Structural Engineering

Primary Graduate Student: Sai Theja Medi (MSCE’19)
Project Advisor: Keith Kowalkowski, PhD, PE, SE

Lawrence Tech was contracted by Nederveld Inc. to perform eighteen (18) tests on “irregular” hanger connections that have been constructed in General Motors (GM) automotive plants. In the plants, there are several hangers than are connected to header steel. The work was primarily performed the research assistant Sai Theja Medi (India) and supervised by the primary investigator, Dr. Keith Kowalkowski.

Header steel is a term used in assembly plants for steel members that are added after the main structural building is constructed and usually connect to the bottom chord of existing steel trusses. Header steel is typical designed for special applications dependent on the operations performed on the floor in the area. It often hoists added platforms, conveyors, etc. Hangers are connected to the header steel to directly connect to loads below and are subjected to axial tension. This project focused on connections specifically from the hangers to the header steel and the end connections of the header steel as it connects to the bottom chord of trusses part of the main structural steel framing. In this project, the hangers were single angle sections and the header steel members were channel sections. Dissimilar from most standard connections, the hangers were not bolted or welded director to the header channel sections. Instead, the connections were “wrapped” around the channel sections, which induced flexural, shear and torsional loading on the channel sections.

The results of the research investigations saved GM and subcontractors a significant amount of money. Prior to the tests being performed, engineers considered removing a significant amount of header steel in multiple plants, since individual capacities were uncertain. The research resulted in recommendations for allowable loads for several connections that exist in the field.

Primary Graduate Student: Javier Rodilla (MSCE’20)
Project Advisor: Keith Kowalkowski, PhD, PE, SE

A research project was funded by the American Institute of Steel Construction (AISC) entitled “Analysis and Design of Eccentric Stiffeners Part of Moment Connections to Column Flanges”. The research project included both experimental and analytical work. All work was performed with the primary investigator, Dr. Keith Kowalkowski, and graduate student Javier Alvarez Rodilla (Spain). The experimental structural engineering tasks was assisted by an additional graduate student, Sai Theja Medi (India). Digital Image Correlation (DIC) was supervised by Dr. Xin Xie (former faculty member of the Department of Mechanical Engineering) and student assistants Himanshu Kolambe (India), Abhijit Bothe (India), and Chukiang Fong-Ramirez.

In the experimental investigations, forty column specimens were tested. Three different test methods were used: (1) single compression in which a downward force was applied to the top flange of a column specimen from a hydraulic actuator, (2) double compression in which a downward force was applied to the top flange of a column specimen but with a support directly adjacent and at the bottom flange, and (3) single tension in which an upward force was applied to the top flange of a column specimen. In a group of four specimens, one specimen was tested without stiffeners, one was tested with concentric stiffeners, one was tested with stiffeners at a low eccentricity and one was tested with stiffeners at a high eccentricity. Relationships were derived between the magnitude of eccentricity and the “Effective Stiffener Capacity”.

Finite element models were developed for larger column sizes more regularly used in practice. All test methods included the column sizes W14X68, W14X120, W14X176, W14X233, W24X131, and W24X229. The finite element models were developed and analyzed by Javier Alvarez Rodilla and the influence of stiffener eccentricity was evaluated in a similar way as for the experimental results. The research collectively resulted in recommendations for determining the capacity of eccentric stiffeners in comparison to that of concentric stiffeners by using a formula that considered the amount of eccentricity and the flange thickness of the wide flange beams. Two papers were authored by Dr. Kowalkowski and Mr. Alvarez Rodilla.