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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Civil and Environmental Engineering

First Advisor

Nadim I. Wehbe


An experimental research study was conducted at South Dakota State University to evaluate the composite action exhibited by steel box truss towers in torsion. Four tower configurations were constructed and tested. Strain, rotation, and load measurements were used to assess the performance of each configuration. The specimens were 32ft-6in long and were fixed at one end as a cantilever. Composite action between adjacent trusses was developed with bolted angle connections spaced at 6ft-6in intervals along the specimens. The first configuration consisted of a tower segment with no cross bracing. The second configuration consisted of a tower segment with end cross bracing only. The third configuration consisted of a tower segment with middle cross bracing only. The fourth configuration consisted of a tower segment with both end and middle cross bracing. A torsional moment was applied at the free end of the specimen. Loading was applied continuously until the actuator capacities were reached. This study includes an introduction, literature review, test specimen description and setup, testing results of the specimens, analysis of the experimental results, and conclusions and recommendations. Experimental results were analyzed to determine the percent composite action displayed by each configuration. The performance of a partially composite tower shown in testing in relation to a fully composite tower is referred to as its composite action. Experimental results indicated that bolt slip in the connectors was initiated at a certain applied moment, above which the specimens displayed a reduced stiffness. The configuration with no cross bracing was the least stiff configuration. The configuration with middle cross bracing only was the second least stiff configuration. The configuration with end cross bracing only displayed the same stiffness as the configuration with end and middle cross bracing. In the finite element analysis, each configuration was modeled and calibrated. Effective reduction factors were found for range of applied moments which can be used in design to account for bolt slip effects.

Library of Congress Subject Headings

Towers -- Design and construction -- Evaluation
Trusses -- Design and construction -- Evaluation
Steel, Structural


Includes bibliographical references (pages 109-110)



Number of Pages



South Dakota State University


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