Structural Systems

Delia Tacheny
INT 322 - Building Systems

Weekly Summary

After discussing the site and the general building enclosure last week, this week we learned about various structural systems - both historical and modern. Given that this topic is heavily structural though, the reading first clarified the role of an Interior designer, and why this topic may pertain to them. 

Though an interior designer does NOT deal with structural, load-bearing systems, it is helpful for interior designers to understand the language of structural systems so that in working with colleagues such as architects and engineers, and because these systems impact the interior space, they may better understand the functionality of a building established by its structural basis. To define better the expertise of an Interior Designer, many organizations layout lengthy definitions. A few areas of expertise include, but are not limited to: Space planning and utilization, long-term project and lifestyle planning, awareness of relevant building codes, safety and accessibility, ergonomics, acoustics, restoration, furnishings, appliance choices, etc.

Diving into structural systems, the purpose of a structural system is to carry the loads of a building/ structure and transfer them to the foundation and therefore the ground. There are three primary types of structural systems: bearing wall, structural frame, and stud wall. 

A bearing wall relies on the entire wall to carry all loads to the foundation beneath, and is typically constructed of concrete, stone, brick, or concrete blocks. To note, when an opening must be made in a bearing wall, a lintel or arch is needed to carry the load of the wall. 

A structural frame is composed of columns and beams that transfer loads to the foundation. A structural frame is typically constructed of heavy timber, structural steel, or pre-cast concrete.

And a stud wall is a system relying on several small members to carry loads to a horizontal sole plate that in turn distributes the weight to a sill plate. Stud walls can be constructed using light gauge steel or light frame wood.

Structural basics to consider are stability, strength and stiffness, economy, and aesthetics. Stability describes the state when the forces are equal to zero. Several loads are to be considered in the structural design phase: live loads are loads that move - people, furniture, etc.; dead loads include the building material and weight of the building itself; a uniform load is distributed evenly, while a concentrated load acts on a single point. Static loads are loads that move over time and dynamic loads are sudden movements such as earthquakes and wind that may put pressure on a building. These loads can be categorized into various forms of stress/resistance: tension, compression, sheer, and bending.

There are a variety of structural techniques that have been used to resist loads and create stable structures: cables, post and beams, trusses, arches, shells, a cantenary, dome, etc. Structural techniques have changed over time; a few examples of historic systems are mortise and tenon (a pegging system) and balloon framing (rather than the modern version of platform framing). 

There are a variety of alternative systems as well that are not as popular in use and/or are used in different cultural climates: Structural insulated panels (SIPs), cob (earth, straw, water, sand), adobe (dirt, water, clay), rammed-earth, cordwood, bamboo, earth-sheltered, gabion, sandbags, etc.

And once again sustainability comes into play as we consider the use of recycled materials such as reclaimed lumber; recycled concrete, bricks, or stones; or the use of plastic bottles is incorporated into a concrete mixture. 

As last time, I enjoyed gaining a refresher on construction terminology and structural systems, and I even learned some new things such as all the alternative systems.

Alternative Building System Research: Adobe Construction

Adobe construction is not only a greatly historic and multi-cultural form of construction; it has also become a popular, modern and sustainable construction choice. It is an environmentally friendly option with extremely sustainable materials (basically dirt and sun) and it reduces the need for air conditioning and heat with its natural heating and cooling properties. 

Adobe is a sun-dried material, and so while sustainable, it is also conducive to thriving better in some climates than others. A wet climate may cause the bricks to return to mud, and a constantly changing temperature may cause crumbling. Climates of warmer and dryer temperatures tend to be better locations for this type of construction.

Adobe is an ancient material dating back to the 8th century BC. It has been used in history by both the Native Americans and Spaniards (as well as others I'm sure). "The largest adobe building in the world, and probably the most famous adobe structure standing, is the Great Mosque of Djenné in central Mali, near the edge of the Sahara Desert... built in 1907 on the ruins of earlier mosques." 

Though there are variations, the construction of adobe bricks and buildings follow these general steps (taken from page 3 of the resource cited below):

The making of adobe bricks: 

• Sand and clay are mixed with water.
• Straw or grass (and sometimes manure) is usually added, which helps the mud shrink into uniform brick shapes as it dries.
• The mud mixture is put into wooden forms and leveled and shaped.
• After they have dried for a few days, the bricks are set on their edges for at least four weeks of air-drying.

Basic method for building with adobe bricks:

• Build your foundation. Adobe houses usually don't have basements. Foundations can be made of stones or other locally available materials.
• Lay the bricks with mortar. Mud works best because it shrinks and swells with the bricks. Cement and similar mortars are too strong and rigid.
• Stack bricks together to make thick walls—10 inches or more. This mass helps cool the house summer and warm it in winter. Adobe houses are usually rectangular and rarely more than two stories high.
• Leave openings for doors and windows... but not too many; and use lintels.
• Choose a roof. The variety of options includes thatched roofs, timbers and sticks, adobe mud, terra cotta tile, wooden shingles, and metal roofing. The roof should be fairly flat but not level since water needs to run off.
• Select a coating. Builders use coatings of mud plaster, whitewash, lime plaster and cement stucco to protect adobe walls.

Even as an ancient method, adobe still seems to be a great, sustainable, low-cost option if the climate agrees!

How Adobe Construction Works | HowStuffWorks