Wood Properties

Wood Properties and Wood Structural Behavior: Principles of Wood Structural Design

Understanding structures is fundamental to the education of the professional architect. This course provides a structural analysis for entry-level architecture students. It seeks to simplify the process applied as fundamentals principles of the practical aspects of structural design.

Introduction:

Our focus in this course is on wood because it's the preferred building material for residential construction in North America and Europe. We will also provide courses about other building material such as masonry, concrete, and steel. Since most of the same principles that apply to wood apply as well to all of those other materials, this course will end up studying those other materials by default

Wood is becoming increasingly popular in all type of construction, from residential to heavy commercial and industrial construction. As with all materials, the design of wood structures is based on building code regulations. The durability of wood structures must also be considered and increasingly environmental considerations are influencing the choice of structural materials. Compared to masonry, concrete and steel, wood has environmental advantages.

This tutorial is an introductory course to the behavior of wood structures. In this tutorial, we will estimate the lateral loads on low-rise wood buildings due to wind and seismic events. The proper determination of loads is one of the most import steps in the design process. Even if the design of the structural components is correct, improperly calculated loads will cause the structure to be incorrectly designed. We will start with a very simple example using a "box" as structural model. The "box" model is used to show you how buildings are modeled and their expected response to wind and seismic induced loads.

Before we get to our example, we need to do a little bit of structural analysis, and define some terms.

1. Structural Behavior

Structural Analysis

The process used to determine the adequacy of a wood is as follows: Determine the loads and then calculate the stresses. Finally, check the allowable stresses against the actual stresses.

Determine the Loads

Determining the amount of weight the structural is going to support is the first step in the structural analysis of a structural support. There are two major categories of loads: dead and live loads. Dead and live loads are terms used in mechanical and structural engineering, especially where analysis of real world objects are required. A 'load' refers to any type of force exerted on an object, which may be in the form of a 'weight' like gravitational force, a pressure, or anything which affects the object in question.

Dead loads:

Typically, dead loads are those which do not change over the course of normal operations of the object or those which are considered to act permanently. For instance, concrete, roofing, flooring, pipes, interior partition walls and furniture are considered examples of the permanent non-structural elements. When calculating the total dead load, environmental control systems such as machinery, elevator machinery and all other construction systems within a building must also be included. The weight of the structural members themselves normally provides the largest portion of the dead load of a building.

Usually the magnitude of the dead loads of buildings can be determined with a 5% margin of error. Therefore, manufacturers arrange information regarding properties of building materials systematically in a table or in columns and rows. Because properties of construction materials often vary due to the rapidly changing marketplace, it is always very important to keep up-to-date on the changes. The load due to these materials is usually expressed as kN/m3 or lbs/ft3. However, for further consideration, they are normally converted to load/area or load/length. To be continued...