Damage of PC tendons in a prestressed concrete structure need to be detected before such damage accumulates to cause a serious failure. That, however, is quite a difficult task because the PC tendons are invisible from outside and the damage location cannot be known beforehand. Phase space analysis based on vibration data is a novel method for damage detection. An earlier study by the authors demonstrated that Change of Phase Space Topology (CPST) was effective in identifying the existence of PC tendon damage. However, CPST from impact hammer test, which is a more practical method, did not show a trend as obvious as that of the free vibration test. As it is known that PC tendon damage affects several modes of vibrations and that the hammer can be used for excitation to the higher modes, it may be possible to improve the capability of impact hammer test by considering CPST separately in different frequency ranges. As in the previous study, the current study conducted experiments on PC tendon damage, but with an increased number of accelerometers for constructing mode shapes and investigated CPST further in different frequency ranges. The results still revealed that CPST was more sensitive to damage than the parameters from modal-based analysis. CPST in different frequency ranges can improve results from impact hammer test and has the capability to identify roughly the damage locations.

Hardened cement pastes (HCP) with different water contents were irradiated with gamma rays under different temperatures and irradiation dose rates. The relationship between the quantity of hydrogen gas produced and the water content as well as the stability of HCP under gamma irradiation was evaluated. It is experimentally confirmed that hydrogen gas was mainly produced from the evaporable water. The G value of the hydrogen production assuming the radiation energy absorbed by the total water composed of chemically bound water (CBW) and evaporable water was ranging from 0.03 to 0.42. The G value of the hydrogen production for CBW was ranging from 0.03 to 0.07, which were an order of magnitude smaller than that of the bulk water (0.45).

Assuming that the radiation energy on evaporable water is used for the formation of hydrogen, it is experimentally confirmed that, in case of low dose rate, the G value tended to converge to a constant value when the evaporable water exceeded a certain value, while, in case of high dose rate, the G value increased as evaporable water increased. However, the G values of all cases grew with increasing evaporable water content and exceeded the G value of the bulk water (0.45). The CBW was not susceptible to gamma irradiation. Only 2 to 3% of the CBW was estimated to be decomposed by 200 MGy of gamma irradiation.

A multi-scale model for significant characteristics of cementitious composite and structural concrete at high temperatures is presented and the experimental verification at micro, meso and macro-scales is conducted. Deterioration of cement hydrates, reduced stiffness of concrete composite and their rehydration are modeled at high temperature of 100 – 1000°C and integrated up to the multi-scale simulation platform. This framework enables us to reproduce some meso-scale chemo-physics such as progressive spalling of concrete cover and exposure of reinforcing bars. The temperature-dependent thermal characteristics of both aggregates and cement matrix are also considered to truck the rising temperature inside RC members. The behavioral simulation of columns, slabs and beams, which are subjected to axial compression and out-of-plane flexural shear, is conducted to be ready for fire.

In order to enhancement accuracy of shear design of reinforced concrete (RC) beams, detail understanding of the shear resistance mechanism is required. This study evaluated the shear resistance mechanism of RC beams based on arch and beam actions by using three dimensional Rigid-Body-Spring-Method (3-D RBSM). Firstly, RC deep and slender beams with and without shear reinforcement failed in shear were tested to measure local behavior. Then, the validity of local behaviors obtained from 3-D RBSM was confirmed by comparing with the test results and the applicability of decoupling of shear resistance mechanism using simulated stress distribution was presented. Moreover, the contributions of arch and beam actions in RC beams until failure stage were investigated numerically by changing the shear reinforcement ratio and shear span to depth ratio and was compared with the current shear design recommendations in JSCE Standard Specification. As a significant finding, the numerical results upon the quantitatively evaluation of shear resistance mechanisms that the shear strength of RC beam could be evaluated without classification of deep beams and slender beams was presented.

The distribution of restraint stresses in bottom-restrained walls is an important information for the efficient crack control of wall-like concrete members. Practical examples are retaining walls, bridge abutment walls or tank walls, for which the results can be used in order to assess the risk and intensity of harmful separating cracks over the wall height.

Different solutions exist for the determination of these stress distributions, ranging from advanced computational methods over analytical and semi-analytical solutions up to empirical approaches. The aim of the present contribution is twofold. On the one hand, the general applicability as well as commonalities and differences of the investigated solutions were demonstrated by using them for the analysis of a given demonstration example. On the other hand, a para-metric study was carried out in order to assess the dependence of the prediction quality of the applied solutions on changing conditions. Altogether it was found that advanced computational methods and analytical or semi-analytical solutions showed a good agreement for common design tasks. Solutions with empirical modifications, however, were proved to be less satisfying from engineering perspective due to predefined parameters or mechanically inconsistent modifications.