The Vierendeel is a frame with rigid joints patented in 1896 by Belgian engineer Arthur Vierendeel (1852-1940). His invention came about after he noticed that experiments and calculation methods on iron and steel frameworks didn't agree, making his invention a response in the then discussion on secondary stresses. After designing a church tower and testing a full-scale bridge model during the 1897 Brussels World Fair, many bridges 'système Vierendeel' were erected the following decades in his homeland, as well as a few dozens around the globe. At times the discussion on the Vierendeel got heated in trade journals and amongst people, mainly due to a lack of 'visual' safety and theoretical uncertainties concerning calculation, safety factors and welding techniques. Nowadays the Vierendeel principle is still topical and many (structural) designers apply his formal ideas. This led to a broader meaning of the word Vierendeel varying from aesthetic to strictly structural.