Integral bridge

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Integral bridge frame.png
Integral bridge embedded.png
Integral bridge end screen.png
Integral bridge bank pad.png
Clockwise from upper left: Examples of frame, embedded, bank pad and end screen bridge types. The latter is semi-integral as it incorporates a bridge bearing.

An integral bridge contains no expansion joints to accommodate enlargement due to increased temperature. Horizontal (axial) movements due to thermal expansion and braking loads are instead transferred to the fill adjacent to the abutment. The omission of the expansion joint removes a pathway for the penetration of chloride-bearing road salts to the bridge's sub-structure. In the United Kingdom there is a presumption that most new short to medium length bridges will be of the integral type.[ citation needed ]

Expansion joint construction detail designed to absorb temperature-induced volume changes of construction parts

An expansion joint or movement joint is an assembly designed to safely absorb the temperature-induced expansion and contraction of construction materials, to absorb vibration, to hold parts together, or to allow movement due to ground settlement or earthquakes. They are commonly found between sections of buildings, bridges, sidewalks, railway tracks, piping systems, ships, and other structures.

Contents

An early example of an integral bridge is masonry arch bridge. Some of the earliest examples of integral bridges in reinforced concrete were constructed as part of the United Kingdom's M1 motorway in 1959. [1]

Arch bridge bridge with abutments at each end shaped as a curved arch

An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side. A viaduct may be made from a series of arches, although other more economical structures are typically used today.

M1 motorway motorway in central England connecting London and Leeds

The M1 motorway connects London to Leeds, where it joins the A1(M) near Aberford, to connect to Newcastle. It was the first inter-urban motorway to be completed in the UK; the first motorway in the country was the Preston By-pass, which later became part of the M6.

Description

Non-integral bridges incorporate at least one expansion joint (pictured) to accommodate movement BridgeExpansionJoint.jpg
Non-integral bridges incorporate at least one expansion joint (pictured) to accommodate movement

An integral bridge contains no expansion joints, spanning monolithically from abutment to abutment. [1] Movement due to thermal expansion and contraction or braking loads is accommodated by the end walls or abutments. [2] [3] Where intermediate supports are specified (e.g. bridge piers) these may also serve to resist thermal expansion movements. [3]

Monolithic architecture

Monolithic architecture describes buildings which are carved, cast or excavated from a single piece of material, historically from rock. The most basic form of monolithic architecture is a rock-cut building, such as the monolithic churches of Ethiopia built by the Zagwe dynasty, or the Pancha Rathas in India. These are cut out of solid rock, to which they remain attached at the base. In most cases this is evident from the remaining surrounding rock, but sometimes a building is cut from an outcrop, as in the Shore Temple in southern India, and only inspection at close quarters reveals that the building is monolithic.

Abutment

In engineering, abutment refers to the substructure at the ends of a bridge span or dam whereon the structure's superstructure rests or contacts. Single-span bridges have abutments at each end which provide vertical and lateral support for the bridge, as well as acting as retaining walls to resist lateral movement of the earthen fill of the bridge approach. Multi-span bridges require piers to support ends of spans unsupported by abutments. Dam abutments are generally either side of a valley or gorge but may be artificial in order to support arch dams such as Kurobe Dam in Japan.

The omission of the expansion joint removes a significant maintenance and durability issue, as it serves as a point of ingress for road salts which allows the abutment, piers and deck soffit concrete to come under chloride attack that can cause degradation and eventual span failure. A 1989 British study showed that the majority of expansion joints surveyed in existing bridges had failed and allowed water (and hence salt) ingress. [1]

The movement experienced at the abutment in an integral bridge is an order of magnitude greater than those designed with movement joints. The size of movement depends on the stiffness of the bridge structure and the fill adjacent to the abutment (which is subject to compaction). The movement is largest in the upper portion of the abutment, where thermal effects are greatest. [2] Highways England specify that integral bridges should be designed to limit movement to 20 millimetres (0.79 in). [3] Due to repeated expansion and contraction cycles the backfill adjacent to the abutment is subject to ratcheting, whereby the material's stiffness is increased. The maximum stiffness level is reached after around 100–200 thermal expansion cycles. [2]

Highways England Company Limited is the government-owned company charged with operating, maintaining and improving England's motorways and major A roads. It operates information services through the provision of on-road signage and its Traffic England website, provides traffic officers to deal with incidents on its network, and manages the delivery of improvement schemes to the network.

Types

Highways England recognises four types of integral bridge, defined by the construction of their abutments:

Where bridge bearings are used on an integral bridge (as is often the case for end screen abutment types) the structure is sometimes referred to as semi-integral. [1]

Use

It is widely accepted that short to medium length bridges should be designed as integral structures to minimise maintenance requirements. [2] Highways England's Design Manual for Roads and Bridges (applicable to the whole of the UK and many parts of it, including the section on integral bridges, applying to the Republic of Ireland) states that all bridges with deck length less than 60 metres (200 ft) and skew of less than 30 degrees should be designed as integral structures unless there is a compelling reason to do otherwise. [1] [3] [4]

Related Research Articles

Prestressed concrete form of concrete used in construction

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A slip joint is a mechanical construction allowing extension and compression in a linear structure.

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Plate girder bridge

A plate girder bridge is a bridge supported by two or more plate girders.

Steel frame

Steel frame is a building technique with a "skeleton frame" of vertical steel columns and horizontal I-beams, constructed in a rectangular grid to support the floors, roof and walls of a building which are all attached to the frame. The development of this technique made the construction of the skyscraper possible.

Extradosed bridge a structure that combines the main elements of both a prestressed box girder bridge and a cable-stayed bridge

An extradosed bridge employs a structure that combines the main elements of both a prestressed box girder bridge and a cable-stayed bridge. The name comes from the word extrados, the exterior or upper curve of an arch, and refers to how the "stay cables" on an extradosed bridge are not considered as such in the design, but are instead treated as external prestressing tendons deviating upward from the deck. In this concept, they remain part of the main bridge superstructure.

Tied-arch bridge type of bridge

A tied-arch bridge is an arch bridge in which the outward-directed horizontal forces of the arch(es) are borne as tension by a chord tying the arch ends, rather than by the ground or the bridge foundations. This strengthened chord may be the deck structure itself or consist of separate, deck-independent tie-rods.

Girder bridge bridge built of girders placed on bridge abutments and foundation piers

A girder bridge is a bridge that uses girders as the means of supporting its deck. The two most common types of modern steel girder bridge are plate and box.

Schierstein Bridge

The Schierstein Bridge is 1,282-meter (4,206 ft) long, four-lane highway bridge in Germany. It carries Bundesautobahn 643 over the Rhine River between Mainz-Mombach, Rhineland-Palatinate and Wiesbaden-Schierstein, Hesse. Crossing two arms of the Rhine and the intervening island of Rettbergsaue, the bridge is made of six individual structures, including 100 m (330 ft) from prestressed concrete. It was built between 1959 and 1962.

Hadley Parabolic Bridge

The Hadley Parabolic Bridge, often referred to locally as the Hadley Bow Bridge, carries Corinth Road across the Sacandaga River in Hadley, New York, United States. It is an iron bridge dating from the late 19th century.

A pipe support or pipe hanger is a designed element that transfer the load from a pipe to the supporting structures. The load includes the weight of the pipe proper, the content that the pipe carries, all the pipe fittings attached to pipe, and the pipe covering such as insulation. The four main functions of a pipe support are to anchor, guide, absorb shock, and support a specified load. Pipe supports used in high or low temperature applications may contain insulation materials. The overall design configuration of a pipe support assembly is dependent on the loading and operating conditions.

Vidyasagar Setu cable-stayed bridge

Vidyasagar Setu, also known as the Second Hooghly Bridge, is a toll bridge over the Hooghly River in West Bengal, India, linking the cities of Kolkata and Howrah.

Aircraft bridges, including taxiway bridges and runway bridges, bring aircraft traffic over motorways, railways, and waterways, and must be designed to support the heaviest aircraft that may cross them. In 1963, a taxiway bridge at Chicago O'Hare Airport, one of the busiest airports in the world, was planned to handle future aircraft weighing 365,000 pounds (166,000 kg), but aircraft weights doubled within two years of its construction. Currently, the largest passenger aircraft in the world, the Airbus A380, has a maximum take-off weight (MTOW) of 575 t (1,268,000 lb). The largest Boeing planes, i.e. the current "Project Ozark" versions of the Boeing 747-8, are approaching MTOW of greater than 1,000,000 lb (450,000 kg). Aircraft bridges must be designed for the substantial forces exerted by aircraft braking, affecting the lateral load in substructure design. Braking force of 70 percent of the live load is assumed in two recent taxiway bridge designs. And "deck design is more apt to be controlled by punching shear than flexure due to the heavy wheel loads."

Clackline Bridge road bridge in Clackline, Western Australia

Clackline Bridge is a road bridge in Clackline, Western Australia, 77 kilometres (48 mi) east of Perth in the Shire of Northam, that carried the Great Eastern Highway until 2008. It is the only bridge in Western Australia to have spanned both a waterway and railway, the Clackline Brook and the former Eastern Railway alignment. The mainly timber bridge has a unique curved and sloped design, due to the difficult topography and the route of the former railway. The bridge was designed in 1934 to replace two dangerous rail crossings and a rudimentary water crossing. Construction began in January 1935, and was completed relatively quickly, with the opening ceremony held in August 1935. The bridge has undergone various improvement and maintenance works since then, including widening by three metres (10 ft) in 1959–60, but remained a safety hazard, with increasing severity and numbers of accidents through the 1970s and 1980s. Planning for a highway bypass of Clackline and the Clackline Bridge began in the 1990s, and it was constructed between January 2007 and February 2008. The local community had been concerned that the historic bridge would be lost, but it remains in use as part of the local road network, and has been listed on both the Northam Municipal Heritage Inventory and the Heritage Council of Western Australia's Register of Heritage Places.

Rigid-frame bridge type of bridge

A Rigid-frame bridge is a bridge in which the superstructure and substructure are rigidly connected to act as a continuous unit. Typically, the structure is cast monolithically, making the structure continuous from deck to foundation. The connections between members are rigid connections which transfer bending moment, axial forces, and shear forces. A bridge design consisting of a rigid frame can provide significant structural benefits, but can also be difficult to design and/or construct.

Nipigon River Bridge road bridge over the Nipigon River

The Nipigon River Bridge is a cable-stayed bridge carrying Highway 11 and Highway 17, designated as part of the Trans-Canada Highway, across the Nipigon River near Nipigon, Ontario, Canada.

Yowaka River bridge, Greigs Flat

The Yowaka River bridge is an heritage-listed road bridge that carries the Princes Highway across the Yowaka River at Greigs Flat on the Bega Valley Shire local government area of New South Wales, Australia. It was built in 1936. The bridge is also known as the Yowaka Bridge near Eden. The property is owned by Roads and Maritime Services, an agency of the Government of New South Wales. It was added to the New South Wales State Heritage Register on 20 June 2000.

Structural support is a part of a building or structure providing the necessary stiffness and strength in order to resist the internal forces and guide them safely to the ground. External loads that act on buildings cause internal forces in building support structures. Supports can be either at the end or at any intermediate point along a structural member or a constituent part of a building and they are referred to as connections, joints or restraints.

References

  1. 1 2 3 4 5 "Integral bridges". The Concrete Society. Retrieved 12 February 2018.
  2. 1 2 3 4 Rhodes, Steve. "Integral Bridges and the Modelling of Soil-Structure Interaction" (PDF). LUSAS. Retrieved 12 February 2018.
  3. 1 2 3 4 5 6 7 8 "BA 42/96 Amendment no 1: The Design of Integral Bridges" (PDF). Design Manual for Roads and Bridges. Highways England. Retrieved 12 February 2018.
  4. ↑ "NRA addendum to BA 42/96 amendment no. 1 the design of integral bridges" (PDF). Transport Infrastructure Ireland. National Roads Authority. Retrieved 14 February 2018.
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