CASE STUDY: Taiyuan Botanical Garden Lucas Epp, P.E., P.Eng. The Taiyuan Botanical Garden, located in the capital of China’s Shanxi province, features an artificial landscape that combines nature and architecture in a unique destination for local and international visitors. The Greenhouse is the centerpiece, featuring three biodomes that enclose flora from tropical, desert and aquatic biomes. The dome structures range 140–300 ft. in diameter and 40–100 ft. in height. The largest of the three domes is believed to be the longest clear-span timber gridshell (non-triangulated) worldwide. It is also likely the largest timber gridshell to be covered entirely in doubly curved glass, adding significant challenges to the structural design, which is in a region with significant seismic hazard. All three parabolic gridshells comprise light doubly curved glulam beams, arranged in two or three crossing layers. The project pushes the boundaries of structural engineering, materiality and construction technique in a country that has little experience using timber for long-span applications. The use of a unique, optimized geodesic grid allowed minimization of doubly curved glulam, and enabled a manufacturing pace which could
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keep up with an intense Chinese construction schedule. When viewed from above, the timber structures resemble seashells, with the primary members tightly spaced on one side and fanned out across the surface of the domes, driven by a desire to optimize solar gains by creating a gradient in skin transparency. This complex arrangement means that every one of the 2,400 glulam members is unique, many of which are doubly curved. Wood facilitated this “seashell” look in a more natural way than other structural materials could. Computational design methods inside Rhino and Grasshopper were used extensively from concept design through to fabrication geometry and automatic generation of CNC machine files. This structurally optimized geometry was developed while looking at all constraints, including shipping/containerization, fabrication and pre-assembly, with kit-of-parts erection and sequencing drawings for site crews. The unique seashell aesthetic on these domes required a two-way grid. This requirement created the project’s single biggest challenge: achieving an efficient timber gridshell with elements which were moment-fixed to each
