design and rating of steel bridges - squarespacebridge+steel_2015.pdf · ... of the aashto lrfd...

4/21/2015

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© 2014 Bentley Systems, Incorporated

Steve Willoughby

Parametric and Integrated Bridge DesignLEAP Bridge Steel

2 | WWW.BENTLEY.COM | © 2014 Bentley Systems, Incorporated

Design and Rating of Steel Bridges

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3 | WWW.BENTLEY.COM | © 2014 Bentley Systems, Incorporated3 | WWW.BENTLEY.COM | © 2014 Bentley Systems, Incorporated

Discussion Topics

• LEAP Bridge Steel Overview

• 3D Modeling Workflow

• General commands

• Roadway Commands and Civil data import

• Superstructure Modeling

• Substructure Modeling

• Analysis

• Design

• Substructure Analysis/design using RC-PIER

• Load Rating

• Export to MicroStation


LEAP Bridge Steel Overview

• Supported bridge configurations– Simple and continuous spans

– Straight and curved bridges

– Standard rolled shapes and welded I girders

– 6th Edition (7th coming soon) of the AASHTO LRFD Bridge Design Specification, and

– 2nd Edition of the AASHTO Manual for Bridge Evaluation.

• Provides:– Parametric modeling

– Streamlined analysis

– Design code checking

– Load Rating

– Transparent dead and live load analysis by STAAD.Pro

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LEAP Bridge Steel Overview

• General Commands

– Libraries

– Tutorials

– MS export …

• Modeling Commands

– Roadway

– Superstructure

– Substructure

– Analysis, design, rating


General Commands

View toggles

Add

Remove

Refresh Bridge

Libraries

DTM view

options

Export model

to

MicroStation

Input Data

Report

Tutorials

RSS

Feeds

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General Commands - Libraries

• Libraries store…

– Appurtenances

– Vehicles/live load information

– Material tables

• Users can add and share library data

• Library elements are selected during the modeling process


General Commands – Appurtenance Library

• Parapets

• Medians

• Sidewalk

• Railings

• General

• Weights are included automatically as DC2 load on the model

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General Commands – Material Library

• Steel

• Concrete

• Reinforcing steel


General Commands – Vehicle Library

• Define

– Truck loads

– Lane loads

– Live load groups

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Bridge Modeling Workflow

• Roadway Elements

– Import from Civil InRoads, GEOPAK, MXROAD

– Enter in LBS

• Superstructure

• Substructure

• Analysis

• Design

• Load Rating

Wor

kflo

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Roadway Element Commands

• Roadway elements define the horizontal,

vertical and cross section geometry for

the bridge deck

• The cross section defines the left and right

edges of the slab

• Tapered cross sections define tapered

slabs

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• Import alignments and beam paths directly from MicroStation

Import From MicroStation


Roadway Elements – Roadway Definition

• Combines alignment, profile and cross section to define roadway/slab surface and edges

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Superstructure Commands

• Define the components of the superstructure

• 3D bridge model automatically updated geometrically and for loading

• 3D Model can be visualized at every stage of model definition


Superstructure – Pier & Abutment Locations

• Locate bridge support centerlines

• Define as pier or abutment

• Assign skew, if any

• Can be offset to alignment

• Define bearing locations

• Changes are automatically reflected in the overall model

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Superstructure – Deck Slab

• Define concrete deck longitudinal bounds

• When the deck is defined as multiple slab units, these can be used in the Deck Placement Sequence Command

• Sacrificial wearing surface included for dead load calculation

• Slab is considered non-composite until shear connectors are added


Superstructure – Deck Reinforcing Steel

• Used in section property calculations as stipulated by the AASHTO Spec.

– Strength: Article 6.10.1.1.1c – sections in negative bending

– Service: Article 6.10.4.2.1

• Used to determine minimum steel requirements per Article 6.10.1.7

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Superstructure – Member Groups

• Define the member layout or framing plan –straight or curved

• Simple or continuous spans

• Define from MicroStation elements

• A single bridge model can contain multiple member groups

• Member groups can be copied in their entirety (including members) to different locations


Superstructure – Standard Section List

• Select standard shapes for…

– Cross frames

– Main members

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Superstructure – Member Definition

• Define member geometry using schedule based methodology

• Web transitions

• Copy members

• Hybrid girders

• Welded plate or standard section


Superstructure – Cross-Frame / Diaphragm Definition

• Struts, X, V, inverted V

• Build from standard shapes

• Control orientation of members

• Analyze as frame or truss

• Used in grillage model as equivalent beam using methods from NCHRP Report 725

• Individual member forces computed

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Superstructure - Cross-Frame / Diaphragm Location

• Locate per bay or entire bridge

• Can be skewed

• Wizards available to assist layout

• Manipulate individually


Superstructure – Stiffener Definition and Location

• Define bearing, connection plates or shear stiffeners

• Wizards available to assist locating stiffeners

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Superstructure – Shear Connector Definition and Location

• Define stud, channel or generic

• Locate along members by range with longitudinal and transverse spacing

• Define regions of composite action

• Fatigue and Strength checks


• Define locations of moment release along any member

Hinge Locations

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Superstructure – Appurtenance Locations

• Locate appurtenances such as parapets, medians, sidewalk, etc.

• DC2 load automatically calculated

• Parapets define travel way for live load


Substructure – Piers and Abutments

• Piers

– Multi-column

– Hammerhead

• Abutments

– Pile cap

– Stem wall

• All geometry defined in LBS and passed to RC-PIER for design

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Substructure – Support Conditions

• Control movement at bearing locations

– Pinned

– Roller

– Fixed

– Float

– Directional


Analysis Commands

• Point of Interest Locations

• Deck Placement Sequence

• Loads

• Analysis

• Design

• Rating

• Substructure Design/Analysis

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Analysis – Point of Interest Locations

• Locations where analysis results and design code checks

• Auto located at X-frames

• At section breaks

• User defined locations


Analysis – Deck Placement Sequence

1

2 3

4

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Analysis – Deck Placement Sequence

• Provides means to analyze stress effects in the steel and concrete slab as slab segments are poured in each stage

• The process is closely tied to Constructability checking (6.10.3)

• LBS automatically generates stages, load cases and load combinations

• User defined load cases at any stage

• Deck overhang, construction and finishing machine loads can be added


Analysis – Deck Placement Sequence Simulation

Slab 1 Slab 2 Slab 3 Slab 4 Slab 5

Plan View of Bridge

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Analysis - Loads

Load Combinations• The Loads command allows entry of

load cases (right) and Load

combinations (left)

• Loads Cases can be:

• Permanent DC1 dead load

• Superimposed DC2 dead load

• FWS/Utility DW dead load

• Uniform temperature

• Pedestrian

• Wind

• and Live load

• Load cases and combinations can

be user defined for any stage.

Load Cases


Analysis – Dead Load

• Most dead load cases are auto generated and updated as the model changes

• Dead load cases can be user defined

• DC1 loads applied to the non-composite structure

• DC2 loads applied to the long term composite structure (N=3N)

• DW loads applied to the long term composite structure (N=3N)

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Analysis – Live Load

• Live load cases consist of:

– Vehicles

– Lane

– Combinations of vehicle and lane

– Notional effects

– Special envelope and optional factors

– Optional side by side load

• Live loads applied to the short term composite structure (N=N)

• All live loads are stored in the Vehicle Library


Analysis – Load Combinations

• LEAP Bridge Steel auto generates default load combinations for construction and final stages

• Construction stage loads include all automatically generated loads from previous stages (for stress accumulation)

• User defined load combinations can be added to any stage

• Construction stage combinations default to Strength I

• Final stage load combinations default to Strength I, Service II and Fatigue

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Analysis – Structural Analysis

• There currently are two analysis options

– Line girder

– Grillage

• Line Girder Live load distribution factors calculated automatically

• Analysis performed for all dead and live load cases

• Analysis takes into account structure stiffness variations in each stage

• Results displayed in report and graphic form

• Results exported to multiple formats: PDF, Excel, HTML, RTF, MHT, Text, JPG, PNG…..


Analysis – Results

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Analysis Results – Camber Diagrams


Analysis - Reports

• Dead Load

– Node displacements

– Girder forces

– Cross frame forces

– Support reactions

• Live Load

– Distribution factors

– Girder forces

– Node displacements

– Cross frame forces

– Support reactions

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Analysis - Design

• Design code checks per AASHTO LRFD 6th Edition (7th Edition updates coming)

• Load rating per Manual for Bridge Evaluation, 2nd Edition

• Detail reports organized by member and Point of Interest

• Code check failures are flagged


Analysis – Design Reports

• Under / Over Design

• Section Properties

• Section Limits

• Factored Forces

• Factored Stresses

• Intermediate values

• Shear connectors

• Constructibility

• Service Limit State

• Strength Limit State

• Fatigue

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Analysis – Design Reports


Analysis - Rating

• LBS 1.0 performs design Inventory and Operating rating

• Rating models are copied from the design model or other rating models – multiple rating models possible

• User defined combinations

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Analysis – Substructure Design/Analysis

• Substructure geometry and superstructure description are seamlessly passed to RC-PIER

• RC-PIER performs analysis and design


Export to MicroStation

• The complete bridge model is exported to MicroStation as a 3D intelligent model

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Steel Bridge designed by LEAP Bridge Steel


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Upcoming Events – Important Dates

• Save the Date

– Bentley LEARNing conference

• May 6-7, 2015 – Indianapolis, Indiana

• Bentley Bridge SIG Meeting included

– Bentley Bridge SIG

• June 11, 2015

• 3D Modeling with LEAP


design and rating of steel bridges - squarespacebridge+steel_2015.pdf · ... of the aashto lrfd...

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