Erratum to: Textile Reinforced Concrete: experimental investigation on design parameters

Textile Reinforced Concrete (TRC) is an advanced cement-based material in which fabrics used as reinforcement can bring significant loads in tension, allowing architects and engineers to use thin cross-sections. Previous research projects, developed during the last 10 years mainly in Germany, Israel and the USA, have shown the capabilities of such a material. In this paper an extensive experimental investigation of TRC is presented: tensile tests were carried out to obtain a complete mechanical characterization of the composite material under standard conditions, considering the influence of different variables such as reinforcement ratio, fabric geometry, curing conditions, displacement rate and specimen size.     

Influence of experimental setups on the apparent uniaxial tensile load-bearing capacity of Textile Reinforced Concrete specimens

An important parameter for dimensioning of Textile Reinforced Concrete (TRC) structures and structural elements is the tensile load-bearing capacity of the composite. Respective values are usually derived from uniaxial tensile tests with overcritically reinforced TRC specimens. In this paper, influences from specimen geometry, e.g. plane and waisted specimens, and load application design, e.g. stiff glued steel plates or soft clamping constructions are investigated. Therefore, experimental results regarding the load-bearing capacity of the composite are statistically evaluated. The experimental observations are supported by results of numerical simulations with a one-dimensional model based on the Finite Element Method. These simulations provide stress distributions in concrete and reinforcing fibres as well as the tensile load-bearing capacity. Based on these results existing test setups for the derivation of the load-bearing capacity of the composite for dimensioning are assessed. As a result, plane plate specimens with a load application by means of friction is recommended for experimental determination.     

氯盐干湿环境下TRC与老混凝土的界面特性研究

采用双面剪切的加载方式研究了氯盐干湿循环对纤维编织网增强混凝土(Textile reinforced concrete,TRC)与普通硅酸盐混凝土界面性能的影响,并通过SEM(Scanning electron microscope)技术探究了氯盐干湿循环作用下界面的微观结构。研究发现:氯盐干湿循环下,TRC与老混凝土界面微观结构会损伤劣化;与连续氯盐浸泡相比,氯盐干湿循环对界面粘结性能的影响较大;相同干湿循环次数下,加固界面的粘结强度随着氯盐溶液浓度的增加而降低;相同氯盐溶液浓度下,加固界面的粘结强度随着循环次数的增加而降低。     

Flexibility and manufacturing system design: An experimental investigation

Manufacturing industries today are faced with steady and unrelenting changes to the environment in which they operate. In order to survive and profit, manufacturing facilities must be designed such that they exhibit desirable system-level flexibility characteristics. The relationships between flexibility and manufacturing system design, however, remain largely unexplored. This paper investigates the effects of manufacturing system design on product, mix, production, and volume flexibilities, and on trade-offs between these flexibility types, for different product environments. Of particular concern is the determination of whether or not flexibility trade-offs can be avoided, and if so, how. Simulation experiments are performed to determine flexibility values for 16 different manufacturing system design 'approaches' and two levels of part processing flexibility. A total of 800 different manufacturing system/product set combinations are investigated. The results indicate that the effects of manufacturing system design on flexibility are not always intuitive, and that they can change depending upon the level of part processing flexibility present. In addition, however, they show that flexibility trade-offs are not inevitable: multiple flexibility types can be increased in value simultaneously through proper selection of the design approach.     

The investigation of treatment design parameters on carbon integration networks

Carbon Integration methods help identify the appropriate allocation of captured carbon dioxide (CO₂) streams into CO₂-using sinks, and are especially useful when a number of CO₂ sink options are present simultaneously. The method helps identify CO₂ allocation scenarios when subjected to an emission target on the CO₂ overall network. Many carbon dioxide sink options are costly, and more often than not, require a high purity carbon dioxide source to satisfy the sink demand. Hence, it is imperative to effectively incorporate treatment units in such networks, to obtain high-purity CO₂ streams. In fact, it has been previously reported in many studies that the most expensive step in Carbon Capture, Utilization and Sequestration (CCUS) is the treatment system. As a result, this paper focuses on reassessing the performance of carbon integration networks using a more rigorous cost model for the treatment design stage. The effect of utilizing different treatment operating conditions on the overall cost of the treatment stage of CO₂ (before allocation) is first captured using a detailed cost model. Subsequently, this information is then fed into a network design problem that involves a CO₂ source-sink allocation network problem, and different CO₂ net capture targets within the network. For this, an enhanced treatment model that captures all necessary treatment design parameters has been utilized alongside the original model. The original carbon integration formulation has been adopted from previous work. Many of the cost items have been lumped into single parameters in the original formulation, and lack the necessary depth required to carry out the necessary investigations for this work. Hence, the treatment model introduced in this paper is more rigorous, as it accounts for important technical performance constraints on the system to be assessed. Utilizing a more detailed cost model was found to be very helpful in understanding several effects of varying parameters on the overall source-sink allocations, when subjected to different CO₂ net emission reduction targets. The cost of the carbon network increases when the solvent temperatures are increased. However, there was a noticeable linear trend at lower temperatures compared to higher temperatures, where the increase became non-linear. Furthermore, it was discovered that for net capture targets of 20% and 25%, no revenue from carbon storage could be generated beyond a solvent temperature of 25 °C. Additionally, the optimal diameter of the treatment column was more responsive to changes in solvent temperature for cases with low net capture targets (below 10%), while its sensitivity decreased for higher capture targets (above 10%).

Graphical Abstract

     

Computer-aided design and experimental investigation of a hydrodynamic device: the microwire electrode

The development and application of a new electrochemical device using a computer-aided design strategy is reported. This novel design is based on the flow of electrolyte solution past a microwire electrode situated centrally within a large duct. In the design stage, finite element simulations were employed to evaluate feasible working geometries and mass transport rates. The computer-optimized designs were then exploited to construct experimental devices. Steady-state voltammetric measurements were performed for a reversible one-electron-transfer reaction to establish the experimental relationship between electrolysis current and solution velocity. The experimental results are compared to those predicted numerically, and good agreement is found. The numerical studies are also used to establish an empirical relationship between the mass transport limited current and the volume flow rate, providing a simple and quantitative alternative for workers who would prefer to exploit this device without the need to develop the numerical aspects.     

Multi-Scale Modelling and Simulation of Textile Reinforced Materials

Novel textile reinforced composites provide an extremely high adaptability and allow for the development of materials whose features can be adjusted precisely to certain applications. A successful structural and material design process requires an integrated simulation of the material behavior, the estimation of the effective properties which need to be assigned to the macroscopic model and the resulting features of the component. In this context two efficient modelling strategies - the Binary Model (Carter, Cox, and Fleck (1994)) and the Extended Finite Element Method (X-FEM) (Moës, Cloirec, Cartraud, and Remacle (2003)) - are used to model materials which exhibit a complex structure on the mesoscale. For these investigations the focus is set on composites made of glass fibers, thermoset or thermoplastic matrices and on the application of commingled thermoplastic and glass fibers. Homogenization techniques are applied to compute effective macroscopic stiffness parameters. Problems arising from a complex textile reinforcement architecture, e.g. bi- or multi-axial weft-knit, woven and braided fabrics, in combination with a high fiber volume fraction will be addressed and appropriate solutions are proposed. The obtained results are verified by experimental test data. The macroscopic stress and strain fields in a component are used for optimization of the construction and the material layout. These distributions are computed in a global structural finite element analysis. Based on the global fiber orientation the required macroscopic material properties obtained from homogenization on the meso-scale are mapped to the model of the structural part. The configuration of the fiber-orientation and textile shear deformation in complex structural components caused by the manufacturing process is determined by a three-dimensional optical measurement system.     

Preliminary investigation on the design of biodegradable microparticles for ivermectin delivery: set up of formulation parameters

The aim was to design sterile biodegradable microparticulate drug delivery systems based on poly(dl-lactide) (PLA) and poly(?-caprolactone) (PCL) and containing ivermectin (IVM), an antiparasitic drug, for subcutaneous administration in dogs. The drug delivery system should: (i) ensure a full 12-month protection upon single dose administration; (ii) be safe with particular attention regarding IVM dosage and its release, in order to prevent over dosage side effects. This preliminary work involves: polymer selection, evaluation of the effects of γ-irradiation on the polymers and IVM, investigation and set up of suitable microparticle preparation process and parameters, IVM-loaded microparticles in vitro release evaluation.

Results of gel permeation chromatography analysis on the irradiated polymers and IVM mixtures showed that combination of IVM with the antioxidant α-tocopherol (TCP) reduces the damage extent induced by irradiation treatment, independently on the polymer type.

Solvent evaporation process was successfully used for the preparation of PLA microparticles and appropriately modified; it was recognized as suitable for the preparation of PCL microparticles. Good process yields were achieved ranging from 76.08% to 94.72%; encapsulation efficiency was between 85.76% and 91.25%, independently from the polymer used. The type of polymer and the consequent preparation process parameters affected microparticle size that was bigger for PCL microparticles (480–800?µm) and solvent residual that was >500?ppm for PLA microparticles. In vitro release test showed significantly faster IVM release rates from PCL microparticles, with respect to PLA microparticles, suggesting that a combination of the polymers could be used to obtain the suitable drug release rate.     

A theoretical and experimental investigation of the parameters for an electric arc

A new method is presented for the determination of the temperature distribution over the cross section of a cylindrical arc, as well as of the volt-ampere characteristics, and these are compared with experimental data.     

钢筋混凝土腐蚀研究综述

综合探讨了混凝土中钢筋腐蚀的机理、影响因素及其检测方法,以及腐蚀结构的耐久性评定和使用寿命预测,通过分析提出了混凝土钢筋腐蚀研究的难点以及今后的重点研究方向。     

钢筋混凝土粘结滑移研究综述

钢筋混凝土(Reinforced concrete, RC)作为近现代土木工程领域中最重要的组合材料,在实际工程中得到了大量应用。钢筋与混凝土之间良好的粘结性能是保证RC结构服役性能的关键,影响着RC结构生命周期不同阶段的力学性能。然而,由于钢筋混凝土界面粘结滑移关系十分复杂,且涉及多种变量,因而实际结构分析中一般忽略了粘结滑移对RC结构整体力学性能的影响,即认为二者间完全粘结,忽略了二者间的相对滑移,从而导致分析结果与实际存在较大偏差。 迄今为止,国内外学者基于大量试验研究,综合考虑影响钢 筋混凝土粘结性能的多种因素,建立了相应的粘结滑移本构关系及模型。在此基础上,一些学者则结合试验研究与理论分析,建立了钢筋混凝土粘结滑移的理论模型和数值模拟方法,通过将其带入结构分析以考虑粘结滑移效应,从而提高了对结构响应的模拟精度。因此,准确揭示钢筋与混凝土间的粘结失效机理及其影响因素,表征各因素对钢筋混凝土粘结性能的影响规律,建立相应的粘结滑移本构关系和数值模拟方法,并将其应用于实际结构分析中,是提高分析结果精度、改善整体结构受力性能的前提。 鉴于此,本文综合国内外相关研究成果,分别从粘结机理、试验研究、理论和数值模型三个角度出发,对钢筋混凝土粘结滑移研究现状展开了详细综述。首先,在粘结滑移关系表征及其破坏机理方面,简要分析了粘结应力计算方法、粘结滑移本构关系建立及粘结破坏模式。在试验研究方面,详细描述了国内外相关试验研究和基于试验建立的粘结滑移本构关系,并对影响粘结性能的各种因素进行了归纳总结。在模型分析方面,具体介绍了粘结滑移的理论模型及数值模型,并将数值建模方法划分为直接模拟法和间接模拟法,进而简要分析了两种方法的优缺点和适用性。最后,对该研究方向中存在的不足以及进一步研究的趋势进行了分析,指出考虑钢筋锈蚀、冻融循环等环境因素耦合作用影响的粘结滑移问题是未来钢筋混凝土粘结滑移研究的重点方向,在后续工作中需要借助更加广泛的试验研究及理论分析来丰富该领域研究,以期进一步完善混凝土基本理论体系,并为实际工程结构的耐久性提供参考。     

浅析钢筋混凝土构件的安全鉴定

如何鉴定裂缝、分析裂缝、控制裂缝,是安全鉴定工作的重要内容之一.根据裂缝成因和特征,判断结构受力工作状况,评定结构的安全性、适用性和耐久性.并对可疑结构构件应进行强度、刚度、抗裂性验算,必要时还应通过进行荷载试验,然后作出安全鉴定意见.     

钢筋混凝土微平面动态本构模型

在B．P．Bazant等人提出的混凝土微平面模型基础上通过引入钢筋的影响提出了一个钢筋混凝土动态本构模型。本构模型的建立通过平行耦合假定考虑钢筋和混凝土的相互作用。混凝土模型采用能反映各种复杂受力行为并被充分验证的M5微平面模型，钢筋采用Cowper—Symonds型率相关的双线性模型。最后参照M4微平面模型对应变率效应的处理方法，将提出的钢筋混凝土模型推广到动态模型范畴。此模型可适合钢筋混凝土的静力、动力显式分析。     

海港码头钢筋砼沉箱群阴极保护的研究与应用

某１０＊１０＾４ｔ级油码头由１９只钢筋砼沉箱和钢质架管桥组成。采用区域性外加电流法,对沉箱的海水全浸区进行连续的阴极保护,而对其潮差区进行断续的阴极保护。被保护面积约１２２５０ｍ＾２,钢筋总面积约４０００ｍ＾２。研究了开发了成大的专用阴极保护装置,试验了强弱交叉极化的方法。实际运行一年后的检测结果表明,有保护的钢筋比未保护的其耐腐蚀能力提高４．７－６．１倍,而锈蚀率降低为１／１４。．     

钢筋混凝土烟囱的爆破拆除

本文介绍了由于受烟囱本身结构特点和周围环境的原则，对钢筋混凝土烟囱的上部采用定向倾倒爆破拆除；下部采用水压爆破拆除的设计和施工方法。     

钢筋混凝土烟囱拆除切口中脊高度的计算

拆除钢筋混凝土烟囱时,拆除切口中脊高度的合理选择是拆除成功的重要因素。根据钢筋混凝土烟囱在倒塌至拆除切口闭合时,倾覆力矩大于薄弱面的抵抗力矩的原则来确定钢筋混凝土烟囱定向倒塌的条件及拆除切口中脊高度对其定向倒塌的影响。在考虑烟囱是变截面筒体的情况下,通过对上述条件的分析,得到拆除切口中脊高度的计算公式,与烟囱的结构尺寸、拆除切口薄弱面位置、拆除切口所对圆心角、余留支撑体轴筋承受的拉力有关,不仅仅与烟囱的壁厚有关,与传统的经验公式是有较大差别的。     

Study of Acoustic Surface Waveguides on Reinforced Concrete Slabs

This paper describes the development of a two-dimensional acoustic surface waveguide system to enhance the transmission of Acoustic Emission (AE) signals in high attenuation concrete materials. The design of the surface waveguide system and the AE source location results are described. In this study, steel wires were selected as a waveguide material and were attached on the surface area of reinforced concrete structures. AE sensors were mounted at the end of the waveguides. The waveguides were connected to a concrete slab at joints with small contact areas using epoxy. This minimizes the amount of AE energy that could dissipate back to concrete. Thus, AE signals can be transmitted a longer distance. Experiments using standard pencil-lead breaks were conducted at 49 locations on a surface of a reinforced concrete floor slab to provide artificial AE signals. High transmission efficiencies were experimentally determined for the epoxy joints developed to attach the waveguides on the concrete surface. Results confirm that the use of the two-dimensional surface waveguides can significantly increase the AE monitoring range. A multi-layer Neural Network (NN) system was employed to predict locations of the AE sources. Four data sets of AE parameters and their corresponding 49 source locations in each data set were used to train the NN system. A testing data set was then used to demonstrate the ability of the NN in identifying the locations of the AE sources. Satisfactory prediction results from the NN were obtained.     

Using experimental design to optimize the process parameters in fluidized bed granulation

In this study many parameters were screened for a small-scale granulation process for their effect on the yield of granules between 75 and 500 μm and the geometrical granule mean size (d50). First a Plackett-Burman design was applied to screen the inlet air temperature, the inlet flow rate, the spray rate, the nozzle air pressure, the nozzle spray diameter, and the nozzle position. The Plackett-Burman design showed that the key process parameters were the inlet flow rate and the spray rate and probably also the inlet air temperature. Afterward a fractional factorial design (2^5-2) was applied to screen the remaining parameters plus the nozzle aircap position and the spraying time interval. The fractional factorial design showed that the nozzle air pressure was also important. As the target values for the granule yield (between 75 and 500 μm) and the geometric mean granule size (between 300 and 500 μm) were reached during the screening experiments, further optimization was not considered necessary.