Miroslav Nastev - Academia.edu (original) (raw)

Papers by Miroslav Nastev

Earthquake Spectra

A novel probabilistic methodology for regional seismic site characterization is proposed and appl... more A novel probabilistic methodology for regional seismic site characterization is proposed and applied to a region with highly heterogeneous surficial geology and varying soil sediment thickness and stiffness. The method combines various sources of geological and geotechnical uncertainties to develop a three-dimensional (3D) shear-wave velocity ( Vs) model and evaluate the associated uncertainties. A 3D geological model of the unconsolidated deposits was developed using geostatistical interpolation and simulation methods. Sequential indicator simulations produced a quantitative geologic model that explicitly quantified geological uncertainties based on the likelihood of specific soil types occurring. In situ measurements and multivariate statistical analysis allowed the development of empirical correlations between Vs, geotechnical parameters, depth, and soil types. The resulting 3D Vs values were estimated on the basis of Vs-depth correlations and the probability of occurrence of eac...

Geosciences

Knowledge of the stratigraphic architecture and geotechnical properties of surficial soil sedimen... more Knowledge of the stratigraphic architecture and geotechnical properties of surficial soil sediments is essential for geotechnical risk assessment. In the Saguenay study area, the Quaternary deposits consist of a basal till layer and heterogeneous post-glacial deposits. Considering the stratigraphic setting and soil type heterogeneity, a multistep stochastic methodology is developed for 3D geological modelling and quantification of the associated uncertainties. This methodology is adopted for regional studies and involves geostatistical interpolation and simulation methods. Empirical Bayesian kriging (EBK) is applied to generate the bedrock topography map and determine the thickness of the till sediments and their uncertainties. The locally varying mean and variance of the EBK method enable accounting for data complexity and moderate nonstationarity. Sequential indicator simulation is then performed to determine the occurrence probability of the discontinuous post-glacial sediments (...

Journal of Earthquake Engineering

Modified Newmark method is proposed including the equivalent seismic loading and critical acceler... more Modified Newmark method is proposed including the equivalent seismic loading and critical acceleration dependant on the dynamically exerted plastic yielding and tension cutoff effects along the bas...

Buildings, 2022

This special issue of Buildings Journal brings together outstanding papers presented at the 1st C... more This special issue of Buildings Journal brings together outstanding papers presented at the 1st Croatian Conference on Earthquake Engineering 1CroCEE, held at the Faculty of Civil Engineering, University of Zagreb, Croatia, 22–24 March 2021 [...]

Geoenvironmental Disasters, 2021

A seismic microzonation study was conducted to refine the seismic hazard model for the city of Sa... more A seismic microzonation study was conducted to refine the seismic hazard model for the city of Saguenay, Canada. The Quaternary geology underlying Saguenay shows complex glacial and post-glacial stratigraphy with a number of buried valleys filled with fluvioglacial and glaciomarine sediments. High impedance contrast between rock formations and surficial sediments is prone to seismic amplification. To evaluate their applicability, advantages and limitations in capturing the geological specificity of the study area, four site classification methods were applied: the current National Building Code of Canada (NBCC) and Eurocode 8, both mainly based on the average shear-wave velocity for the surficial sediments (VS,avg) and for the top 30 m (VS,30); a method based on the fundamental site period (T0); and a hybrid method based on the combination of VS,30, T0 and VS,avg. The study specifically aimed to evaluate the importance of the site classification parameters on the resulting microzona...

Bulletin of Earthquake Engineering, 2021

This paper highlights the principal features of the Mw5.4 Zagreb earthquake. Located within the c... more This paper highlights the principal features of the Mw5.4 Zagreb earthquake. Located within the city limits at a depth of 10 km, the earthquake generated a peak ground acceleration of more than 0.2 g and a maximum spectral acceleration of about 0.6 g at 0.1 s in the historic downtown area. The situation was particularly challenging since the event occurred amid a partial Covid-19 lockdown at temperatures close to 0 °C, emphasizing the extensive and complex vulnerability of the local communities and individuals. 27 people were reported severely injured, one of which later died. The surprisingly high economic costs, needed to achieve a full reconstruction of damaged buildings and infrastructure in the affected area, are currently evaluated at more than 10B euros. Description of the organization of the emergency response in the first days and the observed damage to buildings is given with typical examples. The focus is on the performance of older masonry residential and cultural herita...

Fluid dam interaction can impact significantly the dynamic response of dams, in particular when d... more Fluid dam interaction can impact significantly the dynamic response of dams, in particular when dams are subjected to strong seismic excitations. The phenomenon has been for the first time physically explained and mathematically solved by Westargaard with the added mass concept. During recent decades, various BEM-FEM and FEM-FEM techniques have been developed to account for the significant parameters which influence the accuracy of the calculated hydrodynamic effects. A BEM-FEM solution is presented based on the use of the matrix of hydrodynamic influence to effectively analyze extensive domains of complex fluid-dam-foundation rock systems. The simulations were conducted with the ADAD-IZIIS software for static and dynamic analysis and design of dams. Validation was conducted by comparing the results with those obtained with the commercially available Adina software. The validation examples showed effective computation time and accurate and stable solution.

In an effort to reduce seismic risks, the Geological Survey of Canada has recently taken importan... more In an effort to reduce seismic risks, the Geological Survey of Canada has recently taken important steps by initiating a project on quantitative assessment of earthquake related risks. One of the objectives of this project is to study the seismic vulnerability of historic stone masonry buildings generally known for their poor performance during strong ground motion. This paper focuses on the development of analytical displacement-based fragility curves re- flecting the characteristics of existing stone masonry buildings in Canada. The fragility anal- ysis provides the necessary link between the building damage and earthquake intensity in a probabilistic setting, where the extent of building damage is best correlated to the amount of induced building displacement. The old historic center of Quebec City was selected as a typi- cal study area due to the concentration of stone masonry buildings, which combined to the high heritage value increases the potential consequences of failure. C...

Seismic risk assessment is the key component of the disaster resilience planning process in earth... more Seismic risk assessment is the key component of the disaster resilience planning process in earthquake prone areas. In the last decades, the US FEMA’s loss assessment methodology HAZUS-MH has become a de facto standard due to its well developed and widely accepted analytical approach for damage and loss calculations. In practice, preparing the necessary input layers and running the iterative approach for calculating the performance point of structures can be time consuming, and require advanced knowledge of GIS. As an alternative, a prototype of a rapid risk assessment tool, based on the same structural parameters but with a different computation algorithm, was developed. The tool meets the needs of the target groups of non-expert emergency management and public safety decision makers through easily understandable input and output information and flexible interactive environment, while maintaining the scientific rigour. It uses a database with pre-calculated vulnerability curves def...

IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 2018

Flood inundation mapping is very useful for both risk assessment and for providing situational aw... more Flood inundation mapping is very useful for both risk assessment and for providing situational awareness during an emergency. Flood modelling is often complex and requires many variables and parameters, which are often unavailable. In this paper, the capability of simplified flood models, relying exclusively on digital terrain models was explored for two study areas. Three simplified conceptual flood models were tested: (i) planar method (ii) inclined plane and (iii) height above nearest drainage network (HAND) model. The accuracy and performance of these models were evaluated using two criteria: inundation extent and computation time. Findings indicate the HAND model is the best predictor of inundation extent. Though the preprocessing time for the HAND model is lengthy, once completed, the time to simulate flood depth at a variety of water levels is rapid, making this model the most suitable choice for on-demand flood inundation mapping.

IABSE Symposium, Vancouver 2017: Engineering the Future, 2017

The prediction of earthquake damage to highway bridges is essential for informed decision on the ... more The prediction of earthquake damage to highway bridges is essential for informed decision on the post-earthquake bridge functionality. This paper presents a simplified method based on the development of fragility functions of typical reinforced concrete highway bridges and its validation. The concept of fragility functions represents a probabilistic relationship between the seismic intensity measure IM (e.g. spectral acceleration) and the degree of bridge damage. Median IMs of the fragility functions for the assumed damage states are developed using closed-form relationships based on the capacity spectrum method for seismic demand assessment. For each damage state, these relationships correlate the displacement threshold to the corresponding median IMs in terms of the input spectral acceleration at 1.0 sec. The simplified fragility assessment method was validated with dynamic analyses of an existing three span continuous girder reinforced concrete bridge in Quebec. The method reveal...

While Canada is exposed to a variety of natural hazards, most risk and emergency managers current... more While Canada is exposed to a variety of natural hazards, most risk and emergency managers currently lack the necessary tools and guidance to adequately undertake rigorous risk assessments. Unlike the complex computer models for natural hazard risk assessment intended for use by a small number of technical experts, userfriendly rapid risk assessment tools are being developed to allow non-expert users from the public safety community to run otherwise complex risk scenarios at a ‘press of a button’. This paper reports on the ongoing activities carried out jointly by the federal government and academia on the development of inventory and seismic and flood risk analysis tools. Application examples at urban scales for Ottawa and Quebec City are given.

Risk models, which describe the relationship between hazard intensity and a damage ratio are incr... more Risk models, which describe the relationship between hazard intensity and a damage ratio are increasingly used in flood risk management. Direct tangible damage resulting from flooding is typically computed based on the internationally accepted method of depth-damage curves. Depth-damage curves relate absolute damage (in terms of currency) or relative loss (percentage of the estimated total replacement value of property) to a given flood depth. Many depth-damage functions in use today are computed from synthetic data, where data are collected from a representative sample of buildings with similar properties in a floodplain during field surveys. A primary problem when assessing risk at an objectbased spatial resolution using depth-damage curves is that these damage functions represent an average structure in the study location. There is great variability across any given structural class as well as variation within individual structures in a structural category (and across communities...

This paper presents the results of a seismic risk assessment study of the Old Quebec City, Canada... more This paper presents the results of a seismic risk assessment study of the Old Quebec City, Canada, for 1220 existing buildings, mainly pre-code unreinforced brick and stone masonry. Vulnerability modelling included a set of successive analytical development of capacity curves; displacement-based fragility functions; and vulnerability functions of the mean damage factor defined as repair to replacement cost ratio. These functions were conditioned to a structure-independent hazard intensity measure (IM), e.g. spectral acceleration. The distribution of the potential damage was evaluated for a scenario event of magnitude 6.2 at distance 15 km (M6.2R15). The results show that approximately 35% of the stone masonry buildings and 17% of the brick masonry buildings would suffer damage. A sensitivity analysis conducted to investigate the impact of uncertainties in the vulnerability modelling, showed that the damage estimates are significantly affected by the uncertainty in the ground shaking...

The dam-fluid interaction is significantly affected by the irregularity of the terrain in the vic... more The dam-fluid interaction is significantly affected by the irregularity of the terrain in the vicinity of the dam-fluid interface. The joint vibration of the dam and canyon walls generates pressure and dilatational waves as functions of several variables. Besides the geometry and mechanical properties of the dam-reservoir system, the distance to the non-reflecting truncation boundary is important parameter to be considered in the computation of the hydrodynamic forces. The direction of the seismic excitation should also be taken into account. Different modelling scenarios of arch dam-fluidreservoir systems were conducted and compared via a time dependent indicator referred to as ‘cumulative hydrodynamic energy’. The comparison indicates that, depending on the direction of excitation, the combined vibration of the dam and reservoir with complex topography could generate between 10% and 100% higher hydrodynamic energy at the dam-fluid interface than that generated by a dam-regular res...

Water, 2018

The authors wish to make the following corrections to this paper [...]

ZBORNIK RADOVA GEO-EXPO 2019, 2019