Based on the disjoining pressure concept, volume change of several kinds of hardened cement paste (hcp) is investigated. As the hcp shows a hysteresis regarding adsorption and desorption isotherm, disjoining pressure of water in hcp is evaluated with the proposed equation led from equilibrium between disjoining pressure of water and elastic force of skeleton. In addition, the averaged thickness of adsorbed water is evaluated through water content and specific surface area which was measured by vapor absorption isotherm and B.E.T. theory. As a result, all the relationships of hcp between averaged thickness of adsorbed water and disjoining pressure of water were on the same curve. The proposed theory for hcp can also explain the volume change after hysteresis, shrinkage without decreasing the equilibrium relative humidity, and the larger shrinkage of concrete containing aggregate with the larger specific surface.
For achievement of long-term durability of concrete structures, it is important to get knowledge about properties of concrete. Nowadays, properties of concrete are determined by experimental or predicting from empirical equation. However, it is difficult to predict concrete properties at long-term, because it is impossible to do experiment. Therefore, it is necessary to make a model by considering its microstructure. Microstructure is a key for predicting the properties of concrete. Some properties are determined by microstructure such as C-S-H, calcium hydroxide, pores, unhydrated cement particles, interfacial transition zone and these interactions. In this study, we investigated dynamic elastic modulus of hardened cement pastes in view point from microstructure. Backscattered electron image was used for acquiring the microstructure image and autocorrelation function (ACF) of each phase was calculated by these images. The ACF was applied for reconstructing three dimensional structures from two dimensional images. Finally, three dimensional structures were used for calculating dynamic elastic modulus of specimen. It was cleared that the prediction result of dynamic elastic modulus used micro indentation result was good agreement with experimental result in high W/C.
This paper describes equations for estimating maximum along-wind load on the structural design of a wind turbine tower in the operational condition. Some parameters are derived from field measurements and wind tunnel tests. Furthermore, the wind load estimation method is based on the gust effect factor method. First, the application terms and fundamental wind load estimation methods are shown. Second, the modeling of parameters of the equations is investigated. Lastly, the gust effect factors and maximum overturning moments are calculated using the suggested equations, and compared with field measurements. The estimated maximum along-wind loads agree with the field measurements, thus confirming the applicability of the equations.
It is known that wind damage to houses is more strongly affected by maximum gusts rather than maximum wind speeds. However it is not easy to indicate a meaningful relationship of the damage to the wind properties, because the wind damage is strongly affected by the numerous conditions of construction. In this paper, we proposed a new damage analysis procedure using correlation analysis with the quantified structural conditions of houses. This method can estimate more clearly that the structural conditions of houses as well as the gust speeds information are a significant factor to wind damage spreading.
In order to estimate the building damage during earthquakes in the future, we should perform damage prediction analysis considering both strong motion characteristics and response characteristics of buildings since we are now becoming possible to predict strong motions with sufficient accuracy. It is indicated that the damage of a building due to an earthquake is greatly influenced by the regional characteristics of buildings in addition to construction types, floor numbers, and construction ages. In this paper vibration characteristics of reinforced concrete (RC) buildings in different regions with different design levels are collected by microtremor measurements. Then we construct the damage prediction models that reflect regional differences of the acquired vibration characteristics based on the nonlinear building models proposed by Nagato and Kawase (2001). Then we use observed strong motions and synthesized Nankai earthquake waveforms as inputs to perform nonlinear response analyses. We construct vulnerability functions for four different numbers of floors, two different ages, and five different regions. We found that when we use regionally corrected models in Kochi region for the hypothesized Nankai earthquake the damage ratios will be 18% reduced on the average.
This study is to propose a method to evaluate cumulative damage of steel buildings under plural strong seismic actions. A series of time history analyses on a one degree-of-freedom non-linear system are conducted for three strong ground motions simulated for Nagoya district. Comparing the results of the analyses, a method to predict the maximum and cumulative response values for successive action of the three motions from those of one single motion is proposed. Time history response analyses of thirty (30) storied steel building models with and without response control systems are conducted to verify the proposed method. In addition, seismic performances of these model buildings are evaluated based on “JSCA Performance Menu”. Finally, the method and procedure to evaluate seismic performances of buildings for strong motions that act on the buildings one after one are proposed.
The two microtremor features, namely, the H/V spectra and the dispersion curves, on the basin periphery area were investigated to the southern Osaka basin. In the coastal area with a gentle basement inclination, the S-wave velocity profile identified from the two features gave the appropriate basement depth. On the other hand, in the terrace area with a steep basement inclination, the S-wave velocity profile identified from the dispersion curves was quite different from the one obtained from the down-hole S-wave logging. As the reason of the experimental results, it could be interpreted that microtremor H/V spectra are likely to be robuster than microtremor dispersion curves in the estimation of the subsurface structures with an inclined basin-bedrock interface. On the basis of this usefulness of microtremor H/V spectra, the past basin model in southern part in Osaka plains was improved using three-component microtremor records observed at a hundred stations. The depth of the basin-bedrock interface of the presented model was deeper in the coastal area and shallower in the terrace area than that of the past model.
Some nonlinear vibration responses were observed in cylindrical tank with water on shaking table driven by periodic sinusoidal wave. The linear vibration theories never explain occuring these vibration phenomenon. It is reported that they might be caused by initial imperfection of cylindrical shell. Assuming that these responses were caused by geometrical nonlinearity of the system with elastic container and water , we have been studying these nonlinear responses from both theory and vibration test. Here, we report subharmonic vibration responses that branch out on periodic stationary response of the vibration system. They make instability regions on response curves, where subharmonic vibration responses become significant vibration. We show several mechanisms that generate the instability regions of subharmonic vibration on response curves.
RIMD (=Rotating Inertia Mass Damper) has been developed to mitigate an earthquake response of structure. Three type of RIMDs, which were a parallel connecting type, a series connecting type and both combined connecting type, for SDOF system were studied by comparing frequency transfer functions for various excitation patterns. The proposed combined connecting type was found to be able to suppress the response in wider frequency range compared with a conventional TMD. The parallel connecting type well reduced the absorbed energy amounts for the earthquake excitations.
It is known that apparent mechanical performance improve on partial compression perpendicular to the grain. The equation in the construction standard follows the assumption that the surface deformation at additional area is exponential shape. However the factor to determine its shape has not been investigated. In this research the influence of supporting condition was studied. It was suggested by FEM analysis that the factor is different among them and was confirmed by the experiments. Consequently, three different factors were proposed instead of 1.5/Zo (height of specimen) in current standard, 2.5/Zo for normal, 3/Zo for triangle and 5.5/Zo for double triangle.
This paper presents a new hybrid connection for installing an steel frame inside an existing RC frame. Three one-bay one-story non-ductile RC frames were retrofitted by steel braced frames with the help of hybrid connection technique. The scale factor of test specimens was 1/4-1/3, to model a low-rise school building designed according to the pre-1971 Building Standard Law of Japan. The specimens were tested under constant axial forces and cyclic horizontal loading. The experimentally observed behaviors exhibited that the propose hybrid connection can successfully transfer a relatively high shear force between the surrounding RC frame and the installed steel braced frame. Moreover, in case of non-ductile RC frames, the hybrid connection perfectly prevents the possible brittle shear failure of boundary RC columns. The hybrid connection method, in addition to obtaining superior structural performance, provides ease in construction at a building site, and minimizes the vibration, noise, and concrete dust of the retrofitting process.
An experimental study on non-slip-type exposed column bases proposed by the authors, subjected to both cyclic horizontal laodings and variable axial forces in the limits of compression was carried out to make bending moment characteristics of the column bases and to propose models of restoring force characteristics. In addition, the same experiments on conventional exposed column base were conducted to show the effectiveness of the proposed column bases. The following conclusions were drawn from the experimental results: 1) The restoring force characteristics of the non-slip-type column bases become linear-from-origin-type under variable axial forces, and the column bases sustain the self-centering performance reducing residual deformation of a building after an earthquake. 2) The energy absorption capability of the proposed column bases is higher than the conventional ones, and the energy absorption capacity is almost the same under between constant and variable axial forces. 3) The gap between the edge of the base plate and the foundation of the proposed column base under variable axial forces in tension and compression becomes smaller than the conventional one. 4) The gap between the base plate and the foundation of the proposed column base is not generated unless the axial force exceeds half of yield strength of all the anchor-bolts, therefore the bending resistance of the column base is not reduced by the shearing resistance of the anchor-bolt in the case of the lift-off of the column base.
Shaking table tests of steel cantilever beam-column with H-shaped section were performed under horizontal two-directional and one-directional excitation. All specimens collapsed with the excessive accumulation of displacement u. Even though the specimen was subjected to the uniaxial ground motion, the failure mode was the lateral instability... That divergent and convergent behavior of the response was well predicted by the critical axial force for convergence of the beam-column subjected to two-directional excitation derived from the theory proposed by the author.
This paper describes elasto-plastic behavior of the beam to column connections composed of steel members by filling the joint with concrete or mortar. The three tests were carried out using sub-assemblages subjected to cyclic lateral loading. The test results verified that the connections could be regard as rigid. If the mortar did not crush, the connection could transfer the ultimate moment of the beams. The analysis employing the yield condition of Mohr-Coulomb is applied to estimate the yield strength and maximum strength of the connections. The formulae of the strength are verified through comparison with test results.
Assessment of the mechanical fire safety performance of Japanese traditional floor-beam assemblies is conducted by predicting the post-fire bending stress of timber beams and validated by full scale 45minutes furnace tests with specimens of floor-beamassembly of different spans and intervals of the beams. The study intends to explore the possibility to widen the application of and to develop theoreticalmethod for the design of traditionalwooden construction. It has resulted in the prediction of the fire safety performance of floor-beamassemblies by thismethod closer to reality than those by the conventional deformation-based assessment.
A period region of strong ground motions which have close relationship with actural damage to buildings was reinvertigated including the data by the 2007 Noto-hanto Earthquake and the 2007 Niigata-chuetsu-oki Earthquake, where 1.5-2 sec. and 2-2.5 sec. period dominated records were observed for the first time as the site with building damage data. I found that 1-1.5 sec. period region response had closer relationship with the actual damage to buildings, compare to the previously proposed 1-2 sec. region. The reason why 1-2 sec. in stead of 1-1.5sec. region had close relationship with actural damage to buildings in the previous study was investigated. I found the reason was that the JR Takatori record in the 1995 Hyogoken-Nanbu Earthquake which brought about severe damage around the observation site happened to have a large response around the 2 sec., in addition that 1.5-2 sec. and 2-2.5 sec. period dominated records which were observed in the 2007 Noto-hanto Earthquake and the 2007 Niigata-chuetsu-oki Earthquake were not included in the previous data set.