Conical shell structures are commonly used in many engineering systems, and vibration suppression is very important to realize the desired function. In this study, piezoelectric ceramics were used as actuators/sensors with a multimodal fuzzy sliding mode controller to suppress vibrations of conical shell structure for the first time. The structure's natural frequencies and mode shapes were obtained through modal analysis using finite element method and verified by modal tests. The agreement between analysis and test results verified the finite element method was appropriate. A multimodal fuzzy sliding mode controller was subsequently designed based on the analysis to provide active vibration control. The resulting controller was tested experimentally for the conical shell structure. The experimental results indicated that the proposed controller can effectively use to suppress vibration for the conical shell structure.

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The fatigue assessments for boom girders of a concrete pump truck, which is typically a welded box girder structure, were investigated in this study. Finite element analysis were conducted using shell and beam elements to obtain the stress histories of the boom girders. Field tests were performed to verify the finite element model. Then, the loading spectrum was developed using the rain-flow counting method. The fatigue assessments for the boom girders were evaluated using the nominal stress method and Miners cumulative damage rule based on the International Institute of Welding recommendation. It is found that some critical locations of the boom girder were at risk for fatigue failure. To overcome this problem, it is suggested to add diaphragms to boom girders.