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.

Evaluation of IACS Common Structural Rules in Terms of Ultimate Limit State Design and Assessment of Ship Structures

2007 ◽  
Author(s):  
Jeom Kee Paik ◽  
Bong Ju Kim ◽  
Jung Kwan Seo
Keyword(s):  
Limit State ◽  
Bending Moment ◽  
Ultimate Limit State ◽  
Stiffened Plate ◽  
Plate Structures ◽  
Hull Girder ◽  
Structural Rules ◽  
Out Of Plane ◽  
Common Structural Rules ◽  
Ultimate Limit

The aim of the present paper is to evaluate the ultimate limit state performance of an AFRAMAX-class hypothetical double hull oil tanker structure designed by IACS CSR (Common Structural Rules) method, compared with the same-class/type tanker structure designed by IACS pre-CSR method. The ultimate strengths of stiffened plate structures in deck and bottom parts under combined in-plane and out-of-plane actions, and hull girder against vertical bending moment, are computed for the two designs, and the resulting computations are compared. ALPS/ULSAP program is used for the ultimate limit state assessment of stiffened plate structures, while ALPS/HULL program is employed for the progressive hull collapse analysis. ANSYS nonlinear FEA method, which uses more refined technology, is also used for the same purpose. The insights and developments obtained from the present study are addressed.

DESIGN OF BOLTED CONNECTIONS SUBJECT TO TORSION AND SHEAR IN THE ULTIMATE LIMIT STRESS STATE

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Mohamed S. Abu-Yosef ◽  
Ezzeldin Y. Sayed-Ahmed ◽  
Emam A. Soliman
Keyword(s):  
Failure Modes ◽  
Focal Point ◽  
Design Method ◽  
Limit State ◽  
Bending Moment ◽  
Steel Structures ◽  
Ultimate Limit State ◽  
Shear Forces ◽  
Limit States ◽  
Ultimate Limit

Steel connections transferring axial and shear forces in addition to bending moment and/or torsional moment are widely used in steel structures. Thus, design of such eccentric connections has become the focal point of any researches. Nonetheless, behavior of eccentric connections subjected to shear forces and torsion in the ultimate limit state is still ambiguous. Most design codes of practice still conservatively use the common elastic analysis for design of the said connections even in the ultimate limit states. Yet, there are some exceptions such as the design method proposed by CAN/CSA-S16-14 which gives tabulated design aid for the ultimate limit state design of these connections based on an empirical equation that is derived for ¾ inch diameter A325 bearing type bolts and A36 steel plates. It was argued that results can also be used with a margin of error for other grade bolts of different sizes and steel of other grades. As such, in this paper, the performance of bolted connection subject to shear and torsion is experimentally investigated. The behavior, failure modes and factors affecting both are scrutinized. Twelve connections subject to shear and torsion with different bolts configurations and diameters are experimentally tested to failure. The accuracy of the currently available design equations proposed is compared to the outcomes of these tests.

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.

Ultimate Limit State Performance of 170k Bulk Carrier Structures: Pre-CSR versus CSR Designs

2009 ◽  
Vol 46 (03) ◽  
pp. 174-182
Author(s):  
Jeom kee Paik ◽  
Jin Young Kim ◽  
Min Soo Kim
Keyword(s):  
Limit State ◽  
Bending Moment ◽  
Ultimate Limit State ◽  
Stiffened Plate ◽  
Bulk Carrier ◽  
Plate Structures ◽  
Structural Rules ◽  
Similar Class ◽  
Common Structural Rules ◽  
Ultimate Limit

The objective of the present paper is to evaluate the ultimate limit state (ULS) performance of 170k bulk carrier structures designed by the IACS common structural rules (CSR) method, compared with the similar-class/type bulk carrier structure designed by the IACS pre-CSR method. The ultimate strengths of stiffened plate structures in deck, side, and bottom parts, and hull girders against vertical bending moment, are computed for the two designs, and the resulting computations are compared. ALPS/ULSAP program is used for the ultimate limit state assessment of stiffened plate structures, and ALPS/HULL program is employed for the progressive hull collapse analysis. The insights and developments obtained from the present study are documented.

Calibration of resistance factors for bearing resistance design of shallow foundations under seismic and wind loading

2021 ◽  
Author(s):  
Pengpeng He ◽  
Gordon A. Fenton ◽  
D.V. Griffiths
Keyword(s):  
Limit State ◽  
Shallow Foundations ◽  
Soil Conditions ◽  
Dynamic Resistance ◽  
Ultimate Limit State ◽  
Loading Conditions ◽  
Foundation Design ◽  
Resistance Factors ◽  
Ultimate Limit ◽  
Undrained Soil

Although the geotechnical resistance 19 factors at ultimate limit state used for dynamic loading conditions should be different from those for static loading conditions, most current structural and geotechnical design codes do not specifically provide dynamic resistance factors. In this paper, the ultimate limit state reliability analysis of individual shallow foundations for drained and undrained soil conditions under seismic (pseudo-dynamic) and wind loads using the Random Finite Element Method is carried out using the provisions of the National Building Code of Canada. The geotechnical resistance factors required to achieve target maximum lifetime failure probabilities are estimated for a few major Canadian cities. The results indicate that the failure probability for drained soil conditions is slightly greater than that for undrained soil conditions. In addition, the results suggest that the dynamic resistance factors for foundation bearing capacity design at ULS are lower than those for static foundation design specified by the code. The current analysis can be used to guide the calibration of these geotechnical resistance factors.

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.

An Automated Approach for Optimizing Monopile Foundations for Offshore Wind Turbines for Serviceability and Ultimate Limit States Design

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
James P. Doherty ◽  
Barry M. Lehane
Keyword(s):  
Limit State ◽  
Offshore Wind ◽  
Ultimate Limit State ◽  
Trial And Error ◽  
Limit States ◽  
Foundation Design ◽  
Offshore Wind Turbines ◽  
Economical Design ◽  
Limit State Criteria ◽  
Ultimate Limit

Pile foundation design is conventionally conducted using a process of trial and error, where the dimensions of a pile are estimated and the performance is computed and compared with design criteria. The dimensions are varied and the process is repeated in order to converge to a safe and economical design. In this paper, this time-consuming and labor intensive process is replaced with an automated approach using the example case of an offshore monopile supporting a wind turbine. The optimum length and diameter of the monopile are determined with the aim of minimizing the pile weight while satisfying both serviceability and ultimate limit state criteria. The approach handles general soil and loading conditions and includes an ability to incorporate cyclic loading.

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.

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