ppt07 clarifications

8/17/2019 Ppt07 Clarifications

http://slidepdf.com/reader/full/ppt07-clarifications 1/35

Abdelghani Meslem & Dominik LangDepartment of Earthquakes and the Environment

NORSAR, Kjeller, Norway

Seismic Vulnerability AssessmentPPT07

Clarifications

http://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=RYy_zyAnKrrx3M&tbnid=6ro4JD6h68IG_M:&ved=0CAUQjRw&url=http://ablab.in/our-clients/&ei=gUQMU6bML4WzywPV1YDAAw&bvm=bv.61725948,d.bGQ&psig=AFQjCNE9PXe7kY6izxtwgoZbBgEZms7IRw&ust=1393399266892324



Content

o Set Mass Source for Modal Analysis

o How to determine if higher modes are significant

o Gound motion selection and scaling for for nonlinear time history

o Second-order effects (P-Delta effects)

A. Meslem & D. Lang © NORSAR – Kjeller (Norway) 2014




Define

Mass Source...

From Element and Additional Masses and Loads

G + 0.3 ∙ Q G = 1

Q = 0.3

Set Mass Source for Modal Analysis




in new version of SAP2000 in old version of SAP2000

Set Mass Source for Modal Analysis




Nonlinear static analysis: Criteria

shall be permitted for structures in which higher mode effects are not

significant.

To determine if higher modes are significant:

• Step 1: Perform modal analysis to identify number of modes required to

obtain 90% mass participation;

• Step 2: a modal response spectrum analysis shall be performed for thestructure using sufficient modes to capture 90% mass participation;

• Step 3: a second modal response spectrum analysis shall also be

performed, considering only the first mode participation;

• Higher mode effects shall be considered significant if the shear in any

story resulting from the modal analysis considering modes required to

obtain 90% mass participation exceeds 130% of the corresponding story

shear considering only the first mode response.





Step 1: Modal analysis

select the number of

modes to be considered


http://slidepdf.com/reader/full/ppt07-clarifications 7/35A. Meslem & D. Lang © NORSAR – Kjeller (Norway) 2014



first torsional

mode is 3rd

Σ = 0,90 0,98

n

j

i j j

n

ji j j

i

m

m

1

2

,

1,

Modal participation factor of mode k:




4 modes to be

considered





Design spectral accelerations Sa(T i )/g for each mode i :

Mode shape i: 1 2

3 n,1

j+1,1

j,1

n,2

j+1,2

j,2

n,3

j+1,3

j,3

Period T [sec]

S p e c t r a l a c c e l e r a

t i o n S a

T 2T 1 T 3

Sa,d (T 1 )

Sa,d (T 2 )

Sa.d (T 3 )

tep 2: a modal response spectrum analysis shall be performed for the structure

using sufficient modes to capture 90% mass participation




)T(SmF id,aii, j ji, j

F n,1

F j+1,1

F j,1

F n,2

F j+1,2

F j,2

F n,3

F j+1,3

F j,3

Mode shape i: 1 2

3 n,1

j+1,1

j,1

n,2

j+1,2

j,2

n,3

j+1,3

j,3

resulting shear forces F b,m : 2

i,m,b

n

1im,b FF

EN 1998-1:2004, 4.3.3.3








F 1,1

= 100 0.30 1.426 0.846 = 36.2 kN

F 2,1

= 75 0.644 1.426 0.846 = 58.3 kN

F 3,1

= 50 1.00 1.426 0.846 = 60.3 kN

F 1,2

= 100 ( –0.676) ( –0.511) 1.813 = 62.6 kN

F 2,2

= 75 ( –0.601) ( –0.511) 1.813 = 41.8 kN

F 3,2

= 50 1.00 ( –0.511) 1.813 = –46.3 kN

F 1,3 = 100 2.47 0.090 2.115 = 47.0 kN

F 2,3

= 75 ( –2.57) 0.090 2.115 = –36.7 kN

F 3,3

= 50 1.00 0.090 2.115 = 9.5 kN

)T(SmF id,aii, j ji, j F 3,1= 60.3

F 2,1 = 58.3

F 1,1 = 36.2

F 3,2 = –46.3

F 2,2 = 41.8

F 1,2 = 62.6

F 3,3 = 9.5

F 2,3 = –36.7

F 1,3 = 47.0






A number of ways to combine modes given direction including CQC, SRSS,..and others...

Response spectrum will be applied as an acceleration in U1 (UX) direction using the

previously defined curve EC-8-B






li i l i i i




1 mode to be

considered

Step 3: a second modal response spectrum analysis shall also be performed,

considering only the first mode participation

li i l i C i i




If higher mode effects are significant, the nonlinear static method shall

be permitted if a linear dynamic analysis is also performed tosupplement the NSP (i.e. to verify the adequacy of the design).

RegularityAllowed simplification in model

Plan Elevation

● ● Planar (2D)● ○

○ ● Spatial (3D)

○ ○

Regularity vs. allowed simplification model in nonlinear static analysis

EN 1998-1:2004, 4.3.3.4.2

N li i hi l i




Nonlinear time history analysis

This approach is the most rigorous, and is required by some building

codes for buildings of unusual configuration or of special importance .

N li ti hi t l i





the calculated response can be very sensitive to the characteristics of

the individual ground motion used as seismic input; therefore, severalanalyses are required using different ground motion records to achieve

a reliable estimation of the probabilistic distribution of structural

response.

Since the properties of the seismic response depend on the intensity,or severity, of the seismic shaking, a comprehensive assessment calls

for numerous nonlinear dynamic analyses at various levels of intensity

to represent different possible earthquake scenarios.

N li ti hi t l i




• Accelerograms to be used in non-linear time history analysis shallbe selected according to EN 1998-1, 3.2.3.1 ( Session III)

Determination of Response Parameters:

N - number of accelerograms used in non-linear time history analysis

N ≥ 7 Response Computation

yes no

● ○ Use average of the response quantities

○ ● Use the most unfavorable value of the

response quantity amongst all motions

EN 1998-1:2004, 4.3.3.4.3


Ground motion selection and scaling



N li ti hi t l i






The parameters (that have the most influence on ground motion spectral shape)that need to be considered in selecting records :

• Magnitude range of anticipated significant event;

• Distance range of the site from the causative fault;

• Site Condition (i.e. looking at the average shear velocity);

• Basin effect (if basin exists)

N li ti hi t l i






Select pairs of ground motion records to perform dynamic response history analysis.

The use of 11 pairs of motions (i.e. 22 motions set) is recommended;

For each ground motion pair, run analysis: the amplitude should be incremented, and

nonlinear response history analysis performed until the occurrence

N li ti hi t l i






Step 1: Run nonlinear static analysis (pushover) and identify the different damagestates.

S l i g h t D a m a g e

M o d e r a t e D

a m a g e

E x t e n s i v e D a m a g e

C o m p l e t e D a m a g e







Step 2: For each selected ground motion, run nonlinear time history analysis

Use scaling to increase the IM level of the ground motion records, until all the limit

states are reached as defined above. Details on scaling procedures that the analyst

may implement are beyond the scope of these guidelines. Reference on this matter

can be made to ATC-58 (FEMA P-58, 2012)

1, 1.5, 2, ….3.1, 3.2, 3.3, …4, 4.5, 5.0….6.1, 6.2, 6.3, ….7, 7.5, 8, …….9.1, 9.2, 9.3, …..10, 10.5, 11.0…….12.1, 12.2, 12.3

Slight

Damage

Moderate

Damage

Extensive

DamageComplete

Damage







Use scaling to increase the IMlevel of the ground motion

records







Mean Curve

Second order Effects (P Δ effects)




Structures in real life are flexible and can exhibit largelateral displacements in unusual circumstances. The lateral

displacements can be caused by wind or seismically

induced inertial forces.

Gravity loading will influence structural response undersignificant lateral displacement.

P-Δ may contribute to loss of lateral resistance, ratcheting

of residual deformations, and dynamic instability.

Second-order Effects (P- Δ effects)





Second-order effects (P-∆ effects) need not be taken into account if the following

condition is fulfilled in all storeys:

EN 1998-1:2004, 4.4.2.2

10,0

hV

d P

tot

r tot

h

V

d

P

tot

r

tot

= is the interstorey drift sensitivity coefficient;

= is the total gravity load at and above the storey considered in the seismic design

situation;

= is the design interstorey drift, evaluated as the difference of the average lateral

displacements ds at the top and bottom of the storey under consideration and

calculated in accordance with Chapter 4.3.4;

= is the total seismic storey shear; and

= is the interstorey height.






If 0,1 < θ≤0,2, the second-order effects may approximately be taken into account bymultiplying the relevant seismic action effects by a factor equal to 1/(1 - θ).

value of the coefficient θ shall not exceed 0,3






Use P-Delta in SAP2000




Contact details

Abdelghani Meslem, Dominik Lang

Department of Earthquakes and the Environment

NORSAR, 2027 Kjeller, Norway

Phone: (+47) 974 10 740 (Dr. Meslem)

(+47) 988 42 924 (Dr. Lang)

E-mail: [email protected]

[email protected]

Web: http://www.norsar.no

ppt07 clarifications

Documents