International Concrete Abstracts Portal

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International Concrete Abstracts Portal

Showing 1-10 of 14 Abstracts search results

Document: 

SP311

Date: 

September 28, 2016

Publication:

Special Publication

Volume:

311

Abstract:

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.


Document: 

SP311-13

Date: 

September 1, 2016

Author(s):

Luis E. García, Mete A. Sozen, Anthony Fiorato, Luis E. Yamín, and Juan F. Correal

Publication:

Special Publication

Volume:

311

Abstract:

On October 12, 2013, a 27-story building collapsed in Medellín, Colombia, with no apparent evidence of vertical or horizontal overload. The building was shaped in plan as a circular arc whose gravity load resisting structure can be described as a three-dimensional structural concrete moment resisting frame consisting of columns and a grid of beams running in both radial and tangential directions that meet at the vertical structural member locations. The building structure was designed using the Colombian NSR-98 Code1, which is based on the ACI 318-95 Code3. An assessment of the structure, as built, was performed by the Universidad de los Andes, Bogotá, Colombia. Material samples of concrete and reinforcing bars were secured and tested for compliance with the materials properties specified in the construction documents. An evaluation of the strength of the structural members as built was performed and a comparison with the gravity load demands was performed. This evaluation identified a strength deficiency of the vertical supporting elements of the structure. The driving reason for the collapse of the structure was that the selfweight of the structure resulted in axial loads that were comparable to the nominal axial capacities of the columns. This was considered the root cause of the sudden collapse of the building with no apparent external factors.


Document: 

SP311-12

Date: 

September 1, 2016

Author(s):

Mohammad R. Ehsani

Publication:

Special Publication

Volume:

311

Abstract:

Since the late 1980s, FRP products have seen increased use in repair and strengthening of concrete structures. The traditional technique is referred to as wet layup where carbon or glass fabric are saturated with epoxy in the field and applied to the structure. In this paper I present several new products that I have developed in recent years. One is very large pre-cured carbon or glass laminate sheets that can be used to repair columns, piles underwater, pipelines, etc. The other is a honeycomb-FRP combination that allows construction of lightweight stiff elements. This product can be used to build pipes that can serve as free-standing elements or in slip-lining repair of deteriorated culverts and pipes. These products can also be used as stay-in-place forms for repair of seawalls, large piers and the like. Examples of field applications are also presented.


Document: 

SP311-11

Date: 

September 1, 2016

Author(s):

A.E. Naaman

Publication:

Special Publication

Volume:

311

Abstract:

This paper provides a brief overview of a project comprising several parts, carried out in collaboration with Jim Wight and a number of graduate students over a period of about fifteen years, starting in the mid 1980’s. The project focused on the effects the addition of fibers can have on the performance of reinforced concrete joints. Lessons learned from early “non-success” and subsequent successes achieved are described. Although details of the effects of fiber reinforcement on the joint behavior under monotonic and cyclic loading such as load carrying capacity, hysteretic moment-rotation response, strength and stiffness degradation, shear resisting mechanisms, and absorbed energy are left to the references cited, a key observation related to the hysteretic energy dissipated is emphasized. It is observed in particular that not all fibers provide equal benefits and the fiber reinforcing parameters must be carefully selected in order to achieve superior results. Two important factors are further stressed: the need to achieve a fiber reinforced concrete composite that is strain hardening in tension (thus likely in shear as well), and the need to develop a postcracking resistance that remains significant even when crack widths exceed the millimeter range.


Document: 

SP311-10

Date: 

September 1, 2016

Author(s):

Jingu Kang and John E. Bolander

Publication:

Special Publication

Volume:

311

Abstract:

This paper presents simulations of early-age concrete behavior, as observed during restrained ring tests. The steel and concrete rings are represented by an irregular lattice model. The evolution of concrete properties, including stiffness and strength, is based on simple models and experimental results. For simulating cases of steel fiber-reinforced concrete, each fiber is explicitly represented within the concrete ring. The simulation results compare well with the experimental data, including readings from strain gages attached to the steel rings. As expected, the addition of short fibers prolongs the time to cracking and reduces crack widths. Viability of the model, as a means for analyzing the early-age behavior of fiber-reinforced concrete, is discussed.


Document: 

SP311-09

Date: 

September 1, 2016

Author(s):

Mary Beth D. Hueste, John B. Mander, Reza Baie, Anagha S. Parkar, Akshay Parchure, J. Michelle Prouty and Tristan Sarremejane

Publication:

Special Publication

Volume:

311

Abstract:

The span length of precast prestressed concrete girder bridges is typically limited to 140–160 ft (43–49 m) due to handling and transportation restrictions on individual girder segments. Span lengths may be doubled by splicing individual girder segments within the spans to form a continuous bridge. A design for a three-span continuous prototype bridge with a 240 ft (73 m) main span and 190 ft (58 m) end spans using modified Tx70 precast concrete girders has been developed. A full-scale experimental study investigated the performance of the prototype bridge details in the splice region under service and ultimate loads. The tested splice connection details were selected to represent critical design parameters. The splice connections performed well under service level loads. However, the lack of continuity of the pretensioning through the splice connection region had a significant impact on the behavior at higher loads approaching ultimate conditions. Moderate ductility was observed for positive bending with low ductility for negative moment. Ideally, spliced connections should be located in regions of low moment demands, away from the peak positive or negative moments. Improved connection behavior at ultimate conditions is expected through enhanced connection details, and several detailing suggestions are discussed.


Document: 

SP311-08

Date: 

September 1, 2016

Author(s):

Enrique Villalobos, Santiago Pujol, and Jack P. Moehle

Publication:

Special Publication

Volume:

311

Abstract:

A wall panel zone is a region in which forces from connecting wall segments are resolved. Four different types of wall panel zones are described. Among these, the case of a wall panel located under an aligned stack of openings in a coupled wall is examined closely. Instances in which such panel zones failed during past earthquakes are presented. Laboratory tests and analytical studies are used to define wall panel zone force demands and capacities. It is shown that simple mechanics and existing design expressions can be used to design wall panel zones against shear failure.


Document: 

SP311-07

Date: 

September 1, 2016

Author(s):

Catherine E. French

Publication:

Special Publication

Volume:

311

Abstract:

U.S. and Japan have had a history of collaboration to mitigate the effects of earthquakes. In 1977, a cooperative agreement set forward a plan to improve the safety of building structures. This plan led to collaborative research over the next several decades that included studies of reinforced concrete, masonry, steel, and precast structural systems. This paper summaries some of the research on structural subassemblages at the University of Minnesota that stemmed from that collaboration. The intent of this paper is to also recognize the contributions provided by Prof. James K. Wight who played a key role in the U.S. Japan collaboration and in the dissemination of the outcomes of research through his leadership at the American Concrete Institute (ACI) including his roles with technical committees including ACI Committees 318 – Structural Concrete Building Code and 352 – Joints and Connections in Monolithic Concrete Structures.


Document: 

SP311-06

Date: 

September 1, 2016

Author(s):

Min-Yuan Cheng, Leonardus S. B. Wibowo, Remy D. Lequesne and Andres Lepage

Publication:

Special Publication

Volume:

311

Abstract:

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.


Document: 

SP311-05

Date: 

September 1, 2016

Author(s):

Remy Lequesne and Gustavo Parra-Montesinos

Publication:

Special Publication

Volume:

311

Abstract:

Early research on the behavior of frame members subjected to reversed cyclic displacements has been reviewed, with an emphasis on the phenomenon of shear strength decay. Information is provided about variables that affect shear strength decay and measures that can be taken to mitigate this phenomenon, which should be of interest to students and structural engineers learning or involved in earthquake resistant design of reinforced concrete structures. Starting in the 1950s, the effect of reversing the loading direction on the flexural response of beams was investigated experimentally. Among other findings, tests showed that single and repeated reversals of load had little influence on flexural strength, but that loading history does influence the deformation capacity and stiffness of members. Although several researchers emphasized the importance of providing adequate transverse reinforcement confining the member core, the role of shear stresses on the response of frame members was not well understood until the early 1970s. Tests by Brown and Jirsa, Wight and Sozen, and Popov, Bertero and Krawinkler, showed that member strength can decay under reversals of load if shear stress demands are large or if inadequate transverse reinforcement is provided. In particular, it was shown by Wight and Sozen that maintaining the integrity of the concrete core through use of closely spaced transverse reinforcement with enough area to resist the entire shear demand without yielding is essential, although not necessarily sufficient. Changes to the ACI Building Code aimed at minimizing shear strength decay were first adopted in 1983 and have remained in subsequent editions of the Code with relatively minor changes.


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