structural design achieving floating artificial …― ―31 structural design achieving floating...
TRANSCRIPT
― ―31
Structural Design Achieving Floating Artificial Ground and Attractive Office Space
— Nichia Suwa Technology Center —
浮遊する人工大地と魅力的な執務空間を実現する構造デザイン― 日亜化学工業諏訪技術センター ―
* ** *** ****
* Junichi SASAKI: Takenaka Corporation佐々木 淳一:(株)竹中工務店
** Souichirou KUSHIMA, Ph.D.: Takenaka Corporation九嶋 壮一郎,博士(工学):(株)竹中工務店 *** Hisato OKUDE: Takenaka Corporation奥出 久人:(株)竹中工務店
**** Masayoshi IMAMURA: P.S. Mitsubishi Construction Co., Ltd.今村 雅泰:(株)ピーエス三菱
Contact: [email protected]: PCaPC beam, hybrid structure, long span, labor savingDOI: 10.11474/JPCI.NR.2018.31
SynopsisNichia Suwa Technology Center has an open office space that commands panoramic views of Lake Suwa. A dynamic and flexible structural frame floating in the air with a 28.8-m span and 6.4-m overhangs was constructed by applying the Gerber beam concept to a hybrid framing of precast prestressed concrete (PCaPC) and steel. The authors increased the percentage of PCa concrete in the members with the aims of saving labor in framework construction in a cold region and improving quality by ensuring accuracy.
Structural DataStructural Type: PCaPC structure, reinforced concrete (partially PCa) structure, and steel structureScale: 2 floors above ground, 1 basement floor, and 1 penthouse floorBuilding Height: 15mBuilding Area: 2,625.44m2
Gross Floor Area: 4,002.8m2
Owner: Nichia CorporationDesigner: Osaka Main Office, Takenaka CorporationContractor: Tokyo Main Office, Takenaka CorporationConstruction Period: Jan. 2016 – Nov. 2016Location: Suwa County, Nagano Prefecture, Japan
1. IntroductionThis building is a technology center with an open office space that commands panoramic views of Lake
Suwa. The whole office appears to float on the artificial ground constructed of a structural frame system, by which the authors have achieved a façade design that highlights the image of an advanced company while taking the surrounding abundant natural environment into the interior space (Fig.1).
2. DesignThe design concepts in the architectural planning phase were “creating a favorable research environment” and “enhancing intelligent productivity.” The aim was a symbolic work that would afford the company recognition in the surrounding areas (Figs. 2 and 3).
3. Structural PlanningTo match the architectural plan, the authors applied a combination of different types of structures so that
Fig.1 Full view of building
― ―32
the right structures might be used in the right places. The substructure is made of reinforced concrete (RC) while the superstructure is made of steel. Some parts of the RC structure have a PCa structure and a PCaPC structure in combination depending on the span (Fig.4).Since only the minimum areas are used for the building uses on the first basement and first (ground) level floors, they comprise two cores, one in the east and the other in the west. Each core has a pure rigid-frame structure consisting of eight PCaRC columns and PCaPC girders, thereby minimizing the number of structural members and ensuring all of flexibility, bearing capacity and stiffness. Using PCa columns and PCaPC girders simultaneously resolved two major issues, namely snow accumulation and a shortage of
construction workers. The second-level floor comprises a steel rigid-frame structure with braces to achieve an open space. The aim was to minimize the member sections and reduce the load on the substructure.
(1) Construction of Artificial GroundThe artificial ground constructed at the second-floor level is a structure that can support the superstructure stably. It also gives the impression of floating by showing a dynamic framework with a 28.8m distance (on-center) between the columns in the east and west cores and 6.4m overhangs from the east and west cores (Fig.5).The 28.8m span was achieved by pin-joining the steel beams to the PCaPC beams hanging over 2.2m from the cores and turning them into Gerber beams (Fig.6). The light-weight steel beams minimized the structure section, and PCaPC beams at the ends increased the stiffness, thereby enhancing the habitability of the office. The maximum height of the steel beams was 1,800mm considering the habitability of the upper habitable rooms. The maximum section of the PCaPC beams is 850mm by 1,500mm, and the specified concrete strength is 60MPa. The PCa members for integrated column–beam joints were fabricated in a
Fig.2 Concept diagram
Fig.4 Building section (upper) and Floor framing plan, Level 2 (lower)
Floating
Lake Suwa
Mountain
View Ventilation Sunlighting
Artificial ground
上部建物外形
ピロティ
実験室ゾーン
執務室ゾーン来客ゾーン
2階平面図(メインフロア)
1階平面図
Pilotis
Shape of superstructure
Floor plan, Level -1
Floor plan, Level -2(Main floor)
Laboratory Zone
Office ZoneVisitors Zone
諏訪湖Lake Suwa
N
Fig.3 Plan of each floor
3,80
06,
000
3,00
0
PHFLRFL2FL
1FLB1FL
Core(West) Core(East)
Steel structure
PC structureRC structure
2,60
0
6,400 16,000 28,800 16,000 6,400
Artificial ground2.2 2.23.2 3.2
Half PCa void slab(Reverted beam)16,000 16,00028,800 6,4006,400
Steel beam
Existing RC beam
3,20
03,
200
8,80
08,
800
8,80
0
PCaPC beam PCaPC beam :PC pressure bonded
Vertical brace
Fig.5 View looking up at 6.4 m overhang
2,200
納まり改善
Fig.6 Joint between PCaPC beam and steel beam
― ―33
many members as possible were made in the same shape, thereby enabling the same forms to be used for fabrication. For the PCa floor members, the cantilever floor members at the corners are large, measuring 6.4m by 3.2m, and two sides at the end of each overhang have rises. Special fixtures were used for form removal to prevent the members from being inclined. The same fixtures were used when erecting the members (Fig.11).
factory and then erected and tensioned on site.A 6.4m overhang was constructed by integrating a half PCa void slab into a 3.2m overhanging PCaPC beam in a reversed beam style. This style facilitated the design of an exposed slab on the underside of the slab, an under-floor air-conditioning system on its top side, and a structural design that looks like a 6.4m overhanging slab.Combining these Gerber beams, PCaPC beams, and large-scale overhangs helped balance the long-term stressed condition of the artificial ground, leading to construction of stable ground (Fig.7).
(2) Construction of Open Office SpaceThe office space above the artificial ground was made an open space with a uniform column diameter of 139.8mm by applying all the horizontal forces to the vertical braces (Fig.8). The vertical braces are concentrated, well balanced, and aligned with the core positions of the substructure, thereby minimizing the sections of the horizontal brace members that ensure the roof stiffness. Moreover, the authors used a combination of a pure rigid-frame RC substructure and a steel superstructure with braces to balance the story stiffness ratios of the whole building.
4. Construction(1) Fabrication of PCa MembersBecause the project site is in a cold region, as many RC members as possible were precast to improve their workability. Fig.9 shows the shapes and layout of the members and Table-1 lists their quantities.The PCa column members were designed to have projections in the east and in the west (Fig.10). Therefore, concrete was cast only in the north direction.The PCaPC beam members were designed so that their column–beam joints might be integrated. As
Fig.7 Long-term stresses on artificial ground
16,000 16,00028,8006,400 6,400
3,2003,200
24,4002,200 2,200
PCaPC beam PCaPC beamSteel beam
Fig.8 Office interior
SG4A
SG3
SG1
SG3
SG1
SG4
SG2
SG4A
sb58M
CPB3
PB1
PB1
PB1
PB1
CPB1 CPB1
CPB1
CPB1
CPB1
CPB1
CPB4A
CPB2A
CPB2
CPB2A
CPB4 CPB2
CPB2
CPB2A CPB3
G1 G1
G1
G2 G2G2
G3 G3
G3
PG1A PG1A
CPG2
CPG2
PG1
CPG1
CPG1
CPG1A PG1A CPG2A CPG2A PG1B CPG1B
CPG2A
PG1
PG1
FG6
FG1
CPG2A CPG1BCPG2A PG1B
PG1A
CPG1B PG1B
PG1
G1
G2
G3
CPG2A
CPG2
CPG2
CPG1
CPG1
CPG1A CPG1A
C1 C1
C2 C2
F2F1
F3 F2a
2FL
RFL
PHFL
1FLGL
平均GL
2FL
RFL
PHFL
1FL
B1FL
3200
8800
8800
8800
3200
6400 6400 9600 9600 9600 9600 9600 6400 6400
1800
6400 6400 9600 9600 9600 9600 9600 6400 6400
73600
32800
73600
1695
6000
3800
2600
100
14095 3800
2600
3000
6000 15400
A
B
C
F
D
E
1 2 4 5 6 8 9 1073
1 2 4 5 6 8 9 1073
Fig.9 Layout of members
factory and then erected and tensioned on site. A 6.4 m overhang was constructed by integrating a half PCa void slab into a 3.2 m overhanging PCaPC beam in a reversed beam style. This style facilitated the design of an exposed slab on the underside of the slab, an under-floor air-conditioning system on its top side, and a structural design that looks like a 6.4 m overhanging slab. Combining these Gerber beams, PCaPC beams, and large-scale overhangs helped balance the long-term stressed condition of the artificial ground, leading to construction of stable ground (Fig. 7).
(2) Construction of Open Office Space The office space above the artificial ground was made an open space with a uniform column diameter of 139.8 mm by applying all the horizontal forces to the vertical braces (Fig. 8). The vertical braces are concentrated, well balanced, and aligned with the core positions of the substructure, thereby minimizing the sections of the horizontal brace members that ensure the roof stiffness. Moreover, the authors used a combination of a pure rigid-frame RC substructure and a steel superstructure with braces to balance the story stiffness ratios of the whole building.
4. Construction (1) Fabrication of PCa Members Because the project site is in a cold region, as many RC members as possible were precast to improve their workability. Figure 9 shows the shapes and layout of the members and Table 1 lists their quantities. The PCa column members were designed to have projections in the east and in the west (Fig. 10).Therefore, concrete was cast only in the north direction. The PCaPC beam members were designed so that their column–beam joints might be integrated. As many
members as possible were made in the same shape, thereby enabling the same forms to be used for fabrication. For the PCa floor members, the cantilever floor members at the corners are large, measuring 6.4 m by 3.2 m, and two sides at the end of each overhang have rises. Special fixtures were used for form removal to prevent the members from being inclined. The same fixtures were used when erecting the members (Fig. 11).
North
West East
Projection
Fig. 9 Layout of members
SG4A
SG3
SG1
SG3
SG1
SG4
SG2
SG4A
sb58M
CPB3
PB1
PB1
PB1
PB1
CPB1 CPB1
CPB1
CPB1
CPB1
CPB1
CPB4A
CPB2A
CPB2
CPB2A
CPB4 CPB2
CPB2
CPB2A CPB3
G1 G1
G1
G2 G2G2
G3 G3
G3
PG1A PG1A
CPG2
CPG2
PG1
CPG1
CPG1
CPG1A PG1A CPG2A CPG2A PG1B CPG1B
CPG2A
PG1
PG1
FG6
FG1
CPG2A CPG1BCPG2A PG1B
PG1A
CPG1B PG1B
PG1
G1
G2
G3
CPG2A
CPG2
CPG2
CPG1
CPG1
CPG1A CPG1A
C1 C1
C2 C2
F2F1
F3 F2a
2FL
RFL
PHFL
1FLGL
平均GL
2FL
RFL
PHFL
1FL
B1FL3200
8800
8800
8800
3200
6400 6400 9600 9600 9600 9600 9600 6400 6400
1800
6400 6400 9600 9600 9600 9600 9600 6400 6400
73600
32800
73600
1695
6000
3800
2600
100
14095 3800
2600
3000
6000 15400
A
B
C
F
D
E
1 2 4 5 6 8 9 1073
1 2 4 5 6 8 9 1073
Fig. 8 Office interior
φ139.8
16,000 16,00028,8006,400 6,400
3,2003,200
24,4002,200 2,200
Fig. 7 Long-term stresses on artificial ground PCaPC beam PCaPC beamSteel beam
Table 1 Quantities of members
Fig. 10 Shape of column member projection
Floor level -Work area Member Qty.
(pieces)
Memberweight(t )
Grossweight(t )
B1F‐East Column 8 7.75-10.04 63.96
1F‐West Column 8 14.16-15.05 115.71
1F‐East Column 8 9.52-10.16 78.72
1F‐East Girder 12 9.91-20.05 162.42
2F‐West Girder 12 15.80-24.13 236.26
2F‐West Beam 8 13.70-19.34 130.22
2F‐East Girder 12 15.80-24.13 236.26
2F‐East Beam 9 4.6-19.34 135.55
2F‐East Slab 11 5.06-8.51 63.22
2F‐West Slab 11 5.14-8.51 68.63
2F‐South Slab 12 4.73-6.27 60.21
2F‐North Slab 12 4.73-6.27 59.89
Table-1 Layout of members
North
West East
Projection
Fig.10 Shape of column menber projection
― ―34
概 要 日亜化学工業諏訪技術センターは,諏訪湖を一望できる魅力的な執務空間を有する技術センターである。
構造躯体で構築した人工大地により執務室を浮遊させることで,周囲の豊かな自然環境を室内に取り入れる
と同時に,先進的な企業イメージをアピールする外観デザインとしている。
メインの執務空間を支える人工大地は,PCaPC 造と S 造を適材適所に組合わせることで,居住性と安全性の
確保に加え,28.8m ロングスパンや6.4m 跳出しといったダイナミックな架構を実現し,空中に浮かせた。さ
らに,構造部材の数と断面を最小限とすることで,フレキシブルな空間を実現した。
施工面においては,躯体の PCa 化率を高めることで現場作業を削減し,寒冷地での施工効率・品質の向上
と,省人化による労務職不足の克服を同時に実現した。
(2) Erection and Tensioning of PCaPC BeamsBecause the withstand load of the carry-in route was 25t, the following erection program was incorporated in the design phase: splitting the PCaPC beams into three, carrying them on site, and then pressure-bonding the split members on site. The PCaPC beam members split into three were supported by timbering for installation. The PC cables were tensioned prior to injecting the joint mortar into the column capitals so that prestressing might not cause statically indeterminate stress. Because the authors were able to predict that the column capitals would move 3.3mm inside due to the deformation caused by prestressing, the capitals were shifted 3mm outside prior to installation.Steel liners were used at the joints between the PCa column capitals and the lower surfaces of the PCaPC beams, thereby reducing friction and ultimately preventing constraint of the deformation caused by prestressing. The authors also took care so that the timbering supports installed at the joints of the PCaPC beams might not constrain the deformation caused by prestressing during tensioning work. The tensioned members were therefore erected as accurately as ± 5mm or less.Because the tensioning work took place prior to the floor installation, the stress conditions differed greatly between the loads in the construction phase and in the design phase. The authors considered a tensioning sequence that would not induce excessive tensile stress at the pressure-bonded joints (Figs.12 and 13).
5. ConclusionNichia Suwa Technology Center has a dynamic and flexible structural framework that appears to float in the air. Its 28.8m span and 6.4m overhangs were achieved by using a hybrid structure that combines the features of both PC and steel structures.For the construction, the authors increased the percentage of PCa members and were thereby able both to save labor in structural work in a cold region and to improve quality by ensuring accuracy. The building was also well received by its owner, who noted that it provides a good research environment, taking in the surrounding abundant natural environment.Consequently, the authors have realized the architectural plan that was aimed at a symbolic work that would suit two purposes: an open office space commanding panoramic views of Lake Suwa, and a building that could establish the company in the surrounding areas. This project won the JPCI (Japan Prestressed Concrete Institute) Awards for Outstanding Structures and the JSCA (Japan Structural Consultants Association) Kansai Structural Design Presentation 2017 Award of Excellence.
Fig.11 Fitting used to hoist PCa floor member
Pressure bondedFixed end
Fixed end
16,000 3,2002,200 3,20028,800
PCa column
PCaPC beam Steel beam
Steel liner
PC single sliding Pressure bonded
Pressure bonded Pressure bonded PC single sliding
Fig.12 Framing structure of PCa columns and PCaPC beams
Fig.13 Installation of PCa columns and PCaPC beams