土木建筑施工中大体积混凝土结构的运用

受到经济发展的带动,城市化进程加快推进,建筑数量、规模大幅度上涨,在城市发展中土木建设成为了重点内容。大体积混凝土结构的应用,为土木工程建筑建设带来了支持,最大化地保障建筑趋于安全性、稳定性。然而在大体积混凝土结构的施工工艺中,经常出现不符合工艺要求的问题,这就需要加强施工管理,切实保证工程质量达到标准。运用大体积混凝土的施工结构来分析土木建筑项目、大体积混凝土结构、施工工艺中出现的不良现象,深层探究施工技术要点,科学地运用大体积的混凝土施工技术,从而提高土木建筑的建设质量。

建筑用织物和涂层材料

建筑用织物结构有重量轻，装配和运输方便等优点，早在上世纪50年代，随着涂层织物的成功开发，建筑用织物结构就已开始应用于体育场馆，大卖场，空港飞机库和仓库等大型建筑项目。国际产业织物协会（IFA）下属轻结构协会（LSA）列举了8种美国最主要的采用织物的建筑轻结构，它们包括：抗拉（或张力）结构，框架支撑结构，空气支撑结构，

Analysis on degradation behaviors of sisal fibers at various pH conditions

The degradation behaviors(mass loss,tensile strength,crystallinity index,and microstructure)of sisal fibers immersed in sodium hydroxide solution with pH of 13.6,12.9,and 11.9 were investigated via X-ray diffraction and scanning electron microscopy.A three-stage degradation process of natural fibers in an alkaline environment was proposed.The results showed that the sisal fibers exhibited a sharp mass loss over the first 7 d of degradation under all pH conditions,attributable to the rapid hydrolysis of lignin and hemicellulose at the fiber surface.The sisal fibers degraded at pH 12.9 and 13.6 over 1 month exhibited significantly lower tensile strengths(181 and 195 MPa,respectively)than the original fibers(234 MPa)because of the loosely bound structure of the component microfibrils caused by the hydrolysis of the linking lignin and hemicellulose.After 6-month degradation,stripped microfibrils occurred in the fibers,resulting in substantial degradation in tensile strength.The sisal fibers degraded at pH 11.9 largely maintained their integrity and tensile strength,even after 6 months,indicating that reducing the environment pH can effectively mitigate the degradation.

Correlation between microstructural features and tensile strength for friction welded joints of AA-7005 aluminum alloy

Similar friction welded joints of AA-7005 aluminum rods were fabricated using different combinations of process parameters such as friction pressure(1.0, 1.5 and 2.0 MPa) and friction time(10, 15 and 20 s). Interfacial microstructure and formation of intermetallic compounds at the joint interface were evaluated via scanning electron microscopy(SEM) equipped with energy dispersive spectrum(EDS), and optical microscopy(OM). Microstructural observations reveal the formation of intermetallic phases during the welding process which cannot be extruded from the interface. Theses phases influence the tensile strength of the resultant joints. From the tensile characteristics viewpoint, the greatest tensile strength value of 365 MPa is obtained at 1.5 MPa and 15 s. Finally, the role of microstructural features on tensile strength of resultant joints is discussed.

An ultrahigh strength steel produced through deformation-induced ferrite transformation and Q&P process

In this work,DIFT technology and Q&P process were combined in order to introduce ultrafine-grained ferrite into the matrix of martensite and retained austenite to develop a new kind of advanced high strength steel,and two kinds of steels were investigated by this novel combined process.The newly designed process resulted in a sophisticated microstructure of a large amount of ferrite(about 5 m in diameter),martensite and a considerable amount of retained austenite for TRIP 780 steel.The ultimate tensile strength can reach about 1200 MPa with elongation above 16% for TRIP 780,that is much higher than the one solely treated by Q&P process.Tensile tests showed that both steels with the novel combined process achieved a good combination of strength and ductility,indicating that the new process is promising for the new generation of advanced high strength steels.