In this paper, a statistical pattern recognition method based on time series analysis is implemented in flexible risers. This method uses a combination of Auto-Regressive (AR) and Auto-Regressive with eXogenous inputs (ARX) prediction models. The flexible riser model used in this paper is experimentally validated employing a proposed numerical scheme for dynamic response of flexible risers. A modal-based damage detection approach is also implemented in the flexible riser model and its results are compared with the ones obtained from time series analysis. The numerical results show that the time series analysis presented in this paper is able to detect and locate structural deterioration related to fatigue damage in flexible risers. Finally, considering the case study results presented in this paper, the presented AR-ARX prediction model works better than the modal-based damage detection method.

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The ultimate flexural strength of composite steel girders with compact sections is examined through experimental investigation and elasto-plastic finite displacement analyses to develop a reduction factor of the ultimate flexural strength. A two-point loading test of a composite girder was carried out to verify the numerical modeling by comparing the experimental and numerical results. Then, a parametric study was performed using finite element analyses to investigate the effect of concrete crushing on the flexural strength of composite girders constructed using SM570 grade steel. Observations made by comparison of the ultimate flexural strength obtained from the experimental and numerical results with that according to the AASHTO and Eurocode show that the existing reduction factor equations are conservative and can be relaxedwhenthestrengthiscontrolledbycrushingofconcreteslab. Anewreductionfactorfortheultimate flexural strength for composite I-girders under positive bending is proposed.

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It is quite complicated for the linear differential equation of beam deflection to be expanded as to varying cross section. But, once a tapered beam element is solved, its nodal stiffness relations can be adopted into a general discrete analysis of framed structures. In this paper, the method of separation into rigid displacement and deformation, which has been developed in the geometrically nonlinear analysis, is found to have a fitness for dealing with the varying beam elements; and typical two types of tapered 2-D beams are discretized from their linear solutions into the geometric and second-order stiffness relations.

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The authors investigated into the fundamental characteristics of the external forces on foundation piles from flowing liquefied soil by experiments under a centrifuge condition. The followings were obtained as conclusions; the viscous force resulting from the ground flow velocity of liquefied soil was dominant when model ground was completely liquefied. On the contrary, the external force resulting from ground displacements was governing the pile deformation when the model ground was not liquefied, or partially liquefied. Furthermore, when the liquefied soil was overlaid with a non-liquefied soil, external forces resulting from ground displacements of the non-liquefied soil was dominant.

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In most more economically developed countries an ever growing percentage of existing structures is threatened by obsolescence in the short- to medium-term—either because of structural deficits due to deterioration, or due to functional aging. To ensure sustained serviceability and safety of these structures, maintenance interventions are utilized, which allow partial or complete structural rehabilitation. However, such maintenance interventions have to be economically reasonable, that is, maintenance expenditures spent have to be outweighed by expected future benefits. For this purpose, we propose herein a novel optimization formulation for maintenance planning based on cost-benefit criteria. The usefulness of the proposed approach lies in the fact, that it not only allows to determine optimal sequences of maintenance times, rehabilitation levels and inspection qualities, but also allows to specify economically optimal lifetimes and acceptable failure rates of structures. The modeling of structural deterioration and maintenance, as well as the setting of all relevant cost factors is discussed in detail. Numerical examples investigate the effect of imperfect execution of maintenance actions and functional aging.

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A new constitutive model of swelling soil material is proposed to evaluate its mechanical characteristics. In the case of the compacted bentonite material, nonlinear behavior appears more dominantly than ordinary clay materials in the consolidation test. The original Cam-clay model cannot describe these characteristics observed in the compacted bentonite materials. Therefore, a new modeling that strain increment consists of linear summation of the swelling component and the elast-plastic component is introduced to describe the nonlinear behavior in the unloading stage. From the result of the simulation of the triaxial compression test, it is demonstrated that the stress pass and the stress and strain relationship are well simulated by the new model.

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The purpose of this study is to investigate the flexural strengthening effects of RC beams with hybrid FRP sheets consisting of high-modulus type continuous carbon fibers. Based on a preliminary hybrid design following mixture rules for the hybridization of high strength and high modulus types of carbon fibers, the hybrid fiber sheets are used to strengthen RC beams. Throughout a series of investigations of beam specimens under three-point bending, the hybrid fiber sheets consisting of high-modulus type carbon fibers as an externally bonded reinforcement can effectively enhance the mechanical properties of RC structures. And serviceability performances of structures such as cracking resistance, stiffness and steel yielding load etc., especially, can be enhanced. Moreover, through a rational design of hybrid fiber sheets, the stress drops due to the gradual ruptures of fibers are controlled and sufficient ductility is achieved by avoiding premature debonding. Finally, some indices for evaluating the strengthening effects of hybrid fiber sheets and the optimum mixture are also suggested and discussed.

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Mechanical behavior of particle-fluid systems is extensively studied in various engineering field such as geotechnical engineering, mechanical engineering and powder technology. Although observation of complicated behaviors including interaction between particles and pore fluid is essential, very few efficient techniques are available for this purpose. From this point of view an observation technique based on LAT (Laser-Aided Tomography) and PIV (Particle Image Velocimetry) was developed and applied to the permeability experiments involving a seepage failure. The LAT-PIV technique enables us to visualize not only the particle motion but also the pore fluid motion and evaluate them quantitatively.

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