A Comprehensive Review of Ultimate and Allowable Stress Design Methodologies for External Load Calculation of Petrochemical Equipment: Eurocode 8 Versus ASME Codes

2003 ◽  
Author(s):  
Ch. Botsis ◽  
G. Anagnostides ◽  
N. Kokavesis
Keyword(s):  
Yield Stress ◽  
Safety Factor ◽  
Process Equipment ◽  
Design Codes ◽  
Allowable Stress ◽  
Design Philosophy ◽  
Design Methodologies ◽  
Strength Design ◽  
External Loads ◽  
Allowable Stress Design

The purpose of this paper is to provide a review of design methodologies for process equipment under pressure subjected to seismic loads. Such equipment includes spherical and cylindrical tanks, pressure vessels including towers and reactors, and fired heaters. For this equipment, the wall thickness of the pressure retaining space is designed so that the hoop stress is a fraction of the yield stress, Sy, of the material of construction. This fraction of the yield stress is called the allowable stress, Sm, and it is used in the allowable stress design codes such as ASME and API. However the magnitude of the stresses due to external loads is not determined by code rules. The task of calculating the stresses due to external loads is left up to the designer. Furthermore, process equipment is often sufficiently massive so that anchorage is needed to avoid overturning and a potential fire hazard. The anchors or bolts are imbedded in concrete bases, which are designed using strength design codes such as UBC, ASCE or EUROCODES. The level of stress in such structures is allowed to reach the yield stress of the material of construction. The safety factor in structures sized using allowable stress design philosophy is taken in the allowable stress. The safety factor in structures sized using strength design philosophy is realized by using load factors or increased loads. Guidelines are provided to solve the problem of merging the two design philosophies while avoiding the application of safety factors twice in the mechanical design of process equipment subjected to external loads and pressure.

scholarly journals ANALISIS KEKUATAN STRUKTUR HYDRAULIC LIFTING MACHINE DENGAN MENGGUNAKAN METODE ELEMEN HINGGA

SIMETRIS ◽  
2020 ◽  
Vol 14 (2) ◽  
pp. 39-45
Author(s):  
Ahmat Saebudin ◽  
Hendri Suryanto ◽  
Eva Hertnacahyani Herraprastanti
Keyword(s):  
Safety Factor ◽  
Allowable Stress ◽  
Von Mises ◽  
Allowable Stress Design

Hydraulic Lifting Machine merupakan jenis alat angkat yang didesain untuk memindahan barang ditempat yang relatif sempit. Dalam mendesain suatu alat selain fungsi dan kegunaannya kekuatan struktur merupakan salah satu aspek yang sangat penting untuk diperhatikan. Struktur tersebut haruslah mampu untuk menanggung beban yang timbul saat beroperasi dan memberikan keamanan bagi penggunanya dari kegagalan struktur. Oleh sebab itu tujuan dari penelitian ini adalah untuk menganalisis kekuatan struktur Hydraulic Lifting Machine dengan menggunakan metode elemen hingga. Berdasarkan hasil dari simulasi yang telah dilakukan dimana nilai tegangan resultan dan defleksi maksimum yang timbul pada struktur Hydraulic Lifting Machine yaitu pada beban kerja 100 kg tegangan resultannya sebesar 90,62 MPa dengan defleksi maksimum 4,39 mm, pada beban kerja 250 kg tegangan resultannya sebesar 218,51 MPa dengan defleksi 10,71 mm, pada beban kerja 500 kg tegangan resultannya sebesar 431,68 MPa dengan defleksi 21,25 mm, pada beban kerja 750 kg tegangan resultannya sebesar 644,84 MPa dengan defleksi 31,79 mm, dan pada beban kerja maksimal 1000 kg tegangan resultannya sebesar 858 MPa dengan defleksi 42,33 mm. Berdasarkan pada peraturan BS-5950 Structure Use of Steelwork in Building, nilai batas defleksi maksimumnya tidak boleh lebih dari 7,778 mm. Sedangkan untuk batas tegangan resultannya berdasarkan peraturan Allowable Stress Design (ASD) untuk dinyatakan aman adalah sebesar 149,7 MPa. Sehingga dapat disimpulkan bahwa struktur Hydraulic Lifting Machine layak digunakan dengan beban kerja maksimal 100 kg dengan angka safety factor 2,5.   Kata kunci : Crane, Metode Elemen Hingga, Tegangan Von Mises.

Design Methodologies for Arctic Gas Pipelines

2010 ◽  
Author(s):  
Germa´n E. Ortega ◽  
Pascinthe Saad
Keyword(s):  
Design Method ◽  
Design Methods ◽  
Clear Understanding ◽  
Allowable Stress ◽  
Gas Pipelines ◽  
Design Assessment ◽  
Design Methodologies ◽  
Modes Of Failure ◽  
Definition Of ◽  
Allowable Stress Design

The need to install gas pipelines in more technically difficult locations, coupled with very tight competitive economics necessitates increased efforts to consider more refined design methodologies that provide higher levels of certainty and result in more economical designs. The design of onshore gas pipelines in arctic environment must also address a number of Geohazards which will impose various external loads on the pipeline in addition to the internal pressure and other stress inducing loads that non-arctic pipelines typically experience. These geohazards include frost heave, thaw settlement, and soil movement and will tend to deform the pipeline and induce longitudinal strain at levels well above the linear elastic limit. The different design methods must account for these loads in order to ensure a rational and fit for purpose design. Currently, a design engineer can rely on one of three distinct design methods for onshore gas pipelines: Allowable Stress Design (ASD), Load and Resistance Factor Design (LRFD) or Reliability Based Design Assessment (RBDA). Each of the methods has advantages as well as disadvantages that could limit their applicability to a specific project. Clear understanding of the loads, the operational requirements, the environmental conditions and regulatory framework are all key factors in selecting the appropriate design method. Allowable Stress Design has been the traditional design method for onshore pipelines in the US and while the method leads to safe pipelines, the degree of safety and the inherent level of conservatism incorporated can often be improved. Gas pipelines can also be designed using probabilistic methods that require the consideration of credible modes of failure (limit states) and the calculation of the probability that these limits will be exceeded. Since the design engineer must evaluate each applicable mode of failure individually, the degree of conservatism and safety can be applied where needed the most. Probabilistic design methods can be used to achieve consistency and to provide a higher degree of certainty that pipelines would perform as designed [2]. Since probabilistic methodologies are typically applied only by small group of specialized consultants, a clear understanding of their strengths and limitations is required by all key personnel involved in the design and engineering decision making process. This paper will present a definition of the design methods as well as a direct comparison of all major components associated with each. Furthermore, it will provide a definition of commonly used terminologies associated with reliability and strain based design application in order to enhance the practical knowledge of the basis for each approach.

Determination of Modification Factor R for Seismic Design of Pressure Vessels Using ASME and Eurocodes

2005 ◽  
Author(s):  
N. Kokavesis ◽  
Ch. Botsis
Keyword(s):  
Seismic Design ◽  
Pressure Vessel ◽  
Structural Design ◽  
Response Spectrum ◽  
Pressure Vessels ◽  
Design Codes ◽  
Allowable Stress ◽  
Design Response Spectrum ◽  
Modification Factor ◽  
External Loads

The design of pressurized equipment such as columns, towers and reactors, heaters subjected to external loads is important from a safety point of view. Pressure vessel design codes provide guidelines for the combination of membrane stresses due to external loads and hoop stress. Customarily the seismic loads imposed by pressure vessel design codes are functions of allowable stress. The factor R is a modification factor of the design response spectrum. Its numerical value is based the capacity of a structural system to resist seismic actions in the nonlinear range. It generally reduces the seismic design forces to be smaller than those corresponding to a linear elastic response. The Uniform Building Code (UBC) has been used extensively for the seismic design of pressure vessels. With the advent of EUROCODES [2], the values proposed by UBC for factor R (usually 3 or 4) are not automatically accepted by local authorities. The pressure vessel mechanical designer must select a factor R that satisfies both the requirements of the pressure vessel code and the structural design code (local code) where the vessel is installed. This problem has also been acknowledged by several collogues in the past PVP conferences. In this paper the factor R is examined using ASME [10] codes and the guidelines provided by EUROCODES. A common basis for the selection of the factor R that satisfies both allowable stress design philosophies and structural design codes is established.

Allowable Stress Design of Rupture Strength Based on Confidence Level of 9Cr-1Mo Steel

2012 ◽  
Vol 155-156 ◽  
pp. 1107-1111
Author(s):  
Ji Bin Pei ◽  
Yun Feng Zhao ◽  
Shao Ping Yu ◽  
Jie Zhao
Keyword(s):  
Safety Factor ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Parameter Method ◽  
Allowable Stress ◽  
Reliability Design ◽  
Factor Method ◽  
Z Parameter ◽  
Rupture Data ◽  
Allowable Stress Design

The scattering of creep rupture data was represented by Z-parameter method based on Larson-Miller method. It was verified that the values of Z were supported by normal distribution. After obtained the distribution characteristics of creep rupture data using Z-parameter, reliability design for rupture allowable stress was carried out according to design life. Safety factor method is used for safety guarantee in conventional rupture allowable stress design and minimum rupture strength method is used in some standard. In comparison with safety factor method and minimum rupture strength method, it can be seen that reliability design based on Z-parameter is more agree with experimental data than other methods. Reliability design provides more precise results by considering the real distribution of creep rupture property and provides more flexible choice for design due to the need of safety and economy.

Stress Concentration at the Root of Bolt Thread

2010 ◽  
Author(s):  
Yasumasa Shoji ◽  
Toshiyuki Sawa
Keyword(s):  
Finite Element Analysis ◽  
Stress Concentration ◽  
Concentration Factor ◽  
The Other ◽  
Special Technique ◽  
Allowable Stress ◽  
Element Analysis ◽  
Bolt Stress ◽  
Thread Root ◽  
External Loads

The bolt strength is determined based on the concentrated bolt stress at the thread roots. The allowable stress is determined so that the thread root will not yield by the pretension and the external loads, using the stress concentration factor obtained as 3 to 5 from experiments. However, the concentration factor is not clear so far, as it is quite difficult to measure the stress at such a localized region. On the other hand, structural analysis, namely finite element analysis, has the possibility to provide the most-likely stress at the thread root. In this paper, a special technique, a.k.a. submodelling, is used to calculate the stress distribution at thread surfaces very precisely. The result will be useful to solve any stress related problems.

Strength Model Uncertainties of Burst, Yielding, and Excessive Bending of Piping

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Kleio Avrithi ◽  
Bilal M. Ayyub
Keyword(s):  
Structural Design ◽  
Design Method ◽  
Strength Model ◽  
Allowable Stress ◽  
Model Uncertainties ◽  
Reliability Based Design ◽  
Design Variables ◽  
Strength Models ◽  
Potential Use ◽  
Allowable Stress Design

Nuclear safety-piping is designed according to the ASME Boiler and Pressure Vessel Code, Sections III, NB-, NC-, and ND-3600 that use the allowable stress design method (ASD). The potential use instead of reliability-based design equations for nuclear piping could benefit the structural design by providing, among others, consistent reliability levels for piping. For the development of such equations, not only the probabilistic characteristics of the design variables are needed, but also the quantification of the uncertainties introduced by the strength models that are used in order to estimate the resistance of pipes subjected to different loadings. This paper evaluates strength models, and therefore provides necessary information for the reliability-based design of pipes for burst or yielding due to internal pressure and for excessive bending.

scholarly journals Diseño óptimo de estructuras tridimensionales para techos

2012 ◽  
Vol 22 (7) ◽  
pp. 25-31
Author(s):  
Maximino Tapia Rodriguez ◽  
Salvador Botello ◽  
Luz Angélica Caudillo ◽  
Héctor Hernández ◽  
Iván Munguía ◽  
...  
Keyword(s):  
Allowable Stress ◽  
Iron And Steel ◽  
Allowable Stress Design ◽  
Steel Institute

Se presenta un laboratorio virtual que realiza el análisis, diseño y optimización de estructuras de acero rolado en frío, así como la cuantificación de los materiales utilizados en la construcción de la techumbre completa y el costo de fabricación e instalación la misma. El software está dotado con una interfaz de usuario amigable desarrollado para la empresa “Tejas El Águila”. El análisis estructural considera cargas de peso propio, muertas y vivas, a las que estará sometida la estructura en condiciones de servicio, además de considerarse los efectos de viento y sismo para la República Mexicana -de acuerdo a la normatividad vigente. El optimizador está basado en métodos de minimización de entropía con restricciones múltiples, evaluando cada una de las estructuras por el método de la rigidez. Para la evaluación de la eficiencia de la estructura, se utiliza la normativa American Iron and Steel Institute- Allowable Stress Design (AISI-ASD). La optimización de las estructuras se realiza haciendo múltiples evaluaciones de diferentes configuraciones de las mismas, tarea que se ha paralelizado utilizando técnicas de programación de memoria compartida Open Multiprocessing (OpenMP). La combinación adecuada del seguimiento de las normatividades vigentes, la implementación del optimizador y los métodos matriciales para el cálculo de estructuras, aunado al ambiente grafico fácil de usar y amigable, han resultado en un potente software que genera soluciones de vivienda económicas, seguras y estéticas (favoreciendo así a un amplio sector de la sociedad mexicana).

A probabilistic study on the geometrical design of gravity retaining walls

2017 ◽  
Vol 14 (5) ◽  
pp. 414-422 ◽  
Author(s):  
Abdolhosein Haddad ◽  
Danial Rezazadeh Eidgahee ◽  
Hosein Naderpour
Keyword(s):  
Bearing Capacity ◽  
Failure Mode ◽  
Retaining Walls ◽  
Probability Analysis ◽  
Allowable Stress ◽  
Global Mode ◽  
Simple Method ◽  
Content Type ◽  
Mode Of Failure ◽  
Allowable Stress Design

Purpose The purpose of this study is to introduce a relatively simple method of probabilistic analysis on the dimensions of gravity retaining walls which might lead to a more accurate understanding of failure. Considering the wall geometries in the case of allowable stress design, the probability of wall failure is not clearly defined. The available factor of safety may or may not be sufficient for the designed structure because of the inherent uncertainties in the geotechnical parameters. Moreover, two cases of correlated and uncorrelated geotechnical variables are considered to show how they affect the results. Design/methodology/approach This study is based on the failure and stability of gravity retaining walls which can be stated in three different modes of sliding, overturning and the foundation-bearing capacity failure. Each of these modes of failure might occur separately or simultaneously with a corresponding probability. Monte Carlo simulation and Taylor series method as two conventional methods of probability analysis are implemented, and the results of an assumed example are calculated and compared together. Findings The probability analysis of the failure in each mode is calculated separately and a global failure mode is introduced as the occurrence of three modes of sliding, overturning and foundation-bearing capacity failure. Results revealed that the global mode of failure can be used along with the allowable stress design to show the probability of the worst failure condition. Considering the performance and serviceability level of the retaining structure, the global failure mode can be used. Furthermore, the correlation of geotechnical variables seems to be relatively more dominant on the probability of global failure comparing to each mode of failure. Originality/value The introduced terminology of global mode of failure can be used to provide more information and confidence about the design of retaining structures. The resulted graphs maintain a thorough insight to choose the right dimensions based on the required level of safety.

A Study of Axial Compression in the ASME B&PV Code for Pipe Supports and Restraints

2016 ◽  
Author(s):  
Phillip E. Wiseman ◽  
Zara Z. Hoch
Keyword(s):  
Axial Compression ◽  
Pressure Vessel ◽  
Slenderness Ratio ◽  
Elastic Buckling ◽  
Allowable Stress ◽  
Linear Elastic ◽  
Division 1 ◽  
Asme Code ◽  
American Society ◽  
Allowable Stress Design

Axial compression allowable stress for pipe supports and restraints based on linear elastic analysis is detailed in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section III, Division 1, Subsection NF. The axial compression design by analysis equations within NF-3300 are replicated from the American Institute of Steel Construction (AISC) using the Allowable Stress Design (ASD) Method which were first published in the ASME Code in 1973. Although the ASME Boiler and Pressure Vessel Code is an international code, these equations are not familiar to many users outside the American Industry. For those unfamiliar with the allowable stress equations, the equations do not simply address the elastic buckling of a support or restraint which may occur when the slenderness ratio of the pipe support or restraint is relatively large, however, the allowable stress equations address each aspect of stability which encompasses the phenomena of elastic buckling and yielding of a pipe support or restraint. As a result, discussion of the axial compression allowable stresses provides much insight of how the equations have evolved over the last forty years and how they could be refined.

Sign in / Sign up

Export Citation Format

Share Document