H1c. Second Presentation 1per Page

8/11/2019 H1c. Second Presentation 1per Page

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Loads on structures:

- -. .- Dynamic (e.g. earthquake)

- Linear (constant stiffness)- Nonlinear (variable stiffness)

Structural Analysis Approaches:-(least accurate; least complex)

-- Nonlinear static (pushover)- Nonlinear d namic time histor

(most accurate; most complex)


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Pushover analysis: pp y ng a orce str ut onorce str ut on to t e structure n an

incremental fashion while monitoring theu vv

base shear (V b) versus control nodecontrol node displacement N .

compromise the simplicity of linear static approachesu y y .


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1- Nonlinearity sources:

- -(consider or not: codes)

-(too many materials behavior models)

2- Nonlinearity modeling:

- Concentrated - Distributed


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Plastic hinge properties:

- -


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Plastic hinge properties:- using codes tabulated properties


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-- a single concentrated force at the top

-

- in ro ortion to the standard code rocedure:

/ x x x x xF w h w h V - in proportion to the product of story masses and

predominant mode shape of the elastic model of thestructure

/ x x x x xF w w V


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4- Control node:- For common buildings, the control node could beselected as roof (top) story node

- Pushover analysis is stopped when the structure reaches:re-defined dis lacement

or

ultimate capacity

-application of lateral loads


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-The global response of the structure and individual

light of the specific performance goals of the system


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Using SAP2000 for Pushover Analysis

We will use the same frame (elastic beams), justmodify dead loads:


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1- Run Modal Analysis

1 . 0 .

0 . 3 4 5

Select lateral load pattern:

1 0 0 0

3 4 5 x


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2- Lateral Load Case


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3- Define Push Load Case

1 2


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4- Assign Plastic Hinges


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4- Assign Plastic Hinges


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5- Run


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6- Results OutputDisplay displacement:


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7- Checking Hinges Status

At 0.5 ft roof dis lacement: the erformance levelof the system is Collapse Prevention (CP)

H1c. Second Presentation 1per Page

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