Why triangular beams are not used in building?

Triangular beams are not commonly used in building construction primarily due to their inefficiency in distributing loads and their inability to effectively resist bending and shear forces compared to rectangular or I-beams. The shape of triangular beams can create stress concentrations at the points where the sides meet, leading to potential failure. Additionally, standard construction practices and design codes favor more conventional beam shapes that provide greater strength and stability. Lastly, the complexity of connecting triangular beams to other structural elements can complicate construction and increase costs.