砌体结构的耐久性

在总结国内外有关工程实践、标准规范及研究成果的基础上,概括了砌体结构耐久性的基本内涵、设计概况、耐久性常见的问题、耐久性设计措施对策和耐久性检测方法简化的建议。相关内容也已成为砌体规范修订相应条文的背景材料。     

历史建筑砖砌体耐久性研究

通过对西安碑林博物馆历史建筑砖砌体的耐久性现状调查,以及砖表面物质的X-ray衍射分析,发现这些历史建筑普遍存在砖砌体耐久性劣化现象,并且随环境条件和建筑材料的不同,劣化程度出现明显差异。根据调查结果,分析历史建筑砖砌体耐久性劣化原因及其影响因素,为今后这些建筑物的砖砌体耐久性修复提供了可靠依据。     

Durability study of stabilized earth concrete under both laboratory and climatic conditions exposure

The strength and durability of the earth can be improved considerably by the addition of different stabilizers. In this work, four stabilizers have been used: cement, lime, cement plus lime and cement plus resin and then evaluated by various laboratory tests as well as in real climatic conditions. In general, it has been noted that all treated walls showed no signs of deterioration after 4 years exposure in real climatic conditions even though the laboratory test conditions are more severe compared to the natural climatic conditions of the region of Biskra where this present work has been carried out. Among the 4 stabilizers tested, the cement plus resin showed the best durability behavior.     

Pretreatment for membrane water treatment systems: a laboratory study

The goal of the work was to determine if biological treatment of water containing soil-derived humic substances has the potential for reducing the fouling of membranes used in water treatment. Laboratory scale biological filters containing biologically active carbon or iron oxide coated sand were fed humic-laden water with or without prechlorination. This stream was split, with half being further treated by microfiltration. Treated water was assessed for total organic carbon removal and biofouling potential using a glass bead assay and membrane assay for total cell counts, fouling layer thickness, and flux reduction. A combination of these assays provided more insight than any single measurement. Compared to untreated control water, biological treatment was capable of reducing downstream fouling of membrane systems. For example, fouling layer thickness was reduced by half after biological treatment, and cell counts were reduced four- to five-fold. Biological treatment coupled with microfiltration provided the best reduction of fouling, while prechlorination did not appear to impact the process. These results suggest that biological treatment may be valuable in reducing membrane fouling while reducing the amount of disinfectants used in pretreatment.     

砌筑用粉煤灰砂浆性能研究

本文对比研究了砌筑用水泥砂浆与粉煤砂浆的性能，研究结果表明，粉煤灰能有效改善砂浆如易性，提高砂浆后期强度及耐久性。     

Clogging of stormwater gravel infiltration systems and filters: insights from a laboratory study

Stormwater infiltration systems are widely used in the control of polluted urban runoff. They are very effective in reducing the volume of stormwater runoff and improving its quality, but they are known to be prone to clogging. Whilst it is evident that clogging determines the design lifespan of infiltration systems, quantitative understanding of the clogging process is currently very limited. A laboratory study was therefore undertaken to better understand physical clogging processes, with the ultimate aim of developing a clogging model for stormwater infiltration systems. This paper presents findings from one-dimensional (1-D) experiments conducted on a gravel filter column. Physical clogging was studied under both constant and variable water levels, and for different sediment inflow concentrations. It was found that a clogging layer forms at the interface between the filter and underlying soil, irrespective of the inflow regime of both water and sediment. It was also found that clogging is much slower if the water level is kept at a constant level than if it varies within the column, due to formation of a sediment plug that 'shelters' the filter/soil interface. Most importantly it was shown that physical clogging is mainly caused by migration of sediment particles less than 6 microm in diameter. A simple regression model was proposed and tested for the prediction of clogging due to stormwater sediment.     

Long-term damage of historic masonry: A probabilistic model

Creep and the creep-fatigue interaction have shown to strongly influence the mechanical behaviour of ancient masonry and long-term heavy loads proved to cause a continuous damage. The problem of achieving a reliable life-time estimate of historic masonry toward the effects of persistent loading has been dealt with by a probabilistic approach. The results of pseudo-creep tests on ancient masonry of different ages and their interpretation through a probabilistic model are presented, aimed to the individuation of a random variable as a significant index of vulnerability, and to the solution of the classic problem of reliability in stochastic conditions.     

Seismic performance evaluation of slender masonry towers: a case study

Historical structures and preserving their cultural values are crucial issues for humanity, not only because of their link to important certain periods in the past, but also their unique architectural features. Although many historical structures continue to offer services while keeping their historical values, some of them are at high risk in seismic prone regions. Therefore, the understanding of their structural performance under strong ground motions has been of significant importance to the civil societies as well as engineering community. The structural systems of historical buildings, generally, consist of masonry walls or piers. The behavior of such walls is controlled by either deformation or force. Seismic performance evaluation of historical structures can be carried out within the framework of performance‐based evaluation principles. This paper mainly discusses the basic principles to be considered in performance‐based seismic evaluation of historical structures. Proposed seismic hazard levels, evaluation of existing seismic hazard, selection of earthquake ground motions as well as site geology, geological and tectonic settings of the area, seismic activity of the region and local soil conditions are needed for a thorough performance evaluation. Seismic performance evaluation of a clock tower located in eastern Turkey was accomplished based on the proposed principles. Copyright © 2015 John Wiley & Sons, Ltd.     

预应力砌体抗震性能的试验研究

本文通过8片不同类型的预应力混凝土小型空心砌块砌体的水平低周反复荷载试验以及2片普通混凝土小型空心砌块砌体的对比试验,研究了预应力砌体破坏形态、滞回特性、延性、刚度退化曲线等抗震性能,明确了预应力、窗洞以及构造措施对混凝土小型空心砌块墙体的开裂荷载、极限荷载和变形性能的影响。研究结果表明,预应力延缓了混凝土小型空心砌块墙体的开裂,提高了结构的开裂荷载和极限荷载;预应力改变了墙体破坏时的裂缝分布形状,裂缝密而细,几乎布满墙体全部灰缝,主裂缝不明显;预应力提高了墙体的刚度、延性和耗能能力;在窗洞底部现浇水平配筋混凝土条带能有效地抑制裂缝的产生和发展,并能提高墙体的变形和耗能能力。     

A laboratory study of landfill-leachate transport in soils

Continuous flow experiments were conducted using sand-packed columns to investigate the relative significance of bacterial growth, metal precipitation, and anaerobic gas formation on biologically induced clogging of soils. Natural leachate from a local municipal landfill, amended with acetic acid, was fed to two sand-packed columns operated in upflow mode. Degradation of the influent acetic acid resulted in the production of methane and carbon dioxide, and simultaneous reduction of manganese, iron, and sulphate. Subsequent increase in the influent acetic acid concentration from 1750 to 2900 mg/l, and then to 5100 mg/l, led to rapid increase in the dissolved inorganic carbon, solution pH, and soil-attached biomass concentration at the column inlet, which promoted the precipitation of Mn(2+) and Ca(2+) as carbonate, and Fe(2+) as sulphide. An influent acetic acid concentration of 1750 mg/l decreased the soil's hydraulic conductivity from an initial value of 8.8 x 10(-3)cm/s to approximately 7 x 10(-5)cm/s in the 2-6 cm section of the column. Increasing the influent acetic acid to 5100 mg/l only further decreased the hydraulic conductivity to 3.6 x 10(-5)cm/s; rather, the primary effect was to increase the length of the zone experiencing reduced hydraulic conductivity from 0-6 cm to the entire column. As bioaccumulation was limited to the 0-5 cm section of the column, and the effect of metal precipitation was negligible, the reduction on the deeper sections of the column is attributed to gas flow, which was up to 1440 ml/day. Mathematical modelling shows that biomass accumulation and gas formation were equally significant in reducing the hydraulic conductivity, while metal precipitation contributed only up to 4% of the observed reduction.     

Scenariopolis: the civil engineering systems policy research laboratory

This paper describes a system dynamics model of a hypothetical region. The region provides an environment for three typical civil engineered systems; water resource, sewage treatment and urban transportation. The interaction of the key parameters of each system within the system, as well as among the systems, are examined through scenario analysis using simulation and analytical techniques.     

不同砌筑方式蒸压加气混凝土砌块砌体抗压强度研究

主要研究采用不同方式砌筑的蒸压加气混凝土砌块砌体的轴心抗压强度,讨论蒸压加气混凝土砌体的裂缝发展特点和破坏特征,分析其抗压承载力及应力应变关系。结果表明,蒸压加气混凝土砌体开裂后砌体还可以承受一定的压力,延性较好。蒸压加气混凝土砌体对砌块的抗压强度利用率较高,轴心受压砌体的抗压强度为砌块抗压强度的70%左右。在灰缝中配钢筋和纤维能显著提高抗压砌体的开裂强度,延缓抗压砌体开裂,提高其延性。蒸压加气混凝土承重砌块砌体的强度与传统承重砌体的强度水平相当,完全可以用于多层住宅房屋的承重结构。     

九层组合砌体结构模型动力性能实测分析

本文作者着重介绍并研究了１／４比例的组合砌体结构模型的自振频率、振型、阻尼比等项动力性能的实测情况。这对于合理地评价、分析,尤其是高宽比较大的组合砌体结构的抗震性能,具有一定的参考价值。     

Feasibility study for drone-based masonry construction of real-scale structures

The additive manufacturing of real scale structures using UAVs (drones) is a new discipline with challenges as wide as the possibilities it opens up for the future. UAVs must not be seen as the only way of robotizing future construction sites, but in combination with other kinds of robots. This adequate combination is indeed likely to reduce the influence of factors that usually badly affect the quality and profitability of construction projects, such as human factors, execution slowness, insecurity, insufficient communication between the stakeholders, weather conditions, strikes, lack of skilled labor, etc. The aim of this research, carried out jointly by MIT and UCLouvain since 3 years, was to lay the necessary groundwork, still not explored elsewhere, in order to prove the feasibility of building real-scale structures, in particular masonry structures, with big custom-built drones. In particular, the objective was to investigate the drones precision, their behavior while transporting, handling and laying loads, but also to draw the first guidelines for the design of “Drone compatible” construction elements: their shape, the way they should be assembled together, how to minimize their weight, how to connect them together, how to ensure their stability. This publication summarizes the work carried out so far in this field, provides the results of the laboratory tests and proposes development and improvement paths for the future. In particular, lab tests with a big drone assembling different kinds of more and more complex construction elements are commented. Several conclusions can be drawn from the study, the first one being that the research is worth going beyond the step of proving the feasibility. Indeed, it shows that using UAVs for the construction of future real scale structures is certainly not a utopia and is very promising. However, it requires further developments, not only about the drone themselves (guiding systems, handling systems, robustness, power supply), but also about the way to pass from the laboratory stage to the construction of real structures with a complex geometry, composed of slabs, walls, connections and finishing.     

The vapor diffusion resistance and air permeance of masonry and roofing systems

Several building parts contain layers composed of separate elements that are mortared together or simply interlock or overlap. Typical examples are masonry walls, brick veneers, tiled roofing systems and slated roofing systems. The mortar joints, the interlocks and overlaps should affect the water vapor diffusion resistance and the air permeance of the composite layer, at least in comparison with the vapor and air flow properties of the pure elements. However, little information is found in literature that allows a quantification of the differences.     

条石砌筑石墙抗震性能试验研究

为研究条石砌筑石墙的抗震性能及滞回特性,进行了5片干砌甩浆石墙试件的低周水平反复荷载试验.主要研究参数包括砂浆强度和压应力.通过试验研究了干砌甩浆承重石墙的破坏形态、强度、滞回曲线、骨架曲线、变形能力、耗能能力和刚度退化规律.试验结果表明:石墙的最终破坏形态主要受压应力水平的影响;受剪承载力随砂浆强度和压应力水平的提高...     

Retrofitting of masonry building with reinforced masonry ring-beam

To improve the behavior of the connection between the roof and the masonry walls, reinforced concrete ring-beams were commonly used in these last years. This technique have proved to be effective, but, at the same time, the different properties of concrete and masonry require an adequate connection to the underlying masonry and the additional mass added on the top of the building may have negative effects when the building is subjected to seismic loading. To avoid such shortcomings a possible solution could be the use of masonry ring-beams reinforced with composites. After an analysis of the behavior of this new structural solution, the results of a first set of experimental tests will be presented and discussed. Finally, a first application of a FRP masonry ring-beam will be illustrated.     

多层砌体房屋抗震概念设计研讨

对多层砌体房屋地震破坏情况及其产生的原因进行了分析和研讨 ,特别强调了进行房屋抗震概念设计的重要性 ,指出了房屋抗震概念的设计要点和设计步骤     

某砖石古塔动力特性测试研究

动力特性是结构自身的重要特征之一,是评价古塔抗震性能和损伤状态的重要指标。采用敲击激振法对某砖石古塔的动力特性进行了测试,根据测试所得各测点的加速度时程和自功率谱函数图,分析了结构的自振频率和阻尼及结构振型,并用有限元软件ANSYS对测试结果进行了进一步验证。测试和分析结果可为同类古塔的维护和开发提供理论依据。