Piping Seismic Stress Limits: A Critical Review

2002 ◽  
Author(s):  
Gerry C. Slagis
Keyword(s):  
Nonlinear Dynamic ◽  
Static Load ◽  
Dynamic Factor ◽  
Seismic Capacity ◽  
Strength Factor ◽  
Linear Elastic ◽  
Dynamic Factors ◽  
Load Limit ◽  
Potential Failure ◽  
Seismic Stress

Seismic stress limits for nuclear piping were published by the Section III code in 1994. Because of concerns on the technical bases for the rules, NRC has not approved their use. Modifications to the rules have been made in 2001. The 1994 seismic stress limits are reduced, and one type of joint now has a seismic stress limit that is less that the static load limit. A limit for seismic that is less than the limit for a static load contradicts the test data. Most of the technical concerns were valid. The 1994 rules are based on the premise that collapse is not a potential failure mode for a seismic event. However, collapse occurred in two of the EPRI component tests. Seismic margins in the component tests were overestimated. Revisions to the seismic margin data do not support the higher stress limits. A different approach has been taken to justify the 2001 rules. A probability approach is used where seismic capacity is related to a strength factor. The strength factor is based on the measured ultimate moment in the component tests. The capacity is the strength factor multiplied by a nonlinear dynamic factor. A small nonlinear dynamic factor is used because of concerns with off-resonance margin in stiff components. In contrast, the tests demonstrate large nonlinear dynamic factors. The intent of the new rules is to limit piping response to the SSE to the linear elastic range.

Using Dynamic Analysis for Compact Gear Design

1998 ◽  
Author(s):  
Ping-Hsun Lin ◽  
Hsiang Hsi Lin ◽  
Fred B. Oswald ◽  
Dennis P. Townsend
Keyword(s):  
Dynamic Response ◽  
Bending Strength ◽  
Three Dimensional ◽  
Spur Gear ◽  
Dynamic Factor ◽  
Operating Speed ◽  
Gear Design ◽  
Dynamic Factors ◽  
Speed Range ◽  
Response Change

Abstract This paper presents procedures for designing compact spur gear sets with the objective of minimizing the gear size. The allowable tooth stress and dynamic response are incorporated in the process to obtain a feasible design region. Various dynamic rating factors were investigated and evaluated. The constraints of contact stress limits and involute interference combined with the tooth bending strength provide the main criteria for this investigation. A three-dimensional design space involving the gear size, diametral pitch, and operating speed was developed to illustrate the optimal design of spur gear pairs. The study performed here indicates that as gears operate over a range of speeds, variations in the dynamic response change the required gear size in a trend that parallels the dynamic factor. The dynamic factors are strongly affected by the system natural frequencies. The peak values of the dynamic factor within the operating speed range significantly influence the optimal gear designs. The refined dynamic factor introduced in this study yields more compact designs than AGMA dynamic factors.

Lessons Learned From Freespans at Pipeline Watercourse Crossings

2020 ◽  
Author(s):  
Gerry Ferris
Keyword(s):  
Static Load ◽  
Water Velocity ◽  
Lessons Learned ◽  
Vortex Induced Vibration ◽  
Water Loading ◽  
Relevant Question ◽  
The Past ◽  
Load Limit ◽  
Pipeline Failure

Abstract Over the past 10 years inspections (site visits, boat based surveys or diver surveys) have been completed at nearly 20,000 pipeline watercourse crossings for 20 different pipeline owners. During the last 10 years there have been 721 unique locations where an exposed pipeline was found and at 213 of these locations a freespan was encountered. Only one of the freespans resulted in the failure (loss of product) of the pipeline. This record illustrates what is now become widely accepted, that pipeline exposure does not necessarily lead to pipeline failure. The record adds to this, pipeline freespan does not necessarily lead to failure. This highlights that the relevant question for “water loading caused pipeline failure” is: Does the combination of freespan length and water velocity exceed a combination that would lead to vortex induced vibration or the exceedance of the static load limit of the pipe?

Implications of cumulated seismic damage on the seismic performance of unreinforced masonry buildings

2014 ◽  
Vol 47 (2) ◽  
pp. 157-170 ◽  
Author(s):  
Amaryllis Mouyiannou ◽  
Andrea Penna ◽  
Maria Rota ◽  
Francesco Graziotti ◽  
Guido Magenes
Keyword(s):  
Nonlinear Dynamic ◽  
Fragility Curves ◽  
Seismic Damage ◽  
Unreinforced Masonry ◽  
Masonry Building ◽  
Masonry Buildings ◽  
Seismic Capacity ◽  
Building Stock ◽  
Dynamic Analyses ◽  
Nonlinear Dynamic Analyses

The seismic capacity of a structure is a function of the characteristics of the system as well as of its state, which is mainly affected by previous damage and deterioration. The cumulative damage from repeated shocks (for example during a seismic sequence or due to multiple events affecting an unrepaired building stock) affects the vulnerability of masonry buildings for subsequent events. This paper proposes an analytical methodology for the derivation of state-dependent fragility curves, taking into account cumulated seismic damage, whilst neglecting possible ageing effects. The methodology is based on nonlinear dynamic analyses of an equivalent single degree of freedom system, properly calibrated to reproduce the static and dynamic behaviour of the structure. An application of the proposed methodology to an unreinforced masonry case study building is also presented. The effect of cumulated damage on the seismic response of this prototype masonry building is further studied by means of nonlinear dynamic analyses with the accelerograms recorded during a real earthquake sequence that occurred in Canterbury (New Zealand) between 2010 and 2012.

Dynamic Factors and Asset Pricing

2010 ◽  
Vol 45 (3) ◽  
pp. 707-737 ◽  
Author(s):  
Zhongzhi (Lawrence) He ◽  
Sahn-Wook Huh ◽  
Bong-Soo Lee
Keyword(s):  
Asset Pricing ◽  
Factor Model ◽  
Dynamic Factor ◽  
Pricing Model ◽  
Portfolio Returns ◽  
Dynamic Factors ◽  
Ex Ante ◽  
Out Of Sample ◽  
Competing Models ◽  
Fama And French

AbstractThis study develops an econometric model that incorporates features of price dynamics across assets as well as through time. With the dynamic factors extracted via the Kalman filter, we formulate an asset pricing model, termed the dynamic factor pricing model (DFPM). We then conduct asset pricing tests in the in-sample and out-of-sample contexts. Our analyses show that the ex ante factors are a key component in asset pricing and forecasting. By using the ex ante factors, the DFPM improves upon the explanatory and predictive power of other competing models, including unconditional and conditional versions of the Fama and French (1993) 3-factor model. In particular, the DFPM can explain and better forecast the momentum portfolio returns, which are mostly missed by alternative models.

Dynamic factor to live load regulation during structural calculation of bridges at high-speed networks

2017 ◽  
pp. 15-27 ◽  
Author(s):  
Leonid Dyachenko ◽  
Andrey Benyn ◽  
Vladimir Smyrnov
Keyword(s):  
Dynamic Analysis ◽  
High Speed ◽  
Strain State ◽  
Dynamic Factor ◽  
Live Load ◽  
Labor Costs ◽  
Stress Strain ◽  
Stress Strain State ◽  
Dynamic Factors ◽  
High Speed Trains

Objective: Improvement of dynamic analysis method of simple beam spans in the process of high-speed trains impact. Methods: Mathematical modeling with numerical and analytical methods of building mechanics was applied. Results: The parameters of high-speed trains influence on simple beam spans of bridges were analyzed. The method of dynamic factor to live load determination was introduced. The reliability of the method in question was corroborated by the results of numerical simulation of high-speed trains’ movement by beam spans with different speeds. The introduced algorithm of dynamic analysis was based on the connection between maximum acceleration of a beam span in resonance vibration mode and the basic factors of stress-strain state. The method in question makes it possible to determine both maximum and bottom values of main loading in a construction, which determines the possibility of endurance tests. It was noted that dynamic additions for the components of stress-strain state (bending moments, shear force, vertical deflections) were different. The fact in question determines the necessity of differential approach application to identify dynamic factors in the process of calculation testing on the first and the second groups of limit states. Practical importance: The method of dynamic factors’ determination presented in the study makes it possible to perform dynamic analysis and determine the main loading in simple beam spans without application of numerical modeling and direct analytical analysis, which considerably reduces labor costs on engineering.

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