动载下饱和重塑黄土的骨干曲线变化研究

针对饱和重塑黄土进行了一系列等向固结和偏压固结下的排水与不排水动三轴试验,分析了饱和重塑黄土的动力性质、骨干曲线模型及其影响因素。基于动三轴试验结果,探讨了在考虑累积塑性应变影响下,修正Hardin-Drnevich模型的适用性。结果表明,考虑累积塑性应变时,修正Hardin-Drnevich模型能够较好地模拟饱和重塑黄土的骨干曲线试验结果。进而分析了等向固结和偏压固结、固结围压、波形和排水条件等因素对饱和重塑黄土骨干曲线的影响,得到偏压固结和固结围压的增大使骨干曲线上移,土体强度增加,而波形对骨干曲线的影响较小;排水条件下的骨干曲线较不排水条件下的有所上移,土体强度增加。所得结论可供工程设计人员参考。

粉煤灰改良饱和黄土动力特性研究

以资源循环再利用与提高饱和黄土地基抗震性能为目的,通过对不同掺量粉煤灰改良饱和黄土进行动弹性模量-阻尼比试验,研究了动荷载作用下粉煤灰掺量对饱和改良黄土动骨干曲线的影响,同时对不同掺量粉煤灰改良饱和黄土初始动弹性模量、最大动应力幅值、动弹性模量与阻尼比进行了对比研究。研究结果表明:饱和压实素土与不同掺量粉煤灰改良饱和黄土动骨干曲线均可用双曲线模型进行描述,模型参数受粉煤灰掺量影响较大;粉煤灰的掺入可有效改善饱和黄土地基抗震性能,随粉煤灰掺量增加,不同掺量饱和改良黄土动弹性模量与阻尼比分别总体呈增大与减小趋势;考虑粉煤灰改良饱和黄土抗震性能与经济成本,提出了饱和改良黄土最佳粉煤灰掺量为20%~25%;并基于回归分析,给出了饱和改良黄土动弹性模量衰减经验公式与阻尼比增长经验公式及其拟合参数。

实验方法推估台湾地区岩石变形模量研究

为了对无法进行现场试验却又必须决定岩体的变形模量,探讨台湾地区的岩石共分沉积岩层中的砂岩、页岩、粉砂岩、砂页岩互层、泥岩等五类及变质岩层中的石英云母片岩、片麻岩、硅质片岩、绿色片岩、黑色片岩、大理岩、板岩、角闪岩、石英岩、燧岩、变质砂岩等11类岩石的变形性,利用现场孔内变形试验(ElastmeterTest)所得的参数,与室内动弹性试验(DynamicElasticModulusTest)及静弹性试验(StaticElasticModulusTest)所得的参数,整理分类以作为台湾地区地层、岩性的变形性工程参数数据库,并比较其相互间关系。最后推估得到沉积岩的变形模量及其弹性模量随着地质年代增长而有增加的趋势,而大理岩的变形模量明显高于大南澳片岩层的石英岩、石英云母片岩、片麻岩以及白冷层的板岩。

Elastic-plastic study on high building with SRC transferring story

A new type of transferring structure for steel reinforced concrete (SRC) beams is used in high building. The pushover analysis method was used to study the failure mechanism and ductility of SRC transferring structure through consulting pseudo-static test results for the structure. And, the occurrence order and position of the plastic hinge, the weak story and seismic capacity of high building with SRC transferring story were also studied through consulting shaking table test results for the high building, showing that the seismic behavior of high building with SRC transferring story is good.

Wind tunnel study on wind-induced vibration of middle pylon of Taizhou Bridge

Full aero-elastic model tests are carried out to investigate wind-induced vibration of middle steel pylon of Taizhou Bridge. Model of the pylon under different construction periods is tested in both uniform and turbulent flow field. And the yaw angle of wind changes from transverse to longitudinal. Through full aero-elastic model testing, wind-induced vibration is checked, which includes vortex resonance, buffeting and galloping. Vortex resonance is observed and further studies are carried out by changing damping ratio. Based on wind tunnel testing results, wind-resistance of middle pylon is evaluated and some suggestions are given for middle pylon's construction.

Static aeroelastic analysis of a high-aspect-ratio wing based on wind-tunnel experimental aerodynamic forces

The aeroelastic responses of a high-aspect-ratio wing are investigated based on nonlinear experimental aerodynamic forces. The influences of nonlinear experimental aerodynamic forces and dynamic pressures on the wing loads are studied in the longitudinal and lateral maneuver states. The flight loads of the wing fixed at the root are calculated at different angles of attack. The aileron efficiency with respect to the dynamic pressures and aileron deflections are also studied. The results indicate that the flight loads of the wings vary nonlinearly with the angle of attack and dynamic pressure. Due to the high-lift aerofoil, elastic components are a large portion of the wing loads, especially for small angles of attack and high dynamic pressure condi-tions. The aileron efficiency is significantly affected by aileron deflections, dynamic pressures and angles of attack when the nonlinear experimental aerodynamic forces are used for calculation. In states with high dynamic pressures and large aileron deflections, aileron reversal can occur. The aileron deflection and angle of attack have a nonlinear effect on the aileron efficiency. An efficient method for analyzing the flight loads and structural design of high-aspect-ratio wings is derived in this study, and the analysis can provide insight into the distribution of flight loads for high-aspect-ratio wings.

Studies on aeroservoelasticity semi-physical simulation test for missiles

Missiles may be damaged when aeroservoelastic problem occurs,which is caused by the interaction of structure flexibility and flight control system.Because of the limit of wind tunnel test condition,numerical methods are mostly used in previous aeroservoelastic studies.However,series of assumptions and simplification on structures,aerodynamics and flight control systems are unavoidably introduced,and various nonlinear factors are also ignored,therefore,they result in considerable errors.A novel method called aeroservoelasticity semi-physical simulation test is proposed in this paper,which takes the flexible missile with control system as the test object.Vibration signals at several locations of the missile are measured by accelerometers,then corresponding unsteady aerodynamics is computed based on the fact that airflow at high Mach is nearly quasi-steady,and finally unsteady aerodynamics is exerted simultaneously by shakers at certain locations of the missile.The aeroservoelasticity semi-physical simulation test system can be constructed after the control system is closed.Open loop transfer function test and closed loop stability test are carried out in sequence.The test principle and method proposed in this paper are verified by the concordance between the results of numerical simulation and experiment.