SHRP R19B BRIDGE FOR SERVICE LIFE BEYOND 100 YEARS ...
Transcript of SHRP R19B BRIDGE FOR SERVICE LIFE BEYOND 100 YEARS ...
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
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