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.