I’ve prepared an English translation of Gábor Kazinczy’s Experiments with built-in beams (Kísérletek befalazott tartókkal), published in three parts in the Hungarian journal Betonszemle in 1914. The paper starts with a practical question about beams embedded in building walls, but develops an idea that remains central to structural engineering: yielding at one location does not necessarily mean the whole structure has reached its capacity.
One of the experimental beams loaded with bricks
(Figure 3 of the article)
The tests took place in October 1913 in a Budapest villa under construction. Two steel beams were embedded in concrete ring beams at floor level, then loaded with stacks of bricks until failure. Kazinczy wanted to understand how much restraint the supports actually provided. Assuming a beam’s ends are perfectly fixed makes a substantial difference in its calculated bending moments, so this was more than an academic question.
The interesting part comes when he examines how the beams failed. One beam developed pronounced bends at both ends and near the middle. Kazinczy explained that a yielded region could continue resisting bending moment while allowing rotation. As more load was added, the bending moments could redistribute to other parts of the beam.
Today, we call these regions plastic hinges. Unlike an ordinary pin connection, a plastic hinge still resists bending moment. In the ideal plastic model of a beam fixed at both ends, hinges at the two ends and near midspan form a collapse mechanism, allowing large displacement without a further increase in load.
That distinction between local yielding and collapse of the whole structure is what makes this paper important. It is an early explanation of the behavior underlying plastic analysis and design, as discussed in this account of Kazinczy’s contribution to structural engineering.
Several familiar modern concepts connect to this work:
Plastic analysis and design of steel structures. Engineers can calculate how much load a structure carries as yielding develops and moments redistribute, including the reserve capacity beyond first yield.
Moment redistribution in reinforced concrete. With sufficient rotation capacity, continuous beams can accommodate a different distribution of bending moments from that predicted by an elastic analysis. Modern research still examines the relationship between rotation capacity and redistribution.
Ductile seismic design. Special moment frames are detailed to develop plastic hinges in selected regions and dissipate energy through repeated inelastic deformation. This is a later application of the same underlying ideas about strength and deformation, illustrated in NIST’s guide to steel special moment frames.
The paper also shows the limits of the experiments. One beam’s concrete support failed, and Kazinczy emphasized that the supports still had to resist the required moments even if they were not perfectly rigid. Some of his conclusions, particularly about reinforced concrete, have been superseded. Reading the original lets you see both the important insight and the questions that remained unresolved.
My translation includes the equations and tables, with some figures recreated for clarity and to translate their Hungarian labels. Margin notes identify the corresponding issue and page in the original journal. For anyone interested in how these ideas were first being worked out, it’s worth reading Kazinczy’s own explanation.
