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.

Comparison of Structural Bolting Assemblies Installed By the Turn-Of-Nut and Direct-Tension- Indicator Methods and Their Respective Reserve Ductility

This Rowan University study demonstrates that fully flattened DTIs are entirely reliable in comparison to traditional methods of bolt tensioning.

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.

Effect of Washer Placement on Performance of Direct Tension Indicators with Curved Protrusions

Reprinted with the permission of the AISC

Lehigh University's Slip Test Report on the TurnAnut DTI

2011 Lehigh University, Pennsylvania

Effect of Washer Placement on Performance of Direct Tension Indicators

2009 Rowan University, New Jersey

DTI Case Study: Ammonia Offloading Pier

2010 Fator, Arzew, Algeria

Preload Measurement and Comparison of Structural Bolts sets installed in Steel Connections with and without Direct Tension Indicators

2007 Applus, Barcelona, Spain.

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.

Bolting Research Studies