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Fatigue of prestressed tendons

预应力筋的疲劳

基本信息

批准号：
351987113
负责人：
Professor Dr.-Ing. Martin Empelmann
金额：
--
依托单位：
Fachgebiet Massivbau
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2017
资助国家：
德国
起止时间：
2016-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/351987113?language=en
关键词：
Fatigue prestressed tendons

项目摘要

Prestressed concrete members with pre-tensioned tendons under predominantly non-static loads need to be designed against fatigue failure. In practice, such members are used e. g. in crane runway beams, slabs in industrial constructions, towers of wind turbines, poles or bridges. The fatigue failure of these members can basically occur within the concrete, within the bond between concrete and prestressing steel as well as within the prestressing steel itself. Here, the fatigue of the prestressing steel is often the decisive failure mode. Furthermore, a significant difference between fatigue tests with singular prestressing steel and tests with embedded pre-tensioned tendons in prestressed concrete members can be noticed.In research projects and further preliminary work, carried out by the applicant, a database of prestressed concrete beams under fatigue loading was established and various investigations on prestressing steel samples were analyzed. A large part of the test results of prestressed concrete beams - especially with small stress ranges in the prestressing steel and high numbers of load cycles - indicate a lower fatigue strength compared to the SN curves according to EC2+NA and MC10. This was confirmed by a test of a prestressed concrete beam conducted by the applicant at the iBMB, TU Braunschweig.It can be concluded that the fatigue behavior of embedded pre-tensioned tendons is influenced by structural and systematical parameters and damage mechanisms, leading to a reduction in the fatigue strength compared to fatigue tests on prestressing steel samples. This deviation is not sufficiently recognized in common models. Due to the lack of basic understanding regarding the identification, the definition and the modelling of these parameters and damage mechanisms, systematic investigations are required to close existing gaps in knowledge. Therefore, the fundamentals of the fatigue strength of pre-tensioned tendons will be investigated in this research project experimentally, theoretically and numerically. Based on fatigue tests on singular prestressing steel samples and prestressed concrete beams the different parameters and damage mechanisms which are caused by the complex fatigue processes and stresses due to built-in conditions of pre-tensioned tendons are to be examined. In combination with theoretical models as well as numerical investigations the individual parameters and mechanisms will be identified, quantified, modeled and described.The aim of this project is to develop a model - based on these investigations - which describes the fatigue behavior of prestressing steel including the effects of the various relevant parameters and damage mechanisms.

在非静态荷载作用下，预应力混凝土构件的预应力筋需要进行抗疲劳设计。在实践中，这样的构件被使用e。G.用于起重机跑道梁、工业建筑中的板、风力涡轮机的塔、杆或桥梁。这些构件的疲劳破坏基本上可以发生在混凝土内部、混凝土和预应力钢筋之间的粘结部内以及预应力钢筋本身内。在这里，预应力钢筋的疲劳通常是决定性的失效模式。此外，可以注意到，预应力混凝土构件中使用奇异预应力钢的疲劳试验与使用预埋预张拉筋的疲劳试验存在显着差异。在申请人开展的研究项目和进一步的前期工作中，建立了疲劳荷载下的预应力混凝土梁数据库，并对各种研究进行了分析预应力钢样本。大部分预应力混凝土梁的试验结果--尤其是预应力钢筋应力范围小且荷载循环次数多的梁--表明疲劳强度低于根据EC 2 +NA和MC 10的SN曲线。申请人在布伦瑞克的iBMB进行的预应力混凝土梁试验证实了这一点。可以得出结论，预埋预张拉钢筋束的疲劳性能受结构和系统参数以及损伤机制的影响，导致疲劳强度与预应力钢样本的疲劳试验相比有所降低。这种偏离在普通模型中没有得到充分认识。由于对这些参数和损害机制的识别、定义和建模缺乏基本了解，需要进行系统的调查，以填补现有的知识空白。因此，本研究计画将以实验、理论及数值分析探讨先张法预应力筋疲劳强度之基本原理。通过对预应力钢试件和预应力混凝土梁的疲劳试验，研究了预应力钢束在不同预张条件下的复杂疲劳过程和应力引起的不同参数和损伤机理。结合理论模型和数值研究，将对各个参数和机制进行识别、量化、建模和描述。本项目的目的是在这些研究的基础上开发一个模型，该模型描述预应力钢筋的疲劳行为，包括各种相关参数和损伤机制的影响。