scholarly journals Optimal configuration of RC frames considering ultimate and serviceability limit state constraints

2021 ◽  
Vol 14 (2) ◽  
Author(s):  
Marcela Alejandra Juliani ◽  
Wellison José de Santana Gomes
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Optimization Problems ◽  
Limit State ◽  
Physical Nonlinearity ◽  
Ultimate Limit State ◽  
Limit States ◽  
Serviceability Limit State ◽  
Rc Frames ◽  
The Cost

Abstract Most current structural design codes are based on the concept of limit states, that is, when a structure fails to meet one of its purposes, it is said that it has reached its limit state. In the design of reinforced concrete structures, the Ultimate Limit State (ULS) and the Serviceability Limit State (SLS) must be checked. Therefore, this paper presents an optimization scheme for reinforced concrete plane frames, in which the objective is to minimize the cost of structures for three cases of constraints: the first is related to ULS and SLS; the second refers only to the ULS; and the third is related only to the SLS. Computational routines for checking limit states of beams and columns are implemented in MATLAB, following the requirements of the Brazilian code. Structural analyses are performed by using the MASTAN2 software, taking into account geometric nonlinearities and a simplified physical nonlinearity method. The objective function considers the cost of concrete, reinforcement and formwork, and the optimization problems are solved by genetic algorithms. Two numerical examples of frames are presented. Regarding the optimal characteristics related to each type of limit state, it is noted that the beams and columns tend to have larger and more reinforced cross sections in the case of the ULS. Even so, optimal structures related to the ULS often do not satisfy SLS and vice versa, which indicates that the optimal characteristics related to each limit state may be different. In addition, it is observed that the SLS is less restrictive than ULS.

scholarly journals Simplified Data-Driven Model for the Moment Curvature of T-Shaped RC Shear Walls

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Bin Wang ◽  
Wenzhe Cai ◽  
Qingxuan Shi
Keyword(s):  
Cross Sections ◽  
Limit State ◽  
Shear Walls ◽  
Load Ratio ◽  
Ultimate Limit State ◽  
Limit States ◽  
Displacement Ductility ◽  
And Performance ◽  
Displacement Based ◽  
Ductility Capacity

Sectional deformation quantities, such as curvature and ductility, are of prime significance in the displacement-based seismic design and performance evaluation of structural members. However, few studies on the estimates of curvatures at different limit states have been performed on asymmetric flanged walls. In this paper, a parametric study was performed for a series of T-shaped wall cross-sections based on moment-curvature analyses. By investigating the effects of the axial load ratio, reinforcement content, material properties, and geometric parameters on curvatures at the yield and ultimate limit state, we interpret the variation in curvature with different influencing factors in detail according to the changes of the neutral axis depth. Based on the regression analyses of the numerical results of 4941 T-shaped cross-sections, simple expressions to estimate the yield curvature and ultimate curvature for asymmetric flanged walls are developed, and simplified estimates of the ductility capacity including curvature ductility and displacement ductility are further deduced. By comparing with the experimental results, we verify the accuracy of the proposed formulas. Such simple expressions will be valuable for the determination of the displacement response of asymmetric flanged reinforced concrete walls.

Fatigue and Serviceability Limit State Model Basis for Assessment of Offshore Wind Energy Converters

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
S. Thöns ◽  
M. H. Faber ◽  
W. Rücker
Keyword(s):  
Wind Energy ◽  
Limit State ◽  
Sensitivity Study ◽  
Offshore Wind ◽  
Ultimate Limit State ◽  
Offshore Wind Energy ◽  
Limit States ◽  
Serviceability Limit State ◽  
State Models ◽  
Energy Converters

This paper develops the models for the structural performance of the loading and probabilistic characterization for the fatigue and the serviceability limit states for the support structure of offshore wind energy converters. These models and a sensitivity study are part of a risk based assessment and monitoring framework and will be applied for establishing the “as designed and constructed” reliability as prior information for the assessment and the design of monitoring systems. The constitutive physical equations are introduced in combination with the fatigue and serviceability limit state requirements as the starting point for the development of the structural performance and loading models. With these models introduced in detail, several modeling aspects for both limit states are analyzed. This includes analyses of the influence on the hot spot stresses by applying a contact formulation for the pile guide brace connection and the application of a finite element formulation using solid elements. Further, the comparison of the natural frequencies of a discrete rotor model with a continuous rotor model is documented. To account for uncertainties associated with the structural and loading models, a probabilistic model is derived on the basis of literature review and measurement data from a prototype Multibrid M5000 support structure. The sensitivity study is based on the calculation of a nonlinear coefficient of correlation in conjunction with predetermined designs of experiments. This is conducted by a systematic analysis of the influence of the random variables on limit state responses and hence on the structural reliability. Integrating the analyses and sensitivity studies of the fatigue and serviceability limit state models developed in this paper as well as the ultimate limit state models in Thöns et al. (“Ultimate Limit State Model Basis for Assessment of Offshore Wind Energy Converters,” ASME J. Offshore Mech. Arct. Eng.), the model basis for the assessment is completed. The process of establishing and analyzing such a model basis contributes to a detailed understanding of the deterministic and probabilistic characteristics of the structure and provides valuable insights in regard to the significance of available data.

scholarly journals Combined axial and flexural loads in short reinforced concrete columns in fire: ultimate limit state curves using 500 °C isotherm method

2018 ◽  
Vol 11 (1) ◽  
pp. 163-182
Author(s):  
J. S. SUAZNABAR ◽  
V. P. SILVA
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Limit State ◽  
Concrete Columns ◽  
Ultimate Limit State ◽  
Reinforced Concrete Columns ◽  
The Cross ◽  
In Fire ◽  
Ultimate Limit

Abstract Ultimate limit state curves of short reinforced concrete columns in fire situation are going to be presented in this paper. The authors created a code developed in Matlab. It makes a discretization of the cross sections of the columns and calculates the equilibrium integrals of them. The curves were plotted with the code considering the 500 °C isotherm method.

scholarly journals Probabilistic Approach to Limit States of a Steel Dome

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5528
Author(s):  
Paweł Zabojszcza ◽  
Urszula Radoń ◽  
Waldemar Szaniec
Keyword(s):  
Normal Distribution ◽  
Limit State ◽  
Probabilistic Approach ◽  
Random Variables ◽  
Structural Safety ◽  
Ultimate Limit State ◽  
Limit States ◽  
Serviceability Limit State ◽  
First Case ◽  
Ultimate Limit

In this paper, Numpress Explore software, developed at the Institute of Fundamental Technological Research of the Polish Academy of Sciences (IPPT PAN), was used to conduct reliability analyses. For static-strength calculations, the MES3D module, designed by the authors, was employed. Ultimate limit state was defined as condition of non-exceedance of the capacity value, resulting from the stability criterion of the bent and compressed element. The serviceability limit state was defined as the condition of non-exceedance of allowable vertical displacement. The above conditions constitute implicit forms of random variable functions; therefore, it was necessary to build an interface between the Numpress Explore and MES3D programs. In the study, a comparative analysis of two cases was carried out. As regards the first case, all adopted random variables had a normal distribution. The second case involved a more accurate description of the quantities mentioned. A normal distribution can be adopted for the description of, e.g., the randomness in the location of the structure nodes, and also the randomness of the multiplier of permanent loads. In actual systems, the distribution of certain loads deviates substantially from the Gaussian distribution. Consequently, adopting the assumption that the loads have a normal distribution can lead to gross errors in the assessment of structural safety. The distribution of loads resulting from atmospheric conditions is decidedly non-Gaussian in character. The Gumbel distribution was used in this study to describe snow and wind loads. The modulus of elasticity and cross-sectional area were described by means of a log-normal distribution. The adopted random variables were independent. Additionally, based on an analysis of the elasticity index, the random variables most affect the failure probability in the ultimate limit state and serviceability limit state were estimated.

Software for Design and Assessment of Rotationally Symmetrically Loaded Reinforced Concrete Slabs in the Shape of Circle or Ring

2015 ◽  
Vol 749 ◽  
pp. 368-372
Author(s):  
Jana Vaskova ◽  
Pavlina Matečková
Keyword(s):  
Reinforced Concrete ◽  
Limit State ◽  
Design Principles ◽  
Tangential Direction ◽  
Concrete Slabs ◽  
Ultimate Limit State ◽  
Serviceability Limit State ◽  
Reinforced Concrete Slabs ◽  
The Subject ◽  
Ultimate Limit

The subject of this paper is an universal software for reinforced concrete annular and circular slabs reinforced in the radial and tangential direction. Such slabs are used for roof and ceiling structures of buildings. The software can be used for design and assessment of rotationally symmetrically loaded annular and circular reinforced concrete slabs with arbitrary supports and span. Based on user's choice, the software proposes solutions to not only meet all the design principles, but especially ultimate limit state and serviceability limit state.

Towards a Capacity-Design Assessment Procedure for Reinforced Concrete Frames

1991 ◽  
Vol 7 (3) ◽  
pp. 413-437 ◽  
Author(s):  
M. J. Nigel Priestley ◽  
G. Michele Calvi
Keyword(s):  
Reinforced Concrete ◽  
Limit State ◽  
Elastic Response ◽  
Collapse Mechanism ◽  
Ultimate Limit State ◽  
Assessment Procedure ◽  
Capacity Design ◽  
Design Assessment ◽  
Probability Of Exceedance ◽  
Serviceability Limit State

A two-level seismic assessment procedure for reinforced concrete frame buildings is presented. The intent of the procedure is to determine the risk, in terms of annual probability of exceedance, associated with two limit states, namely a serviceability limit state and a survival, or ultimate, limit state. The serviceability limit state is determined by elastic response calculation, but the survival limit state analysis attempts to identify the strength and ductility of the critical collapse mechanism, and hence its probability of exceedance by comparison with reference spectra. The basis for identifying the critical collapse mechanism is a modified form of capacity design principles which allows local element failure provided overall structural integrity is not jeopardized.

Combined flexure and torsion of I-shaped steel beams

1989 ◽  
Vol 16 (2) ◽  
pp. 124-139 ◽  
Author(s):  
Robert G. Driver ◽  
D. J. Laurie Kennedy
Keyword(s):  
Limit State ◽  
Bending Moment ◽  
Phase Behaviour ◽  
Inelastic Interaction ◽  
Steel Beams ◽  
Ultimate Limit State ◽  
Second Phase ◽  
Design Standards ◽  
Limit States ◽  
Interaction Diagram

Design standards provide little information for the design of I-shaped steel beams not loaded through the shear centre and therefore subjected to combined flexure and torsion. In particular, methods for determining the ultimate capacity, as is required in limit states design standards, are not presented. The literature on elastic analysis is extensive, but only limited experimental and analytical work has been conducted in the inelastic region. No comprehensive design procedures, applicable to limit states design standards, have been developed.From four tests conducted on cantilever beams, with varying moment–torque ratios, it is established that the torsional behaviour has two distinct phases, with the second dominated by second-order geometric effects. This second phase is nonutilizable because the added torsional restraint developed is path dependent and, if deflections had been restricted, would not have been significant. Based on the first-phase behaviour, a normal and shearing stress distribution on the cross section is proposed. From this, a moment–torque ultimate strength interaction diagram is developed, applicable to a number of different end and loading conditions. This ultimate limit state interaction diagram and serviceability limit states, based on first yield and on distortion limitations, provide a comprehensive design approach for these members. Key words: beams, bending moment, flexure, inelastic, interaction diagram, I-shaped, limit states, serviceability, steel, torsion, torque, ultimate.

Anchor rod forces and maximum bending moments in sheet pile walls using the factored strength approach

1996 ◽  
Vol 33 (5) ◽  
pp. 815-821 ◽  
Author(s):  
A B Schriver ◽  
A J Valsangkar
Keyword(s):  
Water Pressure ◽  
Limit State ◽  
Bending Moment ◽  
Ultimate Limit State ◽  
Sheet Pile ◽  
Limit States ◽  
Working Stress ◽  
Geotechnical Design ◽  
Ultimate Limit State Design ◽  
Sheet Pile Wall

Recently, the limit states approach using factored strength has been recommended in geotechnical design. Some recent research has indicated that the application of limit states design using recommended load and strength factors leads to conservative designs compared with the conventional methods. In this study the influence of sheet pile wall geometry, type of water pressure distribution, and different methods of analysis on the maximum bending moment and achor rod force are presented. Recommendations are made to make the factored strength design compatible with conventional design. Key words: factored strength, working stress design, ultimate limit state design, anchored sheet pile wall, bending moment, anchor rod force.

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.

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