Bemessung von Fundamentplatten aus Stahlfaserbeton gemäß ÖVBB Richtlinie Faserbeton und DBV Merkblatt Stahlfaserbeton

Static Analysis and Verification of Steel Fibre Reinforced Concrete Foundation Slabs according to the Austrian Guideline “Fibre reinforced concrete” and DBV (German Concrete Association) Recommendations “Steel fibre reinforced concrete” Steel fibre reinforced concrete is used for foundation slabs of housing structures since many years. The Austrian guideline [1] and the DBV recommendations [2] provide material properties and design values for calculation and verification of steel fibre reinforced concrete structural members. This paper provides a comparative study on foundation slabs taking both guidelines into account. A nonlinear finite element parameter study has been performed in order to verify a simplified static calculation and verification method. This calculation method is based on the yield line theory. This paper concludes with a sample calculation for steel fibre reinforced foundation slabs according to the Austrian and German design recommendations.     

Versuche an genieteten Brückenlängsträgern – Statisches Verhalten,Ermüdungsfestigkeit und Rissausbreitung

Tests on riveted bridge stringers – behaviour under static loads, fatigue strength and crack propagation. The assessment of the load‐carrying capacity and of the remaining fatigue life of existing railway and road bridges has gained an increasingly significant role over the last years. Thus, the problem of determining adequate strength values of riveted members of older steel bridges once again arose during the elaboration of the ONR 24008 specification. In the course of a research project initiated by the Austrian Federal Railways (ÖBB), static and fatigue tests were carried out on riveted members taken from a demolished railway bridge in Salzburg. The results of these tests gave further insight into the load carrying behaviour of built‐up riveted members, particulaly the progagation of fatigue cracks.     

Baustähle im konstruktiven Ingenieurbau

Structural Steels in structural engineering. Reliability and maximum dimensions of structures of structural engineering are among others determined by the characteristic of the used materials. The material characteristic from the in steel structure used products can be exactly adapted to the particular demands. For the low alloyed ferritic structural steels the most common methods of strength increase are described. The fabrication conditions and the terms of use can influence the ductility of the steel according to the manner of the applied method differently. To eliminate inadmissible risks limitations for the materials regarding the operating conditions, dimensions and methods of handling are necessary. In Germany such limitations for buildings are fixed in the technical building regulations. This essay shall demonstrate the different strength increasing influences and therefore it shall increase the understanding of adherence the material‐conditioned limitations. For cases where the limitations differ from the conditions background information are pointed out to facilitate evaluation in individual cases (“Zustimmung im Einzelfall”).     

Beurteilung des Ermüdungsverhaltens von Krankonstruktionen bei Einsatz hoch‐ und ultrahochfester Stähle

Analysis of fatigue details typically used in crane structures. For joints and attachments in crane structures usually the verification of the fatigue strength governs the design. When using the nominal stress approach some details often used in crane structures, especially welded details, cannot be classified according to the tables of fatigue classes given in the standards. Together with representatives from the crane industry such details have been identified. In the frame of the FOSTA research project P 512 fatigue tests have been carried out, so that proposals for the classification according to Eurocode 3 could be made. In addition, fatigue tests on structural details already covered by the codes have been executed to check the influence of material strength. A general increase of the fatigue strength when using high strength steel could not be observed but details with low notch effects show a better behaviour compared with normal strength steel. This is attributed to higher fabrication qualities. The research project P 512 was funded by the Stiftung Stahlanwendungsforschung, Essen, and has been carried out in behalf of the Forschungsvereinigung Stahlanwendung e.V.     

Statistisch begründete Festigkeitskennwerte genieteter Bauteile – statische Festigkeit und Wöhlerlinienkatalog

Statistically founded strength values of riveted members – static strength and fatigue life classification of constructional details. The assessment of the load‐carrying capacity and of the remain‐ing fatigue life of existing railway and road bridges has gained an increasingly significant role over the last years. Thus, the problem of determining adequate strength values of riveted members of older steel bridges once again arose during the elaboration of the ONR 24008 specification. In the course of a research project initiated by the Austrian Federal Railways (ÖBB), results of static and fatigue tests carried out on riveted members were evaluated statistically. With regard to fatigue test data, a classification of riveted details with consideration of different constructional details proved to be sensible and to lead to more consistent S‐N design curves. Tables containing static strength values and a catalogue of S‐N design curves based on constructional detail classifications represent the result of the research project.     

Einsatz von hochfesten Stählen und Betonen bei Hohlprofil‐Verbundstützen

Composite columns made of high‐strength steel and high‐strength concrete. The paper deals with the use of composite columns made of high‐strength steel and high‐strength concrete. Based on the design methods in Eurocode 4‐1‐1 and DIN 18800‐5 a simplified design method is presented for composite columns with high strength concrete and high strength steel in combination with massive inner steel core‐profiles. The ultimate strength of these special type of columns is significantly influenced by the residual stresses in the core profiles resulting from the cooling process during fabrication. Based on Finite Element studies new models are presented for the determination of the distribution of residual stress taking into account the steel grade, the dimensions of the core profiles and the cooling conditions during fabrication.     

Zur Korrosionsschutzwirkung von organischen Beschichtungssystemen auf gestrahlten Stahloberflächen

Corrosion protection of organic protective coat systems on blast cleaned steel surfaces. The paper reports about the effects of three surface preparation methods upon the protective performance of five typical organic corrosion protection coating systems. The surface preparation methods include dry blast cleaning and high‐pressure water jet cleaning as well as a modified wet blast cleaning method. The properties of the plain steel substrates immediately after cleaning and the performance of the coating systems are assessed under standard test conditions. Important selection criteria, namely disbonding after salt spray testing and adhesion strength, are not material parameters but rather system parameters, which depend predominantly upon the cleanliness of the prepared steel surfaces.     

高强无机锚固材料的实验研究

研制一种新型的无机锚固材料,作为植筋胶的替代品。通过试验确定无机锚固材料的配合比,并对其抗压强度、与混凝土的粘结强度、体积稳定性、对钢筋的锚固力进行研究。所研制的无机锚固材料的早期强度高,1 d强度达到38.5 MPa,3 d强度达到60 MPa以上;与混凝土有较高的粘结强度,28 d的粘结强度在2 MPa左右;所研制的锚固材料随着龄期延长,会产生微小的体积膨胀,有利于提高锚固力。所研制的锚固材料是以水泥基材料为主要成分的无机锚固材料,克服了有机高分子材料耐久性差、施工条件要求严格等缺点,试验证明此材料具有早强高强、与混凝土粘结良好、能够产生微小的体积膨胀等特点,能够满足植筋施工和承载力的要求,可以替代植筋胶使用。     

Zur plastischen Bemessung hochfester kammerbetonierter Verbundträger

Plastic design method for high‐strength partially concrete encased composite beams. Partially concrete encased composite beams offer numerous advantages compared to conventional composite beams consisting of a steel beam and a concrete slab. In many cases these advantages are not used because of missing practicable design models. In the current paper the load bearing behaviour and the rotation capacity of partially concrete encased composite beams made of high strength steel and concrete is investigated using experimental tests and parametric studies. At first the influence of high strength concrete encasement and high strength structural steel on the cross section capacity is described. Taking into account the stress‐strain distribution of high strength concrete and steel a new plastic design method for partially concrete encased composite beams was affiliated. The experimental and theoretical results are documented in the research report [1] and the dissertation [2].     

国产超高强钢Q890高温力学性能试验

通过稳态拉伸试验法对国产超高强钢Q890在不同火灾高温条件下的力学性能进行了试验研究,得到高温下钢材的力学性能参数、应力-应变关系曲线和试验现象,并将所得试验结果与钢结构抗火设计规范及相关超高强钢研究文献中高温材料模型结果进行比较。分别采用多项式模型和钢材高温通用材料模型对试验结果进行数值拟合,建立高温下Q890钢力学性能参数的材料模型。结果表明:不同温度条件下的Q890钢试件在试验后有明显不同的外观特征,相应的应力-应变关系曲线基本形状差异较大;当受热温度低于500 ℃时,弹性模量和强度随温度升高逐步减小,断后伸长率变化不大;超过500 ℃后,弹性模量和强度下降速率明显加快,断后伸长率急剧增大;所建立的模型为研究Q890钢结构抗火性能及其计算方法提供理论基础。     

Ermüdungsverhalten von Mobilkranbauteilen aus hochfesten Baustählen

Fatigue behaviour of component sections of mobile cranes out of high strength steel plates. High‐strength structural steels with 960 and 1100 MPa minimum yield strength allow a decrease of the investment and operating costs of mobile cranes through lightweight design. However, there still exists an uncertainity for stress resistance under cyclic loads and bearable stresses concerning fatigue behaviour of important crane components. This paper deals for the first time with the fatigue behaviour of crane components examined under realistic load‐time‐cycles derived from realistic crane operating conditions. The results supply important information as they indicate that the service life for both steels, even with very high applied stress, is at least 20years. Moreover, it is shown that further improvements of the durability are possible around up to 50% through subsequent treatment of the welds, toughness improvement of the base material and constructive remodelling of the components. Additionally, this paper provides a new design method with which the fatigue behaviour of crane components under most different aspects and involved variable combinations can be estimated, consistent with measured values, through a fracture mechanically based model. Important procedure recommendations and hints can be given for a more intense use of high‐strength structural steels for practical application in mobile crane engineering. Inspection intervals and contents can be newly determined.     

Experimental study on the shear performance of quasi-NPR steel bolted rock joints

Quasi-NPR (negative Poisson’s ratio) steel is a new type of super bolt material with high strength, high ductility, and a micro-negative Poisson’s effect. This material overcomes the contrasting characteristics of the high strength and high ductility of steel and it has significant energy-absorbing characteristics, which is of high value in deep rock and soil support engineering. However, research on the shear resistance of quasi-NPR steel has not been carried out. To study the shear performance of quasi-NPR steel bolted rock joints, indoor shear tests of bolted rock joints under different normal stress conditions were carried out. Q235 steel and #45 steel, two representative ordinary bolt steels, were set up as a control group for comparative tests to compare and analyze the shear strength, deformation and instability mode, shear energy absorption characteristics, and bolting contribution of different types of bolts. The results show that the jointed rock masses without bolt reinforcement undergo brittle failure under shear load, while the bolted jointed rock masses show obvious ductile failure characteristics. The shear deformation capacity of quasi-NPR steel is more than 3.5 times that of Q235 steel and #45 steel. No fracture occurs in the quasi-NPR steel during large shear deformation and it can provide stable shear resistance. However, the other two types of control bolts become fractured under the same conditions. Quasi-NPR steel has significant energy-absorbing characteristics under shear load and has obvious advantages in terms of absorbing the energy released by shear deformation of jointed rock masses as compared with ordinary steel. In particular, the shear force plays a major role in resisting the shear deformation of Q235 steel and #45 steel, therefore, fracture failure occurs under small bolt deformation. However, the axial force of quasi-NPR steel can be fully exerted when resisting joint shear deformation; the steel itself does not break when large shear deformation occurs, and the supporting effect of the jointed rock mass is effectively guaranteed.     

A study on the material characteristics and the welding properties of the HSA800 steel

In this research, 7 species of material characteristics test and 9 species of welding properties test for FCAW and SAW were proceeded to confirm the various material characteristics and welding properties of HSA800 developed recently. As a result of material test, HSA800 steel satisfied the KS and the criteria of homogeneity for the strength of the steel, confirmed as sound steel having excellent directivity and toughness. Test results of the FCAW and SAW partially satisfied the KS and the criteria of homogeneity for the strength of the steel, and confirmed as having a good weld zones. However, the result of SAW weld zone chemical composition test showed that the P composition is not satisfying the KS. According to the result of weld zone rod and plate tensile test results, the FCAW 1G appeared more better than the FCAW 3G, and the SAW PH2 appeared more better than the SAW PH1.

     

Reduktion der Wanddicken bei Tragtürmen von Windenergieanlagen durch den Einsatz höherfester Stähle

Reduction of plate thickness of wind energy converters made by high strength steels. The design of wind energy converters is significantly defined by the fatigue strength of critical notch details, especially welded joints. The usage of high strength steels leads to no economical benefit because the fatigue strength of welded notch details are defined in design rules independently from the yield strength. The application of post weld treatment methods may increase the fatigue strength of these details significantly. Investigations on high frequency peening methods prove that a doubling of the fatigue strength can be achieved for steel grade S 690. An example of a connection detail is presented where it can be shown that by the application of the investigated methods together with a steel S 690 Q the plate thickness can be reduced to 45%.     

Experimental study on high strength structural steel S460 in fire and after cooling down

In order to reveal more information on material behaviour of high strength structural steel S460 both in fire and after fire, an experimental research has been carried out. The elastic modulus, yield strength and ultimate strength of S460 in fire and after cooling down are presented herein. A comparison study with current European, American, British and Australian design standards of steel structures shows that the material behaviour of high strength steel S460 in fire is different from mild steels and the current leading design standards are not applicable to high strength steel S460. This paper highlights the necessity of employing a unique elevated-temperature and post-fire material behaviour of high strength steel S460 to conduct safe fire-resistance design and evaluation after fire on steel structures with S460. Moreover, the residual material behaviour of high strength steel S460 after cooling down is found promising for its reuse.     

Effect of filler material on local and global behaviour of buckling‐restrained braces

The nonlinear response of buildings has attracted a tremendous amount of attention in recent years. Braces, as lateral force‐resisting elements of a structure, are designed to not only react in the elastic region, but also to exhibit nonlinear response beyond the elastic limit. However, buckling in compression drastically degrades the performance of braces under earthquake loading. Buckling restrained braces (BRBs) have been evolved into very effective systems for severe seismic applications. They prevent buckling in compression through the encasing of core steel into a steel tube and confining infill concrete. The effect of infill material is investigated in this research through the use of experimental tests. Filler material may be concrete, grout or mortar, as well as granular material such as compacted aggregate. Moreover, lightweight concrete or lean concrete may be utilized as filler to reduce the overall structural weight. Furthermore, the need for unbonding material may not arise when sand and gravel mixture is used. Nevertheless, the strength of the aggregate should be such that no buckling or strength deterioration is observed. Parametric studies on BRB characteristics are carried out in this research. Results of cyclic loading tests are then provided for individual cases to characterize the effect of response parameters of BRB assemblages. Copyright © 2009 John Wiley & Sons, Ltd.     

“豹猫”多功能住宅，布拉格，捷克

豹猫是一种猫，以此命名这座钢铁房子是由于拼写的相似性（钢在捷克语中是“ocel”）。它建于捷克共和国最大的废弃钢铁厂区内．钢铁是这里最重要的特色．建筑的北、西和东立面都是钢板。所使用的特殊钢材会迅速生锈，但这一过程很快会停止并将在表面生成一层氧化铁以保护钢板。整座房子由此变成了一个坚固的钢锭。豹猫的立意渗透入钢立面和图形之中。     

Das Verhältnis von Bautechnik und Festigkeitslehre in Gerstners “Handbuch der Mechanik” – Zum 250. Geburtstag von Franz Joseph Ritter von Gerstner

On the relationship between construction engineering and strength of materials in Gerstner's “Handbook of Mechanics”. Commemorating Franz Joseph Ritter von Gerstner's 250^th birthday. Like nobody else before him Gerstner based the theory of material strength in his “Handbook of Mechanics” on experiments. To this end he discussed the classic experimental stress analyses undertaken by Musschenbroek, Rondelet, Eytelwein, Rennie, Telford, Brown, Brunel, Barlow, Tredgold, Navier and Dufour. He also carried out extensive test series himself, for which he designed his own devices for determining tensile and bending strength. Gerstner's experiments on the tensile strength of wrought iron and steel, for example, set standards in terms of precision, methodology and application. As part of the design work for a chain suspension bridge in Prague he developed a polynomial formula for the stress‐strain diagram of steel and wrought iron, the parameters for which he determined himself through experiments. Gerstner clearly differentiated between a linear region (“perfect elasticity”) and a nonlinear region (“imperfect elasticity”) and warned against exceedance of the proportionality limit, particularly for chain suspension bridges. He also dealt extensively with the bending strength of timber and iron structures. With his empirically accentuated theory of material strength Gerstner established the basic principles of a physically substantiated theory of proportions for structural and machine engineers, which formed the historical‐logical transition to structural theory and classic dimensioning theory.     

钢纤维增强高强轻骨料混凝土的力学性能

为提高高强轻骨料混凝土(HLAC)的强度和韧性,在HLAC中分别掺入体积分数为0.5％～2.0％的微细型、端钩型、波纹型钢纤维,研究了钢纤维类型及其体积分数对钢纤维增强高强轻骨料混凝土(SFHLAC)的抗压、劈裂抗拉、抗折和抗剪强度等力学性能的影响,分析了SFHLAC的韧度因子和承载力变化系数等材料韧性指标的变化特点....     

Dehnungsabhängige Berechnung vierseitig gelagerter Querschnittselemente unter Druckbeanspruchung im Brandfall

Strain‐based calculation of stiffened elements in compression subjected to fire. Local buckling, the non‐linear stress‐strain relationship of steel at elevated temperatures, non‐uniform temperature distributions as well as thermal strains and restraints have a strong influence on the compression strength of stiffened elements (internal compression parts) in fire. This paper proposes a novel model for calculating the load‐shortening behavior of stiffened elements under fire conditions. It uses strain‐based capacity curves. These curves can additionally be used to calculate the axial load‐temperature behavior of stiffened elements with both uniform and non‐uniform temperature distributions. The simplified calculation model avoids classification and considers local buckling, the non‐linear material behavior of steel at elevated temperatures, thermal strains and stresses as well as thermal restraints.