A new method has been developed for measuring the force of ground shaking during earthquakes at particular locations. The proposed Earthquake Shaking Force (EqSF) rating is based on the maximum vector sum of the recorded ground accelerations in the three main directions scaled with the strong ground motion duration. …
The 2015 Edition of Special Design Provisions for Wind and Seismic (SDPWS) was approved as an American National Standard on September 8, 2014, with the designation ANSI/AWC SDPWS-2015 (Figure 1). The 2015 SDPWS was developed by AWC’s Wood Design Standards Committee (WDSC) and contains provisions for design of wood members, fasteners, and assemblies to resist wind and seismic forces. …
Concentrically braced frames (CBFs) resist large lateral forces due to wind and earthquake loading, and their ductility is largely derived from tension yielding and compressive buckling of the braces. Since 1990, AISC has focused on improving seismic resistance of CBFs by introducing detailing requirements for the connection, geometric limits of the brace, and capacity-design-type strength requirements for the gusset plate and the framing members. …
It is a well-understood concept and an inevitable law of statics that loads must be transferred between beams and columns. This is an idea that is not foreign to engineers. Since our first classes in structural analysis, we have been developing our expertise at analyzing and designing beam-column intersections. The idea of balancing the sum of forces at such locations is one that cannot be disputed. However, there are some vagaries with this concept when considering flat plate and flat slab systems, which by definition have no beam-column joints. Hence, moment transfer becomes a more complex issue. …
Bridge historians and early textbooks generally call a truss with alternating compression and tension diagonals a Warren; however, sometimes it is called an equilateral truss since all panel lengths and diagonals are of equal length creating a series of equilateral triangles. When the panel lengths are shorter than the equal length diagonals, it was sometimes called an isosceles or isometric truss. …
The purpose of science is to explain and predict. Uncertainty in scientific predictions degrades their value. Uncertainty should not be hidden, but it should be reduced over time to show progress in science.
Predictions of future ground motions are needed for mitigation and insurance of seismic risk. The United States Geological Survey (USGS) is responsible for predicting future ground motions throughout the U.S. and territories. …
Many types of ground improvement (GI) are used in modern geotechnical construction. For the purpose of this article, GI refers to a rigid or semi-rigid cylindrical inclusion (GI element) installed through otherwise unsuitable bearing soils into underlying suitable strata to enable the use of spread footing foundations for building support. Due to favorable economics compared to viable foundation alternatives, use of GI is accelerating in the United States. …
This is the second of a two part series that draws attention to Young Member Groups. The first article “Rainbows Only Come After Rain” by Ellen (Chuan-Hua) Kuo PE, LEED AP.BD+C was published in the February, 2015 issue of STRUCTURE.
The extent to which industries train market entrants and have established recruiting procedures varies from industry to industry. …
The Pacific Rim, or The Ring of Fire, is commonly known as the area bordering the Pacific Ocean that attracts a high volume of seismic and volcanic activity from shifting plate tectonics. Over the past 100 years, 90 percent of earthquakes and 75 percent of volcanic eruptions have occurred in the Pac Rim, making it one of the most active and destructive areas in the world. With the recent influx of high-magnitude earthquakes over the past few years, we are reminded of the importance of seismic protection and its value in safeguarding some of our world’s most precious structural assets. …
Skidmore, Owings & Merrill LLP was an Outstanding Award Winner for the Chhatrapati Shivaji International Airport – Terminal 2 project in the 2014 NCSEA Annual Excellence in Structural Engineering awards program (Category – International Structures over $100M).
As recently as 15 years ago, only 6 million travelers used Chhatrapati Shivaji International Airport each year. …