A Study on the Strengthening of ASR Damaged Concrete Piers Using Prestressing Steel Wires

针对ASR损伤的钢筋混凝土桥墩，提出了一种新的预应力钢丝加固方法——PC约束加固法。制备了直径为300 mm、高为900 mm的钢筋混凝土柱，研究了混凝土柱周围预应力对碱-硅反应引起的混凝土裂缝的约束作用以及对损伤混凝土柱承载能力和延性的改善作用。试验结果表明，在混凝土柱周围施加预应力可以有效地抑制ASR引起的裂缝，减小混凝土的膨胀。结果表明，采用预应力混凝土约束法后，损伤钢筋混凝土柱的强度和延性均有较大提高。在室内试验的基础上，分别于1997年和1998年成功地将PC约束法应用于石川县诺藤半岛丰川桥和熊木川桥ASR损伤RC桥墩的加固。对东川大桥桥墩采用PC约束法加固后混凝土应力应变随时间的变化进行了监测。

A new strengthening method with prestressing steel wires, which is named the PC confined method, has been developed especially for ASR damaged RC piers. Reinforced concrete columns, 300 mm in diameter and 900 mm high, were prepared in order to examine the effects of the prestressing force around the concrete column on the confinement of the cracks of concrete due to alkali-silica reaction and on the improvement of load-carrying capacity and ductility of damaged concrete columns.From the experimental results, it was concluded that the prestressing force given around the concrete column could effectively confine the cracks due to ASR and decrease the expansion of concrete. Thus, it was found that both the strength and ductility of damaged RC column was much improved by PC confined method. Based on the results of the laboratory test, the PC confined method was successfully adopted in the strengthening for ASR damaged RC piers of the Toyokawa bridge and the Kumakigawa bridge in Noto peninsula in Ishikawa prefecture in 1997 and 1998, respectively. The measurements on changes with time in the stress and strain of concrete in the piers of the Toyokawa bridge after strengthening by PC confined method are now monitored.