Lateral distribution of live load moment in skewed NEXT beam bridges: Fid-Bau Portal

Lateral distribution of live load moment in skewed NEXT beam bridges

Huang, Jianwei

Developed by the PCI northeast, northeast extreme tee (NEXT) beams provide a solution to achieve rapid construction and minimal bridge maintenance. The NEXT beams have shown several advantages over the traditional I-shaped and adjacent box beam sections. In current practices, the design live load moment in an I- or box-beam in skewed bridges is calculated in accordance with the LRFD approximation method with a live load distribution factor (LLDF) and a skew correction factor (SCF). As a new bridge section, live load distributions in NEXT beam bridges however have not been addressed in the LRFD bridge design specifications. In this sense, this paper intends to explore the lateral distribution of live load moment in simply supported skewed NEXT beam bridges, aiming to assess the suitability of the LRFD approximation method for NEXT beam bridges. Through employing validated finite element (FE) analyses, a total of 160 NEXT beam bridges with five different skew angles (i.e., 0° to 40° with 10° intervals) were investigated in this paper by a comprehensive parametric study. The parameters of beam section, span length, number of beams in a bridge were considered in the study. A method for computing the FE-SCFs for skewed NEXT beam bridges was proposed. The FE-SCFs were compared to the LRFD-SCFs by percent errors. Results from this study showed that the LRFD-SCFs governed the FE-SCFs when the skew angle is ≤30°. However, it was observed that some FE-SCFs exceeded the LRFD-SCFs by up to 5.65% when the skew angle is 40°, indicating that using LRFD-SCFs may lead to an unsafe design in this case. It is recommended that the LRFD-SCFs be used for NEXT beam bridges with skew angles ≤30°, whereas the LRFD-SCFs should be increased by 6% in order to achieve a sufficient safety margin for NEXT beam bridges with a skew angle of 40°.