Civil Engineering Design最新文献

Due to growing traffic volume and more restrictive design standards, structural engineers require new strengthening systems for concrete structures. Especially the level of calculated shear reinforcement has increased with the introduction of the Eurocode standards. Therefore, new methods to improve the shear strength of existing structures are needed. Concrete screws are used as a fastening system in concrete. Due to the mechanical connection, a very robust bond between the reinforcement element and the concrete is given. The new idea is to use these anchoring elements as postinstalled shear reinforcement. To show the usability and enhancements of the new method, several test series with concrete girders have been performed at the University of Innsbruck. Using concrete screws in several different configurations all test beams showed a remarkable increase in shear-load capacity. With a new design approach derived from the test results it was possible to apply the new system to several pilot-projects. One slab bridge built in the 1970s was strengthened to the load level according to Eurocode. Another pilot-project was realized at a railway bridge with a two span concrete box girder. This bridge was built with tendons vulnerable to stress corrosion cracking. To ensure a ductile failure, strengthening was necessary which was realized with concrete screws under ongoing traffic on and underneath the bridge. Currently a shear strengthening of a city tunnel in the central area of Munich is planned. In the roof slab about 7000 concrete screws are projected to be installed as shear and bending strengthening system.

The goal of the common research project autartec, funded by the German Federal Ministry of Education and Research (BMBF), is the development of a modular system for largely self-sufficient buildings. Specifically, known technologies, for example, for solar power and heat generation or decentralized storage should be developed so that they can be integrated space saving into the building envelope or the building structure of energetically and climatically functional buildings. Within the frame of Joint project I “Functionally integrated components made of textile concrete,” lightweight elements for stairs and walls were developed. For these applications, carbon reinforced concrete provides new possibilities in the design of high performance space saving construction components. The innovative wall elements will be introduced in this article.

Structural Health Monitoring with analysis of dynamic characteristics intends to detect stiffness changes caused by damage. It can be performed by vibrational tests resulting to modal parameters, that is, eigenfrequencies, damping, modeshapes, or modal masses. Those parameters are themselves informational and even allow often deducing the stiffness matrix. Based on that, it is possible to identify and to localize changes in the stiffness matrix due to damage, that is, localization and quantification of damage. However, changing test conditions, like ambient temperature or excitation force or existing nonlinearities of concrete, show important influence on damage indicators and hence need compensation prior to damage detection. Considering this background, this article focuses on comparing ambient excitation to forced excitation including appropriate exciters. Furthermore, continuous monitoring is discussed vs discrete testing in distinct time-intervals. The intention of the comparison is to give an overview, that is, helpful for choosing appropriate measurement technique for the sake of correct damage detection subsequently.