Analysis of Nonlinear Static-Dynamic Deformation of Reinforced Concrete Frames in out-of-Limit States

Постановка задачи. Приводятся расчетная модель, алгоритм расчетного анализа и результаты расчета нелинейного статико-динамического деформирования железобетонных рам в запредельных состояниях, вызванных внезапным удалением одной из несущих конструкций. Результаты. Для создания численной модели режима статико-динамического нагружения конструктивной системы использован программный комплекс LS-DYNA с применением детальной 3Д-модели, реализующей явный метод конечных элементов. При проведении расчетного анализа были приняты физико-механические характеристики деформирования материалов в трех вариантах: полученные по опытным данным Г. А. Гениева, по опытным данным Н. В. Федоровой, М. Д. Медянкина при статико-динамическом одноосном режиме испытаний ограниченного числа стандартных образцов призм и по СП 385.1325800.2018. Выводы. Численным анализом статико-динамического деформирования железобетонной рамно-стержневой системы каркаса многоэтажного здания установлено, что дифференцированный учет количественного значения модуля вязкости бетона и соответственно времени и уровня статико-динамического догружения конструкции позволяет более строго определять критерии особого предельного состояния элементов железобетонных конструктивных систем зданий и сооружений. Statement of the problem. The article presents a computational model, an algorithm for computational analysis and the results of calculating the nonlinear static-dynamic deformation of reinforced concrete frames in out-of-limit states caused by the sudden removal of one of the supporting structures. Results. To design a numerical model of the static-dynamic loading mode of a structural system, the LS-DYNA software package was used that makes use of a detailed 3D model implementing an explicit finite element method. During the computational analysis, the physical and mechanical characteristics of the deformation of materials were taken in three variants: those obtained based on the experimental data by G. A. Geniev, the experimental data by N. V. Fedorova and M. D. Medyankin under the static-dynamic uniaxial testing mode of a limited number of standard samples of prisms and according to the Russian standards SP (СП) 385.1325800.2018. Conclusions. Numerical analysis of the static-dynamic deformation of the reinforced concrete frame-rod system of a multi-storey building has established that the differentiated accounting of the quantitative value of the concrete viscosity modulus and, accordingly, the time and level of static-dynamic loading of the structure allows one to identify the criteria for the special limit state of the elements of reinforced concrete structural systems of buildings and structures in a more rigid manner.

Onsite Testing for Nonlinear Analysis of an Earthquake Damaged Historical Church in Italy

Analysis and diagnosis of historical masonry buildings are frequently affected by uncertainties due to unexpected behaviors caused by cumulative damage, material decay or transformations. This research work follows a methodology in the structural analysis of the historical masonry church of San Filippo Neri in Macerata, severely damaged after the Central Italy Earthquake occurred in October 2016. The PRiSMa laboratory (Proof testing and Research in Structures and Materials) of Roma Tre University carried out an extensive onsite testing campaign, including NDT tests as sonic tomography and endoscopy, and minor destructive technique as double flat jack test, together with dynamic monitoring under ambient vibrations, to investigate the state of conservation of the building. The onsite testing results were then implemented in an accurate finite element model, which was tuned up by means of global dynamic response provided by OMA (operational modal analysis) and updated, after the sensitivity analysis, through the Douglas-Reid method. Finally, nonlinear static and dynamic analyses were performed to investigate the state of damage of the church and reduce its uncertainties. This methodology will support the design of strengthening measures to achieve a higher level of safety concerning both needs of protection and conservation, thereby avoiding ineffectual or amiss interventions.

Selection of the Optimal Structural Design of a Spar Composite Wing

This paper describes a method for optimizing the design of a spar-type composite aircraft wing structure based on multi-criterion approach. Two types of composite wing structures such as two-spar and three-spar ones were considered. The optimal design of a wing frame was determined by the Pareto method basing on three criteria: minimal weight, minimal wing deflection, maximal safety factor and minimal weight. Positions of wing frame parts, i.e. spars and ribs, were considered as optimization parameters. As a result, an optimal design of a composite spar-type wing was proposed. All the calculations necessary to select the optimal structural and design of the spar composite wing were performed using nonlinear static finite element analysis in the FEMAP with NX Nastran software package.

Study on the Development of Seismic Fragility of Steel SMRF

Vulnerability assessment of the structure is the most important and wide area of research which requires more input from the engineers and seismologist. The seismic vulnerability assessment of the structure can be evaluated by developing Fragility curves. Fragility curves shows the conditional probability of the structure exceeding the particular performance limit of the given damage state during strong ground motions. Fragility curves can be developed for different parameters like spectral displacement (Sd), spectral acceleration (Sa) Peak ground acceleration (PGA) , Inter storey drift ratio (IDR) etc. This paper describes about the different methods used in deriving the Fragility curves like conventional methods, Nonlinear Dynamic analysis methods and Nonlinear Static analysis methods. Also the fragility analysis of 5 Storied Steel Moment Resisting Frame (SMRF) has been carried out based on the parameters suggested by HAZUS M.H 2.1. Nonlinear static pushover analysis of the frame has been carried out in ETABS2016. Fragility curves are developed based on the pushover analysis results. The damage states defined as per HAZUS are Slight damage (SD), Moderate damage (MD) Extensive damage (ED) and Complete damage (CD). After carrying out the fragility analysis for the steel SMRF, it has been found out that, as the spectral displacement increases probability of failure for the slight damage of the structure is very high and the probability of failure for the complete damage is very low. Hence the probability of failure of the structure reduces from slight damage to complete damage. Keywords: Fragility curves, vulnerability assessment, Nonlinear static pushover analysis, HAZUS M.H 2.1.