Abstract：A numerical investigation is presented to in-plane strength and design of the pin-ended circular steel arches with a welded I-section subjected to web local buckling. A number of numerical examples of the arches were analyzed by using a large deflection elastic-plastic shell element model considering the web local buckling, and initial geometric imperfections and residual stresses were also involved in the analysis. Key parameters affecting the stability coefficient of the arches are involved in the numerical analyses under uniformly axial compression, which include web height-to-thickness ratio, slenderness and flange-to-web thickness ratio in a required range of flange width-to-thickness ratio. It is found that the stability coefficients of arches under the uniformly axial compression are exclusively related to the equivalent normalized web height-to-thickness ratio and the normalized slenderness, where the equivalent normalized web height-to-thickness ratio is introduced as an integrated result from both the web height-to-thickness ratio and the flange-to-web thickness ratio. Accordingly the design formula of the stability coefficients of the arches is proposed. Additionally, the influence of the web height-to-thickness ratio on strength of the steel arches under combined bending and compression is investigated numerically and a generalized design formula of the arches is developed for predicting the in-plane strength under general in-plane loading.
