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©COMPUTERS AND STRUCTURES, INC., MARCH 2015

TECHNICAL NOTE SEGMENTAL BRIDGE WIZARD

Introduction

This document describes the use of the segmental bridge wizard, including functionality, options, and terminology.

The segmental bridge wizard provides a streamlined way to define the geometry of a segmental bridge using

parameters and terminology that are familiar to bridge engineers.

The segmental bridge wizard gives the user direct control of the length, number, type, erection method, and naming

convention of segments in each span. The erection methods currently supported include the balanced cantilever

method and span-by-span.

The prestressing tendon definition for segmental bridges follows the industry standard of tendon categorization

based on their geometry and sequence of installation. Each category features a customized input form that facilitates

very fast and efficient batch mode tendon definition and provides immediate plotting of defined tendons and

segments in various nonprismatic scales for quick checking

Segmental Bridge Span Assembly

The span layout is defined in the Segmental Bridge Span Assembly form by specifying a sequence of span

discretization schemes. The naming of spans, segments, and supports can be modified by clicking the View/Rename

Segments button. The location of the bridge on the layout line is defined by specifying the station of the initial (first)

segment. If the station of the last segment is larger than the layout line end station it is necessary to first exit this

form and modify the layout line.

There are four types of span discretization schemes.

Start Abutment – this can only be defined at the start of the bridge

Balanced Cantilever

Span-by-Span

End Abutment – this can only be defined at the end of the bridge

It is possible to define a bridge span assembly without Start and/or End Abutments. Click the Span

Discretization button to add/modify/view/delete span discretizations.

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View / Rename Segments

The View/Rename Segments form controls the labels of abutments, supports, spans, and segments. Each item must

have a unique name and the prefix and suffixes must satisfy the minimum and maximum character count

requirements shown on the form. Lower and uppercase characters are treated as identical.

The Segment List table refreshes upon exiting the input fields where the labels are defined. Segment rows are color

coded based on their type (rigid, pier table, segment CIP, segment precast, closure). The color coding can be toggled

off by unchecking the Color Rows per Segment Type checkbox. The entire table can be copied to the clipboard

using the Copy Table to Clipboard button. The first column in the table indicates the row number in the Segmental

Bridge Span Assembly form and the span discretization name that controls the data in each row.

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Span Discretization

There are four types of span discretization schemes that cover various superstructure erection methods common for

segmental bridges.

Start Abutment – allows definition of segments in the upstation direction, from the start abutment

Span-by-Span – assumes support at both ends and segments are defined from the downstation support

sequentially towards the upstation support

Balanced Cantilever – assumes a single support with segments cantilevering on both sides

End Abutment – allows definition of segments in the downstation direction, from the end abutment

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The Start and End Abutment types can specify no segments. An example of the use of the Start and End

Abutment discretization types is for end spans where segments are erected on temporary falsework and later

connected to the tip of a balanced cantilever via a closure segment.

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The Span-by-Span discretization type is intended to facilitate modeling of segments erected on falsework or by

overhead gantry. The prestresing is typically applied once the entire span is assembled.

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The Balanced Cantilever discretization type is intended to facilitate modeling of segments that are cast using

traveling formwork (traveler) or precast segments lifted by hoist or overhead gantry. Typically after erection of each

segment, cantilever tendons are stressed and the traveler or lifting device is advanced to facilitate erection of the

next segment.

There are five segment types that can be assigned to each segment. The types are used in segment labeling, color

coding, and to facilitate nonlinear staged construction load case definitions.

Rigid

Pier Table

Segment CIP (cast-in-place)

Segment Precast

Closure

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Segmental Bridge Tendons

The prestressing tendons for segmental bridges can be divided into categories based on their geometry and sequence

of installation. The Define Segmental Bridge Tendons form is designed to accommodate the definition and

management of tendons using the following categories.

Cantilever

Bottom Span

Top Span

For each of those three categories, a customized segmental tendon template allows very effective tendon generation

and modification. To open the template select any of the three Tendon Categories from the drop down list and click

Define Segmental Tendon. For special tendons that cannot be defined in the segmental template, select the General

category and click the Add New Tendon button.

Any tendons defined using the segmental tendon template (segmental tendons) can be copied to the General

category where the tendon geometry and parameters can be modified using the Bridge Tendon Data form.

Segmental tendons can also be edited in the Bridge Tendon Data form. It should be noted that unless the segmental

tendon name is changed, the modifications will be lost anytime the segmental tendon template form is opened and

closed by clicking on the OK button, which will regenerate the associated segmental tendons.

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Cantilever Tendons

Cantilever tendons can be defined only for superstructures that include balanced cantilever span discretization types.

The Balanced Cantilever Pier dropdown box lists the qualifying piers. Once a balanced cantilever pier is selected the

downstation and upstation tables are populated with the relevant segments and the Partial Plan Top Slab image is

updated.

Next the duct template should be selected. To add/modify a duct/anchor template, click the button. The duct

template allows definition of maximum slope of the tendon from the centerline insertion point as it leads from the

anchor location to the final duct destination. The form also allows specification of the minimum distance from the

segment face where the tendon will run straight. If the slope and straight distance criteria cannot be met the tendon is

plotted as red and a warning is displayed.

The tendon prefix is one character that must be unique within the cantilever, bottom, and top span tendons. Lower

and uppercase characters are treated as identical. Check the Mirror @ X check box and specify an X-coordinate to

generate symmetrical tendons. The X-coordinate is measured from the centerline insertion point; for X=0 the

tendons will be mirrored about the centerline insertion point.

The tendon parameters such as tendon material, area, jacking force, etc can be modified by clicking the Add/Modify

Tendon Parameters button.

To define cantilever tendons, specify the number of tendons that are anchored at each segment face. The total

number of tendons anchored in downstation segments must equal the number of tendons anchored in upstation

segments. If the count does not match the verification displays the ≠ symbol and no tendons are plotted. By clicking

the Autocorrect button the defined anchored tendon numbers are adjusted to match the count. The number of

tendons that can be anchored at each segment face is limited by the number of anchors defined in the duct template.

To add/modify anchors click on the Tendon Duct Template button.

The tendon is always defined as anchored in the lowest available anchor number and positioned in the lowest

available duct number. The tendons that are anchored in segments closer to the pier are generated first followed by

tendons anchored in segments further away from the pier. Each tendon must cross the pier centerline. Tendons that

do not satisfy those criteria can be defined as general tendons.

There are two plots that help to visualize the tendons as they are being generated. On the left is the Partial Plan Top

Slab and on the right a rotated Partial Section Top Slab. The horizontal and vertical scales do not match and are

calculated automatically to include all defined segments, ducts and anchors. The ducts are shown in green and

anchors in blue. The plot options allow hiding or showing of the working point (WP) and mirrored tendons when

applicable. The working point is defined on the Tendon Duct Template form.

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Bottom Span Tendons

Bottom tendons can be defined in a superstructure that includes any type of spans. The span tendons are defined on a

span basis, meaning that the tendon cannot cross the centerline pier to another span. Tendons that do not satisfy

those criteria can be defined as General tendons. The Span drop down list contains the qualifying spans. Once a span

is selected the downstation and upstation drop down lists are populated with the relevant segments and the Partial

Plan Bottom Slab image is updated.

Next the duct template should be selected. To add/modify a duct/anchor template click on the button. The duct

template allows definition of the maximum slope of the tendon from the centerline insertion point as it leads from

the anchor location to the final duct destination. The form also allows specification of the minimum distance from

the segment face where the tendon will run straight. If the slope and straight distance criteria cannot be met the

tendon is plotted as red and a warning is displayed.

The tendon prefix is one character that must be unique within the cantilever, bottom, and top span tendons. Lower

and uppercase characters are treated as identical. Check the Mirror @ X check box and specify an X-coordinate to

generate symmetrical tendons. The X-coordinate is measured from the centerline insertion point. For X=0 the

tendons will be mirrored about the centerline insertion point.

The tendon parameters such as tendon material, area, jacking force, etc can be modified by clicking the Add/Modify

Tendon Parameters button.

To define bottom span tendons, select the downstation and upstation segments in which the tendon is anchored. If

the tendon is not anchored directly at the segment end specify an offset value to locate the anchor inside the

segment. The number of tendons that can be anchored at each segment is limited by the number of anchors defined

in the duct template. To add/modify anchors click on the Tendon Duct Template button.

The tendon is always defined as anchored in the lowest available anchor number and positioned in the lowest

available duct number. The tendons that are specified in the first row of the table are generated first followed by

tendons specified in the subsequent rows. Since the ducts and anchors are defined relative to the bottom left or right

corner of the box section, the generated bottom slab tendons follow the variation of the bottom slab width and of the

section depth.

When the Plot Relative to WP option is selected there are two plots that help to visualize the tendons as they are

being generated. On the left is Partial Plan Bottom Slab and on the right a rotated Partial Section Bottom Slab. The

horizontal and vertical scales do not match and are calculated automatically to include all defined segments, ducts

and anchors. The ducts are shown in green and anchors in blue. The Relative to Bottom Slab Edge and Show Entire

Bottom Slab plot options hide the rotated Partial Section Bottom Slab image and the edge(s) of the bottom slab are

shown at its true location.

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Top Span Tendons

Top tendons can be defined in a superstructure that includes any type of spans. The span tendons are defined on a

span basis, meaning that the tendon cannot cross the centerline pier to another span. Tendons that do not satisfy

those criteria can be defined as General tendons. The Span dropdown list contains the qualifying spans. Once a span

is selected, the downstation and upstation dropdown lists are populated with the relevant segments and the Partial

Plan Top Slab image is updated.

Next the duct template should be selected. To add/modify a duct/anchor template click on the button. The duct

template allows definition of the maximum slope of the tendon from the centerline insertion point as it leads from

the anchor location to the final duct destination. The form also allows specification of the minimum distance from

the segment face where the tendon will run straight. If the slope and straight distance criteria cannot be met, the

tendon is plotted as red and a warning is displayed.

The tendon prefix is one character that must be unique within the cantilever, top, and top span tendons. Lower and

uppercase characters are treated as identical. Check the Mirror @ X check box and specify an X-coordinate to

generate symmetrical tendons. The X-coordinate is measured from the centerline insertion point. For X=0 the

tendons will be mirrored about the centerline insertion point.

The tendon parameters such as tendon material, area, jacking force, etc can be modified by clicking on the

Add/Modify Tendon parameters button.

To define top span tendons, select the downstation and upstation segments in which the tendon is anchored. If the

tendon is not anchored directly at the segment end specify an offset value to locate the anchor inside the segment.

The number of tendons that can be anchored at each segment is limited by the number of anchors defined in the duct

template. To add/modify anchors click the Tendon Duct Template button.

The tendon is always defined as anchored in the lowest available anchor number and positioned in the lowest

available duct number. The tendons that are specified in the first row of the table are generated first followed by

tendons specified in the subsequent rows.

There are two plots that help to visualize the tendons as they are being generated. On the left is Partial Plan Top Slab

and on the right a rotated Partial Section Top Slab. The horizontal and vertical scales do not match and are

calculated automatically to include all defined segments, ducts, and anchors. The ducts are shown in green and

anchors in blue.

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