印尼凝灰质粘性土工程特性及地基方案优化

国华印尼穆印电厂属BOO项目,工程场地由第三系凝灰质细粒土组成,具有含水量高、孔隙比大和高塑性等工程特性。地基处理选择中,通过调整总平面布置、垫层试验研究和全面论证,采用厚度达7m的砂砾石垫层换填,放弃了在印尼当地技术难以实现、质量控制难度大、施工工期长和综合造价高的钻孔灌注桩方案。建筑物沉降观测表明,沉降量和沉降差在容许范围内,方案是经济合理和成功有效的。     

Corner Foam Versus Flat Foam: An Experimental Comparison on Cushion Performance

Most cushion structures used in the industry are end caps, edge or corner foam. The bearing area and thickness of the cushioning obtained from cushion curves apply, in principle only, to flat foam because the specimens used to develop the cushion curves are flat foam samples. This study is aimed at finding the difference between the two foams in stress–strain relationship and dynamic impact. A hysteresis cycle compression test, in conjunction with digital image correlation techniques, and a shock cushion test were performed to assess the static stress and strain, energy dissipated and maximum acceleration of flat and corner foams. The study found that the static stress of the corner foam that occurred during the compression testing is 23% higher in average than the flat foam, depending on the compression speed. The shock cushion curve of the corner foam showed a similar pattern as the flat cushion curve but was shifted horizontally to the right as a result of the increased static stress. This study recommends that the conventional cushion curve should be shifted to the right horizontally by about 23–35% in order for a packaging designer to apply it for corner foam. Copyright © 2014 John Wiley & Sons, Ltd.     

黄河特大桥主墩承台井点降水施工

包头至树林召高速公路黄河大桥主桥为85+6×150+85m的预应力连续箱梁,7个主墩,除22#、23#墩位于黄河主河槽,20#、21#、24#、25#、26#墩承台位于黄河滩地。由于黄河水位较高,采用轻型井点降水配合管井降水,进行干处基坑开挖施工。     

双弹簧支撑ETFE枕式膜结构性能研究

利用压缩弹簧代替充气形成无需充气设备的ETFE薄膜结构,采用数值分析与模型试验方法对双弹簧支撑ETFE枕式膜结构的可行性及结构性能进行研究。数值分析结果表明：膜面形状由膜面初始应力和弹簧弹力之比决定;弹簧刚度对膜面应力影响较小,增大弹簧刚度可减小膜面位移但使荷载作用下弹簧弹力的变化增大;膜面矢跨比对膜面应力影响不大,但减小矢跨比使膜面变形增大。模型试验结果表明：膜面成形可通过调整弹簧弹力完成,方法简便可靠,膜面成形精度较高;加载试验中弹簧支撑系统工作可靠,可以较好地追随并张紧膜面;支撑点处膜面应力集中不明显,试验结果与数值分析结果吻合较好。     

大直径圆形钢板桩围堰施工技术

钢板桩围堰由于施工周期短、综合成本低等特点,越来越多的深水基础开始采用。徐明高速淮河特大桥20号承台为直径26.0m的圆形承台,采用圆形钢板桩围堰。结合该工程实例介绍了钢板桩的打拔、腰梁安装、钢板桩锁口漏水处理、硬黏土层湿挖、封底混凝土浇筑等大直径圆形钢板桩围堰施工成套技术。     

跨既有营业线钢盖梁门式墩施工安全技术

以沪昆客运专线赵家里特大桥8号门式桥墩跨既有沪昆铁路上行线施工为实例,结合相关安全技术规范和现场施工安全技术措施等,从前期现场调查开始,到完成桩基、承台、墩身及钢盖梁吊装施工整个过程,全面分析跨既有电气化铁路线钢盖梁门式墩施工安全技术,通过做好事前分析、过程控制、严格落实施工安全技术措施,确保了施工过程安全受控.     

Uplift of elastomeric bearings in isolated bridges subjected to longitudinal seismic excitations

Bearings are used to isolate bridge substructures from the lateral forces induced by creep, shrinkage and seismic displacements. They are set in one or two support lines parallel to the transverse axis of the pier cap and are typically anchored to the deck and to the pier cap. This detailing makes them susceptible to possible tensile loading. During an earthquake, the longitudinal displacements of the deck induce rotations to the pier caps about a transverse axis, which in turn cause tensile (uplift) and compressive displacements to the bearings. Tensile displacements of bearings, due to the pier rotations, have not been addressed before and questions about the severity of this uplift effect arise, because tensile loading of bearings is strongly related to elastomer cavitation and ruptures. An extended parametric study revealed that bearing uplift may occur in isolated bridges, while uplift effect is more critical for the bearings on shorter piers. Tensile displacements of bearings were found to be significantly increased when the isolators were eccentrically placed with respect to the axis of the pier and when flexible isolators were used for the isolation of the bridge. The results of this study cannot be generalised as bridge response is strongly case-dependent and the approach has limitations, which are related to the modelling approach and to the fact that emphasis was placed on the longitudinal response of bridges.     

基于CAE优化分析的汽车水箱盖中盖注塑模设计

针对汽车水箱盖中盖的结构特征,结合CAE技术对产品进行注塑成型过程模拟分析,确立了点浇口浇注系统并优化了冷却方案,在此基础上完成了注塑模设计。在模具结构设计中,提出用斜滑块和斜顶组合脱螺纹机构代替常用的旋转脱螺纹方式。模具结构合理,运动可靠,产品成型质量好。     

充气式张弦穹顶结构静力性能与稳定性研究

基于Tensairity结构概念设计了跨度80m的充气式张弦穹顶结构,建立了精细化的有限元模型,实现了零状态、初始态和荷载态的全过程数值模拟,分析了结构在不同工况下的静力性能和稳定性。研究表明：该结构体系具有良好的静力性能和稳定性,内压在1~4kPa范围内即可保证充气气囊对刚性构件的支撑作用;整体结构没有出现明显的弹性失稳问题,导致结构失效的主要原因是构件的材料破坏和膜材的应力松弛;当内压较低时,结构因上层膜面松弛而失效;当内压较高时,结构因刚性上弦大范围进入塑性状态而破坏。自振特性分析表明,该结构的整体刚性较大,但绕中心轴的抗扭刚度较为薄弱。     

水泥土搅拌桩的加固机理及其应用

水泥土桩加固软土地基，一般形成半刚性桩复合地基。从水泥土桩复合地基的构成，对水泥土桩桩身、垫层及桩间土的受力特性及相互作用机理进行了分析和探讨，同时对水泥土搅拌桩复合地基的设计理论进行了阐述，对施工方案及施工注意事项提出相关建议。