We conducted questionnaire surveys on evaluation of surface defects in concrete specimens and reinforced concrete buildings. The questionnaire responses were statistically analyzed to identify and calculate the odds ratios of factors influencing defect evaluations. Based on these results, we investigated (1) the acceptable limits of bug-hole area ratio, crack width, and standard deviation of lightness—defined as the level at which half of evaluators are expected to accept—and (2) the psychological acceptability of the appearance of cracks with different widths and, particularly, a crack width of 3 mm.
The generation process and propagation of the basin edge induced wave were observed from the continuous ground motion record by MeSO-net. The basin edge induced wave was generated at the western edge of the Kanto basin when S-wave, generated near Choshi City, arrived there. Particle motion revealed that Love wave dominates in the transverse components, while the higher mode of Rayleigh wave dominates in vertical motion. Snapshot enables to visualize the marriage of the basin edge induced wave and direct surface wave. Numerical simulation reproduced the observed basin edge induced wave. That wave significantly amplifies the displacement response.
We estimated rupture directions and directivity effects of moderate-sized intraslab and interplate earthquakes off coast of Fukushima prefecture using S-net, K-NET and KiK-net records. Source spectral ratio of each earthquake to a reference earthquake observed at the same station is modeled by using the dependency of amplitude in the frequency higher than corner frequencies on azimuths assuming unilateral rupture. All four intraslab earthquakes are estimated to rupture to updip which is the direction to west toward land. Therefore, their short-period spectral level estimated using only KiK-net records are much larger than those estimated using records at all stations.
The authors proposed the quantitative criterion for the safety of ceiling boards in the preceding paper. In the ceiling drop tests, the impact load was measured by the load cell under the dummy head due to the measurement difficulty at the contact surface. Therefore, in this paper, the authors identified impact load on the contact surface, by inverse analysis, from the load cell record and validated it. As a result, it showed the impact load amplifies as the force transmits from the contact surface and the evaluation by the proposed criterion is on the safe side.
This paper presents an optimization method of the joint arrangement for shell structures composed of CLT panels. The joining system is modeled as link elements with multidirectional stiffness. Their stiffnesses are calculated by multiplying the weight parameters defined as the design variables to the original stiffnesses. Furthermore, the joint arrangement is controlled by multiplying a power-law function to design variables. An optimization problem is formulated to minimize the strain energy. The effectiveness of the proposed method is shown through numerical examples. It is confirmed that the joint arrangement in each direction is optimized corresponding to the stress state.
The aim of this research is to establish a design method for the glulam frame structure with tensile-bolted moment resisting joints. In this paper, we proposed a calculation method of the stiffness and strength of column - base joints subject to axial force and conducted the bending test for the column-base joint subject to compressive axial load to grasp the failure modes and the characteristic values. From the comparison of the test values and the calculated values, we confirmed the validity of the proposed method.
The maximum crack width is frequently used as a damage indicator for reinforced concrete (RC) structures. However, predicting crack width and crack spacing through conventional nonlinear finite element (FE) analysis with the smeared crack concept is difficult. Accordingly, a crack propagation index based on FE analysis is proposed. The maximum crack width observed from past experiments on RC shear walls and the increment of element volume in the FE analysis were associated to derive the method for calculating the index. The index simulated the increasing trend of maximum crack width observed in the past experiments.
When a steel moment-resisting frame deforms horizontally, H-shaped beams are subjected to the flexural moment gradient. Generally, H-shaped beams are rigidly connected to the box section columns possessing the large fork restraint. Further, continuous braces on the top flange effectively prevent lateral buckling. In this paper, the lateral buckling behavior of continuously braced H-shaped beams with the fork restraint under the flexural moment gradient is clarified theoretically and analytically. Additionally, the elastoplastic buckling stresses of beams and lateral restraint force and rotational restraint moment of continuous braces are evaluated, reflecting the flexural moment gradient and constraint at the beam end.
The fracture factor that determines the ultimate flexural strength and limit displacement of concrete-filled steel tubular (CFT) columns subjected to high axial compression is the local buckling of the flange/web of the steel tube at the hinge region and crushing of concrete. Therefore, the structural performance of CFT columns can be improved if the steel tube and concrete are specially reinforced to prevent local buckling of the steel tube and flexural crushing of concrete. In this paper, a reinforcement method using PBL (Perfobond-Leisten) was proposed, and its reinforcement effect was confirmed by experiments.
The main purpose of this study is to evaluate tensile strength at elevated temperatures and after heating and cooling processes, for JIS G3549 strand steel wire ropes (the nominal diameter: 9mm) with the tensile strength 1570 MPa at ambient temperature. The steady-state, transient-state, creep, and the tensile tests after the heating and cooling processes were conducted, respectively. The test results to evaluate the tensile strength and collapse temperatures at fire and post-fire from the ambient temperature to 800 ℃ were accumulated.