In general, NiTi shape memory alloys are used for applications in civil structures. NiTi SMAs show good superelasticity and shape memory effect properties. However, for application of the shape memory effect, it is desirable for SMAs to show a wide temperature hysteresis, especially for civil structures which are exposed to severe environmental conditions. NiTiNb SMAs, in general, show a wider temperature hysteresis than NiTi SMAs and are more applicable for civil structures. This study examines the temperature hysteresis of NiTiNb and NiTi SMAs, and their recovery and residual stress are investigated. In addition, the tensile behaviors of SMA wires under residual stress are evaluated. This study explains the possible applications for concrete structures with the shape memory effect and illustrates two experimental results of concrete cylinders and reinforced concrete columns. For both tests, SMA wires of NiTiNb and NiTi are used to confine concrete using residual stress. The SMA wire jackets on the concrete cylinders increase the peak strength and the ductility compared to the plain concrete cylinders. In addition, the SMA wire jackets on reinforced concrete columns increase the ductility greatly without flexural strength degradation.

The purpose of this study was to propose a new method to confine concrete cylinders or reinforced concrete columns using martensitic or austenitic shape memory alloy (SMA) wires. The prestrained martensitic SMA wire was wrapped around a concrete cylinder then heated by a heating jacket. In the process, the confining stress around the cylinder was developed in the SMA wire due to the shape memory effect, which can increase the strength and ductility of the cylinder under axial compressive load. For austenitic shape memory wires, the wires were prestrained as they were wrapped around the concrete cylinders on which post-tensioning stress was generated. In this study, martensitic and austenitic SMA wires of 1.0 mm in diameter were used for the confinement. Recovery tests were conducted on the martensitic wire to assess the recovery stress. Also, a superelastic behavior test was performed for the austenitic wire. The confinement by martensitic SMA wires increased the strength slightly and greatly increased the ductility compared to the strength and ductility of plain concrete cylinders. The austenitic SMA wires showed a similar effect on concrete cylinders to that of the martensitic wires. This study showed the potential of the SMA wire jacketing method to retrofit reinforced concrete columns and protect them from seismic risks.

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-This paper presents the parameters optimization technology for generating the first short stroke lightning current waveform(10/350 μs) which is necessary for the performance tests of components of lightning protection systems, as required under IEC 62305 and the newly amended IEC 62561. The circuit using the crowbar device specified in IEC 62305 was applied to generate the lightning current waveform. To find the proper parameters of the circuit is not easy because the circuit consists of two parts; circuit I, which relates to the front of current waveform, and circuit II, which relates to the tail. A simulation in PSpise was carried out to find main factors related to the front and tail of 10/350 μs. The lightning current generator was developed by utilizing the circuit parameters found in the simulation. In the result of experiments, new parameters of the circuits need to be changed because of the difference between the simulation and the experiment results. Using the iterative method, the optimized parameters of the circuits was determined. Also a multistage-type external coil and a damping resistor were proposed to make the efficiency of generation to enhance. According to the result in this paper, an optimized first short stroke lightning current waveform was obtained.

This study conducts a bond test of reinforced concrete confined by a new steel jacketing method without grouting, which was suggested previously. The steel jacket does not show composite behaviour with concrete because it has no grouting. The aims of this study are to determine the performance of the steel jacketing method in improving bond behaviour and to assess splitting stress developed during bond tests. For the purpose, this study uses concrete cylinders with the dimension of 100 mm 3 200 mm and 150 mm 3 300 mm (D 3 L), and D22 reinforcing bars (nominal diameter of 22 . 2 mm) are embedded in concrete. The specimens of 100 mm 3 200 mm are designed to show splitting failure under unconfined conditions. On the contrary, the specimens of 150 mm 3 300 mm are expected to produce pull-out failure under unconfined conditions. This study analyses the relation of circumferential strain to bond stress and suggests a model of splitting stress-strain for the confined concrete. The new steel jacketing method transfers the bond failure from splitting to pull-out mode and increases bond strength and toughness satisfactorily. This study suggests the ratio of bond stress to splitting stress as a function of slip that can be used to develop an analytical model of bond behaviour. In general, the bond strength increases with the confinement of the steel jackets; however, too heavy a confinement is not effective in continuously increasing the bond strength. In contrast to the bond strength, more confinement effectively decreases circumferential strain. The bond stress-circumferential strain curves generally show hook-shaped behaviour for pull-out failure mode for unconfined or confined specimens.