ph.D. Stanford University 2020.
- © 2020 by Kuanshi Zhong
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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