Thin-walled structures such as ship and offshore structures basically consist of a number of plates stiffened by different types of stiffeners.
Continuous welding may be used for attaching stiffeners to plates, but this technique requires a large amount of welding, adds weight to the structures, and increases construction costs. In order to reduce the costs of labour and materials and save weight of the stiffened plate structures, non-continuous welding is frequently applied to the attachment of plates and stiffeners. This method of fabrication also lowers the magnitudes of welding residual stresses more than continuous welding.
Over the past few decades, the buckling and collapse behaviors of continuously welded stiffened plates under different loading conditions have been widely investigated in order to develop analytical, empirical, numerical and experimental methods.
However, little has been studied on the behavior of intermittently welded stiffened plates and, furthermore, only some numerical and experimental studies have been carried out.
Mun Ji Song, a section head at the Mirae Academy of Science and Technology, has proposed a simplified method for ultimate strength estimation of intermittently welded stiffened plates under uniaxial compression. The plate and stiffener of a stiffened plate were considered as individual beam-columns. The whole span of an intermittently welded stiffened plate was divided into welded and non-welded segments. For modeling the behavior of the intermittently welded stiffened plate, the differential equations which describe the bending of the beam-columns in welded and non-welded segments were considered.
Special attention was paid to the following two cases.
i) Case 1
It was assumed that beam-columns 1 and 2 are deformed in contact and deflections of the beam-columns 1 and 2 are equal to each other.
ii) Case 2
In this case, it was assumed that beam-columns 1 and 2 are deformed in non-contact and behaviors of the beam-columns 1 and 2 are independent of each other.
Based on the model, the Euler limit load of the intermittently welded stiffened plate was calculated. The intermittently welded stiffened plate was changed into a continuously welded one with the equivalent Euler limit load. The Paik’s empirical formulation was used to estimate the ultimate strength of the changed continuously welded stiffened plate under uniaxial compression.
The proposed method demonstrated a good agreement with FEA results. This suggests that ultimate strength of chained and staggered welded stiffened plates can be estimated by the proposed method.
For more information, please refer to his paper “Study on Ultimate Strength Estimation of Intermittently Welded Stiffened Plates under Uniaxial Compression” published in the SCI Journal “Marine Structures”.
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