Kenji Hirose, who designed The “SH series” prefab houses, developed a three hinged ramen structure system named “Type 33” in SH-30 in 1960. That was the representative system of the series and aimed to eliminate structural braces that existed in previous works and to promote further industrialization, and over 20 houses were built by the system. However, there were some other systems that also eliminated structural braces before and after “Type 33”. This study analyzed these systems systematically in chronological order and re-evaluate them by deciphering existing old documents.

 As a result, the following points were pointed out in this study.

 1) At first, a ramen frame structure system with fixed column bases and pin-jointed beams was tried so as to eliminate structural braces. But it was very difficult to fix these bases on site with high accuracy because it depended on the construction accuracy of concrete pouring.

 2) At second, “type33” ie a unique 3 hinged ramen frame structure system was developed. It was very flexible in planning and over 20 houses were built by the system. However, it was unavoidable that many pin-jointed columns stood in the house.

 3) At third, “type43” ie another type of 3 hinged ramen frame structure system was developed. Compared with “type 33”, manufacturability and transportation efficiency of main structural components were improved and very few columns stood in the house. But it was unavoidable to use “square division” room planning way.

 4) At fourth, “type52” ie yet another new type of 3 hinged ramen frame structure system was developed. It eliminated any columns in the house, but main structural components were bigger than “type 33” and “type 43” and thus manufacturability and transportation efficiency was deteriorated again.

 As above, various prototypes of ramen frame structure system was developed by Kenji Hirose in the SH series, however his interest shifted to “Space-unit construction” after that.