Search

A method for an evaluation of the building structure response reduction by soil‐structure interaction (SSI) based on the seismographs of the soil‐structure system is presented. In the proposed method, a simplified SSI model is employed, and the parameters of model are determined by system identification. For system identification, both the inertial interaction (II) and kinematic interaction (KI) are considered. The method that indicates a reduction in the structure response by II and KI separately is also presented. The proposed procedures are applied to the observed records of the 2011 off the Pacific coast of Tohoku Earthquake. The findings demonstrate that the reduction effect of II is reduced when the response of building structure enters the inelastic range, and vice versa. In the superstructures with pile foundations, the reduction effects of KI are relatively smaller than those of II.

During the 2011 Tohoku-oki earthquake, a large number of response records from various types of buildings were obtained. The records give us the actual motions of buildings during the exceptionally large earthquakes that are considered comparable with design earthquakes. Various types of earthquake response records have been collected, and their properties with several buildings that will exhibit implications for structural design are discussed.

SUMMARY The 11 March 2011 M 9.0 Great East Japan earthquake generated significant long-duration shaking that propagated hundreds of kilometers from the epicenter and affected urban areas throughout much of Honshu. Recorded responses of a tall building at 770 km from the epicenter of the mainshock and other related or unrelated events show how structures sensitive to long-period motions can be affected by distant sources. Even when the largest peak input motions to the building is about 3% g, the strong-shaking duration was about 140 s. The 300- to 1000-s prolonged responses of the building are primarily due to a combination of site resonance (e.g. structural fundamental frequency ~0.15 Hz and site frequency ~0.13–0.17 Hz) and low damping (~1–2%) of the structure. Response modification technologies can improve the response of the building during future earthquakes. The need-to-consider risks to such built environments from distant sources are emphasized. Copyright © 2012 John Wiley & Sons, Ltd.

To grasp the effects of creep characteristics and rising temperatures on lead rubber bearings under wind load, long-duration cyclic loading tests and real-time online tests were conducted. From the loading tests, the lateral restoring characteristics of the lead rubber bearings in the small deformation range considering the creep characteristics were obtained. Analytical results using a simplified estimation method considering the small deformation characteristics of lead rubber bearings agreed well with the test results. From the online tests, the response properties of a base-isolated building under wind load were experimentally verified, and the validity of the modeling approach for lead rubber bearings and the wind response analysis method were confirmed.

Amplification characteristics in surface layer are often estimated by simple 1D structure for design input motions. In case of inclined engineering bedrock, it’s important to grasp effects on amplification characteristics. This paper presents the result of 2D-FEM analysis with one-side and two-side 10 degrees incline. Predominant period of 2D structure is 10 or 20 % shorter than that of 1D structure. The one-side incline slightly increases amplitude of 1D structure in the area where incident and diffracted waves interfere. Amplitude in the center of the two-side incline is larger than that of 1D structure due to a concentration of waves.

In order to clarify effects of earthquake motion and aging on dynamic characteristics of wooden houses, earthquake records at a seismically isolated wooden house for 10 years are summarized. The predominant period and amplification factor of the 2-story superstructure are compared, based on acceleration amplitude of earthquake motion, drift angle of first story, and time after completion. The predominant period is longer with increasing the acceleration amplitude and the story drift angle. The average predominant period for two years after 8 years is longer than that of first two years by 2.9-12.2%. The dependency of acceleration amplitude and time on the amplification factor is not clear.

In this paper, oscillatory properties of two school gymnasiums are investigated based on microtremor observation, forced vibration tests and seismic observation. The roof forms of the gymnasiums are different, one is a hip roof and the other is a gable roof. At each gymnasium, influences of the roof forms on the natural frequency or damping ratio, etc. are investigated. And using the observation and tests results, the validity of the dynamic analysis model is discussed.

A simple method for estimating the seismic amplification characteristics of surface strata is proposed by using the response spectrum method within the capacity-spectrum design scheme. The following presentations and discussions are made in this article: 1) to compute the natural and equivalent site periods based on the modal analyses of the multi-degree-of-freedom (MDOF) soil systems, 2) to determine the effective shear strain in surface soil, and 3) to examine the reliability and accuracy of the proposed method compared to SHAKE analysis.

To make sure the relationship between strong ground motions and building damages, dynamic earthquake response analyses of a building, which had a slight damage during the 2007 Niigata-ken Chuetsu-oki earthquake, are performed. Earthquake records at ground surface have been observed by the K-NET system near the building. Also the building responses were observed during after-shock. The analysis model of the building is estimated based on results of a push-over analysis. Sway and rocking impedances are also installed in this model. The predominant frequency of the building in elastic condition is corresponding to that in after-shock observation. It is demonstrated that the response of the building, which is calculated considering the nonlinear characteristics of soil and building during the main-shock, is larger than the estimated response based on the damage situation of the building.

In this paper, vibration characteristics of 43 middle-rise reinforced concrete buildings located in Kyoto city were investigated based on microtremor measurements. The buildings can be divided to three types by judging from the structural specifications. The vibration characteristics of soil around the objective buildings were also investigated. As the influences of soil-structure interaction were evident, we used a model including swaying and rocking behavior of soil in the analysis. The natural frequencies of the three-type buildings were compared, and their statistical properties were evaluated.

A recently proposed three-dimensional (3D) linear method for examining soil-building interactions based on an input seismic wave field is, after some improvements, applied to estimate seismic building responses in the reclaimed zone of Tokyo Bay, where ground motions include a considerable amount of surface waves, thus reconfirming the effects of the method in a different situation. A seismic wave field involves seismic waves propagating in a 3D medium. The proposed method was developed with the goal of adequately treating seismic surface waves trapped by a (several-kilometers) deep underground structure in a soil-building interaction system. Two simulations were carried out. The first simulation successfully reproduced surface, downhole, and building accelerograms that were recorded at one borehole station during two medium-sized earthquakes. In the second simulation, seismic responses of a midrise RC model building and a wood model building were favorably calculated at the other borehole station...

The Building Code of Japan (the Building Standard Law of Japan) has been changed from the former prescriptive type into a performance-based type in June, 2000. This paper presents the evaluation procedures for seismic performance of seismically isolated buildings against major earthquake motions newly introduced to the Building Code of Japan in October, 2000. The evaluation procedures apply the equivalent single-degree-of-freedom (ESDOF) system, equivalent linearization and response spectrum analysis. The basic concept of seismic design spectra for major earthquake motions is (1) basic design spectra defined at the engineering bedrock, and (2) evaluation of site response from geotechnical data of surface soil layers. The principle of evaluation procedures is that the predicted response values should not exceed estimated limit values. The evaluation criteria of each portion of a building are (1) the isolation system shall be designed so that the maximum response displacement does not exceed the design limit displacement, and (2) the structure above the isolation system and the foundation and structural elements below the isolation system shall be designed so that the working stress does not exceed the allowable stress. The scope of application of the evaluation procedures is (1) buildings not exceeding 60 meters in height, and (2) base isolation buildings on the soil layers excluding very soft soils.

The Building Research Institute (BRI) launched a 5-year research and development project on Smart Materials and Structural Systems in 1998 as part of U.S.-Japan cooperative research efforts. Smart Structural Systems also called as Auto-adaptive Media are defined as systems that can automatically adjust structural characteristics, in response to the change by external disturbances and environments, toward structural safety and serviceability as well as the elongation of structural service life. Smart materials and systems have been developed and studied.

The seismic design provisions of buildings in Japan was revised toward a performance-based structural engineering framework in 2000. The provisions provide two performance objectives: life safety and damage limitation of a building at two corresponding levels of earthquake motions. The design earthquake motions are defined in terms of the acceleration response spectra specified at the engineering bedrock to take account of the soil conditions and soil-structure interaction effects as properly as possible. The seismic performance shall be verified by comparing the predicted response values with the estimated limit values of a building.

The Building Standard Law of Japan and related Enforcement Order and Notifications have been substantially revised since the year 2000 to introduce a performance-based regulatory and deregulation system for building control systems. Up to then, time-history analyses were mandatory for isolated buildings and had to be specially approved by the Minster of the Ministry of Construction (MOC). Simplified design procedures based on the equivalent linear method for seismically isolated buildings have been issued as “Notification 2009 — Structural calculation procedure for buildings with seismic isolation” from MOC, and are now integrated into the Ministry of Land, Infrastructure, and Transportation (MLIT). Along with Notification 2009, “Notification 1446 of year 2000 — Standard for specifications and test methods for seismic isolation devices” was also issued. Buildings with heights equal to or less than 60m and that are designed according to these Notifications, including base isolated buildings, only need approval from local building officials, and no longer require the special approval of the Minister of MLIT. This paper summarizes: 1) some statistics related to buildings with seismic isolation completed up to the end of 2001; 2) simplified design procedures required by Notification 2009 of year 2000; and 3) performance of seismic isolation devices required by Notification 1446 of year 2000.

The good performance of seismically isolated structures during the 1995 Kobe earthquake persuaded structural engineers, isolator manufacturers and housing construction companies to undertake a coop...

This paper proposes a response spectrum method (RSM) for evaluating nonlinear amplification of surface strata (SS) overlying an engineering bedrock (EBR). The proposed RSM follows the procedures below. (1) Represent the response characteristics of SS on EBR by a multi-lumped mass model with shear springs and damping coefficients. (2) Calculate a period T1, a mode shape {U1} and a modal damping factor ƒA1 for the first vibration mode. (3) Evaluate the equivalent shear wave velocity Vse of SS. (4) Evaluate the amplification factor R1 of the surface to EBR at T1 using the Haskell matrix of two strata consisting of an equivalent SS with Vse and ƒA1 on EBR. (5) Evaluate the displacements in SS from R1{U1}, and hence evaluate the shear strains. (6) In accordance with nonlinear relations between shear modulus (G), damping factors (h) and shear strains, replace soil constants G and h by those corresponding to strains. (7) Return to step (1) with revised G and h. Iterate these procedures until T1 becomes stable. (8) After T1 is converged, calculate the response distributions in SS. The results obtained by the proposed RSM are compared with those by “SHAKE” in terms of the response spectrum at the surface as well as distributions of displacement, shear wave velocity and damping factor in SS. The applicability of the proposed RSM for evaluating the nonlinear amplification of SS is confirmed through the comparative studies.

This paper outlines shaking table tests and their results for an active seismic response control system that uses fuzzy optimal logic (FOL). The test results confirmed the validity of the vibration control effect of this seismic response control system. The results of this study lead to two conclusions, that the effectiveness of this FOL control system can be increased by modifying the membership function, and that the results of seismic response control tests can be qualitatively evaluated by simple simulation methods.

Shape Memory Alloys (SMA) exhibit stable superelasticity between a reverse transformation finish temperature (Af) and approximately 30°C above Af, and therefore can sufficiently work as a superelastic material for structural use in building under the temperature in a construction environment. In order to verify the potential self-restoration capacity of mortar beams containing superelastic SMA reinforcements, static loading tests were conducted, and the results were then compared with those for a beam containing steel wires. The comparison indicates that (1) after maximum deflection, the mortar beam with SMA can return to an about one-tenth deflection compared with the maximum, (2) the range of deflection of the mortar beam with SMA is more than seven times that of the beam with steel, and (3) wide single crack can occur at the critical section due to a weaker bond force between SMA and mortar.

The Building Code of Japan (the Building Standard Law of Japan) has been changed from the former prescriptive into performance-based type in June, 2000. This paper presents the evaluation procedures of seismic performance of seismically isolated buildings against major earthquake motions newly introduced to the Building Code of Japan in October, 2000. The evaluation procedures apply the single-degree-of-freedom (SDOF) system, equivalent linearization and response spectrum analysis. The basic concept of seismic design spectra for major earthquake motions is: 1) basic design spectra defined at the engineering bedrock, and 2) evaluation of site response from geotechnical data of surface soil layers. The principle of evaluation procedures is that the predicted response values should not exceed the estimated limit values. The evaluation criteria of each portion of a building are: 1) the isolation system shall be designed so that the maximum response displacement does not exceed the design limit displacement, and 2) the structure above the isolation system and the foundation and structural elements below the isolation system shall be designed so that the working stress does not exceed the allowable stress. The scope of application of the evaluation procedures is: 1) buildings not exceeding 60 meters in height, and 2) base isolation buildings on the soil layers excluding very soft soils.Copyright © 2002 by ASME

The dynamic earth pressures during earthquakes have been observed on both sides of an embedded foundation for about 30 events. Some characteristics of dynamic earth pressures were extracted from the observations. The main findings obtained in this study can be summarized as follows. (1) The phase characteristics of earth pressures between both sides of the foundation show remarkable dependence on the frequency components of acceleration motions. (2) The earth pressures on lateral sides of the foundation are strongly related with horizontal velocity motions of the foundation. (3) The peak values of earth pressures have shown a tendency to increase with increase of lower frequencies contained in accelerograms on the ground surface. (4) The fact that the earth pressure has strong relation with the velocity motions of the foundation may be roughly explained by means of a simplified one-dimensional wave propagation theory for a soil rod model.