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.

? i s

■F-tCi i

tm iBXM U »T HELENA, MONTANA. OCTO.nl J |. | | ] | . COHrONtm H-I

jZ i Cl 2.

■F tC7 3

VELO

CITY

Su

(IN

./SE

C.)

F'V *

IMPERIAL VALLEY EARTHQUAKE MAY 18,1940 EL CENTRO COMPONENT SOOE

400

200

100

30

60

^0

20

109 .

4

2

i.9

2

DAMPING: 0,2,5,10 AND 20% OF CRITICAL400

200

.04 .06 .08 •2 .4 .6 .9 i 2 4 6 9 10 20

PERIOD (SEC.)

1 Ci 4—