Design Methods and Technological Strategies of Umbrella Bamboo Structures

HUANG Yuming; ZHAO Yamin; XIN Shanchao

doi:10.3969/j.issn.1000-0232.2025.04.004

Abstract：Bamboo,a renewable green building material,has the advantages of rapid growth,high strength,and plasticity.The umbrella-shaped structure is a common bamboo structure because it can fully express the natural aesthetics of bamboo.Two types of umbrella-shaped bamboo structures,namely the"cantilevered type"and"supported type",were extracted through graphical analysis,structural performance analysis,design derivation,and other methods.(1)Cantilevered type.This is in the shape of an inverted cone,and its structure has the following characteristics:the stress of the component is mainly concentrated at the node on the top of the bamboo umbrella,the annular component weakens the stress of the cantilever arch,and the deformation of the structure gradually increases from the bottom to the top,limiting the cantilever span.The structural strategy has two methods:truss type and branch type.The truss type uses triangular or square lattice units to form an umbrella-shaped structure,which is suitable for smaller-scale bamboo umbrellas.The branch type forms a complex umbrella-shaped structure by combining straight columns and curved arches,which is suitable for larger-scale bamboo umbrellas.The design of key nodes includes mortise-tenon connections and hemp-rope binding to ensure the stable connection of multiple types and multi-directional rods.Owing to the limited bearing capacity of a single cantilever bamboo umbrella,it is necessary to improve the structural stability through cluster combination,which is suitable for smaller-scale buildings.Clustered umbrella groups usually have proportional modules,and a modular system can be introduced into the design and construction process.(2)Supported type.This is shaped like a straw hat,and its structural characteristics are introduced as follows:the load is transferred from the roof to the ring beam,and then to the central and the surrounding columns.Furthermore,the boundary can be grounded by bamboo beams or additional side columns,which affects the vertical height and plane scale of the structure.The grouping strategy includes single and clustered approaches.The single structure has a smaller span and scale with the roof made of lightweight materials and supported at the boundaries.The clustered structure generates multi-curvature surfaces or retains conical shapes through topological aggregation or linear splicing.Key structural designs include bolt/bamboo nail anchoring and mortise-tenon joints to ensure the stability and safety of the structure.In combination with the mechanical properties and morphological characteristics of bamboo,it optimizes the structure and transforms space,with a relatively flexible scale.It can be realized through independent or clustered construction strategies,which are suitable for large-scale buildings.In areas with low technology availability or incomplete regulations,structural redundancy and architectural differences need to be considered to ensure the safety and stability of the building.This study provides important theoretical and practical references for the application of bamboo to contemporary architecture,which not only promotes the development of the forestry economy,but also forms a unique bamboo structure culture.