Research is getting under way to develop prescriptive code language and performance-based design guidelines for a “rocking frame” structural system that relies on vertically post-tensioned shear walls for seismic resistance. The system promises to improve seismic performance, reduce rebar congestion and enhance constructibility, says the engineer developing it. Photo: Courtesy of Tipping Mar Placing vertical post-tensioning tendons in ducts in concrete shear walls is known to reduce rebar congestion and simplify construction. Drawing: Courtesy of Tipping Mar “We believe these advantages could significantly impact seismic design and construction of mid-rise and high-rise concrete buildings,” says Steven Tipping, president of structural
Structural engineers inspecting Christchurch’s six steel structures designed with eccentric bracing to resist seismic loads found that five performed well in the shallow Canterbury earthquake that devastated the city on Feb. 22. But the engineers are curious about why two eccentric-braced bays of a three-story parking garage did not fare well—one fractured and the other deformed. The garage did not collapse, thanks to redundancy in the overall structure. “This is the first time the level of excitation of an earthquake was at least as large as or has exceeded the design basis in an area where steel, eccentrically braced frames
A week after the devastating shallow earthquake that struck Christchurch, New Zealand, on Feb. 22, structural engineers are surprised and relieved that damage to modern engineered buildings was not even more widespread. Recordings at several instrumented sites indicated that ground motion exceeded the maximum considered event. The MCE has a one in 2,500 chance of happening in any given year. Photo Courtesy Logan Mcmillan / www.gorillapictures.co.nz Low-rise devastation frames the 26-story landmark hotel, stabilized by construction crews after one corner dropped by a meter. + Image The magnitude-6.3 Canterbury quake, centered some 10 kilometers from downtown Christchurch and only 5
Engineers, working with the city, have devised a program of repairs to the 26-story Hotel Grand Chancellor, damaged but still standing in the magnitude-6.3 earthquake Feb. 22 in Christchurch, New Zealand. Landmark hotel is in precarious position following devastating earthquake. At least one engineer, visiting from the U.S., advised the city against the repair as too risky to workers. After the remediation, owner Grand Hotels International will decide whether the building can be salvaged, say city officials. The hotel, which dropped about one meter at one end, is considered stable. The repairs will take three weeks. Damage to the hotel
Four days after the magnitude-6.3 Canterbury quake that shook Christchurch, destroying significant areas of the city, rescue operations in the central business district are almost complete except for the zone around the 26-story Hotel Grand Chancellor, which is leaning and near collapse. Photo: Directrooms.com The Grand Chancellor Hotel, shown before the earthquake, is in danger of collapse. The city has cordoned off the area around the hotel, say Christchurch city officials. Built in 1986 and operated by Grand Hotels International, the concrete-framed building is 85 m tall, according to the Council on Tall Buildings and Urban Habitat. If the structure
An engineer on the ground in Christchurch says that New Zealand�s seismic retrofit code and/or construction methods should be strengthened based on the damage to recently upgraded buildings. Photo: AP Photo/Kyodo News, Shuzo Shikano Rescuers stand atop a collapsed structure in Christchurch. Related Links: Engineers Surprised By Damage to Newer Structures The New Zealand Building Code Eyewitness Account of New Zealand Earthquake Many other Christchurch buildings, damaged in many cases as a result of soil liquefaction, were rendered uninhabitable and also still pose a public threat because they might collapse, says the engineer, Amir Gilani. Several recently seismically retrofitted buildings
The New Zealand earthquake surprised engineers by triggering severe damage or collapse of some recently constructed buildings. Photo: AP Photo/Kyodo News, Shuzo Shikano Rescue workers search for victims buried under the rubble near the Canterbury Television building in Christchurch, New Zealand, Wednesday night, Feb. 23, 2011. The magnitude 6.3 earthquake that struck 10 km from Christchurch, South Island, New Zealand on Feb. 22 brought down or severely damaged some contemporary structures because the quake was extremely shallow—centered only 5 km below the surface. “New Zealand has very good loading standards and a strict regulatory environment and since the mid-70s onwards,
The Pacific Earthquake Engineering Research Center is calling on seismic engineers, government agencies and researchers to try out a “live” beta version of a web-based interactive tool that will allow them—free of charge—to search, extract and download recorded ground motions for the analysis and design of earthquake-resistant structures. Seismic engineers familiar with the tool are already lauding it, especially for use in performance-based earthquake engineering. Photo: Courtesy of Peer Web-based app lets engineers explore many seismic scenarios. The 2010 PEER Ground Motion Database allows users to select ground-motion records to match the seismic code’s response spectrum or a customized site-specific
Code crafters are lauding a significant process change in reference-standard development that provides markers for progress along the way, directional signals for reaching goals and validation of the standard’s potential impact on energy use and cost. The process, based on energy modeling and analysis, helped the developers of the 2010 edition of the commercial-building energy standard reach their goal of providing a standard that, if followed, could result in a whopping 30% reduction in both energy use and costs compared with use of the standard’s 2004 edition. Crafters of the next edition of the energy standard already are using the
Earlier-than-expected changes to ConsensusDOCS, the three-and-a-half-year-old library of model contracts for building design and construction, have been welcomed by lawyers who say the update not only enhances the original documents but demonstrates a development process responsive to industry changes. ConsensusDOCS, a coalition of 31 industry groups and a rival of the American Institute of Architects and other standard-agreement developers, says more improvements are coming soon. Photo: Russell Witherington - Fotolia.com ConsensusDOCS released the update on Jan. 19, at least 18 months ahead of the originally envisioned five-year revision cycle. One rationale is that “the economics of the construction industry today