Structural Analysis of Utility Boiler Waterwall

2005 ◽  
Author(s):  
Tae-Woan Kim ◽  
Jae-Cheol Kim ◽  
Suk-Hwan Hwang
Keyword(s):  
Structural Design ◽  
Orthotropic Plate ◽  
Fluid Pressure ◽  
Gas Pressure ◽  
Dead Weight ◽  
Large Size ◽  
Asme Code ◽  
Stress States ◽  
Critical Zones ◽  
Part Model

The safe structural design of boiler waterwalls with various loadings such as dead weight, fluid pressure, gas pressure and thermal differences is an extensive problem demanding the use of sophisticated computation methods due to the complexity of the geometric structure and the large size of the walls. To evaluate the operating reliability of boiler waterwalls, it is essential to know not only overall behavior of the whole structure but also the stress states at the critical zones. In this paper, the structural soundness for the Korea standard 500MW boiler waterwalls is preliminary examined. The equivalent orthotropic plate model is used to investigate the structural behavior of boiler waterwalls under thermal differences. Submodeling technique for part model of boiler waterwalls is proposed to accurately compute stresses of waterwalls at the critical zones under gas pressure. The computed stresses are combined and finally compared with the allowable stress limits according to the criteria of ASME Code.

Numerical Investigation on Behaviors of Stiffened Large Suction Cap for Offshore Suction Cofferdam

2020 ◽  
Author(s):  
Jeongsoo Kim ◽  
Yeon-Ju Jeong ◽  
Min-Su Park ◽  
Sunghoon Song
Keyword(s):  
Finite Element ◽  
Structural Design ◽  
Nonlinear Finite Element ◽  
Finite Element Models ◽  
Suction Pressure ◽  
Sheet Pile ◽  
Large Size ◽  
Critical Issues ◽  
Stress And Deformation ◽  
Pile Type

Abstract This study introduces a large offshore cofferdam installed by suction, unlike conventional ones such as a sheet-pile type, and proposes an effective suction cap for the cofferdam. In structural design view of the cofferdam, there are several critical issues due to its large size. This study conducted structural analyses of stiffened caps for large offshore suction cofferdam using fully nonlinear finite element models, and analyzed changes in behaviors of the cap due to stiffener arrangements to provide design insights. For finite element models, the diameter and the thickness of the suction cap (circular plate only) are 20m and 0.07m, respectively. Suction pressure on the cap was assumed to be 100kPa, all parts of the cofferdam except the cap are considered as boundary conditions. By investigating conventional suction anchors, several stiffener arrangement patterns on the cap of suction cofferdam were derived, and each arrangement was estimated by comparing stress and deformation of the cap. Also, reaction distributions on the edge of the cap were investigated to analyze effects of the stiffener arrangement on the interface behaviors between cap and cofferdam.

Influence of Elevated Temperature on the Acoustic Emission Evaluation of FRP Vessels Through Internal Fluid Pressure Tests

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Guillermo Ramirez ◽  
Paul H. Ziehl ◽  
Timothy J. Fowler
Keyword(s):  
Acoustic Emission ◽  
Elevated Temperature ◽  
Operating Temperature ◽  
Fluid Pressure ◽  
Pressure Vessels ◽  
The Body ◽  
Emission Testing ◽  
Internal Fluid ◽  
Asme Code ◽  
Acoustic Emission Testing

A research program evaluating the effect of elevated temperature in the acoustic emission testing of fiberglass vessels was completed recently. The program aimed at evaluating the current ASME provisions that require acoustic emission testing for Class II vessels be carried out at operating temperature in the event that the operating temperature exceeds 49°C (120°F). Lack of data from fiber reinforced polymer vessels and/or components that have been subjected to acoustic emission evaluation at elevated temperature has resulted in speculation regarding the appropriateness of conducting the acoustic emission evaluation at elevated temperature. To address these issues, an experimental investigation was conducted on representative coupon specimens and pressurized cylindrical specimens at differing temperatures. The results from the coupon tests were presented in a previous publication. This paper will present the results of the cylindrical specimens and compare them to the coupon specimens drawing the final conclusions from the overall results of the program. The results from this study resulted in changes in the body of the ASME code for testing pressure vessels with acoustic emission at temperature.

Ratchet Boundary for Superimposed Biaxial Membrane Stress States

2018 ◽  
Author(s):  
Wolf Reinhardt
Keyword(s):  
Thermal Expansion ◽  
Thermal Stress ◽  
Analytical Solution ◽  
Pressure Vessels ◽  
Stress Fields ◽  
Design Codes ◽  
Bending Stress ◽  
Membrane Stress ◽  
Asme Code ◽  
Stress States

Thermal membrane and bending stress fields exist where the thermal expansion of pressure vessel components is constrained. When such stress fields interact with pressure stresses in a shell, ratcheting can occur below the ratchet boundary indicated by the Bree diagram that is implemented in the design Codes. The interaction of primary and thermal membrane stress fields with arbitrary biaxiality is not implemented presently in the thermal stress ratchet rules of the ASME Code, and is examined in this paper. An analytical solution for the ratchet boundary is derived based on a non-cyclic method that uses a generalized static shakedown theorem. The solutions for specific applications in pressure vessels are discussed, and a comparison with the interaction diagrams for specific cases that can be found in the literature is performed.

Simulation of Excessive Deformation of Piping Due to Seismic and Weight Loads

2002 ◽  
Author(s):  
Tatsuya Fujiwaka ◽  
Hiroe Kobayashi ◽  
Yasuhide Asada ◽  
Chikashi Shitara
Keyword(s):  
Effective Means ◽  
Bending Moment ◽  
Dominant Frequency ◽  
General Purpose ◽  
Inertia Force ◽  
Piping System ◽  
Progressive Deformation ◽  
Dead Weight ◽  
Dynamic Reliability ◽  
Asme Code

The ASME Code for seismic design of piping system was revised in 1994 based on evaluation of pipe component test results submitted by the Piping and Fitting Dynamic Reliability Program (PFDRP). PFDRP indicated piping component failure to result in most cases from fatigue with ratchet. Excessive progressive deformation was noted by this program to ultimately occur in test #37, #39 and #40 piping models. This mode of failure was considered due to superposition of bending moment arising from vertical load produced by weight and horizontal seismic inertia force. To clarify the conditions leading to such failure, elastic-plastic dynamic analysis using the general-purpose FEM Code was carried out on the test#37 piping model of PFDRP. The analytical model and method were verified as effective means of study by comparison of analytical results with those obtained experimentally. The parameter determinations were made under condition of variation in dead weight stress and excitation and its dominant frequency. 1994 ASME seismic stress limits were shown effective for preventing excessive progressive deformation in tests #37, #39 and #40.

Moment Loads Induced by Pressure and Momentum Forces in Piping

1982 ◽  
Vol 104 (4) ◽  
pp. 268-271
Author(s):  
A. G. Ware
Keyword(s):  
Fluid Pressure ◽  
Axial Elongation ◽  
Internal Fluid ◽  
Pipe Segment ◽  
Asme Code ◽  
The Moment

A structural load, which is often overlooked when ASME Code analyses of piping and nozzles are conducted, is the moment induced by axial elongation of a pipe segment due to internal fluid pressure and momentum. An example illustrates that this effect can sometimes produce stresses which are too large to be ignored.

Ceramics Reliability: Statistical Analysis of Multiaxial Failure Using the Weibull Approach and the Multiaxial Elemental Strength Model

1988 ◽  
Author(s):  
Jacques Lamon
Keyword(s):  
Experimental Data ◽  
Structural Design ◽  
Mixed Mode ◽  
Bending Test ◽  
Second Step ◽  
Strength Model ◽  
Precise Evaluation ◽  
Ceramic Components ◽  
Stress States ◽  
Mode Failure

Methodology for designing reliable ceramic components requires a precise evaluation and correlation of strengths in different stress states. The present paper compares the merits of the Weibull approach and the Multiaxial Elemental Strength model on an experimental case involving mixed mode failure in the presence of bimodal flaw populations (surface and volume flaws). The experimental data were obtained using flexure specimens of Si3N4 tested at various spans, with the purpose of enhancing shearing effects. The analysis of data was refined by developing an advanced post-processor program to finite element codes, for failure probability determination based upon the Barnett-Freudenthal approximation of the Weibull approach and the Multiaxial Elemental Strength Model. In a second step, the strengths of the specimens exhibiting failures from the two concurrent populations of flaws (intermediate span) were predicted using both approaches from data obtained with different span lengths (long and short spans). Comparison with experimental data showed that the Multiaxial Elemental Strength Model is an improvement over the Weibull approach. It also allowed the short span bending test to be assessed. Finally, important implications for structural design with ceramics are discussed.

Method for Selecting Stress States for Use in an NB-3200 Fatigue Analysis

2010 ◽  
Author(s):  
Thomas L. Meikle V ◽  
E. Lyles Cranford ◽  
Mark A. Gray
Keyword(s):  
Time History ◽  
Stress Range ◽  
Total Stress ◽  
Secondary Stress ◽  
Transient Stress ◽  
Automated Method ◽  
Relative Minimum ◽  
Asme Code ◽  
Time Histories ◽  
Stress States

In ASME Code Section III NB-3222.4 fatigue evaluations, selecting stress states to determine the stress cycles according to Section NB-3216.2, Varying Principal Stress Direction, can become a challenging and complex task if the transient stress conditions are the result of multiple independent time varying stressors. This paper will describe an automated method that identifies the relative minimum and maximum stress states in a component’s transient stress time history and fulfills the criteria of NB-3216.2 and NB-3222.4. Utilization of the method described ensures that all meaningful stress states are identified in each transient’s stress time history. The method is very effective in identifying the maximum total stress range that can occur between any real or postulated transient stress time histories. In addition, the method ensures that the maximum primary plus secondary stress range is also identified, even if it is out of phase with the total stress maxima and minima. The method includes a process to determine if a primary plus secondary stress relative minimum or maximum should be considered in addition to those stress states identified in the total stress time history. The method is suitable for use in design analysis applications as well as in on-line stress and fatigue monitoring.

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