The purline is often designed as a simple beam, and only it ′ s strength needs to be calculated, if the roof panel can prevent it ′ s lateral buckling and torsion.
檩条一般采用简支梁,假定屋面板能阻止其侧向失稳和扭转,则只计算其强度。
auger especially designed thick purline;
专为厚檩条设计的钻头;
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