Sub- Committee Co-Chairs:
Prof. H. Noguchi, Chiba University
Prof. G. Deierlein, Cornell University
The meeting of the RCS committee in Monterey included thirteen participants from Japan, eleven from the United States, and three international visitors. One full day of the meeting was devoted to hearing over twenty presentations summarizing experimental and analytical research, development of design criteria, and recent construction applications of RCS systems. As summarized below, there are seven active projects in the US that are related to the area of RCS structures. While most of the projects in Japan are nearing completion, major efforts are still underway in both the US and Japan to develop design criteria for composite RCS frames and to exchange research findings. Collaboration over the past year has been greatly facilitated by several Japanese researchers who spent extended visits in the US.
List of Participants
|Hiroshi Noguchi||Chiba University|
|Shin-ichi Iizuka||Nishimatsu Corporation|
|Eiji Ishii||Taisei Corporation|
|Hidehiko Itadani||BRI (Ohmoto-Gumi Co.)|
|Yasuhiko Masuda||Obayashi Corporation|
|Mikio Mizuta||Obayashi Corporation|
|Yasushi Nishimura||Osaka Institute of Technology|
|Noboru Sakaguchi||Shimizu Corporation|
|Kunio Sugihiri||BRI (Mitsubishi Cons. Co.)|
|Kazuhiro Uchida||Fujita Corporation|
|Kenji Yoshimatsu||Kumagai -Gumi Co. Ltd.|
|Gregory Deierlein||Cornell University|
|Hassan Astaneh||Univ. of California, Berkeley|
|Joe Bracci||Texas A&M University|
|Dan Frangopol||Univ. of Colorado at Boulder|
|Roberto Leon||Georgia Tech.|
|Walter P. Moore Jr||Texas A&M University|
|Enrico Spacone||Univ. of Colorado at Boulder|
|Chia-Ming Uang||Univ. of California, San Diego|
|Don White||Georgia Tech.|
|James Wight||Univ. of Michigan|
|Yan Xiao||Univ. of Southern California|
|J. Bouwkamp||Tech. Univ. of Darmstadt, Germany|
|Oan Chul Choi||Soongsil Univ., Seoul, Korea|
|K.C.Tsai||National Taiwan University|
< Introductions by sub-committee co-chairs
Deierlein - Welcome and introduction of US participants.
Noguchi - Introduction of Japanese participants and research progress in Japan
< Database of RCS test data and design standards
Sakaguchi, Yoshimatsu, Masuda and Iizuka et al. Review and evaluation of RCS beam-column connection design models (strength equations, stress transfer models and restoring force characteristics) using data compiled in an electronic database with results from 450 RCS connection tests.
Kuramoto and Deierlein Summary of work to develop English translations of Japanese database of connection test data and AIJ report with design models for beam-column connections. Reports will be available by the end of 1997.
< Tests of beam-column connections
Moore/Bracci - Presentation on tests of RCS beam-column joints with concrete floor slabs. Two tests have been completed and four more are planned for testing within the next year.
Wight - Presentation on test results of five exterior RCS beam-column joints, including one specimen made with fiber reinforced concrete. Three to five additional tests are being planned to look further into the use of fiber reinforced concrete and the repair/rehabilitation of damaged connections.
Uang - Presentation on plans to test two exterior and two interior RCS joints between steel beam and composite columns with and without steel jackets in the joint region. Some joints will utilize reduced beam section (dogbone) concept.
Y. Nishimura - Experiments on stress transfer mechanisms in through beam type joints. Description of the superposition of inner (bearing) and outer panel (torsional) strength. Effect of lateral reinforcement on the joint torsional strength is similar to that described by equations given in the ASCE design guidelines for RCS joints. The shear resisting mechanisms change gradually from an inner panel to an outer panel according to the reinforcing levels in the joint.
H. Itadani/ K. Sugihiro - Results of 3D beam-to-column joints tested under bi-directional loading at the BRI. Some discussion on how the 3D-loading path was developed based on the observed loading orbits observed from the Kobe earthquake. Results to date show that 3D test results are not remarkably different from 2D tests if loading orbits follow a line, thus tending to verify the accuracy of existing models developed based on 2D tests.
< Analysis of beam-column connections
K. Uchida Described tests to investigate and analyze bond between steel plates and concrete. Work was conducted while Uchida was in residence at the Univ. of Texas at Austin.
H. Noguchi Nonlinear 3D FEM analyses of RCS joints. Results show that the ASCE design equations give conservative joint strengths (approx. 10 to 15% conservative). The FEM analyses utilize interface elements for crack opening/closing and slip between steel plates and concrete at critical locations between the steel beam flanges and surrounding concrete.
< Test and analysis of RCS frames
Spacone/Frangopol - Presentation on analytical modeling of frames with composite beams including the effects of material nonlinearity in steel and concrete and bond/slip between the two. Two models were used, one with continuous shear connectors and one with concentrated shear springs elements, and differences between them were described.
Deierlein - Presentation on analysis of RCS frames and review of seismic design issues and criteria. Review of preliminary push over and inelastic time history (dynamic) analyses of RCS frames with comparisons to frame tests conducted by Tokyu Corporation. Future plans include: (1) further verification analyses using other frame tests conducted in Japan, (2) systematic frame analysis/design studies to evaluate seismic design criteria, and (3) development of improved frame analysis/design criteria.
Y. Nishimura- Described a 2D RCS frame test to be conducted in November 1997 at the Osaka Institute of Technology.
K. Uchida/ H. Noguchi Discussion of 3D FEM Analyses of an RCS frame that include detailed continuum modeling of the beam-columns and connection (joint) regions. Nonlinear bond behavior is shown to be a dominant effect at the boundary of joint and column.
< Research plans for US beginning in 1997
Leon/White Discussion of plans for testing and analyses of composite partially restrained frames consisting of composite beams and steel columns. Some of the testing work will be coordinated with related SAC investigation on bolted frame connections.
Xiao Discussion of plans for testing encased composite columns emphasizing applications with high strength concrete and shear critical behavior.
Astaneh Plans for testing composite action in simple shear connections between composite beams and steel columns. These tests are part of the SAC Joint Venture Project and were presented at the U.S.-Japan meeting since they relate to the work of the RCS group.
< Visitor presentations
K. C. Tsai (Taiwan) Described recent tests of eight RCS beam-column joint specimens with through beam type connections and various reinforcing details. Column compression failure was observed near the joint.
Jack Bouwkamp (Tech. Univ. Darmstadt) Reviewed the design of a 3D composite frame and testing of 2D frame specimens with composite beams and steel columns.
< Video presentations to introduce recent applications of RCS systems in Japan
Taisei Corporation - Eiji Ishii introduced an RCS system called the UNIQUE system composed of RCS framing in one direction and RC framing in the perpendicular direction. A case study was presented of a four-story building that was built in 16 months.
Kumagai-Gumi Corporation - Kenji Yoshimatsu presented two types of RCS systems: one type has rigid joints in one direction and pin joint in the perpendicular direction, and the second type is constructed using steel erection columns. Case studies were presented on each system, the two-story Naruto shopping center and the Higashitotsuka shopping center.
< Design guidelines
I. Nishiyama Overview of a new initiative of the Ministry of Construction to develop design guidelines that permit the use of both current seismic practice and new performance-based methods.
Summary of Progress and Near Term Plans
Beam-Column Connection Testing: Including work in-progress, seventy-one RCS beam-column joint specimens will be completed as part of the U.S.-Japan program. These add to a database of over 400 tests of RCS joint subassemblies previously tested in Japan and 35 subassemblies previously tested in the US. In spite of the large number of previous tests, those conducted as part of the U.S.-Japan program are valuable in that they focus on parameters that have not been studied in prior tests, e.g., 3D joint details and loading, interaction of the floor slab and the beam-column joint, external joint details, and use of fiber reinforced concrete.
It is recommended that there should be more emphasis on sharing/exchange and critical review of test reports/papers between the Japanese and US researchers. An important mechanism for such sharing is the electronic database of connection test data that has been compiled by the BCS in Japan and will soon be available to researchers in the US from Cornell University. During the next year, US and Japanese researchers should incorporate new test data into this common database.
Member Testing: To date there has been little or no member testing done as part of the U.S.-Japan initiative for RCS structures. However, Xiao and Anderson (of USC) have plans to conduct tests of encased composite SRC columns made with high strength concrete and to investigate shear-critical behavior.
Frame Testing: RCS frame tests have been conducted in Japan by the Tokyu Corporation (1 test) and the Nishimatsu Corporation (2 tests). One additional RCS frame test will soon be completed at the Osaka Institute of Technology under the direction of Prof. Nishimura. No tests have been conducted or are currently planned in the US.
Analysis Model Development/Verification: The following is a summary of efforts to develop, implement, and test new analysis formations for the inelastic analysis and design of RCS systems and components:
Theme Structures: Japanese researchers associated with JSCA have developed and analyzed trial designs for six and twelve story RCS theme structures using BCJ and AIJ design guidelines and criteria. Researchers at Cornell University are currently developing trial designs for six, twelve, and twenty-four story RCS theme structures based on the 1997 NEHRP Recommended Provisions for the seismic design of composite structures. Designs will be developed and analyzed for various levels of seismicity. Researchers at Georgia Tech will undertake related work for composite PR frames. Other groups in the US whose main emphasis is connection testing (Univ. of Michigan, Texas A&M, and Univ. of California at San Diego) will also be developing some theme structure designs, but with the main emphasis of supporting their research on connection behavior.
Design Models and Criteria: The latest source of design criteria for composite RCS frames in Japan is a set of recommendations prepared by the Architectural Institute of Japan in 1994. This document deals primarily with the design and detailing of RCS beam-column joints, and it has recently been translated into English by Kuramoto while he was in residence at Cornell University. The Japanese BRI is currently leading an effort to develop a more extensive document on RCS frame design, and a first draft of this is expected to be completed in March 1998. It is hoped that Kuramoto (of the BRI) can develop an English translation of this document with the editorial assistance of US researchers.
In the US, design criteria for RCS frames are available from several sources. The 1997 editions of the NEHRP Recommended Provisions and the AISC Seismic Provisions (Part II) include general seismic loading and design/detailing criteria for composite structures. Additionally, a report published by the composite structures committee of ASCE in 1994 (Jl. of Struct. Engrg. in Aug. 1994) includes detailed design models and guidelines for RCS beam-column connections. It is anticipated that US researchers involved in the U.S.-Japan Program will participate in forthcoming initiatives within ASCE, AISC, and ACI to develop improved and more comprehensive design criteria for RCS frames.
Recommendation for Future Work
The following is a summary of areas where further research is needed to facilitate the design and use of composite RCS frames in regions of moderate- to high-seismicity (listed roughly in order of priority):
Research Dissemination and Collaboration
The followings are suggestions for mechanisms to disseminate research findings of the US-Japan Composite and Hybrid Structures Program to engineers, researchers, and educators in the United States and international community:
< Conferences: Sessions that focus on the U.S.-Japan program are currently scheduled for the following upcoming conferences:
Other future conferences where it may be useful to organize sessions include the following:
- -ASCE Congress 99 (New Orleans)
- -ASCCS-Los Angeles, Spring 2000
- -ACI-Nov. 98 (Los Angeles: Constructability for Seismic Regions)
- -EERI-Annual meeting 99 or 2000
- -WCEE 12-New Zealand 2000
- -AISC Annual Conf.- 99 or 2000
< Journals: It is suggested a dedicated issue on the U.S.-Japan Program be published in one or more engineering journals over the next few years. A target submission date of January 1999 would be a good time to summarize Japanese research that has been completed and US research that is near completion. The following is a suggestion of possible journals for publication: Engineering Structures, Journal of Const. Steel Research, EERI Earthquake Spectra, ASCE Sruct. Journal, ACI SP, Earthquake Engineering and Structural Dynamics, AIJ Struct. Div. Journal (in Japanese with summary in English).
< Web site US researchers are encouraged to publish web pages to summarize recent progress on their work and to facilitate sharing of information. In Japan, researchers can post web-page updates through coordination with Prof. Noguchi who is maintaining a web site at Chiba University. It is emphasized that these web sites must be kept current (i.e., frequently updated) to be of interest and use to other researchers.