## Bridge Evaluation by Load Resistance Factor Rating (LRFR). Application to TxDOT Prestressed Concrete I-beamsCurrently there are three methods available to evaluate the capacity of existing bridges: Allowable Stress Rating (ASR), Load Factor Rating (LFR) and Load and Resistance Factor Rating (LRFR). The most commonly used method in the past three decades has been the LFR. However, in 2001 AASHTO introduced LRFR, based on the reliability theory and actually used by most bridge evaluators. Using this new method the performance of a given bridge or its component can be estimated based on its reliability index. By taking into account the variability in load and resistance of the component, this reliability index increases public safety. |

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### Contents

1 Gusset plates of the I35W Bridge after collapse | 2 |

4 LRFD Design Live Load HL93 | 8 |

Bridge Evaluation Procedures | 12 |

1 AASHTO legal loads which control weight limits | 18 |

5 Probability density function of load and resistance | 25 |

7 LRFR Flow Chart | 35 |

Evaluation Examples | 40 |

3 Type A B C IV Beams HS20 | 41 |

Summary Of Results and Conclusion | 152 |

### Common terms and phrases

AASHTO Asphalt concrete beam end beam to centroid Calculate Center of gravity centerline composite section compression steel compressive strength compressive stress critical section critical shear section Dead load debonded depressed strands Distance from top Distribution factor dNew dpEnd dvcr end regions Ep-ApsEnd EpAps factor for shear falw flange width flexure resistance ftkiP haunch kip-ft lane loaded legal load Live Load Factor Live load shear Load and Resistance load effect load factor rating load rating LRFD Eq LRFD Table LRFR LRFRD MDC1 MDC2 midspan modulus of elasticity nominal shear resistance normally distributed NOTGOOD Number otherwise probability of failure RDC2 Resistance Factor Rating safety index section located section modulus Shear Rating Factor Shear strength slab Strength 1 Limit stress in concrete sxNew tensile stress tension steel uNew VDC2 VDC2new vNew VuNew wearing surface Yield strength