The monopile-friction wheel composite foundation is an innovative offshore wind turbines (OWTs) foundation type for its good bearing properties and anti-erosion advantages. The local scouring is a non-negligible challenge by moving surrounding soils away till even some engineering disasters. To explore this kind of unfavorable effects, we model the response of scouring to the bearing capacity of the composite foundation by means of laboratory flume tests. Furthermore, the influence of different loading sequences (i.e., T→H or H→T) is considered, and the failure envelopes are also obtained. On this basis, a 3D finite element model is established to investigate the impact of key scouring parameters and different loading point heights on the bearing capacity. The conclusions are as follows: local scouring can significantly reduce the bearing capacity; the scouring depth has the most significant effect, followed successively by the scouring angle and extent; compared with pure horizontal foundations, the ultimate torsional bearing capacity of the foundations under the combined T→H loading sequence decreases by about 1.95%–11.1%, while the horizontal bearing capacity under the combined H→T loading sequence decreases by about 0.82%–1% compared with pure torsional foundations; the loading point height has noticeable effects on the lateral resistance for the composite foundation.
Abstract Ganluo County is located in the southwestern part of Sichuan Province in China. It has strong geological tectonic movement, strong earthquake affected area and frequent debris flow disasters. There are two huge debris flows occurred in Zile Valley of Ganluo County in 1987 and 2019, a large amount of debris flow deposits went down the valley, destroyed the buildings at the mouth of the valley, causing huge property damage to local residents. In this regard, based on data of field survey and UAV aerial photography, the Arcgis and Massflow software were used to invert and analyze the movement characteristics of the debris flows occurred in 1987 and 2019, and the future activity characteristics of the valley are predicted. The results show that if the debris flow breaks out in the valley again based on the existing sources, the maximum mud depth will reach to 11.9m, the flow intensity will reach to 123.37m2/s, the total volume of material flushed out is 11.18×104m3 and the accumulation fan area is 6.925×104m2. However, after adopting reasonable engineering measures, the maximum mud depth is reduced to 8.5m, the flow intensity is reduced by 52.7% to 58.32m2/s, the accumulation fan area is reduced by 80% to 1.406×104m2 and the total volume of material flushed out is reduced by 75% to 2.75×104m3. This shows that the use of retaining measures to control the debris flow in Zile Valley can achieve good results.
目前广大农村地区拥有大量不符合抗震要求的砌体结构房屋,因此,针对老旧砌体结构房屋进行加固是一门值得研究的课题.为了研究混杂纤维改良活性粉末混凝土(HFMRPC)加固不同高宽比砌体窗间墙的抗震性能,对1面作为对照组的未加固砌体墙和3面不同高宽比的面层加固砌体墙进行了低周往复荷载试验.对比分析了4面墙体的破坏模式、滞回曲线和骨架曲线等抗震性能指标.试验结果表明:HFMRPC面层加固能够有效提高墙体的承载能力,峰值荷载提高约42％;HFMRPC面层对砌体窗间墙具有良好的约束作用,能够有效提升墙体的延性,延性系数提升约199％;HFMRPC面层加固后墙体耗能能力显著提升,累积耗能约提升98％;高宽比是影响墙体破坏模式的重要因素,随着高宽比的减小,砌体墙的承载能力提高,试件的破坏模式趋向于脆性破坏,相反随着高宽比的增大,砌体墙的耗能能力提高,试件趋向于延性破坏.根据试验结果进行了墙体抗剪、抗弯承载力计算分析,并提出了适用于HFMRPC面层加固的抗剪承载力计算公式,可为实际工程应用提供理论基础.
为了探讨钢箱梁桥在爆炸荷载下的动力响应机理及关键参数对其影响规律,基于流固耦合方法,建立了钢箱梁桥、空气和炸药有限元模型,分析了爆炸荷载下钢箱梁桥动力响应机理.随后针对钢箱梁桥的关键参数,分析了各参数对钢箱梁桥的动力响应影响灵敏度,提出了钢箱梁桥在抗爆设计时参数选取规律.研究结果表明:在爆炸荷载作用下,钢箱梁桥的破坏主要分为三阶段.钢材性能由Q345提高为907A钢,钢箱梁桥的凹坑深度和塑性变形区面积减小了33.91％和27.93％;截面形式和爆炸位置两个关键参数的改变涉及纵横隔板对主要迎爆区薄弱位置的加固,能够明显提高钢箱梁桥的抗爆能力.比例距离0.1 m/kg1/3,爆炸位置相同,约束形式由简支改为固支,对钢箱梁桥抗爆性能提升几乎无影响.
结构健康监测系统在桥梁上的测点十分有限,测试数据不完备导致结构安全状态评价困难.提出一种自然纹理条件下的结构全场位移监测方法.通过尺度不变特征变换算法提取结构表面自然纹理特征点,将提取的自然纹理特征点作为结构变形前后的点源数据,通过特征点匹配建立起变形前后特征点的位置关系.进一步,建立结构变形前后自然纹理特征点相对位置变化数学模型,提出结构全场位移矢量计算理论.最后,通过试验梁对方法进行验证,获得了试验梁的全场位移监测结果.验证结果显示,结构边缘挠度最大误差4.94％,平均误差为2.08％,全场位移矢量最大长度误差0.68 mm,最大角度误差0.76°,计算得到的全场位移矢量与结构实际变形一致.
