Abstract
Tunnels, culverts, and subway stations are the main parts of an integrated infrastructure system. Most of them are constructed by the cut-and-cover method at shallow depths (mainly lower than 30 m) of soil deposits, where large-scale seismic ground deformation can occur with lower stiffness and strength of the soil. Therefore, the transverse racking deformation (one of the major seismic ground deformation) due to soil shear deformations should be included in the seismic design of underground structures using cost- and time-efficient methods that can achieve robustness of design and are easily understood by engineers. This paper aims to develop a simplified but comprehensive approach relating to vulnerability assessment in the form of fragility curves on a shallow two-story reinforced concrete underground box structure constructed in a highly-weathered soil. In addition, a comparison of the results of earthquakes per peak ground acceleration (PGA) is conducted to determine the effective and appropriate number for cost- and time-benefit analysis. The ground response acceleration method for buried structures (GRAMBS) is used to analyze the behavior of the structure subjected to transverse seismic loading under quasi-static conditions. Furthermore, the damage states that indicate the exceedance level of the structural strength capacity are described by the results of nonlinear static analyses (or so-called pushover analyses). The Latin hypercube sampling technique is employed to consider the uncertainties associated with the material properties and concrete cover owing to the variation in construction conditions. Finally, a large number of artificial ground shakings satisfying the design spectrum are generated in order to develop the seismic fragility curves based on the defined damage states. It is worth noting that the number of ground motions per PGA, which is equal to or larger than 20, is a reasonable value to perform a structural analysis that produces satisfactory fragility curves.
Highlights
In previous design specifications for underground structures in Japan, the seismic design is not usually considered in the transverse direction because there has been a strong belief that underground structures are stable following the deformation of the surrounding soil during an earthquake
This study examines the fragility curves of a shallow two-story reinforced concrete underground box structure subjected to seismic loading
A total of 1150 artificial ground motions in 23 peak ground acceleration (PGA) ranging from 0.02 g to 1.3 g were applied to a two-dimensional plane strain finite element method (FEM) model
Summary
In previous design specifications for underground structures in Japan, the seismic design is not usually considered in the transverse direction because there has been a strong belief that underground structures are stable following the deformation of the surrounding soil during an earthquake. Sci. 2017, 7, 735 the design did not consider the earthquake load [1] were hit by the Hyogoken-Nanbu earthquake of magnitude 7.2 based on Japan Meteorological Agency scale (roughly equivalent to a moment magnitude Mw of 6.9) in 1995 [2]. The general damage pattern showed the lack of load carrying capacity against shear at the center columns that led to the collapse of the tunnel ceiling slabs [1,3]. Many of infrastructures worldwide have experienced significant damages in recent earthquakes such as in the Mw 7.7 Chi-Chi Taiwan in 1999 [4], Mw 6.3 Baladeh in 2004 [5], and
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
