Shojiro Motoyui

Seismic Retrofit Using Rocking Walls and Steel Dampers

A retrofit system of prestressed concrete rocking walls and steel dampers is used to control the seismic damage mode and increase the strength and energy dissipating capacity of an 11 story steel reinforced concrete frame in Japan. Important details of the retrofit design are introduced. The seismic performance of the structure before and after the retrofit is evaluated through extensive nonlinear time history analysis. Results show that the rocking system can significantly reduce both the seismic responses to different earthquake ground motions and their scattering. This makes the damage mode and the seismic performance of the retrofitted building more predictable, leading to a possibility of more reliable performance-based seismic design.

Ceiling Anchorage Loads during Shake Table Tests of a Full-Scale Five-Story Building

This paper documents tests conducted to assess anchor loading characteristics and distributions over a suspended ceiling before, during, and after a series of simulated earthquakes. Miniature force-measurement devices were installed on a 4.5 by 6.5 m section of gypsum board ceiling located in a full-scale five-story building. The building was subjected to a series of four scaled earthquakes until failure of the ceiling occurred. The test results show that the ceiling-to-slab acceleration amplification was a factor of about 6.4 for horizontal accelerations and 15.0 for vertical acceleration immediately prior to failure of the ceiling. Variation of the peak axial anchor forces across the ceiling under earthquake loading was significant; the maxima exceed the mean value by a factor of up to 3.8 times. Rainflow counting of axial anchor load cycles is used to provide cycling demand for both the linear and nonlinear response of the ceiling.

Identification of Dynamic Characteristics of a Historical Church in Armenia Using Microtremor Survey Technique

Historical Churches in Armenia may have many experiences of earthquake ground motion. Thus, some of them have been damaged partially or severely. We had carried out the microtremor survey at a historical churches, which is Cathedral at Etchimiadzin around 5th century, to identify the dynamic characteristic. Four sensors are used simultaneously for the observations and modes of vibration are identified from some methods such as the Fourier spectrum and coherence function, and frequency domain decomposition (FDD) technique.

A Proposal of Generalized Plastic Hinge Model for the Collapse Behavior of Steel Frames Governed by Local Buckling

Publisher Summary It is necessary to evaluate the true safety of structures by using an analytical method, which can simulate the behavior to collapse. A collapse of steel frames is due to local buckling and fracture. However, this chapter depicts a generalized plastic hinge model for the collapse behavior of steel frames governed by local buckling. The development of plastic displacements conforms to associate flow rule. This chapter considers that the strength surface for Zone I is moving parallel to the initial full yield surface according to equivalent strength parameter. The relationship between equivalent strength parameter and equivalent plastic displacement parameter is obtained from the results calculated with finite element method. The relationship between hysteresis characteristic under monotonic loading and that under cyclic loading is developed. However, structural member behaves without shear yielding and shear buckling.

PLASTIC LOCAL BUCKLING STRENGTH OF HIGH STRENGTH STRUCTURAL STEEL TUBES

The objective of this paper is to examine the structural properties, namely the plastic local buckling strength, the deformation capacity and the slope of strength inferiority of high strength structural steel tubes, by the stub column tests and the nonlinear FEM analysis. The differences of buckling behaviors between the annealed tubes and not-annealed ones are also examined. The examined tubes are high strength steel tubes frequently used for the structural members in large structures with the radius-to-wall thickness ratio (R/t) for 8.0 to 35.0 and the yield strength of 55.0 to 80.0 kg/mm2. As the material properties, the yield strength and the type of the stress-strain relation such as the round-house type or the bilinear one were chosen. We also paid attention to the distribution of the residual stresses due to fabrications and to the difference of the properties between the annealed tubes and the not-annealed ones. The FEM analysis using the axi-symmetric shell element can take into account both the geometrical and the material nonlinear effects. As the results of these analysis and tests, the differences of the strength characteristics are clearly recognized from the load-displacement curves. It is noted that the annealed tubes may have less buckling strength and deformation capacity than the not-annealed ones when the radius-to-wall thichness ratio (R/t) is large.