¹Graduate School of Science & Technology, Nihon University

Chiba, JAPAN

yasu@post.ocean.cst.nihon-u.ac.jp

　

²The Institute of Physical and Chemical Research

Saitama, JAPAN

hiro@atlas.riken.go.jp

　

³Department of Oceanic Architecture & Engineering, Nihon University

Chiba, JAPAN

saijo@ocean.cst.nihon-u.ac.jp

　

　

For the structural design of floating architectural buildings on which various kinds of environmental loads acts, first, the structural design has to be required to secure the structural safety relating to elapse, deformation, stress and motion. Besides, even if structural safety of buildings is saved, the following problem to be solved will be presented; the oscillation or vibration of floating structure giving uncomfortable feeling to people induced by environmental loads will lose the habitability and efficiency on work. Therefore, the structural design to be considered the physiological and psychological influence to human body becomes particularly essential to evaluate the habitability in the motion of floating structure.

　

The object of this paper aimed to study the evaluation of habitability for floating oceanic architectural buildings. After having reviewed several standards; ISO (International Standard Organization) describing about vibration and vertical motion, guideline for building vibration in Architectural Institute of Japan and others, we proposed a diagram expressed by four levels for evaluation of habitability in vertical motion. Moreover, we had calculated displacement responses of floating structural model using arranged significant wave in Tokyo Bay. In order to examine the validity of calculation procedure and the evaluation, we plotted the obtained results into the diagram, and summarized the conclusion.

　

　

With overpopulation of late years, living space for human beings has been compelled to expand to the ocean. The building on the sea where people aims to live is called oceanic architectural building. It is apparent the environment surrounding those buildings is different from the environmental land. Therefore, in the structural design of oceanic architectural buildings influenced by ocean environment, specifically, environmental loads of wave and wind, its structural members must be designed to secure the safety for structural damages like collapse, deformation, others. However, even if structural safety has been kept, and if the oscillation or vibration to be uncomfortable to the human beings appears, the habitability and utility of buildings will be hurt. Particularly, in floating oceanic architectural building, the structural design has to be considered with regard to the influence to human body caused by these oscillation and vibration. In this paper, we proposed an analytical procedure of calculation method in terms of load effect of environmental load, wave response analysis of oceanic architectural buildings and the evaluation of habitability in the specified vertical motion except horizontal and rotational motions. Using the floating structural model referred to PUKARI-Pier at Yokohama, MM21, we demonstrated displacement response of its model by wave load, and evaluated the habitability in accordance with that procedure.

　

　

　

In limit state design of buildings in Japan, two limit states relating to safety on structural performance and utility performance are prescribed by Japanese building code. In addition, another limit state on the habitability of floating architectural buildings has to be considered. This limit state arises from the oscillation of building and vibration caused by wave and wind load. The structural design of oceanic architectural building cannot avoid from the evaluation for habitability is relation to comfortable or uncomfortable feeling induced by the oscillation and vibration. We have shown the classification of limit state design in oceanic architectural building as the followings:

　

Habitability Limit State - Habitability Level

The limit state belongs to the level which does not hurt habitability due to comfortable or uncomfortable feelings induced by ordinary oscillation and ordinary vibration of the buildings.

　

Serviceability Limit State - Utility Level

The limit state belongs to the level which does not damage the use of the building, work and operation induced by oscillation, vibration and deformation.

　

Ultimate Strength Limit State - Safety Level

The limit state means that some structural member is damaged partially or the structure collapses totally by extreme forces.

　

　

In order to grasp the load effect of environmental load acting on oceanic architectural buildings, the calculation of expected value corresponding to the return period is required. Practically, the expected values of wave height and wave period are needed for wave load calculation. With regard to the return period connecting to the load effect, three levels mentioned as above; habitability level, utility level and safety level, can be listed up. Load effect level and return period of limit state design for oceanic architectural buildings are shown in Table 1.

　

Habitability Level

It means the evaluation by the level according to closest usual life. The degree of oscillation and vibration of buildings must be grasped by ordinary load occurred everyday. The return period on load effect corresponds to 1-year.

　

Utility Level

This level is judged by the purpose due to use of buildings, building owner and user. The return period corresponds to two to three times of use period of building.

　

Safety Level

Assuming that huge typhoon or tsunami hits the structure directly, return period of load effect sets up 50 or 100-year. Its level aims to secure the structural safety.

　

　

The ground of 1-year return period can be explained by the evaluation of displacement response in ordinary state of buildings. The utility and safety level are controlled by large magnitude of loads like appearance of once in several decades or several hundred years. One year is defined as the shortest term of climate change in Japan of four seasons. Therefore, its calculation by short period than one year such as several months or half year is not rational. By those reasons, 1-year was adopted as the return period for habitability level.

　

Most standards and guidelines have dealt with frequency range from 1.0 (Hz) to 100.0 (Hz) with regard to frequencies of buildings on land in vertical direction with reference to the actual earthquake which had happened in the range from 3.0 (Hz) up to 30.0 (Hz). In case of floating oceanic architectural buildings, it must be considered by the motion due to low frequency range less than 1.0 (Hz) of wave period. As to the frequency range from 1.0 (Hz) to 30.0 (Hz), there are many data, for example, Guidelines for the evaluation of habitability to building vibration (AIJ, 1991), Reiher & Meister (AIJ, 1991), ISO standard (ISO 2631/2, 1989) are well known. But, in frequency range between 0.05 and 1.0 (Hz), data are still lacking. Figure-1 shows an evaluation diagram between 0.05 (Hz) and 50.0 (Hz) for habitability in vertical motion, which had been drawn in reference to three represent lines mentioned below.

　

　

　

　

The evaluation domain of oscillation in vertical direction was classified into three performance levels shown in Figure 1. Table 2 shows the definition of three performance levels; living level, office work level and work level.

　

　

　

The procedure on evaluation for habitability of oceanic architectural buildings is shown.

　

　

In practical, the structural design level in habitability does not accord with the level in habitability satisfied with the use of building, return to Step 2 and trace its procedure repeatedly until satisfaction.