In this study, we aimed to clarify that modification condition when unburned carbon of Fly Ash which quality differ is removed by flotation method, physical properties of Fly Ash which was modified by that condition and properties of mortar and concrete with it. As a result, properties of modified Fly Ash by flotation method are superior to original ash, and unburned carbon of Fly Ash was removed, particle size of it had become fine down. Therefore, fluidity of mortar and concrete with it improved. In addition, durability of concrete with it was superior to normal concrete.
We conducted a study to estimate damage to buildings considering the directional property of seismic ground motions and buildings. We created the fragility curve based on the ‘average direction’, which response is the average value in various directions. We found responses in the average direction and responses in the ‘maximum direction’, which response is the maximum in various directions have a strong linear relationship. We can estimate damage to buildings by the fragility curve based on the ‘average direction’ by using the response estimated from the response in the ‘maximum direction’, that can be calculated faster than the ‘average direction’.
The applicability of the seismic interferometry was examined for the purpose of establishing a method for investigating the two-dimensional S wave velocity structure. Microtremor records were obtained for 14 hours and 22 hours at two sites with different vibration levels, respectively. The main findings obtained are as follows.
1. S-wave velocity structures at depths of 20 m or more can be explored, which is difficult to do with existing surface wave surveys.
2. Phase velocity can be detected in about one hour of measurement by arranging a large number of receiving points in a straight line.
This paper proposes a control method of Active Mass Damper (AMD) for Building Mass Damper (BMD). The parameters of the soft story of BMD must be higher than the optimal values to prevent excessive displacement of the soft story. The AMD makes the behavior of the non-optimal BMD close to that of the optimal BMD and improves damping performance by the proposed control method, which is based on Model Predictive Control (MPC). Through the results of numerical analysis and shaking table test, it is demonstrated that the proposed method can mitigate the responses of the non-optimal BMD.
This paper presents a response evaluation method for a seismic control structure includes a large weight sub-system as dynamic mass damper. Not only a conventional 2-element sub-system but also a 3-element sub-system with an inertial mass are taken into consideration. The fundamental idea is to consider the main-system’s displacement as that of equivalent SDOF system, and the sub-system’s stroke as a modified independent sub-system’s displacement amplified by the interaction with the main-system. First, optimum absorber parameters of variable conditions are derived. After formulating the needed equations for evaluation, the accuracy of the method are discussed by numerical analyses.
An image data acquisition monitoring system for the suspended piping that is difficult to inspect visually above the ceiling, is developed to evaluate the building functionality immediately after an earthquake disaster. The proposed sensor unit consists of an infrared camera for collecting image data and an accelerometer for triggering image data acquisition. The image analysis method based on a single image is presented to estimate the seismic residual deformation in the suspended piping. The proposed image monitoring system is applied to the shaking table test of a full-scale steel frame structure with building equipment at the E-Defense facility.
At the pile head part of a steel pipe pile, commonly a structure called slip prevention stoppers are attached to the inner surface of steel pipe pile in multiple steps, and filled with concrete in the pile body. However, there are no reports on experimentally verifying the structural performance of this structure. In this paper, we have confirmed the integration of steel pipe pile and filled concrete, ultimate bending strength and deformation capacity. We propose a method to calculate the ultimate bending strength and deformation capacity at the pile head part of steel pipe pile and show its validity.
This durability survey investigates age-related changes in the properties of pile materials such as concrete and reinforcing steel when reusing existing piles, but this is limited to confirming that the results satisfy the regulations and specifications in the design documents. In this paper, the survey results of existing cast-in-place piles are analyzed for the purpose of utilizing the survey results to rationalize pile reuse design. As a result, we gain an understanding of the trends in compressive strength, density, elastic modulus and neutralization depth, and present the results of the study on evaluation of pile properties for use in design.
The objective of this study is to grasp the required tensile performance at column-to-lintel connections of the wooden frame with a hanging mud wall in case of a hanging wall with initial failure in shear. In the full-scale tests, hanging mud wall specimens were collapsed with initial failure in pull-out of a lintel. A static pushover analysis was conducted to simulate the relationship between lateral load and deformation angle and the tensile displacement at column-to-lintel connections. In addition, the mechanical model to estimate the initial failure of wooden frame with a hanging mud wall is constructed.
In this paper, assuming that the embedding deformations under steel plates and dowels were almost equal to the deformations of damage zone in these joints, the evaluation methods of stiffness of tensile-bolted joints and dowel-types joints based on Strongest link model were proposed. To inspect the proposed methods, we compared and verified experimental and calculated results. The experimental and calculated values by the proposed methods were in good agreement and the effectiveness of the proposed methods was shown.
Currently there is no examination formula of shear force acting on the connections between joint members of sheets and columns used in the structural design of sheathed shear walls with multiple sheets. A formula is derived by applying the mechanical model of sheathed shear walls with various nailing arrangement patterns developed by the first author.
This formula is verified with experiments and numerical analyses.
The criteria necessary to examine the shear force acting on the connections depending on the nailing arrangement patterns is presented in this paper.
Vibration characteristics of high-damping timber structure are discussed based on resonance curve and time-history response analysis. The steady-state response of the timber structure that has viscous damping and friction damping is derived by Caughey’s equivalent linearization technique. The resonance curve shows that adding viscous damping and friction damping works to mitigate jump phenomenon. Time-history seismic response analysis is carried out to confirm the validity of the results obtained by the resonance curve and to propose the method for estimation of damping performance to obtain desired response reduction.
Four-point bending tests were conducted to investigate the flexural properties of fly-ash-based geopolymer concrete beams. Although the geopolymer concrete has a stress-strain relationship with brittle compressive softening behavior, it can be used as a flexural member because it showed ductile bending moment-deflection relationships by installing compression reinforcing bars and transverse reinforcement. The test results revealed that the conventional design method could be used to estimate the bending moment-deflection relationship of geopolymer concrete beams. However, the stiffness reduction ratio for yielding needs to be modified to consider the difference in modulus of elasticity between geopolymer concrete and ordinary portland cement concrete.
Experiments and finite element analysis were performed using members taken from an existing RC building. The average concrete strength from the material tests was less than 10N/mm2, the RC building was of extremely low strength concrete. The obtained members were subjected to reversal loadings to evaluate the validity of the equations of ultimate strength used in the seismic evaluation. Further, the damaged members were repaired with epoxy resin injection to investigate the effect of repairs after earthquake events. The behavior of actual members and the repair effect of epoxy resin injection for low strength concrete were discussed in the paper.
The evaluation method of the joint strength in a non-diaphragm connection of a circular hollow section column to H-shaped beams subjected to 45°-oblique horizontal loading is discussed in this paper. The ultimate state of the joint under 45°-oblique loading can be considered as a combination of those of under two biaxial-symmetrical bending moments. Therefore, the prediction method of the joint strength under oblique loading using the proposed formulae for the joint strength under biaxial-symmetrical bending moment was proposed, and this evaluation method demonstrated good accuracy in predicting the joint strength under oblique loading.
The purposes of this study are to present the formula for calculating the ultimate flexural strength of a circular CFT section, to clarify the relationship between the generalized superposed strength and ultimate flexural strength, in addition, the relationship between the generalized superposed strength and simple superposed strength. Numerical calculation based on the theoretical analysis is performed and moment -axial load interaction relations are shown. Comparing the ultimate strength with superposed strength, the effects of analytical parameters on the strengths are discussed.