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 ε insensitive 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.

View full abstract

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.

View full abstract

The environmental destruction of the earth is becomes very serious social problem. In this study, the fundamental investigations of quantitative lifecycle assessments on bridge structures are performed by using Data Envelopment Analysis (DEA). The analytical bridge models are 11 kinds of deferent bridge systems such as steel, PC and so on, and lifecycle span of structures are set to 200 years. The parameters of DEA for lifecycle assessments are CO₂ emissions, lifecycle cost, using period of structures and one product meaning of bridge as used.
Form analytical results, steel rational plate girder bridge and PC girder bridge have a very good performance for environmental impact, also conventionally type bridges are 70 to 85% of performance as compared with these bridges. It is considered that the decrease of CO₂ and cost are effective for improvement of environmental impact performance.

View full abstract

The present paper concerns the road-traffic induced vibration from a viaduct and in the nearby soil. The procedure is to take a hybrid technique utilizing the field measurement data with the FEM analysis for the vibration prediction. The vibration measurements are conducted for test-runs of a 20tf-truck and for the ordinary traffic flows. The investigation is made on the dynamic behavior of the viaduct and the wave propagation at site in view of the involved state-of-the-arts. The low frequency around 3Hz from the structural vibration modes are pointed out to be transmitted from the foundation toward far distance with less damping. The present simulation predicts the concerned ground vibrations with good accuracy and works for checking the validity of the measures at the structural side and for developing the mitigation measure by use of WIB (Wave Impeding Barrier) in ground.

View full abstract

It has been around 120 years since the drainage business started in Japan, and maintenance of the drainage system enters the importance stage to sustain its function. Present paper proposes the decision-making method of the optimum renewal time and method of sewage concrete pipeline. Corrosion speed with the acid of sewage pipeline was quantitatively evaluated and the service time of the sewage pipeline was examined. Then, the period that pipeline reaches at each corrosion level and renewal cost were considered in the cost benefit analysis.

View full abstract

In earthquake resistant designs, for example, design specifications of highway bridges and building standard law, the engineering bedrock, where the S-wave velocity is about 400 m/sec, is used as the bedrock to specify the design spectrum. However, the seismic bedrock should be defined at the most upper part of the earth crust where S-wave velocities are about 3 km/sec. Therefore it is difficult to evaluate long-period ground motions excited by the deep underground structure from the design spectrum specified on the engineering bedrock. To evaluate the amplification due to the deep underground structure, the spectral ratio of ground motions on the engineering bedrock with respect to the seismic bedrock is computed by using the strong motion records in the Kanto Plain. In case of the shallow sediments, the amplification tends to be large in short periods. In case of the deep sediments, the amplification is large in both short and long periods. These results suggest that the ground motion spectrum on the engineering bedrock depends on the thickness of the sediments. Large variation in the amplifications for the sites with the same thickness is also observed and may be explained by the effects of the angle of incidence.

View full abstract

The present paper proposes a seismic risk management method for water supply pipelines to hospitals by cost-benefit analysis. The renovation program of water pipeline has a purpose to improve the pipeline itself and serviceability of hospitals. The proposed method can evaluate the fragility of building and lifeline facilities inside hospitals, and can account seismic risk for emergency supply to hospitals as well as that for water outage in surrounding areas. Also the method was applied to water supply systems distributing water to important hospitals, and it showed to be able to evaluate quantitative risk and validity of the method to chose vulnerable pipe segment in priority.

View full abstract

Rubber bearings show large changes in their performances due to the heat oxidation deterioration. Their performance changes in any construction site have not been clarified. Therefore, the long-term deterioration of rubber bearings is not considered in the current design method. In this research, performance changes of natural rubber bearings at any site could be estimated. It was clarified how the performance changes of natural rubber bearings depended on the time, the temperature and the size of the rubber bearings. Then, the design formula was proposed, which could estimate the horizontal stiffness of deteriorated rubber bearings in any construction site.

View full abstract

In this research, the loss factors for axial and bending deformations are statistically identified based on the lateral vibration experiment results of various cables that have been reported. It is confirmed that the bending loss factors [0.040-0.140] are relatively large for the axial loss factors [0.010-0.022], and that the loss factor of locked coil rope is about two times larger than those of other cables. Furthermore, the accuracy of the identified loss factors was experimentally confirmed by the independent tests of both axial and bending vibrations.

View full abstract

A one-dimensional model is proposed for static and dynamic analysis of box section steel bridge piers subjected to strong ground motions. The present formulation does not require experimental results nor shell analysis to obtain a constitutive equation of the model. The present analysis consists of two steps. The first step is to obtain the stress and strain relationship of the base plastic-hinge region, where local inelastic buckling is observed. The second step is to analyze static and dynamic responses of steel bridge piers by using fiber elements whose constitutive equation was obtained in the first step. The validity of the present model has been confirmed through comparisons with existing experimental results.

View full abstract

In case of design of the hybrid girder, there is a certain limitation of the width to thickness ratio of the web specified in some design codes. However,it has been reported experimentally that the composite action of the hybrid girder with much thinner web plate and RC slab can make the ultimate bending strength in positive flexure improve up to fully plastic bending moment. In this study, in order to investigate both the limitation of width to thickness ratio of the web and the ultimate strength of the hybrid girder which consists of different grades of steels for the thinner web and the flange, a parametric FE analysis is carried out for thr hybrid girders subjected to the positive flexure by varying the width to thickness ratio of the web, material strengths of the steels. It is concluded that the ultimate strength of the hybrid girder with thinner web and high yield strength steel, YP500 flange, can be evaluated by the full plastic bending moment and the reduction factor considering the neutral axis position and the width to thickness ratio of the compression area at the web.

View full abstract

This paper presents the test results of corrugated web girders under pure bending. Four different trapezoidal corrugation configurations, including a flat web, were used. All the girders tested failed due to local buckling of the compression flange at near the mid-section. The test results of bending behavior and ultimate strength were compared with the numerical analysis using the finite-element program DIANA. It was confirmed that the contribution of the corrugated web to the bending capacity is negligible and the ultimate strength can be estimated conservatively from the yield moment for only two flange sections. A predicting method of the ultimate strength considering local flange buckling was also proposed based on the parametric analysis of corrugated web girders.

View full abstract

In this paper, a new analytical method for free vibration problem of a simply supported rectangular plate with a crack is proposed. Features of the obtained theoretical solution for a plate are that only the deflection has a gap of the finite Fourier series shape along a crack line, and it continues along the other line.
The natural period according to some past research results has been compared in order to verify the effectiveness of this study. As some numerical examples, the following have been illustrated: Deflection surface of a plate , cross sectional forces[M_x(y), R_x(y)]along a crack line and the natural period with eccentricity and transfer of a crack line.

View full abstract

We examine the approximation properties and computational efficiency of three typical mesh connection technologies in the finite element analyses; that is, (1) the penalty method (PM), (2) the discontinuous Galerkin method (DGM) based on the Nitsche′s method and (3) the Lagrange multiplier method (LMM) in conjunction with the augmented Lagrangian method (ALM). After formulating the problem and briefly describing the solution methods of these methods, we carry out the series of numerical experiments to compare the performances of PM and DGM, as well as the LMM. Specifically, we examine the effects of the magnitude of penalty parameters in PM and DGM on the accuracy of the approximated displacements or tractions on the interface between the decomposed physical domains, on which the meshes topologies are compatible or incompatible and which, in some cases is identified with the material interface. We are also concerned with the performances and the computational efficiency of interpolation functions of different orders for the Lagrange multipliers in the ALM.

View full abstract

The Scaled corrector method has come to be acknowledged as an efficient bifurcation analysis procedure that does not require the eigenvalue analysis; however, its accuracy remains to be improved. As a remedy of this, we propose a new bifurcation analysis procedure that combines the mechanism of bifurcation of symmetric structure with the Scaled corrector method. The bifurcation mode is made highly accurate by decomposing Scaled corrector vector into a number of vectors and, in turn, choosing the predominant one. The usefulness of this technique was demonstrated through the application to the bifurcation analysis of the hexagonal truss dome to extract the bifurcation mode, and to search for the bifurcation point with high accuracy.

View full abstract

Failure processes of quasi-brittle inhomogeneous materials, such as rock, concrete, and etc., generally involve not only cracking within and/or between constituents but also closing and slippage between crack interfaces, especially when they are subjected to compressive loading. In this paper, we have developed a new analysis method, which enables us to simulate these processes in a consistent manner, by incorporating Lagrange multipliers and a cohesive crack model into the finite cover method (FCM). Several numerical examples are presented to validate the proposed method for failure analysis involving frictional contact on crack interfaces.

View full abstract

In this study, attenuation relationships of response spectra with 1%, 2%, 5%, 10% and 20% damping were constructed by using 3990 ground motions recorded by the JMA-87-type accelerometers. Based on the relationships, the amplitude ratios of response spectra with respect to the response spectrum with 5% damping were obtained to reveal the effects of damping ratio and JMA Magnitude on the shape of the amplitude ratio. Then, the verification of predicted response spectrum ratios obtained by attenuation relationships was discussed by using actual earthquake records.

View full abstract

The pre-stressed concrete girders with corrugated steel webs (PCGCSW) are known for there numerous advantages, including the accordion effect, a high shear strength etc. However, the mechanical analysis of these structures has always been a challenge for engineers, since the classical Euler-Bernouilli and Timoshenko theories do not account for the bending behavior and the stress distribution of the PCGCSW. A new theory, called the G3 theory was developed by Machimdamrong et al. (2004) and was found in good accordance with the FEM analysis. In this paper, we propose an extension of the G3 theory by taking into account the inelastic properties of the steel web. FEM analysis is used as a benchmark and gives results very close to the prediction of the elasto-plastic G3 theory.

View full abstract

In seismic design criteria for highway bridges, it is required to calculate the responses of structures to seismic force by the time-history nonlinear dynamic response analysis (abbreviated as NDA after). It is, however, extremely troublesome and difficult to obtain a design solution with NDA as the main response analysis method. In this study, the RBFN (radial basis function network) is applied to approximate the constraints on dynamic responses. As numerical examples, the method is applied to the seismic design of several RC piers of highway bridges, and finally is applied to the seismic design of the four continuous RC bridge with rubber shoes on its piers and abutments successfully.

View full abstract

We develop a multi-scale multi-physics analysis method for mass concentration diffusion and deformation in quasibrittle materials such as concrete materials, with a view to the evaluation of time-series environmental deterioration. The structural failure in micro-structures is evaluated by a simple damage model and analyzed by the voxel finite element method. The application of the homogenization method enables us to evaluate the change over time in macroscopic elastic and diffusion properties. First, we formulate the multi-scale mass concentration problem and the multi-scale deformation problem by applying the homogenization theory and present the weak-coupling analysis procedure. Secondly, we briefly summarize the modified voxel finite element method for the representation of microscopic damage such as cracks. Finally, several numerical examples are presented to demonstrate the capability of proposed method.

View full abstract

In order to investigate the time-dependent corrosion behavior for the steel structural members in boundary with concrete, accelerated exposure tests were carried out on model specimens in the authors' previous study. However, long-term corrosion tests over several years is required to clarify the corroded surface corresponding to service period of actual steel structures. In this study, the corroded surfaces of tested specimens were analyzed using regression trees and variograms to make the time-dependent corroded surface models. Numerical simulations using referential spatial statistics were also carried out on the models to estimate the corroded surfaces corresponding to the service period. From these analytical results, a prediction method for the remained plate thickness and a period of penetrating through a part of the members by the localized corrosion was proposed.

View full abstract

Bilinear hysteretic models are widely used for representing restoring forces of laminated rubber bearings. In this paper, the optimal bilinear model of a super high damping rubber bearing is proposed. At first, the bilinear model specified by the present design code is shown to be inaccurate especially in the large amplitude range. Then, optimal bilinear models under uni-axial and bi-axial seismic excitations are obtained with the aid of the multi-axial high order model and real-coded GA. Finally, equations for estimating the parameters of bilinear models are proposed, and they are found to be much more accurate than the present design code.

View full abstract

Many weathering steel bridges have been constructed in recent years. However, the performance of the steel in those bridges is not well traced and so little known. Against this background, “Committee on the Performance of Weathering Steel Bridges in Kyushu-Yamaguchi Region” in Kyushu Association for Bridge and Structural Engineering (KABSE), conducted the filed study of performance of weathering steel in bridges in the region. This paper describes the result of this study, based on which the factors that may influence the rust development are also discussed.

View full abstract

Recently, steel bridge members using the very thick plate, i.e., a few main girder bridge, are often used. If high strength bolted joint is applied to such the members, it becomes a long length bolt. It is considerable to use a large diameter bolt as a high performance bolted joint. In this study, the friction type of high strength bolted connection specimens were made on the thick plate using the large diameter bolt (M36) and the long length bolt (M22), then slip tests were carried out on these specimens. From these results, we discussed the applicability of the large diameter bolt and the long length bolt on the thick plate.

View full abstract

Elastic wave propagating through a layer on a rigid base was examined by ray theory which is quite available to Love wave phenomena. In this paper, Rayleigh wave phenomena were examined by the same approach. Displacement time histories due to Rayleigh wave propagation were measured clearly in certain exciting frequency band. For elastic layer of which Poisson's ratio is 0.5, ray theoretical approach ascertained successfully such phenomena and was verified by elastic theory.

View full abstract