nmoscovitch - ultimate guide to structural engineering

STRUCTURALENGINEERINGBASICS

ULTIMATE GUIDE TO

ULTIMATE GUIDE TO STRUCTURAL ENGINEERING BASICS

Structural Engineers use a variety of tools, skills and resources in order to perform their jobs professionally, responsibly and safely. Although these are all important and critical to what they do, they are not all necessary for the average person to understand in order to have a good grasp on what is involved in a structure and how it is designed. This guide will provide you with the MUST KNOW information with regards to Structural Engineering if you have time or money invested in a building or structure.


Structures are designed to resist loads. These loads are forces applied to the structure that are either vertical or horizontal that ultimately cause stresses on the load bearing elements. Vertical loads can include the weight of the structural materials and finishes, the weight of furniture, the weight of people, and the weight of snow/rain. Horizontal loads can include pressure on a building due to wind, the weight of soil pushing against a wall, and seismic loads from earthquakes.

LOADS

Structures can be built out of many di�erent types of building materials. The most common types of materials are wood, reinforced concrete, steel and masonry. Each of these materials have di�erent properties, characteristics and costs associated with them that make some more suitable than others depending on the type of structure, look of the structure and budget.

Here is a breakdown of each of these common building materials:

BUILDING MATERIALS


WOOD is readily available and an economically feasible natural resource that is lightweight and easy to use for construction. It also provides good insulation from the cold which makes it an excellent building material for homes and residential buildings. There are many di�erent species of wood used in construction that have varying strengths and properties that make some more suitable than others depending on the application. Wood is very flammable which requires additional costs for fire rating if required by code. It is a great construction material to use when the loads on the structure are not too large and the span between load bearing walls and beams are not too long.



REINFORCED CONCRETE is a composite material made up of steel reinforcing and concrete. Concrete is very strong when placed in compression however, it’s brittle and weak when it is placed in tension. Steel reinforcing, or rebar, is used to resist tension loads in a concrete element. Combined with steel rebar, reinforced concrete is stronger and more suitable for a wide range of structures such as tall multi-story buildings, bridges, roads, tunnels and so many other applications. Reinforced concrete can be cast in place directly at a job site, or it can be casted in a controlled environment prior to installation. Building with concrete is fairly labour intensive as it requires form works to be installed and rebar to be in place prior to pouring/installing the concrete. Overall, reinforced concrete is a very desirable building material as it has excellent fire resistance ratings, durability and strength.


STEEL is one of the strongest building materials available with excellent strength capacity in both tension and compression. It has a high strength-to-weight ratio which makes it ideal for structural framework of tall buildings and large industrial facilities. Structural steel is available in standard shapes such as angles, I shaped beams and C-channels. These shapes can be welded together or connected using high-strength bolts to build structures capable of resisting large forces and deformations. Steel is a relatively expensive building material but it is quick to install, and can support large loads without taking up much space which is desirable for owners and architects as they often want to maximize the space in a building.

MASONRY construction uses individual units to build structural elements along with mortar to bound the units together. The most common material used in design of masonry structures is concrete block with vertical steel reinforcing if necessary. Because masonry is strong in resisting compression stresses it is ideal for it to be used in the construction of load bearing walls where the load is applied vertically on the masonry units. Similar to reinforced concrete, steel reinforcing is used in concrete block walls to resist tension loads or bending in the wall if lateral loads are applied. Grout can be installed in the hollow cores of concrete block structures to increase its strength and to hold the reinforcing in place to make the materials act compositely. Other masonry materials include brick, stone and glass block. Masonry is highly durable and easy to construct, however, it’s properties and strength limit how it is used as a building material.


Structural engineers design structures bases on the stresses imposed on the load bearing elements that make up the structure. The amount of stress depends on the magnitude of load and the geometry of these elements. Each type of material has di�erent stress limits. A very large load in an element does not necessarily mean that the stress in that element will be large as well. Stress is defined as load over an area, therefore a load spread over a smaller area will have a higher stress than a load spread over a larger area. The types of stresses depend on the direction of the load being applied to the structural element. The stresses structural engineers design for include the following:

� Bending� Compression� Tension� Torsion� Shear� Bearing

STRESSES



These are the horizontal members that resist vertical loads on a floor or roof structure. Beams, joists and trusses transfer load to the vertical members of the structure. Joists are often smaller and lighter than beams. Joists transfer load to larger beams that take load to vertical columns. Usually, the deeper the beam, joist, or truss, the longer it can span without it deflecting too much or becoming overstressed.

Trusses are an economical option for long spans and are built up of multiple horizontal, vertical and diagonal elements that are placed in either compression or tension. Trusses are often used in the construction of roofs in homes and in bridges.

BEAMS, JOISTS AND TRUSSES


These are the vertical, often slender, members that resist axial loads from a floor or roof structure. A beam transfers its load into columns which take the load down to the foundation. Columns are most often loaded in compression, unless there is uplift on a structure then it is loaded in tension.

COLUMNS


This is a wall in a structure that transfers vertical load from a floor or roof structure down to the foundation or structure below.

LOAD BEARING WALLS

This is what stabilizes a building and provides bracing for in order to prevent the structure from collapsing under earthquake or wind loading. These could be in the form of steel bracing, solid walls, stair or elevator shafts, rigid connections and floor/roof structures.

LATERAL LOAD RESISTING SYSTEM


This is a critical part of any structure where load is transferred from one structural element to the other. It could be between two structural elements with the same material or two di�erent materials. Examples of connections include bolts and welds for steel, nails and screws for wood, anchors and studs for concrete and masonry.

CONNECTIONS


The loads that a structure is designed to resist need to be transferred into the ground below the earths surface. Foundations are the element of the structure that transfers the building loads to the soil below, either near the earths surface or deep into the ground. Footings are an example of a shallow foundation and are the foundation of choice for lightly loaded structures such as a house. Piles are examples of deep foundations and are often the foundation of choice for heavily loaded structures such as high rise buildings.

FOUNDATIONS


Building codes are rules and requirements that must be followed when designing a structure. They will tell you the loads the building should be designed to resist based on occupancy and geographical location. The codes are based on testing and experience and are ultimately there to protect the public and ensure a building is safe for people to occupy.

BUILDING CODES


Structural drawings are the blueprints that contractors use to build a structure. These drawings have information as to what materials are used, and how they come together to form the structure. Structural drawings often include plans, details, sections and general notes/specifications.

STRUCTURAL DRAWINGS


Structural engineers need to make sure they design a load path that can safely transfer the load from its point of application through the structure all the way to the foundation where the structure meets the earth’s surface. An example of a load path when designing a house could be if snow is applied to a roof, the load will enter the roof joists/trusses and will be transferred to beams, which will transfer loads to vertical columns or walls that will bear on a foundation that takes the load into the ground below. Another example would be a gymnast on a balancing beam. The weight of the gymnast gets transferred into the balancing beam and then into the supports on each end and down into the floor structure. The closer the gymnast is to a support, the higher the load the support will attract.

LOAD TRANSFER AND LOAD PATH

A structural design that is based on human comfort for vibration under walking excitation, rhythmic activities and vibrations due to wind

PERFORMANCE BASED DESIGN


These are used in the design of structures to account for uncertainty in the load, strength and quality of material, and workmanship.

FACTOR OF SAFETY

A structural design that is based on the strength of a material and its ultimate capacity

FORCE BASED DESIGN

A structural design that is based on the sti�ness of the material to control it’s deflection

DEFORMATION BASED DESIGN

Copyright © 2019 by Structural Engineering Basics

Now that you have read this Ultimate Guide to Structural Engineering Basics, hopefully you have a good understanding as to what is involved in the design of structures and how structures work. If you have any questions with regards to the content of this guide, or if there is anything you would like to learn about structural engineering, feel free to contact us at [email protected] and we would be happy to help. Good luck in all of your structural engineering endeavors!

Best Wishes

Noah Moscovitch,P. Eng.

Dr. Mostafa El-Mogy, P. Eng.

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nmoscovitch - ultimate guide to structural engineering

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