Gold(I)‐Catalysed Cyclisation of Alkynoic Acids: Towards an Efficient and Eco‐Friendly Synthesis of γ‐, δ‐ and ϵ‐Lactones

The improved synthesis of γ‐, δ‐ and ϵ‐lactones using a dinuclear N‐heterocyclic carbene (NHC)‐gold(I) catalyst is reported. This solvent‐free process provides access to γ‐ and δ‐lactones in high regio‐ and stereoselectivity. Reactions were performed at low catalyst loadings and without the need for any additives. The use of a digold pre‐catalyst provides a new synthetic route to functionalised ϵ‐lactones, poorly accessible using previous methodologies.

     

Ein Modell zur Berechnung des Verformungsverhaltens von horizontal hochzyklisch beanspruchten Pfählen

A model for the behavior of horizontally high‐cycle loaded piles For the prediction of the deformation for long or intermediate long piles under lateral high cycle load, embedded in non‐cohesive soil, a simplified engineering model for drained conditions is developed based on the high cycle accumulation (HCA) model of Niemunis , Wichtmann and Triantafyllidis [1]. The monotonic soil deformation under static load is approximated by elastic springs, placed around the pile, whereas the accumulation of soil deformations under cyclic loading is modelled by viscous dashpots (cyclic creep) according to the HCA model. In most instances this contemplation is physically validated by element tests. In conjunction with the pile the spring‐dashpot elements represent an elastically embedded beam system. Two versions of the model with a two‐sided arrangement of springs and dashpots on the Lee‐ and Luv‐side and a one‐sided arrangement only on the Lee‐side will be presented. The pile displacement prediction of the model is compared with the results obtained by existing engineering models already known in the literature and the solution of a 3‐D‐finite element simulation with the HCA model.     

Methoden zur Analyse des Bruchverhaltens hochfester Stahlfaserbetone

Methods for analyzing the fracture behavior of high‐strength steel fiber‐reinforced concretes High‐strength and ultra‐high strength fiber‐reinforced concretes are most suitable for applications with extreme mechanical loads. These extreme conditions require a ductile behavior under tensile loading, which is obtained solely by the addition of steel fibers and their working mechanism. Profound know ledge on the working mechanism of the steel fibers is necessary for optimizing this material. Usually, this knowledge is obtained by means of classical measuring techniques of destructive tests. Adopting measuring techniques from non‐destructive material testing helps to analyze and to identify the different stages of the fracture mechanism of high‐strength and ultra‐high strength fiber‐reinforced concretes in detail. The application of different non‐destructive measuring techniques is shown exemplary on tensile tests conducted on an ultra‐high strength fiber‐reinforced concrete and its applicability for analyzing the fracture behavior is discussed. The main focus is on the characterization of the relevant failure modes under tensile loading by the different measuring techniques and the comparison with classical measuring techniques (e. g. extensometer). The tensile tests have been analyzed by optical deformation measurements using digital image correlation (DIC), acoustic emission analysis (AE), and 3D computed tomography (CT).     

Responses of a cylindrical lined tunnel due to internal dynamic load in two distinct mediums: Ideal elastic and saturated porous medium

The dynamic responses of a lined tunnel subjected to dynamic loading is one of the key issues that needs to be addressed prior to the design and construction of tunnels. While the tunnel lining and surrounding soil are commonly designed in ideal explosion-proof engineering as ideal elastic media to simplify the problem, in reality; soils are porous geo-materials. Therefore, the concern is whether this practice is more conservative or close to the reality, in contrast to the scenario where the surrounding soil is assumed as a saturated porous medium. This study investigates the differences and relationships between the dynamic responses of the lining structures in two immensely disparate media: ideal elastic medium and porous saturated medium. Firstly, to avoid the complexity of 3D numerical studies, 3D analytical solutions for the responses of the lined tunnel in both the ideal elastic medium and porous medium due to internal dynamic loading are derived using Fourier and Laplace transforms. Also, the differences between the dynamic responses (e.g., the radial displacement, radial effective stress, and hoop effective stress) of the lining structures in two media are determined to assess the rationality of assuming that the soil around the lined tunnel is an infinite elastic compressible medium. Finally, the influence of the porosity on the dynamic response of a cylindrical lined tunnel subjected to dynamic loads is examined.     

Vibration velocity control standard of buried pipeline under blast loading of adjacent tunnel

With the rapid development and construction of China’s transportation system, more and more projects are being conducted near existing buried pipelines, which will inevitably influence the safety of the pipelines. Among the safety issues related to buried pipelines, blasting during the construction of an adjacent tunnel is one of the most adverse factors for existing pipelines. To ensure the safety and normal operation of the pipelines, a method for determining the peak vibration velocity control standard for buried pipelines under blast loading is established in this study. The acceleration time-history function that acts on the rock mass under the blasting seismic wave is derived as external excitation acting on the pipeline. By using the acceleration time-history function as input and combining it with a dynamic and static analysis of the pipeline, the critical vibration velocity of pipelines under the action of blast loading can be determined by the von Mises yield criterion of the buried pipeline material. Using the Dashanpi No. 1 tunnel project in Shenzhen, China as a background, the critical velocity control standard for buried pipelines under tunnel blast loading can be set at 190 mm/s without considering either the initial defects or the corrosion conditions during the operation.     

钢桥面沥青混合料铺装应变动态响应实测研究

掌握钢桥面沥青混合料铺装层在车载作用下的真实力学特性对桥面铺装体系设计有重要意义,而现阶段现场桥面铺装层的力学实测数据仍偏少,尤其缺乏对铺装层不同温度下服役时力学特性的长期监测。为此,该研究对钢桥面双层SMA混合料铺装进行现场实桥加载试验,实测铺装层在低温、中温、高温3种服役温度下的应变响应数据。试验结果表明,钢桥梯形肋正上方铺装层混合料在中低温服役状态下主要承受压应变的作用,而在高温服役时则主要承受拉应变的作用;动载作用过程中铺装层底纵向应变会出现拉压应变交替作用的现象,而横向应变只体现为拉应变或压应变的形式;加载车行驶速度对混合料的应变极值均有明显的影响,加载车低速行驶时混合料层底横向及纵向变形最为显著。同时,研究利用加载试验中铺装层应变响应时程曲线,计算不同加载状态下混合料对应的加载频率数值,计算结果可为钢桥面铺装混合料室内试验中加载频率参数的确定提供参考。     

高比例掺炼催化汽油预加氢单元的优化设计

以某厂60万t/a连续重整装置为例,从原料油优化处理、采用催化剂级配装填技术以及优化注冷氢位置等方面探讨了高比例掺炼FCC汽油石脑油加氢单元的工程设计。通过采取多种优化设计,使加氢精制油中杂质含量完全满足重整进料要求,解决了炼厂重整原料不足的问题,满足了企业汽柴油产品质量升级的需求。     

长期循环荷载下珊瑚砂累积变形特性试验研究

对取自南海的珊瑚砂进行等向和K_0固结的三轴排水剪切试验,发现固结路径对珊瑚砂的剪切行为有显著影响。在此基础上,采用K_0固结条件,设计一系列不同围压和循环动应力比的长期排水循环加载三轴试验,研究得到珊瑚砂具有门槛颗粒破碎循环动应力比,安定性理论可用于解释不同动应力比长期循环加载下珊瑚砂的累积变形发展模式。基于静力和动力试验结果,引入相对偏应力水平,建立能反映初始固结状态和循环动应力比的珊瑚砂排水循环加载轴向残余累积应变显式计算模型,对预测循环荷载下珊瑚砂地基长期沉降有积极意义。     

宋式带“昂”斗栱节点力学性能试验研究

古建筑中宋式斗栱节点最为显著的特征之一就是带有“下昂”。为研究具有这种特征的斗栱节点的受力性能,制作 1∶3.52的缩尺模型试件进行竖向荷载试验和水平低周反复荷载试验,依据宋《营造法式》和实际建筑的 “有昂无梁栿”和“有昂有梁栿”两种类型的宋式斗栱节点模型,设计并制作了以柱头斗栱节点为对象的试验模型。研究结果表明：在竖向荷载作用下,栌斗始终作为薄弱构件首先破坏;下昂与梁栿虽打断了斗栱节点分层叠加,但其依旧能保持良好的整体性;水平荷载作用下单个斗栱节点的倒三角形构造易发生转动,但加入梁栿后,节点的转动受到约束而发生滑移,此时斗栱表现良好的耗能效果,由此说明斗栱节点良好的抗震性能并非来自单个斗栱节点,而是由其通过相互约束协同工作而产生;底部暗销有较强的锚固作用,斗栱节点水平承载力主要由底部暗销的锚固力和柱与斗栱节点接触面的摩擦力组成。     

方钢管混凝土柱-组合梁框架抗连续倒塌性能试验研究

为了研究组合梁对方钢管混凝土柱-组合梁框架抗连续倒塌性能的影响,设计了带有混凝土现浇楼板方钢管混凝土柱-组合梁框架(CFSTCBF)及不带楼板的方钢管混凝土柱-钢梁框架(CFSTSBF),采用拆除构件法对两个试件的抗连续倒塌性能进行竖向加载试验研究,对其在中柱失效工况下的破坏模式、受力机理以及主要的抗力机制进行分析,同时对现浇混凝土楼板和节点在连续倒塌过程中的性能进行探讨。研究表明：两个试件的破坏均是由正弯矩区钢梁破坏引起,结构的倒塌阶段可分为弹塑性阶段、塑性阶段、过渡阶段和悬链线阶段,压拱机制和悬链线机制均能改善结构的抗倒塌性能;混凝土楼板可以有效增强结构的承载能力,提高结构的初始转动刚度,但在改善结构变形能力方面的作用较弱。