The starting point of the research on damping of shell and spatial structures is the panel discussion (PD) at the annual meeting of the Architectural Institute of Japan (AIJ) in 1995. The title of the PD was "Damping evaluation of buildings - accurate response estimation of buildings subjected to the large scale seismic forces or strong winds. The authors will review the past and the present of damping research on shell and spatial structures and think about the future of those.
In recent years, the Institution of the Long-Life quality housing for Wooden structure house is needed proper maintenance and evaluation of seismic performance. And the application of the vibration control structure for Wooden structure is also increasing. In order to evaluate seismic performance of wooden structure directly, it is useful that time-history earthquake response analysis is useful to evaluate the response about input energy of earthquake. In this report, we analyzed damping of wooden structure from the measured vibration data, and propose the damping model for Wooden structure. We compare response analytical result with experiment.
Since the 1990s, Architectural Institute of Japan has collected full-scale data of buildings based on vibration tests, earthquake and wind observation records, and has performed statistical analyses on vibration characteristics, such as natural periods and damping ratios. At first, collecting data and analyses was mainly conducted for general buildings and tower-like structures. Subsequently, the objective was expanded to various buildings and architecture, such as vibration-controlled buildings, shell and spatial structures and small-scale buildings, and analyses using full-scale data has been advanced. In this paper, we introduce the outline of database in these buildings and a part of analyses results.
This paper focuses on natural period and damping factor as a vibration characteristic of steel or RC-type buildings, and shows the results of trend analyses using full-scale data. Database is organized nearly 400 full-scale data from documents published in the past. The first-mode damping factors often used in design are 2% in steel buildings and 3% in RC buildings. Therefore, with reference to the database created, we compared them with damping ratios assumed for ordinary design. Also trend analyses was performed trend analyses on building heights, the first-mode natural period and damping ratios, furthermore about amplitude dependence of damping ratios.
The research committee in AIJ(Architectural Institute of Japan) collects and analyzes natural periods and damping ratio based on the full-scale measurement data. This paper shows the results of tower-like structures. The natural periods of the first mode are roughly proportional to the heights of structures. In the first mode, the damping ratio is negatively correlated with the natural period. Although it is only one case, the damping ratio of the first mode of a RC chimney tends to increase as amplitude of vibration increases.
Many observation records are recorded by the seismometer installed in the buildings during the 2011 off the Pacific coast of Tohoku earthquake. These observation records are analyzed, and the variability of the eigen period and the equivalent damping factor is considered much. In this paper, the results of the documents are integrated and reanalysis is carried out separately for each type of structure, building height, input level of earthquake ground motion. In addition, it's investigated about setting of an analysis model in high building evaluation from 1966.2 to 1998.12.
The natural period and the damping ratio of buildings depend on the amplitude of vibration. The authors have studied that for RC buildings. In this paper, 8 high-rise steel buildings were studied. Both the natural period and the damping ratio are dependent on the vibration amplitude of the building. In this paper, the damping characteristics during the 3.11 earthquakes were studied, especially.
Atsugi City, Kanagawa Prefecture, is set as a region for strengthening the earthquake disaster prevention measures of the Tokai Earthquake, and it is necessary to strengthen countermeasures in preparation for a large-scale earthquake that is said to be 88% probability of occurrence within 30 years. There are many dwelling houses, low-rise office buildings, etc. in Atsugi city, and it is considered indispensable to construct such a structural health monitoring system and observation network of small buildings. Especially the school building (36 elementary and junior high schools in Atsugi city) are bases where children stay for many hours, and also become evacuation centers in the event of emergencies, such as important structures that require immediate structural integrity assessment. With the final goal of evaluating the soundness of elementary and junior high schools in Atsugi city, we carried out ambient vibration measurements for accumulating the vibration characteristics of several elementary school buildings.
In earthquake resistant design of buildings, evaluation of vibration characteristics is important. In recent years, due to the increment of super high-rise buildings, the evaluation of response is important for not only the first mode but also higher modes. The knowledge of vibration characteristics in buildings is mostly limited to the first mode and the knowledge of higher modes is still insufficient. In this paper, using ARX model to earthquake observation records of a SRC building, characteristics of first and second modes were studied.
This paper investigated the accuracy of the seismic response characteristics of building evaluated by the autoregressive exogenous model (ARX), the subspace state-space system identification method (4SID), and the complex mode indicator function method (CMIF). First, the accuracies of the natural frequency, the damping ratio, and the specific mode shape identified by the three methods were compared based on linear seismic response analysis. Then, the dynamic characteristics of the SRC building were identified by the abovementioned three methods using the strong motion records of the 2011 off the Pacific coast of Tohoku Earthquake and its aftershock. From the comparison of these identified results, the characteristics of these methods were estimated.
The change of natural frequency of the building during an earthquake and earthquakes in the long term was investigated. The authors have studied the change of variation of 1st natural frequency and damping ratio. In this paper, 6 buildings were studied. Concerning to the low-, middle- and superhigh-rise RC buildings, the 1st natural period and damping ratio were studied and compared with past study.
Secular change in equivalent stiffness and strength of a SRC-type building was examined by analyzing seismic records of a long-term seismic observation. Identifying the predominant frequencies and the corresponding deformations from the observed records, the detailed relationship between equivalent shear-force and deformation of the objective building can be obtained, which relationship includes useful information about the structural state of the building. Further, it is demonstrated the single degree-of-freedom model follows the regulation of the relationship can explain the dynamic performance of the building.
Damping factor makes an effect in the response of buildings during earthquake. In design process, conventional values are used for damping factors of buildings. Recently the real measured data of damping factors have been collected and that characteristics are different from general ones. This paper shows the analytical results for changing values and characteristics of damping factors of buildings.
Damping factor makes an effect in the response of floor vibrations. In design process, conventional values are often used for damping factors. This paper shows the trend analysis of the real measured data of damping factors have been collected and conventional values in design process.
Natural period and damping factor are important values in seismic design. However, these values obtained by actual earthquake observation of buildings are affected by the soil–structure interaction. Therefore the characteristics of the building structure only are unclear. This paper focuses on the vibration characteristics of the structure itself using the records of large shaking table tests. Reinforced concrete specimens subjected to strong input motion were studied. Moreover, the effects of the experienced largest deformation on the vibration characteristics were investigated.
When performing dynamic design, it's necessary to set an appropriate damping model. In the linear region, the setting of initial damping model affects the response. In the nonlinear region, the combination of initial damping model and hysteresis model affects the response. In this regard, we consider that its characteristics are unclear in the nonlinear region. In this paper, we study the effect of the difference both initial damping model and hysteresis model on the dynamic characteristics of the structure. We use the ARX model for calculate the natural frequency and damping ratio. The results showed the difference of response due to difference of damping model. Also the difference of variation of the natural frequency and damping ratio are shown.
Although vertical vibration characteristics of buildings still remains unclarified, safety evaluations of structural members such as base isolators and long-span girders considering vertical motions are frequently required in building structural design process. In this paper, we identify the 1st vertical natural period and damping ratio of Steel, RC, and SRC buildings using ARX model from earthquake observation records.
Particle and cell positon control and sorting system is developed in the present work by exerting dielectrophoretic force on particle using rail-type, ladder-type and flip-type electrodes. In this study, the technology that can control the space and time intervals of particles flowing in microchannel flow and their timing (alignment control) is described. This is achieved by controlling the time characteristic of acceleration and deceleration forces exerted on particles using dielectrophoretic force and ladder-type electrodes. Particle motion and alignment performance are measured using high-speed camera. Further, perturbation analysis is made to solve and understand particle motion and alignment physics and to discuss their instability and alignment characteristics.
Tissue morphogenesis can be controlled by the coupling between biochemical and mechanical signals to derive the functional three-dimensional (3D) shapes of organs. To acquire a better understanding of the mechano-chemical coupling, we construct a mathematical model based on the understanding of the physical picture of ligand–receptor kinetics at the 3D cell surface. Simulations demonstrated that the coupling between the gene expression and cell shape occurs spontaneously to regulate the spatiotemporal gene expression at the tissue scale, indicating that the cell shape is a key regulatory link between multi-physical events or multi-scale phenomena at the subcellular and tissue scales.
Recent molecular dynamics (MD) simulation studies predicted that the phase transition to the interdigitated gel (LβI) phase, interdigitation, occurs in phospholipid/cholesterol bilayers under mechanical stresses. Here, we propose a free energy model of stretched phospholipid/cholesterol bilayers to explain the interdigitation. The model consists of the elastic energy, the surface energy on the bilayer-solvent interface, and the inter-phase boundary energy. The phase diagram from our model is in good agreement with that obtained from MD simulations. The energy balance among the energy components quantitatively explains the mechanical stress-induced interdigitation.
A numerical analysis is presented of cell adhesion in capillaries whose diameter is comparable to or smaller than that of the cell, where the solid and fluid mechanics of a cell in flow was coupled with a slip bond model of ligand-receptor interactions. Our results suggest that even under the interaction between PSGL-1 and P-selectin, which is mainly responsible for leukocyte rolling, a cell is able to show firm adhesion in a small capillary.
Structural properties of ionomer aggregations in a mixture of 1-propanol (NPA) and water have been investigated using coarse-grained molecular dynamics simulations. The dependence of NPA content on the ionomer structures was studied by systematically changing the NPA content in the system. The self-assembly behavior of ionomers into cylindrical bundle-like aggregates was observed for all NPA content solutions. The ionomer aggregation size was found to tend to be larger and more dispersive at higher NPA contents, although the ionomers aggregated into one cluster at all NPA contents.
Condensation heat transfer on the exterior surface of a vertical tube in the presence of noncondensable gas is investigated taking into account temperature variation of the tube and the coolant flowing within the tube. A heat transfer model is derived by employing energy conservation and the heat transfer coefficients of both the inside and the outside of the tube, which have been previously proposed. The model is compared to an experiment in the past, and a correction factor of the outer heat transfer coefficient is estimated. As a result, it is shown that the correction factor depends on the concentration of the gas mixture or the subcooling of the tube. Furthermore, a new expression of the outer heat transfer coefficient is proposed, whose correction factor varies against the subcooling smaller than the previous one.
We study nonlinear dynamics of flow velocity fluctuations during thermoacoustic combustion oscillations in terms of statistical complexity and complex networks. The multiscale-complexity-entropy causality plane enables us to show the possible presence of two important dynamics: noisy-periodic oscillations near the swirler exit and noisy-chaos in the shear layer between a vortex breakdown bubble in the wake of the centerbody and an outer recirculation region in the dump plate. We also observe the scale-free nature in the networks consisting of interactions between convective vortices.
This paper presents the investigation of momentum and heat transfers in the viscoelastic layer of a viscoelastic fluid flow. We measured time series of velocities and the temperature using a two-component laser Doppler velocimeter and a fine-wire TC probe in flows of a surfactant solution which is a viscoelastic fluid. From the examination of the turbulent statistics, the effective thermal diffusivity, the time series of velocity and temperature fluctuations, and the spectra analysis, it was concluded that the viscoelastic vibration in the viscoelastic layer transports a high temperature fluid on the heating wall to the outer region.
Brittle fragmentation of vesicular magma, which is a Maxwell fluid, during rapid decompression is driven by crack propagation in the magma. In this study, we have conducted numerical simulation of a crack propagation in a Maxwell viscoplastic material using the phase-field method coupled with finite element method. We have examined the effect of viscoplasticity on the crack initiation and propagation. The results show that phase-field model which Kuhn and Mueller proposed can represent the ductile/brittle transition of the crack in Maxwell viscoplastic material.
We have developed a coarse-graining method which allows for the extraction of molecular collective motion by eliminating the irrelevant degrees of freedom from a fine-grained atomistic system. More specifically, we construct non-Markovian coarse-grained models subject to the generalized Langevin equation based on the Mori–Zwanzig formalism from molecular dynamics trajectories of a Lennard–Jones fluid. Moreover, we find that the effective incorporation of multi-body interactions among coarse-grained particles via the iterative Boltzmann inversion ensures the faithful representations of static properties such as pressure and radial distribution function along with the hydrodynamics characterized by velocity autocorrelation function and mean square displacement.
Rupture processes of the main shock of the 2016 Kumamoto earthquake was estimated based on waveform inversion analyses using empirical Green's functions. The main asperity was located approximately 15 km northeast of the hypocenter. In the region between the hypocenter and Mashiki, both slip and slip velocity were rather small. Therefore, it is not appropriate to conclude that the damaging ground motions in Mashiki were caused by forward directivity effects. In the analyses, near-source strong ground motions were used. Possible effects of soil nonlinearity on the inversion results are discussed.
We will describe the ground displacements and the damage of structures, caused by direct earthquakes, including the Kumamoto earthquake2016. As for the relationship between the displacements and the structures, the meaning of damage is different, depending on the function of the structures. In addition, the method of identifying the location where displacement occurred and estimating the amount of displacement generated is still in the course of development. In this lecture, We will try to show the future direction of the measures and research in the future by organizing the situations of damage in large displacements.
We investigated the relationship between the characteristics of nonlinear soil response and site conditions at various seismic stations using a large number of strong motion records and a simple index of soil nonlinearity, DNL, which can be derived from seismic record only. We found that stations which show considerable amplification during weak motion tend to show the evidence of nonlinear soil response clearly in terms of DNL, while the stations with smaller soil amplification during weak motion did not show nonlinear soil response clearly even during strong motion. The relationship between soil parameters, averaged shear-wave velocity for soil layers for example, showed poor relationship to the nonlinear soil response characteristics at a station.
The widespread liquefaction disaster that occurred in the reclaimed land around Tokyo bay area during the Great East Japan Earthquake was alarming. Validating this disaster by simulation is needed to prevent any liquefaction that may occur during likely huge future earthquakes. To do so, not only accurate soil properties and appropriate input wave should be comprehended but also the finite deformation analysis that simulates the reappearance of liquefaction. When the soil properties were given, the upward wave was estimated in the foundation ground using a transfer method using K-NET record motions.
Records observed in bedrocks have been used to extrapolate seismic origin model. However, if non-linear response occurred in the surface ground, the influence of it on the records would not be negligible. In addition, multi-dimensional wave propagation can occur because most deposited grounds are neither horizontal nor even. Therefore, this study proposed a new estimation method for the incident wave to base rock from an observational record while taking into account non-linearity response of surface ground such as liquefaction phenomena and multi-dimensional wave propagation by using a soil-water coupled elasto-plastic finite deformation analysis code. In other words, through this achievement, a new utilization of the viscous boundary condition (VBC) will be proposed. In addition, the feasibility of the proposed method will be examined.
In order to understand the response of strong motion at the ground landfill in Tokyo Bay area, we conducted a seismic response analysis of a wide area. The area is a reclaimed land in Tokyo Bay, and it was modeled by three-dimensional FEM over 100m depth 8km north-south east-west 10km. Alluvium was expressed by the non-linear model. In the results of the displacement distribution and acceleration distribution, we found that there is a strong correlation with the alluvium base contour and buried valley.
Most of the existing damage prediction methods not only do not substantially take account of the nonlinearity of the ground but also are based on one-dimensional vertical evaluations. Therefore, multi-dimensional effects due to an irregular stratigraphic and bedrock structure are not taken into consideration. In this paper, two-dimensional elasto-plastic effective stress analysis is carried out noticing the irregularity of the ground stratification. As a result, complex interference between the surface waves and body waves provides not only inhomogeneous deformation but also localized and extensive damage at the ground surface.
The evaluation of seismic performance of a rock slope in a NPP site is conducted by supposing a sliding surface, calculating safety factors from the transient stress conditions and then searching the minimum value of those. Because of using a transient stress in the equilibrium, it is impossible to estimate the behavior of a supposed sliding block once after becoming the safety factor is less than unity. The influence of element failure on a sliding block behavior was investigated to enable to estimate the behavior of a sliding block under the condition of a safety factor is less than unity.
Earthquake motions include waves of various frequency bands ranging from low to high frequency. Notably, the difference in dominant frequencies affects the seismic stability of fill slopes. Hence, to analyze the deformation/failure mechanism during an earthquake, 1G shaking-table tests were conducted on saturated fill slopes considering the resonance phenomenon. Evaluating the seismic stability of the fill slopes depends on not only the magnitude of the acceleration but also the relationship between the natural frequency and the input frequency. Moreover, it is also important to grasp the change in the natural frequency associated with the progress of plastic deformation due to repeated loading.
In the 2011 off the Pacific coast of Tohoku Earthquake, extensive liquefaction damages were observed over a wide range of reclaimed coastal land. It is reported that, in Chiba prefecture, the big aftershock occurred 29 minutes after the main shock and it caused expanding the liquefaction damage. In this paper, using a soil-water-air coupled finite deformation analysis code incorporating the elasto-plastic constitutive equation “SYS Cam-clay model”, it showed that groundwater level rise due to main shock expands liquefaction damage during aftershock.In the 2011 off the Pacific coast of Tohoku Earthquake, extensive liquefaction damages were observed over a wide range of reclaimed coastal land. It is reported that, in Chiba prefecture, the big aftershock occurred 29 minutes after the main shock and it caused expanding the liquefaction damage. In this paper, using a soil-water-air coupled finite deformation analysis code incorporating the elasto-plastic constitutive equation “SYS Cam-clay model”, it showed that groundwater level rise due to main shock expands liquefaction damage during aftershock.
A slip on strike-slip fault causes flower structures and Riedel shear bands within the overlying cover. In our former research, the Riedel shear bands formation process was simulated considering the material imperfection in ground by utilizing the three-dimensional elasto-plastic finite deformation analysis code GEOASIA. On the other hand, it’s known that the existence of jog (geometrical barrier) has an important role on the formation process. This paper simulates a strike-slip faulting process considering jog as a geometrical imperfection in ground on the strike-slip fault. As a result, the formation processes unique to subsidiary fault such as fractal shear bands, P-shear, low and high angle shears appeared.
To investigate chaos excitation and the relation of it to the stochastic synchronization phenomena in the oceanic double gyre, numerical simulations are conducted using 1.5 layer reduced gravity quasi-geostrophic model driven by seasonal changing forcing with red noise. Results show that by adding red noise to external forcing, synchronization occurs at smaller parameters than the parameter in which it can occur without noise (that is, stochastic synchronization occurs) and the transition to the direction of chaos excitation occurs at larger parameters.
The double-gyre ocean circulation takes on two energy states; a high-energy level corresponds to an antisymmetric inertial subgyre, which in turn corresponds to the “non-large meandering” path of the Kuroshio and a low-energy level corresponds to an asymmetric inertial subgyre, which is the “large meandering” path. These two bifurcatation solutions occur to express the “blue-sky catastrophe” as nonlinear dynamics and vary with low frequency with periods of several years to several decades.
Internal gravity waves propagate in a form of ‘beam’ from a wave source in the atmosphere and the ocean. The corresponding solution is an exact solution of the Euler equations. In the present study, we consider ‘3-wave interaction’ of these beams. The 3-wave interaction among monochromatic waves is well-known to occur, but their dynamics among wave beams has not been elucidated so far. According to recent studies, occurrence of instability due to 3-wave interaction among wave beams depends not only on their amplitudes but also on their ‘width’. We demonstrate this fact by numerical simulation of the Euler equations.
Quasi-uniform nodes are easily generated with a spherical helix without optimizations. A shallow water model has been constructed that utilizes the excellent properties of the spherical helix using the RBF (radial basis function) method and has been evaluated with the standard test cases. The model is indeed spectral (third-order) in the advection of a Gaussian (cosine) bell over the poles (case 1). In the steady state non-linear geostrophic flows (case 2 and 3), the models with minimum energy and spherical helix nodes result in comparable accuracies.
This study concerns the mixing layer depth under stabilizing surface buoyancy flux (surface heating). The combined effects of earth rotation and stabilizing surface buoyancy flux against the wind-induced turbulent mixing needs to be considered. Two different length scales, Garwood scale and Zilitinkevich scale, have been proposed for the mixing layer depth. Here, we analyzed observed mixed layer depth obtained from Argo floats plus surface momentum and buoyancy fluxes estimated from satellites, finding that Zilitinkevich scale is suited for observed mixed layer depths than Garwood scale.
In seismic design, we should appropriately take into account of uncertainties in seismic inputs. We presented a worst-case analysis based on a random sampling approach with order statistics. In this study, we investigate the applicability of the method to design seismic motions, which of acceleration response spectrum at the engineering bedrock surface is specified by a target spectrum, incorporating uncertainties of their ground-surface characteristics. We present a probabilistic prediction method of worst-case response of moment-resisting steel frames under such uncertain seismic inputs.
In this paper, we use the architectural facade of Penta-graphene which is the molecular structure obtained by numerical calculation. The mechanical stability of the obtained Penta-graphene morphology is confirmed and its deformation amount and size are considered by elastic self-weight analysis. We will also mention feasibility of construction of Penta-graphene.
The environment of structural design changes from day to day, corresponding to the development of computer tools. To accelerate the practical application of structural optimization, it is important to understand the actual condition of the usage. Therefore, the questionnaire surveys are conducted at two events and a hearing from six structural engineers is organized. In this report, the results from those questionnaire investigations and the hearing are reported.
In order to apply the structural optimization in practical structural designs, it is important to clarify the demands and problems of structural designs. In this report, a statistical investigation on the questionnaire survey is studied to compare the structural optimization agenda and interests between researchers and structural designers. The questionnaire data is evaluated in the correlation analysis where the structural optimization agendas and interests are focused on difference of the answerer's structural design experience and affiliations.
In this paper, the simultaneous analysis of the form finding and the cutting pattern is shown by adopting the finite element technique with coordinates assumption of which the coordinate value is directly unknown quantity. The analysis model is membrane structures with cable reinforcement having difficulty in the simultaneous analysis. Our study adopts not a spline curve used well conventionally but Bézier curved surface to the decision of a cutting line. This analysis procedure is applied to a suspension membrane structure and a pneumatic membrane structure with cable reinforcement, and its effectiveness is confirmed from numerical results.
Avoiding the collapse of buildings under large-scale earthquakes and protecting people's lives is an important theme in structural design. We proposed a new type of PC steel bar brace for moment-resisting steel frames, which is referred to as displacement-restraint PC steel bar (DRB). The DRB can avoid a collapse mechanism of a specific unique story and the structure with DRB has robustness to extremely severe earthquakes. We study the optimal initial displacement of the DRB that minimizes the interstory drift angle in the time history response analysis.