Reinforced concrete is a construction method that relies on widely understood and historically validated concepts. Traditionally, reinforcing bars are placed in formwork prior to concrete placement. However, many applications require reinforcement to be added to existing structures by means of reinforcing bars grouted into drilled holes, usually with injectable adhesives. …
Under the National Earthquake Hazards Reduction Program (NEHRP) and the stewardship of the National Institute of Standards and Technology (NIST), the Applied Technology Council (ATC) and the Consortium of Universities for Research in Earthquake Engineering (CUREE) have jointly prepared an excellent series of ten succinct and practical seismic design guides for practicing engineers, available for free online. …
It is generally perceived that vibration is not an issue for reinforced concrete floor systems. Because of the inherent mass and stiffness of such systems, this perception is generally true. However, there can be situations where the effects of vibration are one of the main design issues that need to be addressed. In this general overview, simplified methods are provided that can be used in a preliminary analysis to determine approximate fundamental vibration characteristics, which can help in choosing a suitable floor system for a given set of conditions. …
Seismologists, earthquake engineers and seismic code experts understand the science of earth that moves and the structures built on it, but many of the concepts involved may be too abstract for architects, builders and the public. This article offers an analogy to help explain seismic design and presents three different construction techniques used in Chile, Japan and the United States that counter an earthquake’s effects. …
Traditional structures are linear, stiff, restricted, heavy, and inefficient; lightweight structures, on the other hand – whether in fabric, cable, timber, concrete or stone – are nonlinear, long-spanning, flexible, highly efficient, and environmentally friendly. This series shows how, when form follows force as well as function, the result is a structure that soars. …
The Subgrade Modulus, also known as the Modulus of Subgrade Reaction, is a stiffness parameter typically used in defining the support conditions of footings and mat foundations, such as that shown on Figure 1. The parameter is expressed in units of [Force]/[Length]3. Physically however, it is defined as the (contact) bearing pressure of the foundation against the soil that will produce a unit deflection of the foundation. …
Apart from the weight, there is nothing lightweight about lightweight structures. With traditional structures, the loads are resisted by the stiffness in the beams, columns, and walls; with tension-only and compression-only structures, the overall form of the structure becomes critical. Get the form right and the structure can span huge distances with minimal material; get the form wrong and you are in trouble.
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For context and introduction, the author’s education is in solid mechanics followed by an early career in aerospace designing airplanes. Leaving the aerospace industry to design buildings wasn’t easy. …