Simplified Second Stage Creep/Relaxation Analysis of Moderately Complex Spatially Three-Dimensional Piping Systems

1974 ◽  
Vol 96 (3) ◽  
pp. 184-192 ◽  
Author(s):  
G. H. Workman ◽  
E. C. Rodabaugh
Keyword(s):  
Three Dimensional ◽  
Theoretical Development ◽  
Small Displacement ◽  
Piping System ◽  
Stress Strain ◽  
Curved Pipe ◽  
Thermal Change ◽  
Second Stage ◽  
Piping Systems ◽  
Applied Forces

An analysis technique for predicting the second stage creep/relaxation response of moderately complex spatially three-dimensional piping systems is presented herein. The theoretical development of this technique is based on two major assumptions. The first assumption is that at any time the behavior of the piping system can be associated with two components. One is an elastic component which is recoverable, and the other is a creep/relaxation component, which is not recoverable. The second major assumption, the simplifying assumption, is that the creep/relaxation strains due to axial, bending, and torsional loading can be decoupled and strains due to internal pressure can be neglected. Utilizing small displacement linear strain assumptions, the elastic stress-strain and creep/relaxation stress-strain rate laws can be integrated over the pipe’s cross section to yield generalized force-deformation relationships. The method of initial strains associated with the matrix displacement method of structural analysis is now applied to generate the solution of the creep/relaxation problem. This formulation utilizes two distinct types of piping elements. The first is a straight uniform pipe element and the second is a circularly curved pipe element, which incorporates both elastic and creep/relaxation flexibility factors. The end result of this formulation is a digital computer program capable of analyzing spatially three-dimensional piping systems under creep/relaxation conditions that can be represented by a series of straight or circularly curved pipe elements subjected to applied forces, displacements, and/or thermal change. An example analysis is included.

Creep Relaxation Behavior of High-Energy Piping

2000 ◽  
Vol 122 (4) ◽  
pp. 488-493 ◽  
Author(s):  
Raymond K. Yee ◽  
Marvin J. Cohn
Keyword(s):  
Stress Relaxation ◽  
Thermal Loading ◽  
Elevated Temperatures ◽  
Three Dimensional ◽  
Creep Damage ◽  
High Energy ◽  
External Loading ◽  
Piping System ◽  
Dead Weight ◽  
Piping Systems

The analysis of the elastic stresses in high-energy piping systems is a routine calculation in the power and petrochemical industries. The American Society of Mechanical Engineers (ASME) B31.1 Power Piping Code was developed for safe design and construction of pressure piping. Postconstruction issues, such as stress relaxation effects and selection of maximum expected creep damage locations, are not addressed in the Code. It has been expensive and time consuming to evaluate creep relaxation stresses in high energy piping systems, such as main steam and hot reheat piping. After prolonged operation of high-energy piping systems at elevated temperatures, it is very difficult to evaluate the redistribution of stresses due to dead weight, pressure, external loading, and thermal loading. The evaluation of stress relaxation and redistribution is especially important when nonideal conditions, such as bottomed-out or topped-out hangers, exist in piping systems. This paper uses three-dimensional four-node quadrilateral shell elements in the ABAQUS finite element code to evaluate the time for relaxation and the nominal relaxation stress values for a portion of a typical high-energy piping system subject to an ideally loaded hanger or to an overloaded hanger. The stress relaxation results are evaluated to suggest an approximation using elastic stress analysis results. [S0094-9930(00)01304-4]

Pulsation suppression in a reciprocating compressor piping system using a two-tank element

2017 ◽  
Vol 232 (4) ◽  
pp. 427-437 ◽  
Author(s):  
Quyang Ma ◽  
Zhenhuan Wu ◽  
Guoan Yang ◽  
Yue Ming ◽  
Zheng Xu
Keyword(s):  
Theoretical Model ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Wave Theory ◽  
Damping Coefficient ◽  
Piping System ◽  
Pressure Pulsations ◽  
Surge Tank ◽  
Piping Systems ◽  
Gas Pulsations

Gas pulsations excited by reciprocating compressors could introduce severe vibrations and noise in piping systems. When pulsating gas flows through the reducers, the changes in flow characteristics, such as velocity and damping coefficient, will affect the pressure pulsations. To circumvent these constraints, a two-tank element is introduced to control the gas pulsation that is still strong in the piping system with a surge tank. Installing another surge tank to form a two-tank element is more flexible and costs lower than replacing the original surge tank with a larger one. In this work, a theoretical model based on the wave theory was proposed to study the transferring mechanism of gas pulsations in the pipeline with the two-tank element. By considering the damping coefficient and the Mach number, the distributions of the pressure pulsations were predicted by the theoretical model and agreed with the three-dimensional fluid dynamics transient analysis. Three experiments were conducted to prove that the suppression capability of the two-tank element is as good as that of a single-tank element (surge tank) with the same surge volume. The volume optimization of the two-tank element is implemented by selecting the best allocations of the two tanks’ volumes to achieve larger reductions of pressure pulsations. Assuming that the total surge volume is constant, we found that the smaller the volume of the front tank (near the cylinder) is, the lower the pulsation levels are. The optimized result proves that in some conditions the two-tank element could control pulsations better than the single-tank element with the same surge volume.

Elastic-Plastic Analysis of Thick-Walled Toroidal Pressure Vessels

2008 ◽  
Author(s):  
R. Adibi-Asl
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Three Dimensional ◽  
Pressure Vessels ◽  
Toroidal Shell ◽  
Piping System ◽  
Straight Pipe ◽  
Element Analysis ◽  
Process Industries ◽  
Piping Systems

Piping systems in process industries and nuclear power plants include straight pipe runs and various fittings such as elbows, miter bends etc. Elbows and bends in piping systems provide additional flexibility to the piping system along with performing the primary function of changing the direction of fluid flow. Distinctive geometry of these toroidal shell components result in a structural behavior different from straight pipe. Hence, it would be useful to predict the behavior of these components with acceptable accuracy for design purposes. Analytical expressions are derived for stresses set up during loading and unloading in a toroidal shell subjected to internal pressure. Residual stresses in the component are also evaluated. The proposed solutions are then compared with three-dimensional finite element analysis at different locations including intrados, extrados and flanks.

Dynamic Response Studies of Piping-Support Systems

1990 ◽  
Vol 112 (1) ◽  
pp. 39-45 ◽  
Author(s):  
T. Chiba ◽  
R. Koyanagi
Keyword(s):  
Dynamic Characteristics ◽  
Support Systems ◽  
Three Dimensional ◽  
Local Stress ◽  
Integrated Approach ◽  
Piping System ◽  
3 Dimensional ◽  
Piping Systems ◽  
Seismic Loadings ◽  
High Level

Considering the effect of the interaction between piping and support systems in the piping design is a more integrated approach to improve the reliability of piping systems. So, it is important to clarify the dynamic characteristics of the piping and the restraint structure during the seismic events. It may be desirable to investigate the effect of the gap on the response and the local stress of the piping systems. The dynamic characteristics of a simplified piping model with gaps was investigated by the tests and the analysis. Three-dimensional piping model test was performed to estimate the effect of the gap on the response of the piping system. It can be found that the local stress and the stiffness of the piping and the restraint structure under the seismic loadings should be considered in the seismic design. The gap size was not so effective on the response of the 3-dimensional piping system in the high-level response.

Wave Propagation and Attenuation in Piping Systems

1986 ◽  
Vol 108 (4) ◽  
pp. 441-446 ◽  
Author(s):  
Shiran Nanayakkara ◽  
N. Duke Perreira
Keyword(s):  
Wave Propagation ◽  
Three Dimensional ◽  
Piping System ◽  
Transmission Matrix ◽  
Two Dimensional ◽  
Longitudinal Vibrations ◽  
Bending Vibrations ◽  
Piping Systems ◽  
Modes Of Vibration ◽  
Computational Errors

Results of an investigation on wave propagation in two-dimensional fluid-filled piping systems is reported. This phenomenon is studied by first developing a model for the transmission of solid-borne and fluid-borne vibrations in fluid-filled piping system elements, such as bends and straight sections. The aforementioned model, which is represented by an element transmission matrix, is used to determine the transfer and point impedances between the motion and forces of both the pipe and the fluid at any point within the element. It allows for longitudinal vibrations in the fluid, and longitudinal and bending vibrations in the solid portion of the system. The effects of both shear strains and rotary inertia within the pipe are included, while the effects of fluid flow and radial or angular modes in the fluid are neglected. Computer results for two-dimensional piping systems with modes of vibration in the plane of the pipes are considered. This method which is exact, except for possible computational errors, can be easily extended to the three-dimensional case.

A Multiaxial Stochastic Constitutive Law for Concrete: Part I—Theoretical Development

1992 ◽  
Vol 59 (2) ◽  
pp. 283-288 ◽  
Author(s):  
A. Fafitis ◽  
Y. H. Won
Keyword(s):  
Three Dimensional ◽  
Complex Loading ◽  
Uniaxial Stress ◽  
Constitutive Law ◽  
Theoretical Development ◽  
Stress Strain ◽  
Shear Moduli ◽  
Space Truss ◽  
Dependent Behavior ◽  
Path Dependent

An incremental three-dimensional constitutive relation for concrete has been developed. The linear anisotropic and path-dependent behavior is modeled by updating the stiffness matrix at each load increment. The material is assumed incrementally elastic and the six elastic moduli E11, E12 .... E33 are expressed in terms of both the tangential hydrostatic and deviatoric stiffness whereas the three tangential shear moduli are expressed in terms of the deviatoric stiffness only. The hydrostatic and deviatoric stiffness are determined from uniaxial stress-strain relationships by employing the space truss concept. The unaxial stress-strain relationships are in a sense the stress-strain relationships of the members of the truss, and they were based on a rheological stochastic model developed earlier. The predictions of the model compare favorably with experimental data reported by various investigators. Complex loading paths are reproduced with acceptable accuracy as is demonstrated in the second part of this paper.

Experimental and Numerical Studies of Ratcheting in a Pressurized Piping System Under Seismic Load

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
A. Ravikiran ◽  
P. N. Dubey ◽  
M. K. Agrawal ◽  
G. R. Reddy ◽  
R. K. Singh ◽  
...  
Keyword(s):  
Comprehensive Evaluation ◽  
Response Spectrum ◽  
Three Dimensional ◽  
Seismic Loading ◽  
Seismic Load ◽  
Piping System ◽  
Inelastic Response ◽  
Design Procedures ◽  
Numerical Studies ◽  
Piping Systems

Rational seismic design procedures necessitate comprehensive evaluation of nuclear piping systems under large amplitude seismic loads. This comprehensive assessment requires accurate prediction of inelastic response of piping system till failure to ensure adequate margins for unexpected beyond design basis events. The present paper describes the details of experimental and numerical studies of inelastic response of pressurized piping system under seismic loading. Shake table test has been carried out on a three-dimensional stainless steel piping system under internal pressure and seismic load. The amplitude of base excitation has been increased till failure of the piping system. The tested piping system has been analyzed using iterative response spectrum (IRS) method for various levels of excitation. The comparison of numerical and experimental results is given in the paper.

Applicability of the Multilayer Kinematic Hardening Model to Predict Inelastic Behavior of Piping Systems Under Excessive Seismic Loading

2016 ◽  
Author(s):  
Koji Iwata ◽  
Chuanrong Jin ◽  
Yasuhisa Karakida ◽  
Naoto Kasahara
Keyword(s):  
Carbon Steel ◽  
Dynamic Analysis ◽  
Kinematic Hardening ◽  
Seismic Loading ◽  
Cyclic Plasticity ◽  
Piping System ◽  
Stress Strain ◽  
Hardening Model ◽  
Nonlinear Stress ◽  
Piping Systems

For assessing possible failure of piping structures under excessive seismic loading, dynamic structural analysis methods employing advanced constitutive models need to be established. The multilayer kinematic hardening model for cyclic plasticity, which is applicable up to large strain, was proposed in the previous paper by the authors for carbon steel STS410 (JIS, Japanese Industrial Standard) to represent precisely nonlinear stress-strain relation as well as cyclic hardening, and was validated through its application to quasi-static cyclic bending tests of an elbow. In this paper, the applicability of the model to dynamic analysis of piping systems under earthquake loading is evaluated. An existing simulated earthquake excitation test of a piping system made of carbon steel STPT370 (JIS) is dealt with for validation of the finite element nonlinear dynamic analysis method using the presented model. To emphasize the advantage of this model, analyses using the conventional linear kinematic hardening model are also conducted. The results by the latter model are shown to be highly variable depending on the method of bilinear approximation of stress-strain curves. It is shown that the multilayer kinematic hardening model can predict well inelastic strains in piping systems under excessive earthquakes, which is important for the failure assessment.

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