Keywords: Corrugated Steel Web, Shear Buckling, Local Buckling, Global Buckling, Interactive Buckling, Pure Shear

Abstract:

Since a corrugated steel plate has sufficient shear stiffness without shear stiffeners out of plane direction, the use of corrugated steel plate as a web of bridge structure is increasing. Corrugated plates may show different structural behaviors from flat plates. Previous researches have shown that the corrugated webs can fail by local, global and/or interactive buckling modes. Various strength and design equations for each mode have been suggested. However, the results of such equations showed wide variations. This paper focuses on the examination of the behavior of corrugated plate web under shear forces. Eleven test specimens with corrugated steel web are manufactured to investigate local buckling(4EA), global buckling(3EA), and intermediate buckling(4EA). The size of the most specimen are about 6m in length and maximum of 2m in height. The pitch of the corrugation is about 20cm with 8mm thick plate. Pure shear tests are performed to investigate the shear buckling strength and the yield strength, and the test results are compared with the results from finite element analyses. From the results, design equations for shear buckling of the corrugated plate are proposed.

Shear Buckling Tests

A local buckling theory assumes that folded parts of a corrugated web behave as supports, therefore the strength is determined by elastic shear buckling equation in one panel. But this assumption isn’t always applicable because a geometrical property such as depth of corrugation is not considered. Applicability of existing theory is examined through local buckling specimens, which have same theoretically buckling strength but different shapes.

The global shear buckling theory was developed with the upper and lower boundary conditions of web plate as simply supported four edges. This assumption underestimates shear strength and can lead to a conservative design. As the upper and lower connection of web plate is generally embedded to concrete slab, a boundary condition between fixed and simply supports should be considered. Global shear buckling tests focus on investigation of boundary condition.

In case that local buckling strength is similar to global buckling strength(),
the interactive buckling occurs and I1~I4 specimens are designed with the ratio of buckling strength close to the value of 1. Ratio of lateral and longitudinal stiffness(Dy/Dx) dominates characteristics of corrugated plate. It is examined whether the existing equation is applicable to corrugated plates with stiffness ratio(Dy/Dx) smaller than 200, the ratio for general bridge structure. Fig 1 shows set-up of corrugated web shear buckling test using a 10,000kN-UTM.

Fig. 1 Test setup

Test Results

The behavior of trapezoidal corrugated steel plate has not been clearly investigated in spite of its various advantages. This paper evaluates the shear buckling behavior of trapezoidal corrugated steel plate through experimental tests. Furthermore, the finite element analyses are performed to examine the validity of experimental tests. The results are as follows:

• The coefficient of corrugated depth(d) should be included in the local buckling formula because the corrugated depth affects the out of plain stiffness.
  
  
• The range of buckling coefficient in the global buckling formula is between 36.0 and 64.8 due to the change of boundary conditions. The buckling coefficient approaches to the value of 64.8(fixed support) as the ratio of buckling stress, G/L decreases, and the buckling coefficient approaches the value of 36(hinged support) as the ratio of buckling stress increases. Thus, it is suggested to use the value of 36 as the buckling coefficient, corresponding to the hinged support condition, in the conservative point of view.
  
  
• The possibility for the occurrence of interactive buckling increases as the ratio of elastic buckling stress, G/L, approaches to the value of 1.0. In addition, several parameters such as the stiffness ratio (Dy/Dx), the corrugated depth to thickness ratio (d/tw), and the width of horizontal panel to web depth ratio (a/hw) should be considered in the interactive buckling formula.  
  
  
• In order to precisely evaluate the buckling instability of corrugated steel plate with the orthotropic properties, it is preferable to consider the additional parameters such as the corrugated depth to thickness ratio (d/tw) and the width of horizontal panel to web depth ratio (a/hw); previous studies have evaluated the buckling instability considering only the stiffness ratio (Dy/Dx). In the case of d/tw>10 or a/hw<0.2, the trapezoidal corrugated steel plate is thought to behave orthotropically in general.

Fig.2 Buckling modes