A structural damage detection method using uncertain frequency response functions (FRFs) is presented in this article. Structural damage is detected from the changes in FRFs from the original intact state. The measurements are always contaminated by noise, and sufficient data are often difficult to obtain; making it difficult to detect damage with a finite number of data. To surmount this, we introduce hypothesis testing based on the bootstrap method to statistically prevent detection errors due to measurement noise. The proposed method iteratively zooms in on the damaged elements by excluding the elements which were assessed as undamaged from among the damage candidates, step by step. The proposed approach was applied to numerical simulations using a 2D frame structure and its efficiency was confirmed.

In order to reduce the environmental pollutions and develop a new type construction material with super lightweight and high strength, we did some fundamental studies on the mechanical behaviors. The three kinds of experimental samples were made of fly-ash and full hard polyurethane, whose special mix-ratio and producing methods are described in this investigation. The static mechanical characteristics were discovered in the three kinds of material tests, namely the compression test, the bend test, and the cleavage test. The mechanical behaviors of this new material are also compared with that of concrete in the investigation. The main results obtained in the study are : 1) the new material can be made of fly-ash and full hard urethane, 2) stress-strain relations are discovered in the tests, and 3) the new material can be used not only as reinforcement of steel structural system for seismic design, but also as expansion device for highway bridge, due to its large capacities of transformation, remarkable lightweight and high strength.

SUMMARYThe yield level of an insulator is one of the important parameters which are related to responses and absorbing energy under seismic input energy in isolated structures. The purpose of this paper is to determine the optimal ratios of yield force of the isolator (Q ) to the total weight of the structures (=). To obtain the optimal ratio, 1044 two-degree-of-freedom isolated bridge models, which have bilinear isolators, were selected. These 2-DOF isolated bridge models with superstructure isolation can consider pier #exibility and various parameters of the isolator. Two formulas for determining the optimal yield ratio are proposed and compared with the previous researches. RAE (the ratio of absorbed energy by the isolator to the total input energy) is related directly to structural responses, and Optimal Yield Ratio (OYR), de"ned as a yield ratio at maximum RAE, can be obtained from the relationship between RAE and Q /=. Here, we found that RAE is a reliable factor to evaluate OYR, and it is proportional to earthquake amplitudes under the same kinds of earthquake loadings. Using the proposed formulas, OYR is determined and the optimal yield force of the isolator can be obtained easily and reliably at a seismic isolation design stage.

First, cyclic loading tests were conducted on scaled‐down bridge column models using normal‐ and ultra‐strength fiber‐reinforced concrete made with polyvinyl alcohol fibers (PVA‐UFC) and normal‐ and ultrahigh‐strength rebars. The experimental results were compared, focusing on the relation between load and displacement, skeleton, crack distribution, and failure modes. Second, in order to evaluate the reproducibility of the cyclic loading test by finite element (FE) analysis, trace analyses were carried out. The FE analyses investigated the applicability of the conventional analytical model of concrete for PVA‐UFC. Compared with the experimental results, overall hysteresis loops and maximum strength responses were reproduced with sufficient accuracy by using adequate analytical models. Lastly, parametric analyses were conducted on varying cross‐sectional areas of columns, and the extent to which cross‐sectional areas could be reduced by using UFC was investigated.

As part of a comparative study on the United States’ and Japan's seismic design of highway bridges, three scale models of a reinforced-concrete bridge column are tested on a shake table for their seismic performance. Three specimens, one based on the ductility design method (U.S.) and the others on the working stress design method (Japan), are subjected to a set of successive earthquake ground motions with varying intensities. All three specimens showed good performance; however, the specimen of ductility design experienced less damage than those of working stress design. Analysis of test results showed that structural degradation in each column closely correlates with decrease in the transverse stiffness, increase in the hysteretic energy dissipation, and increase in the vibration period, of the column. Two damage indices, based respectively on effective flexibility and weighted cumulative hysteretic energy, are used to indicate the progression of structural degradation in a reinforced-concrete bridge column subjected to successive earthquake ground motions.

This paper summarizes the results of a comparative study on seismic design of highway bridges jointly undertaken by the U.S. Federal Highway Administration and Japan's Public Works Research Institute. The seismic design specifications for highway bridges of the two countries are reviewed and compared with respect to their design philosophies and procedures. Some major design parameters including design seismic forces, response modification factors and minimum support lengths are addressed in detail. The differences between the two specifications are illustrated via a design example of a reinforced concrete column for simple, two-span bridges common in both countries. Three different scale models of the column are designed in accordance with the seismic design specifications of the United States and Japan, and tested on a shake table for their comparative seismic performance. The results of the shake table tests are discussed separately in a companion paper.

<p>In this study, the experimental specimens composed by the extra-high tensile strength concrete called as ESCON and the high yield strength steels called as USD685 were prepared to clarify the seismic performance of the ultra high strength fiber RC columns under cyclic bending loading. Compared to the experimental results of normal strength RC columns, the yielding capacity and the maximum capacity of the high strength one were improved. In addition, the crack distributions and the failure modes were different by the polyvinyl alcohol fiber contained in ESCON. Moreover, the trace analyses using the Finite Element Method (FEM) of these experiments of RC columns were conducted. As a result, it was identified that the experimental hysteresis curves could be traced by FEA. Lastly, it was calculated that how much cross section with equivalent strength of the normal strength specimen by using ESCON and USD685 could be reduced. The calculations showed that the cross section of area of RC columns using these high strength materials could be reduced by about 40% of normal one.</p>

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