6~tzk6&0fe · earthquake shear and moment. then, use these calculated* values as static loads...
TRANSCRIPT
JcAR^HOUAKE ENGINEERING SEMILAR 1
MARCH 1 3 , 1979
TO G. PEERY
Meier4 M illirneie? Wa\/6~TZk6&0fe
M&rm *//7FROM L • J . KING
SUBJECT: EARTHQUAKE ENGINEERING SEMINAR IN HOUSTON
THE SEMINARS ARE SPONSORED BY EERI (EARTHQUAKE ENGINEERING RESEARCH I N S T IT U T E ) . THE PURPOSE OF THE SEMINARS IS TO DISSEMINATE FUNDAMENTAL YET STATE-OF-ART INFORMATION ON IMPORTANT TOPICS IN EARTHQUAKE ENGINEERING. THE TOPICS INCLUDE AN OVERVIEW OF GEOLOGICAL, SEISMOLOGICAL, AND STRUCTURAL ASPECTS. THE STRUCTURAL PORTION COVERS THE STRUCTURAL DESIGN AND ANALYSIS, SOIL-STRUCTURE INERACTION, ETC.
IT WAS A VERY INTENSIVE THREE DAY SCHEDULE AND WORTHWHILE TO BE THERE. SUMMARIZED BELOW ARE MY INTERPRETATION OF THE UP-TO-DATE PRECEDURES FOR EARTHQUAKE DESIGN OF THE CONVENTION BUILDING AND THE SPECIAL PURPOSE STRUCTURES.
( I ) FOR THE CONVENTIONAL B U IL D IN G , CNE MAY CHOOSE FROM ABUILDING CODE, SUCH AS UBC, THE FORMULAS FOR CALCULATING EARTHQUAKE SHEAR AND MOMENT. THEN, USE THESE CALCULATED* VALUES AS STATIC LOADS IN THE DESIGN. THE SHEAR FORMULA IS AS FOLLOWS,
I = IMPORTANCE ( FRCM 1 . 0 GENERAL TO 1 . 5 ESSENTIAL F A C I L IT Y )
K = TYPF OF STRUCTURE (FROM .6 7 FOR DUCTILE FRAME TO 2 . 5 ELEVATED TANK)
C = DYNAMICS OF STRUCTUR (BASED ON STRUC. FOUNDAMENTAL PERIOD)
S = S IT E-STRUCTURE RESONANCE
V = Z I K C S W
WHERE Z = SEISMIC ZONE (HAWAII IS IN ZONE FOR 3)
W = WEIGHT OF STRUCTURE
EARJHQUAKE ENGINEERING SEMILAR 2
HOWEVER, CALCULATIONS BASED ON CODE TENDS TO TREAT ALL STRUCTURE A L IK E , AND USUALLY GIVE LESS (YES ) CONSERVATIVE VALUES COMPARED WITH MORE ELABORATED ANALYSES* ATC (ADVANCED TECHNOLOGY COUNCIL) OF SEAOC CONTRACTED WITH NBS AND NSF IS PREPARING A NEW GUIDELINE FOR EARTHQUAKE DESIGN. ATC, PROVIDED MORE CONTROLS FOR THE DESIGNERS IN DETERMINING THE DYNAMIC LOADS ON THE STRUCTURES/BUILDINGS, IS UNDERGOING TESTING AND REVIEW BY AUTHORITIES ACROSS THE NATION, IF APPROVED,WILL BE ADOPTED AS A CODE.
( I I ) FOR SPECIAL PURPOSE STRUCTURE SUCH AS THE 25M ASTROCOME- TELESCOPE STRUCTURE, THE PROCEDURES FOR EARTHQUAKE DESIGN SHOULD BE:
( 1 ) CHOOSE PROPER EARTHQUAKE FCRCESTHE FORCES MAY BY CHOSEN FROM A PREVIOUS EARTHQUAKE,A LONGER EXCITATION (EL CENTRO TYPE, FIGURE 1) OR A SHORTER EXCITATION (HELENA, MO. TYPE, FIGURE 2 ) , OR A COMPUTER SIMULATE EARTHQUAKE (FIGURE 3 ) .
( 2 ) CONSTRUCT THE SHOCK SPECTRAL CURVES SUCH AS THAT SHOWN IN FIGURE 4 .
( 3 ) DESIGN THE STRUCTURE.
( 4 ) MODEL THE STRUCTURE TO OBTAIN FIRST FEW LOWEST NATURAL FREQUENCIES BY EIGENVALUE EXTRACTION METHOD.
( 5 ) ESTIMATE MAXIMUM FORCE OR UPPER BOND BASED ON SHOCK SPECTRAL CURVES, USE EITHER
FMAX = RSS OF THE INDUCED FORCES BASED ON THE FIRST FEW FREQUENCES OF THE STRUCTURE.
ORFMAX = ALGEBRA SUM OF THE INDUCED FORCES BASED
ON THE FIRST FEW FREQUENCES OF THE STRUCTURE.
( 6 ) REPEAT STEPS 3 THRU 5 UNTIL STRUCTURE IS SAVE.
( 7 ) F INAL CHECK ANALYSIS
THE CORRECT FMAX = SUM OF THE PRODUCT OF FORCES ATEACH FREQUENCY AND ITS P A R T IC I PATING FACTOR,
THE PARTICIPATION FACTORS CAN ONLY BE OBTAINED THRU LENGTHY DYNAMIC ANALYSIS. THIS STEP IS OBVIOUSLY MOST COSTLY AND TIME CONSUMING.
£ a r j h q u a k e e n g i n e e r i n g s e m i l a r 3
CONCLUSION:
THE MATHEMATIC OF DESIGNING A SAFE EARTHQUAKE RESISTING STRUCTURE IS MERELY AN APPLICATION OF THE STRUCTURAL DYNAMICS WHICH IS WELL DEVELOPED. THE DE F IN IT IO N OF SAFE IS A FUNCTION OF THE CLASS OF STRUC. WHICH BELONGS, AND THE ECONOMICS. THUS, AN ECONOMICALLY DESIGNED SAFE WAREHOUSE IS A LOT RISKIER THAN A SAFE HOSPITAL. THE EARTHQUAKE LOADINGS ARE THEREFORE BASED ON THE LOCATION OF THE STRUCTURE AS WELL AS THE STR. CLASS AND ITS COST.
25M ASTRODOME-TELE SCOPE IS DESIGNED TO SURVIVE AT A 200 KM/HR STATIC WIND. WE SHALL LIKEWISE CHOOSE/DECIDE AN ACCEPTABLE EARTHQUATE SPECTRUM FORCES. THEN ANALYZE ACCORDING TO THE RECOMMENDED PROCEDURES OUTLINED ABOVE. THE OUTCOME MAY BE
( 1 ) MAX STRESS DUE TO EARTHQUAKE FORCES IS LOW, AND WIND FORCF S GOVERNS THE DESIGN.
(2 ) STRESSES TCO HIGH(A) REDESIGN AND/OR BEEFUP STRUCTURE IF COST
INCREASE IS TOLERABLE, OR(B) INCREASE THE RISKS BY REDUCING THE EARTH
QUAKE FORCES IF LOCAL BUILDING CODE ALLOWS.
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IMPERIAL VALLEY EARTHQUAKE MAY 18,1940 EL CENTRO COMPONENT SOOE
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DAMPING: 0,2,5,10 AND 20% OF CRITICAL400
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PERIOD (SEC.)
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