Data Mining Practical Machine Learning Tools and Techniques

Dynamics of structures


 The spectral ratio between horizontal and vertical components (H/V ratio) of microtremors measured at the ground surface has been used to estimate fundamental periods and amplification factors of a site, although this technique lacks theoretical background. The aim of this article is to formulate the H/V technique in terms of the characteristics of Rayleigh and Love waves, and to contribute to improve the technique. The improvement includes use of not only peaks but also troughs in the H/V ratio for reliable estimation of the period and use of a newly proposed smoothing function for better estimation of the amplification factor. The formulation leads to a simple formula for the amplification factor expressed with the H/V ratio. With microtremor data measured at 546 junior high schools in 23 wards of Tokyo, the improved technique is applied to mapping site periods and amplification factors in the area.

Ground Motion Characteristics Estimated from Spectral Ratio between Horizontal and Verticcl Components of Mietremors.

The notion of fuzziness as defined in this paper relates to situations in which the source of imprecision is not a random variable or a stochastic process, but rather a class or classes which do not possess sharply defined boundaries, e.g., the “class of bald men,” or the “class of numbers which are much greater than 10,” or the “class of adaptive systems,” etc. A basic concept which makes it possible to treat fuzziness in a quantitative manner is that of a fuzzy set, that is, a class in which there may be grades of membership intermediate between full membership and non-membership. Thus, a fuzzy set is characterized by a membership function which assigns to each object its grade of membership (a number lying between 0 and 1) in the fuzzy set. After a review of some of the relevant properties of fuzzy sets, the notions of a fuzzy system and a fuzzy class of systems are introduced and briefly analyzed. The paper closes with a section dealing with optimization under fuzzy constraints in which an approach to...

Fuzzy sets and systems

http://www.ingware.ch/files/lagomarsino_et_al_2013.pdf

TREMURI program: An equivalent frame model for the nonlinear seismic analysis of masonry buildings

In many seismically active regions of the world there are large numbers of masonry buildings. Most of these buildings have not been designed for seismic loads. Recent earthquakes have shown that many such buildings are seismically vulnerable and should be considered for retrofitting. Different conventional retrofitting techniques are available to increase the strength and/or ductility of unreinforced masonry walls. This paper reviews and discuses the state-of-the-art on seismic retrofitting of masonry walls with emphasis on the conventional techniques. The paper reviews retrofitting procedures, advantages, disadvantages, limitations, effect of each retrofitting technique.

/pdf/a-review-of-conventional-seismic-retrofitting-techniques-for-31vm07oocw.pdf

A review of conventional seismic retrofitting techniques for urm

Static cyclic tests on lightly reinforced concrete shear walls

An equivalent frame model for seismic analysis of masonry and reinforced concrete buildings

Many of existing unreinforced masonry (URM) buildings are seismically vulnerable and require retrofitting. This paper investigates in-plane seismic behaviour of URM walls before and after retrofitting using fiber-reinforced polymers (FRP). Dynamic in-plane tests were carried out on five half-scale specimens with two different effective moment/shear ratios namely 0.7 and 1.4. The specimens were retrofitted on a single side using different types and structures of FRPs. The test specimens were subjected to a series of synthetic earthquake motions on a uni-axial earthquake simulator. The retrofitting technique improved the lateral strength and stiffness of the URM walls. Moreover, the fundamental frequency and the initial stiffness of each specimen remained approximately constant before and after retrofitting. During the test, the slender specimens failed in flexural. For specimens failed in flexural, the measured FRP axial strains showed that the strain distributions along the specimens' cross-sections are approximately linear even at failure. Hence, the flexural strengths of the specimens were calculated using linear elastic approach. The measured lateral resistances of slender specimens are approximately 130% of the calculated flexural strength. This difference attributed to the difference in the nominal ultimate strains of FRPs and the real values at failure. The measured axial strains in FRPs during this test were approximately 50% of its nominal values. In addition, the shear strengths of the squat specimens were calculated using two different models. The calculated shear strengths approximately range from 99 to 177% of the measured lateral resistances.

Aseismic retrofitting of unreinforced masonry walls using FRP

The behavior of seven one-half scale masonry specimens before and after retrofitting using fiber-reinforced polymer FRP is investigated. Four walls were built using one-half scale hollow clay masonry units and weak mortar to simulate walls built in central Europe in the mid-20th century. Three walls were first tested as unreinforced masonry walls; then, the seismically damaged specimens were retrofitted using FRPs. The fourth wall was directly upgraded after construction using FRP. Each specimen was retrofitted on the entire surface of a single side. All the specimens were tested under constant gravity load and incrementally increasing in-plane loading cycles. The tested specimens had two effective moment/shear ratio, namely, 0.5 and 0.7. The key parameter was the amount of FRP axial rigidity, which is defined as the amount of FRP reinforcement ratio times its E modulus. The single-side retrofitting/upgrading signifi- cantly improved the lateral strength, stiffness, and energy dissipation of the test specimens. The increase in the lateral strength was proportional to the amount of FRP axial rigidity. However, using high amount of FRP axial rigidity led to very brittle failure. Finally, simple existing analytical models estimated the ultimate lateral strengths of the test specimens reasonably well.

Pierino Lestuzzi

Papers

A review of conventional seismic retrofitting techniques for urm

Static cyclic tests on lightly reinforced concrete shear walls

An equivalent frame model for seismic analysis of masonry and reinforced concrete buildings

Aseismic retrofitting of unreinforced masonry walls using FRP

Static cyclic response of masonry walls retrofitted with fiber-reinforced polymers