Retrofit Railings for Narrow Through Truss and Other Obsolete Bridge Structures

DOT-FH-11-9418Through truss structures are unique in that the superstructure of the bridge is exposed to impacts from errant vehicles. Effective bridge railings must not only exclude these vehicles from contacting the critical truss members by limiting system deflection, but must also prevent heavy vehicles from rolling over the barrier and contacting a truss member. Complete collapse of truss structures has resulted from automobile impacts as well as heavy vehicle impacts. Two bridge railing retrofit systems were systematically designed and developed in this project. The high performance system is designed to contain and limit vehicle roll of 20,000-lb (9000-kg) buses impacting at 55 mph (90 kmph) and a 15-deg angle. The low service retrofit system contains and redirects a 4500-lb (2000-kg) car impacting at 60 mph (95 kmph) and a 15-deg angle without endangering the truss members behind the retrofit system. Crash tests with vehicles ranging from the bus to an 1800-lb (800-kg) minicompact vehicle were used in the development and evaluation. Design drawings of the bridge rails, bridge attachment detail and approach rail are included in the report

Guardrail-Bridge Rail Transition Designs, Volume I: Research Report

DTFH61-83-C-00028This project was concerned with the transition designs used between w-beam and the guardrail, and rigid bridge rail parapets or wingwalls. State designs submitted to the federal highway administration (FHWA) were rated and designs selected for crash test evaluation. New designs were also formulated and subjected to crash test evaluation. Most of the crash tests were conducted with 4500 lb (2000 kg) cars at 60 mph (95 km/h) and a 25 degree angle. Design drawings are presented along with recommendations for use of these transition designs. Guidelines for transition features are given and design procedures for independent end blocks are given

Characterization of a spark ignition system for flameholding cavities

This paper presents an experimental investigation of a capacitive-discharge spark ignition system designed to promote ignition in CH- and CH-fuelled supersonic combustors. The purpose of this study is the characterization of the ignition system and the plasma generated in the discharge. Schlieren and luminescence imaging are used to visualize the temporal evolution of the spark plasma. Transient voltages and currents across the primary-side of the ignition coil and input-side of the ignition unit are recorded using a high-speed data acquisition system. Three different ignition coils are tested with two different spark plug gaps in an attempt to increase the performance of the ignition system which is evaluated through spatially and temporally integrated luminescence recordings as well as temporally integrated photo diode signals. The data suggests that an increase in performance of a factor of 4-5 over the baseline setup can be achieved. A capacitive ignition lead is used to assess whether or not any capacitance on the coil secondary side can increase the performance of the ignition system. The experiments have also shown that the ignition system parameters can be set to cause sufficient heating of the electrodes to support ignition from a combined glow-spark plug setup

Ancient DNA from lake sediments: Bridging the gap between paleoecology and genetics

<p>Abstract</p> <p>Background</p> <p>Quaternary plant ecology in much of the world has historically relied on morphological identification of macro- and microfossils from sediments of small freshwater lakes. Here, we report new protocols that reliably yield DNA sequence data from Holocene plant macrofossils and bulk lake sediment used to infer ecological change. This will allow changes in census populations, estimated from fossils and associated sediment, to be directly associated with population genetic changes.</p> <p>Results</p> <p>We successfully sequenced DNA from 64 samples (out of 126) comprised of bulk sediment and seeds, leaf fragments, budscales, and samaras extracted from Holocene lake sediments in the western Great Lakes region of North America. Overall, DNA yields were low. However, we were able to reliably amplify samples with as few as 10 copies of a short cpDNA fragment with little detectable PCR inhibition. Our success rate was highest for sediments < 2000 years old, but we were able to successfully amplify DNA from samples up to 4600 years old. DNA sequences matched the taxonomic identity of the macrofossil from which they were extracted 79% of the time. Exceptions suggest that DNA molecules from surrounding nearby sediments may permeate or adhere to macrofossils in sediments.</p> <p>Conclusions</p> <p>An ability to extract ancient DNA from Holocene sediments potentially allows exciting new insights into the genetic consequences of long-term environmental change. The low DNA copy numbers we found in fossil material and the discovery of multiple sequence variants from single macrofossil extractions highlight the need for careful experimental and laboratory protocols. Further application of these protocols should lead to better understanding of the ecological and evolutionary consequences of environmental change.</p

Development of a cost-effectiveness model for guardrail selection. Volume I: technical documentation. Final report.

Federal Highway Administration, Office of Research and Development, Washington, D.C.Mode of access: Internet.Author corporate affiliation: Southwest Research Institute, San Antonio, Tex.Report covers the period June 1975-Dec 1978Subject code: CDISubject code: SCE*CSubject code: WNBSubject code: WW

The Analysis Of Laminated Composite Structures

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