Impact of displacement demand reliability for seismic vulnerability assessment at an urban scale

Diana, Lorenzo; Manno, Andrea; Lestuzzi, Pierino; Podestà, Stefano; Luchini, Chiara

doi:10.1016/j.soildyn.2018.05.002

Cited by 10 publications

(8 citation statements)

References 20 publications

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“…e methodology used in this study for the nonlinear timehistory analysis (NLTHA) is similar to the one proposed in previous investigations [2,10]. Nonlinear responses of SDOF systems exposed to acceleration time-histories are computed and the difference between the obtained peak displacement demands and those predicted by the various simplified methods is calculated.…”

Section: Nltha Methodologymentioning

confidence: 99%

“…Reliable displacement demand predictions are therefore crucial for seismic vulnerability assessment of existing buildings. is is a key issue in vulnerability assessment at urban scale, where such displacement demand predictions are used for determining building damage using mechanical methods [2]. On the plateau of design spectra, Riddell et al [3] and later Vidic et al [4] proposed to compute the displacement demand based on a linear variation of the strength reduction factor as a function of the period.…”

Section: Introductionmentioning

confidence: 99%

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Accuracy Assessment of Nonlinear Seismic Displacement Demand Predicted by Simplified Methods for the Plateau Range of Design Response Spectra

Lestuzzi

Diana

2019

Advances in Civil Engineering

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The nonlinear seismic displacement demand prediction for low-period structures, i.e., with an initial fundamental period situated in the plateau of design response spectra, is studied. In Eurocode 8, the computation of seismic displacement demands is essentially based on a simplified method called the N2 method. Alternative approaches using linear computation with increased damping ratio are common in other parts of the world. The accuracy of three methods for seismic displacement demand prediction is carefully examined for the plateau range of Type-1 soil class response spectra of Eurocode 8. The accuracy is assessed through comparing the displacement demand computed using nonlinear time-history analysis (NLTHA) with predictions using simplified methods. The N2 method, a recently proposed optimization of the N2 method, and the Lin and Miranda method are compared. Nonlinear single-degree-of-freedom systems are subjected to several sets of recorded earthquakes that are modified to match design response spectra prescribed by Eurocode 8. The shape of Eurocode 8 response spectra after the plateau is defined by a constant pseudovelocity range (1/T). However, the slope of this declining branch may be specified using precise spectral microzonation investigation. However, the N2 method has been found to be particularly inaccurate with certain microzonation response spectra that are characterized by a gently decreasing branch after the plateau. The present study investigates the impact of the slope of the decreasing branch after the plateau of response spectra on the accuracy of displacement demand predictions. The results show that the accuracy domain of the N2 method is restricted to strength reduction factor values around 3.5. Using the N2 method to predict displacement demands leads to significant overestimations for strength reduction factors smaller than 2.5 and to significant underestimations for strength reduction factors larger than 4. Fortunately, the optimized N2 method leads to accurate results for the whole range of strength reduction factors. For small values of strength reduction factors, up to 2.5, the optimized N2 method and the Lin and Miranda method both provide accurate displacement demand predictions. However, the accuracy of displacement demand prediction strongly depends on the shape of the response spectrum after the plateau. A gently decreasing branch after the plateau affects the accuracy of displacement demand predictions. A threshold value of 0.75 for the exponent of the decreasing branch (1/Tα) after the plateau is proposed. This issue should be considered for the ongoing developments of Eurocode 8.

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Section: Nltha Methodologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Accuracy Assessment of Nonlinear Seismic Displacement Demand Predicted by Simplified Methods for the Plateau Range of Design Response Spectra

Lestuzzi

Diana

2019

Advances in Civil Engineering

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“…A relative uncertainty following a zero-mean normal distribution with a standard deviation of 7.5% is linked to the acceleration demand values given by the ADRS spectra. The base-shear values are estimated to be affected by a uniform relative uncertainty bounded between −20% and 20%, which also covers uncertainty related to the N2 method itself, which has been shown to be inaccurate for high frequency values when the equal displacement rule does not apply [70]. For the uncertainties related to the definition of DG boundaries the same values than for identification are used (see Section 3.3.1).…”

Section: Sources Of Uncertainty For Predictionsmentioning

confidence: 99%

A model-based data-interpretation framework for post-earthquake building assessment with scarce measurement data

Reuland

Lestuzzi

Smith

2019

Soil Dynamics and Earthquake Engineering

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Recent earthquake events throughout the world have once again exposed the vulnerability of buildings with respect to earthquakes. It is unlikely and unsustainable to design and-especially in regions with low-to-moderate seismic hazard-to retrofit all buildings to remain within elastic displacement ranges during earthquakes with high return periods. Therefore, post-earthquake assessment plays a fundamental role in the resilience of cities, given the potential to reduce time between an earthquake event and the clearance for (renewed) occupancy of a building. In this paper, a framework for model-based data interpretation of measurements of earthquake-damaged structures is presented. The framework allows engineers to combine ambient-vibration measurements and visual inspection to reduce parametric uncertainty of a high-fidelity model using the error-domain modelfalsification methodology. For building types that have limited stiffness contributions from non-structural elements (i.e. shear-wall buildings) and for which non-ductile failure modes (such as out-of-plane failure) can be excluded, reduction in natural frequency and damage grades derived from visual inspection provide global measurement sources for structural identification. The application of the proposed methodology to a shear-resisting building tested on a shake table illustrates that vulnerability-curve predictions provide accurate damage estimates for subsequent earthquakes with probabilities between 50 and 100 percent for five measured scenarios. In complete absence of baseline information regarding the initial building state and the earthquake signal, parametric uncertainty is reduced by up to 76 percent. This study thus demonstrates usefulness for certain building types to enhance post-seismic vulnerability predictions.

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“…For both methods of vulnerability determination (deterministic and probabilistic), the accuracy is calculated as the sum of the differences in absolute value between the number of buildings attributed by the ARL to each damage grade and the "real" number of building for each damage grade (Diana et al, 2018), according to the following equation:…”

Section: Validation Of Vulnerability Assessmentmentioning

confidence: 99%

“…With the typology distribution being defined in the previous section, the damage distribution for the entire city of Basel can be estimated for any seismic intensity. The damage distribution is achieved by the aggregation of the probability distribution multiplied by the number of related buildings according to the typology distribution (Diana et al, 2018).…”

Section: Seismic-vulnerability Assessment For the Entire City Of Basementioning

confidence: 99%

Application of Association Rules to Determine Building Typological Classes for Seismic Damage Predictions at Regional Scale: The Case Study of Basel

Diana

Thiriot

Reuland

et al. 2019

Front. Built Environ.

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Assessing seismic vulnerability at large scales requires accurate attribution of individual buildings to more general typological classes that are representative of the seismic behavior of the buildings sharing same attributes. One-by-one evaluation of all buildings is a time-and-money demanding process. Detailed individual evaluations are only suitable for strategic buildings, such as hospitals and other buildings with a central role in the emergency post-earthquake phase. For other buildings simplified approaches are needed. The definition of a taxonomy that contains the most widespread typological classes as well as performing the attribution of the appropriate class to each building are central issues for reliable seismic assessment at large scales. A fast, yet accurate, survey process is needed to attribute a correct class to each building composing the urban system. Even surveying buildings with the goal to determine classes is not as time demanding as detailed evaluations of each building, this process still requires large amounts of time and qualified personnel. However, nowadays several databases are available and provide useful information. In this paper, attributes that are available in such public databases are used to perform class attribution at large scales based on previous data-mining on a small subset of an entire city. The association-rule learning (ARL) is used to find links between building attributes and typological classes. Accuracy of wide spreading these links learned on <250 buildings of a specific district is evaluated in terms of class attribution and seismic vulnerability prediction. By considering only three attributes available on public databases (i.e., period of construction, number of floors, and shape of the roof) the time needed to provide seismic vulnerability scenarios at city scale is significantly reduced, while accuracy is reduced by <5%.

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Impact of displacement demand reliability for seismic vulnerability assessment at an urban scale

Cited by 10 publications

References 20 publications

Accuracy Assessment of Nonlinear Seismic Displacement Demand Predicted by Simplified Methods for the Plateau Range of Design Response Spectra

Accuracy Assessment of Nonlinear Seismic Displacement Demand Predicted by Simplified Methods for the Plateau Range of Design Response Spectra

A model-based data-interpretation framework for post-earthquake building assessment with scarce measurement data

Application of Association Rules to Determine Building Typological Classes for Seismic Damage Predictions at Regional Scale: The Case Study of Basel

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