为提高大跨度悬索桥基准索股的施工精度,基于悬链线理论提出2种调索方法。一是根据控制点的里程和标高,计算调整基准索股的总无应力长度及对应主塔偏位和施工温度的跨中点理论标高,然后将该跨索股的理论无应力长度转换成该跨调整端索鞍处的有应力长度,即索长调整量的精确解,该方法由于考虑主塔偏位、基准索股的实际跨径和温度等的影响,计算精度高。二是基于悬链线线形方程推导出的中、边跨悬链线简化调索公式。将上述2种方法及传统的抛物线调索公式法应用于珠江黄埔大桥的基准索股的调索计算中,结果表明:对于中跨,悬链线简化调索公式的计算精度高于传统的抛物线调索公式,两者相差约3%;对于边跨,两者精度相差不大;两者相对于索长调整量精确计算法的误差均不超过5%,均可应用于实桥的调索分析。应用本文提出的2种方法进行珠江黄埔大桥基准索股的施工监控,最终取得了理想线形,验证了这2种方法的正确性。
Two methods for strand adjustment were proposed based on the catenary theory to improve the construction accuracy of the datum strand of long-span suspension bridge. One method was a precise method to calculate the adjustment length. With this method, when the mileage and height of the control point were measured, the total unstressed length of the datum strand in the adjustment span, and the theoretical elevation of the midspan corresponding to the deviation of the main tower under the construction tempera- ture were calculated. Then, the theoretical unstressed length of the cable strand in the span was converted into the stressed length of the cable saddle at the adjustment end of the span, which was the exact solution of cable length adjustment. This method features with high calculation accuracy because it takes the influence of such factors into account as the deviation of the main tower, the practical span of the datum strand and the temperature variations. The other method was to deduce the simplified catenary cable adjustment formulas based on the catenary linetype equation. The two methods were used in the datum strand adjustment calculation of Huangpu Bridge over Zhujiang River, with the traditional parabola adjustment formulas. The result shows that, for mid span, the simplified catenary adjustment formulas present a higher accuracy than the conventional parabola formulas, with a 3% relative difference. For side span, the two lead to almost the same precision. The errors of the two kinds of adjustment formulas are less than 5%, comparing with the precise method for calculating the cable length adjustment. So, both can be used in strand adjustment analysis of actual bridge construction. The two methods presented above were used in the datum strand construction monitoring of Huangpu Bridge over Zhujiang River. Ideal linetype of the monitoring data is obtained, which validates the correctness of the two methods.