Please use this identifier to cite or link to this item: https://hdl.handle.net/11681/5578
Title: Strain gage instrumentation of steel piles in snow
Authors: Sohlberg, Erik T.
Keywords: Steel piles
Piling
Pile driving
Strains
Strain gages
Stresses
Measurements
Snow
Snow construction
Stress analysis
Instruments
Equipment
Camp Century, Greenland
Publisher: Cold Regions Research and Engineering Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical report (Cold Regions Research and Engineering Laboratory (U.S.)) ; 152.
Description: Technical Report
Summary: This report describes instrumentation for a preliminary test of friction piles in snow. Two 30-ft. H piles we re fitted with strain gages and driven in snow. Several different types of resistance strain gages were distributed along the centerline of the web of the piles on both sides so as to reflect only axial strains. They were bonded with epoxy resin cement except for a few welded gages, and were water proofed with an oil wax or an epoxy cement. The wiring and gages themselves were mechanically protected by welding a 2 x 2 x 3/16 in. angle over them on both sides of each pile. Dynamic measurements of strain we re made during driving by means of a dual beam oscilloscope fitted with a Land camera. The oscilloscope was triggered from a gage near the top of the pile through a one-shot thyratron trigger circuit especially constructed for the purpose. This arrangement prevented reverberations of the energy pulse up and down the pile from retriggering the scope and confusing the strain wave photographs. During a particular monitored blow, a peak dynamic stress of 13,260 psi was measured in the larger of the two piles. The larger pile was an 8 x 8 WF 35 section and the smaller was a 6 x 6 M 20. Both were 30 ft. long. The piles were driven in September 1962 and left unloaded until the summer of 1963. A switch box was constructed and used during static tests. This box allowed a forward, reverse, and calibration reading to be taken at each gage position in a minimum of time. Analysis of some of the voluminous static load data taken in the 1963 season shows that immediately after the load was applied the upper section of the pile took most of the load. After the load was held in place for several weeks, each unit length of the pile had accepted an equal share of the total load. The 8 x 8 WF 35 pile was loaded to 40,000 lb and the 6 x 6 M 20 to 28,000 lb. Immediately after removal of the load, the upper section of the pile was relieved but most of the loaded strain remained in the bottom section. A few days later the entire pile b.ec arne strain relieved. Analysis of both the static and dynamic data shows the capabilities of the instrumentation techniques used. Complete strain versus depth profiles were obtained in spite of the low level of the strains involved. For this reason it is recommended that in future work of this type similar measuring instruments be used. Welded resistance strain gages and oil wax moisture protection were the most satisfactory. Complete details of each step of the instrumentation are included in appendixes.
Rights: Approved for public release; distribution is unlimited.
URI: http://hdl.handle.net/11681/5578
Appears in Collections:Technical Report

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