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Prafulla Bahadur MALLA

Dr. Prafulla Bahadur MALLA

 (Sep. 1, 2022-)
Dr. Cai's Lab

Research interest

The applicant’s scientific research began in the area of structural engineering, during his Master's degree study in the field of Structural Engineering at Dalian University of Technology, China (2014-2017). He has studied structural engineering, with the goal of understanding the performance of reinforced concrete members and the development of numerical models. During his Master's research work, the study was carried out on the connection system of wind turbine towers with thin-walled reinforced concrete towers. Pre-stressing cables were proposed for the connection systems. The related experimental study has been carried out and a finite element model has been developed and verified with experimental results and further parametric study has been performed. It was confirmed that the connection systems using pre-stressing cables remained stable as well as increased the capacity of the thin-walled concrete tower to resist the lateral loads.

The applicant’s Ph. D. research has been finished at Sichuan University, China in 2020 involving study on precast concrete shear walls with dry connections by mechanical bolts to study its application in the construction of low-story buildings. The host professor of the applicant, Dr. Cai has co-supervised the applicant’s doctoral research. The main content includes two parts, test investigations (a quasi-static test and a shaking table) and FEM analysis of the bolted shear walls. The large-scale quasi-static test experiment on the horizontal connection of precast concrete shear walls to study the resistance mechanism and failure modes of the walls. A fiber-based FEM model (Opensees) was developed especially considering the yielding of gusset plates and crushing of concrete on the edges over which the shear wall overturns. The method developed was in good agreement with the experimental results and allowed robust calculation as compared to the Abaqus-based FE analysis which requires a longer computation time for cyclic loading analysis. The analytical method for the calculation of connection joint capacity in bolted connection precast concrete member as well as the shear capacity of the shear wall with bolted connection was proposed. On the other hand, an Abaqus-based FE analysis model was developed for shear walls with bolted connections. The methodology has proposed to select the contact stiffness for the contact interface of shear walls resting on the top of the foundation instead of selecting large contact stiffness which affects the initial elastic stiffness in the load-displacement curve. Also, to solve the convergence problem in cyclic loads, the applicant has proposed to increase the coefficient of viscosity for the concrete damage plasticity model but should adopt the lowest possible value in the model. All developed models have been verified by the experiments conducted.

After completing the quasi-static study of shear walls with horizontal and vertical joint connections, the applicant has conducted a shaking table experiment of a prototype two-story precast concrete shear wall building with high-strength steel bolt connections. A fibre-based 3-D FEM model was developed for precast concrete shear wall building to perform the dynamic analysis of the two-story building. The proposed fiber-based shear wall model with bolted connection was modified and improved for the development of a two-story building model. The gusset plate as a beam element on the previous version of models was replaced by a zero-length element representing the joint system. The property of the joint system is determined by the proposed analytical formula for the capacity of bolted joints in precast concrete members. Also, the contact spring elements were provided at the critical regions instead of at equal intervals which makes large modeling convenient. The calculated period and displacement response from the dynamic analysis of the proposed model for precast shear wall building with bolted connections were in good agreement with the experimentally observed shake table test results.

With the applicant’s Ph.D. thesis work, THREE peer-reviewed SCI-indexed journal papers have been published about the contents of the experimental study and numerical models for the bolted connection in a precast concrete structure. After his phd study, the applicant mainly focuses on the research about machine learning application in civil engineering, and has published a peer reviewed SCI-indexed journal paper on the convolutional neural network models.v

Achievement

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