Mechanical Behaviors And Strengthening Methods Of Typical Perforated Plates In Steel Pylon

Steel pylons are widely used in recently erected Chinese bridges. Insuch pylons with box sections, cutouts are often provided for the purposesof construction, access and service. The presence of holes in suchstructures is expected to result in a change in mechanical behaviors of theplates. However, there is very little usable reference in existing literaturesfor the influences of such novel holes on mechanical behaviors ofuniaxially compressed plates in steel pylons.This paper regards typical perforated plates in steel pylons, i.e. platesperforated by slotted holes and plates perforated by multiple elliptic holes,as research objects. Both analysis method and finite element method areused to investigate stress concentration factor and ultimate load of studiedplates. Moreover, further researches are taken to analyse strengtheningmethods and effects. The major works and conclusions include:(1) The development of steel pylons and research purposes areintroduced on the basis of existing relevant literatures in domestic andforeign. Research achievement of perforated plates is briefly summarizedand problems to be solved are proposed.(2) The uniaxial compression test of perforated plates is brieflyreviewed. The perforated plates models were conducted by the use ofANSYS software, where FE models were validated by comparingnumerical results with experimental data.(3) The stress concentration factors (SCF) of perforated plates with slotted holes and with continuous elliptical holes were analyticallydeduced using elastic mechanics methods and numerical computationmethods, respectively, followed by the example validations. Theinfluences of a/b and d/b on SCF were discussed on the basis of finiteelement analysis. Results show that SCF is unaffected by a/b when a/b isgreater than a critical value, and that SCF becomes higher as d/b isenlarged. Simplified SCF formulations used for finite perforated plates inpractical engineering were finally proposed by introducing plate widthrelated correction factors to the results of infinite planes.(4) Analysis method to solve ultimate load of plate with square holeis introduced, and applicability of the method is analysed by examples.Moreover, slotted holes and elliptical holes were both converted intorectangular holes. The positions of yield lines were determined with theaid of finite element results. Equivalent aspect ratios for long perforatedplates were also proposed.(5) Based on finite element analysis, the influences of dimensions ofstrengthening stiffeners on the ultimate strengths of strengthenedperforated plates were investigated, where ultimate strength enhancementfactors were introduced to quantify the strengthening effects. In case ofconstant stiffener height-thickness ratio hs/ts, enhancement factor increasedlinearly as hs/tswas increased, and then kept unchanged for various hs/tswhich were greater than the critical value. Simplified formulations forultimate strength enhancement factors, which can be used forstrengthening design of perforated plates in practical engineering, werefinally proposed on the basis of numerical fitting.(6) The main research results are summariedand the prospect of thefuture research is put forward.