The effectiveness of seismic displacement response control for isolated bridges, which behave nonlinearly at both the columns and the isolators, is studied using the LQR optimal active control. A typical viaduct is analyzed for evaluation. An extensive parametric study of weighting matrices is carried out to examine the effect on reducing the displacement response. The results indicate that the active control is effective in reducing the deck displacement at small control force levels. Further, the effectiveness of saturation of control force is investigated for preventing excessive control at large control force levels. Finally, the active control is compared with the passive control using viscous dampers.

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In order to evaluate the deterioration characteristics during the lifecycle of bridge rubber bearing, a series of long-term accelerated exposure tests are performed on four kinds of rubber materials widely utilized for bridge bearings. Different degradation factors are applied in these tests, such as thermal oxidation, ozone, low temperature ozone, ultraviolet radiation, salt water and acid rain. The test duration lasts from 96 hours to more than 6,000 hours. Mechanical properties of aged rubber specimens are measured and compared. The effects of pre-strain are investigated too. The ageing behaviors of each kind of rubber are made clear. The test results are fundamental to the prediction of rubber bearings’ durability.

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These authors, focusing on the seismic responses of a pile foundation of traffic viaduct, propose an innovative enhancement method of a pile foundation by surrounding cells like Wave Impeding Barriers (WIB) for design. The present WIB consists of a multiple number of soil-cement columns, which are arranged in cells around piles. Since nonlinear dynamic soil-pile interaction is unavoidable in strong earthquake motions at soft site, such behavior is simulated approximately by a two-dimensional FEM-BEM in time domain. The performance design is pursued by parametric studies in view of pile internal forces. Partial damage of the WIB makes the pile safe with less nonlinear response. The high-damping assumption for the WIB fill-in keeps the WIB within safe margin.

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Structures exhibit highly nonlinear characters under severe loads such as strong seismic excitations. Therefore, it is crucial to make nonlinear structural identification in civil engineering. However, nonlinear hysteretic structural identification is still a challenging topic due to structural model complexity and the strong noises existing in input and output (I/O) data. An efficient approach based on the incremental support vector regression (SVR) is proposed here to identify nonlinear hysteretic structural parameters on-line. Instead of the Gaussian loss function utilized in the least squares method, a novel εinsensitive loss function is employed in SVR, and therefore the suggested SVR-based approach produces robust and accurate identification results. Furthermore, as an incremental algorithm employed to train SVR in a sequential way, the presented SVR-based approach not only works rapidly, but also identifys nonlinear structural constitutive parameters on-line. The performance of the proposed approach is verified by a five degree of freedom nonlinear hysteretic structural identification problem, in which two cases (power parameter is known/unknown) are both investigated. The identified results show evidently that the proposed technique has potential performance in robustness and accuracy for nonlinear structural identification, even when the measurement data in the presence of noises.

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A mapping of shear-wave velocity for al of Japan is performed using “Japan Engineering Geomorphologic Clasification Map (JEGM)” which has been developed as a GIS-based ground condition map. At first, we calculate the average shear-wave velocity in the upper 30m (AVS30), which is a simple and useful predictor for estimating site amplification factors of peak ground velocity (PGV), for approximately 2,000 sites where shear-wave velocity has been measured in al over Japan. Geomorphologic units for al boreholes logging data are interpreted using land-clasification maps that are the base paper maps for the JEGM. Next, we examine the corelation between not only geomorphologic units but also geographical information derived from the JEGM and the AVS30 values. The AVS30s show some dependency with elevations, slope angles, and distances from mountains or hils. In order to develop the estimating model of the AVS30, multivariate regresion analysis is conducted using these geomorphologic indices. Then, we can achieve to create an AVS30 map with relatively high accuracy for al of Japan using the JEGM.

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The relationship between the seismic intensity and the reactions of expressways drivers was investigated based on the questionnaire survey conducted by Japan Highway Public Corporation after the 2003 Miyagi-ken Oki earthquake. Only 40 % of drivers were aware of the earthquake in the areas where the Japan Meteorological Agency (JMA) seismic intensity was smaller than 4.0. On the contrary, more than 80 % of drivers recognized the earthquake in the areas where the JMA seismic intensity was larger than 4.0. The abnormal vibration of the vehicle was indicated as the reason why the drivers recognized the earthquake. Hence, the seismic motion is considered to affect the safe and stable driving.

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Firstly, failure mode and shear strength of stud connectors were investigated based on push-out test results. Secondly, the practicability of a proposed analytical method was verified on the basis of a comparison with test results and the failure mechanism of the grouped arrangement was investigated. Lastly, parametric analyses on concrete strength and on the longitudinal spacing of stud connectors were conducted and shear strength reduction equations of the grouped arrangement of stud connectors were proposed.

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A rational method for the design of deep-water foundations of super long span bridges is desired. Attention is paid to the suction acting on the foundation bottom, which resist the rise of an under-water foundation during an earthquake. The results of a laboratory model experiment conducted in order to grasp the characteristics of suction are presented, and a rational seismic design method considering the efiect of suction is proposed.

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This paper proposes an analysis model that, based on fiber element analysis, appropriately evaluates the phenomenon—spalling of cover concrete by buckling of longitudinal bars under the mechanism of the formation of a plastic hinge in a reinforced concrete bridge column under cyclic loading—and presents a study of its suitability based on a comparison with cyclic loading testing of reinforced concrete bridge column models performed by the authors in the past. The results have revealed that by modeling the cover concrete as a beam with its thickness treated as effective height and considering controlling the force of the longitudinal bars pushing outwards based on the bending resistance of this beam, it is possible to estimate the deformation of the bridge column when the longitudinal bars buckle causing spalling of the cover concrete with relative accuracy.

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The two-level seismic design method using post-yield stiffness is proposed. The post-yield stifiness on the load —displacement relationship of the RC pier is found to be effective for the reduction of both the demand strength and the residual displacement under extreme earthquakes. Then, the two-level seismic design method is applied to the Unbonded Bar Reinforced Concrete (UBRC) pier that has the stable post-yield stiffness. The smaller cross section is designed than the optimal cross section of the conventional RC structure. The performance of the UBRC pier is verified by the pseudodynamic tests, and as the results it is confirmed that the UBRC piers can be rationally satisfied with the required performance of the two-level seismic design.

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A centrifuge model test with similitude of 1/20 is carried out to clarify the inelastic response character-istics of reinforced concrete members in the culvert type of underground structure. Numerical analysis simulating the centrifuge model test is carried out to confirm the applicability of numerical procedure considering the material non-linearity. It is concluded that the reinforced concrete member in miniature is similar to the actual member in mechanical properties and yielding of reinforcing bars was found in the centrifuge model test under the applied strong motions. The present numerical procedure had the possibility of predicting the inelastic response of soil-structure interaction during strong earthquakes.

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Stress drops of 168 earthquakes (focal depth ≤60 km, 4.4≤MW≤6.9) are estimated by a generalized-inverse method using strong motion records in Japan. Stress drops of crustal earthquakes are dependent of focal depths. Stress drops of reverse-faulting earthquakes are two times greater than those of strike-slip faulting earthquakes and stress drops of strike-slip faulting earthquakes are two times greater than those of normal-faulting earthquakes. These results are consistent with the crustal strength expected from a frictional law. Stress drops of intraplate earthquakes have more variation than those of interplate earthquakes, but are two times greater than those of interplate earthquakes on average.

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In a bridge which is equipped with a rubber bearing support and undergoes relatively large displacement of its girders during an earthquake, the girder and abutment collide in the case that the expansion spacing is not sufficient. However, it may be possible to improve the seismic performance of the overall bridge by constraining the displacement of girders by taking a measure such as reinforcing the colliding members or by installing collision absorbers. In order to use such seismic resistant structures, it is essential to clarify the behavior of the abutment subject to collision force. This paper reports on an analytic study of the characteristics of the dynamic behavior of an abutment and the soil behind it, and the seismic performance of the overall bridge when a bridge girder collides with the parapet wall of the abutment during a large earthquake.

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We propose a method to estimate phase velocities of the Rayleigh and Love waves using array observation records of three-component microtremors. Previous researchers have provided a method on the basis of the spatial auto-correlation (SPAC) method, assuming that the Rayleigh and Love waves are propagated in the same direction. However, this assumption seems to be poorly suited to microtremors, because of the various possible sources and the uncertain nature of microtremors. Thus, we formulate the SPAC coefficients for microtremors in a case where the Rayleigh and Love waves are propagated in different directions. From this, it is shown analytically that the phase velocities of surface waves can be calculated from the SPAC coefficients and that they are independent of the propagation directions of the surface waves.

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In the elasto-plastic constitutive model, bulk modulus is one of the most important parameters to control the change of effective stress under undrained condition. However, the experimental research on bulk modulus of sand during liquefaction has not been conducted so far. In this paper, therefore, the bulk modulus of Toyoura sand was measured directly during liquefaction using a hollow cylindrical torsional shear testing device equipped with a volumetric strain control device. This study found that the bulk modulus corrected by membrane penetration effect during liquefaction process is constant under relatively high confining pressure, and that the stress dependency of bulk modulus during liquefaction process is different from that during swelling process.

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An accurate method for remotely measuring structure microtremors is proposed by using an improved Laser Doppler Velocimeter (LDV). The remote microtremor measurements of a rigid-frame structure model and an existing RC rigid-frame structure are presented in order to verify the efficiency of the proposed method. Dynamic structural characteristics, such as the natural frequency and the fundamental mode shape, of the model and the RC structure are accurately estimated.

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Since the seismic behavior of pile foundations in a liquefiable ground is primarily affected by the behavior of the ground, this paper discusses the usefulness of equivalent linear analysis considering the reduced shear modulus of liquefied soil for evaluating the dynamic behavior of liquefied ground. A multilumped mass model having liquefied soil springs set by reduced shear modulus is then applied to damaged buildings to verify its applicability. Shear strain levels and shear modulus in liquefied soil are also evaluated using strong motion records. In this light, a method of evaluating the reduced shear modulus of liquefied soil is proposed for dynamic analysis of liquefied ground by equivalent linear analysis

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