独塔部分地锚式PC斜拉桥经济及设计参数研究

为得到独塔部分地锚式PC斜拉桥的合理设计参数范围,通过对拉索、主塔、锚碇、主梁的材料用量和造价进行计算,建立了全桥总造价及单位桥长造价公式,据此开展了独塔部分地锚式PC斜拉桥合理背索自锚比例、锚碇主跨长度比、边主跨比及塔跨比的研究,并与其他斜拉桥型进行了对比。结果表明:考虑全桥跨越能力时,背索自锚比例宜取0.336~0.487范围内的大值,边主跨比宜取0.487~0.544范围内的小值,考虑单跨跨越能力时反之;当主跨跨度较小时,可取适当小于依据上原则的取值,当主跨跨度较大时反之;塔跨比宜取0.372左右,对应的主跨边索倾角为20.4°左右,跨径较小时取较大值,跨径较大时取较小值,与其他斜拉桥型无明显区别。独塔部分地锚式PC斜拉桥仅在边跨自锚段空间受地形条件限制时经济性能优于独塔常规斜拉桥,在常规地形并无优势。

Cost and design parameter of partially earth-anchored PCcable-stayed bridge with single pylon

In order to obtain the reasonable design parameter range of a partially earth-anchored PC cable-stayed bridge with a single pylon, the formulas for the total bridge cost and the cost per unit length of the bridge were obtained through computation of the material dosage and cost of cables, the main pylon, the anchor, and the girder. According to these formulas, the reasonable ratio of the self-anchored length of the side span to the length of the main span, the ratio of the anchor length to the main span length, the side-to-main span ratio, and the ratio of the pylon height to the main span length of the partially earth-anchored PC cable-stayed bridge with a single pylon were studied, and they were compared with those of other cable-stayed bridges. The results show that, considering the spanning capacity of the whole bridge, larger values in the range of 0. 336 to 0. 487 should be used as the ratio of the self-anchored length of the side span to the length of the main span, and lower values in the range of 0. 487 to 0. 544 should be used as the side-to-main span ratio. Considering the spanning capacity of the single span, the opposite is the case. Values to some extent lower than those mentioned above are allowed when the main span is smaller, and vice versa. The ratio of the pylon height to the main span length should have a value of about 0. 372, and the corresponding main span side-cable inclination is about 20. 4°. Larger values can be used when the span is lower, as with other types of cable-stayed bridges. The partially earth-anchored PC cable-stayed bridge with a single pylon performs better economically than a common cable-stayed bridge with a single pylon only when the self-anchored space of the side span is limited by terrain conditions. It has no advantage in common terrain conditions.