02-07-2013, 01:06 PM
JAPANESE DEVELOPMENT OF EARTHQUAKE RESISTANT BUILDING DESIGN
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INTRODUCTION
The Seismological Society of Japan was founded in 1880 by three European engineering
professors invited at the Imperial College of Engineering in Tokyo. The 1891 Nohbi
Earthquake (M 8.0) caused significant damage to then modern and western brick and masonry
construction in Nagoya city, killing 7,273, collapsing 142,177 and damaging 80,184 timber
houses. Brick and masonry construction was abandoned in Japan after the Nohbi earthquake
disaster. The Association for Earthquake Disaster Reduction Investigation was organized by
Japanese government in 1892 to develop the measures to improve earthquake resistance of
building construction.
Mr. Toshikata Sano (1880 - 1956), a pioneer researcher in earthquake engineering at the
Imperial University of Tokyo, visited San Francisco after the 1906 San Francisco Earthquake,
and recommended construction of reinforced concrete buildings in urban areas for the reason
of earthquake resistance and fire protection. He published "Earthquake Resistance of
Buildings" in 1914, in which he proposed the use of equivalent static horizontal loads in
seismic design of buildings, and suggested a seismic coefficient of 0.3 in the downtown
Tokyo area.
BUILDING STANDARD LAW (1950 - to date)
Building Standard Law, applicable to all buildings in Japan, was proclaimed in May 1950.
The purpose of the law is to safeguard the life, health, and property of people by providing
minimum standards concerning the site, structure, equipment, and use of buildings. The Law
requires that a building owner must submit, before construction work, an application to
building officials to confirm that the building, plan, site, structure and equipment satisfy the
provisions of the law. The law does not prescribe technical issues, but it refers to the Building
Standard Law Enforcement Order (Cabinet Order). Although the law and its accompanying
cabinet order have been revised from time to time, the law and cabinet order govern the
planning, design and construction of buildings in Japan.
DESIGN OF REINFORCED CONCRETE BUILDINGS (1950 - 1971)
The 1950 Cabinet Order required the reinforced concrete construction as follows: (1) ends of
longitudinal reinforcing bars should be hooked for anchorage; (2) specified compressive
strength of concrete should be not less than 90 kgf/cm2; (3) a column should be reinforced by
at least four longitudinal bars which were firmly fastened by tie reinforcement at a spacing not
exceeding 30 cm and 15 times the smallest diameter of longitudinal reinforcement (Fig. 1.a);
(4) the minimum dimension of a column section should be larger than 1/15 the clear height;
the reinforcement ratio of a column should be not less than 0.8 percent; (5) beams should be
reinforced by top and bottom reinforcement; spacing of stirrups should be not more than 3/4
of the beam depth and 30 cm (Fig. 1.b); and (6) the thickness of a structural wall should be 12
cm or more; the spacing of horizontal and vertical reinforcement should be 30 cm or less; an
opening should be reinforced with bars of 12 mm diameter or larger.
REINFORCED CONCRETE BUILDING DESIGN FROM 1971 TO 1981
The 1968 Tokachi-oki Earthquake (M 7.9) caused significant damage to buildings in Aomori
prefecture and Hokkaido with a death toll of 49. The number of totally collapsed buildings
reached 673; approximately 10 percent of reinforced concrete buildings in the affected areas
suffered some kind of damage including cracking. Short reinforced concrete columns
typically in school buildings failed in shear. The damage raised some doubt about the
earthquake resistance of reinforced concrete construction although no one was killed by the
collapse of reinforced concrete buildings.
The causes of damage were summarized as (1) poor concrete and reinforcement work, (2)
uneven settlement of foundation, (3) lack of shear strength and ductility in columns, (4)
failure of corner columns under bi-directional response, and (5) torsional response of
buildings. The AIJ recommended that (1) shear stress level in columns should be kept low by
the use of structural walls and by the use of larger section, (2) monolithic non-structural wall
should be included in design structural analysis, (3) amount of shear reinforcement should be
increased and placed effectively, and (4) ends of ties and hoops should be bent more than 135
degrees, or welded closed-shape hoops and spiral reinforcement should be used. Note that the
shear resisting mechanism of a reinforced concrete member was not understood at the time.
REINFORCED CONCRETE BUILDING DESIGN (1981 TO PRESENT)
The Ministry of Construction organized an integrated technical development project
(1972-1977), entitled "Development of New Earthquake Resistant Design." The 1978
Miyagi-ken Oki Earthquake caused damage to buildings with flexible first-story or with a
large eccentricity between the centers of mass and stiffness. Therefore, the Cabinet Order was
revised to the present form in July 1980 following the recommendations of the development
project and was enforced from June 1981. The allowable stress design procedure was
maintained. Major points of revision were listed below:
(1) Shear reinforcement ratio must be 0.2 percent or more in a reinforced concrete member,
(2) Design and construction of a building is made possible up to 60 m in height; the design
and construction of buildings taller than 60 m must be approved by the Minister of
Construction,
(3) Additional requirements were introduced in structural calculation; (a) story drift, rigidity
factor and eccentricity factor under design earthquake forces, (b) examination of story shear
resisting capacity at the formation of a collapse mechanism under lateral forces, © alternative
simple procedures for buildings with abundant lateral shear resisting capacity,
(4) Design earthquake forces were specified (a) by story shear rather than horizontal floor
forces, (b) as a function of fundamental period of the structure, © at two levels (allowable
stress design and examination of story shear resisting capacity), and (d) also for the
underground structures,
BUILDING DAMAGE FROM KOBE EARTHQUAKE
The 1995 Hyogo-ken Nanbu Earthquake, commonly known as Kobe Earthquake Disaster,
occurred at around 5:46 am on January 17, 1995. The magnitude of the earthquake was
intermediate and 7.2 defined by Japan Meteorological Agency. The earthquake hit a
populated area of Kobe City, killing more than 6,300 (including those killed indirectly after
the earthquake), injuring more than 40 thousands people, collapsing approximately 92,800
buildings and houses, and damaging approximately 192,700 buildings. Approximately 80
percent of the death were caused by the collapse of houses and buildings. The total loss was
estimated to be more than 9,914 billion yen. The property losses in buildings amounted to
58.5 % of the total loss.
The damage to reinforced concrete buildings may be characterized by (1) collapse in a middle
story in office buildings, (2) collapse in the first story in apartment and condominium
buildings, (3) significant loss incurred by the damage of non-structural members, (4) fracture
at the splice of longitudinal reinforcement by gas-pressured welding technique, (5) damage in
lightly reinforced beam-to-column connections, and (6) failure of foundation and piles.
CONCLUSIONS
The technical development of earthquake resistant-building construction reduced significantly
vulnerability of new construction. Although majority of existing buildings may achieve the
purpose of structural design, some of the buildings constructed prior to the development need
careful attention and may require retrofitting work.
The structural damage can be significantly reduced by regulating (a) the brittle modes of
member failures such as shear failure of reinforced concrete columns, (b) the discontinuity in
stiffness and strength along the height of buildings, © the eccentricity between the centers of
mass and stiffness in plan, (d) the irregular configuration of structures in plan, and controlling
the quality of construction work. The experience from the Kobe earthquake disaster indicated
the desirability of higher resistance of structures to control the damage for immediate use after
an intermediate earthquake.
[attachment=56315]
INTRODUCTION
The Seismological Society of Japan was founded in 1880 by three European engineering
professors invited at the Imperial College of Engineering in Tokyo. The 1891 Nohbi
Earthquake (M 8.0) caused significant damage to then modern and western brick and masonry
construction in Nagoya city, killing 7,273, collapsing 142,177 and damaging 80,184 timber
houses. Brick and masonry construction was abandoned in Japan after the Nohbi earthquake
disaster. The Association for Earthquake Disaster Reduction Investigation was organized by
Japanese government in 1892 to develop the measures to improve earthquake resistance of
building construction.
Mr. Toshikata Sano (1880 - 1956), a pioneer researcher in earthquake engineering at the
Imperial University of Tokyo, visited San Francisco after the 1906 San Francisco Earthquake,
and recommended construction of reinforced concrete buildings in urban areas for the reason
of earthquake resistance and fire protection. He published "Earthquake Resistance of
Buildings" in 1914, in which he proposed the use of equivalent static horizontal loads in
seismic design of buildings, and suggested a seismic coefficient of 0.3 in the downtown
Tokyo area.
BUILDING STANDARD LAW (1950 - to date)
Building Standard Law, applicable to all buildings in Japan, was proclaimed in May 1950.
The purpose of the law is to safeguard the life, health, and property of people by providing
minimum standards concerning the site, structure, equipment, and use of buildings. The Law
requires that a building owner must submit, before construction work, an application to
building officials to confirm that the building, plan, site, structure and equipment satisfy the
provisions of the law. The law does not prescribe technical issues, but it refers to the Building
Standard Law Enforcement Order (Cabinet Order). Although the law and its accompanying
cabinet order have been revised from time to time, the law and cabinet order govern the
planning, design and construction of buildings in Japan.
DESIGN OF REINFORCED CONCRETE BUILDINGS (1950 - 1971)
The 1950 Cabinet Order required the reinforced concrete construction as follows: (1) ends of
longitudinal reinforcing bars should be hooked for anchorage; (2) specified compressive
strength of concrete should be not less than 90 kgf/cm2; (3) a column should be reinforced by
at least four longitudinal bars which were firmly fastened by tie reinforcement at a spacing not
exceeding 30 cm and 15 times the smallest diameter of longitudinal reinforcement (Fig. 1.a);
(4) the minimum dimension of a column section should be larger than 1/15 the clear height;
the reinforcement ratio of a column should be not less than 0.8 percent; (5) beams should be
reinforced by top and bottom reinforcement; spacing of stirrups should be not more than 3/4
of the beam depth and 30 cm (Fig. 1.b); and (6) the thickness of a structural wall should be 12
cm or more; the spacing of horizontal and vertical reinforcement should be 30 cm or less; an
opening should be reinforced with bars of 12 mm diameter or larger.
REINFORCED CONCRETE BUILDING DESIGN FROM 1971 TO 1981
The 1968 Tokachi-oki Earthquake (M 7.9) caused significant damage to buildings in Aomori
prefecture and Hokkaido with a death toll of 49. The number of totally collapsed buildings
reached 673; approximately 10 percent of reinforced concrete buildings in the affected areas
suffered some kind of damage including cracking. Short reinforced concrete columns
typically in school buildings failed in shear. The damage raised some doubt about the
earthquake resistance of reinforced concrete construction although no one was killed by the
collapse of reinforced concrete buildings.
The causes of damage were summarized as (1) poor concrete and reinforcement work, (2)
uneven settlement of foundation, (3) lack of shear strength and ductility in columns, (4)
failure of corner columns under bi-directional response, and (5) torsional response of
buildings. The AIJ recommended that (1) shear stress level in columns should be kept low by
the use of structural walls and by the use of larger section, (2) monolithic non-structural wall
should be included in design structural analysis, (3) amount of shear reinforcement should be
increased and placed effectively, and (4) ends of ties and hoops should be bent more than 135
degrees, or welded closed-shape hoops and spiral reinforcement should be used. Note that the
shear resisting mechanism of a reinforced concrete member was not understood at the time.
REINFORCED CONCRETE BUILDING DESIGN (1981 TO PRESENT)
The Ministry of Construction organized an integrated technical development project
(1972-1977), entitled "Development of New Earthquake Resistant Design." The 1978
Miyagi-ken Oki Earthquake caused damage to buildings with flexible first-story or with a
large eccentricity between the centers of mass and stiffness. Therefore, the Cabinet Order was
revised to the present form in July 1980 following the recommendations of the development
project and was enforced from June 1981. The allowable stress design procedure was
maintained. Major points of revision were listed below:
(1) Shear reinforcement ratio must be 0.2 percent or more in a reinforced concrete member,
(2) Design and construction of a building is made possible up to 60 m in height; the design
and construction of buildings taller than 60 m must be approved by the Minister of
Construction,
(3) Additional requirements were introduced in structural calculation; (a) story drift, rigidity
factor and eccentricity factor under design earthquake forces, (b) examination of story shear
resisting capacity at the formation of a collapse mechanism under lateral forces, © alternative
simple procedures for buildings with abundant lateral shear resisting capacity,
(4) Design earthquake forces were specified (a) by story shear rather than horizontal floor
forces, (b) as a function of fundamental period of the structure, © at two levels (allowable
stress design and examination of story shear resisting capacity), and (d) also for the
underground structures,
BUILDING DAMAGE FROM KOBE EARTHQUAKE
The 1995 Hyogo-ken Nanbu Earthquake, commonly known as Kobe Earthquake Disaster,
occurred at around 5:46 am on January 17, 1995. The magnitude of the earthquake was
intermediate and 7.2 defined by Japan Meteorological Agency. The earthquake hit a
populated area of Kobe City, killing more than 6,300 (including those killed indirectly after
the earthquake), injuring more than 40 thousands people, collapsing approximately 92,800
buildings and houses, and damaging approximately 192,700 buildings. Approximately 80
percent of the death were caused by the collapse of houses and buildings. The total loss was
estimated to be more than 9,914 billion yen. The property losses in buildings amounted to
58.5 % of the total loss.
The damage to reinforced concrete buildings may be characterized by (1) collapse in a middle
story in office buildings, (2) collapse in the first story in apartment and condominium
buildings, (3) significant loss incurred by the damage of non-structural members, (4) fracture
at the splice of longitudinal reinforcement by gas-pressured welding technique, (5) damage in
lightly reinforced beam-to-column connections, and (6) failure of foundation and piles.
CONCLUSIONS
The technical development of earthquake resistant-building construction reduced significantly
vulnerability of new construction. Although majority of existing buildings may achieve the
purpose of structural design, some of the buildings constructed prior to the development need
careful attention and may require retrofitting work.
The structural damage can be significantly reduced by regulating (a) the brittle modes of
member failures such as shear failure of reinforced concrete columns, (b) the discontinuity in
stiffness and strength along the height of buildings, © the eccentricity between the centers of
mass and stiffness in plan, (d) the irregular configuration of structures in plan, and controlling
the quality of construction work. The experience from the Kobe earthquake disaster indicated
the desirability of higher resistance of structures to control the damage for immediate use after
an intermediate earthquake.