Abstract
The post‐earthquake recovery of a community depends on the ability of important buildings to perform their functions. Lifeline and other critical buildings that meet a predictable enhanced ...seismic performance increase the community's disaster risk management capacity. In prescriptive force‐based design standards, the seismic design force for these buildings is typically enhanced using an importance factor depending on the risk category. The present paper proposes an innovative framework based on performance‐based seismic design (PBSD) principles using risk‐targeted importance factors suitable for use with prescriptive standards. The framework decouples probabilistic assessments of building typologies to experts, while the structural designers can continue the conventional design approach. The framework explicitly considers probabilistic seismic demand, uncertainty in the performance of the building, and the inter‐building variation within a particular building typology in seismic performance. Six special reinforced concrete (RC) frame buildings conforming to Indian standards are selected to illustrate the framework. Sensitivity studies on parameter selection are used to establish the framework's robustness. An expression for the importance factors is also proposed. The use of the proposed importance factor expression is shown to meet a wide range of risk targets corresponding to different performance levels. The paper also proposes design factors for
enhanced performance objectives
suitable for the risk‐targeted prescriptive design. Further, the framework is implemented to estimate the seismic risk associated with existing building typology conforming to prevalent design standards. The assembly‐ and critical‐category RC buildings are found to require higher importance factors for achieving enhanced performance objectives than currently prescribed.
This article examines the baseline resilience of reinforced concrete (RC) moment frame buildings conforming to the seismic design standards of Canada. Metrics for robustness, rapidity, and resilience ...are evaluated to capture the system's reliability, speed of recovery, and socioeconomic impacts. Buildings of different heights are evaluated using nonlinear time-history analyses. Six damage states are defined as disjoint branches of an event tree depending on the building's path to recovery. For a scenario earthquake of magnitude 7.3 magnitude at a distance of 30 km from Vancouver, the housing occupancy recovery trajectory is developed. Monte Carlo simulations are used to propagate uncertainty from seismic hazards to the building response to the lead time required for recovery. Buildings are found to maintain 50%-65% of their pre-event housing occupancy in the immediate aftermath. The housing occupancy is restored to 90% within 2-4 months, with a shorter recovery period for low-rise buildings, whereas the system resilience level requires 6 months to 1 year for restoration to 90%. Empirical data from the Loma Prieta (1989) and Northridge (1994) earthquakes are used to compare analytically predicted repair times. The findings from this article will facilitate the shift to resilience-based design in Canada.
A vast majority of the world's reinforced concrete (RC) buildings are designed using prescriptive force‐based methods. In addition to safety, there is growing demand to meet additional performance ...objectives to limit economic losses and minimize disruption after smaller earthquakes. A framework is proposed that allows prescriptive design standards to deliver multi‐objective risk targets. It adopts an explicitly probabilistic approach considering uncertainty in seismic demand and structural capacity. A rational basis for targeting multiple performance metrics is actualized. The framework provides the first step of a practical strategy to migrate to the performance‐based design of buildings in a phased manner. Using the framework, risk‐targeted safety factors (RTSF) are derived in conjunction with the prescriptive design method to meet different target risk spaces. The framework proposes the replacement of importance factor, which does not quantify performance or risk or considers the building typology, with RTSFs. The framework is illustrated using six example RC buildings representing special moment frame typology conforming to prevalent Indian standards. The results indicate that such typology has an annual frequency of collapse of 1 × 10−4, an annual loss‐of‐operationality of 20 × 10−4, and an expected annual loss of 3 × 10−4. For the same typology, a four‐fold reduction requires an RTSF value of 1.6 for collapse risk, whereas the risk of loss‐of‐operationality necessitates a larger RTSF of 2.0. The larger RTSFs for higher performance illustrates additional design requirement that can only be obtained when considering multiple performance objectives. The framework is universally applicable for any lateral load‐resisting system and selected performance metrics.
Large parts of Asia, Europe, and the eastern USA have high population concentrations in moderate seismic regions (MSR), where very large earthquakes are rare. With rampant construction in the cities ...located in MSRs, a relatively moderate earthquake can turn into a catastrophe. Limiting the collapse has been the conventional performance objective for regions with high seismicity. However, this does not necessarily translate into a more desirable target of life-safety under design basis earthquake in MSRs. The present paper investigates the seismic performance of non-ductile reinforced concrete (RC) buildings that were common before the advent of modern design standards, and are found in very large numbers. An analytical model capturing the shear failure is employed using a drift-based limit state material. The results show that a hybrid index captures moderate damage more accurately than the prevalent drift-based index. The paper further shows that while a generic ground motion suite accurately estimates the median fragility, it fails to capture the uncertainty. A 7-story non-ductile RC archetype building was found to be at a collapse prevention risk of 2
×
10
–4
. The seismic risk deaggregation reveals that seismic risk consistency can be enhanced by explicit specification of the seismic forces for retrofitting. The study shows that the stringent seismic risk targets can be met by non-ductile buildings in MSR, provided they are designed or retrofitted with constraints on strong column weak beam factors. The study will facilitate in developing a scheme for prioritizing and devising the retrofit of pre-modern code and non-ductile deficient buildings.
A framework for incorporating probabilistic seismic performance during prescriptive design of reinforced concrete buildings using Indian building codes is presented. The second-generation ...performance-based design procedure is considered. Thirty special RC frame buildings have been numerically analyzed through nonlinear static and time history analyses. Effects of seismicity, building height, bay-width, and number of bays on building performance are investigated. A generalized expression for the overstrength factor is proposed. Expression for response reduction factor to achieve the desired level of performance objective is also proposed. Low- and mid-rise buildings in the high seismic region designed using current codes are found to be deficient.
•In the Kemeny–Snell axiomatic framework, algorithms are proposed for rank aggregation.•Two proposed algorithms, FUR and SIgFUR, outperform state-of-the-art algorithms.•Algorithms are efficient in ...terms of run time as well as performance.•Various examples from real and simulated data are provided to compare proposed algorithms.
Rank aggregation problem is useful to practitioners in political science, computer science, social science, medical science, and allied fields. The objective is to identify a consensus ranking of n objects that best fits independent rankings given by k different judges. Under the Kemeny framework, a distance metric called Kemeny distance is minimized to obtain consensus ranking. For large n, with present computing powers, it is not feasible to identify a consensus ranking under the Kemeny framework. To address the problem, researchers have proposed several algorithms. These algorithms are able to handle datasets with n up to 200 in a reasonable amount of time. However, run-time increases very quickly as n increases. In the present paper, we propose two basic algorithms— Subiterative Convergence and Greedy Algorithm. Using these basic algorithms, two advanced algorithms— FUR and SIgFUR have been developed. We show that our results are generally superior to existing algorithms in terms of both performance (Kemeny distance) and run-time. Even for large number of objects, the proposed algorithms run in few minutes.
The 2020 National Building Code of Canada (NBCC) seismic hazard model (SHM) marks a comprehensive update over its predecessor (NBCC 2015). For different regions in Canada, this will have an impact on ...the design of new buildings and performance assessment of existing ones. In the present study, a recently developed hybrid building system with reinforced concrete (RC) moment-resisting frames and cross-laminated timber (CLT) infills is assessed for its seismic performance against the latest SHM. The six-story RC-CLT hybrid system, designed using the direct displacement-based method, is located in Vancouver, Canada. Along with very high seismicity, southwestern British Columbia is characterized by complex seismotectonics, consisting of subduction, shallow crustal, and in-slab faulting mechanisms. A hazard-consistent set of 40 ground motion pairs is selected from the PEER and KiK-net databases, and used to estimate the building’s seismic performance. The effects of using steel slit dampers (associated with large hysteresis loops) and flag-shaped energy dissipators (associated with the recentering capability) are investigated. The results indicate that the hybrid system has good seismic performance with a probability of collapse of 2–3% at the 2475-year return period shaking intensity. The hybrid building with steel slit dampers exhibits a collapse margin ratio of 2.8, which increases to 3.5–3.6 when flag-shaped dissipators are used. The flag-shaped dissipators are found to significantly reduce the residual drift of the hybrid building. Additionally, the seismic performance of the hybrid building equipped with flag-shaped dissipators is found to improve marginally when the recentering ratio is increased.
Radiometric Quality Evaluation of INSAT-3D Imager Data Prakash, S.; Jindal, D.; Badal, N. ...
International archives of the photogrammetry, remote sensing and spatial information sciences.,
01/2014, Letnik:
XL-8, Številka:
8
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
INSAT-3D is an advanced meteorological satellite of ISRO which acquires imagery in optical and infra-red (IR) channels for study of weather dynamics in Indian sub-continent region. In this paper, ...methodology of radiometric quality evaluation for Level-1 products of Imager, one of the payloads onboard INSAT-3D, is described. Firstly, overall visual quality of scene in terms of dynamic range, edge sharpness or modulation transfer function (MTF), presence of striping and other image artefacts is computed. Uniform targets in Desert and Sea region are identified for which detailed radiometric performance evaluation for IR channels is carried out. Mean brightness temperature (BT) of targets is computed and validated with independently generated radiometric references. Further, diurnal/seasonal trends in target BT values and radiometric uncertainty or sensor noise are studied. Results of radiometric quality evaluation over duration of eight months (January to August 2014) and comparison of radiometric consistency pre/post yaw flip of satellite are presented. Radiometric Analysis indicates that INSAT-3D images have high contrast (MTF > 0.2) and low striping effects. A bias of <4K is observed in the brightness temperature values of TIR-1 channel measured during January–August 2014 indicating consistent radiometric calibration. Diurnal and seasonal analysis shows that Noise equivalent differential temperature (NEdT) for IR channels is consistent and well within specifications.
PDF
