The Effect of Magnitude Mw and Distance Rrup on the Fragility Assessment of a Multistory RC Frame Due to Earthquake-Induced Structural Pounding (original) (raw)
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Earthquake Resistant Engineering Structures XIII, 2021
The aim of this study is the probabilistic evaluation of the seismic performance of a multistory reinforced concrete (RC) frame structure due to the inter-story pounding effect. The assessment is performed through fragility curves at different performance levels. For this purpose, different probabilistic seismic demand models (PSDMs) are developed based on the real seismic response of the RC structure as a function of the spectral acceleration (Sa). In this direction, the inter-story (floor-tocolumn) pounding between an 8-story RC frame structure and a 3-story rigid barrier (very stiff structure) is examined. Three different initial gap distances (dg) between the adjacent structures are considered. The seismic fragility assessment of the 8-story RC structure without the inter-story pounding effect is also incorporated. Results indicate that the local performances of the columns of the 8-story RC structure are crucial demand parameters for the probabilistic assessment of the inter-st...
Probabilistic seismic demand model for pounding risk assessment
Earthquake Engineering & Structural Dynamics, 2016
Earthquake-induced pounding of adjacent structures can cause severe structural damage, and advanced probabilistic approaches are needed to obtain a reliable estimate of the risk of impact. This study aims to develop an efficient and accurate probabilistic seismic demand model (PSDM) for pounding risk assessment between adjacent buildings, which is suitable for use within modern performance-based engineering frameworks. In developing a PSDM, different choices can be made regarding the intensity measures (IMs) to be used, the record selection, the analysis technique applied for estimating the system response at increasing IM levels, and the model to be employed for describing the response statistics given the IM. In the present paper, some of these choices are analyzed and evaluated first by performing an extensive parametric study for the adjacent buildings modeled as linear single-degree-of-freedom systems, and successively by considering more complex nonlinear multi-degree-of-freedom building models. An efficient and accurate PSDM is defined using advanced intensity measures and a bilinear regression model for the response samples obtained by cloud analysis. The results of the study demonstrate that the proposed PSDM allows accurate estimates of the risk of pounding to be obtained while limiting the number of simulations required.
This study aims to develop a probabilistic seismic demand model (PSDM) for pounding risk assessment suitable for use within modern performance-based design frameworks. In developing a PSDM, different choices can be made regarding the intensity measures (IMs) to be used, the record selection, the analysis technique applied for estimating the system response for different IM levels, and the model to be employed for describing the response statistics given the IM. In the present paper, some of these choices are analyzed and discussed by considering the case of two adjacent buildings modeled as single-degree-of-freedom systems with linear and nonlinear hysteretic behavior. Based on the comparison, an optimal demand model is sought as the one that permits to achieve confident estimates of the response parameter of interest, i.e., the relative displacement demand, with few time-history analyses. This property allows reducing the complexity and computational cost associated with the pounding risk assessment.
Assessment of seismic-induced pounding risk based on probabilistic demand models
2017
The seismic-induced pounding between adjacent buildings is an undesirable event that can cause major damage and even structural collapse for structures with inadequate separation distance. This issue is particularly important in metropolitan areas, where the land space is limited and expensive. In order to minimize the pounding risk, existing design codes provide simplified numerical procedures and analytical rules for estimating the minimum separation distance that is needed to avoid pounding under a target seismic hazard scenario. However, these code procedures are characterized by unknown safety levels and, thus, do not permit to control explicitly the risk of pounding or the consequences of the impact. Previous research by two of the authors developed a reliability-based design methodology for the separation distance that corresponds to a target probability of pounding during the design life of adjacent buildings. This methodology was successfully applied to linear elastic struc...
Probabilistic seismic demand analysis for pounding risk assessment
Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures, 2014
This study aims to develop a probabilistic seismic demand model (PSDM) for pounding risk assessment suitable for use within modern performance-based design frameworks. In developing a PSDM, different choices can be made regarding the intensity measures (IMs) to be used, the record selection, the analysis technique applied for estimating the system response for different IM levels, and the model to be employed for describing the response statistics given the IM. In the present paper, some of these choices are analyzed and discussed by considering the case of two adjacent buildings modeled as single-degree-of-freedom systems with linear and nonlinear hysteretic behavior. Based on the comparison, an optimal demand model is sought as the one that permits to achieve confident estimates of the response parameter of interest, i.e., the relative displacement demand, with few time-history analyses. This property allows reducing the complexity and computational cost associated with the pounding risk assessment.
Probabilistic seismic risk evaluation of reinforced concrete buildings
The main objective of this article is to propose a simplified methodology to assess the expected seismic damage in reinforced concrete buildings from a probabilistic point of view by using Monte Carlo simulation. In order to do so, the seismic behaviour of the building was studied by using random capacity obtained by considering the mechanical properties of the materials as random variables. From the capacity curves, the damage states and fragility curves can be obtained, and curves describing the expected seismic damage to the structure as a function of a seismic hazard characteristic can be developed. The latter can be calculated using the capacity spectrum and the demand spectrum according to the methodology proposed by the Risk-UE project. In order to define the seismic demand as a random variable, a set of real accelerograms were obtained from European and Spanish databases in such a way that the mean of their elastic response spectra was similar to an elastic response spectrum selected from Eurocode 8. In order to combine the uncertainties associated with the seismic action and the mechanical properties of materials, two procedures are considered to obtain functions relating the peak ground acceleration to the maximum spectral displacements. The first method is based on a series of non-linear dynamic analyses, while the second is based on the well-known ATC-40 procedure called equal displacement approximation. After applying both procedures, the probability density functions of the maximum displacement at the roof of the building are gathered and compared. The expected structural damage is finally obtained by replacing the spectral displacement calculated using ATC-40 and the incremental dynamic procedure. In the damage functions, the results obtained from incremental static and dynamic analyses are compared and discussed from a probabilistic point of view.
2014
Practical methods for the probability-based seismic assessment of structural performance in terms of fragility curves relies on estimates of demand produced by earthquakes of different intensities. The uncertainties associated with these estimates are highly dependent on the interface variable adopted as the intensity measure (IMs), generating a need for analyzing the suitability of different candidate IMs, particularly in terms of their efficiency. An efficient IM is one that results in a relatively small dispersion of seismic demand measures, or engineering demand parameters (EDPs), conditional to each considered IM. Selecting an efficient IM will result in a narrower confidence interval for the conditional median EDP value for a given IM level or, from a different perspective, in a smaller number of analyses needed to obtain an acceptable confidence interval. To this aim, the simple study presented in this paper deals with the prediction of displacementbased response of a case-study reinforced concrete (RC) frame building, representative of mid-rise RC building classes in the Mediterranean region. The prediction is performed via statistical relationship between multiple (scalar) ground motion IMs and various EDPs, namely peak (over time) inter-storey drift ratio, maximum (over all stories) peak inter-storey drift ratio and roof drift ratio. Only a small set of potential IMs are considered in the preliminary investigation discussed in this study, namely peak ground acceleration, spectral acceleration at the initial fundamental period (for a damping ratio of 5%), and two advanced scalar parameters accounting for spectral shape over a range of periods. The relationship is built on data obtained from analysis of the frames subjected to over nine hundred ground motion records. An innovative capacity spectrum method is employed, which uses inelastic response spectra derived from actual earthquake accelerograms to estimate seismic demand and derive fragility curves. This approach has the advantage of simplicity and rapidity over other methods using accelerograms, as nonlinear dynamic analysis.
Soil Dynamics and Earthquake Engineering, 2019
This paper deals with the selection of optimal intensity measures (IMs) for displacement-based seismic demand assessment and fragility derivation of case-study mid-rise reinforced concrete (RC) frames. The considered frames represent distinct RC vulnerability classes in the Mediterranean region. Optimal IM selection is performed by means of probabilistic seismic demand models considering multiple IMs and various engineering demand parameters (EDPs). Based on findings from previous and concurrent studies, a small subset of potential IMs is investigated here, including conventional peak IMs and two advanced scalar IMs accounting for spectral shape over a range of periods. Probabilistic seismic demand models are built on data obtained from analysis of the casestudy frames subjected to over nine hundred ground motions by employing an innovative capacity spectrum method using inelastic response spectra derived from actual earthquake accelerograms to estimate seismic demand and derive fragility curves. This approach has the advantage of simplicity and rapidity over other methods as nonlinear dynamic analysis. This study concludes that advanced IMs, and particularly the ones accounting for the period elongation (due to the nonlinear structural behavior) and structure-specific parameters, can effectively satisfy all the selection criteria, including the hazard computability criterion.
Capacity, fragility and damage in reinforced concrete buildings: a probabilistic approach
The main goals of this article are the analysis of the use of simplified deterministic nonlinear static procedures to assess the seismic response of buildings, and to evaluate the influence that the uncertainties regarding the mechanical properties of the materials and of the features of the seismic actions have in the uncertainties of the structural response. A current reinforced concrete building is used as a guiding case study. In the calculation of the expected spectral displacement, deterministic static methods are simple and straightforward. In the case of non severe earthquakes, these approaches lead to somewhat conservative but adequate results when compared to more sophisticated procedures involving non-linear dynamic analyses. Concerning the probabilistic assessment, the strength properties of the materials, concrete and steel, and the seismic action are considered as random variables. The Monte Carlo method is then used to analyze the structural response of the building. The obtained results show that significant uncertainties are expected, as uncertainties in the structural response increase with the severity of the seismic actions. The major influence in the randomness of the structural response comes from the randomness of the seismic action. A useful example for selected earthquake scenarios is used to show the applicability of the probabilistic approach to assess the expected damage and risk analysis. An important conclusion of this work is the need to address the fragility of the buildings and expected damage assessment problem from a proba-bilistic perspective.
Probabilistic seismic demand modeling of local level response parameters of an RC frame
Bulletin of Earthquake Engineering, 2017
Probabilistic methods to evaluate the seismic vulnerability of reinforced concrete (RC) frames are largely used in the context of performance based design and assessment, often describing the structural response using global engineering demand parameters (EDPs) such as the maximum interstory drift. While such EDPs are able to synthetically describe the structural behavior, the use of local EDPs is necessary to provide a more realistic and thorough description of failure mechanisms of low-ductility frames lacking seismic details. The objective of this paper is to investigate viable probabilistic seismic demand models of local EDPs, which may be used in developing fragility curves for the assessment of the low-ductility RC frames. The present work explores adequate regression models, probability distributions and uncertainty variation of the demand models. In addition, the adequacy of several ground motion intensity measures (IMs) to be used for predictive modeling of local EDPs is investigated. A realistic benchmark three-story RC frame representative of non-ductile buildings is used as a case study to identify key considerations.