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1.
R. Braun Dr. 《Materialwissenschaft und Werkstofftechnik》2007,38(9):674-689
A short review of the stress corrosion cracking (SCC) behaviour of aluminium alloys is given. Mechanisms of environmentally assisted cracking are outlined. For aluminium alloys, in which stress corrosion cracks propagate predominantly along grain boundaries, anodic dissolution and hydrogen embrittlement have been proposed. Transgranular stress corrosion cracking occurring at severe loading conditions has found particular interest concerning localised corrosion‐deformation interactions. Accelerated test methods for assessing the SCC behaviour are described, including the slow strain rate testing technique and the breaking load method. Results of recent studies on environmentally assisted cracking of aluminium alloys are summarised. Most of the work published in the last two decades has been on aluminium‐lithium based alloys and improved high strength Al‐Zn‐Mg‐Cu alloys in corrosion resistant retrogressed and re‐aged tempers. 相似文献
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Prof. Dr.-Ing. Gero Marzahn Hon.-Prof. Dr.-Ing. habil. Olaf Mertzsch Lisa Kramer 《Bautechnik》2020,97(7):508-516
Load-bearing index to grade structural capacities of road bridges For decades, bridge structural conditions have been evaluated on the basis of structural health grades determined during a bridge examination. However, recalculations conducted for bridge structures show that structural deficiencies, such as low or insufficient load-bearing capacities, are not or not sufficiently reflected by these conditions if no corresponding damage or unusual behavior can be detected. There are known cases of deficient bridges that had to be replaced even though the structural health grade suggested a good condition or vice versa. To better measure and assess the structural conditions of a bridge, i.e., the criteria of the superstructure that are relevant for the load-bearing capacity, a new parameter was developed. The load-bearing index allows for a different perspective as it identifies presumed deficiencies on the basis of various criteria that are independent of the physical condition. In a next step, these deficiencies have to be further examined. Both parameters – the structural health grade and the load-bearing index – describe the condition and the usability of a structure. But they do so from a different point of view, and, therefore, complete the overall picture of the structure. 相似文献
3.
Temporary corrosion protection of prestressing steels in non‐injected ducts Prestressing steels may be subjected to corrosive conditions during the manufacturing process at building sites. Due to this a risk of hydrogen induced stress corrosion cracking of the steels may arise. Tests under practical conditions in a prestressed concrete beam were carried out where non‐injected ducts were treated with preheated scavenging air to prove this method being able to protect the prestressing steels against corrosion. The results yielded sufficient corrosion protection by this measure and therefore it may be an interesting alternative in comparison to corrosion protection by film forming agents which contain inhibitors. 相似文献
4.
《Beton- und Stahlbetonbau》2017,112(2):75-84
Structural monitoring for safeguarding the remaining life time of a bridge building endangered by stress corrosion cracking Initial point of the structural monitoring of the bridge over the railway in Waren (Müritz) were the results of recalculation and the investigations of the prestressed wires. In this regard it was documented, that the bridge is in fact endangered by stress corrosion cracking, but ductility provides a sufficient prior notice of failure. Thus the further use of the bridge is possible, provided of a shortened inspection interval. Due to ongoing use the inspection of the building is possible to a limited extend only, the necessary frequent visual assessment was replaced by a structural monitoring. So the focus was not on the complete measurement based observation of the building. The main aim of the structural monitoring rather was the purposeful and economical registration of possibly developing bending cracks. During the monitoring period of two years the development of a bending crack under service load was detected and thereby the real arise of the crack‐before‐failure‐criterion was confirmed. The paper shows the principle procedure of collecting information as basis for a safe decision making as well as on planning, execution and evaluation of structural measurements and their integration into the assessment process of the structure. 相似文献
5.
Suspended ceilings in indoor swimming pools are safety‐relevant components. As was demonstrated by the collapses of the ceiling of the Uster (CH) indoor swimming pool (1985) and again at Steenwijk (NL, 2001) greater attention has to be paid to selecting suitable materials and inspecting the state of such components. Our findings according to corrosion of metal fastening components of more than 150 indoor swimming pools in Switzerland are reported. The corrosion behaviour of stainless steels and galvanized steels are compared and discussed including newer results from the literature. 相似文献
6.
Dr.-Ing. Thorsten Stengel Philipp Obermeier Dipl.-Ing. Johannes Zellner 《Beton- und Stahlbetonbau》2019,114(10):724-736
Nitrate induced stress crack corrosion within the cupola of the elephant's house Hellabrunn – Demolition of the historic cupola after 100 years That was not an usual hundredth birthday party: The historic and protected elephant's house at the zoo Hellabrunn was demolished by a blast in September 2014. During the preceding months an intensive inspection of the whole structure was conducted. Results showed that a considerable part of the reinforcement was irreparably affected by nitrate induced stress crack corrosion. Therefore, the elephant's house had to be closed and a temporary support was installed. The present paper illustrates the outstanding achievements during design and erection of the elephant's house and explains the mechanisms and consequences of nitrate induced stress crack corrosion of the reinforcement. 相似文献
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8.
Oliver Steinbock Dipl.-Ing. Eberhard Pelke Dipl.-Ing. Oliver Ost Dipl.-Ing. 《Beton- und Stahlbetonbau》2021,116(2):101-108
Carbon reinforced concrete – An alternative method for strengthening Concrete Bridges; Part 1: Basics and background information to the pilot project “federal highway bridges (A 648) across the river Nidda” In 2020 two of three bridges, which are part of the german highway road A 648, were strengthened with carbon reinforced concrete for the first time in Germany. The two superstructures were erected in the 1970s as a pre-stressed beam. As tendons a so called -sigma-oval-steel was used, which is sensitive for stress corrosion cracking. According to German guidelines and to exclude a sudden failure, it has to be verified if a damage of the tendons can be seen at the surface of the cross section via cracks along the superstructure. This -crack before failure- criteria was not fulfil for the described superstructures. With reference to the relevance of the bridges in the local infrastructure around Frankfurt a. M., a strengthening concept was necessary. Due to that fact, a strengthening with carbon reinforced concrete was identified as an economic and minimal invasive method. The report on that forerunner project is spread into three parts. The following first part gives an overview about the bridges and the background on stress corrosion cracking, added with explanations about the planning steps. The second part describes the strengthening with carbon reinforced concrete with a focus on bridges. The third part goes further into detail, regarding the construction and the design of a carbon reinforced strengthening for the superstructure. 相似文献
9.
The stress corrosion cracking behaviour of plate material of the aluminium alloys 2024‐T351, 8090‐T8171, 7475‐T651, and 7075‐T7351 was investigated performing constant load tests. Short transverse tensile specimens were permanently immersed in aerated aqueous 0.6 M Na2Cl solutions with additions of Na2SO4, NaNO3, NaHCO3, NH4HCO3, Na2HPO4, Na2SO3 or Na2CO3. The concentration of the added salts was 0.06 M. The applied stress was 100 MPa, except with 7075‐T7351 specimens, which were loaded at 300 MPa. Environment induced failure was not observed in neutral 0.6 M NaCl solution. The various salts added promoted intergranular stress corrosion cracking with the alloys 2024‐T351, 8090‐T8171, and 7475‐T651. Threshold stresses were generally below 100 MPa. For 8090‐T8171 exposed to chloride containing electrolytes with additions of sulfate, hydrogen phosphate, or sulfite, threshold stresses were approximately 100 MPa or higher. Similar results were obtained for 7475‐T651 plate when immersed in chloride‐hydrogen phosphate and chloride‐carbonate solutions. Alloy 7075‐T7351 was resistant against intergranular stress corrosion cracking. Specimens suffered pitting corrosion during immersion in the corrosive environments. Failure observed with 7075‐T7351, in particular when exposed to the chloride‐nitrate solution, was associated with reduction of cross‐sectional area due to pitting and transgranular stress corrosion cracking. 相似文献
10.
Dr.-Ing. Gregor Schacht Max Käding Dipl.-Ing. Prof. Dr.-Ing. Guido Bolle Prof. Dr.-Ing. Steffen Marx 《Beton- und Stahlbetonbau》2019,114(2):85-94
Concepts for the assessment of bridges with the risk of stress corrosion cracking The networks of the road construction authorities and DB AG still contain a significant number of bridges manufactured with steel endangered by stress corrosion cracking. Although there are guidelines that provide computational and material assessment, they do not always lead to a (desired) result and the final definition of appropriate measures. In this context permanent monitoring has played a subordinate role, even though the degradation processes and their consequences occurring in the structure can be excellently resolved and the continuous information gives the possibility to state the condition of the structure at any time. The present article composes the existing rules and shows the possibilities and limitations of the recommended methods. Subsequently, examples for the implementation of monitoring systems are presented each for a building with and without computational announcement before collapse. 相似文献