Every country has hundreds of rules and regulations surrounding the construction of buildings. In countries such as Chile and Japan, which face regular earthquakes, many extra rules have been put in place to ensure buildings can withstand these disasters as well as possible.
Designers can remedy this by adding a flexible steel skeleton made of something called rebar, which is also known as reinforcement steel. Casting rebar inside concrete boosts the overall strength of the concrete and enhances its ability to withstand force.
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After the Kobe earthquake in 1995, which killed more than 6,000 people, Japan carried out extensive research into making buildings earthquake-resistant, including retrofitting older structures, the New York Times reported. Like Chile, it put in place strict rules around making sure buildings are able to withstand earthquakes.
It says making sure buildings can withstand earthquakes not only saves lives and prevents injuries, but reduces the economic consequences of these disasters. There are also environmental benefits, as there is less need for debris to go to landfill, and no consumption and emissions spent on reconstruction efforts.
Earthquake-resistant or aseismic structures are designed to protect buildings to some or greater extent from earthquakes. While no structure can be entirely impervious to earthquake damage, the goal of earthquake engineering is to erect structures that fare better during seismic activity than their conventional counterparts. According to building codes, earthquake-resistant structures are intended to withstand the largest earthquake of a certain probability that is likely to occur at their location. This means the loss of life should be minimized by preventing collapse of the buildings for rare earthquakes while the loss of the functionality should be limited for more frequent ones.[1]
Currently, there are several design philosophies in earthquake engineering, making use of experimental results, computer simulations and observations from past earthquakes to offer the required performance for the seismic threat at the site of interest. These range from appropriately sizing the structure to be strong and ductile enough to survive the shaking with an acceptable damage, to equipping it with base isolation or using structural vibration control technologies to minimize any forces and deformations. While the former is the method typically applied in most earthquake-resistant structures, important facilities, landmarks and cultural heritage buildings use the more advanced (and expensive) techniques of isolation or control to survive strong shaking with minimal damage. Examples of such applications are the Cathedral of Our Lady of the Angels and the Acropolis Museum.[citation needed]
Based on studies in New Zealand, relating to 2011 Christchurch earthquakes, precast concrete designed and installed in accordance with modern codes performed well.[2] According to the Earthquake Engineering Research Institute, precast panel buildings had good durability during the earthquake in Armenia, compared to precast frame-panels.[3]
Thus, two wooden houses built before adoption of the 1981 Japanese Building Code were moved to E-Defense[5] for testing. One house was reinforced to enhance its seismic resistance, while the other one was not. These two models were set on E-Defense platform and tested simultaneously.[6]
Designed by architect Merrill W. Baird of Glendale, working in collaboration with A. C. Martin Architects of Los Angeles, the Municipal Services Building at 633 East Broadway, Glendale was completed in 1966.[7] Prominently sited at the corner of East Broadway and Glendale Avenue, this civic building serves as a heraldic element of Glendale's civic center.
In October 2004 Architectural Resources Group (ARG) was contracted by Nabih Youssef & Associates, Structural Engineers, to provide services regarding a historic resource assessment of the building due to a proposed seismic retrofit.
In 2008, the Municipal Services Building of the City of Glendale, California was seismically retrofitted using an innovative combined vibration control solution: the existing elevated building foundation of the building was put on high damping rubber bearings.
A steel plate shear wall (SPSW) consists of steel infill plates bounded by a column-beam system. When such infill plates occupy each level within a framed bay of a structure, they constitute a SPSW system.[8] Whereas most earthquake resistant construction methods are adapted from older systems, SPSW was invented entirely to withstand seismic activity.[9]
SPSW behavior is analogous to a vertical plate girder cantilevered from its base. Similar to plate girders, the SPSW system optimizes component performance by taking advantage of the post-buckling behavior of the steel infill panels.
The Ritz-Carlton/JW Marriott hotel building, a part of the LA Live development in Los Angeles, California, is the first building in Los Angeles that uses an advanced steel plate shear wall system to resist the lateral loads of strong earthquakes and winds.
On May 9, 2009, one unit (Unit 7) was restarted, after the seismic upgrades. The test run had to continue for 50 days. The plant had been completely shut down for almost 22 months following the earthquake.
A destructive earthquake struck a lone, wooden condominium in Japan.[12] The experiment was webcast live on July 14, 2009, to yield insight on how to make wooden structures stronger and better able to withstand major earthquakes.[13]
The Miki shake at the Hyogo Earthquake Engineering Research Center is the capstone experiment of the four-year NEESWood project, which receives its primary support from the U.S. National Science Foundation Network for Earthquake Engineering Simulation (NEES) Program.
"NEESWood aims to develop a new seismic design philosophy that will provide the necessary mechanisms to safely increase the height of wood-frame structures in active seismic zones of the United States, as well as mitigate earthquake damage to low-rise wood-frame structures," said Rosowsky, Department of Civil Engineering at Texas A&M University. This philosophy is based on the application of seismic damping systems for wooden buildings. The systems, which can be installed inside the walls of most wooden buildings, include strong metal frame, bracing and dampers filled with viscous fluid.
The proposed system is composed of core walls, hat beams incorporated into the top-level, outer columns, and viscous dampers vertically installed between the tips of the hat beams and the outer columns. During an earthquake, the hat beams and outer columns act as outriggers and reduce the overturning moment in the core, and the installed dampers also reduce the moment and the lateral deflection of the structure. This innovative system can eliminate inner beams and inner columns on each floor, and thereby provide buildings with column-free floor space even in highly seismic regions.[14][15]
After a large earthquake, the news inundates us with images of crumbled concrete, twisted steel, and disaster recovery teams searching through rubble for survivors. According to the California Department of Conservation, the 1989 Loma Prieta earthquake caused 63 deaths, and 3,757 people reported injuries from the disaster. The World Health Organization says that earthquakes caused nearly 750,000 deaths worldwide between 1998 and 2017. And more than 125 million people were affected, either through injuries or displacement.
Though earthquakes are uncontrollable, earthquake damage to people and property is predictable and preventable with earthquake engineering and earthquake-resistant building technology. While an earthquake-proof building is impossible, at least for the foreseeable future, earthquake resistance is possible with a holistic, cohesive approach.
In earthquakes, some of the damage is immediate, catastrophic, and obvious. Other damage can be more insidious. For example, seismic vibration could separate roof flashing, the material that directs water away from vulnerable connection points in the roof. Then water can enter the structure (sometimes unnoticed) and cause damage later.
Methods for making a structure earthquake-resistant involve either deflecting, absorbing, transferring, or distributing vibrations from seismic activity. Those methods come into play with building design. A more holistic, proactive approach is seismic design. This process analyzes both the site and the surrounding area before building design begins.
All these considerations help establish priorities and inform which seismic resistance techniques to use. This holistic approach has the added benefit of hardening buildings against other threats, from terrorism to high-speed winds.
Making buildings resistant to earthquakes begins with the soil beneath it. Soft, silty soils are prone to liquefaction during earthquakes. Liquefaction is when soil temporarily behaves like a liquid. Soft soils can also amplify vibrations. Any structure on such soil is at risk. An earthquake-resistant building is best located on solid ground.
Earthquake-resistance techniques can be used throughout a building, from foundation to roof and exterior to interior. The specific technique depends on the type of vibration control ideal for that location.
Seismic dampers can be used throughout the foundation and structure to absorb vibrations from earthquake forces. Dampers come in a variety of forms. For example, viscous dampers use hydraulics to dissipate energy. A tuned mass damper uses weight at the top of or at critical points throughout a structure to counteract ground motion. Friction dampers are like the brakes in most cars, converting movement to heat.
Structural reinforcements transfer or distribute vibrations to decrease their impact. For example, shear walls transfer vibrations to the foundation. Floors and roofs built as diaphragms distribute vibrations across the horizontal structure and into stronger vertical structures. Moment-resistant frames help connection points remain secure while allowing columns and beams to move without damage. 152ee80cbc