Doobyong Bae

Experimental Study on Fatigue Strength of In-plane Welded Gusset Joints

This paper presents the results of three phases of fatigue tests for the fatigue strength of in-plane welded gusset joints which are most common details inevitably existed in the region of high stress range. Totally fifty seven fatigue specimens with various thickness and strengths were made and the tensile fatigue tests were performed. One full scale beam fatigue tests was also carried out. The validity of the fatigue strengths of those details in specification was proved and the effects of thickness of flanges and welded attachments, length of attachments and the strength of applied steel were examined. The characteristics of crack initiation and propagation were also observed. The test results are evaluated by comparing with other test data and the fatigue criteria of other countries. In order to find out the degree of stress concentration in the weld toe depending on geometric configuration such as the attachment length and transition radius, analytical works were also carried out. Comparing with present specification, analytical results indicate that there are need of revising and subdividing the detail categories.

Comparison of Wind Load Provisions Based on the Wind Buckling Behaviors of Plant Tank

There are no consistent wind load provisions to design the plant tank in Korea. To suggest the appropriate design wind load, five kinds of specifications including KS B 6283, API 650, ASCE 7-10, EN 1991-1-4 are compared. To evaluate the adequacy of wind load specification in each code first, pressure coefficients were calculated in each code and compared with the results of wind tunnel test. Finite element analyses using linear bifurcation analysis were performed with the parameter of h/d and f/d (h : height of cylinderical part of tank, f : roof heigh, d : diameter of tank). By analyzing the results, appropriate wind load criteria which reflects the real wind actions and easy to apply will be suggested.

Ultimate Flexural Strength of Hybrid Composite Girders Using High-Performance Steel of HSB600 at Sagging Bending

HSB600 is a high performance steel which is currently developed by a Korean steel company. HSB600 does not have an obvious yield point and yet undergoes large strains after proportional limit. Its 0.2% offset yield strength and tensile strength are over 450 MPa and 600 MPa respectively. Modern standards such as AASHTO LRFD and Eurocode 4 provide rules for determining the flexural strength of composite girders. These rules are based on the presence of a yield point in the stress-strain diagrams of steel materials. This paper presents experimental works conducted for the purpose of verifying the ultimate flexural strength of hybrid composite girders using the tension flange made of HSB600. Totally five composite girder specimens (one hybrid and a conventional composite girders (Series I), three hybrid composite girders (Series II)) have been tested. The results of the test are compared with the flexural strengths obtained by nonlinear moment-curvature analysis based on the stress-strain curves of each material and the code predictions. The test results show that, if the plastic moment is calculated with using 0.2% offset yield strength, the ultimate flexural strength is underestimated. Finally, based on the test results, some design recommendations regarding the flexural strength and the ductility requirement for hybrid composite girders with HSB600 are suggested.