Experimental research of steel-concrete joint bearing law of steel-concrete rock-socketed piles
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摘要: 钢管混凝土嵌岩桩是深水和浅覆盖层环境下的新型深基础型式,在内河深水码头建设中应用广泛。针对船舶撞击力、波浪力及水流力等周期性水平荷载作用下内河港口钢管混凝土嵌岩桩钢-混凝土联合承载特性,制作了3根1∶7.3的大比尺钢管混凝土嵌岩桩模型,沿桩身不同高度在钢管外侧、对应内侧混凝土块及内置受力钢筋上分别布置应变测点,以18.0、22.5和27.0 kN为循环幅值,开展钢管混凝土嵌岩桩钢-混凝土联合承载规律试验。结果表明:桩身钢-混凝土应变均包括线性增长、平稳波动、剧烈震动和急剧下降4个阶段,各阶段占疲劳寿命8.66%、79.66%、6.06%和5.62%;同一桩身截面外侧钢管应变与内侧对应混凝土应变差异较大,最大超过混凝土应变的80%,而内置钢筋与混凝土始终保持应变协同,最大应变差不超过混凝土应变的20%;在弯矩较小的桩顶处,桩身弯矩主要由内侧混凝土承担,占比超过70%,沿桩身往下,钢管承担的截面弯矩比逐渐增大,在桩身底部,两者弯矩占比近似相等,钢管与混凝土受弯同步,在同一桩身截面处,循环幅值越大,两者越早达到受弯协同状态。Abstract: Concrete-filled steel tube rock-socketed piles are a new type of deep foundation in deep water and shallow overburden environments, and are widely used in the construction of deep water wharves in inland rivers. In view of the combined bearing characteristics of steel-concrete for concrete-filled steel-filled piles under cyclical horizontal loads such as ship impact force, wave force and current force, three models of large-scale concrete-filled steel tube rock-socketed piles of 1∶7.3 were made. At different heights of the pile body, strain measuring points were arranged on the outer side of the steel tube, the corresponding inner concrete block and the built-in stressed steel bars, with 18.0, 22.5 and 27.0 kN as the cyclic amplitude, to develop the steel-concrete joint bearing law of the concrete-filled steel tube rock-socketed piles test. The results show that the steel-concrete strain of the pile body satisfies the four stages of linear growth, steady fluctuation, severe vibration and sharp decline, and each stage accounts for 8.66%, 79.66%, 6.06% and 5.62% of the fatigue life; the strain of steel pipe on that outside the same pile section is quite different from that of concrete on the inside, and the maximum is more than 80% of the concrete strain. The built-in steel bars and the concrete always maintain strain coordination, and the maximum strain difference does not exceed 20% of the concrete strain; at the top of the pile with a small bending moment, the bending moment of pile body is mainly borne by inner concrete, which accounts for more than 70%. Along the pile, the ratio of the section bending moment borne by the steel pipe gradually increases. At the bottom of the pile, the proportion of the two bending moments is approximately equal. The steel pipe and the concrete are subjected to bending. Simultaneously, at the same pile section, the greater the cyclic amplitude, the earlier the two will reach the bending coordination state.
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表 1 原型与模型对照
Table 1. Comparison between prototype and model
项目 钢管
材料钢管外径/
mm钢管壁厚/
mm桩身
材料桩身直径/
mm地基
材料主筋 钢管内壁钢筋 箍筋 根数 直径/mm 根数 直径/mm 间距/mm 直径/mm 原型 Q235A 2 200 16 C30 2 168 砂泥岩 34 25 30 25 125 10 模型 Q235A 300 2 C30 296 C15 8 8 8 8 不均 4 表 2 不同循环荷载幅值下桩身应变的发展阶段划分
Table 2. Development stage division table of pile body strain under different cyclic load amplitudes
发展阶段 循环次数/次 循环荷载幅值18 kN 循环荷载幅值22.5 kN 循环荷载幅值27 kN 线性增长 1~9 500 1~1 000 1~700 平稳波动 9 500~55 000 1 000~10 200 700~7 800 剧烈震动 55 000~68 000 10 200~10 900 - 急速下降 — 10 900~11 550 7 800~7 900 -
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