The study proposes a simple index for evaluating the deterioration of reinforced concrete columns by statistically examining three impact acoustic properties; sound pressure level of the maximum amplitude, the cluster analysis for the normalized 1/3 octave band levels, and the energy decay time of 2.5 dB. The proposed index is developed based on the field measurement survey at Nikkyu jutaku and validated using the results of another building (Building 39) on Hashima Island. The results show that the proposed index generally provides a reasonable evaluation.

The effect of Superabsorbent polymer (SAP) admixture in patch repair materials on the adhesion to the base concrete and the protection performance of reinforcing bars was investigated. In the experiment, one side of RC joint specimens were exposed to water. Water leakage from the interface between the base concrete and the repair material was reduced in the SAP specimen compared to the conventional Polymer modified mortar specimen. In addition, the half-cell potential and polarization resistance of the SAP specimens showed noble and high values, respectively, indicating the inhibition of corrosion of reinforcing bars.

Viscoelastic (VE) damper generates heat as it dissipates seismic and wind-induced structural vibration. Thereby, when under long-duration loading, its temperature can significantly increase. Since it is highly sensitive to frequency and temperature, effect of heat generation and heat transfer must be considered when predicting its dynamic mechanical properties. Previous studies on two-layered VE dampers had proposed analysis and prediction methods based on one-dimensional heat transfer. Such methods, however, were never employed to multi-layered VE dampers. Therefore, this paper extends such one-dimensional modeling approach to analysis and prediction of multi-layered VE damper properties considering effects of heat conduction and convection.

In 2016, a countermeasure against the Nankai trough long-period and long-duration ground motions (LPGMs) was announced. However, the response spectrum method (RSM), indicated by the Ministry of Construction notification Vol. 2009 (MCN), is out of the countermeasure. An RSM that considers characteristic changes due to repeated deformation has also been proposed, but since the damping correction formula of MCN is used, its applicability to LPMGs has not been sufficiently investigated. In this paper, we proposed a method for evaluating the influence of characteristic changes due to repeated deformation using RSM for LPGMs and seismically isolated buildings using LRB.

The buckling restraint brace (BRB) has a function of giving damping to a building, but at the same time, BRB is prone to shorten the resonant-vibration period of the building and to increase the displacement response. Therefore, the inertial mass damper (IMD) is applied to suppress the resonant vibrations of the building. By this method, the original damping energy of BRB can be efficiently extracted. Consequently, an optimal layout for a hybrid damping system of BRB and IMD in the high-rise building is proposed. The effectiveness of the proposed method is confirmed by comparing with the optimal arrangement of BRB.

The authors focus on the thermal-mechanical coupled behavior of tin rubber bearings (SnRBs) under cyclic loading. The research consists of three phases. First, the tests providing a large number of cyclic deformations to the SnRBs were performed. Second, an analysis model considering the thermal-mechanical coupled behavior was constructed by combining a seismic response analysis and thermal conductivity analysis. Finally, seismic response analyses using the model were conducted to evaluate the dynamic behavior of seismically isolated buildings with SnRBs. The authors conclude that characteristic change due to cyclic deformations of the SnRBs should be considered for long-duration earthquake ground motions.

The author has estimated broadband source models of the off Miyagi earthquakes in March (M_J 6.9) and May (M_J 6.8), 2021 using S-net and KiK-net strong motion records by the empirical Green’s function method. Strong motion generation areas are located at different regions of the 1978 and 2005 off Miyagi earthquakes. The short period spectral level of the two earthquakes are larger than the average of the interplate earthquakes on the Pacific plate. Rupture directions of moderate-sized interplate earthquakes in the source region estimated in this study are up dip directions which are consistent to the two earthquakes in 2021.

This paper discusses the basic mechanical properties of a newly proposed parallel link mechanism as a three-dimensional seismic isolation system capable of supporting large loads. Specifically, the static restoring force characteristics of the entire mechanism, the moment caused by the spring force, and the inclination of the top surface due to 3-dimensional displacement were analyzed. The results show that stable static restoring force can be obtained by setting the initial angle within a certain range and using multiple units with a separation distance of 4 m or more between mechanisms.

To clarify behavior and sliding resistance of a spread foundation under combined load, static vertical loading test, and static vertical and lateral combined loading tests were conducted on a spread foundation on sand. The sliding resistance under the combined load was caused by the soil failure beneath the foundation. After the peak of the lateral resistance, settlement and horizontal displacement increased although vertical and lateral load did not increase. When the vertical load is less than about 1/2 of the ultimate bearing capacity, the vertical load could be retained and the horizontal displacement was greater than the settlement.

A post-installed shear reinforcement (PSR) method that is applied to flat plates such as foundation slabs and underground outer walls from inside the building was developed. In this study, the out-of-plane shear strength evaluation formula was proposed using the past test results. In addition, since these flat plates are subjected to seismic force while receiving earth pressure, it is expected that they will be in a complicated stress state during an earthquake. In such a case, finite element analysis is useful, so the experimental results were simulated to verify the finite element analysis method for the flat plate with PSR.

This paper proposes a simple method to obtain equilibrium membrane forms under the self-weight. The horizontal component of the membrane forces determined by the finite element analysis of an initial shell form is given as the known membrane stress distribution in the form-finding analysis. The form of the hanging membrane can be obtained by modifying the nodal z coordinates to be in equilibrium for the self-weight while maintaining the horizontal membrane stress distribution. Several numerical examples are presented to demonstrate the effectiveness of the proposed method.

In this paper, a numerical model considering the embedment reaction of column foot by the beam-column finite element method was proposed for evaluating the restoring force characteristics of the rocking column in traditional timber structures. Wood compression tests in contact with stones were conducted to investigate the characteristics of the embedment reaction and initial deformation generated at the end of the wood, and these characteristics were considered in the column foot numerical model. The validity and applicability of the numerical model were verified by analyzing several static loading tests of the rocking column.

An evaluation procedure of the seismic performance of overseas RC buildings with unreinforced masonry walls is proposed and applied to an urban residential building in Nepal. The structural performance of unreinforced masonry walls in the out-of-plane as well as in-plane directions is considered in the proposal. Consequently, the seismic performance of the building of interest was reliably evaluated considering the in-plane effects of brick walls; namely, it was confirmed that the brick walls did not collapse in the out-of-plane direction under the analytical conditions adopted in the present study.

Tri-directional loading tests were conducted with out-of-plane deformation and axial force conditions as parameters. The in-plane maximum load capacity was reduced by 8.8% due to out-of-plane deformation and varying axial load. The results were discussed along with previous experiments by the authors. As a result, it was found that the out-of-plane deformation reduced the maximum load capacity by 19% compared to that under uni-directional loading, while the axial force variation reduced that by 2% compared to that under constant axial load. An evaluation method considering tri-directional loading proposed by the authors could accurately evaluate the in-plane shear capacity.

In this paper, we proposed new "Energy balance method" characterized by the following two points.

1) Calculate plastic deformation capacity of story using the fatigue curve of beam-end connections

2) Consider ground motion characteristics, for instance, long-duration ground motion with large energy spectrum

We compared this method with time history response analysis result in terms of damage degree of beam-end connections. Furthermore, we verified seismic safety for medium and high-rise steel buildings and confirmed effects of specification of beam-end connections, installation of damping device and characteristics of ground motion by method.

This paper investigated the dynamic response characteristic with focus on damped slit configuration of damped braced tube systems with oil dampers. According to the results, 1) damped braced tube system has over 10% 1st to 3rd damping ratio, 2) while the displacement and acceleration responses are simultaneously reduced up to maximized 1st mode damping ratio, the acceleration reduction effect may be getting worse after the peak, 3) while uniform damper distribution contributes to better damping performance, centralized damper distribution contributes to better period reduction.

Superior design solutions (SDSs) of seven-story steel buildings are obtained for a space frame system (SFS) and perimeter frame systems (PFS) in various structural systems such as moment frame (MF) and those with buckling restrained braces (BRBF). The SDSs satisfy the design constraints of allowable stress design (ASD) and calculations of resistance and limit state (CRLS) with the minimized steel volume. The influences of design conditions are comparatively evaluated. It is found that the maximum inter-story drift ratio for safety limit in CRLS for MF can be rationally defined as 2% and ASD can be more dominant for BRBF.

From the results of recent research on long-period ground motions, it is feared that a high-rise building with a long natural period will be seriously damaged by long-period ground motions caused by a huge earthquake along the Nankai Trough, which is expected to occur in the near future. Therefore, it is an urgent task to grasp of the structural performance of concrete-filled steel tubular (CFT) columns used in high-rise buildings against multiple cyclic loadings. To grasp structural performance of square CFT columns subjected to multiple cyclic loading, ten specimens were tested.

Experimental and FEM-based analytical study revealed following aspects regarding post-installed adhesive anchors set with Epoxy or UHPFRC adhesive.

1.The experimental and FEM results agreed in regard to maximum loads, load-displacement curves, crack patterns, failure modes and the location.

2.The load-bearing mechanisms was discussed employing a model with a conic surface and an interface layer below it, which revealed the contribution of a conic surface to the maximum load was low and that of an interface layer was very high.

3.The mechanisms of combined failure with cone-shaped fracture of concrete and interface slipping were also reported.

In the evaluation of losses due to building damage during earthquakes, it is necessary to comprehensively consider the variability of response, damage, and loss, even when the earthquake motion intensity is fixed, and Monte Carlo simulations are required to account for these variabilities. Among the economic losses, the repair time requires consideration of the repair schedule corresponding to the damage distribution, and therefore a rational and automated evaluation method has not been established. This paper proposes a method to evaluate the repair time integrated in the MCS by utilizing a method to automatically generate a logical network of repair schedules.

In this study, load-heating tests were conducted on glued laminated timber frames to investigate the temperature and charring behavior of column-beam connections of dowels under standard fire heating for more than 1 hour. This paper reported on these results and discussed on the required covering thickness to control the temperature and charring. Wood plugs with 40 mm thickness at the dowel connections prevented that the charring reaches to head of the dowels during 4 hours (heating for 1 hour and decay for 3 hours) for Japanese larch. Partial wood-covering at the beam ends decreased temperatures of the steel connectors.