Minimizing Fatigue and Fracture in Steel Bridges

1980 ◽  
Vol 102 (1) ◽  
pp. 20-25 ◽  
Author(s):  
J. W. Fisher ◽  
B. T. Yen ◽  
K. H. Frank
Keyword(s):  
Laboratory Tests ◽  
Field Data ◽  
Steel Bridges ◽  
Range Limits ◽  
Live Load ◽  
Stress Range ◽  
Fatigue And Fracture ◽  
Live Loads ◽  
Material Fracture ◽  
Initiation Stage

Steel bridges are subjected to live loads which produce variable stress ranges in bridge components. At welded bridge details, the existence of initial defects and residual stresses eliminate the initiation stage of fatigue crack growth, and stress range is found to be the controlling factor for crack propagation. Laboratory tests have resulted in stress range-fatigue life relationships for various bridge details. These data correlate well with fracture mechanics theory and with field data. Limits on live load stresses have been adopted for steel bridges. Coupled with material fracture toughness requirements, the stress range limits minimize the probability of fatigue and fracture in steel bridges.

Structural Behavior of Three-Sided Arch Span Bridge

1996 ◽  
Vol 1541 (1) ◽  
pp. 112-119 ◽  
Author(s):  
Timothy J. McGrath ◽  
Ernest T. Selig ◽  
Timothy J. Beach
Keyword(s):  
Structural Design ◽  
Load Test ◽  
Structural Performance ◽  
Live Load ◽  
Element Analysis ◽  
Annual Basis ◽  
Soil Stress ◽  
Load Effects ◽  
Live Loads ◽  
Adjacent Segments

A study was undertaken to evaluate the methodology used for the structural design of three-sided culverts with arched top slabs. An 11-m span by 3.4-m rise bridge was instrumented and monitored during installation, under an HS-25 + 30 percent live load and at 6-month intervals for 2 years after installation. The bridge consisted of ten 1.6-m-wide precast segments. Three of the interior segments were instrumented with soil stress cells mounted on the legs of the bridge and with anchor pins for use with a tape extensometer to determine change in shape of the bridge. Survey data were taken on the same three segments and the two adjacent segments. Visual observations were also made to monitor cracking. The live load test was conducted with 0.3 m of cover. Final cover was 0.9 m. The bridge showed less movement under the live load than under the 0.9 m of earth load. The 2-year data show that the shape of the bridge and the soil stresses at the sides of the bridge cycle on an annual basis and that the spans have increased 4 to 8 mm over the 2 years since the completion of construction and appear to be still increasing. Overall, the structural performance of the bridge under earth and live loads was excellent. The correlation between the measured behavior and the computer analysis was good except that the actual live load effects were much smaller than assumed for design. The results of the project support the use of finite-element analysis to design such structures.

Random Load Fatigue: Theory and Experiment

1985 ◽  
Vol 199 (3) ◽  
pp. 249-257 ◽  
Author(s):  
J M Tunna
Keyword(s):  
Traditional Method ◽  
Laboratory Tests ◽  
Stress Range ◽  
Constant Amplitude ◽  
Random Load ◽  
Welded Steel ◽  
Random Loads ◽  
Fatigue Design ◽  
Stress Signal ◽  
Theory And Experiment

This paper is concerned with the problem of fatigue design for random loads. A theory is outlined which allows the fatigue life to be predicted from the constant amplitude stress range–life curve and the standard deviation and ruling frequency of the stress signal. Laboratory tests are described which verify the theory for welded steel constructions in a railway environment. The results are also analysed by a more traditional method. Areas where the theory might usefully be extended are identified.

Synthesis of a Time History Based on the Sine-on-Random Prediction Methodology Defined in MIL-STD-810 Method 519

2017 ◽  
Vol 60 (1) ◽  
pp. 31-41
Author(s):  
Michael T. Hale
Keyword(s):  
Time Domain ◽  
Laboratory Tests ◽  
Field Data ◽  
Time History ◽  
Environmental Engineering ◽  
New Technique ◽  
Vibration Test ◽  
Temporal Characteristics ◽  
New Time ◽  
Exponentially Weighted

Abstract Method 519.7, Annex D of MIL-STD-810G, Environmental Engineering Considerations and Laboratory Tests, Change Notice 1 (MIL-STD-810G/CN1) outlines a prediction methodology for establishing a sine-on-random (SoR) structured spectrum that is intended to be representative of gunfire for use in cases in which there is an absence of field data. From that spectrum, the ramp modulated pulse (RMP) technique is proposed as a methodology to synthesize a time history with temporal characteristics that more realistically represent the temporal characteristics of gunfire than that of a SoR time history synthesized via classical SoR generation techniques. This paper provides an alternate technique to the RMP methodology presented in Method 519. The alternate technique is based on normalized exponentially weighted (NEW) time history generated via classical time domain techniques for a SoR vibration test. An outline of the NEW technique and an associated example are provided.

scholarly journals Nectar Meals of a Mosquito-Specialist Spider

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Josiah O. Kuja ◽  
Robert R. Jackson ◽  
Godfrey O. Sune ◽  
Rebecca N. H. Karanja ◽  
Zipporah O. Lagat ◽  
...  
Keyword(s):  
Plant Species ◽  
Laboratory Tests ◽  
Field Data ◽  
Ricinus Communis ◽  
Aloe Vera ◽  
East African ◽  
Natural Diet ◽  
Striga Asiatica ◽  
Early Instar ◽  
Evarcha Culicivora

Evarcha culicivora, an East African jumping spider, is known for feeding indirectly on vertebrate blood by actively choosing blood-carrying mosquitoes as prey. Using cold-anthrone tests to detect fructose, we demonstrate thatE. culicivoraalso feeds on nectar. Field-collected individuals, found on the plantLantana camara, tested positive for plant sugar (fructose). In the laboratory,E. culicivoratested positive for fructose after being kept withL. camaraor one of another ten plant species (Aloe vera, Clerodendron magnifica, Hamelia patens, Lantana montevideo, Leonotis nepetaefolia, Parthenium hysterophorus, Ricinus communis, Senna didymobotrya, Striga asiatica, andVerbena trivernia). Our findings demonstrate thatE. culicivoraacquires fructose from its natural diet and can ingest fructose directly from plant nectaries. However, experiments in the laboratory also show thatE. culicivoracan obtain fructose indirectly by feeding on prey that have fed on fructose, implying a need to consider this possibility when field-collected spiders test positive for fructose. In laboratory tests, 53.5% of 1,215 small juveniles, but only 3.4% of 622 adultE. culicivora, left with plants for 24 hours, were positive for fructose. These findings, along with the field data, suggest that fructose is especially important for early-instar juveniles ofE. culicivora.

Probabilistic Analysis of Live Loads on Offshore Platform Piles

2005 ◽  
Author(s):  
Hassan Zaghloul ◽  
Beverley Ronalds ◽  
Geoff Cole
Keyword(s):  
Probabilistic Analysis ◽  
Field Measurements ◽  
Weather Conditions ◽  
Load Resistance ◽  
Live Load ◽  
Offshore Platforms ◽  
Open Area ◽  
Foundation Design ◽  
Live Loads ◽  
Load Intensity

Relatively accurate techniques are available to assess structural behavior under given loads, yet the loads themselves remain an estimate based in part on field measurements, in part on professional logic and experience, and in part on trial and error. The design of piled foundations for fixed offshore platforms must consider operating and extreme weather conditions. In the operating condition, the magnitude of live loads on open areas of topside structure is an important consideration. Unfortunately, the design live load intensity that applies to open areas on offshore platforms is not identified in international codes and standards. There does not appear to be any consensus on the value to be adopted in the industry. Some operators suggest the open area live loads need not be considered for pile foundation design, while others stipulate values such as 10 kPa. This is partly due to the variability associated with the different live loads sources. The objective of this study is to obtain a better understanding of open area live loads on offshore platforms and develop a methodology to obtain the long-term and extreme open area live load. A load survey was conducted for the purpose of this study, and a probabilistic analysis was carried out to derive the maximum axial load on piles that is expected during platform lifetime. The results of this study indicate that the use of a single value for the open area live load (OALL) may not be appropriate and suggest appropriate values for Load Resistance Factor Design (LRFD) or Working Stress Design (WSD) methods.

HAND TOOLS OPERATOR 'S HEALTH WORKSHOP ON MECHANICAL AND LEVEL OF RISK WHITE SYNDROME FINGERS

2016 ◽  
Vol 78 (5) ◽  
Author(s):  
Toni Dwi Putra ◽  
Vitri Pitrandjalisari ◽  
Nurida Finahari
Keyword(s):  
Working Conditions ◽  
Laboratory Tests ◽  
Field Data ◽  
Field Trials ◽  
Safety Equipment ◽  
Hand Tools ◽  
White Syndrome ◽  
Shoulder Joints ◽  
Hand Tool ◽  
Negative Effect

Workers in the metal industry are using the equipment (hand tool) that produces vibrations. These vibrations have a negative effect on the fingers, forearm, or shoulder joints. Disorders that often arises is often called the effects of hand arm vibration. These effects vary of workers, ranging from finger whitened condition to the inability to move the finger. Lack of security and safety equipment will further enlarge this negative effect, because the disturbance will result in declining labor productivity. This study aims to model safety equipment in the form of fluidic damper to reduce glove hand arm vibration. This objective will be carried out in stages: 1) obtain field data on working conditions, workload with a hand tool and type of equipment used, 2) determine the parameters of vibration hand tool that is widely used, 3) modeling and making fluidic damper glove, perform the test comparison of the use and without the use of glove, 4) glove on field trials that have been surveyed. In the period of the study for 2 years, each parameter vibration hand tools frequently used can be measured in the laboratory. Tests conducted to determine the vibration of the arms that operate hand tools. Fluidic damper glove designed to dampen vibrations in the arm so that its effect on health problems can be reduced.

Reliability Assessment of Steel Bridges for Specialized Hauling Vehicles

2019 ◽  
Vol 2673 (12) ◽  
pp. 391-403
Author(s):  
Peng Lou ◽  
Dongjian Gao ◽  
Hani Nassif ◽  
Mula Reddy
Keyword(s):  
Safety Margin ◽  
Steel Bridges ◽  
Live Load ◽  
Load Rating ◽  
Truck Traffic ◽  
Reliability Indices ◽  
Weigh In Motion ◽  
Load Factors ◽  
Load Effects ◽  
Existing Bridges

Specialized hauling vehicles (SHVs) are short heavy trucks within the legal weight limits but induce higher load effects than routine commercial loads. The Manual for Bridge Evaluation (MBE) adopted a series of single-unit trucks (SUs) to represent this type of vehicle. However, the SUs were introduced without rigorous reliability-based analysis due to the lack of data on SHVs. With the availability of vast amounts of data on weigh-in-motion (WIM) truck weights and configurations, the reliability of steel bridges under the SHVs should be evaluated in a more robust and quantitative manner. Through the utilization of WIM data, the authors quantified the SHVs in terms of percentages of SHVs among all truck traffic, daily average counts of SHVs, and number of axles. The gross vehicle weights (GVWs) and typical configurations of SHVs were investigated. In addition, their load effects were determined and normalized by the corresponding SUs. The maximum live loads corresponding to a return period of 5 years were also extrapolated using normal probability paper (NPP). To evaluate the effectiveness of current load-rating procedures for SHVs, the authors investigated the relationship between the load-rating factors and the corresponding reliability indices for existing bridges using the developed live load parameters based on the WIM data. Results indicated that the current live load factors were not able to provide a uniform and appropriate reliability index at different average daily truck traffic (ADTT) scenarios. This paper thus proposes new live load factors and weight adjustments of SU trucks to provide an adequate and uniform safety margin for the evaluation of steel bridges.

Probabilistic fatigue and fracture analyses of steel bridges

2003 ◽  
Vol 25 (3) ◽  
pp. 245-262 ◽  
Author(s):  
M.S. Cheung ◽  
W.C. Li
Keyword(s):  
Steel Bridges ◽  
Fatigue And Fracture
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