A new system identification method based on top translational and rotational acceleration response is proposed for a five-story building model with biaxial eccentricity. The proposed method provides a comparison between the multi-input, multi-output transfer functions derived from a subspace-based method and those derived from the equation of motion. In this method, the lateral stiffness of each story and the damping ratios of the first and second modes are identified. The numerical example illustrates the cases of a shear-building lumped-mass model calibrated to match the first mode of the three-dimensional flame and the three-dimensional frame.

A method of multi-step loading test was introduced to investigate the aging of 3D-printed polymer parts in terms of elasticity and viscosity under repeated service loads, where Nylon 12 by the process of powder bed fusion was employed in consideration of its excellent mechanical properties. Two-types of loading, i.e., axial tension on dumbbell-shaped plate coupons and 3-point bending on a cruciform-section beam, are examined on the condition that the generated strains remain in an ordinary service range. Major findings are as follows: alterations in viscoelasticity of the printed parts under repeated service loads are negligible when the loading rates remain the same, in other words, the mechanical properties are repeatable or free from aging, while the degree of loading rates is influential to Young’s modulus as well as viscosity but not to Poisson’s ratio. The repeatability was statistically tested by means of traditional Fisher-Neyman-Pearson’s statistics and also by Bayesian statistics.

Using spectral modal method and time history analysis, characteristics of wind-induced responses of high-rise apartment building were investigated. For the spectral modal method, the first linear-like mode shape was considered, and for the time history analysis, Newmark β method was implemented. Peak accelerations and maximum displacements at model height from both methods were reasonably coincide well, showing a little larger values from the time history analysis. The results from the spectral modal method were within the range of the results of each 10-minute sample in time history analysis, and it was found that forces applied on the shared space on the bottom of the building can be negligible in response analysis.

This study investigated tsunami loads on a building with openings based on hydraulic experiments and CFD. Three types of inflow conditions and four opening configurations were examined. The results indicated that, under normal flow conditions, the drag force decreased as the opening ratio increased. In contrast, for oblique flow conditions greater than 45°, drag force didn’t decrease. Furthermore, CFD investigated the pressures on external and internal surfaces. For inflow angles less than 22.5°, openings contributed to reducing the drag force, whereas for 45°, the drag force is nearly equal to that without opening because of the increase in internal pressure.

Improving the seismic safety of wooden houses is a critical issue. One method to prevent soft-story collapse is the installation of highly rigid through-pillars, known as "rocking pillars". By equalizing inter-story drift and redistributing the total shear force, these pillars suppress the building's seismic response and significantly reduce the probability of collapse. This study evaluates the response suppression and collapse prevention capabilities of rocking pillars by applying a performance-based safety assessment that combines fragility curves, derived from collapse analysis, with region-specific seismic hazard probabilities.

This paper proposes a simplified prediction of self-excited vibration in large-span cantilevered roofs, which can in turn be used to assess aerodynamic instability. The prediction is based on the rule that vibrations exist only if the wind-induced added stiffness is dynamically consistent with roof motion, and then the instability is determined based on the stiffness and damping of the wind-structure system. 2D rigid roof models with the first rotational mode were adopted. Firstly, the effectiveness of vibration prediction was excellently demonstrated using computational fluid dynamics (CFD). Secondly, the critical conditions were derived and aerodynamic properties measured in wind tunnel tests were applied to calculate the safe structural parameters.

A common failure mode for wooden houses in Japan during major earthquakes is a total structural collapse initiated by the failure of the first story. One method to improve seismic performance is the installation of rigid, continuous column-like members known as rocking pillars. These high-rigidity pillars help to homogenize the inter-story drift between floors, allowing surplus seismic capacity from the upper story to be redistributed throughout the entire structure. This study verifies the effectiveness of rocking pillars through shaking table experiments on a 1/4 scale, two-story wooden house model. The model was subjected to repeated seismic input until story collapse. The results demonstrated that the model without rocking pillars exhibited a progressively larger response in the first story, leading to its eventual collapse. In contrast, the model equipped with rocking pillars showed a significantly suppressed response and a markedly reduced risk of collapse, confirming their collapse-prevention capabilities.

This study investigates dynamic similitude for reduced-scale seismic experiments on seismically isolated buildings. By applying Buckingham’s π theorem, mass and stiffness were scaled with the cube of the geometric factor to relax strict similarity conditions. The isolation system was represented by a Kelvin–Voigt model, avoiding difficulties in nonlinear member selection. Validation through single- and multi-degree-of-freedom analyses, including a 15-story reinforced concrete building, confirmed close agreement with prototype responses. These findings demonstrate the applicability of the proposed framework, with future work addressing diverse ground motions and nonlinear behaviors.

To reduce indoor damage and improve of indoor resilience performance against major earthquakes, the behavior of cabinet installed within a reinforced concrete building during earthquakes was verified by shaking table tests on a five-story reinforced concrete building conducted at E-Defense in 2020, accumulating relevant data. Additionally, simulation analysis of the behavior of cabinet based on measurement records of the shaking table test was conducted to examine the reproducibility of the shaking table test results and the validity of the modeling. These results are considered to form foundational technology contributing to the improvement of indoor resilience performance.

The nonlinear energy sink (NES) is a vibration control device that utilizes the nonlinear resonance between an auxiliary mass and the primary structure. By exploiting nonlinear restoring forces, NES can maintain its vibration reduction performance even when the natural period of a building deviates from design value. Among various types of NES proposed, challenges remain in ensuring sufficient restoring force under small displacements and enabling control in two horizontal directions. We proposed a bidirectional NES with pretensioned springs (PB-NES) that addresses these challenges by employing pretensioned tensile springs to secure restoring force under small displacements, and by introducing a dual-carriage mechanism to achieve simultaneous bidirectional control. Numerical analyses and shaking table tests using scaled models confirm that the proposed PB-NES provides effective control in two horizontal directions and exhibits robustness against variations in the natural period of the structure.

In base-isolated structures, negative-stiffness control actively inputs energy into the system, providing a high level of vibration suppression, yet inherently posing a risk of system instability. By contrast, skyhook control dissipates energy through damping, thereby imparting a stabilizing effect on the system. Consequently, these two control strategies exhibit fundamentally opposing characteristics; however, this opposition also results in a notable complementarity between them. Leveraging this complementary interaction, the present study proposes an active base-isolation control method based on the principle of maintaining the superstructure in an approximately stationary state. In this approach, ground displacement is inversely estimated from measured acceleration records, and the resulting restoring force of the isolation layer is actively counteracted by actuators. The performance of the proposed control strategy is evaluated using a single-degree-of-freedom (SDOF) model. Compared with conventional viscous damping, the method achieves approximately a 50% reduction in peak structural acceleration and a reduction of RMS acceleration to about 60% of that obtained under viscous damping, demonstrating its effectiveness in mitigating seismic responses.

When subjected to excessive seismic motion, high-rise buildings are at a high risk of experiencing inter-story collapse. Incorporating steel plate shear walls into the building can mitigate this risk by preventing damage concentration. However, the influence of wall width and thickness on the effect of preventing damage concentration has been analyzed only qualitatively for each structural design of the building. This study investigates the influence of steel plate shear walls on the effect of preventing damage concentration through static and dynamic numerical simulations on a three-dimensional framework model.

The purpose of this paper is to present a physical consideration on the influence of the damping correction factor on the ripple shape of the velocity response spectrum. The results of the study showed that when the ripple shape is convex upwards, the damping correction factor tends to be smaller. This indicates that ripple shape of the velocity response spectrum is caused by the input energy of the earthquake motion at the resonance. It was also revealed that earthquake motion such as inland crustal types with a small number of repetitions results in a smaller ripple shape of the velocity response spectrum, resulting in a smaller damping effect.

Recent seismic events have revealed the vulnerability of pile head connections, emphasizing the need for rational and reliable design methodologies for these connections. This study examined the strength of pile caps with anchorage reinforcement and embedment by performing bending-shear tests. Even when cap dimensions were reduced or embedment lengths were shortened, the specimens exhibited stable load-deformation behavior and sufficient ductility. However, conventional evaluation approaches inadequately captured geometric influences. Then, a compressive strut mechanism-based model was formulated that incorporated effective shear reinforcement stress derived from the experimental results. Evaluation using the proposed formula showed close agreement with the experimental results.

The objective of this study is to calculate threshold values for each damage category within each evaluation item for mid-to-low-rise steel-framed buildings, based on prior research, to compare damage estimation results across evaluation items and examine their validity. After understanding the damage estimation results for each evaluation item, it was clarified that the story drift angle is the most conservative index. Furthermore, the validity of the indicator was demonstrated by comparing damage assessment results obtained through visual inspection of full-scale shaking table test results with those obtained using multiple evaluation items.

This paper compares the seismic design provisions for steel braced frames in Japan, the United States, and the European Union. Regulatory frameworks of the three regions are reviewed with emphasis on historical developments, seismic analysis procedures, and design criteria. Japanese regulations, governed by the Building Standard Law, have remained relatively unchanged since 1981, whereas U.S. and European provisions are subject to regular updates that incorporate the latest research findings and engineering practice, including revised hazard maps, capacity design principles, and improved connection detailing rules. The comparison shows that although substantial differences exist in structural design methods and requirements, similarities are found in the underlying structural philosophy and design procedures. It is hoped that this paper will help engineers from different regions learn from one another and contribute to more consistent international approaches to seismic design.

In this study, changes in wall mass sufficiency, eccentric factor, base shear and maximum displacement response are investigated by changing from brace bearing walls to plywood bearing walls of the same amount of bearing wall, using wall layout data for wooden houses. As a result, the following were found. The sufficiency ratios for the two types of the amount of bearing wall were calculated in accordance with the law in force in 2025, and it was confirmed that the sufficiency ratio using Method 2 was considerably safer than the sufficiency ratio using Method 1. The base shear at the ultimate horizontal resistant force with plywood bearing walls lies in the range 0.7 -1.2 times the base shear at the ultimate horizontal resistant force with brace bearing walls, which is 0.9 times if a linear approximation is taken.

In this study, I attempt to clarify the characteristics of torsional vibration due to eccentricity by simulating a model using random numbers. Several planar models are set up, and method of dividing into four parts and the modulus of eccentricity are calculated, and the correspondence between both calculation results is confirmed. The eccentric ratio, which is the ratio of eccentricity distance to plan width, is introduced as an alternative to the modulus of eccentricity. The concept of the eccentric ratio is similar to that of modulus of eccentricity, and the calculation is less complicated than that of the modulus of eccentricity, and it can be easily calculated using spreadsheet software. The eccentricity ratio, like the method of dividing into four parts, does not include information about the orthogonal walls, so it is safer than the modulus of eccentricity in that it does not overly expect the effect of the orthogonal walls.

The column-beam joint focused on this research is joined by fitting, screwing, and adhesive application. Full-scale rotating tests were conducted to reveal the moment resisting performance of the joints and to cosider the influence of each resisting element. Resistance element tests of each joining method were also conducted, and the results of these tests were used to predict the results of the full-scale rotational tests. These comparative study revealed the effects of construction conditions on structural performance.

This study aims to investigate the seismic performance evaluation method for wooden frame structures with a large-section brace, as used in western-style wooden buildings. The literature review on western-style wooden buildings with a brace is conducted. Based on the findings, test specimens are designed and subjected to static loading tests to determine the seismic performance of wooden frame structures with a large-section brace. Next, an analytical model replicating the test specimens used in the experiments is constructed and subjected to static incremental analysis. The validity of the analytical model is verified by comparing the experimental results with the analytical results.

Ensuring the structural safety of traditional architecture while preserving their cultural value is an important issue in many countries and regions. This study aims to clarify fluctuations of vibration characteristics of traditional timber structures by conducting continuous microtremor measurements, temperature, humidity, and moisture content measurements for 16 months. A specimen of one span by one span was installed in a laboratory and measured once a week from September 2022 to April 2024 to identify basic vibration characteristics and to understand their changes. Results revealed evident seasonal fluctuation in natural frequency and a high correlation with moisture content of wood was identified.

This study proposes a method to convert stress–strain relationships of wall clay specimens with different geometries using statistical analysis and deep learning. Compression tests on 371 cylindrical and prismatic specimens made from Kyoto Fukakusa clay revealed systematic differences in peak strength, strain at peak, and post-peak behavior. Regression analysis proved effective for converting density and peak strength, while deep neural networks made it possible to predict strain at peak and stress–strain curves. Combining regression and DNN models provided the best overall accuracy. The proposed approach integrates heterogeneous test data, offering a unified framework for structural performance evaluation of earthen wall materials.

We investigated the influence of varying connection specifications on the performance of shear walls with identical properties, focusing on the condition of preventing premature failure at column bases and heads. Our experiments revealed that connection performance affects the shear wall’s performance. This suggests that the ultimate state of timber wall structures is not adequately controlled in the allowable stress design method. We therefore proposed a formula to estimate the actual shear wall’s performance using the rigidity of the connections and the true shear performance, and its validity was confirmed by comparison with experimental results.

Funicular shells minimize bending moments under self-weight and are common in rational shell design. A previous study introduced the eccentricity reduction method, adjusting nodes based on membrane forces and bending moments. This study explores three ways to calculate eccentric distance on multiaxial stress fields: (A) along principal bending moment, (B) along maximum eccentricity, and (C) based on mean stress. Results show that method C is most effective for form-finding. Numerical examples confirm the validity of this approach.

In recent years, the use of cable-based systems such as string truss and beam string structures has been increasing. To achieve downsizing and simplification of intermediate joint metal fittings, it is essential to evaluate structural stability in the event of slippage. This study focuses on a string truss structure, aiming to clarify the structural behavior of fittings under slippage conditions. An experimental program is first conducted to determine the static and dynamic coefficients of friction. Subsequently, the influence of cable slippage at intermediate joint metal fittings on the overall structural response is investigated through contact-based numerical analysis. Finally, a simplified analytical method capable of accounting for cable slippage is proposed, and its applicability is discussed.

In truss tower structures, if the main members are not strong enough against compressive forces, the structure may collapse triggered by the buckling of that ones. With the increase in the assumed load following the revision of design standards, the simple and effective reinforcing methods for post and brace memberes are required. In this study, the reinforcing effect using Carbon-Fiber-Reinforced-Plastics (CFRP) attatched by VaRTM construction method was verified by member compression tests, and an designing formula was proposed to estimate the compression capacity of the CFRP reinforced members considering the effect of thickness reduction by attatching CFRP.

A reliable evaluation method has not yet been established for the ultimate strength of column-beam joints in mixed structures composed of RC columns and steel beams where the steel beam is connected eccentrically to the RC column core. This study investigated the effect of eccentricity in S-beams on the ultimate strength of eccentric joints.

Based on these results, we proposed a strength evaluation method for eccentric joints by applying the strength evaluation method for standard joints specified in the Architectural Institute of Japan guidelines. Calculations using this method can evaluate strength with accuracy equivalent to that of standard joints.

In this study, a new connection method for the use of laminated veneer lumber (LVL) in steel structures was proposed, and its bending capacity was investigated. The proposed composite beam incorporates an interlocking connection, which is expected to provide bearing resistance. To evaluate the bending capacity of the composite beam, bending tests were conducted. The results showed that a longer interlocking length enhanced the bending capacity of the connection, and that bearing resistance predominantly governed the improvement in connection bending capacity. Based on the experimental results, a formula for estimating the bending capacity of interlocking connections was developed. It was indicated that the bending capacity of the proposed connections was 1.64 to 2.05 times greater than the calculated value.

The authors developed a Light Gauge Steel (LGS) wall construction method that meets the required performance criteria based on the results of a uniformly distributed load test conducted on a test specimen composed of prefabricated components. In the development of this method, the authors focused on the lightweight steel components that constitute the LGS wall and devised a stud with a shape that possesses high cross-sectional performance. This stud is designed to have a thickness that allows for the installation of screws and a weight that enables manual transportation.

This report details the uniformly distributed load tests conducted on the LGS wall composed of prefabricated components, as well as the uniformly distributed load tests and shaking table tests conducted on the LGS wall utilizing the stud devised by the authors.