Previous Major Earthquake Damage and Countermeasures Calculation of Allowable Unit Stress, etc.

30 Intermediate inspection June 1998 ƒ Intermediate inspection was required to ensure thorough supervision of construction work. ƒ Others Act for Promotion of the Earthquake Proof Retrofit of Buildings was enacted in Oct. 1995 Act for Densely Inhabited Areas Improvement for Disaster Mitigation was enacted in May 1997 [Great Hanshin-Awaji Earthquake] Jan. 1995 M7.2; 6,432 deaths, 104,906 buildings totally damaged, 144,274 buildings partially damaged and 6,148 buildings totally burned down Buildings built to the former seismic standard and those poorly designed and constructed were damaged and collapsed in great number. New seismic standard July 1980 ƒ Secondary design should be introduced in seismic calculation 1 Restrictions of inter-story drift, rigidity, or eccentricity ratio 2 Introduction of ultimate lateral strength calculation ƒ Reinforcement of specification regulations 1 Increase in the amount of load-bearing walls for wooden buildings [Tokachi-oki Earthquake] May 1968 M7.9: 49 deaths, 673 buildings totally damaged and 3,004 buildings partially damaged A large number of RC buildings were damaged. [Miyagi-ken-oki Earthquake] June 1978 M7.4; 27 deaths, 651 buildings totally damaged and 5,450 buildings partially damaged Buildings with pilotis and of serious eccentricity were damaged.

1. Previous Major Earthquake Damage and Countermeasures

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2. Calculation of Allowable Unit Stress, etc.

Buildings other than specified buildings Specified buildings Higher than 31 m Height of 31 m high or less + + + + + Check of inter-story drift ensure the building’s exterior materials will not fall with any building deformation Check of allowable unit stress ensure the building will not suffer damage by regular and medium-scale earthquakes, storms, etc. Check of modulus of rigidity and eccentricity ratio make sure the structural balance of the building is appropriate Check of ultimate lateral strength make sure the building will not collapse in a major earthquake Check of bearing capacity make sure the amount of load-bearing walls or columns and bearing capacity of connections are appropriate Specified building: a building that is not: a wooden building not greater than 13 m in height and not greater than 9 m in eaves height, a steel frame building not higher than 13 m and complying with predetermined specifications, or an RC building not higher than 20 m and complying with predetermined specifications 32 Calculation of allowable unit stress Make sure that the building will not suffer damage to any part, by its own dead weight, applied loads or the force of a medium scale earthquake, etc. earthquake, storm or snowfall likely to occur about once in the life time. 1 The force that occurs to a part of a building is calculated by loads and external force. Then, the unit stress that occurs in a section of any part of the building stress per unit area is calculated. 2 Make sure that the unit stress of any given part calculated in 1 is smaller than the allowable unit stress of that part. Allowable unit stress is the limit force per unit area in the building material’s elastic domain the section which recovers to its original condition once the force is removed. 33 Elastic area Plastic area Major earthquake Japanese scale of 6 + to 7 Range of calculation of allowable unit stress Original condition will be recovered after removal of force after earthquake. No damage Allowable unit stress M axi m um f orce that the member can sustain Ordinary condition Deformation Damage deformation will remain even after removal of force. Collapse Size of force that acts Relationship between force working on a member and deformation Medium scale earthquake Japanese scale of 5 Range of calculation of ultimate lateral strength 34 Inter-story drift The level of deformation that occurs on each floor section in the lateral direction at the time of an earthquake of medium scale should be smaller than the level that causes the fall of exterior materials in principle, within 1200, and in case of no possibility of serious damage, within 1120. Modulus of rigidity Eccentricity ratio Modulus of rigidity is an index of balance of rigidity for each floor of the building. Eccentricity ratio is an index of balance of rigidity for each floor in the lateral direction. With these indexes, one can check if the balance of the building is appropriate without causing serious defects in structural strength. —Ž ‰º ” z’ u‚ Ì• ΂ è‚ Å • ÏŒ`‚ ª“ Á ’ è‚ Ì’ Œ ‚ É W ’ † s• ½ – Ê } t ‘ ¼ ‚ æ ‚ è _‚ ç‚ © ‚ ¢ Š K ‚ É ‘ ¹ ‚ ª W ’ †‚ ·‚ é Floor that is to o elastic. Fall [Top View] [Elevational View] Damage is concentrated on the most elastic floor. Deformation is concentrated on a specific column due to the eccentricity of the layout. 35 Calculation of ultimate lateral strength The building should not suffer collapse or destruction that can harm people in the building in the event of an extremely rare major earthquake. 1 Ultimate lateral strength for each floor is calculated from the strength of materials used. 2 The ultimate lateral strength necessary for each floor not to suffer collapse or destruction in the event of major seismic force is calculated. This should be calculated by considering various parameters, such as tenacity and shape characteristics eccentricity ratio and modulus of rigidity of each floor. 3 1 should be larger than 2. 36

3. Calculation of Ultimate Bearing Capacity