フィラデルフィア貯蓄銀行ビル(PSFSビル)における計画・意匠と構造・空調設備技術の関係

抄録

 Philadelphia Saving Fund Society Building (PSFS Building) is a high-rise office building constructed in Philadelphia, the U.S. in 1932, designed by Howe and Lescaze Architects. PSFS Building is known as one of the two skyscrapers referred in “The International Style” written by H. R. Hitchcock and P. Johnson and also known as the second overall air-conditioned office building in the U.S. However, since the introduction of overall air-conditioning was decided during the construction phase, two schemes coexisted: the scheme based on natural ventilation and day lighting and those based on air-conditioning. This indicates that PSFS Building has important characteristics for considering the history of development of high-rise buildings with the progress of engineering. Therefore this paper aims to clarify the relationship between planning/design and structural-engineering/air-conditioning of PSFS Building by investigation of the original architectural drawings and magazine articles published in the period of its construction and by comparison with the other high-rise building in the period.
 As for the relationship between structural engineering, planning and design, the followings were clarified. PSFS Building has four characteristics of the structural engineering: 1) the huge truss structure of the transfer floor, 2) the special column-beam connection of the east and west elevation of the tower, 3) the special framing in the lower portion facade, 4) the extensive use of knee-bracing to resist wind-pressure in the tower part. These are considered to have relation to features of planning and design as the followings: Firstly, the truss structure realized the stacking of the different functions such as bank demanding huge banking space and office demanding rational planning. Secondly, the extensive use of knee-bracings realized the rental office space without interior permanent walls and the expression of horizontal ribbon window of the tower part. Thirdly, the special framing in the lower portion facade realized the expression of huge planes. Among these, the use of knee-bracings in offices space was unusual method among buildings in that period. Moreover, this use of knee-bracings was related to not only the characteristics of the planning and design such as the placement of the vertical shafts to the south, the projection of columns to outside and the horizontal ribbon window of the tower, but also those of the structural engineering such as the huge truss connecting the lower portion and the tower part.
 As for the relationship with air-conditioning, the followings are clarified. The introduction of the air-conditioning in the lower portion was considered from the early designing phase and it had close relation to planning and structural engineering such as placing equipments on the transfer floor, where the huge truss was installed by the demand of planning, and matching them with the structural layout. Moreover, the expression of using the same finishing material to the exterior wall of the transfer floor as those to second and third floor was also considered. On the other hand, in the higher part, as the introduction of air-conditioning was decided during its construction, the followings were pursued: the T-shaped planning with operable windows resulted from the common method with other office buildings based on natural ventilation and lighting, the minimization of the space for equipments for securing maximum rentable floor. Especially regarding the lower part, it is notable that the space for equipments was intensively secured and integrated with the complicated structural engineering and that this integration led to the expression reflecting the aesthetics of the new age. Furthermore, the higher part, which was planned based on natural ventilation and daylighting, is suggestive even in the present day when natural ventilation and lighting are being reconsidered.