CHAPTER 1 WHAT IS STRUCTURAL ENGINEERING Have you ever traveled in a tunnel through a mountain or under city streets Have you ever gazed at a skyscraper swaying in the wind Have you peered over the edge of a bridge Then you've taken a look at structural engineering A structure is anything designed to resist or support a force or load Structural engineers usually design buildings and bridges They also work on projects such as airplane bodies and equipment supports Structural engineering is an ancient science Age old builders may not have had today's methods to calculate forces and test materials But they understood the concepts The results of their understanding are seen in ancient pyramids and arched bridges Many are still standing after thousands of years
Often parts of a structure are easy to see In a bridge each steel beam or concrete slab is part of the structure The structure of a building is often harder to see The beams columns and braces that support it can be hidden under flooring or behind walls But each piece has a purpose FACT All structures use the same structural engineering principles The Guggenheim Museum in Spain looks like a complex structure But its design principles are the same as those used in a simple cottage The Pont du Gard in France is 2 000 years old The Romans built the structure to deliver water Today it is used as a bridge resist a force that opposes or slows the motion of another force or object
PROJECT 1 EXPERIMENT WITH STRUCTURAL SHAPES Did you know that the shapes of structures and their parts affect their strength Test out some shapes to see for yourself MATERIALS CAKE PAN SMALL BUCKET OF SAND CLEAR TAPE 6 SHEETS OF POSTER BOARD MEASURING 8 5 BY INCHES 22 BY 28 CENTIMETERS SEVERAL MID SIZED BOOKS STEPS Fold a piece of poster board into thirds along the longer side Unfold to make a triangular tube Tape the edges together Make a fold 1 5 inches 4 centimeters from each edge of the longer side of another piece of poster board Unfold and carefully bend and tape the edges together to form a dome shaped tube Fold another piece into a square shaped tube Tape the edges together Repeat Steps 1 through 3 to make two of each shape
Lay the square tubes on their sides next to each other One at a time stack books on top until the tubes flatten Repeat the experiment with the other tubes Which of the shapes can hold the most books Now place one of the square tubes on its side in a cake pan Slowly and evenly pour sand around the tube until it is nearly covered Repeat step 7 with the other tubes Which tube keeps its shape best What if you stack the books on top too WHAT HAPPENED In the first experiment it's likely the triangle held the most weight A triangle is one of the strongest structural shapes Its stable angles help it evenly distribute loads to all sides You'll often see the triangle shape in buildings and bridges The Burj Khalifa tower in Dubai and the Louvre art museum in Paris are two famous examples So why does the dome shape hold up better when buried A triangle is strong when loaded at its points But pushing on its sides weakens it Domes and arches are strong when loads are placed all around them This is why the arch shape is used for most tunnels Challenge Experiment with the sizes of the structural shapes Do bigger triangles or domes support more weight What about smaller ones
