Mário Marques

Evaluation of Nonlinear Static Procedures in the Assessment of Building Frames

In recent years a number of nonlinear static procedures (NSPs) have been developed and proposed. Such pushover-based seismic assessment procedures are relatively straightforward to employ and are generally chosen over nonlinear dynamic analysis, especially within the realm of design office application. Parametric comparisons between the different NSPs available, however, are still somewhat sparse. In this work, five commonly employed NSPs (the N2 method, capacity spectrum method, modal pushover analysis, adaptive modal combination procedure, and the adaptive capacity spectrum method) are applied in the assessment of 16 frames subjected to a large number of input motions with a view to assess the accuracy level of such approaches through comparison with nonlinear dynamic analysis results. The evaluation shows that all the NSPs are able to accurately predict displacements and to produce reasonable estimates for other response parameters, with limited dispersion. Even though no single NSP tested led to consistently superior results, modal pushover analysis and the adaptive capacity spectrum method seemed to perform slightly better.

Including Multiple IMTs in the Development of Fragility Functions for Earthquake Loss Estimation

This article presents a proposal for an innovative approach for including multiple intensity measure types (IMTs) in the representation of building fragility. Thousands of nonlinear dynamic analyses are performed in a 2D environment in which reinforced concrete frames are simulated using a Monte Carlo approach, according to geometrical and material variability of typical pre-code reinforced concrete buildings in Portugal. Seismic action variability is foreseen through the selection and scaling of appropriate Spectrum compatible record sets, following the most recent proposals for linking nonlinear dynamic analysis back to probabilistic seismic hazard. A literature review of seismic Intensity Measures is performed, in order to select a number of IMTs capable of representing a comprehensive set of earthquake shaking characteristics. A proposal for multiple IMT based fragility is outlined, whereby variability in structural damage effects along the considered seismic intensity range is accounted for by including the explicative power of an additional set of IMTs.

Investigation of the Characteristics of the Portuguese Moment-frame RC Building Stock

The computation of fragility models can be carried out using post-earthquake damage data or through the development of numerical models capable of reliably representing the structural behaviour of a given building typology when subjected to a set of ground motion records. In Portugal, due to the lack of data regarding groundshaking damage, analytical methodologies are often followed to evaluate the structural vulnerability of the existing building stock. However, these methodologies require advanced knowledge about the geometric and material characteristics of the building typologies, which is often not available or poorly characterized. In this study, the material and geometric properties of the RC buildings, which represent approximately 50% of the Portuguese building stock, were thoroughly analysed. In order to do so, 400 drawings and design specifications from real buildings were gathered throughout the country, in cooperation with private practitioners, design offices and public institutions. For each building drawing, the main frames in the structure that would resist eventual lateral loads were chosen in order to measure the following set of geometric parameters: ground story and upper storeys heights, column widths and depths, beam lengths, widths and depths, and slab thicknesses. The distribution of each geometric property was modelled considering several probabilistic distributions (normal, lognormal, exponential, gamma, beta), and their statistical parameters were derived using the maximum likelihood approach. These results can be used for numerical analysis, thus allowing a better understanding of the physical vulnerability of the RC building stock in Portugal.

Hazard Disaggregation and Record Selection for Fragility Analysis and Earthquake Loss Estimation

Economic losses and collapse probability are critical measures for evaluating the earthquake risk of existing buildings. In this context, this study sheds light on several problems and limitations in current practice of hazard-consistent ground-motion selection and fragility analysis, focusing on the impact that (commonly assumed) approximations in disaggregation outputs have on the aforementioned risk metrics, as opposed to an exact solution. These issues are investigated for several building classes, seismicity models and ground motion prediction equations (GMPE), for a site in the city of Lisbon (Portugal). It is observed that only an exact (i.e., rupture-by-rupture) disaggregation can lead to satisfactory results in terms of accuracy, when limit state criteria are not structure-specific. On the other hand, an approximate method is proposed, which still leads to statistically valid results regardless of the chosen structural class, seismicity model or GMPE.

NUMERICAL MODELLING AND CALIBRATION OF RC COLUMNS UNDER AXIAL LOADING

This work presents the first step of a methodology to calculate monetary losses in reinforced concrete moment resisting buildings through an innovative and advanced methodology. This framework involves the correlation between the physical damages that a structural component may experience during seismic events with meaningful engineering demand parameters. The establishment of this correlation constitutes the first phase of the methodology and is obtained through detailed finite element simulations of the critical structural elements. In this paper the development of numerical modeling strategies for the detailed simulations of five columns are described. The paper describes step by step the whole calibration process involving mesh sensitivity studies, evaluation of the influence of the compression fracture energy, geometric nonlinearity, bond-slip action and the buckling of the compressed reinforcements. In order to simplify the problem, pushover analysis is adopted to analyze all the models. 4869 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 4869-4880

Investigation of structural fragility for risk-targeted assessment

This paper analyzes the structural fragility of buildings designed according to the European regulation, in order to identify key aspects that impact risk-targeted hazard assessment. The performance of new buildings is assessed through 3D finite element models and non-linear dynamic analysis. These results were used to compute fragility functions for the damage states of interest for risk-targeted hazard assessment. Conclusions are drawn regarding their influence on the expected annual probability of collapse or of exceeding damage states of interest. The results presented in this study permit a better understanding of the seismic behaviour of new buildings, and consequently of the increase in the reliability brought by the adoption of the risk-targeted hazard methodology.