Misplaced Pages

#775224

64-657: The barriers are also known as a K-rail , a term stipulated in the California Department of Transportation specification for temporary concrete traffic barriers which first started using concrete median barriers in the mid-1940s. Over time, different variants were created. Taller variants, such as the Ontario Tall Wall , proved more effective at stopping vehicles and had the added advantage of blocking most oncoming headlights. More modular variants, including plastic water-filled barriers, have been created. Although it

128-504: A chicane to slow vehicular traffic arriving at military installations or other secure areas. During the US occupation of Iraq jersey barriers were set up in cities as form of urban warfare to combat Iraqi resistance . The Ohio Department of Transportation mandates specific design requirements for their precast concrete barrier walls. The department has marked all compliant precast concrete barrier walls with "350", indicating that they adhere to

192-552: A Task Force Committee on Transportation to study the state transportation system and recommend major reforms. One of the proposals of the task force was the creation of a State Transportation Board as a permanent advisory board on state transportation policy; the board would later merge into the California Transportation Commission in 1978. In September 1971, the State Transportation Board proposed

256-485: A concrete structural member reinforced with steel will experience minimal differential stress as the temperature changes. Other readily available types of rebar are manufactured of stainless steel , and composite bars made of glass fiber , carbon fiber , or basalt fiber . The carbon steel reinforcing bars may also be coated in zinc or an epoxy resin designed to resist the effects of corrosion, especially when used in saltwater environments. Bamboo has been shown to be

320-532: A device to reinforce arches, vaults , and cupolas . 2,500 meters of rebar was used in the 14th-century Château de Vincennes . During the 18th century, rebar was used to form the carcass of the Leaning Tower of Nevyansk in Russia, built on the orders of the industrialist Akinfiy Demidov . The cast iron used for the rebar was of high quality, and there is no corrosion on the bars to this day. The carcass of

384-671: A generic, portable barrier during construction projects and temporary rerouting of traffic into stopgap carpool and rush-hour reversing highway lanes. Most of the original barriers constructed in New Jersey in the 1950s and early 1960s were not "modular"; they were formed from concrete poured in place. Many of the first installations (Route 46 in Bergen County and Passaic County, for instance) were about two feet (61 cm) tall, much shorter than modern heights. Some dividers on county or local roads may have been lower than that, since they replaced

448-426: A highway. A typical Jersey barrier stands 32 inches (81 cm) tall and is made of steel-reinforced poured concrete or plastic. Many are constructed with the embedded steel reinforcement protruding from each end, allowing them to be incorporated into permanent emplacements when linked to one another by sections of fresh concrete poured on-site. Their widespread use in road construction has led to wide application as

512-499: A limited ability to carry tensile loads. When rebar is added they are known as "reinforced masonry". A similar approach (of embedding rebar vertically in designed voids in engineered blocks) is also used in dry-laid landscape walls, at least pinning the lowest course in place into the earth, also employed securing the lowest course and/or deadmen in walls made of engineered concrete or wooden landscape ties. In unusual cases, steel reinforcement may be embedded and partially exposed, as in

576-513: A new mission statement: "Provide a safe, sustainable, integrated and efficient transportation system to enhance California's economy and livability." The earliest predecessor of Caltrans was the Bureau of Highways, which was created by the California Legislature and signed into law by Governor James Budd in 1895. This agency consisted of three commissioners who were charged with analyzing

640-516: A raised concrete rumble strip that would dissuade, but not prevent, traffic crossing from one lane to another. Route 46 had a rumble strip in many places before the higher barrier was gradually installed. These lower dividers are visible in old photographs. When the Bergen Mall was first opened in Paramus, New Jersey , rumble strip dividers were extensively used on the roadway (Forest Avenue) that separated

704-553: A viable alternative to reinforcing steel in concrete construction. These alternative types tend to be more expensive or may have lesser mechanical properties and are thus more often used in specialty construction where their physical characteristics fulfill a specific performance requirement that carbon steel does not provide. Reinforcing bars in masonry construction have been used since antiquity , with Rome using iron or wooden rods in arch construction. Iron tie rods and anchor plates were later employed across Medieval Europe, as

SECTION 10

#1732844947776

768-424: Is also used in high-corrosion environments. It is available in many forms, such as spirals for reinforcing columns, common rods, and meshes. Most commercially available rebar is made from unidirectional fibers set in a thermoset polymer resin and is often referred to as FRP. Some special construction such as research and manufacturing facilities with very sensitive electronics may require the use of reinforcement that

832-424: Is approximated as (bar size/9)² square inches. For example, the area of #8 bar is (8/9)² = 0.79 square inches. Bar sizes larger than #8 follow the 1 ⁄ 8 -inch rule imperfectly and skip sizes #12–13, and #15–17 due to historical convention. In early concrete construction bars of one inch and larger were only available in square sections, and when large format deformed round bars became available around 1957,

896-525: Is cast into it to carry the tensile loads . Most steel reinforcement is divided into primary and secondary reinforcement: Secondary applications include rebar embedded in masonry walls, which includes both bars placed horizontally in a mortar joint (every fourth or fifth course of block) or vertically (in the horizontal voids of cement blocks and cored bricks, which is then fixed in place with grout . Masonry structures held together with grout have similar properties to concrete – high compressive resistance but

960-445: Is covered by District 3. Rebar Rebar (short for reinforcing bar ), known when massed as reinforcing steel or steel reinforcement , is a tension device added to concrete to form reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression , but has low tensile strength . Rebar usually consists of steel bars which significantly increase

1024-522: Is non-conductive to electricity, and medical imaging equipment rooms may require non-magnetic properties to avoid interference. FRP rebar, notably glass fibre types have low electrical conductivity and are non-magnetic which is commonly used for such needs. Stainless steel rebar with low magnetic permeability is available and is sometimes used to avoid magnetic interference issues. Reinforcing steel can also be displaced by impacts such as earthquakes , resulting in structural failure. The prime example of this

1088-526: Is not clear exactly when or where the first concrete median barriers were used, concrete median barriers were used in the mid-1940s on U.S. Route 99 on the descent from the Tehachapi Mountains in the Central Valley south of Bakersfield, California . This first generation of concrete barriers was developed to (a) minimize the number of out-of-control trucks penetrating the barrier, and (b) eliminate

1152-759: Is subject to the requirements of Australian Standards AS3600 (Concrete Structures) and AS/NZS4671 (Steel Reinforcing for Concrete). There are other standards that apply to testing, welding and galvanizing. The designation of reinforcement is defined in AS/NZS4671 using the following formats: Shape/ Section D- deformed ribbed bar, R- round / plain bar, I- deformed indented bar Ductility Class L- low ductility, N- normal ductility, E- seismic (Earthquake) ductility Standard grades (MPa) 250N, 300E, 500L, 500N, 500E Bars are typically abbreviated to simply 'N' (hot-rolled deformed bar), 'R' (hot-rolled round bar), 'RW' (cold-drawn ribbed wire) or 'W' (cold-drawn round wire), as

1216-703: Is the collapse of the Cypress Street Viaduct in Oakland, California as a result of the 1989 Loma Prieta earthquake , causing 42 fatalities. The shaking of the earthquake caused rebars to burst from the concrete and buckle . Updated building designs, including more circumferential rebar, can address this type of failure. US/Imperial bar sizes give the diameter in units of 1 ⁄ 8 inch (3.2 mm) for bar sizes #2 through #8, so that #8 = 8 ⁄ 8 inch = 1-inch (25 mm) diameter. There are no fractional bar sizes in this system. The "#" symbol indicates

1280-652: The Federal-Aid Highway Act of 1956 for the construction of its portion of the Interstate Highway System . Over the next two decades after Collier-Burns, the state "embarked on a massive highway construction program" in which nearly all of the now-extant state highway system was either constructed or upgraded. In hindsight, the period from 1940 to 1969 can be characterized as the "Golden Age" of California's state highway construction program. The history of Caltrans and its predecessor agencies during

1344-745: The National Environmental Policy Act and the California Environmental Quality Act forced Caltrans to devote significant time, money, people, and other resources to confronting issues such as "air and water quality, hazardous waste, archaeology, historic preservation, and noise abatement." The devastating 1971 San Fernando earthquake compelled the agency to recognize that its existing design standards had not adequately accounted for earthquake stress and that numerous existing structures needed expensive seismic retrofitting . Maintenance and construction costs grew at twice

SECTION 20

#1732844947776

1408-404: The number sign , and thus "#6" is read as "number six". The use of the "#" sign is customary for US sizes, but "No." is sometimes used instead. Within the trades rebar is known by a shorthand utilizing the bar diameter as descriptor, such as "four-bar" for bar that is four-eighths (or one-half) of an inch. The cross-sectional area of a bar, as given by πr ², works out to (bar size/9.027)², which

1472-403: The 1970s, as its institutional focus shifted from highway construction to highway maintenance. The agency was forced to contend with declining revenues, increasing construction and maintenance costs (especially the skyrocketing cost of maintaining the vast highway system built over the past three prior decades), widespread freeway revolts , and new environmental laws . In 1970, the enactment of

1536-635: The 20th century was marked by many firsts. It was one of the first agencies in the United States to paint centerlines on highways statewide; the first to build a freeway west of the Mississippi River ; the first to build a four-level stack interchange ; the first to develop and deploy non-reflective raised pavement markers, better known as Botts' dots ; and one of the first to implement dedicated freeway-to-freeway connector ramps for high-occupancy vehicle lanes . In 1967, Governor Ronald Reagan formed

1600-552: The City of Toronto is doing likewise on portions of the Gardiner Expressway and Don Valley Parkway . Hollow polyethylene barriers have been developed for short-term applications where portability is important. These plastic barriers are normally filled with water after placement on-site to provide a moderate level of crash protection, then emptied prior to removal. They are not designed to deflect vehicles, so vehicles may penetrate

1664-607: The Department of Engineering into the Department of Public Works, which continued to have a Division of Highways. That same year, three additional divisions (now districts) were created, in Stockton, Bishop, and San Bernardino. In 1933, the state legislature enacted an amendment to the State Highway Classification Act of 1927, which added over 6,700 miles of county roads to the state highway system. To help manage all

1728-441: The Department of Transportation, of which the most important was the Department of Public Works and its Division of Highways. The California Department of Transportation began official operations on July 1, 1973. The new agency was organized into six divisions: Highways, Mass Transportation, Aeronautics, Transportation Planning, Legal, and Administrative Services. Caltrans went through a difficult period of transformation during

1792-502: The State of California into 12 districts, supervised by district offices. Most districts cover multiple counties ; District 12 ( Orange County ) is the only district with one county. The largest districts by population are District 4 ( San Francisco Bay Area ) and District 7 ( Los Angeles and Ventura counties). Like many state agencies, Caltrans maintains its headquarters in Sacramento , which

1856-524: The United States, made a significant contribution to the development of reinforcing bars in concrete construction. He invented twisted iron rebar, which he initially thought of while designing self-supporting sidewalks for the Masonic Hall in Stockton, California. His twisted rebar was, however, not initially appreciated and even ridiculed at the Technical Society of California, where members stated that

1920-413: The United States, who produced and tested reinforced concrete beams. Joseph Monier of France is one of the most notable figures for the invention and popularization of reinforced concrete. As a French gardener, Monier patented reinforced concrete flowerpots in 1867, before proceeding to build reinforced concrete water tanks and bridges. Ernest L. Ransome , an English engineer and architect who worked in

1984-755: The additional work created by this massive expansion, an eleventh district office was founded that year in San Diego. The enactment of the Collier–Burns Highway Act of 1947 after "a lengthy and bitter legislative battle" was a watershed moment in Caltrans history. The act "placed California highway's program on a sound financial basis" by doubling vehicle registration fees and raising gasoline and diesel fuel taxes from 3 cents to 4.5 cents per gallon. All these taxes were again raised further in 1953 and 1963. The state also obtained extensive federal funding from

Jersey barrier - Misplaced Pages Continue

2048-486: The bar into place, while the second makes use of the high compressive strength of concrete. Common rebar is made of unfinished tempered steel, making it susceptible to rusting . Normally the concrete cover is able to provide a pH value higher than 12 avoiding the corrosion reaction. Too little concrete cover can compromise this guard through carbonation from the surface, and salt penetration . Too much concrete cover can cause bigger crack widths which also compromises

2112-430: The barriers. These barriers can also be filled with sand at the cost of reduced portability. California Department of Transportation The California Department of Transportation ( Caltrans ) is an executive department of the U.S. state of California . The department is part of the cabinet -level California State Transportation Agency (CalSTA). Caltrans is headquartered in Sacramento . Caltrans manages

2176-529: The bars and corrosion under the epoxy film have been reported. These epoxy-coated bars are used in over 70,000 bridge decks in the US, but this technology was slowly being phased out in favor of stainless steel rebar as of 2005 because of its poor performance. Requirements for deformations are found in US-standard product specifications for steel bar reinforcing, such as ASTM A615 and ASTM A706, and dictate lug spacing and height. Fibre-reinforced plastic rebar

2240-673: The beams at the columns. This type of failure manifested in the partial collapse of the Bixby Hotel in Long Beach, California and total collapse of the Eastman Kodak Building in Rochester, New York, both during construction in 1906. It was, however, concluded that both failures were the consequences of poor-quality labor. With the increase in demand of construction standardization, innovative reinforcing systems such as Kahn's were pushed to

2304-448: The commissioners submitted their report to the governor on November 25, 1896, the legislature replaced the Bureau with the Department of Highways. Due to the state's weak fiscal condition and corrupt politics, little progress was made until 1907, when the legislature replaced the Department of Highways with the Department of Engineering, within which there was a Division of Highways. California voters approved an $ 18 million bond issue for

2368-406: The concrete, it can still be pulled out of the concrete under high stresses, an occurrence that often accompanies a larger-scale collapse of the structure. To prevent such a failure, rebar is either deeply embedded into adjacent structural members (40–60 times the diameter), or bent and hooked at the ends to lock it around the concrete and other rebar. This first approach increases the friction locking

2432-481: The construction of a state highway system in 1910, and the first California Highway Commission was convened in 1911. On August 7, 1912, the department broke ground on its first construction project, the section of El Camino Real between South San Francisco and Burlingame , which later became part of California State Route 82 . The year 1912 also saw the founding of the Transportation Laboratory and

2496-464: The creation of a state department of transportation charged with responsibility "for performing and integrating transportation planning for all modes ." Governor Reagan mentioned this proposal in his 1972 State of the State address , and Assemblyman Wadie P. Deddeh introduced Assembly Bill 69 to that effect, which was duly passed by the state legislature and signed into law by Reagan later that same year. AB 69 merged three existing departments to create

2560-476: The creation of seven administrative divisions, which are the predecessors of the 12 district offices in use as of 2018 . The original seven division headquarters were located in: In 1913, the California State Legislature began requiring vehicle registration and allocated the resulting funds to support regular highway maintenance, which began the next year. In 1921, the state legislature turned

2624-483: The grocery stores from the mall proper. The design of the Jersey barrier was specifically intended to minimize damage in incidental accidents and reduce the likelihood of a car crossing into oncoming lanes in the event of a collision . In common shallow-angle hits, sheet-metal damage is minimized by allowing the vehicle tires to ride up on the lower sloped face. Head-on vehicle collisions are minimized by gradually lifting

Jersey barrier - Misplaced Pages Continue

2688-405: The idea that Kahn's reinforcing system in concrete beams would act as a Warren truss and also noted that this system would not provide the adequate amount of shear stress reinforcement at the ends of the simply supported beams, the place where the shear stress is greatest. Furthermore, Turner warned that Kahn's system could result in a brittle failure as it did not have longitudinal reinforcement in

2752-929: The industry manufactured them to provide the cross-sectional area equivalent of standard square bar sizes that were formerly used. The diameter of the equivalent large format round shape is rounded to the nearest 1 ⁄ 8 inch to provide the bar size. For example, #9 bar has a cross section of 1.00 square inch (6.5 cm ), and therefore a diameter of 1.128 inches (28.7 mm). #10, #11, #14, and #18 sizes correspond to 1 1 ⁄ 8 inch, 1 1 ⁄ 4 , 1 1 ⁄ 2 , and 2-inch square bars, respectively. Sizes smaller than #3 are no longer recognized as standard sizes. These are most commonly manufactured as plain round undeformed rod steel but can be made with deformations. Sizes smaller than #3 are typically referred to as "wire" products and not "bar" and specified by either their nominal diameter or wire gage number. #2 bars are often informally called "pencil rod" as they are about

2816-481: The inflation rate in this era of high inflation; the reluctance of one governor after another to raise fuel taxes in accordance with inflation meant that California ranked dead last in the United States in per capita transportation spending by 1983. During the 1980s and 1990s, Caltrans concentrated on "the upgrading, rehabilitation, and maintenance of the existing system," plus occasional gap closure and realignment projects. For administrative purposes, Caltrans divides

2880-682: The local guard. As rust takes up greater volume than the steel from which it was formed, it causes severe internal pressure on the surrounding concrete, leading to cracking, spalling , and, ultimately, structural failure . This phenomenon is known as oxide jacking . This is a particular problem where the concrete is exposed to salt water, as in bridges where salt is applied to roadways in winter, or in marine applications. Uncoated, corrosion-resistant low- carbon / chromium (microcomposite), silicon bronze , epoxy -coated, galvanized , or stainless steel rebars may be employed in these situations at greater initial expense, but significantly lower expense over

2944-522: The need for costly and dangerous median barrier maintenance in high-accident locations with narrow medians – concerns that are as valid today as they were 80 years ago. The Jersey barrier, also called New Jersey wall, was developed in the 1950s (introduced in current form in 1959), at Stevens Institute of Technology , New Jersey , United States, under the direction of the New Jersey State Highway Department to divide multiple lanes on

3008-446: The nominal bar diameter in millimeters, as an "alternate size" specification. Substituting a true metric size for a US/Imperial size is called a hard conversion , and sometimes results in the use of a physically different sized bar. bar size size (soft) Metric bar designations represent the nominal bar diameter in millimeters, rounded to the nearest 5 mm. bar size (kg/m) (mm) Area (mm ) Metric bar designations represent

3072-508: The nominal bar diameter in millimetres. Preferred bar sizes in Europe are specified to comply with Table 6 of the standard EN 10080 , although various national standards still remain in force (e.g. BS 4449 in the United Kingdom). In Switzerland some sizes are different from European standard. bar size density (kg/m) diameter (mm) area (mm ) Reinforcement for use in concrete construction

3136-510: The qualification of “tentative” was removed when the updated standard ASTM A305-49 was issued in 1949. The requirements for deformations found in current specifications for steel bar reinforcing, such as ASTM A615 and ASTM A706, among others, are the same as those specified in ASTM A305-49. Concrete is a material that is very strong in compression , but relatively weak in tension . To compensate for this imbalance in concrete's behavior, rebar

3200-625: The requirements laid out in the National Cooperative Highway Research Program's Report 350. Without this marking, a barrier wall is not approved for use in Ohio. Modern variations include the constant-slope barrier and the F-shape barrier . The F-shape is generally similar to the Jersey barrier in appearance, but is taller, with somewhat different angles. The UK equivalent is the concrete step barrier . First tested in 1968 by

3264-411: The roads of the state and making recommendations for their improvement. At the time, there was no state highway system, since roads were purely a local responsibility. California's roads consisted of crude dirt roads maintained by county governments, as well as some paved streets in certain cities, and this ad hoc system was no longer adequate for the needs of the state's rapidly growing population. After

SECTION 50

#1732844947776

3328-491: The same size as a pencil. When US/Imperial sized rebar are used in projects with metric units, the equivalent metric size is typically specified as the nominal diameter rounded to the nearest millimeter. These are not considered standard metric sizes, and thus is often referred to as a soft conversion or the "soft metric" size. The US/Imperial bar size system recognizes the use of true metric bar sizes (No. 10, 12, 16, 20, 25, 28, 32, 36, 40, 50 and 60 specifically) which indicates

3392-413: The service life of the project. Extra care is taken during the transport, fabrication, handling, installation, and concrete placement process when working with epoxy-coated rebar, because damage will reduce the long-term corrosion resistance of these bars. Even damaged epoxy-coated bars have shown better performance than uncoated reinforcing bars, though issues from debonding of the epoxy coating from

3456-519: The side in favor of the concrete reinforcing systems seen today. Requirements for deformations on steel bar reinforcement were not standardized in US construction until about 1950. Modern requirements for deformations were established in "Tentative Specifications for the Deformations of Deformed Steel Bars for Concrete Reinforcement", ASTM A305-47T. Subsequently, changes were made that increased rib height and reduced rib spacing for certain bar sizes, and

3520-459: The state's highway system , which includes the California Freeway and Expressway System , supports public transportation systems throughout the state and provides funding and oversight for three state-supported Amtrak intercity rail routes ( Capitol Corridor , Pacific Surfliner and San Joaquins ) which are collectively branded as Amtrak California . In 2015, Caltrans released

3584-533: The steel tie bars that constrain and reinforce the masonry of Nevyansk Tower or ancient structures in Rome and the Vatican. Steel has a thermal expansion coefficient nearly equal to that of modern concrete . If this were not so, it would cause problems through additional longitudinal and perpendicular stresses at temperatures different from the temperature of the setting. Although rebar has ribs that bind it mechanically to

3648-481: The taller barrier for their roads, as compared to the standard 32 inches (81 cm) suggested by the Federal Highway Administration . Designs with two rectangular notches at the bottom (through the short axis) allow for forklift-style lifting by front-end loaders . Barriers meant for short-term placement, especially in military and security barrier uses, might include steel rebar loops embedded in

3712-410: The tensile strength of the structure. Rebar surfaces feature a continuous series of ribs, lugs or indentations to promote a better bond with the concrete and reduce the risk of slippage. The most common type of rebar is carbon steel , typically consisting of hot-rolled round bars with deformation patterns embossed into its surface. Steel and concrete have similar coefficients of thermal expansion , so

3776-457: The then Department of Highways in Ontario, Canada , the Ontario Tall Wall is a variant of the Jersey barrier. Standing at 42 inches (107 cm), it is 10 inches (25 cm) taller than the standard Jersey barrier. Ontario's Ministry of Transportation has been replacing guiderails (steel guardrail and steel box-beam) with these tall wall barriers on 400-series highways since the early 1990s, while

3840-650: The top surface for rapid hook-and-cable system lifting. The 2010 G-20 Toronto summit used modified modular Jersey barriers with wired fencing bolted onto the concrete. The fence used the barrier as sturdy base to prevent protesters from toppling the fence around the security zone at the Metro Toronto Convention Centre . The U.S. military nicknamed the devices "Qaddafi Blocks" after truck bomb attacks in Beirut in 1983 resulted in more widespread use in military installations. Sometimes they are deployed to form

3904-548: The tower was connected to its cast iron tented roof , crowned with one of the first known lightning rods . However, not until the mid-19th century, with the embedding of steel bars into concrete (thus producing modern reinforced concrete ), did rebar display its greatest strengths. Several people in Europe and North America developed reinforced concrete in the 1850s. These include Joseph-Louis Lambot of France, who built reinforced concrete boats in Paris (1854) and Thaddeus Hyatt of

SECTION 60

#1732844947776

3968-649: The twisting would weaken the iron. In 1889, Ransome worked on the West Coast mainly designing bridges. One of these, the Alvord Lake Bridge in San Francisco's Golden Gate Park, was the first reinforced concrete bridge built in the United States. He used twisted rebar in this structure. At the same time Ransome was inventing twisted steel rebar, C.A.P. Turner was designing his "mushroom system" of reinforced concrete floor slabs with smooth round rods and Julius Kahn

4032-436: The vehicle and pivoting it away from oncoming vehicles and back into traffic heading in its original direction. The New Jersey Turnpike Authority developed and tested a similar, but heavily reinforced, design. This barrier design has been credited with effectively containing and redirecting larger vehicles, including semi-trailer (tractor-trailer) trucks. The states of New York , Massachusetts and New Jersey have adopted

4096-560: Was experimenting with an innovative rolled diamond-shaped rebar with flat-plate flanges angled upwards at 45° (patented in 1902). Kahn predicted concrete beams with this reinforcing system would bend like a Warren truss , and also thought of this rebar as shear reinforcement. Kahn's reinforcing system was built in concrete beams, joists, and columns. The system was both praised and criticized by Kahn's engineering contemporaries: Turner voiced strong objections to this system as it could cause catastrophic failure to concrete structures. He rejected

#775224