Herewith we publish intermediate results of our work on the Bullet Constraints Builder. This report is an extract of a much larger study of comparisons between the three simulation methods: DEM, FEM and AEM. This main study is for the time being restricted and it will only be published at a later stage. We are happy that we got green light to disseminate an extract with text content that was created by Laurea University of Applied Sciences.
In this report our simulation results are compared with well documented real collapse cases: The demolition of a simple beam, a mid-size column-slab assembly, and the destruction of the Pyne Gould Corporation building by an earth quake. The good agreement between simulations and reality is encouraging.
The claim that the apartment building in Chennai (see post below) collapsed because of a lighting strike sounds- at first- far fetched, since such never was reported before. However, the Polytechnic Südwestfalen, Germany, made laboratory tests that showed that an enormous explosive power is mobilized, when the charge of a lighting jumps from one reinforcement iron to another (when not properly bound together). A possible lesson for engineers and builders in the industrialized countries as well.
© Polytechnic Südwestfalen, Prof. Dr.- Ing. Jan Meppelink
The simulation of the Yu- experiment, for the first time really put our work we have done so far to the test in terms of physical accuracy. We have built the beam with increasing discretization (subdivision) levels. We approximated the weight needed to break the setup by running multiple simulations for each subdivision level. We where very happy to see that the finally established weights of 5100, 5400, 4800, 5000 kg etc where all in a very close range compared to the real loading level of 4700kg in the original real world experiment. (maximal deviation +15%)
We emphasize that at the moment we do not track permanent plastic deformation or crack propagation. What at this stage is interesting to us is to evaluate if we can predict the absolute moment of breaking of a structural assembly. This first comparison with a real world experiment seems to indicate that this is the case.
To validate structural performance of reinforced concrete structures many tests on RC assemblages have been carried out under column removal scenarios. They provide valuable information on structural dynamic performance. One such experiments was executed at the Fraunhofer Institute for High-Speed Dynamics by following the specimen design by Jun Yu and Kang Hai Tan: A ca 6 meter long concrete beam supported by a center concrete pillar was loaded with a constant 47kN in form of two huge concrete block weights . The center pillar was then suddenly removed by explosives.
The research papers by the Fraunhofer Institute can be downloaded from here.
With the support of the engineer office Schüssler-Plan we have collected a set of formulas that is now enabling us to take into account the steel reinforcement in a building element.
Steel reinforcement can improve particular strength values. For example to improve the performance under shear force steel stirrups are added, or to improve the resistance against compression and tensile forces longitudinal irons are added etc.
These Formulas can now be applied to calculate quite accurately the threshold values we need to be set for our particular constraints. We created an excel table to run the calculations on a test bases.
Next we will implement the formulas directly into the BCB- addon. The script will calculate relative strength values: 160131-formulas-calculation, tensile, shear and bend based on a sample element and then apply those relative values in N/mm2 to all the other elements within the same element group.
We are waiting with excitement to the results of the first validation cases.
The BCB has now a manual to introduce the first user interface version. The manual can be downloaded from here:
The Bullet Constraints Builder script is now posted on Github for developers to test and comment. The script needs to be downloaded as a ziped file (on the right lower corner of the site)