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Impact of directivity on seismic risk assessment: rupture distance, component and propagation length

Authors:
Leanda J. Payyappilly at Indian Institute of Technology Hyderabad
Leanda J. Payyappilly
K. S. K. Karthik Reddy at VIT University
K. S. K. Karthik Reddy
Surendra Nadh Somala at Indian Institute of Technology Hyderabad
Surendra Nadh Somala
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Abstract and Figures

Near-field effects like directivity pulses are known to cause severe damage to particular kinds of infrastructure but most studies have limited themselves to the level of structural response and fragility computations. In this study, state-of-the-art tools are used from the Natural Hazards Engineering Research Infrastructure to estimate normalized economic losses and injuries, by considering one particular building type and occupancy category listed in HAZUS-MH. One non-directivity scenario, and three directivity scenarios with different levels of one sided propagation are simulated using dynamic rupture modeling by shifting the hypocenter from the center of the fault towards one side by different amounts for each directivity scenario. Furthermore, multiple five station networks at fixed offsets (rupture distances) from the fault are used to establish the influence of distance away from the fault on the economic losses. Both fault parallel and fault normal components of ground motion are simulated using a spectral finite element software SPECFEM3D. The engineering demand parameter computed in terms of peak inter-storey drift is used with 2000 realizations for a three-, six- and nine-storey commercial steel moment frames to estimate the percentage of economic losses normalized in terms of repair cost and injuries normalized in terms of population. The inclusion of complex phenomena like directivity to evaluate economic losses and risk will contribute to potential reassessment of risk mitigation policies by the United Nations Office for Disaster Risk Reduction (UNDRR).
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Vol.:(0123456789)
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Asian Journal of Civil Engineering (2021) 22:1361–1375
https://doi.org/10.1007/s42107-021-00388-7
ORIGINAL PAPER
Impact ofdirectivity onseismic risk assessment: rupture distance,
component andpropagation length
LeandaJ.Payyappilly1· K.S.K.KarthikReddy1 · SurendraNadhSomala1
Received: 30 April 2021 / Accepted: 11 August 2021 / Published online: 21 August 2021
© The Author(s), under exclusive licence to Springer Nature Switzerland AG 2021
Abstract
Near-field effects like directivity pulses are known to cause severe damage to particular kinds of infrastructure but most
studies have limited themselves to the level of structural response and fragility computations. In this study, state-of-the-art
tools are used from the Natural Hazards Engineering Research Infrastructure to estimate normalized economic losses and
injuries, by considering one particular building type and occupancy category listed in HAZUS-MH. One non-directivity
scenario, and three directivity scenarios with different levels of one sided propagation are simulated using dynamic rupture
modeling by shifting the hypocenter from the center of the fault towards one side by different amounts for each directivity
scenario. Furthermore, multiple five station networks at fixed offsets (rupture distances) from the fault are used to establish the
influence of distance away from the fault on the economic losses. Both fault parallel and fault normal components of ground
motion are simulated using a spectral finite element software SPECFEM3D. The engineering demand parameter computed
in terms of peak inter-storey drift is used with 2000 realizations for a three-, six- and nine-storey commercial steel moment
frames to estimate the percentage of economic losses normalized in terms of repair cost and injuries normalized in terms
of population. The inclusion of complex phenomena like directivity to evaluate economic losses and risk will contribute
to potential reassessment of risk mitigation policies by the United Nations Office for Disaster Risk Reduction (UNDRR).
Keywords Disaster risk reduction· Fault normal· HAZUS· Economic losses· Performance-Based Engineering·
Resilience
Introduction
Disaster Risk Reduction (DRR) is part of the 11th sustain-
able development goal, regarding resilient infrastructure and
cities, of the United Nations. To decrease the human and
economic losses caused due to earthquakes (Daniell, 2014),
it is important to conduct seismic risk calculations. Seismic
risk assessment helps in predicting the probability of the
building and structural damage and economic losses (Pitila-
kis, 2015) according to potential seismic hazard in an area.
Once the seismic risk profile for an area is calculated, it is
used to bring forward design methods for new buildings, to
reinforce the current buildings (Caterino etal., 2018) and to
effectively overcome catastrophic situations. Seismic risk is
a function of hazard, vulnerability and exposure (Tyagunov
etal., 2004).
The Sendai framework (2015–2030) for Disaster Risk
Reduction (DRR) priority 1 about disaster risk manage-
ment requires understanding of hazard characteristics, vul-
nerability and exposure of assets. Seismic hazard includes
any physical phenomenon like ground motion, ground fail-
ure that can cause harm to human activities (Kijko, 2011).
Seismic hazard assessment involves predicting the levels of
shaking intensity that is expected to occur in a particular
region (Shedlock, 2002) along with their frequency of occur-
rence. Structure vulnerability analysis is a kind of pattern
recognition method on the basis of practical earthquake
damage data (Kassem etal., 2020). It involves studying the
behaviour of structures when subjected to earthquake load-
ing to quantify the susceptibility of different types of build-
ings to impact of earthquakes. The exposure model includes
collection of data on structural and physical characteristics
of buildings, infrastructure and population in the hazard
zone. This database is used to conduct rapid evaluation of
* K. S. K. Karthik Reddy
ce17resch01003@iith.ac.in
1 Indian Institute ofTechnology Hyderabad, NH-65Kandi,
Sangareddy, Telangana502285, India
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Interested readers are directed to the works of Karthik et al. [29], where the directivity site parameters are written in conjunction with the ductility demand imposed by subshear ground motions. The same work was later extended to evaluate risk assessment of buildings [74] but is limited to only subshear earthquake ruptures and the source parameter chosen in that study was position of nucleation asperity to estimate the risk associated with minimum and maximum directivity effects. ...
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... While the former reported the ductility demand of inelastic response of simple sdof in conjunction with the Bayless and Somerville [52] and Direct Point [53] directivity parameters, the latter extended this study to compute fragility analysis of 2 span single-column box girder skew bridges. Furthermore, the risk assessment computed for commercial steel frames corresponding to various storey heights by Payyappilly et al. [54] demonstrated variability even in terms of economic loss and injury estimation depending on their location around the fault. Velocity time history based on simulated ground motions at three rupture distances of 5 km, 10 km, and 15 km for three particular stations (S1, S2, and S3) have been plotted in Fig. 2. It can be observed that there is an increase in amplitude in the FN component of the S1 station with a change in the rupture scenario from UL0 to UL12. ...
Seismic assessment of steel frame subjected to simulated directivity earthquakes: The unilaterality of fault normal component at various rupture distances
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Directionality is prominent in the fault normal component of ground motion. It has a different effect on stations in the rupture direction on the tectonic fault than it does on stations in the opposite direction. Such pulse-like features observed in forward and backward directivity stations affect both low-rise and high-rise structures, depending on their fundamental period and the pulse period of ground motion. However, systematic availability of both forward and backward directivity ground motion for unilateral and bilateral earthquakes of the same magnitude at a similar rupture distance for a given fault is rare. So, multiple directivity scenarios are simulated using fracture mechanics-based principles. Using OpenSees, steel moment-resisting frames of 1, 5, and 9 stories, well designed according to building codes, are modeled, and their non-linear response is evaluated. Stations at constant rupture distances are used to compute fragility for each scenario separately. Variation inter-storey drift and peak floor acceleration, along with the hysteretic behavior of panel-zone springs, have also been studied for each of the directivity scenarios. Finally, the results obtained are compared to what is expected by HAZUS.
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Typically, near fault excitations are identified as large amplitude pulses with low frequency and short duration, showing the potential of damage in existing structures. The primary consequences of near fault excitations are fling step and forward directivity, which can impose unforeseen seismic demands on isolated structures. In this study, the behaviour of a five-storey building implemented with a friction pendulum system considering directivity and fling motions, is investigated. The governing equation of motions is derived and solved using Newmark beta method. Parametric studies and optimal analysis are performed for the base isolated building for different structural parameters under far fault, forward directivity and fling step motions. Moreover, the behaviour of base isolated building under seismic excitations with directivity and fling step pulses are significantly amplified when compared with far fault excitations. The gradient-based optimization technique is used to acquire optimal parameter of friction pendulum system. The frictional coefficient is considered as design variable to minimize the acceleration at the top storey. The study reveals that the near fault excitation with fling step motions results in larger demands than forward directivity pulses.
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Over the past few decades, there have been tremendous advancements in high-resolution performance-based earthquake engineering of individual facilities and in seismic risk assessment of geographically distributed systems. To a large extent, research and development have proceeded independently on performance-based methods to perform detailed evaluation of individual facilities (e.g., buildings and bridges) and consequence-based evaluations of distributed systems (e.g., large building inventories, transportation systems). For example, the FEMA P58 methodology, which represents the state-of-art in performance-based seismic design of buildings, involves high-fidelity nonlinear structural analyses of the building structural systems and detailed evaluation of damage and consequences to structural and nonstructural building components. The FEMA P58 approach has been implemented in software tools, such as PACT and SP3, which provide engineers with the ability for high-resolution seismic performance evaluation of alternative design solutions for new buildings and retrofit of existing buildings. At the other end of the spectrum, tools such as HAZUS and OpenQuake simulate geographically distributed building inventories using vulnerability functions, which for buildings are defined using basic attributes, such as building age, numbers of stories, construction material. Well-calibrated vulnerability models provide estimates of average damage or losses to certain classifications of buildings, but they do not have the resolution to discern detailed aspects of behavior. While there are efforts to apply building-specific FEMA P58 models to improve building-specific vulnerability functions for regional assessment, the modeling approaches and software tools for each operate independently. With the aim toward integrating facility-specific and regional simulation tools, the authors have developed an open source tool, called "pelicun" for probabilistic estimation of losses, injuries and community resilience under natural disasters. The pelicun framework disaggregates the available performance and risk assessment methods into their core components, allowing integration of various modeling approaches, from detailed FEMA P58 type methods to generalized fragility functions, into disaster simulations of geographically distributed communities of buildings. pelicun is implemented at the NSF-supported NHERI SimCenter as an open-source, platform-independent Python package. It uses a stochastic model that is sufficiently versatile to handle the high-fidelity component-based FEMA P58 method along with the more approximate building-level approach used by HAZUS. It allows users to modify or create their own fragility and consequence functions and use the built-in assessment methods. It can be used for building-specific evaluations in a stand-alone fashion or integrated into regional earthquake simulations. The software is available through a GitHub repository, where researchers are encouraged to edit and extend the scripts and share their developments with the community. While some of the first applications have been to buildings under earthquake hazard, the pelicun framework is extensible to other system components (e.g., bridges and transportation systems, piping and water distribution systems) and other hazards (e.g., hurricane wind and storm surge). This paper describes the underlying framework of pelicun and its main components. Case studies demonstrate the versatility of the methods available in pelicun and the extensibility of the framework.
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