SHRP R19B

BRIDGE FOR SERVICE LIFE BEYOND 100 YEARS:

SERVICE LIMIT STATE DESIGN

TRA 2010SHRP 2/ FEHRL Joint Symposium

Brussels, BelgiumJune 10, 2010

Modjeski and Masters, Inc.: John Kulicki, Ph.D., P.E.Wagdy Wassef, Ph.D., P.E.

University of Delaware: Dennis Mertz, Ph.D., P.E.University of Nebraska: Andy Nowak, Ph.D.NCS Consultants: Naresh Samtani, Ph.D., P.E.

Research Team

TRB/SHRPDr. Monica Starnes, Senior Program Officer

What Are We Doing?

• Calibrate the existing service limit states of AASHTO LRFD for a wide range of components

• Develop new service limit states as needed

Expected Products

• Framework for calibration• Bridge design procedures and proposed

specifications • Changes that include design for durability • Tools required for future SLS improvement

Current General SLS’s• Live load deflections• Bearings-movements and service forces• Settlement of foundations and walls

Current Steel SLS’s• Permanent deformations in compact steel

components • Slip of slip-critical bolted connections

• Fatigue of structural steel, steel reinforcement (and concrete) through the fatigue limit states

Current Concrete SLS’s

• Load induced– Stresses in prestressed concrete under

service loads– Crack control reinforcement

• Non-Load induced– Shrinkage and temperature reinforcement– Splitting reinforcement

Desired Attributes

• Is an SLS meaningful? Can it be calibrated?

• Does it really relate to service---or something else?

• Can (should) aging and deterioration be incorporated?

• Can it reflect interventions?

Phase 1 Scope• Literature Survey• Service life approaches

- Full probability approach preferred- Semi-probabilistic partial factor approach- Deemed to satisfy

• Compile statistical database – Availability and sources

• Identify successful elements, systems• Compile data – loadings, environmental

factors affecting service life

Phase 1 Scope (Cont’d)

• Develop SLS calibration procedure- Criteria-limit state function- Data to generate statistics- Include time effects on loads and

resistance• Form Independent National Committee to

critique approach and data

Special Challenges

• Criteria – What matters?• Significance of selected limit state• How often can it be violated?• Correlated loads and resistance• Time variance of loads• Deterioration modeling• Resistance related to geography/environment• Role of workmanship• Paucity of data

Where Are We?• Researching background of current SLS• Searching for other needed limit states

– Literature Survey– Owner Survey – 32 out, 16 back so far– Other specifications

• CHBDC• Eurocode• BS 5400• Japanese Geotechnical

– One team member on ABSS European Scan

• General trend – Additional limit states would not have affected reduced serviceability – most respondents said nothing more required

• Correlations between reduced serviceability and deterioration– Corrosion and section loss– Bridge deck deterioration– Beam end deterioration

Survey of Owners - Major Points

Survey of Owners - SLS Needs

• Foundation settlement• Use of reduced section due to corrosion

and corrosion protection• Foundation movements – Majority of

respondents not following Article C10.5.2.2• SLS load case for permit trucks like

Strength II• From 19A – Criteria for jointless bridges and

integral abutments

Weigh-in-Motion Data

• Truck WIM was obtained from the FHWA, State DOT’s and NCHRP Project 12-76

• Total number of records included in the analysis exceeds 50 million

• HL-93 adaptable as national notional SLS live load model

• Site/region specific live load should be accommodated

Phase I Report Submitted Mid-May 2010

Framework for Calibration

• Two versions-research and implementation

• Evolution not revolution – similar to ULS• 9 basic steps-not all needed in

implementation version• Can use Monte-Carlo analysis for

probability of failure β γ and Φ• Can also use closed form solutions for β

Framework for Calibration-attributes• Ability to accept a user supplied

deterioration • Ability to react to user intervention as

reflected in an improved resistance, also user supplied

• Ability to accept either a user supplied database to determine a new bias and COV, or a user supplied bias and COV from an external calculation

Framework for Calibration-attributes• Accept user supplied live load model• The ability to accommodate a user supplied

resistance model, especially important for the geotechnical community due to the regional nature of practice in that discipline

• Robust and self policing

Framework – Reliability Change with Time

Rel

iabi

lity

Inde

x, β

CSI

βI

0

1

Time Service Life

TLS

A B S X

CLS

βT

βCC CC

Z

1.CSI0;ββββ

TLSCLSCSI

TI

CCI ≤≤−−

−=−= 11

Framework - Intervention

Replace

Repair

Service (Design) Life, TD = 100 yrs

CSI

βI

0

1

25 years βT R

elia

bilit

y In

dex,

β

75 years 50 years

Service (Design) Life, TD = 100 yrs

CSI

βI

0

1

25 years βT R

elia

bilit

y In

dex,

β

75 years 50 years

Toolkit

• The implementation framework updated based on the input from the Independent National Committee

• Databases (including a well-defined data format) • Software tools used in the SLS calibration• Monte Carlo spreadsheets• Instructions for developing new or revised

spreadsheets • To the extent possible a set of resistance

deterioration models• Brief users’ manuals with examples

Continuation of Phase I Tasks

• At this stage of the project, it is clear that little has been found in terms of:– need for new service limit states– criteria for problematic components e.g. joints

and bearings,– new proposed systems, subsystems,

components and details from other related projects, and

– a clear relationship between inspector derived “condition” and structural resistance.

Continuation of Phase I Tasks

• At this stage of the project, it is clear that little has been found in terms of:– new, transformative knowledge of the

performance or durability of systems, subsystems, components and details from other related projects which are still early in their research plan

• BUT----many projects are still “In Progress”

Improvements to the Existing SLS

• Load-induced fatigue,• Live-load deflection,• Permanent deformation,• Cracking of concrete,• Settlement of foundations, and• Horizontal movements of abutments.

New SLS

• Cracking of Concrete: Total strain or reduced-shrinkage strain approach, and

• Lifetime bearing movement limitations.

Above: The Mississippi River Bridge at Quincy, Illinois, USA

Questions?

Left: Bluewater Bridges (I & II) between Port Huron, Michigan, USA and Point

Edward, Ontario, Canada

Questions To the Audience

Questions

• Are there any SLS provisions in the EuroCode or other specifications that speak to the probability of failure (exceedance of SLS criteria)?

• What new information is available on the service limit state for expansion joints and bearings.