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*Steel Pier with circular section on The Metropolitan Expressway [#m7887210] *首都高速道路の円形断面鋼製橋脚 [#m7887210] **1.Field of application [#i46ac147] >Steel pier at The 5th line on The Metropolitan Expressway, Japan.&br; >首都高速道路5号線の鋼製橋脚 **2.Circumstances of Repair [#j8c7ddc6] >Fatigue cracks were found in welded joints ,which were the corner of the steel bridge pier,in 2003 after 35 years of service . >供用開始から35年経過した2003年、鋼製橋脚隅角部の溶接継手に疲労き裂が見つかった。 **3.Types of structure [#o5156f4d] >Front view of the steel pier is shown in [[Fig.1>#fig1]]. >[[図.1>#fig1]]に鋼製橋脚の正面図を示す。 -Structural steel : SM50B,SM58 &br; -使用鋼材：SM50B、SM58 &br; CENTER:&aname(fig1);&attachref(./steel_pier_circular_1.jpg,30%);&br; &br; CENTER:Fig.1 Front of the steel piers &br; CENTER:図.1 正面図 &br; **4.Details of loading [#z3320972] >Fluctuating loads due to highway live load. >活荷重 **5.Description of damage [#w809f60e] >Many cracks which lengths were more than 30mm were observed.The location of the cracks is shown in [[Fig.2>#fig2]].The detail of the crack is shown in [[Fig.3>#fig3]]. &br; >長さが30mmを超える疲労き裂が数多く見つかった。[[図.2>#fig2]]に疲労き裂の位置を示す。[[図.3>#fig3]]にき裂の詳細を示す。 &br; CENTER:&aname(fig2);&attachref(./steel_pier_circular_2.jpg,10%);&br; &br; CENTER:Fig.2 The location of the cracks &br; CENTER:図.2 疲労き裂の位置 &br; CENTER:&aname(fig3);&attachref(./steel_pier_circular_3.jpg,10%);&br; &br; CENTER:Fig.3 The detail of the crack &br; CENTER:図.3 疲労き裂の詳細 &br; >Cause of fatigue cracks was as follows: >疲労き裂の原因は次のとおりである。 -The cause of the cracks was the lack of fusions in the welded joints which were at the corner of the steel pier([[Fig.4>#fig4]]). &br; -鋼製橋脚隅角部の溶接継手における溶け込み不足 &br; CENTER:&aname(fig4);&attachref(./steel_pier_circular_4.jpg,20%);&br; &br; CENTER:Fig.4 Lack of fusion in the welded joints. &br; CENTER:図.4 溶接部の溶け込み不足 &br; **6.Repair method applied [#xcafab0b] >The principles of the repair were as follows. >補修の方針は以下のとおりである。 -Halving the fluctuating stress by installing a reinforcement member. -Preventing the development of the cracks by cutting. -補強部材を設置することで発生応力度を半減させる。 -カッティングにより、き裂の進展を抑制する。 >The reinforcement member is shown in [[Fig.5>#fig5]]. And the circumstances of cutting is shown in [[Fig.6>#fig6]]. >[[図.5>#fig5]]に補強部材を示す。また、カッティングの状況を [[図.6>#fig6]]に示す. &br; &br; CENTER:&aname(fig5);&attachref(./steel_pier_circular_5.jpg,30%);&br; &br; CENTER:Fig.5 Reinforcement member. &br; CENTER:図.5 補強部材 &br; CENTER:&aname(fig6);&attachref(./steel_pier_circular_6.jpg,20%);&br; &br; CENTER:Fig.6 Circumstanses of cutting &br; CENTER:図.6 カッティングの状況 &br; **Reference [#g9d0ce04] >Kurokawa et al,A repair case of fatigue damage which occurred at a corner of a steel pier with circular section ,'''Prc.of Annual Conferenece of JSCE''',vol.58,2003.(In Japanese)
