Example2 Two Equal Spans Option3 Final

7/29/2019 Example2 Two Equal Spans Option3 Final

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10/26/2011 Example2-Two-Equal-Spans-Option3-Final.ppt 1

Example 2 Option 3:

Bent columns on capped piles - an alternate way to

connect the columns to the pile caps

Details on following slides

Piles: 14" concrete-filled steel pipeAbutment

Abutment

Bent cap

Pile cap

Slide 1 - no change


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4.0'

20.0'

8" slab deck

Ground level

4"

railing

6.25'

47.0'

8.25'

24.0'

4.0'

Assumed point of pile fixity

(idealized cantilever pile)

Top of column at mid-

height of bent cap

Top of piles at mid-

height of pile cap14.75' 12.75'

32.25'

BT-63 girder

30.25'

Slide 2 - no change


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Pile cap: 13' x 13' x 4'

14" concrete-filledsteel pipe

2.0'

2.0'

4.5'

4.5'

13.0'

6.5'

Slide 3

Stop column at top of pile cap

and insert aJ oint Constraint

between the joint at the columnbase and the center joint at the

mid-depth of the pile cap

4.0'

5.0' 8.5'

2.0'

12.75'

13.0'

Assumed point of pile fixity

30"

Bent cap

Base of

column

Joint at base

of column

Center joint at

mid-depth of cap

J ointconstraint


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Slide 4

Shows theJ oint Constraint that "connects"the joint in the column base and the center

joint at the mid-depth of the pile cap

X

ZX = 80.0'

Z = -6.083'Z = -6.25'

Z = -6.083'

Z = -32.25'

Z = -47.0'

Z = 0

Z = -6.25Z = -8.25'

22.0'

14.75'

X=75.5

'

X=73.5

'

X=84.5

'

X=86.5

'

Roller bearing

(X = 0, X = 160')

Pinned bearing

Abutment Bent column

Z = -30.25'

J oint Constraint

2.0'Base of

column


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Views toward X = 0

Y

Z

Y=0

Y=-2.0

Y=-4.0

Y=-8.5

Y=-13.0

Y=-15.0

Y=2.0

Y=4.0

Y=8.5

Y=13.0

Units: feet

2.0'

4.0'

8.5'

13.0'

15.0'

Y=

0

Slide 4

Shows theJ oint Constraint that "connects"the joint in the column base and the center

joint at the mid-depth of the pile cap


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XZ

Y

next 2 slides

Y

=

-8.5

'


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View in +X direction

nodes

overlapping nodes

bent cap

pile

column

Z

column ( frame section )

bent cap ( frame section )

pile cap ( made up ofthick-

plate finite elements )

pile ( frame section )

top of deckY

Z = - 32.25'

Z = - 8.25'

Z = 0

Z = - 30.25'

base of columnJ oint Constraint


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nodes

overlapping nodes

column

pile

mid-depth of pile cap in

a plane at Z = - 32.25'

top of column at mid-depth of bent cap at

X = 80.0', Y = - 8.5', Z = - 8.25'

bottoms of all piles at depth Z = - 47.0'

X

Z

Y

top of pile cap in a

plane at Z = - 30.25'

tops of piles in a plane at

cap mid-depth Z = - 32.25'

J oint Constraint


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J oint Constraints - introduction

When a member is drawn the program creates joints at the ends of the member. For

example, joints 1 and 2 shown below are created when a member is drawn from a

"starting" point ( insert 1 ) to an "ending" point ( 2 ). Joints just created are connected

by the member, and are the points at which the member is "connected" into the model:

If a new second member is drawn parallel to ( but at a distance from ) the first member,

new joints ( 3 and 4 ) are created. In this case, the joints in Member 1 ( 1 and 2 ) and inMember 2 ( 3 and 4 ) are not connected in any manner, and would not "work together" inthe model unless connected by another component, or by aJ oint Constraint.

ending pointstarting point

1 2

Member

1 2

3 4

Member 1

Member 2


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AJ oint Constraint is a "conceptual device" that can used to rigidly connect two or morejoints that are not connected by a component drawn between them. For example, joints

2 and 4 can be constrained ( i.e., forced ) to work together in the model:

1 2

3 4

Member 1

Member 2

constraint

Two joints that are rigidly constrained will "move together" ( i.e., they cannot displacerelative to each other ) as the structure deforms. Like Mary and her Little Lambs, wherever

one joint goes the other must exactly follow.

There are several types of constraints available in CSI Bridge. They can be seen by:

Orb Resources Help(show) Index

key wordConstraint Define J oint Constraints

The constraint type that will be used in this example is a Body Constraint


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A Body Constraint is a type ofJ oint Constraint that "connects" two separate bodies(each with its own joint numbers) by linking one joint in each body. The connecting link

between the two bodies is a rigid link between the selected joints. The connected joints

act as a three-dimensional rigid body so that they cannot displace relative to each other.

The connected joints may be at any positions in space. That is, if two bodies are to be

connected by "constraining" one joint in each body, the selected in each body do not have

to coincide ( do not have to lie on top of each other ).

Body Constraint

Example:

Superstructure and bent drawn

using Bridge Wizard

Pile cap and piles drawn by

user outside ofBridge Wizard

Note that each "body"

has its own joint

numbering system.

Updating the bridgemodel will not link the

two bodies becausethere are no coincident

joints.


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10/26/2011 Example2-Two-Equal-Spans-Option3-Final.ppt12

Body Constraint ( continued )

The left column can be connected to the left cap/pile foundation by using the BodyConstraint type ofJ oint Constraint to link Node 90 in the column with Node 46 in the

foundation ( similar for the right column and foundation, using another Joint Constraint ).The Joint Constraint acts like a "link" between the two Nodes:

J oint Constraint

"Link"

Multiple constraints can be used between multiple "bodies" within the structure. When

the model is Updated, the program will use all constraints to merge the coordinates inall the separate bodies to form a single bridge model.


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10/26/2011 Example2-Two-Equal-Spans-Option3-Final.ppt13

Multiple constraints can be used between multiple "bodies" within the structure. When

the model is Updated, the program will use all constraints to merge the coordinates in

all the separate bodies to form a single bridge model. Thus:


Body Constraint 1 Body Constraint 2

Body 1

Body 2 Body 3

Update uses two constraints to mergethree bodies into one bridge model


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Note that the program does NOT actually draw the links between the constrained joints.

The user can only see at any given time a single constraint, and the joints that are linked

by that constraint. However, it is convenient to visualize a linkage between constrainedjoints. ForBody Constraint 1 :

Visualized link:

Body Constraint 1Body Constraint 1

as displayed by program


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Welds

A Weld is another form ofJ oint Constraint. It can be used to "connect the different partsof the structural model that where defined using separate meshes" . It is not a single

constraint, but rather is a set of constraint linking multiple pairs of joints. A Weld is used toconnect several joints along the boundary between two separate body meshes:

Figure 12, CSI Analysis Reference Manual

A single Weld can beused to link Joint 121 to 221, Joint 122 to 222, etc. Welds are

not used in this example.


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Coincident node:

top of pile, mid-depth

of cap, base of columnJoint Constraint type:

Body Constraint

How to go from Example 2 Option 2 to Option 3 ?


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Overview

Start with the bridge model from Exercise 2 Option 2

Home YZ plane view X = 80

Extrude on

pile cap

Column

length:

24.0

'

Extrude off

Z = - 32.25

column


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remove

24.0'

columns

Z = - 32.25

24.0'

columns

Starting point from

previous slide

Existing 24.0' columns must be deleted before

Bent_free_base can be redefined with 22.0' columns( column base springs are not changed )


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24.0'

columns

removed

Z = - 32.25Z = - 30.25

add

22.0'

columns

Redefine Bent_free_base to have 22.0' columns


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add two

Body

ConstraintsBODY1 BODY2Z = - 30.25

Z = - 32.25

Use Body Constraints BODY1

and BODY2 to link segments

Link segments ( constrain joints ) and Update bridge model

Update bridge model

BODY1 BODY2


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View joints linked using

Body Constraint BODY1View joints linked using

Body Constraint BODY2


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Open file CSI Bridge file

Example2-Two-Equal-Span-Option3.bdbsaved at the end of Option 2


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In YZ plane @ X = 80, mark the bent column segments and nodes to be deleted.

Left-click mouse and

drag from right to left

to make selection.

Selection box must

include ortouch two

nodes and three column

segments in each of

the bent columns

End

selection Selection box

Start

selection

Three column

segments and

two nodes per

bent column

Don't delete

these joints


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Delete

Column segments and

nodes selected for deletion

Selected column segments

and nodes are now deleted


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Open Components tab to access Bent_free_base to change column lengths


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No change


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In Bridge tab UpdateBridge Model to add re-defined Bent_free_base

2-ft gap

22-ft

column


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Use Display Options to turn on Joint Labels


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Right-click anywhere

in view pane

Increase font sizes ( also increases size of boundary condition symbols )


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Define two Body Constraints, one for each column-foundation connection

BODY1 BODY2

Y

ZView toward X = 0

Pile cap

Z = - 30.25

Z = - 32.25

Node numbers after model

Update that redefined thebent column lengths

Body Constraint-typeJoint

Constraints:

BODY1 links Nodes 46 and 90

BODY2 links Nodes 43 and 87


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Use Home Display Options to turn offJoint Labels.

Then use Advanced tab to create joint constraints BODY1 and BODY2

Constraints created by program

during model construction


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Y

ZView toward X = 0

BODY1 BODY2

Assign each pair of joints to the specified Joint Constraints


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Before going farther, make a change in the color that is used to display the joints assigned

to all internal constraints ( joint links ) and external restraints ( reactions )


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ALL constraints and restraints will be changed to RED

which is easier to see than the default gray


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Open Advanced tab, and select Nodes to be constrained by BODY1

Start

selection

End

selection

Note that reaction symbol

has changed to RED

Selection

box

Use mouse to select the two nodes by

enclosing them in a selection box.

This selection can be made either

Left-to-Right or Right-to-Left


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Assign BODY1 constraint to the selected joints

Select

constraint

BODY1and thenOK

Selected

joints


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Selected joints now constrained by BODY1

Joints constrained by BODY1 change to RED.This is not permanent. Color will revert to

BLACK when any other constraints are shown.

Note that there is no "linkage symbol" drawn

between these joints.

This is the only place where the

constraint name appears


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In current view, select Nodes to be constrained by BODY2

Selection

box


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Assign BODY2 constraint to the selected joints

Selected

joints Select

constraint

BODY2and then

OK


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Selected joints now constrained by BODY2

Joints constrained by BODY2 change to RED.As noted before, there is no "linkage symbol"

drawn between these joints.

Note that only ONE joint constraint can be shown

at a time. Thus, the joints constrained by BODY1

and those constrained by BODY2 cannot be seenat the same time.

This is the only place where the

constraint name appears


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UpdateBridge Model to link foundations to rest of structure.The Bridge Model is now complete.


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How to view Joint Constraint assignments( Assume that Joint Labels are initially turned off )

Example situation:

When an existing file is opened no Joint Constraints

are shown.

Recall that CSI Bridge does NOT show constraint

"linkages" as components. There is no way to "turn on"

a display ofJoint Constraints to show them as linkages

between joints.

For example, the figure at left has two separate Joint

Constraints, but they are not shown.The following steps will allow the user to select and view

these constraints. The user must know that they exist, and

the names of any constraints to be seen.


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To select and view Joint Constraint BODY1 that links Nodes 46 and 90

Use Home Display Options to turn on Joint Labels. This not

required, but it helps see which joints are constrained ( linked )

Opens Show Joint

Assignments window

( next slide )

Display Options


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Select Constraint to be displayed

The constrained joints are shown in the color ( here, red ) that was earlier selected

forConstraints. The name of the Joint Constraint is given as shown below

Joints linked by BODY1( appear as colored joints )


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Repeat to select and view Joint Constraint BODY2 that links Nodes 43 and 87

Joints linked

by BODY2


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The constrained joints are shown in the color ( here, red ) that was earlier selected

forConstraints. The name of the Joint Constraint is given as shown below

Joints linked by BODY2

( appear as colored joints )


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Use Advanced More to clearConstraint display and return to "normal" view


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"Normal" YZ plane view restored

Note that there is no indication that

these joints ( or any other joints )

are linked by a Joint Constraint


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In Home tab, use Display Options to turn off joint labels and then select 3DXZ view

Display options


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In the Analysis tab run an analysis for the DEAD loads


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Deflection reference line

Deflection at bent due to elastic shortening

of the bent columns and the piles

Base of column and tops of piles

deflect vertically by the same amount

Joint Constraint ( not shown by the program )

Deflected profile displayed when Analysis is completed

Recall that the model is Locked. In order to make any changes in the model it

must be Unlocked, which will erase the results of the analysis


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Selected vertical deflections

U3 = -0.2942 in

U3 = -0.461 in

X (U1)

Z (U3)

Set units to inches

Move cursor to joint


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Return to Perspective view and turn offJoint Labels

Make joints Invisiblein Display Options


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Longitudinal ( M3 ) moment diagram

X

Z

Y

1

2

3

Structure ("global")

coordinate system

Member coordinate

system for member

laid out from X = 0

to X at end of bridge

3103 ft-k

4923 ft-k


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Compare DEAD load moment diagrams for two column base connections

Option 2

Bent columns on pile foundations

( column extended to mid-depthof pile cap )

Option 3

Bent columns on pile foundations

( column base is at top of pile cap connected to cap by Joint Constraint )

4923 ft-k

3103 ft-k

Close enough for government work

3107 ft-k

4913 ft-k


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Vertical reactions at tips of piles

If necessary, use Display Options

to turn offRestraints symbols


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Isolated view of pile footing reactions in Y region

52.28

54.89

52.28

65.59

54.83

54.83

52.16

54.77

52.16

Vertical reactions

Reaction sum = 493.8 kips


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Show member axial force diagrams


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Compression forces in piles and in bent column where it

connects to the Joint Constraint at the base of the column

Rubberband zoom

R = 52.28 kips

( Slide 58 )

Force at base of column = -371.1 kips


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Check pile footing vertical equilibrium

Total pile weight = 22.8 kips

Pile cap weight = 101.4 kips

495.3 kips downward

Close enough !!

(computed in Option 2)

(computed in Option 2)

52.28

54.89

52.28

65.59

54.83

54.83

52.16

54.77

52.16

Column force at Joint Constraint = 371.1 kips

Total reaction = 493.8 kips upward


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10/26/2011 E l 2 T E l S O i 3 Fi l

10/26/2011:

Updated from 10/22/2011: Page 4 corrected ( 22.0' vs 24.0' dimension )

No other changes

Example2 Two Equal Spans Option3 Final

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