Instrumentation and Modeling of Concrete Bridge Decks Sponsored
Instrumentation and Modeling of Concrete Bridge Decks Sponsored by: Matthew D'Ambrosia, Chang Joon Lee, David Lange, Zachary Grasley OBJECTIVES FINITE ELEMENT MODELING MATERIALS Measure strain and temperature of six newly Building the model consisted of three stages Shrinkage and creep modeled using RILEM Draft Recommendation B 3 fit with laboratory test data and incorporated into structural model constructed concrete bridge decks Assess overall deck behavior during daily cycles and long term changes of temperature and internal humidity Determine stress development in concrete deck due to drying shrinkage and temperature changes using field data and FEM Concrete Mixture Proportions Assess the potential for early age and long term cracking. Evaluate material and structural interaction and implications for design Thermal Analysis INSTRUMENTATION RESULTS Deck-girder interaction Structural system/boundary conditions DISCUSSION AND CONCLUSIONS Example: I-70/Big Creek Bridge, Clark Co. , IL Structural finite element model was validated (typical for other bridges) successfully with field strain measurements using field temperature measurements and material model as input High performance concrete bridge deck Skewed alignment Continuous supports 275’ long, 4 spans, longest span 67 feet Concrete girders 16 strain gages, 26 thermocouples, 6 RH sensors Comparison of two bridge structures with Deformation Map (1000 x) Duncan Rd Bridge, 56 Days Deformation Map (1000 x) Big Creek Bridge, 56 Days similar concrete materials showed that structural restraint produces higher stress in the bridge with concrete beams. Stresses were generated in areas of higher restraint such as over the pier and over the girders Majority of stress development over time is due to drying shrinkage - Temperature changes deform the whole bridge system, including the girders and do not induce very much stress Typical Sensor Locations Role of shrinkage on bridge deck stress Strain gage and thermocouple positions Cellular antenna - Model strain validated with actual field strain measurements Model stress predictions show higher stress in concrete beam bridge transmits data through analog cellular phone modem connection Solar panel - charges 12 V lead-acid battery Can low shrinkage concrete avoid cracking? Datalogger – reads Shrinkage reduction of 15 -40% would reduce most tensile sensors and stores data until transmission Data collection and transmission system stresses below 400 psi and reduce cracking Maximum stress development in Duncan Rd bridge, 200 psi threshold (max. stress is less than 400 psi) Maximum stress development in Big Creek bridge, 400 psi threshold
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