The intended of this research is to prepare an analytical study to investigate the best width to depth section ratio (b/d) of horizontally curved steel box beam with constant cross-sectional area (without stiffeners) under single concentrated load at mid-span of the beam. The research adopts three – dimensional
nonlinear finite element analysis of steel box -section horizontally curved beams exposed to static load.
The isoparametric brick element of twenty-node has been used to represent the steel element; also, the
yield criterion used to compute the stress level of plastic deformation is Von-Mises. The simulation model
of the behavior of steel under tension and compression stresses is elastic-perfect plastic. A semi-circular
two-span continuous horizontally curved steel box beam was fabricated and tested under two point
loads at midspan of the beam, the results was compared with the results of the computer program
(NFHCBSL) used in this study. In general, it is found that the adopted finite element model to predict
the structural response of horizontally curved steel box beam has a good agreement with the test results
concerning estimate load-deflection response.
The effect of b/d ratio is considered by taken different values (20–100) % with the identical area of
cross-section. Also, the effect of curvature was studied by considering different values from beam with
half circle to straight beam. The results appear that the best (b/d) ratio is in between (0.3 and 0.4) at curvature between (0
and 90
) and the best (b/d) ratio is in between (0.4 and 0.5) at curvature between (90

and 180
). Also, the result showed that the decrease in carrying load capacity as the beam curvature
increased is independent on the value of b/d ratio.