In order to apply the electro-magnetic radar method as an inspection method for cover depth, this study proposed a method to set relative permittivity.
One is to correct the permittivity based on the relationship between the water content on the concrete surface and the relative permittivity, and the other is to measure the cover depth by correcting the permittivity based on the relationship between the water content on the concrete surface and the electromagnetic wave speed. As a result, it was confirmed that the accuracy was equal to or better than that of the electromagnetic induction method.
We propose and validate an evaluation method for fundamental vibration characteristics of high-rise buildings considering the dynamic characteristics of oil dampers with relief load based on the theoretical background. In the evaluation method, we analyze the characteristics in the steady-state response of the system through the equivalent linearization method taking the effect of relief load into account. We validate the applicability of the proposed evaluation method by analyzing the fundamental vibration characteristics of a single-degree-of-freedom model, and investigate the applicability of to the seismic response evaluation of multi-degree-of-freedom model.
In this paper, the influence of dampers on perception time is analyzed from the results of time history response analysis of steel high-rise buildings with dampers. In addition, based on the analysis results, this paper proposes a method of predicting perception time using SDOF elastic system. The period fluctuation is evaluated by the perception time spectrum, which expresses the relationship between the perceptual time and the natural period and is calculated using SDOF elastic system. The damping ratio fluctuation is evaluated by the perception time correction factor adapted to the results of time-history analysis.
Seismically isolated layer may pound against moat walls when a large earthquake occurs. To address the above problem, we developed the displacement control system (DCS). DCS is a seismically isolation system with quasi-zero stiffness (QZS) and inerter. This study evaluated the steady-state response of our DCS through analysis. The response of DCS to seismic excitation was also investigated through shaking table tests. Comparing the analytical solutions and the test results showed that the analytical solutions agree well with the test results. The test results of seismic wave excitations indicate that our DCS suppresses the maximum response displacement and acceleration.
The friction coefficient of elastic sliding bearings is velocity-dependence. Since this dependence is particularly strong in the low velocity range, it is important to consider this dependence when designing structures for forces that result in low-response speeds, such as wind forces. However, conventional design methods do not consider the effect of velocity dependence. In this paper, an equation for the velocity dependence of the sliding friction coefficient at low velocities is derived from experiments. An analytical model to simulate this dependence is proposed to enable more accurate calculation of the restoring force characteristics of the elastic sliding bearings.
A new full-scale seismic isolation test facility named “E-Isolation” has been developed and adopted as a new system that can directly measure the reaction force of the device, excluding the friction force generated in the bearing under the moving platen and the inertial force due to the weight of the platen. In this paper, several experiments were conducted to verify the accuracy of the measurement system in “E-Isolation” under construction. The results of various experiments showed that each component of “E-Isolation” performed as expected in the design, and the measurement system was able to measure data accurately.
This study is an experimental study using Dou-gong extracted from the demolition site of a traditional timber architecture constructed in 1856. In order to clarify the hysteresis curve and deformation behavior of Dou-gong, two-dimensional and one-dimensional horizontal loading experiments were carried out under a vertical load of 20 kN. At the same time, the effects of aging were verified by comparing the results of a dynamic loading test8) on new materials. As a result of the experiment, it was clarified that the hysteresis curves of both are similar although there is a difference in deformation behavior.
Loading tests were conducted on three steel-tubed reinforced ultra-high-strength concrete columns to study the effect of the amount and strength of transverse reinforcement on their flexural behavior using these three specimens and four previously tested specimens by authors. Test results showed that the shear reinforcement had a significant influence on the ultimate deformation. A motion capture system was used to investigate the stress condition of the concrete. A fiber-based analysis was also carried out to find the proper stress-strain relation for concrete to simulate the moment-curvature relations.
The stress transferring mechanism of single pile caps with horizontal two-way eccentricity was investigated using FEM analysis. Since the compressive stress of the pile cap is lower than that of the column except local points, the safety of the pile cap can be ensured by making the concrete strength of the cap and column the same. Moreover, high shear stress and strain were observed in the foundation beams toward the inside of the building. Therefore, the shear design of foundation beams connected to the caps requires a margin of concrete strength and stirrup.
High-strength steel with a tensile strength rating of 780 N/mm2 have been developed in Japan. However, in order to make the strength of the weld equal to that of the base material, much labor and cost are required. If the welds for the column splices in the site can be done by under-match welds, the problems in welding work can be greatly reduced. This paper proposes a design method for the column splices performed by under-matching welds. We carried out bending tests of box column members with the column splice and estimated the ultimate flexural strength of column splices.
This paper describes a methodology to evaluate the elastic shear buckling strength of H-shaped members under shear force. The methodology is based on energy method applying novel displacement functions which are able to capture shear buckling deflections for various cross-sectional profiles of H-shaped sections by using unique trigonometric series. With the proposed displacement functions, a high-precision equation, which can predict the shear buckling strength, can be obtained. To clarify the accuracy of the equation, a parametric eigenvalue analysis based on the finite element method is performed.
To investigate the cyclic hardening and softening behavior of SN490B steel, constant axial strain amplitude cyclic loading tests were conducted using round bar specimens with strain amplitudes ranging from 0.25% to 13.5% for fully reversed loading. The following results were obtained. When the strain amplitude is smaller than 0.50%, cyclic softening behavior is observed, and when the strain amplitude is larger than this, cyclic hardening behavior is observed. Cyclic hardening and softening behavior can be explained by the expansion and contraction of the elastic range. The expansion and contraction of the elastic range depends on the strain amplitude.
In recent years with the fabrication cost of steel soaring, there is a concerted effort to reduce the cost in order to construct large span buildings such as logistic terminals, shopping malls and medical facilities. Research investigations are being carried out and one of the methods is using a composite structure with reinforced concrete columns and hybrid beams. Since a greater shear force is transferred to the RC region, a precise method to estimate the shear capacity is necessary. Therefore, in this study hybrid beams under shear failure were examined and a method to the evaluate shear capacity is proposed.