Niloufar Khoshbakht

PhD Candidate, Sustainable Building Systems

Computational Analysis of LVB connections

Niloufar is a PhD student in the Environmental Conservation Department at UMass majoring in building construction systems. She received her M.S. from university of Tehran department of Agricultural Machinery Engineering. With a previous background on experimental-computational contact stress analysis of bolted joints, Niloufar’s current research area is LVB (Laminated Veneered Bamboo) connections. Her work focuses on the computational analysis of laminated Moso bamboo dowel joints.

Project: Computational Modeling of Laminated Veneer Bamboo (LVB) Dowel Connections 

Dissertation Committee:
Chair: P.L. Clouston
Members: S.R. Arwade & A.C. Schreyer

Project Description:
Laminated veneer bamboo (LVB) is a sustainable building material that has been gaining interest in the construction industry of late. As a relatively new product, little is known about its connection performance, specifically, its failure behavior in dowel type joints and possible similarities it may have to engineered wood products in terms of failure mechanisms. Research is needed to aid in the understanding of LVB dowel connection failure behavior and to quantify the failure mechanism and key factors associated with LVB dowel connection strength. Modeling, as conducted in this research, is a valuable tool to help devise safe standards and formulations for future LVB product adoption, design, and implementation.

In this work, a 2D elastic plane strain Finite Element model is described to investigate dowel bearing failure when loaded parallel-to-grain. The model was calibrated and validated through comparison with experimental results. Frictional contact was incorporated in the model and the coefficient of friction was proved to be a key factor in finding the maximum shear stress location. According to both the FEM and experimental results, the high shear stress-to-strength ratio is the major cause of failure when the dowel is loaded parallel-to-grain. Moreover, tensile stress perpendicular-to-grain is observed to be an influential secondary cause of failure.

The intention of this work is to do a quantitative comparison between the two test methods offered by ASTM5764 standard (full-hole and half hole specimen) for timber products iiand see if the same condition holds for LVB and other similar wood engineering products. Also, a study will be conducted to investigate effectiveness of Hankinson formula for LVB dowel joints and subsequently will devise a formulation that calculates bearing strength at different angles to the grain for LVB material. This research will contribute to safer design and implementation of LVB bolted connections and development of standard test method for wood-composite materials including LVB.