In this study, the effects of high pressure pumping on the fluidity of concrete were investigated by full-scale pumping tests and laboratory tests. From the result, changes in concrete fluidity due to high pressure pumping were determined. Also, it was possible to evaluate the changes in concrete fluidity by laboratory tests using a compact pumping test equipment. It was found that changes such as an increase in the apparent surface area of the cement particles and a change in the adsorption amount of admixture occurred by applying pressure and shear force to concrete using a compact pumping test equipment.
Based on the compressive strength and static modulus of elasticity of mortar and concrete (water / binder 30, 20, 15%) using electric arc furnace oxidizing slag aggregate, the effect of aggregate type and amount of aggregate on each mechanical property was investigated. As a result, the compressive strength of mortar and concrete increased by 10-20% by using slow-cooled electric furnace oxidizing slag fine aggregate and coarse aggregate. In addition, it is found that the apparent static modulus of elasticity of electric furnace oxidizing slag aggregate is larger than that of natural coarse aggregate and fine aggregate.
This study aims to promote the use of recycled aggregate concrete that can be easily manufactured in Vietnam using low-quality recycled aggregate mixed with normal aggregate. This is achieved by examining performance evaluation of concrete through the relative quality index method and mix proportion design. If low-quality recycled aggregate and normal aggregate can be combined in concrete in a suitable replacement ratio, as has been done in Japan, the proposed method can be used for structural concrete applications in Vietnam.
Since, the fireproof coating work has lacked skilled workers, we have developed a fireproof coating spraying robot. In order to grasp the current situation and set the target value of the spraying thickness, the thickness of the fireproof coating sprayed by the skilled worker was measured using a laser scanner and analyzed. It was found that it is efficient to spray with a thickness obtained by adding twice the standard deviation to the specified thickness. Further, spraying the fireproof coating by the robot at the target value satisfied the quality.
In Japan, non-structural exterior walls consisted of metal panels are widely used for low- and medium-rise buildings. It is important to experimentally verify that the exterior walls can follow the story drift of the structural frame during a major earthquake without damage or falling off.
In this paper, in-plane loading tests were conducted on one unit of non-structural exterior walls using metal panels to confirm the deformation following capacity when subjected to large earthquakes. In addition, the ultimate state corresponding to the falling out of the metal panels was observed.
After a major earthquake, safety inspections of numerous buildings must be conducted. However, the number of available engineers is limited. We must improve efficiency of this inspections. One idea for improving efficiency is to accurately estimate the damage of buildings and inspect buildings with a high probability of damage first. In this paper, we propose a method to estimate the probability of building damage by Bayesian estimation using a small number of inspection results. We also show illustrative examples that the efficiency of building inspections can be improved by using the estimation results.
Vertical dynamic characteristics of the seismically isolated building constructed on the ground with inclined bedrock were investigated using ambient vibration measurement, strong motion observation, and seismic response analyses. Coupling effects of SH-, SV- and P-wave incidences were considered for seismic response calculation in the soil-pile-structure interaction analysis. Amplitude of the vertical input motion at foundation and the vertical response of the building was significantly reduced due to the constraining effect by pile foundations. This effect was especially obvious when the SV wave inputs to the inclined bedrock.
This study reports the relationship between the movement of medical equipment and near-fault and long-period-long-duration earthquake ground motions, aiming to provide practitioners and researchers with criteria for limiting disorder and functional deterioration during earthquakes. The influence of floor sheeting materials on the rolling friction coefficients of the equipment’s casters and their resistance to move out of floor dents was evaluated at a pulling test. Then, the seismic behavior of medical equipment was evaluated at E-Defense shaking table tests where a group of critical equipment was arranged for department rooms in the full-scale earthquake-resistant and seismically-isolated steel frames.
This paper describes study on accuracy verification of various restoring force models applied to high-damping rubber bearing by substructure real-time online testing (SROLT). We will compare the seismic response simulation of mid-rise and high-rise base-isolated buildings by SROLT and the numerical simulation applying three restoring force models to high-damping rubber bearings. As a result of comparing the accuracy of the three restoring force models, it was found that the numerical simulation using these restoring force models has the accuracy to confirm the response of the seismic isolation structure.
This paper presents a method for calculating the appropriate seismic loads for a single-layer cylindrical reticulated shell using machine learning. The equivalent seismic loads are evaluated by combining the dominant two vibrational modes, and the proposed method predicts the dominant vibration mode. The proposed method consists of three stages: imaging of vibration modes, feature extraction of the image using Variational Autoencoder, and prediction of image features. Machine learning results indicate that the proposed method successfully predicts the first dominant vibration mode 97.3% of the time and the second dominant vibration mode 78.4% of the time in the test data.
In this paper, a simple and practical method is proposed which enables formfinding analysis of a timber three-way latticed kagome shells and following buckling analysis, using general-purpose FE software without using specialized software for formfinding. In addition, the elastic buckling properties of the kagome shells formed by formfinding are investigated. In-plane shear stiffness of three-way lattices is so high that fixing the intersections does not allow the lattice planes to deform into a shell geometry. Therefore, the formfinding is carried out with virtual slide mechanism at the intersections enables slide of the members along the shell-surface without additional axial stress.
In our study, we propose a simple novel method to obtain funicular shell forms. In this method, the eccentricity distance of each node is obtained by dividing the bending moment by the membrane force. Then, by moving the shell surface in the normal direction by the eccentric distance, the bending moment in the shell is reduced. By repeating this calculation, a funicular shell can be obtained. We call this method “the eccentricity reduction method.” In the numerical examples, the bending moment almost disappeared in both the arch and shell examples, and the validity of the proposed method is confirmed.
In 2011, many roof bearings in large span facilities were damaged severely by the Pacific coast of Tohoku earthquake. Some of them were designed as slide bearings to release the thrust caused by the weight of roof. In ball-jointed system truss roof, bearings are subjected to horizontal movement and rotation since the roof structure has insufficient bending stiffness. In this study, we conducted the cyclic loading tests on conventional roof bearings and analyzed the observed behavior. In addition, we derived functions which express horizontal force in relation to horizontal displacement and rotation and verified by comparing with the test results.
In this research, the structural performance of CLT panel structure was confirmed through full scaled experiments, in which steel beams and CLT were jointed together using steel dowels. The number of drift pins in the connections at the four corners of the CLT and the difference in the performance of assumed fire resistance were set as parameters for the specimens. Element tests were conducted to obtain necessary characteristic values to develop an analysis model. Finally, incremental analysis was performed using finite element models. The analysis results generally reproduced the experimental results in good agreement.
Seismic tests were conducted on RC beams with large web openings strengthened by diagonal reinforcing bars. Maximum strengths of shear failure and flexural yielding type specimens exceeded the calculated values, and the later type specimen showed an adequate ductility. Diagonal reinforcing bars were proved to be effective by yielding just before the specimens reached their maximum strength. Experimental results showed that the test to calculated strength ratio at cracking of web openings increased when the opening’s diameter became larger and an arch mechanism effectively developed, although it is commonly presumed not to develop when such beams exhibit their shear strength.
Lessons learned from earthquake damage in recent years revealed that damage to RC structural members was limited; however, non-structural members were significantly damaged making difficulties for continuous building occupancy. In this study, a laboratory test was conducted to clarify the effects of non-structural flat walls on the seismic behavior/performance of a model frame representing the lower 2.5 stories of high-rise RC buildings. As a result, it was found that the non-structural walls contributed to increase the shear strength of frame; however, the shear forces applied to the structural members of columns and beams were also increased.
Tsunami-driven ships can cause a critical damage to buildings when colliding with their columns. In this paper, the authors report a collision test using reinforced concrete frame specimens and steel bars as colliding ships, and propose quantitative evaluation procedures of the maximum response displacement of the columns. The maximum column displacement is estimated using balance of the energy dissipation capacity of column specimens (calculated using estimated backbone curve) and the energy transferred from the steel bars (calculated using kinetic energy and coefficient of restitution). The proposed procedures could accurately estimate the maximum response deformation of the columns.
This paper presented an analytical study on elasto-plastic seismic response of low and middle-rise steel moment frames composed of square steel tubular columns and H-shaped steel beams under horizontal bi-directional excitation. The analysis assumed three-dimensional frame considering realistic structural behavior such as deterioration after maximum strength. Based on the analysis results, how to address the issues in current seismic design in Japan, where plane frame under uni-directional load has been generally assumed, is proposed.