Earthquake Engineering is a branch of interdisciplinary engineering that designs and analyzes structures, such as buildings and bridges, taking into account earthquakes. The main purpose is to make such structures more resistant to earthquakes. An earthquake (or seismic) engineer aims to build structures that will not be damaged in small shocks and will avoid serious damage or collapse in major earthquakes. Earthquake engineering is a scientific field that deals with the protection of society, the natural environment, and the man-made environment of earthquakes by limiting seismic risk to socially-economically acceptable levels. Traditionally, it has been defined narrowly as the study of the behavior of structures and geo-structures is subject to seismic loads; it is considered as part of structural engineering, geotechnical engineering, mechanical engineering, chemical engineering, applied physics, etc. However, the tremendous costs experienced in the recent earthquake have led to an expansion of its scope to cover the discipline of a wider civilian field. engineering, mechanical engineering and from social sciences, especially sociology, political science, economics and finance.
The main objectives of earthquake engineering are:
- Predict the potential consequences of strong earthquakes in urban areas and civil infrastructure.
- Design, build, and maintain structures for exposure to earthquakes up to expectations and in accordance with building codes.
Well designed structures do not have to be very powerful or expensive. It should be well designed to withstand seismic effects while maintaining an acceptable level of damage.
Video Earthquake engineering
Seismic load
Seismic load means an excitation application generated by earthquakes on a structure (or geo-structure). It occurs on the contact surface of the structure either with soil, with adjacent structures, or with gravitational waves from the tsunami. The expected loading in certain locations on the Earth's surface is estimated by seismological engineering. This is related to the seismic danger of the site.
Maps Earthquake engineering
Seismic performance
Earthquake or seismic performance determines the ability of the structure to maintain its main functions, such as security and serviceability, on and after exposure a particular earthquake. A structure is usually considered safe if it does not endanger the lives and welfare of the people in or surrounding it by partially or completely collapsing. A structure can be considered usable if it is able to fulfill its designed operational function.
The basic concept of earthquake engineering, which is implemented in the main building code, assumes that a building must survive a very rare earthquake, which is very severe by sustaining significant damage but without collapsing globally. On the other hand, it should remain operational for more frequent, but less severe seismic events.
Seismic performance assessment
Engineers need to know the measured levels of actual or anticipated seismic performance associated with direct damage to individual buildings subject to certain ground shocks. Such an assessment can be done either experimentally or analytically.
Experimental ratings
Experimental evaluation is an expensive test that is usually done by placing the model (scale) of the structure on a wobble table that simulates the vibrations of the earth and observes its behavior. Such experiments were first performed over a century ago. It has only recently become possible to perform a 1: 1 scale test on the full structure.
Because of the expensive nature of the tests, they tend to be used primarily to understand the seismic behavior of structures, validate models and verify analytical methods. Thus, once validated correctly, computational models and numerical procedures tend to carry large loads for the assessment of seismic performance of structures.
Analytical/Numerical Assessment
Seismic performance assessment or seismic structural analysis is a powerful tool for earthquake engineering that utilizes detailed structural modeling along with structural analysis methods to gain a better understanding of the seismic performance of buildings and non-building structures. The technique as a formal concept is a relatively new development.
In general, structural seismic analysis is based on structural dynamic methods. For decades, the most prominent seismic analysis instrument was the earthquake response spectrum method that also contributed to the proposed concept of building codes.
However, the method is only good for linear elastic systems, since most can not model the structural behavior when damage (ie, non-linearity) arises. The step-by-step numerical integration proves to be a more effective method of analysis for multi-degrees-freedom structural systems with significant non-linearity under the motion excitation transient process.
Basically, numerical analysis is performed to evaluate the seismic performance of buildings. Performance evaluation is generally done by using nonlinear static pushover analysis or nonlinear time history analysis. In the analysis, it is important to achieve accurate non-linear component modeling such as beams, columns, beam-column connections, shear walls, etc. Thus, experimental results play an important role in determining the modeling parameters of individual components, especially those subject to significant non-linear deformation. The individual components are then assembled to create a fully non-linear structure model. Thus the model made is analyzed to evaluate the performance of the building.
The capability of structural analysis software is a major consideration in the above process as it limits the possibility of component models, available analytical methods and, most importantly, numerical resistance. The latter is a major consideration for structures that roam into non-linear range and near global or local collapse as numerical solutions become increasingly unstable and thus difficult to reach. There are commercially available Finite Element Analysis software such as CSI-SAP2000 and CSI-PERFORM-3D and Scia Engineer-ECtools that can be used for seismic performance evaluation of buildings. In addition, there are up to research-based finite element analysis platforms like OpenSees, RUAUMOKO and older DRAIN-2D/3D, some of which are now open source.
Research for earthquake techniques
Research for earthquake engineering means field investigation and analysis or experiments intended for scientific discovery and explanation of facts related to earthquake engineering, revision of conventional concepts in light of new findings, and the practical application of developed theories.
The National Science Foundation (NSF) is the principal United States government agency that supports fundamental research and education in all areas of earthquake engineering. In particular, it focuses on experimental, analytical and computational research on the design and improvement of structural system performance.
The Earthquake Engineering Research Institute (EERI) is a leader in information dissemination related to earthquake engineering research both in the US and in the world.
The definitive list of earthquake engineering studies related to worldwide shock tables can be found at the Experimental Facility for Earthquake Engineering Simulations around the World. The most prominent of these are the E-Defense Shake Table in Japan.
U.S. main research program
The NSF also supports George E. Brown, Jr Network for Earthquake Engineering Simulations
The Disaster Mitigation and Structural Engineering Program of the NSF (HMSE) supports research on new technologies to improve the behavior and responses of structural systems that pose a threat to the earthquake; fundamental research on the security and reliability of built systems; innovative developments in the analysis and simulation of behavior-based models and structural responses including soil-structure interactions; design concepts that improve the performance and flexibility of the structure; and application of new control techniques to structural systems.
(NEES) that advances the discovery of knowledge and innovation for earthquakes and tsunami loss reduction of the nation's civil infrastructure and new experimental simulation techniques and instrumentation.
The NEES network has 14 geographically distributed shared laboratories supporting multiple types of experimental work: geotechnical centrifuge research, shake-table testing, large-scale structural testing, tsunami wave experiments, and field research. Participating universities include: Cornell University; Lehigh University; Oregon State University; Rensselaer Polytechnic Institute; University at Buffalo, State University of New York; University of California, Berkeley; University of California, Davis; University of California, Los Angeles; University of California, San Diego; University of California, Santa Barbara; University of Illinois, Urbana-Champaign; University of Minnesota; University of Nevada, Reno; and University of Texas, Austin.
The central (laboratory) equipment and data repository sites are connected to the global earthquake engineering community via the NEEShub website. The NEES website is supported by HUBzero software developed at Purdue University for special nanoHUB to help the scientific community share resources and collaborate. The cyberinfrastructure, connected via Internet2, provides interactive simulation tools, simulation tool development areas, curated central data storage, animated presentations, user support, telepresence, mechanisms for uploading and sharing of resources, and statistics about users and usage patterns.
This Cyberinfrastructure allows researchers to: safely store, organize and share data within a standard framework at a central location; observe remotely and participate in experiments through the use of synchronized data and real-time video; collaborate with colleagues to facilitate the planning, performance, analysis, and publication of research trials; and perform computational and hybrid simulations that can combine the results of multiple distributed experiments and connect physical experiments with computer simulations to enable an overall system performance investigation.
These resources together provide a means for collaboration and discovery to improve the seismic design and performance of civil and mechanical infrastructure systems.
Earthquake simulation
The first earthquake simulation is done by statically applying some horizontal inertial forces based on scale scale peak acceleration to the building's mathematical model. With the development of further computing technology, the static approach begins to give way to the dynamic.
Dynamic experiments on buildings and non-building structures can be physical, such as shake-table testing, or virtual ones. In both cases, to verify the expected seismic performance of the structure, some researchers prefer to deal with so-called "real time histories" although the latter can not be "real" for hypothetical quakes specified by building codes or by some specific research requirements.. Therefore, there is a strong impetus to engage in an earthquake simulation which is a seismic input that only has important features of real events.
Sometimes the simulation of earthquakes is understood as the re-creation of local effects of strong earth vibrations.
Structure simulation
Most anticipated theoretical or experimental evaluations of seismic performance require a simulation structure based on the concept of structural similarity or similarity. The similarity is some degree of analogy or similarity between two or more objects. The idea of ​​similarity lies in the exact repetition or approximation of patterns in the items compared.
In general, the building model is said to have something in common with the real object if both share geometric similarities, kinematic similarities and dynamic equality. The most obvious and effective type of resemblance is kinematic .
The highest level of kinematic similarity is kinematic equilibrium when, in the case of earthquake engineering, the time history of each lateral displacement of the story of the model and prototype will be the same.
Seismic vibration control
Seismic vibration control is a set of technical tools aimed at reducing seismic impacts in building and non-building structures. All seismic vibration control devices can be classified as passive , active or hybrids where:
- passive control devices have no feedback capability between them, structural elements and ground;
- active control devices combine real-time recording instrumentation on the ground integrated with processing equipment and earthquake input actuators in the structure;
- hybrid control devices feature a combination of active and passive control systems.
When ground seismic waves reach and begin to penetrate the base of a building, its energy density, due to its reflections, decreases dramatically: typically, up to 90%. However, the remaining part of the incident wave during a major earthquake still has a very destructive potential.
Once the seismic wave enters the superstructure, there are a number of ways to control it to calm its destructive effects and improve the seismic performance of the building, for example:
- to remove wave energy in the superstructure with properly designed dampers;
- to dissolve wave energy between the broader frequency range;
- to absorb the resonance part of all bandwave frequencies with the help of so-called mass damper .
The last type device, abbreviated simultaneously as a TMD for tuned ( passive ), such as AMD for active , and as HMD for hybrid mass dampers
However, there is another approach: partial suppression of the seismic energy flow to a superstructure known as seismic or base insulation.
For this, some bearings are inserted into or under all the main load carrying elements at the base of the building which substantially must separate the superstructure of its substructure resting on the vibrating ground.
The first evidence of earthquake protection using the basic isolation principle is found in Pasargadae, a city in ancient Persia, now Iran, and dating from the 6th century BC. Below, there are some examples of seismic vibration control technology today.
Control of dry stone walls
The people of the Inca civilization are the experts of polished dried rocks, called ashangs, in which stone blocks are cut to fit together tightly without mortar. The Incas were one of the finest stone masons ever in the world and many of the intersections in their bricks were so perfect that even the blades of grass could not enter between the stones.
Peru is a very seismic land and for centuries mortar construction has proven to be more earthquake resistant than using mortar. The rocks from the dry stone walls built by the Incas can move slightly and resettle without collapsing walls, passive structural control techniques using both the energy cipral (coulomb damping) principle and suppressing the resonance amplitude.
Mixed mass dampers
Typically, the adjusted mass silencer is a large concrete block installed in a skyscraper or other structure and moves in opposition to the resonance frequency oscillation of the structure by a spring-like mechanism.
The Taipei 101 skyscraper needs to withstand hurricanes and general tremor earthquakes in this Asia/Pacific region. For this purpose, a 660 metric ton steel pendulum serving as a tuned mass silencer is designed and mounted on the structure. Suspended from 92 to 88th floor, the pendulum rocked to reduce the amplification of lateral displacement resonance in buildings caused by earthquakes and strong gusts.
Hysterical dampers
A hysteretic damper is intended to provide better and more reliable seismic performance than conventional structures by increasing the dissipation of seismic input energy. There are five main groups of hysteretic dampers used for the purpose, namely:
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- Lumpy liquid dampers (FVD)
Viscous Damper has benefits as an additional damping system. They have an oval hysteresis loop and attenuation depending on the speed. While some light treatments are potentially necessary, thickened absorbers generally do not need to be replaced after an earthquake. While more expensive than other damping technologies, they can be used for seismic and wind loads and are the most commonly used hysteretic dampers.
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- Friction reducer (FD)
Friction reducers tend to be available in two main types, linear and take turns and dispose of energy with heat. Silencers operate on the principle of coulomb absorbers. Depending on the design, the friction reducer can experience stick-slip phenomena and cold welding. The main disadvantage is that friction surfaces can be worn from time to time and for this reason they are not recommended to remove wind loads. When used in seismic applications it does not matter and no maintenance is required. They have a rectangular hysteresis loop and as long as the building is sufficiently elastic they tend to return to their original position after an earthquake.
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- Silencer that produces metal (MYD)
The metal that produces silencers, as the name implies, produces to absorb earthquake energy. This type of damper absorbs large amounts of energy, but they must be replaced after an earthquake and can prevent the building from settling back into its original position.
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- Viscoelastic Dampers (VED)
Viscoelastic dampers are useful because they can be used for wind and seismic applications, they are usually limited to small displacements. There are some concerns about technological reliability because some brands have been banned from use in buildings in the United States.
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- Straddling pendulum damper (swing)
Isolation base
The basic isolation seeks to prevent the kinetic energy of the earthquake being transferred to the elastic energy within the building. This technology does so by isolating the structure of the soil, allowing them to move independently. The extent to which energy is transferred into the structure and how energy is dissipated will vary depending on the technology used.
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- Lead rubber bearings
Lead rubber pads or LRB is a basic type of insulation using heavy damping. It was discovered by Bill Robinson, a New Zealander.
The heavy dampening mechanism incorporated in vibration control technology and, in particular, in basic isolation devices, is often considered a valuable source for suppressing vibrations thereby enhancing the seismic performance of buildings. However, for somewhat flexible systems such as isolated base structures, with relatively low but highly attenuated bearing stools, the so-called "damping force" can be transformed into the main thrust force in strong earthquakes. The video shows the Lead Rubber Bearing being tested at the Caltrans-SRMD UCSD facility. The bearings are made of rubber with a tin core. It is a uniaxial test in which the bearing is also under a full structure load. Many buildings and bridges, both in New Zealand and elsewhere, are protected by lead silencers and lead and rubber pads. Te Papa Tongarewa, New Zealand national museum, and New Zealand Parliament House have been equipped with bearings. Both are in Wellington who sit on top of active errors.
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- Bottom basin isolator with damper
The spring-to-damper isolator mounted beneath a three-story town house, Santa Monica, California, is shown in a photo taken before the 1994 Northridge earthquake. It is a basic insulating device conceptually similar to the Lead Rubber Bearing >.
One of these two three-story city houses, well-documented to record vertical and horizontal accelerations on the floor and ground, has survived a severe earthquake during the Northridge earthquake and left valuable information recorded for further study.
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- Simple roller bearings
Simple roller bearings are basic isolation devices intended for the protection of various building and non-building structures against the potentially damaging lateral impact of strong earthquakes.
Support of this metal bearing can be adjusted, with certain precautions, as seismic insulators to skyscrapers and buildings in soft soil. Recently, it has been used under the name metal roller bearings for a residential complex (17 floors) in Tokyo, Japan.
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- Friction of pendulum bearing
The friction of the pendulum pads (FPB) is another name of the friction pendulum system (FPS). It is based on three pillars:
- articulation friction slider;
- sliding concave ball surface;
- attach a cylinder to withstand lateral displacement.
Snapshots with links to video clips from shake-table testing of FPB systems that support rigid building models are presented on the right.
Seismic design
Seismic design is based on official engineering procedures, principles and criteria intended to design or retrofit structures exposed to earthquakes. These criteria are only consistent with contemporary knowledge of earthquake engineering structures. Therefore, proper building designs following seismic code regulations do not guarantee safety against collapse or serious damage.
The price of a bad seismic design may be enormous. Nevertheless, seismic design is always a process of trial and error whether it is based on physical law or on the empirical knowledge of structural performance of different shapes and materials.
To practice seismic design, seismic analysis or seismic evaluation of new and existing civil engineering projects, an engineer must, typically, pass the examination on the Seismic Principles that, in the State of California, include:
- Seismic Data and Seismic Design Criteria
- Seismic Characteristics of Engineered Systems
- Seismic Forces
- Seismic Analysis Procedures
- Seismic Details and Construction Quality Control
To build complex structural systems, most seismic designs use relatively small number of basic structural elements (not to say vibration control devices) as non-seismic design projects.
Typically, according to building codes, structures are designed to "withstand" the largest earthquakes with certain probabilities that may occur in their location. This means the loss of life must be minimized by preventing the collapse of the building.
Seismic design is done by understanding the possible modes of structural failure and providing structures with the right strength, stiffness, ductility, and configuration to ensure that the mode can not occur.
Seismic design requirements
Seismic design requirements depend on the type of structure, location of the project and its authority setting the applicable seismic design codes and criteria. For example, the requirements of the California Department of Transportation called Seismic Design Criteria (SDC) and aimed at new bridge designs in California incorporate innovative seismic performance-based approaches.
The most significant feature in the design philosophy of SDC is the change from the power-based assessment of seismic demand to value-based assessment of demand and capacity. Thus, the newly adopted displacement approach is based on the ratio of elastic displacement to the inelastic displacement capacity of the major structural components while ensuring a minimum level of inelastic capacity at all potential locations of the plastic hinges.
In addition to the designed structure itself, the seismic design requirements may include soil stabilization under the structure: sometimes, highly shaken ground that leads to collapse of existing structures above it. The following topics should be the main concern: liquefaction; dynamic lateral earth pressure on retaining wall; seismic slope stability; earthquake-driven settlements.
Nuclear facilities should not jeopardize their safety in case of earthquakes or other hostile external events. Therefore, their seismic design based on criteria is much more stringent than those applicable to non-nuclear facilities. However, the Fukushima I nuclear accident and the destruction of other nuclear facilities following the 2011 T-hsu earthquake and tsunami have drawn the ongoing attention to Japan's nuclear seismic design standards and caused many other governments to reevaluate their nuclear programs. Doubts have also been disclosed during seismic evaluation and design of certain other plants, including the Fessenheim Nuclear Power Plant in France.
Failure mode
Failure mode is the way how earthquake induced failure is observed. In general, this illustrates how failure occurs. Although expensive and time consuming, learning from any real earthquake failures remains a routine recipe for advancement in seismic design. Below, some typical modes of failure generated by the earthquake are presented.
Lack of reinforcement coupled with poor mortars and inadequate roof-to-wall connections can cause major damage to an opaque brick building . Cracked or tilted walls are some of the most common earthquake damage. Also harmful is the damage that may occur between the walls and the roof or floor of the diaphragm. Separation between framing and walls can compromise the vertical support of roof and floor systems.
Light stories effect . The absence of adequate stiffness in the soil surface causes damage to this structure. A careful examination of the image reveals that a rough board enclosed, once covered by a brick veneer, has been completely dismantled from studwall. Only the rigidity of the above floors combined with support on two sides are hidden with a continuous wall, not pierced with large doors like on the side of the road, preventing the collapse of the full structure.
Liquid disbursement . In cases where the soil consists of loose granular sediment material with a tendency to develop excessive hydrostatic pore water pressures with sufficient and compact magnitude, loose saturated liquefaction of sludge can result in non-uniform settlements and slope structures. This caused massive damage to thousands of buildings in Niigata, Japan during the 1964 earthquake.
The avalanche falls . Landslide is a geological phenomenon that includes various ground motions, including falling stone . Normally, the action of gravity is the main driving force for landslides occurring although in this case there are other factors that affect the stability of the original slope: landslides require earthquake triggers before being released.
Spread in adjacent building . This is a photo of a collapsed five-story tower, St. Seminary. Joseph, Los Altos, California which resulted in one death. During the Loma Prieta earthquake, the tower pounded adjacent vibrating buildings independently behind it. The possibility of pounding depends on the lateral displacement of the two buildings' which should be accurately estimated and taken into account.
In the Northridge earthquake, the Kaiser Permanente concrete office building had a completely destroyed connection, revealing an inadequate confinement steel , resulting in the collapse of the second story. In the transverse direction, the composite end shear wall, which consists of two bricks and a shotcrete layer carrying lateral loads, is pared separately due to inadequate tissue and fails.
- An improper construction site at the foot of the mountain.
- Bad reinforcement details (lack of concrete confinement in columns and on beam-column connections, inadequate splice length).
- A soft seismic soft story on the first floor.
- Long Cantilevers with heavy dead loads.
Glide from the foundation of the effect the relatively rigid housing structure of buildings during the 1987 Whittier Narrows earthquake. A magnitude 5.9 earthquake hit West Garvey Apartment building in Monterey Park, California and shifted its superstructure about 10 inches to the east on its foundation.
If the superstructure is not installed on a basic insulation system, its changes to the dungeon must be prevented.
Reinforced concrete columns explode in Northridge earthquake due to insufficient shift strengthening which allows main reinforcement to buckle outwards. The deck sags on the hinges and fails in sliding. As a result, the La Cienega-Venice underpass of 10 Freeway collapsed.
Loma Prieta earthquake: side view of reinforced concrete failure of supporting columns triggering the collapse of the upper deck into the lower deck of a two-tier cross-country bridge from Interstate Highway 880, Oakland, CA.
Retaining wall failure at the Loma Prieta earthquake in the Santa Cruz Mountains area: northwest-trending extensional trending to a depth of 12 cm (4.7 inches) in spillway concrete to the Dam of Austria, north abutment.
The soil shakes the liquefaction of the ground that is triggered in the sand layer beneath the surface, resulting in differential lateral and vertical motions in the carapace that rests on the sand and irregular sludge. This ground failure mode , called lateral spread , is the main cause of damage caused by earthquake melt.
China Agricultural Development Bank Building that was badly damaged after the 2008 Sichuan earthquake: most of the poles and pillar docks were shaved . Large diagonal cracks in brick and veneer pairs are caused by the load inside the aircraft while a sudden settlement at the right end of the building should be linked to a potentially dangerous landfill even without an earthquake.
Tsunami impacts multiply : ocean wave pressure and hydraulic pools. Thus, the Indian Ocean earthquake of 26 December 2004, with an epicenter off the west coast of Sumatra, Indonesia, triggered a series of devastating tsunamis, killing more than 230,000 people in eleven countries by flooding the surrounding coastal community with huge waves. up to 30 meters (100 feet) high.
Earthquake resistant construction
Construction of earthquakes means the application of seismic design to allow building and non-building structures to live through anticipated seismic exposures to expectations and in accordance with applicable building codes.
Design and construction are closely related. To achieve good workmanship, detailing the members and connections should be as simple as possible. Because of any construction in general, earthquake construction is a process consisting of building, retrofit or assembly of infrastructure provided available construction materials.
The earthquake destabilization action in construction may be either directly (ground seismic movement) or indirectly (landslides caused by earthquakes, liquefaction and tsunami waves).
A structure may have all the look of stability, but it does not offer anything but a hazard when an earthquake occurs. The crucial fact is that, for safety, earthquake resistant construction techniques are as important as quality control and using the right materials. earthquake contractor must be registered in the state/province/country of the project location (subject to local regulations), bound and insured.
To minimize the possibility of losses, the construction process should be set up keeping in mind that earthquakes can strike anytime before the end of construction.
Each construction project requires a team of qualified professionals who understand the basic features of seismic performance of different structures as well as construction management.
Adobe Structure
About thirty percent of the world's population live or work in earth-made construction. Adobe Adobe bricks are one of the oldest and most used building materials. The use of adobe is very common in some of the most hazardous areas of the world, traditionally in Latin America, Africa, the Indian subcontinent and other parts of Asia, the Middle East and Southern Europe.
Adobe's buildings are considered very vulnerable to powerful earthquakes. However, various ways of seismic reinforcement of new and existing adobe buildings are available.
The key factors for improving adobe's seismic construction performance are:
- Quality of construction.
- A compact box-type layout.
- seismic reinforcement.
Structure of limestone and sandstone
Limestone is very common in architecture, especially in North America and Europe. Many landmarks around the world are made of limestone. Many medieval churches and palaces in Europe are made of limestone and stone. They are long-lasting materials but their rather heavy weights are not beneficial for adequate seismic performance.
The application of modern technology to seismic retrofit can improve the resilience of masonry structures that are not opaque. For example, from 1973 to 1989, the Salt Lake City and County Buildings in Utah were completely renovated and refurbished with an emphasis on preserving historical accuracy in appearance. This is accompanied by a seismic increase that places weak sandstone structures on a basic insulation foundation to better protect against earthquake damage.
Wooden frame structure
Wood framing dates back thousands of years, and has been used in many parts of the world during different periods such as ancient Japan, Europe, and England in medieval times where wood is in good supply and building stones and skills to make it work.
The use of wood framing in buildings provides a complete framework framework that offers some structural benefits such as wooden frames, if properly designed, suitable for better earthquake resistance .
Skeletal-light structure
Light skeletal structures usually obtain seismic resistance from rigid shear plywood walls and wood structural panel diaphragms. Specific requirements for seismic load-bearing systems for all engineered wood structures require consideration of diaphragm ratios, horizontal and vertical diaphragm scissors, and connector/fastener values. In addition, the collector, or struts pull, to distribute the shear along the length of the diaphragm is required.
Massive brick structure
A construction system in which steel reinforcement is embedded in a mortar joint from a rock or placed in a hole and after being filled with concrete or nat is called bricklaying .
The devastating 1933 Long Beach Earthquake revealed that masonry construction should be upgraded soon. Later, the California State Code makes compulsory stones reinforced.
There are various practices and techniques to achieve reinforcement. The most common type is the reinforced hollow brick unit. The effectiveness of vertical and horizontal reinforcement is highly dependent on the type and quality of the masonry, which is the masonry and mortar units.
To achieve the ductile behavior of masonry, it is necessary that the shear strength of the wall is greater than the bending strength.
Structure of reinforced concrete
Reinforced concrete is a concrete in which reinforcement or fiber reinforcement has been incorporated to reinforce materials that would otherwise be brittle. It can be used to produce beams, columns, floors or bridges.
Prestressed concrete is a type of reinforced concrete used to overcome the natural weakness of concrete in tension. This can be applied to beams, floors or bridges with a longer than practical range with ordinary reinforced concrete. The prestressing tendon (generally from the tensile wire or high tensile steel rod) is used to provide a clamping load that produces a compressive stress which offsets the tensile stress experienced by the compression member of the concrete, otherwise exposed due to the bending load.
To prevent catastrophic destruction in response to earth vibrations (for survival), the traditional reinforced concrete framework must have a ductile connection. Depending on the method used and the forced seismic strength, the building can be immediately used, requires extensive repairs, or may have to be destroyed.
Prestressed Structure
The prestress structure is a structure whose integrity, stability and security as a whole depends, in particular, on a pratata . Achievement means the creation of intentional permanent pressure within the structure for the purpose of improving its performance under various service conditions.
There are basic prestress types:
- Pre-compression (mostly, with the weight of the structure itself)
- Pretend with high strength embedded tendons
- Attach tensioning with bonded or unbound bonded tendons
Today, the concept of prestressed structures is widely involved in the design of buildings, underground structures, TV towers, power plants, floating storage and offshore facilities, nuclear reactor vessels, and various types of bridge systems.
Useful ideas about pratata , apparently, familiar to the ancient Roman architects; see, for example, on the high-ceiling wall of the Colosseum that serves as a stabilizer for the pillars of the wall underneath. Steel Structure
Steel structure is considered earthquake resistant but several failures have occurred. A large number of temporarily welded steel skeletons, which appeared to be earthquake-proof, were surprisingly brittle and heavily damaged in the 1994 Northridge earthquake. After that, the Federal Emergency Management Agency (FEMA) initiated the development of improved techniques and new design approaches to minimize damage to the framework steel frame in the future earthquake.
For structural steel seismic design based on Load and Resistance Factor Design (LRFD) approaches, it is important to assess the structural ability to develop and maintain bearing resistance within the inelastic range. The measure of this ability is the ductility, which can be observed in the the material itself , within structural elements , or into the entire structure .
As a consequence of the Northridge earthquake experience, the American Steel Construction Institute has introduced AISC 358 "Pre-Qualified Connections for Special and Medium Steel Modeling Frameworks." The AISC Seismic Design Provisions require all Steel Moment Resisting Frames to use the connections contained in AISC 358, or the use of connections that have undergone pre-qualified cyclic testing.
Predicted earthquake loss
Estimated earthquake loss is usually defined as Damage Ratio ( DR ) which is the ratio of the cost of earthquake damage repair to the total value of a building. Maximum Loss Possibility ( PML ) is a generic term used to estimate seismic losses, but has no precise definition. In 1999, the ASTM E2026 Standard Assessment for Earthquake Damage Estimates' was produced to standardize the nomenclature for estimating seismic losses, as well as establishing guidelines for the review process and qualification of reviewers.
Estimated earthquake loss is also referred to as Seismic Risk Assessment . The risk assessment process generally involves determining the possibility of various ground movements associated with the vulnerability or damage to buildings under the movement of the land. The result is defined as the percent of building replacement value.
See also
- The Earthquake Engineering Research Institute
- Earthquake resistant structure
- Emergency management
- The facade
- Geotechnical engineering
- Institute of Earthquake Engineering and International Seismology
- List of international seismic coefficient of acceleration
- National Center for Research on Earthquake Engineering
- Probabilistic risk assessment
- Seismic intensity scale
- Seismic scale scale
- Seismic response from landfill
- Seismic retrofit
- Seismic site response
- Soil structure interactions
- Spectral acceleration
References
External links
- Earthquake engineering in Curlie (based on DMOZ)
- Earthquake Engineering Research Institute
- University Consortium for Research in Earthquake Engineering (CUREE)
- NHERI: Infrastructure research of natural hazard engineering
- Earthquakes and Earthquake Techniques at the Library of Congress
- Infrastructure Risk Research Project at University of British Columbia, Vancouver, Canada
Source of the article : Wikipedia
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