电化学噪声直流漂移的分段多项式拟合消除

在电化学噪声用于工业现场腐蚀监测过程中,如何从大量原始信号中有效去除直流漂移并恢复有用信号,具有重要意义。本文提出了一种多段m次多项式拟合法,以消除噪声数据中直流漂移成分,并采用小波分析法对消除结果的正确性进行了讨论。通过对0.5 mol/L NaCl体系中产生的噪声数据进行处理表明,窗口大小和多项式的最高方次共同影响低频数据的消除结果以及能量分布谱（EDP）的波动特征,窗口大小由腐蚀特征决定,而多项式最高方次不宜超过3。与多项式拟合法相比,分段多项式拟合法具有较高的灵活性。     

Determination of partial factor for model uncertainty for unreinforced masonry shear walls

Experiments in structural engineering can play an important role in the prediction and characterization of the material properties and behaviour of structural components. In order to cover all aspects in tests and use the results for design purposes, several methods have been included in EN 1990 Annex D for design based on test data. The calculation of characteristic values and design values for material resistance are the main aspects. In this study, the recommended methods in Annex D of EN 1990 for resistance of the material will be used to extract the partial safety factors for masonry structures based on the formulation of design and characteristic values. A database including more than 100 tests on unreinforced masonry shear walls will be used to evaluate the results. The resistance model for shear walls based on the recommendation in the Eurocode will be compared with the test results. The main aim will be to compare the model prediction and the test results. Deviation of the prediction from the test is caused by model error or model uncertainty. The test database includes results for three types of masonry units – fired clay, calcium silicate and autoclaved aerated concrete. The evaluation of partial factors for masonry shear models will be undertaken based on the scatter and the model bias for the whole database. Further analysis will also be performed for each type of masonry unit for classification of the outcome.     

Erhöhung der Tragfähigkeit von GV‐Verbindungen durch den Einsatz von Klebstoff

Use of adhesives to increase the load‐bearing capacity of slip‐resistant connections. Slip‐resistant connections are preferred for steel constructions if subjected to fatigue loads and/or load reversals, no slip in the connection is permitted and joining on construction site is necessary. These connections are prepared with a high manufacturing effort due to the intensive preparation of the faying surfaces, or the contact area between the steel plies and it must receive special consideration in design and coating application. The typical corrosion protection for steel structures is still the hot‐dip galvanizing. The follow‐up work of the faying surfaces for a use in slip‐resistant connections is related to a high effort and guarantees no high slip factors. Furthermore the slip factor may deviate more or less high with the properties of the zinc layer. Against this background, investigations have been carried out in a recently concluded research project which show an increase in the load bearing capacity of slip‐resistant connections by the combined use of adhesive. In the case of the process combination, which is also referred and named as a preloaded hybrid connection, the applied preload of the high‐strength bolts is responsible for the considerable increase in load bearing capacity compared to the elementary joining processes – adhesive bonding or just slip‐resistant connections. If the two methods are carefully combined, the individual load bearing capacities can approximately add up.     

Lastkollektive für Eisenbahnbrücken aus Messdaten

Load spectra for railway bridges from measurement data – Part 1: systematic investigations into damage equivalent factor λ₁ on single span girders. The rapid progress in the evolution of memory device leads to an increasing data‐gathering. This offers new opportunities to define fatigue loads for railway bridges by systematic evaluations. So far, the definition of load spectra based on predefined trains and traffic mix was the only approach, but now it can be done much more detailed but even more CPU‐intensive by using influence data over a long period of time. This article shows practical results of this new approach for building load spectra by using systematic calculations on single span girders together with short theoretical explanations. The used influence data provided by the Österreichischen Bundesbahnen result in significant differences comparing to standardized values. Part 1 of this article includes exclusively the damage equivalent factor λ₁ while the second part includes the damage equivalent factors λ₂ and λ₃ as well as the threshold value λ_max and a model with respect to traffic trends.     

Plastische Querschnittstragfähigkeit von quadratischen und rechteckigen Hohlprofilen

Plastic resistance of square and rectangular hollow sections. The plastic resistance of rectangular hollow sections is usually determined by using approximation formulae or simplified models. These approximations lead to a accuracy, which depends on the dimensions h, b, t and the size of the rounded corners. Applying these approximations the plastic resistance is sometimes significantly under‐ or overestimated. The present paper deals with the development of verifications and simplified approximations of high accuracy for the plastic resistance. The new procedures are qualified for the analysis of any combination of the internal forces and moments N, V_y, V_z, M_x, M_y and M_z. In addition the verifications according to DIN EN 1993‐1‐1 are modified concerning the accuracy and the expansion of the application area.     

Kennwerte neuer und abgenutzter Kranschienen für die Bemessung von Kranbahnträgern

Properties of new and used crane rails for the design of crane runway girders. The contribution of crane rails to the load carrying behaviour and the static design of crane runway girders can be taken into account, providing a certain structural detailing. In doing so, an abrasion of 25 % has to be considered at the ultimate limit state and of 12,5 % for fatigue assessments according to EN 1993‐6 (Eurocode 3 Part 6). Different cross section properties regarding new and used rails are specified in literature, which partially show certain discrepancies to each other. With this paper, a clarification is supposed to be given and for the first time a compilation of all properties, meaningful for an application according to EN 1993‐6. The demand has been recognized by an increasing request for these values from practice as well as research.     

Vollständige äquivalente Imperfektionsmethode für biege‐ und druckbeanspruchte Stahlträger

Overall imperfection method for flexure and compression steel beam‐columns. The principles and applications of the overall (global) imperfection method (OIM) for beam‐columns are presented in this paper. The buckling resistance of a beam‐column member is determined by the resistance of its critical cross‐section taking into account second‐order effect of the eigenform equivalent initial imperfection. The maximum amplitude of this initial imperfection, in the shape of elastic buckling mode, is determined from fundamental cases, which are simply fork supported members with uniform cross‐section under uniformly distributed normal force or bending moment. The standardized buckling resistance of the fundamental cases is based on theoretical and empirical background. The proposed global imperfection method is adequate for computer‐aided design method using advanced elastic beam‐column finite element method including the warping behavior of the cross section. The accuracy of the presented method is illustrated step‐by‐step with numerical examples.     

Wind loads on curved roofs

Curved roofed buildings are increasingly used in the modern built environment because they offer aerodynamically efficient shapes and provide architects and designers with an alternative to regular rectangular building forms. However, there is little information available on the wind loads on these roof forms. The Eurocode for wind actions (EN1991-1-4) includes pressure coefficients for a limited range of aspect ratio cylindrical roofs from measurements in low-turbulence conditions but only for wind blowing normal to the eaves. There is some concern regarding the reliability of these data, consequently EN1991-1-4 allows National Choice (National Determined Parameter) for wind loads on these roofs. This paper describes a series of parametric wind tunnel studies undertaken at BRE to measure wind pressures on a wide range of curved roof models in a properly scaled atmospheric boundary layer simulation and gives an alternative to the EN1991-1-4 recommended procedure.     

火灾中不锈钢柱和梁的屈曲

材料特性和它们对高温的反应构成结构防火设计的关键部分。当遇到高温时,与碳钢相比,不锈钢表现出更好的材料强度和刚度。尽管独立而言,强度和刚度都很重要,但是在高温作用下,它们之间的关系同样也会对结构构件的屈曲反应产生显著影响。检查了现有的试验结果,并且介绍了数值参数研究的结果,即利用ABAQUS对火灾中的不锈钢柱进行分析。由于对局部和整体初始几何缺陷的敏感,通过冷作和对柱端的局部保护可以提高焊脚强度。为探究局部横截面长细比、整体构件长细比和荷载变化的影响,还进行了参数研究。试验结果与现有设计规范欧洲规范3(part1.2),欧洲Inox/SCI设计手册中对结构不锈钢的规定及CTICM/CSM中提到的规定相对比。分析了在全部23个柱屈曲抗火试验中,6个短柱和6个梁的抗火试验结果。文中标出过度保守和互相矛盾的结果以及变形极值。通过修订,可以使得今后不锈钢梁和柱能在火灾中更有效的使用。改进后,柱的抗屈曲能力提高了6%,短柱的抵抗能力提高28%,平面内抵抗弯矩提高14%,高于现有欧洲规范的要求。