Curved bridges live load bending moment distribution using straight and curved girders

• Published in: Revista IBRACON de estruturas e materiais 2022, Vol.15 (2)
• Main Authors: Rebouças, Arthur da Silva, Silva Filho, José Neres da, Barros, Rodrigo, Nascimento, Yngrid Rayane Freitas, Coutinho, Pedro Mitzcun
• Format: Article
• Language: English
• Subjects: bending moment distribution; bridges; curvature; ENGINEERING, CIVIL; FEM; live loads
• ISSN: 1983-4195; 1983-4195
• DOI: 10.1590/s1983-41952022000200008

The present study focuses on comparative parametric analysis of curved precast concrete bridges using straight and curved I-girders. The live load bending moment distribution for girders was studied using the bridge curvature and its relationship with the results obtained for a straight bridge. FEM 3D models were developed with restrictions on the transverse live load positions and with two different load models types: HL-93 (AASHTO) and TB-450 (NBR 7188, 2013). The parametric analysis results were calculated using the Modification Factor (MF) and the Bending Moment Distribution Factor (BMDF), calculated from the structural analysis of each model at the midspan. Globally, an increase was found in the total bending moment for the curved bridge models in relation to the straight bridge. In the examples herein studied, the larger the bending radius, the larger the maximal bending moment in the bridge center. For the external girders, the MF increases with the increase of the L/R. For the internal ones, the MF decreases with the increase of the L/R. In addition, the occurrence of “Load Shift” was different from the rigid body behavior, for there was demonstrated a different bending moment variation between external girder (G1) in relation to its adjacent (G2). Therefore, the structural behavior of straight (SG) and curved girders (CG) was analyzed, revealing that, in the SG, a significant gap occurred in the BMDF between G1 and G2 girders for all curvatures. For L/R = 0.6, it caused a difference of 17.8% in the BMDF between the G1 and G2 girders, while on the curved girders, a difference of only 6.6% was found. resumo: o presente estudo foca na análise paramétrica comparativa de pontes curvas utilizando utilizando longarinas retas e curvas pré-moldadas. As análises foram baseadas na distribuição transversal de momento fletor para a longarinas, na variação da curvatura da ponte e na relação desses parâmetros com os resultados obtidos em uma ponte reta. Foram desenvolvidos FEM 3D models com restrições nas posições transversais da carga-móvel e com dois tipos diferentes de modelos de carga: HL-93 e NBR 7187. Os resultados da análise paramétrica foram determinados utilizando o Fator de Modificação (FM) e o Fator de Distribuição de Momento Fletor (FDMF), calculadas a partir da análise estrutural de cada modelo na posição longitudinal do meio do vão. No âmbito global, contatou-se um aumento do momento fletor total nos modelos de ponte curva em relação à reta. Nos ex