结构用工程竹抗紫外线老化性能的试验研究

紫外线是导致材料老化的主要因素之一,通过人工加速老化试验,模拟太阳光中的紫外线辐射,加上温湿度循环变化的影响,测试未经防护处理的工程竹的物理力学性能,并与花旗松木材在紫外线辐射下的物理力学性能变化进行对比,评价胶合竹、重组竹、花旗松木材试样的抗紫外线老化性能。结果表明,花旗松木材颜色对紫外线辐射比较敏感,受辐射面有明显的颜色变深,在紫外线辐射下胶合竹也发生颜色变黄但没有花旗松木材严重,重组竹的颜色变化不明显;除顺纹抗压强度胶合竹降幅最大外,顺纹抗压弹性模量、顺纹抗拉强度、抗弯强度、抗弯弹性模量均为花旗松木材降幅最大。总体来说,重组竹的抗紫外线老化性能最优,但胶合竹、重组竹、花旗松木材这三种材料在紫外线辐射作用下均有不同程度的力学性能退化,用于室外环境时需要进行防护处理。     

结构用平压毛竹集成材单轴本构关系研究

为研究平压毛竹集成材单轴拉压状态下的应力-应变本构关系,以5年生毛竹的根部、中部和稍部为原料按照1∶1∶1的比例制备的毛竹集成材试件为研究对象。探讨了毛竹集成材受拉和受压状态下的破坏模式及应力-应变全过程曲线。研究结果表明:毛竹集成材的受拉破坏表现出典型的脆性拉断破坏;毛竹集成材的受压破坏属于延性破坏,具体表现3种典型破坏模式:纤维纵向撕裂、竹片层间开裂和褶皱破坏,经历了3个破坏阶段,即线弹性阶段、弹塑性阶段和加速破坏段。对于毛竹集成材单轴受拉应力-应变关系,提出了线弹性模型;对于毛竹集成材单轴受压应力-应变关系,提出了三折线模型和多项式模型,理论模型结果和试验结果吻合较好,为毛竹集成材结构有限元分析提供研究基础。     

Verbundverhalten von Vollgewindeschrauben in Brettschichtholzbauteilen

Bond behaviour of self‐tapping screws being used as reinforcement in glue‐laminated timber elements – Part 2: Analytical and numerical investigations as well bond model derivation for the calculation of anchorage length In favor of the investigation of bond behaviour, force transfer and anchorage length of self‐tapping screws, several tests have been realized at the Chair of Structures and Structural Design in cooperation with the Institute for Building Material Research of the RWTH Aachen University. The experimental investigations comprise more than 160 pull‐out tests of screws with long embedment length and over 84 load distributions tests. Additionally, several tests displaying the effect of longitudinal cracks in the surrounding wood as well as the effect of the screw tip have been conducted. Through various analyses of the bond behaviour, the experimental investigations form the basis for the calibration and evaluation of the numerical models and allow a prediction of the force transfer of the screws in glue‐laminated elements. Design rules that enable the application of the self‐tapping screws as reinforcement in timber elements have been derived from the knowledge obtained in the experimental and numerical investigations. This paper, which results from a research project funded by the German Research Foundation [1], presents the results of investigations on the bond behavior of self‐tapping screws in glue‐laminated timber elements. Part 1 elaborates on the experimental investigations [2] whereas part 2 illustrates the numerical analyses and presents a bond model, which enables the design of the anchorage length and the safe application of the screws as reinforcement in timber elements.     

Brandverhalten von Brettsperrholz

Fire behaviour of cross‐laminated timber Cross Laminated Timber (CLT) is currently used in modern timber structures for load‐bearing wall, floor or roof elements as a high quality, innovative and cost‐effective structural element. Careful planning and implementation ensures the safe use of CLT in buildings with increased fire protection requirements and in accordance with the requirements of building‐design standards (e. g. EN 1995‐1‐1 and EN 1995‐1‐2) [1, 2]. Worldwide, many fire tests with CLT have been per‐formed to investigate the influence of different cross‐sectional build‐ups and various adhesives on the fire resistance of CLT floor and wall elements. This paper gives an overview of the extensive investigations, main outcomes are summarized and recommendations on the fire design of CLT elements are given. The investigations show that an adequate data base exists to reliably describe the fire behavior of CLT.     

胶层厚度和耐湿老化对夹层玻璃中PVB胶与玻璃界面粘结性能的影响

夹层玻璃的耐久性和安全可靠性与其界面粘结性能密切相关。本文首次提出了十字交叉法测量夹层玻璃中PVB胶与玻璃的界面拉伸和剪切粘结强度,分别研究了加载速度效应、PVB胶层厚度效应和湿度老化等的影响。结果表明:测量夹层玻璃中PVB胶与玻璃粘结强度的加载速度应选取5mm/min。当胶合层厚度相同时,界面拉伸粘结强度高于其剪切粘结强度,PVB胶层厚度越大,其拉伸粘结强度和剪切粘结强度都逐渐越低。单层PVB胶片与玻璃之间的界面拉伸粘结强度最大值为11.49MPa。耐湿老化对玻璃与PVB胶的界面粘结强度影响不大,即使老化60天后,其拉伸粘结强度也仅下降12.3%。     

延性夹层层状陶瓷复合材料的研究进展

延性材料作为层状陶瓷复合材料的一种典型夹层材料,对层状陶瓷复合材料性能的提高具有独特的作用。本文从层状结构设计和制备、增韧机理、研究现状,以及存在的问题和发展前景等方面,对近年来采用延性金属和有机树脂作为夹层材料制备的层状陶瓷复合材料进行了综述。     

超白压延玻璃自爆分析和解决措施

针对超白压花玻璃层压自爆问题,对其原因进行了分析,提出了解决此问题的一些措施。     

Influence of water and magnesium ion on the optical properties in various plasticized poly(vinyl butyral) sheets

The study is focused on influences of optical properties change of poly(vinyl butyral) (PVB) sheets determined for safety glass preparing. Optic measurements were evaluated itself and after, the laminated glass was observed. The study deals with a cognizance of causation of the optical properties change in different PVB sheets in dependence on adsorbed water content into the polymer matrix. Results of this work describe the influence of ? OH group content on PVB chain and type and amount of additives adjusting adhesion of PVB towards glass. However, the most important discovery of this work is evaluation of critical water content that leads to haze generation. The evaluation of various types of sheets was performed. At the same time the artificial addition of Mg²⁺ salts of organic acids (with various polarity of the molecule) was evaluated to assess their influence on haze generation. It was found that haze caused by Mg²⁺ salt is possible to eliminate when there is certain water content in PVB. Obtained values and comparisons are very important for PVB sheets industry and for industry dealing with lamination of PVB between glasses. Influence of these factors and comparison of haze generation for various PVB sheets has not been published yet. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

钢框架板柱体系叠层升板施工仿真分析

叠层升板是由传统的逐层提升改为一次提升两块板的提升方法。利用自主开发的基于ANSYS有限元程序的升板模拟仿真程序并以4层升板结构为例,对叠层升板过程中框架结构的屈曲载荷、柱的轴力、柱底弯矩、混凝土板的应力分布等进行分析并与传统升板进行比较。结果表明,在群柱稳定性得以保证的前提下,叠层升板在优化施工工序、降低工程造价、缩短施工周期等方面具有显著的优势和良好的经济效益。     

Preparation of laminated safety glass based on high strength polyurethane film by solution annealing

Compared with the traditional polyvinyl butyral (PVB) laminated glass, the polyurethane (PU) based laminated glass has the advantages of higher impact strength and longer service life. Thus, aromatic polyurethane films have attracted more attentions in recent years due to their high light transmittance, adhesion and functionality. In this paper, the tensile strength of polyurethane films based on bis(4-isocyanatocyclohexyl)-methane (HMDI) have been increased from 27 to 51 MPa and their elongation at break have been increased from 330% to 525% after solvent annealing in toluene. It is attributed to molecular segments with high crystallization and hydrogen bond formation of PU, which are confirmed by FT-IR and XRD characterization. Based on this, laminated glasses with higher impact strength based on the thermoplastic polyurethane films are constructed successfully.