Non-contact methods of measuring moisture concentration in external layers of building partitions II—Monitoring of the water vapour condensation on porous surfaces

This paper present the results of the investigation into a potential application of laser radiation for the detection of phase transition processes occurring on the surface layers of porous materials. An attempt was made to discuss in the approximation equations, the relationships between coefficients of the reflected light, the temperature and humidity of the surrounding environment. Laser light reflected from the porous surface carries information about the roughness of the structure. The presence of water microdrop on the surface of the porous material, as a result of condensation and thus a phase transition, leads to the phase displacement of individual rays, which is represented by different images. Therefore, a comprehensive analysis of the reflected light parameters allows a dynamic study of the phase transition phenomena without mechanical intervention.     

Development of non-contact scanning vibration measurement system for real-scale structures

In order to rationalize vibration monitoring in structures, this paper addresses a non-contact scanning vibration measurement system employing laser doppler vibrometers. Generally, in the case of measurement for concrete members or dirt-adhering steel members, monitoring by laser doppler vibrometers is extremely difficult due to low laser reflectance. In this study, it is experimentally verified that the return or reflected laser beam quantity depends on subtle differences in the surface condition of a measurement object. Therefore, by searching the vicinity of the insufficient measurement point for the optimum point which provides a maximum reflected laser beam quantity, a remarkable improvement of measuring accuracy for real-scale structures can be achieved. As an example, vibrations of steel girders and reinforced concrete deck of actual bridges are measured, so as to verify the measuring accuracy of the developed system, and eigen local mode shapes of the members are able to be identified.     

Non-contact methods of measuring moisture concentration in external layers of building partitions. I—The influence of geometrical microstructure on the kinetics of moisture condensation on glass surfaces

This paper presents the results of the larger study on the potential application of laser radiation for the detection of phase transition processes. The proposed experimental method allows a dynamic study of the phenomena without mechanical intervention. This seems to be the best practical solution particularly when the access for the other methods is very restricted. The investigations give an evidence of the strong relationships between the rapid growth of water vapour condensate and the roughness of the surface. Condensation process therefore can be modified by a careful design of the geometrical structure of surface.     

碳纤维缠绕叠合梁冲击破坏效果模型参数的监测

借助振动试验,对两种类型缠绕叠合材料(重、轻)的冲击韧性进行研究。由于尚缺少有效的缠绕叠合材料冲击试验相关文献,本文采用简单的对称冲击。对两种破坏水平(BVID和表面不明显破坏)模型参数的变化进行分析,振动试验结果表明:与重缠绕试件相比,轻缠绕试件具有较好的阻尼,对冲击破坏十分敏感。而且,与刚度变化相比,阻尼与对破坏更敏感。因此,可推断出,阻尼可用以替代自然频率作为结构健康监测破坏的指标。     

路用无黏结集料的动载结构性评价方法研究

由松散集料组成的级配碎石在路面结构中具有很强的动载结构性,但目前对材料的结构性描述是定性的。为了探讨级配碎石动载结构性的定量化描述,采用上表面振动方法成型试样,以水为扰动因素,在3种围压下对试样进行的3000次动载试验,并根据松散集料基层沥青路面的典型破坏形式,定义了级配碎石的动载可稳性、可变性和综合结构性。试验表明:结构可稳性反映了填充料水稳定性,结构可变性表征了骨架排列的稳定性能,二者是土结构性的两个方面,围压σ3≧15 0 kPa时,级配碎石的结构性被钝化,结构性参数应在小围压下测定;采用结构性参数定性评价级配碎石的结构性是可行的。     

Use of a laser camera scanner to highlight the surface degradation of stone samples subjected to artificial weathering

A vision technique system was implemented in order to highlight the deterioration developing on the surfaces of stone samples during an artificial ageing test with marine spray. The system, which employs a matrix CCD camera and a laser beam, provides various kinds of information about the decay suffered by the stone samples, by comparing two types of visual information at different times throughout the ageing test: the partial digital images of the sample surfaces and then the surface relief and laser light reflection obtained by casting a sheet of laser light on to the material. The accuracy of the laser camera scanner is evaluated in the first part of this paper. The methodology was successfully used to identify the degradation morphologies occurring on five types of limestone exposed to salt spray, and to quantify the deterioration using statistical parameters computed from digitized visual data.     

Use of a laser camera scanner to highlight the surface degradation of stone samples subjected to artificial weathering

A vision technique system was implemented in order to highlight the deterioration developing on the surfaces of stone samples during an artificial ageing test with marine spray. The system, which employs a matrix CCD camera and a laser beam, provides various kinds of information about the decay suffered by the stone samples by comparing two types of visual information at different times throughout the ageing test: the partial digital images of the sample surfaces and then the surface relief and laser light reflection obtained by casting a sheet of laser light on to the material. The accuracy of the laser camera scanner is evaluated in the first part of this paper. The methodology was successfully used to identify the degradation morphologies occurring on five types of limestone exposed to salt spray, and to quantify the deterioration using statistical parameters computed from digitised visual data.     

Impact of phase change wall room on indoor thermal environment in winter

Through combining gypsum boards with phase change materials (PCM), the compound phase change wallboards are formed. The transition temperature and latent heat of these phase change wallboards are tested by differential scanning calorimetry (DSC). The results indicate that these phase change wallboards can be applied in buildings to save energy cost and electric power. Then, the thermal properties of phase change wallboards are analyzed. The phase change wall room and the ordinary wall room are experimented and compared under the climatic conditions in winter in the northeast of China. The impact on the indoor temperature, surface temperature of wallboards and thermal flow through wall are achieved. Finally, it can be got that the phase change wallboards can improve indoor thermal environment.     

用于墙体和地板的相变材料性能

利用差示扫描量热仪研究了分别由48#石蜡和液态石蜡、癸酸和硬脂酸组成的2种二元混合物的相变温度和相变潜热,并选取其中6种试样进行5 000次热循环试验,旨在寻找适合于建筑围护结构中使用的相变储能材料.结果表明:2种二元混合物的相变温度和相变潜热随配制比例的不同发生了较为明显的变化;它们的热稳定性均较好,且脂肪酸混合物的热稳定性优于石蜡混合物.同时给出了适用于被动式相变墙体和主动式相变供暖地板或墙板中使用的相变材料混合物配比.     

蒸汽养护下GBFS代砂高性能水泥基材料宏微观分析

通过试验测定了蒸汽养护下不同龄期粒化高炉矿渣(GBFS)代砂高性能水泥基材料的抗压强度及孔隙结构特征,分析了抗压强度与空气含量、气泡平均弦长、间距系数和比表面积的关系。结果表明:石英砂高性能水泥基材料抗压强度略大于GBFS代砂高性能水泥基材料,但GBFS代砂高性能水泥基材料7~28 d的抗压强度增长速率要大于石英砂高性能水泥基材料。不管是GBFS代砂高性能水泥基材料还是石英砂与混合骨料高性能水泥基材料,空气含量、气泡间距系数和平均气泡弦长均与抗压强度呈现负线性相关;且在抗压强度与抗折强度相同时,GBFS代砂高性能水泥基材料的分形维数要大于石英砂高性能水泥基材料。粒化高炉矿渣骨料-胶凝材料过渡区要比石英砂胶凝材料过渡区更为致密,这是由于在过渡区产生新的水合物,且填补了过渡区的空隙。     

Monitoring the effects of impact damages on modal parameters in carbon fiber entangled sandwich beams

The aim is to study the impact toughness of two types of entangled sandwich materials (heavy and light) with the help of vibration testing. A simple case of symmetrical impacts is studied in this article as no literature is available regarding impact tests on entangled sandwich materials. The variation of modal parameters with two levels of damage (BVID and Damage not apparent on the surface) is studied. Vibration test results show that the light entangled specimens possessing good damping capabilities seem more sensitive to impact damage than the heavy ones. Furthermore, damping is found to be more sensitive to damage than the stiffness variations, so it is reasonable to assume that damping may be used instead of natural frequency as a damage indicator tool for structural health monitoring purposes.     

Experimental results of transparent,reflective and absorbing properties of some building materials

This paper presents the study of the behaviour of some transparent materials, glass and plastic sheets and films, due to incidence light radiation. Transmission, reflection and absorbing coefficient variations are evaluated by experimental measurements for different incidence angles of light. To this aim two laser radiation sources have been used (a He–Ne 107S and a diode) characterised by a wavelength emission near the maximum intensity of the natural solar radiation spectrum. The comparison analysis of the experimental data acquired by linear and elliptic polarised light shows that there is no polarising effect on lighting due to the studied materials. The lines trend obtained by the experimental data has a good agreement with the analytical lines trend, obtained by a simple theoretical model.     

体积占比不同的组合式石蜡相变传热数值模拟

石蜡组合式腔体的长、宽、高均为30 mm,内部用两个长30 mm、宽1.5 mm、高30 mm的铜板分割成3个腔体层,每个腔体层填充不同相变温度的石蜡.组合式腔体左壁面为加热面,其余壁面均绝热.在组合式腔体长、宽、高均不变的情况下,通过改变各腔体层的宽度来改变石蜡的体积占比,共设置7种排布方式.排布方式1:各腔体层均填...     

Close-range blast loading on empty recyclable metal beverage cans for use in sacrificial cladding structure

This article deals with the experimental and numerical blast study on a single empty recyclable metal beverage can. The idea is to make a macro-foam (sacrificial cladding structure) out of these cans to protect the main load bearing members of civil engineering structures from the air blast load. Close-range free air blast tests have been conducted to understand the crushing behaviour and the energy absorption of a single empty beverage can in detail. To conduct such an air blast test a special small-scale test set-up was designed and manufactured. The effect of skin plate surface area and its nature on the blast parameters is studied. Furthermore, the effect of inertia of the skin plate on the crushing performance of the beverage can is evaluated. Tests have been conducted with different plates (made of aluminium and sandwich composite materials) with different masses which represent the skin plate of the proposed sacrificial structure. The measured blast parameters from the experimental tests were compared with ConWep predicted data. Furthermore, the influence of the finite surface area of the skin plate on the clearing of the reflected pressure waves was also studied. The deformation behaviour and the corresponding energy absorption of empty beverage cans were captured. During the experimental blast tests it was observed that a part of the total reflected impulse (∼30%) was lost before it transfers to the non-sacrificial structure. Hence, in order to investigate this phenomenon Eulerian-Lagrangian coupled analyses were conducted using Hydrocodes. The results from these analyses showed that the diffraction and ground reflected pressure wave caused the loss in impulse. The results from the numerical studies have been compared and validated with the experimental results.     

低温下不锈钢焊接件的抗冲击性能

以304L和316L型奥氏体和2505型双相不锈钢焊接件为对象,采用屏蔽金属弧焊与点焊方式,进行低温示波冲击试验研究,温度范围从室温至-196℃。结果表明,随试验温度的降低,304L与316L型奥氏体不锈钢焊件的冲击能量略有减小,而其相应焊条的冲击能量有很大减小。随着双相不锈钢焊件与焊条从韧性向脆性的转变,其冲击能量减小了至少5%。从试件的断裂面可看出,奥氏体不锈钢焊件与焊条呈现韧性断裂形态,出现宽深式、窄深式、浅式凹陷;而双相不锈钢焊件与焊条呈现脆性断裂形态,出现大、小延展层断面。依据荷载-时间曲线,说明奥氏体与双相不锈钢的韧性与脆性断裂性能。从控制不锈钢低温下变形机理的主要参数:堆垛层错能,应变诱发马氏体相变及铁素体相变这些方面,探讨两种不锈钢性能的差异。     

定形相变材料的制备及对混凝土耐高温性能的影响

为了提高混凝土结构的耐高温性能,从混凝土自身的储热性能出发,制备了一种定形相变材料,并研究了该相变材料对混凝土导热性能和高温后力学强度的影响。结果显示:硫酸铝铵掺量越高,相变材料的相变焓越大,当其掺量超过70%时,差示扫描量热法(DSC)特征参数趋于稳定;定形相变材料具有较好的热稳定性,且高温下硫酸铝铵和SiO2并未发生化学反应;相变材料的加入能提高混凝土的储能密度,降低其导热系数,混凝土内部的温度随相变材料掺量的增多而逐渐降低;当相变材料掺量小于6.5%时,相变材料的加入能明显提高混凝土高温后的强度,而当相变材料掺量大于6.5%时,再提高其掺量对混凝土耐高温性能的改善作用有限。     

地下洞穴对表面波表观相速度影响的数值分析

通过有限元数值模拟，得到了含洞穴固体介质在动荷载下表面质点的速度响应。根据表面质点响应中瑞利波和反射体波能量分配分析表观相速度扰动机制，讨论振源、测点、洞穴三者相对位置及频率对表面波表观相速度影响。表观相速度扰动程度随频率减小而增加，商至出现大扰动。大扰动峰值频率与反射波基频有关，基频随振源、测点及洞穴间相对位置变化。最后讨论由大扰动峰值波长与洞穴埋深关系，并给出洞穴埋深估算方法。     

Development of realistic design fire time-temperature curves for the testing of cold-formed steel wall systems

Fire resistance rating of light gauge steel frame (LSF) wall systems is obtained from fire tests based on the standard fire time-temperature curve. However, fire severity has increased in modern buildings due to higher fuel loads as a result of modern furniture and light weight constructions that make use of thermoplastics materials, synthetic foams and fabrics. Some of these materials are high in calorific values and increase both the spread of fire growth and heat release rate, thus increasing the fire severity beyond that of the standard fire curve. Further, the standard fire curve does not include a decay phase that is present in natural fires. Despite the increasing usage of LSF walls, their behavior in real building fires is not fully understood. This paper presents the details of a research study aimed at developing realistic design fire curves for use in the fire tests of LSF walls. It includes a review of the characteristics of building fires, previously developed fire time-temperature curves, computer models and available parametric equations. The paper highlights that real building fire time-temperature curves depend on the fuel load representing the combustible building contents, ventilation openings and thermal properties of wall lining materials, and provides suitable values of many required parameters including fuel loads in residential buildings. Finally, realistic design fire time-temperature curves simulating the fire conditions in modern residential buildings are proposed for the testing of LSF walls.     

太阳能通风结合相变墙在苏北沿海的应用研究

结合苏北沿海地区的气候特点,通过对苏北沿海代表性城市盐城地区的室外温度、太阳光线强度等外部环境展开分析,选择相变温度以及潜热较为合理的相变材料展开实验,从而了解太阳能烟囱以及相变蓄热墙在改变室内热环境和针对负荷所表现出的削峰移峰2个方面影响作用。实验结果显示,在盐城同样的室外温度环境下,采用相变墙的房间具有明显的隔热保温作用,有效提升了室内环境的舒适度。充分说明,相变房温度条件得到了改善,房间给人更高的舒适感,降低了空调负荷,达到了节约能源的目的。     

Study on the influence of retroreflective materials on the “secondary reflection” on the room above the horizontal sunshade

Existing studies on horizontal sunshade systems mainly focus on the influence of the sunshade on the room under or inside the sunshade systems. Meanwhile, the top surface of horizontal sunshade, especially those with mirror surface or made of metal, reflects solar radiation into the indoor and surroundings, resulting in “secondary reflection”. This paper mainly focuses on the influence of secondary reflection on the room above the sunshade, using Design-Builder software to conduct numerical simulation analysis and building architectural model for field measurement. Results from simulation and field measurement both prove that mirror materials increase secondary reflection reflected into the indoor. Moreover, results from experiments show that retroreflective materials decrease secondary reflection reflected into the indoor. At low latitude, the application of retroreflective materials on the top surface of horizontal sunshade effectively reduces the adverse influence of secondary reflection on the room above the sunshade.