Chapter 4: Retrofit/Strengthening of Buildings

RETROFIT/STRENGTHENING OF BUILDINGS

The application of unidirectional sheet-type materials is attractive for the retrofit/strengthening of structural components in buildings because the materials can be easily installed in limited areas and close spaces without need for significant changes to the structure in preparation. This causes minimum distress to the occupants of the building. Furthermore, since the material is resistant to corrosion, and inert to most influences (in the case of carbon) it is virtually maintenance free. It can be overlaid or covered by decorative coatings/finishes without concern about future continuous access.

Between 1987 and 1995, of a total of 615 structures retrofitted using Mitsubishi Chemicals Replark Sheet, about 59.3% was related to buildings. In 1995 about 12% of sales of Tonen's FORCA tow sheet was in the area of buildings. A significant percentage of Toray's Torayca cloth is also reportedly used for the same application. There has also been some limited use of the aramid fiber based FITS system for the retrofit of building components. These systems have been used for a variety of structural elements such as the seismic retrofit of internal building columns (Figs. 4.29 and 4.30), repair of cracked apartment floorboards (Fig. 4.31), reinforcement and strengthening of grossly deteriorated/spalled columns in office buildings (Fig. 4.32), seismic strengthening of deficient columns and walls in pinball parlors (Fig. 4.33), reinforcement of slabs in buildings and parking structures (Fig. 4.34) and seismic strengthening of columns in parking lots (Fig. 4.35) and in buildings (external) (Fig. 4.36). In a number of cases, the retrofit was carried out largely as an aesthetic measure or as a preventive measure after initial cracking/exfoliation/peeling of concrete was noticed, rather than as a means of strengthening severely deteriorated or weak elements.

(a)

(b
Fig. 4.29. Seismic strengthening of internal columns of a building in Chiyoda-ku, Tokyo. Tow sheet was wrapped circumferentially; 1,100 m² of material was used on this project.

Fig. 4.30. Seismic retrofit of edges of an internal column using Replark.

Fig. 4.31. Repair of cracked apartment floorboards with Replark.

(a) before retrofit

(b) after wrapping

(a) retrofit of columns.

(b) retrofit of wall
Fig. 4.33. Seismic retrofitting of columns and walls in a pinball parlor in Yokohama, Kanagawa Prefecture using FORCA tow sheet. A Total of 430 m² of material was used.

(a) cracked slab prior to retrofit

(b) retrofit with ductwork in plac
Fig. 4.34. Repair of a cracked slab using Replark without shifting utilities.

Fig. 4.35. Seismic retrofit of columns in a parking lot using FORCA tow sheet.

Fig. 4.36. Seismic strengthening of external rectangular columns at an elementary school in Higashi-Kurume, Tokyo, using FORCA tow sheet.

Although a large majority of structural elements in buildings have been retrofitted using sheet type materials, a few columns have been retrofitted using a combination of tape layup and tow winding (Fig. 4.37).

(a) application of vertically oriented sheet material

(b) circumferential windin
Fig. 4.37. Shear strengthening of columns using a combination of vertically oriented Replark and circumferentially oriented tow.

Table 4.6 gives a listing of different projects in which Replark sheet type material has been used for retrofit/strengthening of components in buildings.

Table 4.6
Projects Completed Using Replark Sheet Material
Date	Location	Description
1993	Kagoshima	"MN" Newspaper Building
1993	Hokkaido	"H" University Column
1993	Hokkaido	"S" Town Housing
1994	Tokyo	"O" City Housing
1994	Hokkaido	Sezar Center Building Wall
1994	Tokyo	Power Station Floor Slab
1994	Kanagawa	Apartment House Floor Slab
1994	Hiroshima	Elementary School, Exterior Wall
1994	Hyogo	"S," Plant Column
1994	Tokyo	Parking Garage
1994	Mie	"M," Plant Column
1994	Hokkaido	"M" Condominium Beam
1994	Hokkaido	"S" Condominium Beam
1994	Fukushima	"K" High School Exterior Wall
1994	Hiroshima	"O" Town Hall, Exterior Wall
1994	Hokkaido	JR Apartment House, Wall
1994	Kanagawa	Incineration Station, Beam
1994	Osaka	"S" Plant Wall
1994	Niigata	Condominium Floor Slab
1994	Okinawa	Power Station Floor Slab
1994	Hokkaido	"B" Town Hall
1995	Niigata	Mitsubishi Electric, Plant Floor
1995	Okinawa	Power Station Floor Slab
1995	Hiroshima	"H" High School Floor Slab
1995	Iwate	"M" High School Floor Slab
1995	Hiroshima	Nippon Express Warehouse Beam
1995	Mie	"N" Hotel Floor
1995	Osaka	"M" City Incineration Station Floor Slab
1995	Kanagawa	"S" High School Wall
1995	Fukuoka	"K" Gymnasium Column & Beam
1995	Hyogo	"S" High School Column
1995	Tokyo	"H" Building Column
1995	Hyogo	Apartment House Wall
1995	Niigata	Apartment House Foundation
1995	Fukuoka	"K" Library Column
1995	Osaka	"D" High School Wall
1995	Hyogo	"K" City Hall Wall
1995	Hokkaido	"H" Town Hall Column
1995	Tochigi	Local Government Office, Beam
1995	Hyogo	"F" Electric, Exterior Wall
1995	Osaka	"F" Insurance, Building Wall
1995	Tokyo	"T" Condominium Column
1995	Kagawa	Mitsubishi Chemical Corp., Plant Beam
1995	Osaka	"N" Railway Retaining Wall
1995	Shiga	"R" Gymnasium Floor Slab
1995	Osaka	"K" Gymnasium, Opening
1995	Hyogo	"N" Building, Column
1995	Hyogo	"S" Building Exterior Wall
1995	Tokyo	"H" Hall Column
1995	Hyogo	"N" Building Column
1995	Hyogo	"S" Apartment House Exterior Wall
1995	Hiroshima	"F" Park Column
1995	Tokyo	"T" Hospital Beam
1995	Kyoto	"K" City, Incineration Station Column
1995	Tokyo	"P" Building Beam
1995	Mie	"T" Chemical, Building Wall
1995	Hokkaido	"S" Building Beam
1995	Osaka	"S" Apartment House Wall

Table 4.6 (cont.)
Projects Completed Using Replark Sheet Material
Date	Location	Description
1995	Hyogo	"M" Building Column
1995	Okayama	"M" Chemical, Building Column
1995	Hyogo	"S" Building Column
1995	Osaka	"S" Apartment House Wall
1995	Hokkaido	"R" Building Wall
1995	Tokyo	"S" Hall Column
1995	Hyogo	"C" Apartment House Column
1995	Okayama	"M" Chemical, Plant Beam
1995	Tokyo	"Z" Building Column
1995	Tokyo	"M" Condominium, Column
1995	Hiroshima	"F" National Park, Column/Beam
1995	Tokyo	"I" City Hall Beam
1995	Hokkaido	"L" Apartment House, Beam
1995	Aomori	"F" Temple Beam
1995	Okinawa	"M" Building, Beam
1995	Tokyo	"G" Building, Beam
1995	Tokyo	"S" Trade Building, Beam
1995	Ibaraki	"A" Glass, Column & Beam
1995	Hyogo	"I" City Housing, Wall
1995	Wakayama	"O" Concrete Plant, Column
1995	Oita	"K" Residence, Column
1995	Hokkaido	"H" Sugar Plant, Wall
1995	Oita	"Y" Apartment House, Column
1995	Kanagawa	"S" Railway, Tower
1995	Tottori	"T" Works, Column
1995	Yamagata	"Y" Elementary School, Beam
1995	Osaka	"D" Department Store, Column
1995	Tokyo	"E" Chemical Building, Column
1995	Kanagawa	"K" Warehouse, Floor Slab
1995	Aichi	"K" Elementary School, Wall
1995	Hokkaido	"A" Courthouse, Beam
1995	Osaka	"K" Apartment House, Floor
1995	Tokyo	"H" Apartment House, Column
1995	Tokyo	"B" Apartment House, Beam
1995	Kanagawa	"T" Housing, Beam
1995	Kanagawa	"H" Hall, Column & Beam
1995	Hyogo	"H" Horseracing Track, Pier
1995	Osaka	"K" Residence, Beam
1995	Kyoto	"M" Construction Building, Beam
1995	Hokkaido	"D" Middle School, Beam
1995	Hyogo	"R" Broadcasting Station, Beam
1995	Miyagi	"O" Elementary School
1995	Shizuoka	"M" LPG Tank, Foundation
1995	Saitama	"M" Bridge Girder
1995	Osaka	"D" Elementary School, Column & Beam
1995	Tokyo	"F" Research Center, Floor Slab
1995	Ibaraki	"O" Elementary School, Floor Slab
1995	Fukuoka	"K" Elementary School, Beam
1995	Osaka	"T" Building Expansion
1995	Yamagata	"S" Harbor, Girder
1995	Tokyo	"K" Condominium, Beam
1995	Hiroshima	"M" High School, Beam
1995	Hiroshima	"N" Elementary School, Column
1995	Gunma	"K" Branch Office, Beam
1995	Hyogo	"H" Hall Column
1995	Hokkaido	"S" Town Hall, Beam
1995	Fukushima	"F" School, Beam
1995	Hyogo	"S" City Housing, Column
1995	Tokyo	"S" Elementary School, Wall
1995	Okayama	"A" Co., Beam
1995	Tokyo	"O" Restaurant, Column & Beam
1995	Tokyo	"H" Apartment House, Beam

Table 4.6 (cont.)
Projects Completed Using Replark Sheet Material
Date	Location	Description
1995	Aomori	"K" High School, Floor
1995	Tokyo	"S" Apartment House, Floor
1995	Saitama	"T" Residence, Wall
1995	Tokyo	"O" Building, Wall
1995	Hiroshima	"M" Road, Pier
1995	Okayama	"A" Plant, Beam
1995	Hiroshima	"S" Complex, Column & Beam
1995	Tokyo	"K" Hospital, Beam
1995	Tokyo	"W" Condominium, Beam
1995	Hyogo	"O" Fire Station, Column & Beam
1995	Hokkaido	"M" High School, Floor & Beam
1995	Hokkaido	"M" School, Foundation & Wall
1995	Ibaraki	"K" Oil Quay, Girder
1995	Tokyo	"S" Condominium Basement, Column
1995	Kanagawa	"S" Elementary School
1995	Tokyo	"S" Hall Column
1995	Hyogo	"K" University, Beam
1995	Tokushima	"M" Insurance, Column & Beam
1995	Hyogo	"F" Building, Column
1995	Fukushima	"O" Oil Building, Column
1995	Nagano	"M" Middle School, Column

Note: Project locations are identified by Mitsubishi Chemical Corp. by the first character only, e.g., "K"

Table 4.7 gives a listing of building-related projects in which Torayca cloth was used.

Table 4.7
Examples of the Use of Torayca Cloth
Date	Structure	Description	Client / Geographical Location	# of Layers	Qty (m²)
8/89	NTT office	Exterior wall crack repair	NTT
8/90	Exterior wall	Crack repair	Volume Retailer	1	2500
11/91	School building	Exterior wall crack repair	Tottori Prefecture	1	300
3/93	Floor slab	Box girder slab reinforcement	Metropolitan Expressway	2-3	1500
5/95	Condominium	Pilotis column seismic retrofit	Real Estate Co.		40
4/95	Columns in classroom	Repair, seismic retrofit	School		20
5/95	Hospital chimney	Reinforcement	University (Taiwan)		100
4/95	Columns in store	Seismic retrofit	Daiei Inc.		100
8/95	Columns	Seismic repair and retrofit	Condo Owner (Kobe)		50
8/95	Underground beam	Seismic repair	Condo Owner (Osaka)	V, H, 1 each	480
10/95	Insurance co. building	Beam reinforcement	Building Owner (Aomori)		300
11/95	Office bldg. columns	Ind. column seismic retrofit	Building Owner (Tokyo)	H 3-4	1000
12/95	High school building	Slab reinforcement	Aomori Prefecture		198*
1/96	Ferry office building	Ind. column seismic retrofit	Building Owner (Chiba)
2/96	High school building	Ind. column seismic retrofit	Hyogo Prefecture		25
2/96	Office building	Ind. column seismic retrofit	Building Owner (Tokyo)		180
3/96	Head office building	Ind. column seismic retrofit	Building Owner (Tokyo)		1500
4/96	Parking tower structure	Slab & ind. column seismic retrofit	Metropolitan Expressway		2349*
4/96	Gym column	Ind. column seismic retrofit	Town in Ishikawa Pref.	V1, H2	710
6/96	Apartment building	Seismic retrofit	Osaka Housing Center		416
6/96	Apartment building	Seismic retrofit	Osaka Housing Center		365
6/96	Apartment building	Seismic retrofit	Osaka Housing Center		462
7/96	Castle	Column seismic retrofit	Osaka Prefecture	H 2-3	1500
7/96	Local govt. office bldg.	Column seismic retrofit	Ministry of Construction	H1-3	600
7/96	Office building	Column seismic retrofit	Building Owner (Tokyo)		230

Note: V: Vertical Alignment of Fibers, H: Horizontal Alignment of Fibers. If no direction is given, fibers are oriented horizontally/longitudinally.
* represents total work area

Table 4.8 gives examples of the use of Tonen's FORCA tow sheet.

Table 4.8
Examples of the use of FORCA Tow Sheet
Date	Description of Project
8/86	Repair of Slab, Cargo Circulation Center
6/87	Repair of Slab, Cargo Circulation Center
9/89	Tonen Kawasaki Refinery
11/90	Beam, Hospital
1/91	Tonen Kawasaki Refinery
11/91	Warehouse RC, Beam, Takaragumi
3/92	Parking lot slab
4/92	Electric Power Plant
4/92	Tonen Kawasaki Refinery
5/92	Electric Power Plant
5/92	Electric Power Plant
8/92	Electric Power Plant
9/92	Tonen Kawasaki Refinery
11/92	Warehouse Co.
1/93	Electric Power Transformer Substation
2/93	Tokyo Adachi Ward, Sanatorium
3/93	RC, Metal Co
6/93	Beam, Tokyo Ward
9/93	Fiber Co. Plant
1/93	Bank
11/93	Electric Power Plant
11/93	Slab, Apartment (Kinki Area)
2/94	Slab (2^nd Step)
4/94	Physical Distribution Center
4/94	Window Frame of Bldg., Association
5/94	Plant, Film Co.
6/94	Plant, Oil Co.
7/94	Floor Beam, Kansai Electric Power
8/94	Department of Construction
8/94	Beam, Curare
9/94	Tank Base, Aomori Prefecture
9/94	Pool, High School (Tokyo)
9/94	Warehouse, Physical Distribution Center
1/94	Hotel, Wakayama Musashi
1/94	Nigata Prefecture
11/94	Floor Beam of Substation, East Japan Railway
12/94	Hotel, Chiba Prefecture Abiko City
12/94	Repair of Building
2/95	Dormitory, Takeda Drugs (Osaka)
3/95	Slab, Sendai City
3/95	Slab, Nishikawaguchi
3/95	Japan AT&T Building
3/95	Sonoda School
3/95	Basement Parking, Osaka Prefectural Office
3/95	Station, Kobe City
3/95	Junior High School, Minoo City
3/95	Sannomiya Station, Kobe City
3/95	Station, Hankyu Railway
4/95	Basement Parking, Osaka Prefectural Office
4/95	Umeda Station Parking, Hankyu Railway
5/95	Building, Dressmaking School
5/95	Slab, Okinawa Base
5/95	Repair of Central Building
5/95	Factory, Morinaga
5/95	Building
5/95	Building

Published: November 1998; WTEC Hyper-Librarian