Civil Engineering

 

Date of this Version

4-2017

Citation

Poster Presented at University of Nebraska-Lincoln Research Fair, April 4-5, 2017

Comments

Copyright (c) 2017 Fayaz Sofi & Joshua Steelman

Abstract

Research Objectives

• Assessment of alternative load distribution methodologies for potential discrepancies that arise when evaluating distribution behavior of skewed steel girder bridges.

• Investigate the influence of skew and material nonlinearities (concrete cracking and steel yielding) on

• Load distribution behavior (elastic versus inelastic).

• System capacities (yielding and ultimate).

Summary and Conclusions • Influence of skew was examined on load distribution behavior, and nonlinear system-based capacities (yielding and ultimate) of composite steel girder bridges in presence of full material nonlinearities. In addition, assessment of two general definitions (beam-line and response fraction approaches) for quantifying load distribution behavior was performed for a range of skew variations on a validated in-service bridge model. • Response-based fractions (such as deflections, strains, curvatures and moments) have limited applicability at higher skews (≥ 30º), significantly biasing load effect distribution factors compared to the reference beam-line definition. • The propagation of concrete cracking results in a substantial increase in distribution factors at higher skews. For 60º skew, an increase up to 36% in distribution factor of girders relative to the uncracked elastic state was observed for the case study in-service bridge. • Load distribution factors decreased with increasing skew as load progressed from elastic to ultimate states. However, AASHTO LRFD based distribution factors were overly conservative in predicting distribution behavior at all load levels (on average 66% higher at elastic and 90% higher at ultimate for critical girder). • System-based ultimate capacity increased with skew, but the first yielding initiation load capacity was poorly correlated with skew despite the reduction of moment demands in girders.