scholarly journals ANALYSIS OF ULTIMATE LIMIT STATE OF SPHERICAL SHELL / SFERINIO KEVALO SAUGOS RIBINIO BŪVIO ANALIZĖ

2013 ◽  
Vol 5 (2) ◽  
pp. 69-75 ◽  
Author(s):  
Tomas Ulitinas ◽  
Stanislovas Kalanta ◽  
Juozas Atkočiūnas
Keyword(s):  
Mathematical Model ◽  
Spherical Shell ◽  
Limit State ◽  
Limit Load ◽  
Mathematical Programming Problem ◽  
Ultimate Limit State ◽  
Axial Forces ◽  
Internal Forces ◽  
The Mathematical Model ◽  
Ultimate Limit

The article presents ultimate limit state analysis and limit load problem of a symmetrically loaded flat spherical shell. Physical parameters (modulus of elasticity, Poisson's ratio), shape, dimensions of the construction, load and its adding position and orientation are known. The mathematical model of the problem is formulated by technically computing the shells theory. The bending moments and axial forces are described by the second and the first degree polynomials. The element's differential statics equations, describing the balance between the internal and external forces, are replaced with algebraic equilibrium equations presented by the Bubnov-Galerkin method. The mathematical model and the calculation algorithm of the internal forces and displacements in the shell analysis problem are developed and formulated using statics and geometry equations. The construction is divided into countable elements, which are composed into a computational network. It is necessary to take into account not only the geometric shape of the structure, but also the distribution of load when the computational network of spherical shell is composed. The spherical shells are considered in the cylindrical (ρ,φ,z) co-ordinate system. The begining of the coordinate system is the construction center. The internal forces and the displacements are independent of j coordinates, when the load is symmetrical, so it is enough to investigate only one radial of the shell. The circular shell elements are connected by boundary nodes in the main nodes of the discrete model. The second-order circular element with three nodal (calculation) points in the one radial is used for discretization (Fig. 1). The mathematical model of elastic-plastic problem is a nonlinear mathematical programming problem. Elastic internal forces S e and displacements u e are calculated by mathematical model (10)–(11). The values of internal forces and displacement of the main nodes are shown in Fig. 5. The values of nodal displacements are given up to the factor pR 0 / E, while the values of the internal forces are given up to the factor pR 0. The problem of limit load parameter p is calculated by mathematical model (15)–(16). The strength conditions are tested at all elements nodes. The value of limit load is p=2, 568 N 0/R 0. The Internal forces diagrams are shown Fig. 7. They are a corresponded plastic decomposition of flat spherical shell. Santrauka Darbe pateikiama simetriškai apkrauto lėkšto sferinio kevalo saugos ribinio būvio analizė. Konstrukcijos fizikiniai parametrai, forma, matmenys, apkrova ir jos pridėjimo vieta ir kryptis yra žinomi. Nagrinėjamas tamprusis ir idealiai tamprus plastinis kevalas, pasitelkiant ekstreminį energetinį principą randami tikrieji įtempių ir deformacijų būviai. Tampraus būvio analizės uždavinio matematinis modelis formuluojamas taikant virtualių jėgų principą, o ribinės apkrovos nustatymo uždavinio matematinis modelis formuluojamas kaip netiesinis matematinio programavimo uždavinys.

scholarly journals Secondary Moments due to Prestressing with Different Bond at the Ultimate Limit State

2018 ◽  
Vol 26 (1) ◽  
pp. 10-18
Author(s):  
Jaroslav Halvoník ◽  
Peter Pažma ◽  
Radoslav Vida
Keyword(s):  
Limit State ◽  
Plastic Hinge ◽  
Ultimate Limit State ◽  
Critical Cross Section ◽  
Structural System ◽  
Secondary Effects ◽  
Limit States ◽  
Internal Forces ◽  
Ultimate Limit ◽  
Kinematic Mechanism

Abstract Secondary effects of prestressing develop in statically indeterminate structures (e.g., continuous beams) due to the restraint of deformations imposed by hyperstatic restraints. These effects may significantly influence internal forces and stresses in prestressed structures. Secondary effects are influenced by the redundancy of a structural system, which raises the question of whether they will remain constant after a change in the structural system, e.g., due to the development of plastic hinge(s) in a critical cross-section(s) or after the development of a kinematic mechanism, or if they will disappear when the structure changes into a sequence of simply supported beams. The paper deals with an investigation of the behavior of continuous post-tensioned beams subjected to an ultimate load with significant secondary effects from prestressing. A total of 6 two-span beams prestressed by tendons with different bonds were tested in a laboratory with a load that changed their structural system into a kinematic mechanism. The internal forces and secondary effects of the prestressing were controlled through measurements of the reactions in all the supports. The results revealed that the secondary effects remained as a permanent part of the action on the experimental beams, even after the development of the kinematic mechanism. The results obtained confirmed that secondary effects should be included in all combinations of actions for verifications of ultimate limit states (ULS).

scholarly journals Non-deterministic Approach for Reliability Evaluation of Steel Portal Frame

2019 ◽  
Vol 5 (8) ◽  
pp. 1684-1697
Author(s):  
Hawraa Qasim Jebur ◽  
Salah Rohaima Al-Zaidee
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Structural Reliability ◽  
Limit State ◽  
Computational Cost ◽  
Probability Of Failure ◽  
Ultimate Limit State ◽  
Axial Forces ◽  
Portal Frame ◽  
Ultimate Limit

In recent years, more researches on structural reliability theory and methods have been carried out. In this study, a portal steel frame is considered. The reliability analysis for the frame is represented by the probability of failure, P_f, and the reliability index, β, that can be predicted based on the failure of the girders and columns. The probability of failure can be estimated dependent on the probability density function of two random variables, namely Capacity R, and Demand Q. The Monte Carlo simulation approach has been employed to consider the uncertainty the parameters of R, and Q. Matlab functions have been adopted to generate pseudo-random number for considered parameters. Although the Monte Carlo method is active and is widely used in reliability research, it has a disadvantage which represented by the requirement of large sample sizes to estimate the small probabilities of failure. This is leading to computational cost and time. Therefore, an Approximated Monte Carlo simulation method has been adopted for this issue. In this study, four performances have been considered include the serviceability deflection limit state, ultimate limit state for girder, ultimate limit state for the columns, and elastic stability. As the portal frame is a statically indeterminate structure, therefore bending moments, and axial forces cannot be determined based on static alone. A finite element parametric model has been prepared using Abaqus to deal with this aspect. The statistical analysis for the results samples show that all response data have lognormal distribution except of elastic critical buckling load which has a normal distribution.

scholarly journals Combined rupture mechanisms in shallow foundations

2018 ◽  
Vol 55 (6) ◽  
pp. 829-838 ◽  
Author(s):  
A. Gajo ◽  
C.C. Smith
Keyword(s):  
Limit State ◽  
Load Condition ◽  
Bending Moment ◽  
Limit Load ◽  
Shallow Foundation ◽  
Ultimate Limit State ◽  
Rigid Plastic ◽  
Foundation Design ◽  
Full Analysis ◽  
Ultimate Limit

Conventional ultimate limit state (ULS) shallow foundation design is typically based on a simplified analysis that fails to consider the possible existence of a combined structural and geotechnical failure, which is shown here to significantly affect the limit load. Neglecting this occurrence may lead to unsafe design, whereas a full analysis can be beneficial for the dimensioning. With the emphasis on separate serviceability limit state and ULS design in modern design codes such as Eurocode 7 (EN 1997-1, 2004 edition), this paper explores unsafe loading scenarios and the benefits to be gained from a rigorous ULS design based on combined failure. For the sake of simplicity, a long foundation slab subjected to three different loading conditions is analysed using elastic, elasto-plastic, and rigid-plastic methods, and the results compared for a range of foundation strengths and stiffnesses. It is found that the limit load may be significantly influenced by plastic hinges in the structure and for each load condition it is possible to derive a curve relating ultimate load to plastic bending moment representing the ultimate limit state of the foundation.

scholarly journals NON-LINEAR ANALYSIS OF SLENDER MASONRY COLUMN SUBJECTED TO BIAXIAL BENDING

2021 ◽  
Vol 61 (2) ◽  
pp. 391-405
Author(s):  
Marek Vokál ◽  
Michal Drahorád
Keyword(s):  
Numerical Study ◽  
Limit State ◽  
Ultimate Limit State ◽  
Beam Model ◽  
Bending Moments ◽  
Biaxial Bending ◽  
Rigid Plastic ◽  
Internal Forces ◽  
Ultimate Limit ◽  
Current Code

The article deals with a method for analysing slender masonry columns. The proposed method uses material and geometric non-linearity. Various stress-strain diagrams can be used: linear, linear-plastic, parabolic-plastic, two various parabolic and rigid-plastic. In all cases, the tensile strength is neglected. The method can be used for analysing the column in accordance with Eurocodes in two ways: SLS (serviceability limit state) and ULS (ultimate limit state). The internal forces are calculated on a general beam model, with imperfections in both directions, which result in two bending moments in two perpendicular planes – biaxial bending. This case is not covered by the current code – Eurocode, even though all columns are more or less loaded in both directions. In this numerical study, using Matlab software, an algorithm was developed for modelling a real 3D case. The results of this study are also compared to the results of laboratory tests of masonry columns.

Combined Reinforced Concrete Columns Strengthening with Steel Clipping and Concrete Surfacing

2021 ◽  
pp. 11-22
Author(s):  
Ю. Г. Москалькова ◽  
С. В. Данилов ◽  
В. А. Ржевуцкая
Keyword(s):  
Reinforced Concrete ◽  
Load Transfer ◽  
Limit State ◽  
Concrete Columns ◽  
Ultimate Limit State ◽  
Concrete Core ◽  
Reinforced Concrete Columns ◽  
Entire Height ◽  
Complex Structural ◽  
Ultimate Limit

Постановка задачи. Исследуется метод усиления железобетонных колонн устройством стальной обоймы с обетонированием, который позволяет восстанавливать эксплуатационные показатели колонн, имеющих значительные дефекты и повреждения. Предпосылкой настоящих исследований явилось предположение о том, что усиление стальной обоймой с обетонированием является эффективным способом повышения несущей способности железобетонных колонн, причем вариант приложения нагрузки - только на бетонное ядро или ко всему сечению - существенно на эффективность усиления не влияет. В связи с этим целью исследования является определение необходимости устройства стального оголовка и включения в работу ветвей стальной обоймы при условии обетонирования стержня колонны по всей высоте. Результаты и выводы. Рациональным признан способ передачи нагрузки только на бетонное ядро усиленных колонн, поскольку устройство оголовка стальной обоймы требует применения сложных конструктивно-технологических решений, но при этом дополнительно увеличивает несущую способность незначительно (согласно проведенным исследованиям менее чем на 10 %). Ввиду отсутствия необходимости устройства конструкций стального оголовка снижаются трудоемкость и сроки производства работ по усилению колонн. Statement of the problem. The method of strengthening reinforced concrete columns with a steel clipping and the concrete surfacing is investigated. This method allows one to repair the columns with significant defects and damage. The prerequisite for this study was the assumption of strengthening with a steel clipping and the concrete surfacing is an effective way to increase the ultimate limit state of reinforced concrete columns, furthermore, the option of applying the load (only to the concrete core or to the entire section) does not significantly affect the strengthening effectiveness. In this regard, the purpose of the investigation was to identify the need to include the steel jacketing in the work, on the condition the column is coated with concrete along with the entire height. Results and conclusions. The load transfer method only to the concrete core of the strengthened columns is recognized as rational since the device of the steel clipping head requires the use of complex structural and technological solutions, but at the same time additionally increases the ultimate limit state insignificantly (according to the studies by less than 10 %). Due to the absence of the need to establish structures of the steel jacketing head, the labor intensiveness and terms of work production on strengthening the columns are reduced.

Application potential of textile reinforcement in concrete construction for infrastructure buildings: environmental performance and availability

2021 ◽  
Author(s):  
Sara Reichenbach ◽  
Benjamin Kromoser ◽  
Philipp Preinstorfer ◽  
Tobias Huber
Keyword(s):  
High Performance ◽  
Construction Material ◽  
Limit State ◽  
Carbon Dioxide Emission ◽  
Resource Consumption ◽  
Ultimate Limit State ◽  
Textile Reinforced Concrete ◽  
Potential Applications ◽  
Application Potential ◽  
Ultimate Limit

<p>With the building industry being one of the main sources of carbon dioxide emission worldwide and concrete being the main construction material, new strategies have to be developed to reduce the carbon footprint thereof. The use of high-performance materials in structural concrete, as for example textile-reinforced concrete (TRC), seems to allow for a reduction of the resource consumption and the carbon emissions. The present paper addresses potential applications of TRC examining the global warming potential (GWP) of a rail platform barrier. The resource consumption is depicted in a parametrical study in terms of the necessary component height and reinforcement area considering both the serviceability limit state (SLS) as well as the ultimate limit state (ULS). The results clearly indicate an achievable reduction of the GWP during construction when using textile reinforcement made of high-performance fibres. Furthermore, an analysis of the European market was conducted to prove the availability of this new reinforcement type. </p>

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