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PROCEEDINGS OF THE EIGHTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY
Edited by: B.H.V. Topping, G. Montero and R. Montenegro
Structural Characterization of an Industrial Masonry Chimney
F.J. Pallarés1, S. Ivorra2 and A. Agüero1
1Department of Applied Physics, Polytechnic University of Valencia, Spain
F.J. Pallarés, S. Ivorra, A. Agüero, "Structural Characterization of an Industrial Masonry Chimney", in B.H.V. Topping, G. Montero, R. Montenegro, (Editors), "Proceedings of the Eighth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 84, 2006. doi:10.4203/ccp.83.84
Keywords: industrial chimney, masonry, modal analysis, cracking, accelerometer, earthquake.
Existing industrial chimneys made of masonry in many European areas are now considered in many places as part of the cultural heritage and often protected by laws. These chimneys were constructed during the period of the industrial revolution, towards the end of the 19th Century and the beginning of the 20th Century until the 1950s, and became obsolete when electric power substituted the production system based on steam power.
Nowadays, these chimneys have fallen into disuse but still remain in parts of the cities, not consumed by the urban development, to configure a characteristic landscape. This is the case of many chimneys that can be found in the city of Valencia. The present work studies one of these chimneys and presents results from an experimental point of view where accelerations have been recorded and vibrations frequencies obtained in a modal analysis. These frequencies are compared with results obtained from a numerical model in order to calibrate it. This fact allows the use of the numerical model to test the chimney under the action of several loads and to know the response of this particular type of structure when different loads are acting.
Four seismic accelerometers have been placed at different height levels and orientations to properly collect the response of the structure when external loads are acting. The loads used to collect the measurements have been ambient forces and impulse forces with the help of a calibrated hammer. The use of this impulse force has been exploited to calculate damping factors.
All the previous data have been used to validate a numerical model adjusting the elastic modulus as the main parameter.
Slight geometric simplifications led to establishment of the numerical model and discretization using the finite element method. A finite element with cracking and crushing capabilities has been used in a three-dimensional model . The element is defined by eight nodes having three degrees of freedom per node. The initial behaviour of this element has been assumed isotropic but with cracking and crushing capabilities. Once the element has cracked, the shear transfer can be reduced through the use of some coefficients depending on the cases "smooth crack" or "rough crack".
The use of this element allows cracking to be considered and crushing features such as the loading from strong winds or earthquakes can be input in order to study failure in the masonry material.
Boundary conditions are introduced in the nodes at the basement level of the chimney, restraining displacements. It has been assumed that the chimney is clamped at ground level. No soil-structure interaction or possible base rotations have been taken into account.
By changing the elastic modulus in the numerical model to fit the natural frequencies obtained in the numerical model with the frequencies from the experimental results, the model has been used to determine the structural response when a seismic load is acting.
As time goes by, crack pattern and cracks distribution along the shaft of the chimney can be known performing a transient analysis. Furthermore, failure modes and ultimate states can be assessed in this way.
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