scholarly journals Undercut tolerances in industry from a fracture mechanic perspective

2018 ◽  
Vol 165 ◽  
pp. 21009 ◽  
Author(s):  
Ceferino Steimbreger ◽  
Mirco Chapetti
Keyword(s):  
Fracture Mechanic ◽  
Cyclic Load ◽  
Damage Mechanism ◽  
Large Structures ◽  
Minimum Requirements ◽  
Load Effects ◽  
Design Loads ◽  
Mechanic Approach ◽  
Time Structures ◽  
Stress Raisers

Fatigue is an important damage mechanism that particularly affects welded components, since they are likely to present residual stresses, inhomogeneities and stress raisers. Assessment of cyclic load effects on welds has concerned both industries and scientist for decades; unexpected failure must be prevented and at the same time, structures must withstand design loads with minimum requirements of material. All these facts together with economic issues have lead to the creation of normative that rule designing and construction of welded components. Particularly, toe undercuts are generally found in large structures, and large scatter and disagreement exists towards their significance and effects. Documents usually limit only their depth without considering radius, width or length, and there is currently no explanation to that fact. Understanding the damaging process will also help to set less conservative tolerances, with consequent cost reduction due to less demanding inspection. The present paper deals with a fracture mechanic approach that uses the Resistance Curve concept to predict fatigue limit of welded components with undercuts. Results revealed that depth is the most influencing variable, and it can be used as the limiting parameter in design regulations. Moreover, good correlation was obtained with FAT values normally assigned to this kind of defect.

Span Rating of Solid-Sawn Deck Boards

2021 ◽  
Vol 71 (2) ◽  
pp. 171-176
Author(s):  
Madison A. Broers ◽  
Donald A. Bender
Keyword(s):  
North America ◽  
Dynamic Load ◽  
Building Code ◽  
Standard Committee ◽  
Minimum Requirements ◽  
Design Loads ◽  
Policy Testing ◽  
Technical Basis

Abstract Deck boards are key components in outdoor decks and balconies. The deck board market is shared primarily between solid-sawn and composite products. The focus of this article is solid-sawn wood deck boards, which are manufactured in North America as span-rated products following a policy promulgated by the American Lumber Standard Committee (ALSC). The latest revision of the ALSC span rating policy was approved in November 2020, and this article describes the technical basis for the changes. Distributed and concentrated design loads specified in the policy exceed building code minimum requirements. In addition, dynamic load amplification due to deck occupants is included in the new policy. Testing was performed to characterize the effects of partial fixity at joist supports caused by screw fasteners and was incorporated into the span rating methodology.

scholarly journals Legal and Permit Loads Evaluation for Indiana Bridges

2021 ◽  
Author(s):  
Chris Kusiak ◽  
Mark D. Bowman ◽  
Arun Prakash
Keyword(s):  
The State ◽  
Federal Law ◽  
Commercial Vehicles ◽  
Interstate Highways ◽  
Design Load ◽  
Current State ◽  
Load Effects ◽  
Design Loads ◽  
Specific Amount ◽  
Highway System

According to federal law, routine commercial vehicles must adhere to certain limits on their load configuration in order to operate legally on interstate highways. However, states may allow for heavier or different load configurations provided that bridges on the state and county highway system are load rated and, if necessary, posted with vehicles that appropriately represent these loads. The state of Indiana allows several classes of vehicles to operate with loads that exceed federal limits, and, presently, several LFD design loads are used to represent these exceptions as state legal loads. This study evaluates the MBE rating loads for their ability to encompass Indiana’s exception vehicles and recommends a set of state rating loads which can replace the current state legal loads and, combined with the MBE rating loads, satisfactorily encompass the load effects due to these exceptions. Comparing moment and shear envelopes on a representative set of bridges, the MBE rating vehicles were found to be insufficient for representing Indiana’s exception vehicles. Three new rating loads are proposed which encompass the exception vehicles efficiently and represent realistic legal loads. Conversely, acceptable HS-20 rating factors are also provided as an alternative to the adoption of these new vehicles. These rating factors, all 1.0 or greater, can ensure a similar level of safety by requiring a specific amount of excess capacity for the HS-20 design load.

Practical Calculation of Global Design Loads and Load Effects for Large High Speed Catamarans

2001 ◽  
Author(s):  
Svein Erling Heggelund ◽  
◽  
Jan Roger Hoff ◽  
Torgeir Moan ◽  
Stig Oma ◽  
...  
Keyword(s):  
High Speed ◽  
Practical Calculation ◽  
Load Effects ◽  
Design Loads

Overlay Replacement Feasibility Study of the Burlington Cable Stayed Bridge

2019 ◽  
Author(s):  
Yinghong Cao ◽  
Gregory Hasbrouck ◽  
Robert A. Magliola ◽  
Michael J. Todsen
Keyword(s):  
Mississippi River ◽  
Original Design ◽  
Significant Deterioration ◽  
Cable Stayed Bridge ◽  
Stay Cables ◽  
Main River ◽  
Local Stresses ◽  
Load Effects ◽  
Design Loads

<p>The Burlington Bridge, built in 1993, spans over the Mississippi River at Burlington, Iowa. The main river crossing is a 379‐m‐long cable stayed bridge carrying two westbound lanes and three eastbound lanes of U.S. Route 34. After 25 years of service, the concrete overlay and barrier are planned for replacement due to deterioration and cracking. This paper presents the methodology of the feasibility analysis for the replacement plan. Based on recent inspection reports, no significant deterioration of the primary structural elements of the bridge was found that would reduce the capacity of the structure to accommodate the original design loads. Without in‐depth determination of the capacity of the existing structure, the feasible construction staging was evaluated by comparing the effect of construction activities with the design live load effects. Various construction staging alternatives with reduced traffic lanes were investigated and optimized. The load effects on the primary structural components including towers, stay cables, edge girders, floor beams, deck and bearings were the main targets of comparison. Both global structural behavior and local stresses on these members were analyzed. After the analytical study, the most favorable construction staging was proposed for further consideration and refinement.</p>

Fatigue Capacity of Steel Cylindrical Bodies and Conduits Subjected to Cyclic Pressure

2014 ◽  
Author(s):  
Anders Wormsen ◽  
Finn Kirkemo ◽  
Anthony David Muff
Keyword(s):  
Fatigue Life ◽  
Lower Bound ◽  
Yield Strength ◽  
Fracture Mechanic ◽  
Code Review ◽  
Cyclic Pressure ◽  
Mechanic Approach ◽  
Number Of Cycles ◽  
Conclusion Section ◽  
Leak Before Break

This paper presents a code review (API 17G, ASME VIII Div 2 and ASME VIII Div 3) for addressing the fatigue capacity of steel cylindrical bodies and conduits subjected to cyclic pressure only. The fatigue capacity for pipes with a yield strength of 75ksi and 90ksi and with rated working pressures (RWP) ranging from 5ksi to 30ksi have been considered using both the S-N approach and the fracture mechanic approach. The S-N based fatigue lives from API 17G are found to be much longer than the corresponding S-N based fatigue lives from ASME VIII Div 2 and Div 3 and by the fracture mechanic (FM) approach as required in ASME VIII Div 3 for vessels where a leak-before-break condition can not be demonstrated. The S-N predicted fatigue lives are found to decrease with increasing RWP while the FM based fatigue lives are found to be rather independent of the RWP. The S-N based fatigue lives from ASME VIII Div 2 and Div 3 for free corrosion conditions are found to be shorter than the corresponding FM based fatigue lives for RWPs ≥ 25ksi and ≥ 20ksi, respectively. Based on this work, it is recommended to establish the fatigue capacity of steel cylindrical bodies and conduits subjected to cyclic pressure using either ASME VIII Div 2 or Div 3. The FM approach is considered to give a lower bound fatigue life as the number of cycles to initiate a crack is disregarded. Guidance on when it is considered applicable to use the API 17G criterion is given in the conclusion section of this paper.

Elemental mass loss in silicate minerals during x-ray analysis

1990 ◽  
Vol 48 (4) ◽  
pp. 804-805
Author(s):  
P.E. Champness ◽  
R.W. Devenish
Keyword(s):  
Mass Loss ◽  
Current Density ◽  
Damage Mechanism ◽  
Beam Current ◽  
Single Chain ◽  
Plagioclase Feldspar ◽  
X Ray ◽  
Alkali Ions ◽  
Structural Order ◽  
Sheet Silicate

It has long been recognised that silicates can suffer extensive beam damage in electron-beam instruments. The predominant damage mechanism is radiolysis. For instance, damage in quartz, SiO2, results in loss of structural order without mass loss whereas feldspars (framework silicates containing Ca, Na, K) suffer loss of structural order with accompanying mass loss. In the latter case, the alkali ions, particularly Na, are found to migrate away from the area of the beam. The aim of the present study was to investigate the loss of various elements from the common silicate structures during electron irradiation at 100 kV over a range of current densities of 104 - 109 A m−2. (The current density is defined in terms of 50% of total current in the FWHM probe). The silicates so far ivestigated are:- olivine [(Mg, Fe)SiO4], a structure that has isolated Si-O tetrahedra, garnet [(Mg, Ca, Fe)3Al2Si3AO12 another silicate with isolated tetrahedra, pyroxene [-Ca(Mg, Fe)Si2O6 a single-chain silicate; mica [margarite, -Ca2Al4Si4Al4O2O(OH)4], a sheet silicate, and plagioclase feldspar [-NaCaAl3Si5O16]. Ion- thinned samples of each mineral were examined in a VG Microscopes UHV HB501 field- emission STEM. The beam current used was typically - 0.5 nA and the current density was varied by defocussing the electron probe. Energy-dispersive X-ray spectra were collected every 10 seconds for a total of 200 seconds using a Link Systems windowless detector. The thickness of the samples in the area of analysis was normally 50-150 nm.

Learning of pitch and time structures in an artificial grammar setting.

2018 ◽  
Vol 44 (8) ◽  
pp. 1201-1214 ◽  
Author(s):  
Jon B. Prince ◽  
Catherine J. Stevens ◽  
Mari Riess Jones ◽  
Barbara Tillmann
Keyword(s):  
Artificial Grammar ◽  
Time Structures

Review of the Current State and Future Development in Standardizing Natural Lighting in Interiors

2018 ◽  
pp. 5-26 ◽  
Author(s):  
Stanislav Darula
Keyword(s):  
Human Life ◽  
Natural Light ◽  
Artificial Lighting ◽  
Computer Tools ◽  
Natural Lighting ◽  
Current State ◽  
Minimum Requirements ◽  
Life On Earth ◽  
Window Design

Three elements mainly wind, water and sun seemed to determine in ancient ages the basic phenomena of life on Earth. Architectural history documented the importance of sun influence on urban and building construction already in layouts of Mesopotamian and Greek houses. Not only sun radiation but especially daylight played a significant role in the creation of indoor environment. Later, in the 20th century, a search of interaction between human life in buildings and natural conditions were studied considering well­being and energy conscious design recently using computer tools in complex research and more detail interdisciplinary solutions. At the same time the restricted daytime availability of natural light was supplemented by more efficient and continually cheaper artificial lighting of interiors. There are two main approaches to standardize the design and evaluation of indoor visual environment. The first is based on the determination of the minimum requirements respecting human health and visibility needs in all activities while the second emphasizes the behaviour and comfort of occupants in buildings considering year­around natural changes of physical quantities like light, temperature, noise and energy consumption. The new current standardization basis for daylight evaluation and window design criteria stimulate the study of methodology principles that historically were based on the overcast type of sky luminance pattern avoiding yearly availability of sky illuminance levels. New trends to base the daylight standardization on yearly or long­term availability of daylight are using the averages or median sky illuminance levels to characterise local climatological conditions. This paper offers the review and discussion about the principles of the natural light standardization with a short introduction to the history and current state, with a trial to focus on the possible development of lighting engineering and its standards in future.

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