Typology of NSPA Pushover Curves and Surfaces for 3D Performance-Based Seismic Response of Structures

Cosic M., Brcic S.: Typology of NSPA Pushover Curves and Surfaces for 3D Performance-Based Seismic Response of Structures (presentation)

This presentation shows a typology of pushover curves and the originally developed pushover surfaces based on the generalization of the nonlinear response of the 3D system to the earthquake action. By determination and analysis of the NSPA (Nonlinear Static Pushover Analysis) pushover surface, it is possible to obtain a more complex and a more complete insight of the response and performance of 3D models of structures exposed to the bidirectional seismic action. The setting which served as a base for the development of the mathematical formulation and generation of the NSPA pushover surface presents the application of NSPA pushover curve for the response of the system in one direction. By integrating the system responses for a number of directions, i.e. attac angles of directions of earthquake action, the presentation of the 3D response of the system in the capacity domain is achieved. The typology of NSPA pushover curves is derived as a function of the existence of linear, nonlinear and collapse subdomain, and also considerations are made taking into account the nonlinear stiffness and ductility class of the system. The typology of NSPA pushover surface is derived based on the generalized model of the system response through ductility, ductility in hardening/softening zone and a coefficient of the relationship of stiffness in the nonlinear and linear domain, based on which it is possible to create systems of different stiffness, strength and ductility. The research presented in this paper defines the typological models of NSPA pushover surfaces based on which further discussion can be done on real pushover surfaces of 3D models of structures with a more complex, particularly non-symetric geometry, as well as variation of responses of the system due to bidirectional seismic actions.

Development of Ground Motion Record Surface and Response Spectra Surface

Cosic M., Brcic S., Susic N., Folic R., Bozic-Tomic K.: Development of Ground Motion Record Surface and Response Spectra Surface (presentation)

The presentation shows a mathematical formulation of an originally developed ground motion record surface (GMRS) and response spectra surface (RSS) for the presentation of 2D seismic ground motion records (GMR) and the corresponding response spectra (RS), respectively. These surfaces are constructed by transformation from 2D polar coordinate system to a 3D cylindrical coordinate system and then to the 3D orthogonal coordinate system. The principle of application of three orthogonal coordinates for each discrete value is used in order to achieve easy manipulation and interpolation of spatial surface. Scaling of accelerograms was carried out using two procedures: the Least Square Method (LSM) and Spectral Matching (SM).

Pile Integrity and Load Testing: Methodology and Classification

Cosic M., Bozic-Tomic K., Susic N.: Pile Integrity and Load Testing: Methodology and Classification (presentation)

The presentation shows the methodology and classification of pile integrity and load testing, in compliance with current foreign standards, as well as our own defined segments of standard improvement and our own definitions of certain key elements. The classification has been conducted according to the test types which clearly define the pile testing process, analysis methods, and test results processing. Beside the basic division of pile testing to integrity tests and load tests, there is also an additionally defined group of shaft control tests in the case of bored piles, since for the proper shaft formation, when it comes to bored piles, certain qualitative-quantitative criteria must be fulfilled beforehand. Presented in this way, the methodology and classification of pile integrity and load tests serves, primarily, an educational purpose for civil and geotechnics engineers who deal with this issue, to additionally introduce innovations in this field of testing and and clarify all the elements of the testing since contradictory opinions and disagreements regarding the testing details are quite common in practice.

Probabilistic Analysis of Bearing Capacity of Piles

Cosic M., Susic N., Folic R.: Probabilistic Analysis of Bearing Capacity of Piles (poster)

The poster shows a probabilistic concept for determining the pile bearing capacity, taking into account the variability of CPT test parameters (stochastic simulations) and methodology of calculation according to the requirements of Eurocode 7. Solutions obtained using this approach were compared with those obtained from the static load test (SLT).

Bridges: Nonlinear Analyses, Probability Theory and Optimization Theory

Cosic M., Folic R., Folic B.: Bridges: Nonlinear Analyses, Probability Theory and Optimization Theory (poster)

The poster shows a multidisciplinary approach to the assessment of seismic performances based on the Performance-Based Earthquake Engineering (PBEE), taking into account the multi-criteria optimization theory in analyzing the priority methods for bridge rehabilitation/strengthening. One bridge model was subjected to nonlinear static pushover analyses (NSPA), target displacement analyses using the spectrum capacity method (CSM), vulnerability analyses, and reliability analyses, while for a damaged bridge, in addition to be considered using the above methods, was also analyzed using the VIKOR method of multi-criteria optimization.

Performance-Based Nonlinear Seismic Analysis

Performance-based nonlinear seismic analysis

Cosic M.: Performance-Based Nonlinear Seismic Analysis (presentation)

The presentation shows a part of the developed theoretical formulations and results of numerical analyses conducted in doctoral dissertation, which is defended at the Faculty of Civil Engineering University of Belgrade in 2015. In summary volume presents the research in the field of:

– ground motion records and response spectras,

– research in the field of non-linear responses of frame system that participate in the structural system of frame buildings,

– research in the field of non-linear response of the 3D model of frame buildings,

– research in the field of relations of the 3D model of frame buildings response/seismic demand.

Pile Tests

Cosic M., Folic R., Susic N.: Pile Tests (presentation)

Based on the analysis of a large number of scientific papers, the authors of this presentation show their own classification pile tests. The general classification is conducted using high strain and low strain tests, i.e. tests whose basic purpose is to determine the capacity of piles and tests the purpose of which is to analyze the integrity of piles. The pile capacity and integrity tests are critically analyzed by defining their advantages and disadvantages using in-situ investigations, cost effectiveness, requirements regarding the special education of engineers, the quality of data obtained, complexity of data processing and the quality of the processed end results. The proposed classification of pile capacity and pile integrity tests enables to identify very effectively which is the optimal test type for further geotechnical analysis of structures and which type of test should be used in the phase of geotechnical testing for designing and scientific research.

Seismic Methods

Folic R., Cosic M.: Seismic Methods (presentation)

The authors of the presentation, on the basis of the analysis of several thousand scientific papers, presented their original systematization of nonlinear seismic methods for structural performance analysis, which were developed in the last twenty years. Nonlinear seismic methods are generally classified into two groups: Nonlinear Static Analyses (NSA) and Nonlinear Dynamic Analyses (NDA). The analyses of non linear seismic structural response were classified separately from the target displacement analysis which defines the relationship of the seismic demand and the seismic response. On the other hand, the classification was also conducted depending on whether a nonlinear response of the system is obtained by the implementation of incremental-iterative procedures or by the implementation of semi-iterative and/or semi-incremental procedures. Nonlinear Dynamic Analyses were classified according to the concept of mathematical formulation, i.e. whether they are based on only one dynamic analysis, several dynamic analyses or are solved in combination with other methods. By implementing the conducted systematization and classification of nonlinear seismic methods, on can very efficiently consider which type of method is optimal for structural analysis and which type of method should be taken into account in the phase of preliminary and final analyses in the course of scientific research and professional projects.

Nonlin Quake software

Cosic M., Brcic S., Folic R., Susic N.: Nonlin Quake Software (presentation)

The presentation shows the original developed software NonlinQuake for performance-based seismic analysis of 3D structural models. Software Nonlin Quake consists of several independent compatible softwares that implements: create a database of two componential ground motion records (GMR), generation and processing of multicomponential GMR, creating incomplete and complete nonstationary artificial accelerograms, deterministic and probabilistic seismic hazard analysis, generation and processing of multicomponential response spectras, analysis of design parameters, processing of pushover curves and surfaces, calculation based on hybrid incremental nonlinear static-dynamic analysis, target displacement analysis, analysis and scaling of response spectras and analysis of target displacement envelope. For four considered methods for analysis of system performances: nonlinear static pushover analysis (NSPA), incremental nonlinear dynamic analysis (INDA), incremental dynamic analysis (IDA) and hybrid incremental nonlinear static-dynamic analysis (HINSDA), flow charts are shown.

Soil-Pile-Pier Interaction

Cosic M., Folic B., Folic R., Susic N.: Soil-Pile-Pier Interaction (presentation)

The purpose of this presentation is to show the methodology for performance-based seismic evaluation of soil-pile-bridge pier interaction using the incremental nonlinear dynamic analysis (INDA). The INDA analysis was post processed separately for the pier and for the pile, so that the constructed PGA=f(DR) curves are in the capacitive domain. For these curves the authors identified the IO, CP and GI performance levels, while the regression analyses were conducted based on the specific DR and PGA parameters. Fragility curves were constructed based on the solutions of regression analysis and the probability theory of log-normal distribution. Based on the results of fragility analysis, reliability curves were also constructed.

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