Lifting Pipeline Buckling under External Pressure Base on Imperfect Reason

2011 ◽  
Vol 337 ◽  
pp. 789-794
Author(s):  
Zhi Jin Zhou ◽  
Zhao Wang ◽  
Yi Min Xia
Keyword(s):  
Carrying Capacity ◽  
Deep Sea ◽  
External Pressure ◽  
Future Application ◽  
Load Carrying Capacity ◽  
Limit States ◽  
Important Conclusion ◽  
Collapse Pressure ◽  
Load Carrying ◽  
Pressure Maximum

The deep-sea pipe is an important part of mining lifting projects in the ocean floor. The uniqueness of environment conditions and design needs to determine the unforeseeable risks and challenges during the laying of pipeline. Based on extensive studies of loads acted on the pipeline and corresponding possible limit states for each installation method, a series of investigations on load-carrying capacity and buckling response of pipes under different loading combinations and various types defects (such as uniform ovalities)were carried out. In these calculations, the collapse pressure has been associated with the pressure maximum of a uniformly deforming long pipe. In experiments in a stiff pressure lifting pipelines, collapse is always localized as shown in Figures 3 and 4.However,because pipe’s localization takes place after the pressure maximum, the collapse pressure yielded by the 2-D analysis suffices for most cases. Exceptions are pipes with local imperfections, in the form of dents. The adequacy of this important conclusion will be demonstrated in the future application, where such predictions are compared to experiments.

Buckling of Corroded Torispherical Shells Under External Pressure

2018 ◽  
Author(s):  
J. Błachut
Keyword(s):  
Carrying Capacity ◽  
External Pressure ◽  
Collapse Mechanism ◽  
Load Carrying Capacity ◽  
Collapse Pressure ◽  
Buckling Strength ◽  
Wall Thinning ◽  
Strength Based ◽  
Load Carrying ◽  
Bifurcation Buckling

The current paper examines the effects of corrosion induced wall thinning on buckling of domed closures onto cylindrical vessels. It is assumed that corrosion is axisymmetric and that the wall is corroded on inside, only. The ratio of corroded wall thickness, tc, to the non-corroded thickness, t, is varied between 0.10 ≤ tc/t ≤ 1.0. Both depth of corrosion and its meridional extend are varied during numerical calculations. Three modelling scenarios for placement of corrosion are considered: (i) corrosion confined to the knuckle, (ii) corrosion spanning evenly the knuckle and spherical parts, and (iii) patchtype area positioned at the apex. Numerical results indicate that the following factors influence buckling performance of the dome: (i) meridional position of corroded area, (ii) depth of corrosion itself, and (iii) meridional span of corroded wall. For example, wall thinning of 10 % over 10 % of meridional length causes almost 20 % drop in buckling strength. The largest drop of load carrying capacity is found when the corroded wall is at the knuckle/crown junction. Here it is shown that assessment of strength based on the collapse mechanism is not only wrong but dangerous. For the case of the corroded dome, the collapse pressure overestimates the load carrying capacity associated with asymmetric bifurcation buckling by 40 %.

Flexural strengthening of pre-cracked RC slabs with prestressed NSM CFRP laminates and evaluation of strain loss

2021 ◽  
pp. 136943322110105
Author(s):  
M.R. Mostakhdemin Hosseini ◽  
Salvador J.E. Dias ◽  
Joaquim A.O. Barros
Keyword(s):  
Carrying Capacity ◽  
Load Carrying Capacity ◽  
Limit States ◽  
Transfer Length ◽  
Rc Structures ◽  
Cracked Concrete ◽  
Flexural Strengthening ◽  
Cfrp Laminates ◽  
Load Carrying ◽  
Rc Slabs

The strengthening intervention of RC structures often involves already cracked concrete. To evaluate the effect of the level of damage prior to the strengthening (pre-cracks) on the behavior of the flexurally strengthened RC slabs with prestressed NSM CFRP laminates, an experimental research was carried out. Two pre-cracking levels of damage were analyzed and, for each one, three levels of prestress were tested (0%, 20% and 40%). The obtained results showed that the strengthening of damaged RC slabs with prestressed NSM CFRP laminates results in a significant increase on the load carrying capacity at serviceability limit states. Pre-cracked RC slabs strengthened with prestressed NSM CFRP laminates presented a load carrying capacity almost similar to the corresponding uncracked strengthened slabs. To determine the effective prestress level in CFRP laminates, the variation of strain over the length of the CFRP and over time was experimentally recorded. The prestress transfer length was also evaluated. The experimental results revealed that the transfer length of CFRP laminates was less than 150 mm, and the maximum value of strain loss out of transfer length (around 14%) was measured close to the cracked section of the damaged RC slabs. Significant part of strain loss in CFRP laminates occurred during 24 h after releasing the prestress load.

Reliability analysis of wood I-joists

1993 ◽  
Vol 20 (4) ◽  
pp. 564-573 ◽  
Author(s):  
R. O. Foschi ◽  
F. Z. Yao
Keyword(s):  
Reliability Analysis ◽  
Carrying Capacity ◽  
Failure Modes ◽  
Limit State ◽  
Load Carrying Capacity ◽  
Limit States ◽  
Element Analysis ◽  
Strength Limit ◽  
Reliability Method ◽  
Load Carrying

This paper presents a reliability analysis of wood I-joists for both strength and serviceability limit states. Results are obtained from a finite element analysis coupled with a first-order reliability method. For the strength limit state of load-carrying capacity, multiple failure modes are considered, each involving the interaction of several random variables. Good agreement is achieved between the test results and the theoretical prediction of variability in load-carrying capacity. Finally, a procedure is given to obtain load-sharing adjustment factors applicable to repetitive member systems such as floors and flat roofs. Key words: reliability, limit state design, wood composites, I-joist, structural analysis.

STABILITY PROBLEMS OF STEEL‐CONCRETE MEMBERS COMPOSED OF HIGH‐STRENGTH MATERIALS

2010 ◽  
Vol 16 (3) ◽  
pp. 352-362 ◽  
Author(s):  
Zdeněk Kala ◽  
Libor Puklický ◽  
Abayomi Omishore ◽  
Marcela Karmazínová ◽  
Jindřich Melcher
Keyword(s):  
Theoretical Analysis ◽  
Experimental Research ◽  
Carrying Capacity ◽  
High Strength ◽  
Statistical Characteristics ◽  
Load Carrying Capacity ◽  
Limit States ◽  
Load Carrying ◽  
Geometrical Imperfections

The presented paper deals with the stochastic analysis of the ultimate limit states of steel‐concrete building members. The load carrying capacity of steel‐concrete columns, comprising of steel profiles encased in high strength concrete, in compression is analyzed. The first part of the paper lists assumptions for the determination of the theoretical load carrying capacity of the column. Principles of elasticity and plasticity are used to determine stresses in the concrete and steel sections. Statistical characteristics of input material and geometrical imperfections are listed. Results of the theoretical analysis are then compared with results of experimental research. Statistical characteristics of obtained results of the theoretical analysis were verified using statistical characteristics obtained from experimental research. Numerical simulation LHS and Monte Carlo methods, which take into account the influences of variability of input imperfections, were employed. The influence of the utilization of the plastic reserve in the determination of the load carrying capacity of the analysed strut is shown. The influence of the initial geometric imperfections of initial strut curvature on the load carrying capacity is also presented. Santrauka Straipsnyje pateikta plienbetonio pastatu elementu didžiausiu ribiniu būkliu stochastine analize, analizuojama plienbetonio kolonu, sudarytu iš plieniniu profiliuočiu, padengtu didelio stiprio betonu, laikomoji galia gniuždant. Pirmoje straipsnio dalyje išvardytos kolonos teorines laikomosios galios nustatymo prielaidos. Tamprumo ir plastiškumo principai taikyti itempiams betono ir plieno skerspjūviuose nustatyti. Nustatytos medžiagu ir geometriniu defektu statistines charakteristikos, teorines analizes rezultatai palyginti su eksperimentiniu tyrimu rezultatais. Teorines analizes metu gautu rezultatu statistines charakteristikos patikrintos taikant iš eksperimentiniu tyrimu gautus statistinius rodiklius. Pritaikytas skaitinis modeliavimas LHS ir Monte Karlo metodais, kurie ivertina pradiniu defektu kintamumo itaka. Parodyta plastiškumo atsargos naudojimo itaka, nustatant analizuojamojo statramsčio laikomaja galia, pateikta pradinio statramsčio išlinkio pirminiu geometriniu defektu itaka laikomajai galiai.

Buckling of Barreled Shells Subjected to External Hydrostatic Pressure

2000 ◽  
Vol 123 (2) ◽  
pp. 232-239 ◽  
Author(s):  
J. Błachut ◽  
P. Wang
Keyword(s):  
Carrying Capacity ◽  
Ultimate Load ◽  
Load Capacity ◽  
External Pressure ◽  
Load Carrying Capacity ◽  
External Hydrostatic Pressure ◽  
Buckling Loads ◽  
Load Carrying ◽  
Initial Geometric Imperfections ◽  
Steel Cylindrical Shell

The paper considers barreling of a mild steel cylindrical shell as a way of improving its load carrying capacity when subjected to static external pressure. Numerical results show that the load carrying capacity can be increased from 1.4 to 40 times above the load capacity of mass equivalent cylinders. The effect of end boundary conditions on the ultimate load is examined together with sensitivity of buckling loads to initial geometric imperfections.

Actual Effects of Local Buckling of Thin-Walled Metal Roof Decking: Control Experimental Verification Performed during Structure Realization

2013 ◽  
Vol 368-370 ◽  
pp. 1503-1506
Author(s):  
Marcela Karmazínová ◽  
Jindrich Melcher
Keyword(s):  
Experimental Verification ◽  
Carrying Capacity ◽  
Failure Process ◽  
Local Buckling ◽  
Load Carrying Capacity ◽  
Limit States ◽  
Loading Test ◽  
Actual Behaviour ◽  
Load Carrying ◽  
Thin Walled

Experimental verification of structural members can be the necessary part of the structural design of load-carrying civil structures, mainly in the period of last two decades. In some cases, the knowledge obtained from the tests is the sole source of the reliable information about actual behaviour of structural member in strain and failure process and about its objective load-carrying capacity. The paper is specifically aimed at the control experimental verification of roof decking based on thin-walled metal profiled sheets. Loading test has been performed during structure erection, as additional resource for the verification of actual behaviour and objective load-carrying capacity and for the confirmation or refinement of static design assumptions and results, within the ultimate and serviceability limit states. The subject of the control experimental verification was roof decking composed of thin-walled metal cassettes with thermal insulation at its upper side, used for the university lecture room roofing.

An Assessment on the Plastic Capacity of Pipe-in-Pipe Systems Under Damage Progression Effect

2021 ◽  
Vol 88 (4) ◽  
Author(s):  
Farhad Davaripour ◽  
Bruce W.T. Quinton ◽  
Kenton Pike
Keyword(s):  
Carrying Capacity ◽  
Phase 1 ◽  
Lateral Load ◽  
External Pressure ◽  
Combined Loading ◽  
Load Carrying Capacity ◽  
Plastic Damage ◽  
Damage Progression ◽  
Structural Resistance ◽  
Load Carrying

Abstract In recent years, pipe-in-pipe (PiP) systems have been employed in an increasing number of subsea projects. According to the previous studies, the external pressure required to develop the initial local buckle on the PiP system is significantly higher than the pressure required to propagate the buckle along the system. In this respect, it is reasonable to investigate a novel topic where the propagation of buckle is induced by a lateral interference load instead of external pressure (e.g., diagonal fishing gear impact). On this subject, the recent studies showed the progression of plastic damage along a single-walled pipe, which is induced by a lateral load, could significantly lower the load-carrying capacity of the pipe. The present study investigates this finding for a PiP solution under a two-phase loading condition: in phase 1, the PiP solution is subject to 75 mm perpendicular indentation, and in phase 2, the resulting plastic damage in phase 1 is translated and induced longitudinally along with the PiP system. Furthermore, using finite element analyses, the effect of combined loading (axial and lateral load) on the load-carrying capacity of the PiP specimen is investigated. The test results show that upon the initiation of damage progression, the load-carrying capacity of the PiP specimen (against the lateral indentation) declines by 10%. Also, the numerical results show that the structural resistance of a PiP specimen against a lateral indentation drops significantly when the inner pipe is subject to axial compression.

scholarly journals Theoretical Study and Application of the Reinforcement of Prestressed Concrete Cylinder Pipes with External Prestressed Steel Strands

2019 ◽  
Vol 9 (24) ◽  
pp. 5532 ◽  
Author(s):  
Lijun Zhao ◽  
Tiesheng Dou ◽  
Bingqing Cheng ◽  
Shifa Xia ◽  
Jinxin Yang ◽  
...  
Keyword(s):  
Prestressed Concrete ◽  
Carrying Capacity ◽  
Load Carrying Capacity ◽  
Original Design ◽  
Limit States ◽  
Prestress Loss ◽  
Theoretical Derivation ◽  
Concrete Core ◽  
Concrete Cylinder ◽  
Load Carrying

Prestressed concrete cylinder pipes (PCCPs) can suffer from prestress loss caused by wire-breakage, leading to a reduction in load-carrying capacity or a rupture accident. Reinforcement of PCCPs with external prestressed steel strands is an effective way to enhance a deteriorating pipe’s ability to withstand the design load. One of the principal advantages of this reinforcement is that there is no need to drain the pipeline. A theoretical derivation is performed, and this tentative design method could be used to determine the area of prestressed steel strands and the corresponding center spacing in terms of prestress loss. The prestress losses of strands are refined and the normal stress between the strands and the pipe wall are assumed to be distributed as a trigonometric function instead of uniformly. This derivation configures the prestress of steel strands to meet the requirements of ultimate limit states, serviceability limit states, and quasi-permanent limit states, considering the tensile strength of the concrete core and the mortar coating, respectively. This theory was applied to the reinforcement design of a PCCP with broken wires (with a diameter of 2000 mm), and a prototype test is carried out to verify the effect of the reinforcement. The load-carrying capacity of the deteriorating PCCPs after reinforcement reached that of the original design level. The research presented in this paper could provide technical recommendations for the application of the reinforcement of PCCPs with external prestressed steel strands.

Collapse Tests on Externally Pressurized Toroids

2003 ◽  
Vol 125 (1) ◽  
pp. 91-96 ◽  
Author(s):  
J. Błachut
Keyword(s):  
Mild Steel ◽  
Cross Section ◽  
Carrying Capacity ◽  
Circular Cross Section ◽  
External Pressure ◽  
Outer Diameter ◽  
Load Carrying Capacity ◽  
The Third ◽  
Load Carrying ◽  
Toroidal Shells

The paper discusses the load-carrying capacity of toroidal shells with closed circular cross section and loaded by static external pressure. Details about the manufacturing, pre-experiment measurements and testing of three, nominally different, steel toroids are provided. Two of them were manufactured from mild steel by spinning two halves and then welding them around the inner and outer equatorial perimeters. The third one has been assembled by welding four 90-deg stainless elbows. The outer diameter of these models was about 300 mm and the wall thickness varied from 2.0 to 3.0 mm. The hoop radius-to-thickness ratio, r/t, varied from about 15 to 30. The experimental collapse pressures were in the range from 4 to 8 MPa. Comparisons with numerical results are also provided.

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