Reference Objects

The investigations and results of partial models and model couplings on different fields of research are brought together and verified on synthetic reference objects. Three reference objects are implemented, which in the course of development are processed from simple partial models to complex global models, tested and perfected in the informational value on different levels.

I - Tower Structures

Responsible: Institute for Constructive Civil Engineering

A tower structure is suitable in an excellent way to demonstrate partial models, their influences, foundation etc. and their couplings around different modelling or their abstraction levels. Furthermore, it succeeds to define in-situ issues, like in-situ buckles of the tower encasing, whether it is reinforced concrete or steel, like the design of connecting elements between individual tower sections, like the mounting of observation decks, antennas or other similar additional load bearing structure systems, like issues of prestressing and so on.
Therewith, the development of the used partial models can be tested and represented according to the given problem characteristics in a well arranged manner. The partial models pass through all stages of development from modest spatial frame models up to complex numerical models. The coupling of the different partial models (influences, floor, construction made of steel/concrete etc.) is analysed within and between the different levels.

II - Bridge Constructions

Responsible: Prof. U. Freundt

Bridge constructions exist in the most different postmodern manifestations, from the simple girder bridge to wide span cable structure. Therewith, this construction form enables a conditioning of different partial model levels and the interactions connected with that of partial models, such as foundation, influences, material etc.. Moreover, the usual bridge systems nowadays are interesting, as often they are a combination of steel and reinforced concrete. The stress processes represent both deterministic defined loads as well as load processes.
The connection of these load bearing systems with vertical elements, i.e. e.g. slim pillars are interesting, where an interaction between horizontal and vertical bearing effects must be considered and the influence of geometric nonlinearity plays an essential role. The problems of the nonlinearity are amplified by the effect of bedding elements.

III - One or Multi-storeyed Skeleton Constructions

Responsible: Dr. J. Schwarz

This construction type represents an important application field of civil engineering. The essential problems of interaction between structure and foundation, influences, bracing system etc. can be exemplarily examined. Here, the effects from spatially distributed influences are also interesting as these structures possess large external surfaces and the stochastic character, e.g. of wind impact have an essential influence on the construction of the load bearing system. The practically applied norm based influences are not realistic for these load bearing structures in many places.
Significant evidence regarding the bearing effect and load-capacity are obtained during investigation of earthquake influences. Analysis and synthesis methods exist on different standards, which lead to subtly differentiated results and require a specific coupling of partial models.

Reference object: Tower

Anemometer at the top of the tower
First five mode shapes of numerical tower model
Measurement box of the monitoring system

Civil engineers are dealing with structures mostly made of concrete, reinforced concrete and steel. But it in most cases structures are composite, i.e. comprising more than one material, and researchers cannot investigate the material behavior separately. To this end, a broadcasting tower has been selected as a suitable reference object in the framework of GRK, which is made of reinforced concrete, steel and fiber glass.

Before starting any experimental investigation it is advised to carefully create the design of experiments (DoE). The aim is an optimal design of measurement setups based on the application of mathematical or engineering methods [1]. The calculated optimal designs will be verified by tests on a numerical model and validated by means of monitoring an existing structure.

One of the most important load cases on tower structures is wind. In many cases slender structures need to be analyzed in a way that allows for the description of their dynamic structural behavior. Therefore the investigations of the research group focused on the tower is mainly concentrated at the dynamic response of the structure to different loading scenarios taking changing environmental conditions into account.

Starting point of the investigations were numerical simulations of the response to dynamic wind loads assuming different severity of damage [2]. Within these simulations which included the development and combination of several partial models for the description of the structure (the wind load and an assumed damage scenario), a damage detection concept based on vibration measurements was applied. The improvement of the used methodologies is subject of ongoing research.

To validate the theoretical concepts that were implemented numerically, experimental studies are required. In 2014 short term measurements were conducted in order to get a first impression about the modal parameters of the tower. This helped to develop the setup for the long term monitoring which has been installed in 2015.

Researchers involved in tower group are: Tajammal Abbas, Sharmistha Chowdhury, Kosmas Dragos, Shahram Ghorashi, Ina Reichert, Maria Steiner

Responsible supervisor: Dr.-Ing. Volkmar Zabel

References

 

[1] Lahmer, T.: Konzepte der optimalen Versuchsplanung für das Monitoring von Bauwerken, Allgemeine Vermessungs-Nachrichten, 3/2011, Wichmann-Verlag

[2] Deeb, M., Abbas, T., Ghorashi, S., Stade, I., Wudtke, I. and Zabel, V.: Modellbasierte Schadensidentifikation an Turmbauwerken, Bautechnik Sonderdruck “Modellqualitäten”, pp. 82-89, 2013