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Bolting Research Studies

Technology validated by research!

Direct Tension Indicators (including the TurnaSure DTI) have been the subject of numerous American and international bolting research studies over the past three decades. We have gathered dozens of them here for you.

Indicadores Directos de Tensión

2012 Construcción Metálica Ed.16, Colombia
Rodrigo Delgado Charria, author of this article, designs and builds Steel buildings and industrial complexes in Colombia since 1986. He is a member of AISC, president of Fedestructuras Valle, former professor of structural design for postgraduate students at Valle University, also taught structural design for architects at Buenaventura University. Rodrigo and his family reside in Cali, Colombia.
A must read for Spanish speakers.

Time Study on Cost Savings using DTIs Compared to Calibrated Torque Wrench Tightening

Recently reanalyzed by Rowan University in New Jersey USA, this study extrapolated data gathered in London England in 1970 by a top consulting engineering firm, a steel fabricator and time and motion consultants, and applied the data to current wage rates. The Calibrated Wrench method was applied as it is used in the EU. The savings in labor cost using DTIs exceed the current cost of DTIs in both the EU and USA.

Lehigh University's Slip Test Report on the TurnAnut DTI

2011 Lehigh University, Pennsylvania

DTI Case Study: Ammonia Offloading Pier

2010 Fator, Arzew, Algeria

Tests for stress relaxation over time

1963 to 1971. Sheffield University, Sheffield, England.

Standard Deviation Comparison Study of the New TurnaSure DTIs vs. Old Through-Hardened and Tempered DTIs

Comparison of Standard Deviation from 250 lots of DTIs From Two Producers, March 2011

Fatigue tests on DTIs

1960s Research conducted by British Welding Research Institute, Abington Hall, Cambridge, England.

Comparison of Tightening Methods of HSFG Bolts

Time trials comparing DTIs with other methods conducted by W.S. Atkins & Partners, Consulting Engineers, P.A. Management Consultants, British Steel, London, England, August 1970.

Study on Bolt Tensions and Long Termed Relaxation after Tightening in Connections with and without DTIs

This study, published by Rowan University in 2014 using structural bolts implanted with ultra sonically monitored chips, shows unequivocally what the bolt tensions remain at after using DTIs with feeler gauge verification compared to some bolts without DTIs

DTI Case History- DTIs Save More the $150,000

Study on DTI use on Power Plant in Nebraska by Bethlehem Steel, Pennsylvania, USA. Dec 1981.

Study discussing influence of load-indicating washers on bolt relaxation in joints subject to high prying forces

Concludes DTIs are a benefit by Dr. J.O. Surtees and M.E. Ibrahim, Leeds University, Yorkshire, England, Published in Civil Engineering Magazine, April 1982.

Transverse Vibration Loosening Characteristics of High Strength Fastened Joints using DTIs

SPS Contract Research, Jenkintown, Pennsylvania, USA. July 1998.

Study on full flattening of Direct Tension Indicators in Shear Connections

by Prof Edwin R. Schmeckpeper, Prof. Richard J. Nielsen, and Guy Gentry, Department of Civil Engineering, University of Idaho. USA. Concludes full flattening of DTIs had no detrimental affect. Published in Engineering Journal of American Institute of Steel Construction. First Quarter 1999.

Impact of Variable Lubricity on Type 325 Structural DTIs

Study showing no change to the new TurnaSure DTIs performance, dry, oiled, or rusty, by Laboratory Testing Inc, Hatfield, Pennsylvania, USA 2000.

Test Report for Accelerated Aging of Weathering Steel Joint using TurnaSure Weathering Steel 7/8" -3 type 325 DTIs

Study concludes DTI prevented rusting inside bolts assembled for unpainted bridges conducted by KTA-Tator, Inc, Pittsburgh, Pennsylvania. USA. Feb 2002.

New Generation Direct Tension Indicators

Article in New Steel Construction magazine, UK describes development of new generation DTIs in USA. Jan-Feb 2004 issue, by Roger Reed, Technical Manager of Thomas William Lench Ltd.

Report using DTIs on seismic isolators

Research report for the National Science Foundation in 1993 on a Slotted Bolted Connection Energy Dissipater design using DTIs and published by The University of California at Berkeley in Steel Tips Magazine.