Load Rating of a Steel Composite

Girder Bridge

Luis J. Vila, Ph.D.

Structural Engineer, GM2 Associates, Inc.

MIDAS 2016 Elite Engineers Webinar Series

April 07, 2016

2

Presentation Outline

Introduction

Modeling Aspects

Construction Stage Analysis

Live Load Analysis

Load Rating

Analysis of Expansion Joint

3

Introduction

Bridge location

4

Introduction (Cont’d)

Bridge location

5

Introduction (Cont’d)

Bridge 00032, Stamford, CT

MNRR

I 95

6

Introduction (Cont’d)

Built in 1958

Rehabilitation work since: joints replacement, substructure

strengthening, widening

7

Introduction (Cont’d)

Bridge 00032 overview:

17 spans carrying I95 over MNRR and local roads

1065 ft long

16 Steel Composite Girder Spans

Main span over MNRR

• - Composite and Non-composite

Floorbeams

• - Steel Through Girders

8

Introduction (Cont’d)

Span 7: I95 over Metro-North Railroad (MNRR)

Steel Through Girders

Composite and Non-composite Floorbeams

NB Traffic

SB Traffic

Diagonal Expansion Joint

11 ft

200 ft Span

9

Defining Bridge Geometry

Import geometry from Microstation or AutoCAD

Bridge Wizard (e.g. Steel composite, PSC, Cable Stayed, Suspension)

Define each node and element

10

Steel Composite Girder Modeling

Material:

• - SRC

Section:

• -Composite

• -Ds/Dc=0

Weight of concrete

applied as distributed

load

Definition of Steel Composite

Girder Geometric and Material

Properties

11

Steel Through Girder Modeling

Built-up Section

• - 2 Web Plates

• - 6 Plates for Flanges

• - Longitudinal Stiffeners

Modeled using Midas Civil General

Section Designer Tool

• -Import shape from

Microstation or AutoCAD

• - Determines Section Properties

of Built-up Section

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Steel Through Girder Modeling

13

Concrete Deck Modeling

Deck Dummy Elements

• -Weightless concrete

• -Provide transverse connection

between floorbeams

• -Transverse distribution of live

loads and composite dead loads

14

Diagonal Expansion Joint Modeling

Diagonal Expansion Joint

Compression only link

Rigid elastic link

15

Construction Stage Analysis

Composite stage

Non-composite stage

Composite Section for Construction

Stage

Stage 1: Steel Only

16

Construction Stage Analysis (Cont’d)

Stage 3: Composite Action

Stage 2: Concrete Pour

17

Live Load Analysis

Live Load Analysis for Load Rating:

• -Design (HL93)

• -CT Permit

• -CT Legal

Traffic Lane Definition

• -Traffic Lane Optimization

Center (Default) Left Right

18

Live Load Analysis (Cont’d)

Traffic Lanes

• -Forward and backward moving load

19

Live Load Analysis (Cont’d)

Live Load Analysis Results

• -Moment Diagrams

Non-Composite Floorbeam

20

Live Load Analysis (Cont’d)

Live Load Analysis Results

• -Displacement Results for HL93 Truck

21

Load Rating

Strength Limit State: Service Limit State: Fatigue Limit State:

22

Load Rating (Cont’d)

Fatigue Limit State

23

Load Rating (Cont’d)

Parameters for Fatigue Rating

24

Load Rating (Cont’d)

Fatigue Limit State

• -Rating Results

If RF < 1.0 => Check for finite fatigue life

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Analysis of Expansion Joint

Analysis of Expansion Joint Under Live Load

NB Traffic

SB Traffic

Corrosion of floorbeam below expansion joint due to active water

leakage

Damaged deck due to repeated impacts against top flange of floorbeam

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Analysis of Expansion Joint (Cont’d)

Span 7 over MNRR

Planking for floorbeam

inspection

27

Analysis of Expansion Joint (Cont’d)

South Side of Non-Composite floorbeam North Side of Non-Composite floorbeam

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Analysis of Expansion Joint (Cont’d)

Deck deterioration along joint

29

Analysis of Expansion Joint (Cont’d)

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Analysis of Expansion Joint (Cont’d)

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Analysis of Expansion Joint (Cont’d)

Determine the location of the truck when deck detaches from top

flange

• -MIDAS Civil Moving Tracer Tool

Location of truck causing maximum and minimum displacement of

deck

• -Two locations of trucks causing a gap between deck and top flange

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Analysis of Expansion Joint (Cont’d)

Moving Load Tracer

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Analysis of Expansion Joint (Cont’d)

Moving Tracer Results

Maximum (upward) displacement at midspan

Minimum (downward) displacement at midspan

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Analysis of Expansion Joint (Cont’d)

Case 1: Maximum (upward) displacement of deck at expansion joint

Through

Girder

(South)

Pier 6 Pier 7

Deck

Joint 16 kips wheel load4 kips wheel load

N

Through Girder

(North)

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Analysis of Expansion Joint (Cont’d)

Deck

Joint

Through

Girder (South)

Through

Girder

(North)

gap

Case 1: Maximum (upward) displacement of deck at expansion joint

36

Analysis of Expansion Joint (Cont’d)

gap

gap

Case 1: Maximum (upward) displacement of deck at expansion joint

37

Analysis of Expansion Joint (Cont’d)

Through

Girder (South)

Through Girder

(North)Pier 6 Pier 7

Deck

Joint16 kips wheel load

N

4 kips wheel load

Case 2: Minimum (downward) displacement of deck at expansion joint

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Analysis of Expansion Joint (Cont’d)

Deck Joint

Through

Girder (South)

Through Girder

(North)

gap

gap

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Conclusion

midas Civil advantages

• -User friendly

• -Graphic user interface

• -Fast and accurate bridge modeling

• - General section designer

Load Rating Method

• -Composite girders/floorbeams (midas Civil)

• -Non-composite floorbeam (spreadsheet using results

from midas Civil)

• -Through girders (spreadsheet using results from midas

Civil)

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Questions?