悬索桥基准索股定位与调整方法研究

悬索桥基准索股线形随着索股跨度、温度及两端高差变化而变化,为实现悬索桥基准索股现场的快速定位与调整,研究一套高效、实用的基准索股线形施工控制计算方法。通过理论推导编制了考虑索鞍切点变化的索股线形计算程序,建立了基于悬链线理论的索股跨中标高影响公式和调索公式。以某悬索桥为工程背景,进行参数分析,得到索股跨中标高随索股跨度、温度、两端高差变化的影响公式,与传统的抛物线、悬链线公式计算结果进行对比分析,结果表明:考虑索鞍切点变化的索股线形计算程序的计算结果与设计结果吻合较好,误差为毫米级,具有较高的精度。与传统抛物线、悬链线公式相比,考虑切点位置变化的索股跨中标高影响系数随着影响因素的变化而变化,可近似为斜直线。索股跨中标高对温度和索股两端间距的变化比较敏感,影响系数在2左右,施工中应对桥塔偏位和温度进行严格的监测,必要时采取相应调整措施。无论索股跨度、温度及两端高差单独发生任意变化,还是发生任意组合变化,该影响公式和调索公式都能保证一定的精度,误差不超过0.2%,而悬链线公式最大误差为0.81%,抛物线公式最大误差达到8%,此时已经不能满足工程精度的要求。

Shear resistance performance of steel-concrete-steel composite shear wall

For a deeper understanding of the shear resistance performance of the steel-concrete-steel composite shear wall, the main influence factors such as the thicknesses of the steel plates and the concrete, the strength grades of the concrete and the span-depth ratios of the composite wall, which have impacts on the shear resistance performance of the composite shear wail, are analyzed by the numerical simulation method. Meanwhile, the simplified calculation formulae of the initial elastic lateral-resisting stiffness and the shear bearing capacity of the composite shear wall are also proposed. The research shows that with the increase in the thicknesses of the steel plates and the concrete and the increase in the strength grades of the concrete, the shear performance of the shear wall improves obviously; the span-depth ratios of the composite wall have a significant effect on the initial elastic lateral- resisting stiffness, but a small effect on the shear bearing capacity. Comparing the results of the simplified calculation formulae with those of the nonlinear finite element method, it is obvious that the presented formulae are reasonable and meet the real force state of the structure. These conclusions can serve as a preliminary design reference for the steel-concrete- steel composite shear wall.

Damage Identification in Simply Supported Bridge Based on Rotational-Angle Influence Lines Method

To locate and quantify local damage in a simply supported bridge, in this study, we derived a rotational-angle influence line equation of a simply supported beam model with local damage. Using the diagram multiplication method, we introduce an analytical formula for a novel damage-identification indicator, namely the diff erence of rotational-angle influence linescurvature(DRAIL-C). If the initial stiff ness of the simply supported beam is known, the analytical formula can be effectively used to determine the extent of damage under certain circumstances. We determined the effectiveness and anti-noise performance of this new damage-identification method using numerical examples of a simply supported beam, a simply supported hollow-slab bridge, and a simply supported truss bridge. The results show that the DRAIL-C is directly proportional to the moving concentrated load and inversely proportional to the distance between the bridge support and the concentrated load and the distance between the damaged truss girder and the angle measuring points. The DRAIL-C indicator is more sensitive to the damage in a steel-truss-bridge bottom chord than it is to the other elements.

Rules of distribution in a plastic zone of rocks surrounding a roadway affected by tectonic stress

In order to study the rules of distribution in a plastic zone of rocks, surrounding a roadway, affected by tectonic stress, we first analyzed the mechanics of a roadway affected by tectonic stress and derived a theoretical formula for the plastic zone of rocks surrounding a roadway. We also analyzed the distribution characteristics of the plastic zone under different levels of tectonic stress, vertical pressure, cohesion and friction angle of the surrounding rock. Secondly, we used numerical simulation to analyze the range and shape features of the plastic zone of rocks surrounding the roadway, given different tectonic stress levels. Finally we used a rock drilling detector to carry out field measurements on the broken state of rock surrounding the roadway at the –700 substation and channels in the Xinzhuang mine of the Shenhuo mining area. Given the measured ground stress, we analyzed the relationship between tectonic stress and the distribution of this plastic zone. Our results show that the range of the plastic zone at the top and bottom of the roadway increases with an increase in tectonic stress and this increase is especially obvious at the roadway corner.