本文指出:由于塑料大棚的钢拱架采取冷弯成形工艺,从而一方面使拱架在承受载荷之前就具有自应力;另一方面使拱架材料的屈服极限发生变化,最后导致强度发生严重的畸形:负弯矩处过份安全,正弯矩处强度则严重不足。这一畸形必须设法克服。 This article points out: Because the steel arch of the plastic greenhouse adopts the cold bending forming process, on the one hand, the arches have self stress before bearing the load; on the other hand, the yield limit of the arch material changes, and finally the strength is severe. Deformity: excessive safety at negative bending moments, severely insufficient at positive bending moments. This deformity must try to overcome.