Koichi Kusunoki

A New Structural Health Monitoring System for Real-Time Evaluation of Building Damage

The author has developed a new method for evaluating the seismic performance of existing structures from measured accelerations based on the capacity spectrum method. This involves comparing the performance curve, which is the equivalent nonlinear behavior of a simplified single-degree-of-freedom system, and the demand curve, which is the relationship between the response acceleration and displacement spectra. Two telecommunication towers in Japan were instrumented in 2016, and their responses during several earthquakes have been recorded. This paper discusses the evaluation of damage during two earthquakes. Moreover, parameters such as the predominant period and the required performance are discussed. The proposed system evaluated both towers as being “elastic”. The damping ratios of the towers are very low, which caused the oscillations to continue for more than 5 min after the mainshock of each earthquake because of long-period components of the seismic motion.

Structural Engineering Studies on Reinforced Concrete Structure using Neutron Diffraction

It has been demonstrated in our past studies that neutron diffraction can be an alternative method to conventional strain gauges for measuring the stress distribution along rebar embedded in concrete. The current study investigated the possibility of the bond stress evaluation using neutron diffraction in order to find a further capability of neutron diffraction for the structural engineering study on the reinforced concrete structure. Several peaks appeared in the bond stress distribution measured by neutron diffraction, showing the inhomogeneous bond variation along the embedded rebar. This result suggests that the neutron diffraction technique with high spatial resolution makes it possible to investigate local bond resistance caused by the transverse ribs. The bond stress distribution measured by the neutron diffraction technique is expected to bring detailed understanding of the bond mechanism between rebar and concrete for the reinforced concrete structure. Introduction The reinforced concrete (RC), which is widely utilized for various architectural and civil engineering structures, is well known as a composite structure, in which concrete with relatively low tensile strength and ductility is strengthened by reinforcements such as steel rods (rebars) with high tensile strength and/or ductility. In general, quantitative evaluation of bond resistance between rebar and surrounding concrete is important to discuss the performance of the RC structures [1-4]. In our previous studies, we have investigated the potential of the neutron diffraction technique for the stress measurement of rebar embedded in concrete as an alternative method to the conventional strain gauge. Our first relevant work was carried out using the engineering diffractometer RESA-1 in JRR3 (Japan Research Reactor No. 3), and we demonstrated that the neutron diffraction technique can be a novel strain measurement method for rebar embedded in concrete [5, 6]. More recently, threedimensional deformation behavior of the embedded rebar including the axial and transverse strains was successfully measured under pull-out loading using Time-of-Flight (TOF) neutron diffraction with the engineering diffractometer, TAKUMI in MLF (Materials and life Science Experimental Facility) of J-PARC (Japan Proton Accelerator Research Complex) [7]. Furthermore, it was demonstrated by some application studies using TAKUMI that the neutron diffraction technique is available to assess the bond deterioration due to rebar corrosion and crack generation in concrete [8]. As described above, our previous studies commonly discussed on the bond condition between rebar Residual Stresses 2016: ICRS-10 Materials Research Forum LLC Materials Research Proceedings 2 (2016) 25-30 doi: http://dx.doi.org/10.21741/9781945291173-5 26 90 o Dector Bank Radial Collimator (5mm width) Radial Collimator (5mm width) -9 0 o De te ct or B an k Gauge volume (5 x 5 x 10 mm3) Gauge definition slit (5 mm width x 10 mm height) Reinforced concrete specimen 45o 10 5 5 (c) 110mm (un-bonded region) 320mm (Bonded region)

Development of Building Monitoring System to Verify the Capacity Spectrum Method

Due to Kobe Earthquake (1995, M7.3), 6,434 people were killed, and 104,906 buildings were totally collapsed. After Kobe Earthquake , 17 large earthquakes occurred in Japan, which include Niigata Cyuetsu Earthquake (M7.2) in 2005 and the 2011 Off the Pacific Coast of Tohoku Earthquake (M9.0) in 2011. At the same time, a lot of earthquake ground motion data were measured by sensors. Some earthquakes, however, caused only slight damage to reinforced concrete structures although many earthquake records with large PGAs were measured. A monitoring building response is required to find out the reason of disagreement between analysis result and observation. In this paper, a building monitoring system with inexpensive sensors is proposed and the validity of the system is confirmed with an actual response of an instrumented building during the 2011 Off the pacific Coast of Tohoku Earthquake .