STUDY ON WIND FORCE COEFFICIENTS FOR DESIGN OF MEMBRANEIN HP-TYPE TENSILE MEMBRANE STRUCTURES -Study Based on Maximum Load Effect on Membrane Surface-

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Publication year 2025
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Title STUDY ON WIND FORCE COEFFICIENTS FOR DESIGN OF MEMBRANEIN HP-TYPE TENSILE MEMBRANE STRUCTURES -Study Based on Maximum Load Effect on Membrane Surface-
Author Konomi Tada (Tomoe Corporation),Naoya Miyasato (Nihon University),Akira Okada (Nihon University),Akira Oshiumi (Nihon University),Akira Oshiumi (Nihon University)
Summary 　In this study, wind load coefficient for membrane design (Cfe) is proposed to appropriately evaluate the maximum load effect on membrane surface deformation and stress in HP-type tensile membrane structures. Conventional wind coefficients for structural frames could not adequately capture membrane surface responses, leaving issues in wind-resistant design. Therefore, this study derived an equivalent static wind coefficient distribution (Cf_LRC) through wind tunnel experiments and time-history response analysis. Based on this, a region-divided Cfe was established, and its applicability was verified through numerical analysis.
　The June 2024 notification revision increased design freedom for membrane structures, enabling the design of large-scale HP-type tensile membrane structures. HP-type structures are rational membrane designs utilizing form resistance, with numerous examples overseas. However, in Japan, examples were limited due to factors like the lack of established wind load coefficients. Since membrane materials are lightweight, wind pressure design is critical, especially for complex shapes like HP-type structures, requiring an understanding of wind pressure characteristics from the early design stages.
　This study modeled an HP-type tensioned membrane structure with a 15m×15m rectangular plan at three sag/span ratios, conducting wind tunnel tests and time-history response analysis. A tendency for downward deflection at 0° wind direction (suspension direction) and upward deflection at 90° (arch direction) was confirmed, with wind load coefficients increasing with larger sag/span ratios.
Response analysis showed membrane stress peaked at wind direction 0°, while at 90°, stress partially increased on the windward side.
　To evaluate maximum load effects, the equivalent static wind coefficient distribution (Cf_LRC) was calculated using the LRC method, focusing on vertical reactions at leeward columns. The obtained Cf_LRC was divided into zones, and membrane design wind coefficients Cfe (downwind: Cfed, upwind: Cfeu) were established. Cfe showed a generally linear relationship with the sag/span ratio, suggesting it can be calculated via interpolation.
　Numerical analysis confirmed that Cf_LRC effectively evaluates the maximum value of the membrane surface's maximum load effect.
However, evaluating the maximum load effect at all points is difficult. Cfe is effective for simplified evaluation; while it provides a good estimate in the downwind direction, it tends to slightly underestimate in the upwind direction, necessitating consideration of a safety factor.