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 Discretization button to add/modify/view/delete span discretizations. Span Page 1 of 13
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. Page 2 of 13
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 Page 3 of 13
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. Page 4 of 13
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. Page 5 of 13
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 Page 6 of 13
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. Page 7 of 13
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. Page 8 of 13
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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. Page 10 of 13
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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. Page 12 of 13
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