:Suspended scaffolds supported by a lot of chains have been usually used at the bridge construction site. And it was mainly used for the painting works, assembling work of form panel, and so on. Therefore, only the light weight materials had been mainly handled on the scaffolds.
    But many reinforcement works for bridge structure have been carried out since Hanshin-Awaji earthquake in 1996. At the reinforcement work, over the 10 KN of the heavy load materials are handled under the suspended scaffolds. However, the safety design method of the suspended scaffolds that used for the supporting the heavy load materials has not been confirmed.
    Therefore, there is an urgent need to develop the countermeasure for the heavy load materials. As a matter of fact, the accidents occurred that the heavy load material dropped from the suspended scaffolds to the express highway and it crashed into some cars. At the accident, the chain of the suspended scaffolds fractures due to the heavy load. The cause of the accident is the mistakes of the use method of the chain.
    This report is to investigate the strength and the suitable use method of the chain by experimental studies that it is a component part of the suspended scaffolds. Especially, the relationship between the deference of the relative chain and the increment load was investigated.
    The major findings obtained in this study can be summarized as follows:
  1) The increment load of the suspended scaffolds is roughly depending on the additional number of the chain. However, the maximum load of the suspended scaffolds with the small length of the chain can not be estimated in proportion to the number of the chain.
  2) The loads of the multiple chains especially have great disparity at the elastic area. This disparity occurs depend on the difference of the relative chain length.
  3) The suspended scaffolds always must be used in the elastic area. Hence, the design load values can not estimate in proportion to the number of the chains.
  4) The chain length needs to be equalized for the fulfillment of the safe suspended scaffolds for supporting the heavy load parts.