Internal force evaluation of columns in electrostatic precipitator casings under transverse loads considering the cooperative load bearing of columns and wallboards

The structure and loading conditions of the enclosed structure of precipitator casings are highly complicated. Currently, there is no accurate method to calculate the internal force distribution in the columns of precipitator casings under transverse loading. In this paper, we investigate a method to calculate both the internal force and strength of precipitator casing columns when a transverse load is directly applied to the wallboard. Both theoretical and finite element analyses are conducted. To effectively study the transferring mechanism of the transverse load, a block of wallboard is regarded as an independent plate with simply supported edges separated by upper and lower neighboring stiffeners and columns on the left and right sides. Concentrated forces are transferred at the location of each stiffener, and nonuniformly distributed loads are transferred between the stiffeners. The column is regarded as an elastic multi-span continuous beam and the maximum bending moment and shear force are evaluated using the moment distribution method. Calculation tables for the maximum bending moment of various columns are determined based on the number of column spans, the number of wallboard blocks in the range of the corresponding column span and the aspect ratio of the wallboard block. Considering the load bearing interaction between the column and wallboard, a composite section is proposed to revise the strength evaluation method for the normal cross sections of columns. A composite section consists of an H-shaped column and the wallboard within the effective width. The results show that for a composite structure composed of a wallboard and a column, the contribution of the wallboard to the bending resistance increases as the wallboard thickness increases or as the wallboard width decreases. The contribution of the column to the bending resistance increases as the inertial moment of the column section increases or as the column span decreases. Based on the statistics of the computation results for the precipitator casings with usual geometries in engineering practice, a unified magnification factor for the column section modulus is proposed on the safe side. Compared to the conventional simplified internal force calculation methods, the proposed calculation method can more conveniently and accurately evaluate the maximum normal and shear stresses for a column section to assist the design of safe and economical column sections under transverse loading.