11 TYPES OF TRUSSES ACCORDING TO BALANCE, CONFORMATION AND ORIGIN - TECHNOLOGY - 2025

The types of trusses may vary depending on the balance, and forming source or designer. Known as flat or spatial lattices or as lattices and reinforcements, in engineering terms they are rigid structures reinforced by straight rods at their ends that have a triangular shape.

This type of configuration has the property of supporting loads in its plane, especially those that act on the joints or nodes. Consequently, its application in construction is of great importance, because it is an articulated and non-deformable system that does not cut or flex. This implies that its elements participate actively in terms of compression and traction.

Unlike the square, this triangular formation is not unstable, so it can be applied in small or large works. The trusses can be composed of various materials, the most commonly used being wooden, metallic and reinforced concrete.

Depending on the use that you want to give to this kind of framework, they are generally applied in the construction of warehouse ceilings, industrial warehouses, aircraft hangars, churches, stadiums, bridges or beam systems.

Classifications of truss types

-According to its balance function

A truss can be totally isostatic or statically determined in relation to the mechanical balance applied to the external shape of the structure. The same happens with the internal elements, which are evaluated in their reactions and efforts to know their stability. The categories resulting from this evaluation have been established as follows:

a) Isostatic

This concept refers to a kind of structure that can be analyzed using the principles and formulas that reveal static values. As mentioned, its nature is statically determined, so the removal of some of the components that bind the frame as such would cause a catastrophic failure of the entire system.

b) Hyperstatic

The essence of this type of configuration is its equilibrium state, which means that the bending moment has a value equal to 0 in each of the bars that make up the system.

Despite this condition, the truss may present conditions of instability due to the type of design with fixed nodes that can resemble an isostatic structure.

-According to its conformation

This type of trusses has a flat structure that is composed of articulated knots and that have various shapes:

a) Simple

This truss is a statically defined conformation, so the number of rods and the number of hinged joints must meet the appropriate formula. It presents the known shape of a triangle and its calculation is based on graphical statics and the balance of the nodes.

b) Composite

Like the previous one, they present a structure with static determination that can be designed from 1 or 2 simple trusses. In this case, both structures are joined by an additional bar at a common point so that they remain fixed. They can also include 3 additional poles or an internal frame that meets the balance criteria.

c) Complex

Since they belong to the category of hyperstatic, their difference is that it does not exclude the previous models and includes the rest of the geometries. Although it is composed of fixed joints, its calculation can be done using the Heneberg method or the matrix method of stiffness. The first is more approximate, while the second is much more precise.

-According to their origin or who designed them

On the other hand, some commonly used trusses are named after their creators, who studied them, or the city where they were first applied. Among them, the following stand out:

a) Long truss

This variant appeared in 1835 and is related to Stephen H. Long. It is a design in which the top and bottom horizontal chords are joined by vertical studs. The whole set is braced by double diagonals and resembles X's enclosed by squares.

b) Howe truss

Although it had been used before, this structure was patented in 1840 by William Howe. Also known as Belgian, it uses vertical studs between the top and bottom chord and is widely applied to wood. In this design, it consists of diagonal bars that receive compression and other vertical ones that support traction.

c) Pratt's truss

Created by Caleb and Thomas Pratt in 1844, it is a variation of the previous model but with a more resistant material: steel. It differs from Howe's truss in the sense of the bars, which form V. In this case, the vertical bars are compressed and the diagonals are pulled.

d) Warren truss

Patented in 1848 by the English Willboughy Monzoni and James Warren, this structure is characterized by forming isosceles or equilateral triangles, giving the same length to the diagonals. Compression and traction forces are present in these crossed elements due to the application of vertical loads in the upper nodes.

e) Truss K

It is generally applied to bridge design and gets its name from the orientation of a vertical element in combination with the oblique parts. It is presented as triangles that start from the center and its design allows to improve the performance of the compressed diagonals.

f) Baltimore truss

Another characteristic model of the bridges of this city. It incorporates greater support in the lower part of the structure. This prevents compression collapse and controls strain. Its sections look like 3 triangles in 1 linked by a horizontal bar.

It is important to note that although these structures can be both triangular and rectangular. This is clearly exemplified in gabled, scissor-type and cantilever roofs.

When using studs, incorporating these vertical elements into bridges, ceilings, and vaults gives it a slightly more boxy look.

References

1. Muzammar, Chemma (2016). Types of Trusses. Recovered from es.slideshare.net.
2. Mariana (2013). Hypostatic, isostatic and hyperstatic structures. Recovered from prezi.com.
3. Open Course Ware (2006). Typical structures: function, general forms, elements… University of Seville. Recovered from ocwus.us.es.
4. Tecun (no date). Flat lattices. University of Navarra, School of Engineers. Recovered from dadun.unav.edu.
5. Construmática (no date). Integral parts of a truss. Recovered from construmatica.com.