Seismic retrofit - Knowledge

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the 1960s, engineers began to regard welded steel moment-frame buildings as being among the most ductile systems contained in the building code. Many engineers believed that steel moment-frame buildings were essentially invulnerable to earthquake induced damage and thought that should damage occur, it would be limited to ductile yielding of members and connections. Observation of damage sustained by buildings in the 1994 Northridge earthquake indicated that contrary to the intended behavior, in many cases, brittle fractures initiated within the connections at very low levels of plastic demand. In September, 1994, The SAC joint Venture, AISC, AISI, and NIST jointly convened an international workshop in Los Angeles to coordinate the efforts of various participants and to lay the foundation for systematic investigation and resolution of the problem. In September 1995 the SAC Joint Venture entered into a contractual agreement with FEMA to conduct Phase II of the SAC Steel project. Under Phase II, SAC continued its extensive problem-focused study of the performance of moment resisting steel frames and connections of various configurations, with the ultimate goal of developing seismic design criteria for steel construction. As a result of these studies it is now known that the typical moment-resisting connection detail employed in steel moment frame construction prior to the 1994 Northridge earthquake had a number of features that rendered it inherently susceptible to brittle fracture.

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face a fireplace from floor to ceiling) can be especially dangerous to occupants. Older masonry chimneys are also dangerous if they have substantial vertical extension above the roof. These are prone to breakage at the roofline and may fall into the house in a single large piece. For retrofit, additional supports may be added; however, it is extremely expensive to strengthen an existing masonry chimney to conform with contemporary design standards. It is best to simply remove the extension and replace it with lighter materials, with special metal flue replacing the flue tile and a wood structure replacing the masonry. This may be matched against existing brickwork by using very thin veneer (similar to a tile, but with the appearance of a brick).

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amount of slip that can be accommodated without failure. These factors have resulted in the slip joint being designed too short to ensure survival of the tube under possible (perhaps even likely) large earthquakes in the region. To correct this deficiency the slip joint must be extended to allow for additional movement, a modification expected to be both expensive and technically and logistically difficult. Other retrofits to the BART tube include vibratory consolidation of the tube's overfill to avoid potential liquefying of the overfill, which has now been completed. (Should the overfill fail there is a danger of portions of the tube rising from the bottom, an event which could potentially cause failure of the section connections.)

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structure. Above the foundation and sill plate the connections are typically made using steel strap or sheet stampings, nailed to wood members using special hardened high-shear strength nails, and heavy angle stampings secured with through bolts, using large washers to prevent pull-through. Where inadequate bolts are provided between the sill plates and a foundation in existing construction (or are not trusted due to possible corrosion), special clamp plates may be added, each of which is secured to the foundation using expansion bolts inserted into holes drilled in an exposed face of concrete. Other members must then be secured to the sill plates with additional fittings.

710:. This low wall structure itself may fail in shear or in its connections to itself at the corners, leading to the building moving diagonally and collapsing the low walls. The likelihood of failure of the pin-up can be reduced by ensuring that the corners are well reinforced in shear and that the shear panels are well connected to each other through the corner posts. This requires structural grade sheet plywood, often treated for rot resistance. This grade of plywood is made without interior unfilled knots and with more, thinner layers than common plywood. New buildings designed to resist earthquakes will typically use OSB ( 1069: 977:

the three inner tubes. The intervening space was filled with concrete. At the bottom of the bay a trench was excavated and a flat bed of crushed stone prepared to receive the tube sections. The sections were then floated into place and sunk, then joined with bolted connections to previously placed sections. An overfill was then placed atop the tube to hold it down. Once completed from San Francisco to Oakland, the tracks and electrical components were installed. The predicted response of the tube during a major earthquake was likened to be as that of a string of (cooked)

1050: 755:(reinforcing bars) arranged in a ring, surrounded by lighter-gauge hoops of rebar. Upon analysis of failures due to earthquakes, it has been realized that the weakness was not in the vertical bars, but rather in inadequate strength and quantity of hoops. Once the integrity of the hoops is breached, the vertical rebar can flex outward, stressing the central column of concrete. The concrete then simply crumbles into small pieces, now unconstrained by the surrounding rebar. In new construction a greater amount of hoop-like structures are used. 1258:

substantial number of these at-risk masonry structures would have significant heritage value. Masonry walls that are not reinforced are especially hazardous. Such structures may be more appropriate for replacement than retrofit, but if the walls are the principal load bearing elements in structures of modest size they may be appropriately reinforced. It is especially important that floor and ceiling beams be securely attached to the walls. Additional vertical supports in the form of steel or reinforced concrete may be added.

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weaknesses are the connection from the wood-framed walls to the foundation and the relatively weak "cripple-walls." (Cripple walls are the short wood walls that extend from the top of the foundation to the lowest floor level in houses that have raised floors.) Adding connections from the base of the wood-framed structure to the foundation is almost always an important part of a seismic retrofit. Bracing the cripple-walls to resist side-to-side forces is essential in houses with cripple walls; bracing is usually done with

210: 1143:, where an entire viaduct, centrally supported by a single row of large columns, was laid down to one side. Such columns are reinforced by excavating to the foundation pad, driving additional pilings, and adding a new, larger pad, well connected with rebar alongside or into the column. A column with insufficient wrapping bar, which is prone to burst and then hinge at the bursting point, may be completely encased in a circular or elliptical jacket of welded steel sheet and grouted as described above. 237: 368:

moment-resisting system that has self-centering capacity. An extension of the same idea for seismic retrofitting has been experimentally tested for seismic retrofit of California bridges under a Caltrans research project and for seismic retrofit of non-ductile reinforced concrete frames. Pre-stressing can increase the capacity of structural elements such as beam, column and beam-column joints. External pre-stressing has been used for structural upgrade for gravity/live loading since the 1970s.

1030: 732:(frozen mud) as it keeps the building's warmth from destabilizing the ground beneath. During an earthquake, the pylons may tip, spilling the building to the ground. This can be overcome by using deep-bored holes to contain cast-in-place reinforced pylons, which are then secured to the floor panel at the corners of the building. Another technique is to add sufficient diagonal bracing or sections of concrete shear wall between pylons. 620: 1021:. During severe ground motion, the rockers may jump from their tracks or be moved beyond their design limits, causing the bridge to unship from its resting point and then either become misaligned or fail completely. Motion can be constrained by adding ductile or high-strength steel restraints that are friction-clamped to beams and designed to slide under extreme stress while still limiting the motion relative to the anchorage. 1169:. This viaduct was a two-level structure, and the upper portions of the columns were not well connected to the lower portions that supported the lower level; this caused the upper deck to collapse upon the lower deck. Weak connections such as these require additional external jacketing – either through external steel components or by a complete jacket of reinforced concrete, often using stub connections that are glued (using 687: 695: 544: 500:

detach from one another. The relative motion will then cause the two parts to collide, causing severe structural damage. Seismic modification will either tie the two building components rigidly together so that they behave as a single mass or it will employ dampers to expend the energy from relative motion, with appropriate allowance for this motion, such as increased spacing and sliding bridges between sections.

1147: 572: 741: 523: 198: 43: 478:, powered by electric pumps and accumulators, are actively driven to counter the wind forces and natural resonances. These may also, if properly designed, be effective in controlling excessive motion – with or without applied power – in an earthquake. In general, though, modern steel frame high rise buildings are not as subject to dangerous motion as are medium rise (eight to ten 401:, can be applied both to a newly designed building and to seismic upgrading of existing structures. Normally, excavations are made around the building and the building is separated from the foundations. Steel or reinforced concrete beams replace the connections to the foundations, while under these, the isolating pads, or base isolators, replace the material removed. While the 350: 229: 1126:

The stays, rather than being fixed to the beams, may instead be clamped to them. Under moderate loading, these keep the overpass centered in the gap so that it is less likely to slide off its founding shelf at one end. The ability for the fixed ends to slide, rather than break, will prevent the complete drop of the structure if it should fail to remain on the footings.

636:(FRP). Composite materials such as carbon FRP and aramic FRP have been extensively tested for use in seismic retrofit with some success. One novel technique includes the use of selective weakening of the beam and added external post-tensioning to the joint in order to achieve flexural hinging in the beam, which is more desirable in terms of seismic design. 190:. Whilst current practice of seismic retrofitting is predominantly concerned with structural improvements to reduce the seismic hazard of using the structures, it is similarly essential to reduce the hazards and losses from non-structural elements. It is also important to keep in mind that there is no such thing as an earthquake-proof structure, although 454:. The net dynamic response of the overall structure is reduced due to both the counteracting movement of mass, as well as energy dissipation or vibration damping which occurs when the fluid's kinetic energy is converted to heat by the baffles. Generally the temperature rise in the system will be minimal and is passively cooled by the surrounding air. 591:. In many buildings the ground level is designed for different uses than the upper levels. Low rise residential structures may be built over a parking garage which have large doors on one side. Hotels may have a tall ground floor to allow for a grand entrance or ballrooms. Office buildings may have retail stores on the ground floor with continuous 167:

In view of the imminent problem, various research work has been carried out. State-of-the-art technical guidelines for seismic assessment, retrofit and rehabilitation have been published around the world – such as the ASCE-SEI 41 and the New Zealand Society for Earthquake Engineering (NZSEE)'s guidelines. These codes must be regularly updated; the

474:"), when built using modern lightweight materials, might sway uncomfortably (but not dangerously) in certain wind conditions. A solution to this problem is to include at some upper story a large mass, constrained, but free to move within a limited range, and moving on some sort of bearing system such as an air cushion or hydraulic film. Hydraulic 2247:, the Association of Bay Area Governments, their web site includes much valuable information and interactive analysis tools. If you know or can reasonably estimate in the worst case the expected shaking index for your area you can still use the included home safety evaluation quiz, even if you are not located within the 947:) or the slope above the tunnel may be stabilized in some way. Where only small- to medium-sized rocks and boulders are expected to fall, the entire slope may be covered with wire mesh, pinned down to the slope with metal rods. This is also a common modification to highway cuts where appropriate conditions exist. 786:. Additional vertical and horizontal rebar is then secured to the new elements, a form is erected, and an additional layer of concrete is poured. This modification may be combined with additional footings in excavated trenches and additional support ledgers and tie-backs to retain the span on the bounding walls. 759:

additional pilings may be driven near the column base and concrete pads linking the pilings to the pylon are fabricated at or below ground level. In the example shown not all columns needed to be modified to gain sufficient seismic resistance for the conditions expected. (This location is about a mile from the

1442:.strategies are different from retrofit techniques, where the former is the basic approach to achieve an overall retrofit performance objective, such as increasing strength, increasing deformability, reducing deformation demands while the latter is the technical methods to achieve that strategy, for example 1125:

Another failure occurs when the fill at each end moves (through resonant effects) in bulk, in opposite directions. If there is an insufficient founding shelf for the overpass, then it may fall. Additional shelf and ductile stays may be added to attach the overpass to the footings at one or both ends.

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Elevated roadways are typically built on sections of elevated earth fill connected with bridge-like segments, often supported with vertical columns. If the soil fails where a bridge terminates, the bridge may become disconnected from the rest of the roadway and break away. The retrofit for this is to

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The engineers of the construction consortium PBTB (Parsons Brinckerhoff-Tudor-Bechtel) used the best estimates of ground motion available at the time, now known to be insufficient given modern computational analysis methods and geotechnical knowledge. Unexpected settlement of the tube has reduced the

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of water-saturated sand and/or mud. Generally, deep pilings must be driven into stable soil (typically hard mud or sand) or to underlying bedrock or the slope must be stabilized. For buildings built atop previous landslides the practicality of retrofit may be limited by economic factors, as it is not

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In masonry structures, brick building structures have been reinforced with coatings of glass fiber and appropriate resin (epoxy or polyester). In lower floors these may be applied over entire exposed surfaces, while in upper floors this may be confined to narrow areas around window and door openings.

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covering to enhance its performance. In many modern tract homes, especially those built upon expansive (clay) soil the building is constructed upon a single and relatively thick monolithic slab, kept in one piece by high tensile rods that are stressed after the slab has set. This poststressing places

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required, which consist of metal straps secured to vertical structural elements. These straps extend into mortar courses, securing the veneer to the primary structure. Older structures may not secure this sufficiently for seismic safety. A weakly secured veneer in a house interior (sometimes used to

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In many parts of developing countries such as Pakistan, Iran and China, unreinforced or in some cases reinforced masonry is the predominantly form of structures for rural residential and dwelling. Masonry was also a common construction form in the early part of the 20th century, which implies that a

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Vertical posts are secured to the beams or other members they support. This is particularly important where loss of support would lead to collapse of a segment of a building. Connections from posts to beams cannot resist appreciable side-to-side forces; it is much more important to strengthen around

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supply pipes to structures often prove especially dangerous during and after earthquakes. Should a building move from its foundation or fall due to cripple wall collapse, the ductile iron pipes transporting the gas within the structure may be broken, typically at the location of threaded joints. The

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up to twice the force of gravity have been measured. If a building is not secured to a well-embedded foundation it is possible for the building to be thrust from (or with) its foundations into the air, usually with severe damage upon landing. Even if it is well-founded, higher portions such as upper

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If the blocking or nailing is inadequate, each beam can be laid flat by the shear forces applied to the building. In this position they lack most of their original strength and the structure may further collapse. As part of a retrofit the blocking may be doubled, especially at the outer edges of the

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to form a subfloor upon which the finish floor surface is laid. In many structures these are all aligned in the same direction. To prevent the beams from tipping over onto their side, blocking is used at each end, and for additional stiffness, blocking or diagonal wood or metal bracing may be placed

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Traditional seismic design assumes that the lower stories of a building are stronger than the upper stories; where this is not the case—if the lower story is less strong than the upper structure—the structure will not respond to earthquakes in the expected fashion. Using modern design methods, it is

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Historic buildings, made of unreinforced masonry, may have culturally important interior detailing or murals that should not be disturbed. In this case, the solution may be to add a number of steel, reinforced concrete, or poststressed concrete columns to the exterior. Careful attention must be paid

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A slosh tank is a large container of low viscosity fluid (usually water) that may be placed at locations in a structure where lateral swaying motions are significant, such as the roof, and tuned to counter the local resonant dynamic motion. During a seismic (or wind) event the fluid in the tank will

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Supplementary dampers absorb the energy of motion and convert it to heat, thus damping resonant effects in structures that are rigidly attached to the ground. In addition to adding energy dissipation capacity to the structure, supplementary damping can reduce the displacement and acceleration demand

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is well acknowledged. Prior to the introduction of modern seismic codes in the late 1960s for developed countries (US, Japan etc.) and late 1970s for many other parts of the world (Turkey, China etc.), many structures were designed without adequate detailing and reinforcement for seismic protection.

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Selected vertical elements (typically the posts at the ends of plywood wall bracing panels) are connected to the foundation. These connections are intended to prevent the braced walls from rocking up and down when subjected to back-and-forth forces at the top of the braced walls, not to resist the

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adhesive) into numerous drilled holes. These stubs are then connected to additional wrappings, external forms (which may be temporary or permanent) are erected, and additional concrete is poured into the space. Large connected structures similar to the Cypress Viaduct must also be properly analyzed

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Large sections of roadway may consist entirely of viaduct, sections with no connection to the earth other than through vertical columns. When concrete columns are used, the detailing is critical. Typical failure may be in the toppling of a row of columns due either to soil connection failure or to

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through an innovative process. Rather than pushing a shield through the soft bay mud, the tube was constructed on land in sections. Each section consisted of two inner train tunnels of circular cross section, a central access tunnel of rectangular cross section, and an outer oval shell encompassing

887:, carrying entire sections of suburban development to new locations. While the most modern of house structures (well tied to monolithic concrete foundation slabs reinforced with post tensioning cables) may survive such movement largely intact, the building will no longer be in its proper location. 727:

Some older low-cost structures are elevated on tapered concrete pylons set into shallow pits, a method frequently used to attach outdoor decks to existing buildings. This is seen in conditions of damp soil, especially in tropical conditions, as it leaves a dry ventilated space under the house, and

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Following the Northridge earthquake, a number of steel moment -frame buildings were found to have experienced brittle fractures of beam to column connections. Discovery of these unanticipated brittle fractures of framing connections was alarming to engineers and the building industry. Starting in

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tends to restrict transmission of the ground motion to the building, it also keeps the building positioned properly over the foundation. Careful attention to detail is required where the building interfaces with the ground, especially at entrances, stairways and ramps, to ensure sufficient relative

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of the perimeter wall erected upon the floor diaphragm, although this will require exposing the sill plate by removing interior plaster or exterior siding. As the sill plate may be quite old and dry and substantial nails must be used, it may be necessary to pre-drill a hole for the nail in the old

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Beam-column joint connections are a common structural weakness in dealing with seismic retrofitting. Prior to the introduction of modern seismic codes in early 1970s, beam-column joints were typically non-engineered or designed. Laboratory testings have confirmed the seismic vulnerability of these

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Most houses in North America are wood-framed structures. Wood is one of the best materials for earthquake-resistant construction since it is lightweight and more flexible than masonry. It is easy to work with and less expensive than steel, masonry, or concrete. In older homes the most significant

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Many short bridge spans are statically anchored at one end and attached to rockers at the other. This rocker gives vertical and transverse support while allowing the bridge span to expand and contract with temperature changes. The change in the length of the span is accommodated over a gap in the

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In some cases, the best that can be done is to reduce the entrance of water runoff from higher, stable elevations by capturing and bypassing through channels or pipes, and to drain water infiltrated directly and from subsurface springs by inserting horizontal perforated tubes. There are numerous

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or beam-column joint shear failures. Local failure of the infill panels due to in and out-of-plane mechanisms, but also due to their combination, can lead to a sudden drop in capacity and hence cause global brittle failure of the structure. Even at lower intensity earthquakes, damage to infilled

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Recently more holistic approaches to building retrofitting are being explored, including combined seismic and energy retrofitting. Such combined strategies aim to exploit cost savings by applying energy retrofitting and seismic strengthening interventions at once, hence improving the seismic and

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For reinforced concrete beam-column joints – various retrofit solutions have been proposed and tested in the past 20 years. Philosophically, the various seismic retrofit strategies discussed above can be implemented for reinforced concrete joints. Concrete or steel jacketing have been a popular

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Frequently, building additions will not be strongly connected to the existing structure, but simply placed adjacent to it, with only minor continuity in flooring, siding, and roofing. As a result, the addition may have a different resonant period than the original structure, and they may easily

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Concrete walls are often used at the transition between elevated road fill and overpass structures. The wall is used both to retain the soil and so enable the use of a shorter span and also to transfer the weight of the span directly downward to footings in undisturbed soil. If these walls are

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Increasing the local capacity of structural elements. This strategy recognises the inherent capacity within the existing structures, and therefore adopts a more cost-effective approach to selectively upgrade local capacity (deformation/ductility, strength or stiffness) of individual structural

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Shown here is an exterior shear reinforcement of a conventional reinforced concrete dormitory building. In this case, there was sufficient vertical strength in the building columns and sufficient shear strength in the lower stories that only limited shear reinforcement was required to make it

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may respond to earthquakes with a side-to-side motion exceeding that which was designed for wind gust response. Such motion can cause fragmentation of the road surface, damage to bearings, and plastic deformation or breakage of components. Devices such as hydraulic dampers or clamped sliding

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Good practices in modern, earthquake-resistant structures dictate that there be good vertical connections throughout every component of the building, from undisturbed or engineered earth to foundation to sill plate to vertical studs to plate cap through each floor and continuing to the roof

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One simple retrofit is to surround the column with a jacket of steel plates formed and welded into a single cylinder. The space between the jacket and the column is then filled with concrete, a process called grouting. Where soil or structure conditions require such additional modification,

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Single or two-story wood-frame domestic structures built on a perimeter or slab foundation are relatively safe in an earthquake, but in many structures built before 1950 the sill plate that sits between the concrete foundation and the floor diaphragm (perimeter foundation) or studwall (slab

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The most common form of seismic retrofit to lower buildings is adding strength to the existing structure to resist seismic forces. The strengthening may be limited to connections between existing building elements or it may involve adding primary resisting elements such as walls or frames,

438:(TMD) employ movable weights on some sort of springs. These are typically employed to reduce wind sway in very tall, light buildings. Similar designs may be employed to impart earthquake resistance in eight to ten story buildings that are prone to destructive earthquake induced resonances. 367:

The use of external post-tensioning for new structural systems have been developed in the past decade. Under the PRESS (Precast Seismic Structural Systems), a large-scale U.S./Japan joint research program, unbonded post-tensioning high strength steel tendons have been used to achieve a

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Side-to-side forces cause most earthquake damage. Bolting of the mudsill to the foundation and application of plywood to cripple walls are a few basic retrofit techniques which homeowners may apply to wood-framed residential structures to mitigate the effects of seismic activity. The

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and has also been heat-treated, it is not subject to either the plastic shear failure typical of hot rivets nor the brittle fracture of ordinary bolts. Any partial failure will be in the plastic flow of the metal secured by the bolt; with proper engineering any such failure should be

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Public safety only. The goal is to protect human life, ensuring that the structure will not collapse upon its occupants or passersby, and that the structure can be safely exited. Under severe seismic conditions the structure may be a total economic write-off, requiring tear-down and

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Widespread weld failures at beam-column joints of low-to-medium rise steel buildings during the Northridge 1994 earthquake for example, have shown the structural defiencies of these 'modern-designed' post-1970s welded moment-resisting connections. A subsequent SAC research project

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The safety of underwater tubes is highly dependent upon the soil conditions through which the tunnel was constructed, the materials and reinforcements used, and the maximum predicted earthquake expected, and other factors, some of which may remain unknown under current knowledge.

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has documented, tested and proposed several retrofit solutions for these welded steel moment-resisting connections. Various retrofit solutions have been developed for these welded joints – such as a) weld strengthening and b) addition of steel haunch or 'dog-bone' shape flange.

462:. In order to be effective the mass of the liquid is usually on the order of 1% to 5% of the mass it is counteracting, and often this requires a significant volume of liquid. In some cases these systems are designed to double as emergency water cisterns for fire suppression. 795:

This application provides tensile strength that stiffens the wall against bending away from the side with the application. The efficient protection of an entire building requires extensive analysis and engineering to determine the appropriate locations to be treated.

1237:), the upper walls are connected to the lower walls with tension elements. In some cases, connections may be extended vertically to include retention of certain roof elements. This sort of strengthening is usually very costly with respect to the strength gained. 610:

bents are useful in preserving lower story garage access, while a lower cost solution may be to use shear walls or trusses in several locations, which partially reduce the usefulness for automobile parking but still allow the space to be used for other storage.

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Structure survivability. The goal is that the structure, while remaining safe for exit, may require extensive repair (but not replacement) before it is generally useful or considered safe for occupation. This is typically the lowest level of retrofit applied to

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practical to stabilize a large, deep landslide. The likelihood of landslide or soil failure may also depend upon seasonal factors, as the soil may be more stable at the beginning of a wet season than at the beginning of the dry season. Such a "two season"

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particularly in the lower stories. Common retrofit measures for unreinforced masonry buildings in the Western United States include the addition of steel frames, the addition of reinforced concrete walls, and in some cases, the addition of base isolation.

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Unless the tunnel penetrates a fault likely to slip, the greatest danger to tunnels is a landslide blocking an entrance. Additional protection around the entrance may be applied to divert any falling material (similar as is done to divert snow

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foundation) may not be sufficiently bolted in. Additionally, older attachments (without substantial corrosion-proofing) may have corroded to a point of weakness. A sideways shock can slide the building entirely off of the foundations or slab.

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Structure functionality. Primary structure undamaged and the structure is undiminished in utility for its primary application. A high level of retrofit, this ensures that any required repairs are only "cosmetic" – for example, minor cracks in

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To prevent masonry infill damage and failure, typical retrofit strategies aim to strengthen the infills and provide adequate connection to the frame. Examples of retrofit techniques for masonry infills include steel reinforced plasters,

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consist of two "I"-beams connected with a criss-cross lattice of flat strap or angle stock. These can be greatly strengthened by replacing the open lattice with plate members. This is usually done in concert with the replacement of hot

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In other circumstances, far greater reinforcement is required. In the structure shown at right — a parking garage over shops — the placement, detailing, and painting of the reinforcement becomes itself an architectural embellishment.

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The lowest plate rails of walls (usually called "mudsills" or "foundation sills" in North America) are bolted to a continuous foundation, or secured with rigid metal connectors bolted to the foundation so as to resist side-to-side

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locations in California where extensive developments have been built atop archaic landslides, which have not moved in historic times but which (if both water-saturated and shaken by an earthquake) have a high probability of moving

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Pampanin, S., Bolognini, D., Pavese, A. (2007) Performance-based Seismic Retrofit Strategy for Existing Reinforced Concrete Frame Systems using FRP composites. ASCE Journal of Composites for Construction, 11(2), pp. 211–226.

1316: 1089:(soft) condition, while the plate, having been hot rolled and quenched during manufacture, remains relatively hard. Under extreme stress the hard plates can shear the soft rivets, resulting in failure of the joint. 1758:

Park, R. (2002). A Summary of Result of Simulated Seismic Load Tests on Reinforced Concrete Beam-Column Joints, Beams and Columns with Substandard Reinforcing Details. Journal of Earthquake Engineering, 6(2),

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of 1886. They could be tightened and loosened to support the house without having to otherwise demolish the house due to instability. The bolts were directly loosely connected to the supporting frame of the

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Performance of steel building structures during the Northridge earthquake. Report No UCB/EERC-94/09. Berkeley, California: Earthquake Engineering Research Center, University of California at Berkeley. 1994.

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A caged metal ball may be arranged at the edge of an orifice. Upon seismic shock, the ball will roll into the orifice, sealing it to prevent gas flow. The ball may later be reset by the use of an external

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Typically, where this type of problem is found, the weak story is reinforced to make it stronger than the floors above by adding shear walls or moment frames. Moment frames consisting of inverted

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In two-story buildings using "platform framing" (sometimes called "western" style construction, where walls are progressively erected upon the lower story's upper diaphragm, unlike "eastern" or

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poorly detailed and under-designed connections. Failure of beam-column joint connections can typically lead to catastrophic collapse of a frame-building, as often observed in recent earthquakes

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Seismic retrofit (or rehabilitation) strategies have been developed in the past few decades following the introduction of new seismic provisions and the availability of advanced materials (e.g.

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gas may then still be provided to the pressure regulator from higher pressure lines and so continue to flow in substantial quantities; it may then be ignited by a nearby source such as a lit

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Park R, Billings IJ, Clifton GC, Cousins J, Filiatrault A, Jennings DN, et al. The Hyogo-ken Nanbu Earthquake of 17 January 1995. Bull of New Zealand Soc of earthquake Eng. 1995;28(1):1 -99.

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There are two primary methods of automatically restraining the flow of gas after an earthquake, installed on the low pressure side of the regulator, and usually downstream of the gas meter.

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In the past, seismic retrofit was primarily applied to achieve public safety, with engineering solutions limited by economic and political considerations. However, with the development of

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Often such buildings, especially if constructed on a moderate slope, are erected on a platform connected to a perimeter foundation through low stud-walls called "cripple wall" or

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interfaces in a "beach like" structure against underlying firm material, seismic waves traveling through the alluvium can be amplified, just as are water waves against a sloping

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in San Francisco is a skyscraper with a rooftop slosh tank which was designed primarily to reduce the magnitude of lateral swaying motion from wind. A slosh tank is a passive

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Selective weakening retrofit. This is a counter-intuitive strategy to change the inelastic mechanism of the structure, while recognising the inherent capacity of the structure.

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slosh back and forth with the fluid motion usually directed and controlled by internal baffles – partitions that prevent the tank itself becoming resonant with the structure,

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wood to avoid splitting. When the wall is opened for this purpose it may also be appropriate to tie vertical wall elements into the foundation using specialty connectors and

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Wooden framing is efficient when combined with masonry, if the structure is properly designed. In Turkey, the traditional houses (bagdadi) are made with this technology. In

1480:"Concurrent seismic and energy retrofitting of RC and masonry building envelopes using inorganic textile-based composites combined with insulation materials: A new concept" 1749:

Calvi, G. M., Moratti, M., and Pampanin, S. (2002). Relevance of beam-column damage and collapse in RC frame assessment. Journal of Earthquake Engineering, 6(1), 75–100.

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add additional reinforcement to any supporting wall, or to add deep caissons adjacent to the edge at each end and connect them with a supporting beam under the bridge.

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are considered non-structural elements, but damage to infills can lead to large repair costs and change the behaviour of a structure, even leading to aforementioned

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the perimeter of a building (bracing the cripple-walls and supplementing foundation-to-wood-framing connections) than it is to reinforce post-to-beam connections.

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Many older structures were fabricated by inserting red-hot rivets into pre-drilled holes; the soft rivets are then peened using an air hammer on one side and a

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A. Ghobarah and A. Said 2001 Seismic rehabilitation of beam-column joints using FRP laminates. Journal of Earthquake Engineering, Vol. 5, No. 1, pp. 113–129.

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Civjan SA, Engelhardt MD and Gross JD (2000). Retrofit of pre-Northridge Moment Resisting Connections. ASCE J.o.Structural Engineering Vol 126(4) 445–452

162:. With better understanding of seismic demand on structures and with recent experiences with large earthquakes near urban centers, the need of seismic 1285: 1410: 665:

between beams at one or more points in their spans. At the outer edge it is typical to use a single depth of blocking and a perimeter beam overall.

599:

possible to take a weak lower story into account. Several failures of this type in one large apartment complex caused most of the fatalities in the

1817: 1623: 1261:

In the western United States, much of what is seen as masonry is actually brick or stone veneer. Current construction rules dictate the amount of

2045:"Cyclic Response of Nonductile Reinforced Concrete Frames with Unreinforced Masonry Infills Retrofitted with Engineered Cementitious Composites" 719:

the concrete under compression – a condition under which it is extremely strong in bending and so will not crack under adverse soil conditions.

482:) buildings, as the resonant period of a tall and massive building is longer than the approximately one second shocks applied by an earthquake. 389:

that should substantially decouple the building's structure from the shaking ground thus protecting the building's integrity and enhancing its

1740:

Implications of experimental on the seismic behaviour of gravity load designed RC beam-column connections. Earthquake Spectra, 12(2), 185–198.

1212:. Oriented strand board (OSB) does not perform as consistently as plywood, and is not the favored choice of retrofit designers or installers. 1191:. Public awareness and initiative are critical to the retrofit and preservation of existing building stock, and such efforts as those of the 1311: 1306: 2264: 1644: 1527:. Climamed 2017 – Mediterranean Conference of HVAC Historical buildings retrofit in the Mediterranean area 12–13 May 2017 - Matera, Italy. 1393: 1957:"Experimental study on the behaviour of nonductile infilled RC frames strengthened with external mesh reinforcement and plaster composite" 1633: 2306: 2244: 1192: 1104:, consisting of a head, a shaft matching the reamed hole, and a threaded end is inserted and retained with a nut, then tightened with a 930:). This device will operate independently of seismic motion, but will not respond to minor leaks which may be caused by an earthquake. 285:

Allowing sliding connections such as passageway bridges to accommodate additional movement between seismically independent structures.

1455: 415:

within the structures. In some cases, the threat of damage does not come from the initial shock itself, but rather from the periodic

2240: 1439: 1420: 1196: 812: 126: 60: 1153:

viaduct collapse. Note failure of inadequate anti-burst wrapping and lack of connection between upper and lower vertical elements.

1788: 856:

One of the most difficult retrofits is that required to prevent damage due to soil failure. Soil failure can occur on a slope, a

2327: 1798:

A. Ghobarah and A. Said. 2002. Shear strengthening of beam-column joints. Engineering Structures, Vol. 24, No. 7, pp. 881- 888.

844:

stories or roof structures or attached structures such as canopies and porches may become detached from the primary structure.

633: 264:

Increasing the global capacity (strengthening). This is typically done by the addition of cross braces or new structural walls.

107: 1068: 926:

A flow-sensitive device may be used to close a valve if the flow of gas exceeds a set threshold (very much like an electrical

302: 2237:– Retrofit Solutions for New Zealand – research group dedicated to seismic retrofit. Contacts and publications are available. 2234: 1562:"Energy performance of existing residential buildings in Europe: A novel approach combining energy with seismic retrofitting" 79: 64: 1375: 419:

motion of the structure that repeated ground motion induces. In the practical sense, supplementary dampers act similarly to

2251:. There are other sections generally applicable for any potential level of seismic activity, such as securing furnishings. 1849:

FEMA 350, July 2000. Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings.1.3, pages 1–3 through 1–11.

1777:

Holmes WT, Somers P. Northridge earthquake Reconnaissance Report. Supplement C, vol. 2. earthquake Spectra. 1996(11):1–278.

2193:"Seismic retrofit of infilled RC frames with textile reinforced mortars: State-of-the-art review and analytical modelling" 1295: 1093: 990: 86: 1720: 240: 1215:

Retrofit methods in older wood-frame structures may consist of the following, and other methods not described here.

1861:"The structural role played by masonry infills on RC building performances after the 2011 Lorca, Spain, earthquake" 1049: 1029: 820: 748: 600: 354: 288:

Addition of seismic friction dampers to simultaneously add damping and a selectable amount of additional stiffness.

168: 2083: 93: 2004:

Koutromanos, Ioannis; Kyriakides, Marios; Stavridis, Andreas; Billington, Sarah; Shing, P. Benson (August 2013).

257: 337:

Structure unaffected. This level of retrofit is preferred for historic structures of high cultural significance.

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Extensive article including some structural retrofits and a comparison of various natural gas safety shutoffs:

1443: 1136: 840: 816: 253: 75: 2284: 1184: 53: 2248: 2123:"Analysis and design of FRP composites for seismic retrofit of infill walls in reinforced concrete frames" 1338: 1280: 1166: 1086: 580: 394: 353:

One of many "earthquake bolts" found throughout period houses in the city of Charleston subsequent to the

209: 31: 2099: 1521:"The energy efficiency challenge for a historical building undergone to seismic and energy refurbishment" 1426: 2332: 1859:

De Luca, Flavia; Verderame, Gerardo M.; Gómez-Martínez, Fernando; Pérez-García, Agustín (October 2014).

1290: 871: 711: 236: 2295: 1157:

Sometimes viaducts may fail in the connections between components. This was seen in the failure of the

2309:

Highlights Large Scale Bridge Building & Engineering Techniques in a Seismically Active Quake Zone

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It appears that the most secure configuration would be to use one of each of these devices in series.

1968: 1466: 1361: 424: 2153: 2044: 2005: 623:

Corner joint steel reinforcement and high tensile strength rods with grouted anti-burst jacket below

1917: 1601:

1994 Building Publications – Status of the U.S. Precast Seismic Structural Systems (PRESSS) Program

1328: 1275: 1162: 803: 566: 390: 191: 1519:

Nardi, Iole; de Rubeis, Tullio; Taddei, Marilena; Ambrosini, Dario; Sfarra, Stefano (2017-10-01).

2290: 2122: 1898: 1703: 760: 532: 435: 2253:

This is an especially valuable reference for any resident of an area subject to seismic activity

1390: 2006:"Shake-Table Tests of a 3-Story Masonry-Infilled RC Frame Retrofitted with Composite Materials" 1676:"Towards realistic minimum-cost optimization of viscous fluid dampers for seismic retrofitting" 775:

One form of retrofit is to drill numerous holes into the surface of the wall, and secure short

2214: 2173: 2103: 2064: 2025: 1986: 1937: 1890: 1828: 1695: 1583: 1542: 1501: 1416: 1343: 1188: 1037: 973: 865: 656:

Floors in wooden buildings are usually constructed upon relatively deep spans of wood, called

459: 398: 268: 143: 100: 2277:

Infrastructure Risk Research Project at The University of British Columbia, Vancouver, Canada

2257: 2204: 2165: 2134: 2095: 2056: 2017: 1976: 1929: 1880: 1872: 1687: 1573: 1532: 1491: 175: 174:

The retrofit techniques outlined here are also applicable for other natural hazards such as

2169: 2060: 2021: 1955:

Korkmaz, S. Z.; Kamanli, M.; Korkmaz, H. H.; Donduren, M. S.; Cogurcu, M. T. (2010-11-18).

2287:

pamphlet illustrating simple house structural improvements that the homeowner can perform.

1651: 1397: 1379: 1158: 1150: 1018: 982: 927: 619: 592: 455: 1972: 1323: 1057: 985:. To avoid overstressing the tube due to differential movements at each end, a sliding 772:

inadequate they may crumble under the stress of an earthquake's induced ground motion.

686: 450: 420: 402: 377: 272: 2300: 2209: 2192: 2138: 1956: 1622:

Experimental testing of external post-tensioning for retrofit of RC beam-column joint

1560:

Pohoryles, Daniel; Maduta, Carmen; Bournas, Dionysios; Kouris, Leonidas (2020-09-15).

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to the connections with other members such as footings, top plates, and roof trusses.

2316: 1902: 1860: 1816:

Selective weakening and post-tensioning for seismic retrofit of RC beam-column joint

1707: 969: 857: 576: 151: 1600: 2260:

Also from ABAG, these will require further approval by the local building official.

675: 194:

can be greatly enhanced through proper initial design or subsequent modifications.

187: 163: 27:

Modification of existing structures to make them more resistant to seismic activity

2154:"Seismic Strengthening of Masonry-Infilled RC Frames with TRM: Experimental Study" 1578: 1561: 1146: 1135:

insufficient cylindrical wrapping with rebar. Both failures were seen in the 1995

964:

A tube of particular structural, seismic, economic, and political interest is the

571: 2281: 1537: 1520: 1372: 1933: 1246: 1140: 1082: 904: 895: 799: 740: 522: 471: 218: 197: 42: 1981: 1611: 17: 1876: 1691: 1333: 986: 876: 729: 670: 159: 147: 2218: 2177: 2107: 2068: 2029: 1990: 1941: 1894: 1699: 1587: 1546: 1505: 575:

Partial failure due to inadequate shear structure at garage level. Damage in

232:

External bracing of an existing reinforced concrete parking garage (Berkeley)

1922:

Proceedings of the Institution of Civil Engineers - Structures and Buildings

1675: 978: 944: 908: 861: 698:

Low cripple wall collapse and detachment of structure from concrete stairway

416: 349: 228: 2303:(Loma Prieta Earthquake), U. S. Geological Survey Professional Paper 1152–A 305:(PBEE), several levels of performance objectives are gradually recognised: 2084:"Behavior of FRP Strengthened Infill Walls under In-Plane Seismic Loading" 1612:

Lowes & Moehle (1998) – ACI Structural Journal Vol 96(4) – pp 519–532

1467:

e.g. Kam & Pampanin (2008)- Selective weakening retrofit for RC frames

1300: 832: 783: 386: 331: 1885: 1230:

wall or house "jumping" off the foundation (which almost never occurs).

1209: 899: 661: 323: 319: 179: 1187:

created guidelines for these procedures, as outlined in the following

171:

brought to light the brittleness of welded steel frames, for example.

1105: 1097: 1005: 920: 715: 714:), sometimes with metal joins between panels, and with well attached 475: 346:

Common seismic retrofitting techniques fall into several categories:

327: 669:

building. It may be appropriate to add additional nails between the

632:

retrofit technique until the advent of composite materials such as

1170: 1145: 1109: 1062: 1033:

Additional diagonals were inserted under both decks of this bridge

1028: 836: 780: 752: 739: 693: 685: 657: 618: 542: 521: 479: 348: 235: 227: 222: 214: 208: 202: 196: 2282:

How the City of San Leandro can help you strengthen your home ...

2307:

Raising the Bar: Engineering the New East Span of the Bay Bridge

1108:. As the bolt has been formed from an appropriate high-strength 1041:

connections and additional diagonal reinforcement may be added.

965: 183: 155: 2152:

Koutas, L.; Bousias, S. N.; Triantafillou, T. C. (April 2015).

2258:

Standard engineered plan sets for residential seismic retrofit

1916:

Altın, S.; Anıl, Ö.; Kopraman, Y.; Belgin, Ç. (October 2010).

989:

was included at the San Francisco terminus under the landmark

678:

glued with epoxy cement into holes drilled in the foundation.

36: 2276: 2121:

Binici, Baris; Ozcebe, Guney; Ozcelik, Ramazan (July 2007).

1918:"Strengthening masonry infill walls with reinforced plaster" 1085:

on the head end. As these cool slowly, they are left in an

779:-shaped sections of rebar to the surface of each hole with 641: 495:

Connections between buildings and their expansion additions

1731:

Beres, A., Pessiki, S., White, R., and Gergely, P. (1996).

807:

frames can lead to high economic losses and loss of life.

267:

Reduction of the seismic demand by means of supplementary

2082:

Almusallam, Tarek H.; Al-Salloum, Yousef A. (June 2007).

1249:, wood and bamboo are used for residential construction. 1096:. The hole is then prepared to a precise diameter with a 744:

Jacketed and grouted column on left, unmodified on right

1674:

Pollini, Nicolò; Lavan, Oren; Amir, Oded (2016-03-01).

1440:

Moehle, J. (2000) State of Research on Seismic Retrofit

330:. This is the minimum acceptable level of retrofit for 2043:

Kyriakides, M. A.; Billington, S. L. (February 2014).

1174:

in their entirety using dynamic computer simulations.

1072:

Bolted plate lattice replacement, forming box members

1412:

Earthquakes and Engineers: An International History

1303:– Open System for Earthquake Engineering Simulation 486:

Ad hoc addition of structural support/reinforcement

67:. Unsourced material may be challenged and removed. 923:. This device will respond only to ground motion. 682:Sliding off foundation and "cripple wall" failure 531:earthquake resistant for this location near the 1092:The solution is to burn out each rivet with an 205:— University of California dormitory, Berkeley 2191:Pohoryles, D.A.; Bournas, D.A. (2020-02-15). 972:. This tube was constructed at the bottom of 8: 1415:. Reston, VA: ASCE Press. pp. 486–487. 385:is a collection of structural elements of a 2266:The Homeowner's Guide to Earthquake Safety 660:, covered with a diagonal wood planking or 798:In reinforced concrete buildings, masonry 751:typically contain large diameter vertical 2208: 1980: 1961:Natural Hazards and Earth System Sciences 1884: 1577: 1536: 1495: 1286:Earthquake Engineering Research Institute 127:Learn how and when to remove this message 1067: 1048: 570: 303:Performance-based earthquake engineering 30:For broader coverage of this topic, see 1354: 397:technology, which is a kind of seismic 2323:Earthquake and seismic risk mitigation 2158:Journal of Composites for Construction 2100:10.1061/(ASCE)1090-0268(2007)11:3(308) 2088:Journal of Composites for Construction 2296:FEMA Seismic Retrofit Cost Calculator 406:motion of those structural elements. 7: 2301:Performance of the Built Environment 1478:Bournas, Dionysios A. (2018-09-01). 652:Shear failure within floor diaphragm 65:adding citations to reliable sources 1253:Reinforced and unreinforced masonry 1199:to seismically active communities. 1193:Association of Bay Area Governments 831:Where moist or poorly consolidated 2235:Retrofit Solutions for New Zealand 2170:10.1061/(ASCE)CC.1943-5614.0000507 2061:10.1061/(ASCE)ST.1943-541X.0000833 2022:10.1061/(ASCE)ST.1943-541X.0000689 1865:Bulletin of Earthquake Engineering 1680:Bulletin of Earthquake Engineering 813:engineered cementitious composites 504:Exterior reinforcement of building 293:thermal performance of buildings. 25: 2210:10.1016/j.compositesb.2019.107702 2139:10.1016/j.compositesb.2006.08.007 2049:Journal of Structural Engineering 2010:Journal of Structural Engineering 1497:10.1016/j.compositesb.2018.04.002 1307:San Francisco–Oakland Bay Bridge 1053:Obsolete riveted lattice members 1045:Lattice girders, beams, and ties 790:Damage to masonry (infill) walls 736:Reinforced concrete column burst 142:is the modification of existing 41: 2291:Seismic Rehabilitation Handbook 1456:Filiatrault & Cherry (1986) 891:Utility pipes and cables: risks 839:. In these special conditions, 634:Carbon fiber-reinforced polymer 587:This collapse mode is known as 254:fiber-reinforced polymers (FRP) 146:to make them more resistant to 52:needs additional citations for 2241:ABAG Home Quake Safety Toolkit 2197:Composites Part B: Engineering 2127:Composites Part B: Engineering 1827:Bertero VV, Anderson JC & 1484:Composites Part B: Engineering 1362:NZSEE Bulletin 39(2)-June 2006 1195:are instrumental in providing 819:(FRP), and most recently also 767:Reinforced concrete wall burst 728:in far northern conditions of 723:Multiple piers in shallow pits 1: 1645:Clark Construction Group, LLC 1634:VSL Repair/Strengthening Page 1579:10.1016/j.enbuild.2020.110024 615:Beam-column joint connections 1538:10.1016/j.egypro.2017.09.357 1296:Mitigation of seismic motion 1008:have several failure modes. 690:House slid off of foundation 1934:10.1680/stbu.2010.163.5.331 1409:Reitherman, Robert (2012). 864:, or in a flat area due to 749:Reinforced concrete columns 241:Port Authority Bus Terminal 2349: 1982:10.5194/nhess-10-2305-2010 821:textile-reinforced mortars 601:1994 Northridge earthquake 564: 556:Typical retrofit solutions 539:Massive exterior structure 375: 260:and high strength steel). 169:1994 Northridge earthquake 29: 1877:10.1007/s10518-013-9500-1 1692:10.1007/s10518-015-9844-9 968:(Bay Area Rapid Transit) 817:fibre-reinforced polymers 509:Exterior concrete columns 258:fiber reinforced concrete 1317:Eastern span replacement 1226:are braced with plywood. 1137:Great Hanshin earthquake 363:External post-tensioning 2285:San Leandro, California 1197:informational resources 911:electrical connection. 2328:Earthquake engineering 2249:San Francisco Bay Area 1339:Tsunami-proof building 1281:Earthquake engineering 1167:Loma Prieta earthquake 1154: 1073: 1054: 1034: 841:vertical accelerations 745: 699: 691: 624: 584: 548: 527: 470:Very tall buildings (" 425:automotive suspensions 395:earthquake engineering 359: 297:Performance objectives 244: 233: 225: 206: 32:Earthquake engineering 1312:Western span retrofit 1291:Earthquake simulation 1149: 1071: 1052: 1032: 1017:roadway by comb-like 872:Mediterranean climate 743: 712:oriented strand board 697: 689: 622: 574: 546: 525: 466:Active control system 410:Supplementary dampers 355:Charleston earthquake 352: 239: 231: 212: 200: 1566:Energy and Buildings 1203:Wood frame structure 1178:Residential retrofit 518:Infill shear trusses 140:Seismic retrofitting 61:improve this article 1973:2010NHESS..10.2305K 1329:Seismic performance 1276:Destructive testing 1185:City of San Leandro 1163:Oakland, California 875:is seen throughout 589:soft story collapse 567:Soft story building 391:seismic performance 192:seismic performance 1650:2008-04-21 at the 1396:2008-11-20 at the 1378:2013-03-03 at the 1155: 1113:non-catastrophic. 1074: 1055: 1038:Suspension bridges 1035: 761:Hayward Fault Zone 746: 700: 692: 625: 585: 561:Soft-story failure 549: 528: 436:Tuned mass dampers 431:Tuned mass dampers 360: 245: 234: 226: 207: 76:"Seismic retrofit" 1967:(11): 2305–2316. 1344:Vibration control 1117:Fill and overpass 1012:Expansion rockers 974:San Francisco Bay 460:tuned mass damper 399:vibration control 176:tropical cyclones 137: 136: 129: 111: 16:(Redirected from 2340: 2223: 2222: 2212: 2188: 2182: 2181: 2149: 2143: 2142: 2133:(5–6): 575–583. 2118: 2112: 2111: 2079: 2073: 2072: 2040: 2034: 2033: 2016:(8): 1340–1351. 2001: 1995: 1994: 1984: 1952: 1946: 1945: 1913: 1907: 1906: 1888: 1871:(5): 1999–2026. 1856: 1850: 1847: 1841: 1838: 1832: 1825: 1819: 1814: 1808: 1805: 1799: 1796: 1790: 1784: 1778: 1775: 1769: 1766: 1760: 1756: 1750: 1747: 1741: 1738: 1732: 1729: 1723: 1718: 1712: 1711: 1671: 1665: 1660: 1654: 1642: 1636: 1631: 1625: 1620: 1614: 1609: 1603: 1598: 1592: 1591: 1581: 1557: 1551: 1550: 1540: 1516: 1510: 1509: 1499: 1475: 1469: 1464: 1458: 1453: 1447: 1437: 1431: 1430: 1425:. Archived from 1406: 1400: 1388: 1382: 1370: 1364: 1359: 1019:expansion joints 951:Underwater tubes 243:in New York City 148:seismic activity 132: 125: 121: 118: 112: 110: 69: 45: 37: 21: 2348: 2347: 2343: 2342: 2341: 2339: 2338: 2337: 2313: 2312: 2231: 2226: 2190: 2189: 2185: 2164:(2): 04014048. 2151: 2150: 2146: 2120: 2119: 2115: 2081: 2080: 2076: 2055:(2): 04013046. 2042: 2041: 2037: 2003: 2002: 1998: 1954: 1953: 1949: 1915: 1914: 1910: 1858: 1857: 1853: 1848: 1844: 1839: 1835: 1826: 1822: 1815: 1811: 1806: 1802: 1797: 1793: 1785: 1781: 1776: 1772: 1767: 1763: 1757: 1753: 1748: 1744: 1739: 1735: 1730: 1726: 1719: 1715: 1673: 1672: 1668: 1661: 1657: 1652:Wayback Machine 1643: 1639: 1632: 1628: 1621: 1617: 1610: 1606: 1599: 1595: 1559: 1558: 1554: 1525:Energy Procedia 1518: 1517: 1513: 1477: 1476: 1472: 1465: 1461: 1454: 1450: 1438: 1434: 1423: 1408: 1407: 1403: 1398:Wayback Machine 1389: 1385: 1380:Wayback Machine 1371: 1367: 1360: 1356: 1352: 1272: 1255: 1235:balloon framing 1205: 1180: 1159:Cypress Freeway 1151:Cypress Freeway 1132: 1119: 1079: 1058:Lattice girders 1047: 1027: 1014: 1003: 1001:Bridge retrofit 983:gelatin dessert 962: 953: 940: 928:circuit breaker 893: 854: 829: 792: 769: 738: 725: 684: 654: 617: 593:display windows 569: 563: 558: 541: 520: 511: 506: 497: 488: 468: 456:One Rincon Hill 444: 433: 421:Shock absorbers 412: 380: 374: 365: 344: 299: 250: 158:failure due to 133: 122: 116: 113: 70: 68: 58: 46: 35: 28: 23: 22: 18:Seismic upgrade 15: 12: 11: 5: 2346: 2344: 2336: 2335: 2330: 2325: 2315: 2314: 2311: 2310: 2304: 2298: 2293: 2288: 2279: 2274: 2261: 2255: 2238: 2230: 2229:External links 2227: 2225: 2224: 2183: 2144: 2113: 2094:(3): 308–318. 2074: 2035: 1996: 1947: 1928:(5): 331–342. 1908: 1851: 1842: 1833: 1820: 1809: 1800: 1791: 1779: 1770: 1761: 1751: 1742: 1733: 1724: 1713: 1686:(3): 971–998. 1666: 1655: 1637: 1626: 1615: 1604: 1593: 1552: 1511: 1470: 1459: 1448: 1432: 1429:on 2012-07-26. 1421: 1401: 1383: 1365: 1353: 1351: 1348: 1347: 1346: 1341: 1336: 1331: 1326: 1324:Seismic hazard 1321: 1320: 1319: 1314: 1304: 1298: 1293: 1288: 1283: 1278: 1271: 1268: 1254: 1251: 1243: 1242: 1238: 1231: 1227: 1221: 1204: 1201: 1179: 1176: 1131: 1128: 1118: 1115: 1078: 1075: 1046: 1043: 1026: 1023: 1013: 1010: 1002: 999: 991:Ferry Building 961: 958: 952: 949: 939: 936: 932: 931: 924: 892: 889: 853: 850: 828: 825: 815:, thin layers 791: 788: 768: 765: 737: 734: 724: 721: 683: 680: 653: 650: 616: 613: 565:Main article: 562: 559: 557: 554: 540: 537: 519: 516: 510: 507: 505: 502: 496: 493: 487: 484: 467: 464: 451:Slosh dynamics 443: 440: 432: 429: 411: 408: 403:base isolation 383:Base isolation 378:Base isolation 376:Main article: 373: 372:Base isolators 370: 364: 361: 343: 340: 339: 338: 335: 315: 311: 298: 295: 290: 289: 286: 283: 280: 276: 273:base isolation 271:and/or use of 265: 249: 246: 213:Reinforced by 135: 134: 49: 47: 40: 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 2345: 2334: 2331: 2329: 2326: 2324: 2321: 2320: 2318: 2308: 2305: 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