A Study on the Ultimate Strength of Thin Cylindrical Tubes under Static or Quasi-static Loading.

Research Project

Project/Area Number	60550320
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	土木構造
Research Institution	Nagoya University
Principal Investigator	USAMI Tsutomu Nagoya University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (50021796)
Co-Investigator(Kenkyū-buntansha)	YAMADA Kentaro Nagoya University, Faculty of Engineering, Associate Professor., 工学部, 助教授 (50109310) MIZUNO Eiji Nagoya University, Faculty of Engineering, Research Associate., 工学部, 助手 (80144129) ITOH Yoshihito Nagoya University, Faculty of Engineering, Research Associate., 工学部, 助手 (30111826) FUKUMOTO Yuhshi Osaka University, Faculty of Engineering, Professor., 工学部, 教授 (10023045)
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥2,000,000 (Direct Cost: ¥2,000,000) Fiscal Year 1986: ¥300,000 (Direct Cost: ¥300,000) Fiscal Year 1985: ¥1,700,000 (Direct Cost: ¥1,700,000)
Keywords	Pipe / Compression member / Ultimate strength / Initial imperfection / Numerical Analysis / 実験
Research Abstract	This project is to determine theoretically and experimentally the load carrying capacity of short fabricated cylindrical tubes under compressive loading. The tests were carried out on 10 fabricated pipes in which 8 were for compression tests and 2 were for residual stress measurements. In addition, initial out-of-straightness(OOS) and out-of-roundness(OOR) were measured for all the specimens. From the experiment, the following were observed: (1)Initial OOS and OOR are well below the specified tolerances of ECCS and API. (2) Measured residual stresses are similar in shape to those in a reference and the maximum compressive residual stress was about 20% of the yield stress. (3)Observed average stress-strain curves of test specimens with the same radius/thickness ratio are similar in shape up to the maximum load, but become different after the peak load, i.e., steeper descending part was observed for longer specimen. (4)Observed ultimate strength may be well predicted by the basic strength formular of cylindrical tubes specified in the current Japanese highway bridge specification. Theoretical study was also conducted by applying the Dynamic Relaxation Method (DR method). A computer program has been developed to make an elastic-plastic large displacement analysis of cylindrical shells. The following are obtained from the study: (1)It is possible to reduce the number of iterations by determining iteration parameters from the maximum and minimum eigenvalues of the stiffness matrix. (2)The computed ultimate strengths of cylindrical shells with initial imperfections fall generally between the strengths predicted by the basic strength formulas of the Japanese highway bridge specifications and ECCS.