International Concrete Abstracts Portal

Editors: Gustavo J. Parra-Montesinos and Mary Beth D. Hueste

Professor James (Jim) K. Wight has been one of the most remarkable researchers and educators in the field of reinforced concrete structures in the past several decades. Jim’s engineering career started at Michigan State University, where he obtained his BS and MS in 1969 and 1970, respectively. After completing his MS studies, he went on to the University of Illinois at Urbana-Champaign to pursue doctoral studies under the supervision of Professor Mete A. Sozen, obtaining his PhD in 1973.

It was while a student at the University of Illinois that Jim Wight made his first major contributions to the field of behavior and design of reinforced concrete structures, particularly under earthquake excitations. He was likely the first to study the phenomenon of shear strength decay in reinforced concrete columns during large shear reversals. He also identified and explained the “disappearance” of the yield plateau in longitudinal reinforcing bars of flexural members subjected to moment gradient. Referring to this, Mete Sozen later said that had Jim been in the field of Physics, he would have won the Nobel Prize.

In 1973, Jim Wight joined the faculty at the University of Michigan. In a career that has spanned over 40 years as a Professor of Structural Engineering, Jim has exemplified excellence in teaching, research, and professional service. Jim has made enormous contributions to the field of behavior and design of reinforced concrete members, including beam-column and slab-column connections, structural walls, and deep beams. Much of his research has led to key advances in the safety and performance of reinforced concrete building structures during seismic events. Further, he has advised over 30 PhD students, several of whom are currently faculty members at major research universities. Jim has also contributed to the education of thousands of structural engineers as co-author (with Professor James MacGregor) of the widely used textbook Reinforced Concrete – Mechanics & Design. He has made significant contributions to the development of design guidelines and codes for reinforced concrete structures as Chair of ACI-ASCE Committee 352 in the early 1980s and of ACI Committee 318 during the 2002-2008 Code cycle. His dedication and involvement in the American Concrete Institute includes the distinction of serving as President in 2012-2013.

It was therefore with great joy that a group of researchers and practicing engineers who, over the years, had the opportunity to interact closely with Jim, decided to honor his illustrious career with a series of technical sessions and this Special Publication. Fifteen presentations, distributed in three sessions named “James K. Wight: A Tribute from his Students and Colleagues,” were given at the 2014 ACI Fall Convention in Washington, DC. All speakers consisted of students of Jim’s; colleagues in ACI technical committees; and his doctoral advisor, Professor Mete A. Sozen. The sessions were well attended by former students, academicians, researchers, and practitioners. A room-packed reception and a dinner were also offered in honor of Jim Wight. This Special Publication contains 12 papers related to the presentations made during the three technical sessions in Washington, DC. Also, Professor James O. Jirsa contributed with his personal perspective of Jim Wight’s contributions to the design of beam-column joints.

This Special Publication is but one small token of the appreciation and gratitude that all those involved have for Jim Wight. He has been a mentor, role model, and a source of inspiration to many, as well as an example of honesty, integrity, dedication, and unselfishness. Professor James K. Wight is, without a doubt, a true educator in the broadest sense of the word. We all feel very grateful to have had the opportunity to honor such an outstanding individual.

A Brief Overview of the Development of Design Guidelines for Joints in Reinforced Concrete Structures and Dr. James K. Wight’s Contributions to ACI 352

Among his many achievements, Professor Wight’s observation and explanation of the irrelevance of the linear-plastic model for the moment-curvature relationship of a structural element subjected to a moment gradient (rather than constant moment) along its span stands out as one of his best contributions and one that will stand the test of time.

The beam-to-column connection regions of reinforced concrete frames are generally considered to be rigid and the inelastic behavior of the joint is not considered both in analysis and design applications. However, joint shear distortions that are observed under earthquake loading have a major contribution to the story drift of a structure. Even if the story drifts are not significant, a collapse mechanism may be formed due to extensive deformations in the beams, columns or connection regions. Therefore, the seismic performance of each member should be investigated independently from that of the frame. In this experimental research, the seismic performance of beam-to-column connection regions of a 1/2–scale three-story three-bay RC frame is studied. Hybrid (pseudo-dynamic, PsD) testing method is utilized and earthquake excitations with increasing intensities are applied sequentially to the frame. The reinforced concrete moment resisting frame building is designed following the code requirements, however a joint mechanism is formed under high intensity seismic loads. The joint shear distortions are observed to be significant even for the basic safety earthquake level, when soft soil conditions are present. In this paper, the seismic performance of the frame and individual member responses are discussed for earthquake loadings with different probabilities of exceedance. The interaction between the beam end rotation and joint shear distortion and the effect of connection performance on the seismic behavior of the frame are explained in detail.

Some implications of using high-strength concrete and steel materials in reinforced concrete frame members are discussed in terms of both flexural design and behavior. Through an example, it is demonstrated that the computed sectional curvature is highly sensitive to the choice of rectangular stress block used to model compression zone stresses of high-strength concrete. Comparison of various models suggests that the use of the stress block model defined in the ACI Building Code tends to overestimate curvature for concrete strengths exceeding 12 ksi (83 MPa). In addition, recent test data are presented for flexure-dominated concrete members reinforced with high-strength steel bars. The effects of replacing Grade 60 (410) flexural reinforcement with Grade 100 (690) steel on deformation capacity, stiffness, and strength are examined. Test data support the viability of using Grade 100 (690) longitudinal reinforcement to resist loads that induce force-displacement response well into the nonlinear range.