An experimental study on the temperature and structural behavior of a concrete wall exposed to fire after a high-velocity impact by a hard projectile

Projectiles, such as turbine blades, can be released in an accident and impact structures. Airplanes and other flying objects can also become impact projectiles. These impacts occasionally cause fire when fire loads, such as oil, fuel, and other combustible materials, are present. This study examines the thermal insulation performance of concrete plates and the structural fire behavior of load-bearing reinforced concrete walls that are exposed to fire after a high-velocity impact by a hard projectile. Impact and fire tests were carried out using small-scale concrete plates and reinforced concrete walls. The results show the influence of local damage and the advantage of short-fiber reinforced concrete subjected to impact loads and fire.     

Effect of infiltration on the performance of an unsaturated geotextile-reinforced soil wall

A full-scale geotextile-reinforced soil wall was built in order to assess the characteristics of water infiltration and its effect on the structure performance. Nonwoven geotextiles were selected as inclusions in order to provide not only reinforcement, but also internal drainage to the fine-grained soil used as backfill material. The structure was built in a laboratory setting, which facilitated implementation of a thorough instrumentation plan to measure volumetric water content changes of soil, suction, facing displacements and reinforcement strains. An irrigation system was used to simulate controlled rainfall events. The monitoring program allowed the evaluation of the advancement of infiltration and internal geosynthetic drainage. Evaluation of the effect of the hydraulic response on the overall performance of the structure included assessment of the development of capillary breaks at soil-geotextiles interfaces. Capillary breaks resulted in water storage above the geotextile reinforcements and led to retardation of the infiltration front in comparison to the infiltration that would occur without the presence of permeable reinforcements. After breakthrough, water was also found to migrate along the geotextiles, suggesting that the reinforcement layers ultimately provided in-plane drainage capacity. While generation of positive pore water pressures was not evidenced during the tests, the advancing infiltration front was found to affect the performance of the wall. Specifically, infiltration led to increasing reinforcement strains and facing displacements, as well as to the progressive loss of suction. While the accumulation of water due to the temporary capillary break also resulted in an increased backfill unit weight, its effect on deformation of the wall was not possible to be captured but it is intrinsic on the overall behavior observed in this study. Correlations between reinforcement strains/face displacement and the average of suction in the backfill soil, as measured by tensiometers in different locations within the backfill mass, point to the relevance of the suction as a representative indicator of the deformability of the geotextile-reinforced wall subjected to water infiltration. Reinforcement strains and face displacements were found to reduce more significantly with reduction of suction until a certain value of suction from which the rate of decreasing declines.     

FRP侧贴加固钢筋混凝土梁受弯承载力计算与分析

根据纤维增强复合材料(Fiber Reinforced Plastics)侧贴加固钢筋混凝土构件受弯性能的试验研究,对受弯破坏形态和设计要求进行了讨论。基于平截面假定的正截面受弯承载力的计算理论,提出了FRP侧贴加固构件的正截面受弯承载力的实用计算方法。计算值与试验值吻合较好,并具有较高的可靠性,可供设计参考。探讨了《混凝土结构加固设计规范》(GB 50367-2006）中由梁底改贴到梁两侧面的FRP截面积修正系数ηf的取值情况:在hf/h为定值时,ηf并不象《混凝土结构加固设计规范》所示为定值,而是随加固梁各参数的变化而变化。     

连续配筋混凝土路面设计和施工方法的研究

结合沪宁高速公路(江苏段)扩建工程连续配筋混凝土路面(CRCP)试验段的修筑,介绍了试验路路面的设计,总结了CRCP的施工工艺和注意事项.为连续配筋混凝土路面在我国高速公路中的应用提供了一定的参考依据.     

Empirical modelling of shear strength of RC deep beams by genetic programming

This paper investigates the feasibility of using genetic programming (GP) to create an empirical model for the complicated non-linear relationship between various input parameters associated with reinforced concrete (RC) deep beams and their ultimate shear strength. GP is a relatively new form of artificial intelligence, and is based on the ideas of Darwinian theory of evolution and genetics. The size and structural complexity of the empirical model are not specified in advance, but these characteristics evolve as part of the prediction. The engineering knowledge on RC deep beams is also included in the search process through the use of appropriate mathematical functions.The model produced by GP is constructed directly from a set of experimental results available in the literature. The validity of the obtained model is examined by comparing its response with the shear strength of the training and other additional datasets. The developed model is then used to study the relationships between the shear strength and different influencing parameters. The predictions obtained from GP agree well with experimental observations.     

钢筋混凝土厚板裂缝间距的分析模型

建立一个简单、实用的新模型预测正交钢筋混凝土板的开裂行为。新的模型能解释箍筋对开裂行为的影响,同时也考虑了影响钢筋混凝土构件开裂行为的主要参数,包括混凝土抗拉强度、配筋率、钢筋直径、间距。采用平衡和协调方程,对钢筋混凝土单元进行研究,以求出钢筋和混凝土的平均应力。对本文试验研究结果以及涉及不同结构单元、荷载条件的已有研究成果进行一系列验证比较可知。所提出的裂缝间距模型能够预测不同荷载阶段的裂缝宽度值。在所研究案例中,试验值与模型预测值吻合较好。     

Properties of hybrid fibre reinforced shell for investment casting

In order to improve the properties of silicon sol shell for investment casting process, a varying content of hybrid fibres (aluminium silicate and polypropylene) was introduced into slurry for preparation of fibre-reinforced shell in the present work. The bending strength, self-load deformation at elevated temperature, and the permeability of fibre-reinforced shell specimens were investigated and the fracture surfaces of shell specimens were observed by SEM. The results show that the bending strength of green shell increases with content of fibres in it. The maximum bending strength of 4.96 MPa was obtained in the fired shell with 0.6 wt% hybrid fibres addition. The high temperature self-loaded deformation of specimens of shell reinforced with a hybrid fibre addition above 0.6 wt% is higher than that of the unreinforced. However, the shell with a hybrid fibre addition up to 0.4 wt% exhibits the lower self-loaded deformation at high temperature compared to the unreinforced. It is also found that the permeability of shell specimens can be improved by hybrid fibres addition. Based on the fracture surfaces observation using a scanning electron microscope (SEM), the failure mode of the green shell reinforced with hybrid fibres is identified as fibre rupturing from the substrate of shell specimens, and/ or debonding from adhesive film surrounding it in shell. Even though the specimens of shell being fired at 900 °C for 2 h, the same failure features also exist in the fracture surfaces of specimens. This indicates that the specimens of shell can still be reinforced with aluminium silica fibres (residue of hybrid fibres) for their interpenetrating fibres network structure although go through firing.     

陶瓷垫片在大功率电源产品中的应用

陶瓷垫片是一种高导热性能的导热材料,主要崩于功率器件、散热器之间的传热和电气隔离。文中分析了陶瓷垫片的性能特点,并对它在电源产品应用中的安规,工艺、结构等设计进行了探讨,最后给出了它在电子负载上的应用。     

预应力钢纤维混凝土梁的挠度试验及数值计算

在试验的基础上,对预应力钢纤维混凝土梁的挠度曲线进行了分析,并且利用有限元分析的方法,用ANSYS软件对预应力钢纤维混凝土梁的变形进行了模拟计算,提出了预应力在ANSYS中的表示方法．从试验结果和模拟结果比较中,论证了模拟方法的可行性,为以后的预应力钢纤维混凝土构件分析工作提供了借鉴经验．     

型钢混凝土结构设计规程对比分析(Ⅰ)

首先对日本和欧美等国外有关型钢混凝土结构的设计规程进行了介绍，并结合我国现有的关于型钢混凝土结构的两部规程《钢骨混凝土结构设计规程》（YB9082—97）及《型钢混凝土组合结构技术规程》（JGJ138-2001／J130-2001）的编制背景和依据，对其进行了详细的比较分析。重点对两部规程中有关型钢混凝土梁的正截面抗弯、斜截面抗剪承载能力的计算理论和计算方法进行了比较。通过型钢混凝土梁承载能力的计算实例，对两部规程的应用方法、计算步骤和计算结果作了比较分析。可为两部型钢混凝土结构设计规程工程应用提供参考。