TABLE OF CONTENTS In today's engineering lexicon, the term lateral loads usually describes the effects of wind and earthquakes, even though in the recent past it included any horizontally applied forces. This terminology seeks to differentiate lateral loads from downward-acting gravity loads, even though in reality wind and seismic forces can act in both horizontal and vertical directions. Indeed, modern building codes require that wind be applied perpendicular to the roof surfaces nearly upward for shallow roofs and that a percentage of earthquake loading be applied vertically.
The ghastly pictures of damage caused by hurricanes and earthquakes testify that the builders of yesterday did not quite know how to make their structures resistant to these natural disasters. Even today, we are still learning how to make buildings withstand these extreme and largely unpredictable forces of nature. As we shall see, the building code provisions dealing with seismic design are in a state of Sturm und Drang, with major changes occurring every few years. New codified design approaches, usually even more confusing than the ones they replaced, and quasi-official advisory documents proliferate, each aiming to explain the complex reality better. Still, these design guidelines are but a gross oversimplification of what actually happens during an earthquake or hurricane.
In this chapter, we do not attempt to undertake an in-depth study of the specific requirements of any particular building code or design document; many of them are likely to have become obsolete by the time you read this book. Instead,...
