Abstract of Special Research Report (SRR-No.37)
National Institute of Occupational Safety and Health, Japan
Study on Instability of Bridge and Development of Safety Construction Technique during Bridge Erection
: In this project study, to prevent collapse accidents and falling accidents during bridge erection, the instability of jack and supporting stand, the safety of bridge girder erection work methods, wire grip management technique used in cable erection, and instability factors on suspended scaffolds are examined experimentally and analytically. From the results of these studies, the risk evaluation methods during the bridge erection are examined for preventing the collapse and falling accidents.
Study on Stability of Bridge Girder in Launching Method
|Seiji TAKANASHI and Katsutoshi OHDO|
: The launching method is one of the construction method used to erect a bridge girder. In this method, a bridge girder is placed on a launching apparatus, and it is moved into a prescribed position by the launching apparatus or other equipment. The advantages of this method are that a large-sized crane is not required, and a bridge girder can be installed in a short time. The disadvantages of this method are that a working area is required for the adjacent to the construction site, and also that a large patch load occur onto the bridge girder during the launching operation. Since this load disappears when the bridge is completed, it may not be taken into consideration at the design stage. If a bridge girder's web plate is damaged due to this load, the stability of the bridge girder may be lost, and it may collapse. Therefore, in this study a reproduction test was carried out using a launching apparatus that is commonly used in construction sites and a full-scale bridge girder model.
Experimental Study on Horizontal Stability of Saddle
|Katsutoshi OHDO, Seiji TAKANASHI and Hiroki TAKAHASHI|
: When constructing or reconstructing bridge girders, a temporary structure called a saddle is often used as a support. The saddle is composed of many stacked steel H-beams, each with a width and height of 150 mm, in a double cross. The load on the saddle comprises the vertical load due to the weight of the bridge girders, and the horizontal load due to the launching erection. Although the strength against vertical loads is considered when designing the saddles, the horizontal stability against the horizontal load has largely been judged based on the experience of the construction workers.
Influence of Residual Deformation on Stability of Saddle in Bridge Construction
|Hiroki TAKAHASHI, Katsutoshi OHDO, Seiji TAKANASHI|
: In the construction of a bridge girder, a temporary "saddle" structure often used. The saddle is composed of multiple stacked steel H-beams, each having a width and height of 150mm. The vertical load acting on the saddle is due to the weight of the bridge girders. The saddle member might become deformed by this load. After removing the load, the deformation might remain. This deformation is known as residual deformation. The slightly deformed saddle members are used repeatedly as well. However, there is no management standards for the saddle. In this study, the influence of residual deformation on the stability of the saddle is examined and a management standard for the saddle is proposed.
Investigation of Wire Rope Grip Usage Standard
|Tetsuya SASAKI, Takashi HONDA, Kenta YAMAGIWA|
: The cable erection method is used in the construction of steel bridge. Even though this method is very versatile and used only as a last resort to build an arch-type bridge over a deep valley,the nature of the method requires the use of many wire ropes and each one must be terminated using wire rope grips. One of the major problems with this method is the risk of wire rope slipping through the wire rope grips in the case of improper fitting. All grips are installed according to the wire rope grip usage standard; nevertheless, accidents due to wire rope slipping through the grips frequently occurs at bridge construction sites employing the cable erection method. This fact suggests that the existing usage standard for wire rope grips may be insufficient.
Strength of Roughly Assembled Suspended Scaffolds
: Suspended scaffolds supported by many chains are generally used at bridge construction sites for work such as painting, assembling of form panels, etc., which involve only lightweight materials. However, after the Hanshin-Awaji earthquake in 1996, numerous bridge reinforcement projects were implemented, involving the handling of 10 kN of heavy-load materials on suspended scaffolds.