Bridge maintenance

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Villagers repairing the bridge in Buangam Buangam villagers are repairing the bridge on the main road of village entrance.png
Villagers repairing the bridge in Buangam

Maintenance of bridge infrastructure presents many challenges. [1] Transportation engineering and maintenance personnel must maintain around the clock service to millions of people each year while maintaining millions of cubic meters of concrete distributed throughout their facilities. This infrastructure includes bridges. Presently only a limited number of accurate and economical techniques exist to test these structures for integrity and safety as well as insure that they meet original design specifications. [2]

Contents

No single technology can locate all physical anomalies in and below the concrete, these techniques along with data fusion can assist in the following investigations, to name a few:

  1. Locating voids and delaminations in bridge pavements and scour around bridge support columns.
  2. Determining location and types of reinforcing steel in concrete
  3. Ensuring quality control on new concrete installations

Techniques

Infrared thermography and ground-penetrating radar

Infrared thermography and ground-penetrating radar have been developed to locate voids and delaminations in concrete structures such as bridge decks, highways and airport pavements. Being able to locate voids and delaminations means the structural maintenance engineer can measure the actual cracking and weakening of concrete pavements before catastrophic failures can occur. [3]

Concrete objects, such as bridges, emit energy based upon the absolute temperature of its surfaces and the surface temperatures are dependent upon the internal conditions of the concrete. These internal conditions can include physical conditions like:

  1. Density changes in concrete
  2. Voids caused by erosion beneath the concrete slabs
  3. Horizontal delaminations caused by rust expansion of rusting internal reinforcing steel.

Infrared thermographic radiometer or “IR Imager” locates these anomalous thermal conditions. This device can measure hundreds of thousand of individual temperature points per second and convert this data to thermal maps or temperature images of the concrete. By locating anomalous areas, or temperature patterns which differ from the background “norm” on these images, trained engineers can locate the exact anomalous areas that could lead to catastrophic failure of concrete and its supporting soil and backfill systems.

Ground-penetrating radar gives information valuable in determining such characteristics as: target material, voids, fluids, soil or backfill strata, and quantity of reinforcing steel present.

Magnetometer

Magnetometers are instruments designed to locate ferrous materials. It can detect iron containing materials to a maximum depth of approximately 10 feet. This is useful for locating dowel pins or determining if reinforcing steel exists.

Pachometer

This device is designed to specifically locate reinforcing steel in concrete and to assist in the determination of the size of the hidden reinforcing steel.

Related Research Articles

<span class="mw-page-title-main">Concrete</span> Composite construction material

Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined.

<span class="mw-page-title-main">Road</span> Land route for travel by vehicles

A road is a thoroughfare for the conveyance of traffic that mostly has an improved surface for use by vehicles and pedestrians. Unlike streets, whose primary function is to serve as public spaces, the main function of roads is transportation.

<span class="mw-page-title-main">Highway engineering</span> Civil engineering of roads, bridges, and tunnels

Highway engineering is a professional engineering discipline branching from the civil engineering subdiscipline of transportation engineering that involves the planning, design, construction, operation, and maintenance of roads, highways, streets, bridges, and tunnels to ensure safe and effective transportation of people and goods. Highway engineering became prominent towards the latter half of the 20th century after World War II. Standards of highway engineering are continuously being improved. Highway engineers must take into account future traffic flows, design of highway intersections/interchanges, geometric alignment and design, highway pavement materials and design, structural design of pavement thickness, and pavement maintenance.

<span class="mw-page-title-main">Road surface</span> Road covered with durable surface material

A road surface or pavement is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past, gravel road surfaces, macadam, hoggin, cobblestone and granite setts were extensively used, but these have mostly been replaced by asphalt or concrete laid on a compacted base course. Asphalt mixtures have been used in pavement construction since the beginning of the 20th century and are of two types: metalled (hard-surfaced) and unmetalled roads. Metalled roadways are made to sustain vehicular load and so are usually made on frequently used roads. Unmetalled roads, also known as gravel roads or dirt roads, are rough and can sustain less weight. Road surfaces are frequently marked to guide traffic.

<span class="mw-page-title-main">Thermographic camera</span> Imaging device using infrared radiation

A thermographic camera is a device that creates an image using infrared (IR) radiation, similar to a normal camera that forms an image using visible light. Instead of the 400–700 nanometre (nm) range of the visible light camera, infrared cameras are sensitive to wavelengths from about 1,000 nm to about 14,000 nm (14 μm). The practice of capturing and analyzing the data they provide is called thermography.

<span class="mw-page-title-main">Thermography</span> Infrared imaging used to reveal temperature

Infrared thermography (IRT), thermal video and/or thermal imaging, is a process where a thermal camera captures and creates an image of an object by using infrared radiation emitted from the object in a process, which are examples of infrared imaging science. Thermographic cameras usually detect radiation in the long-infrared range of the electromagnetic spectrum and produce images of that radiation, called thermograms. Since infrared radiation is emitted by all objects with a temperature above absolute zero according to the black body radiation law, thermography makes it possible to see one's environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature; therefore, thermography allows one to see variations in temperature. When viewed through a thermal imaging camera, warm objects stand out well against cooler backgrounds; humans and other warm-blooded animals become easily visible against the environment, day or night. As a result, thermography is particularly useful to the military and other users of surveillance cameras.

<span class="mw-page-title-main">Permeable paving</span> Roads built with water-pervious materials

Permeable paving surfaces are made of either a porous material that enables stormwater to flow through it or nonporous blocks spaced so that water can flow between the gaps. Permeable paving can also include a variety of surfacing techniques for roads, parking lots, and pedestrian walkways. Permeable pavement surfaces may be composed of; pervious concrete, porous asphalt, paving stones, or interlocking pavers. Unlike traditional impervious paving materials such as concrete and asphalt, permeable paving systems allow stormwater to percolate and infiltrate through the pavement and into the aggregate layers and/or soil below. In addition to reducing surface runoff, permeable paving systems can trap suspended solids, thereby filtering pollutants from stormwater.

<span class="mw-page-title-main">Delamination</span> Mode of failure for which a material fractures into layers

Delamination is a mode of failure where a material fractures into layers. A variety of materials, including laminate composites and concrete, can fail by delamination. Processing can create layers in materials, such as steel formed by rolling and plastics and metals from 3D printing which can fail from layer separation. Also, surface coatings, such as paints and films, can delaminate from the coated substrate.

<span class="mw-page-title-main">Dowel bar retrofit</span> Highway crack treatment

A dowel bar retrofit (DBR) is a method of reinforcing cracks in highway pavement by inserting steel dowel bars in slots cut across the cracks. It is a technique which several U.S. states' departments of transportation have successfully used in repairs to address faulting in older jointed plain concrete pavements. The typical approach is to saw cut and jackhammer out the slots for the dowels. Following dowel placement the slots are then typically backfilled with a non-shrink concrete mixture, and the pavement is diamond-ground to restore smoothness.

<span class="mw-page-title-main">Thermal bridge</span>

A thermal bridge, also called a cold bridge, heat bridge, or thermal bypass, is an area or component of an object which has higher thermal conductivity than the surrounding materials, creating a path of least resistance for heat transfer. Thermal bridges result in an overall reduction in thermal resistance of the object. The term is frequently discussed in the context of a building's thermal envelope where thermal bridges result in heat transfer into or out of conditioned space.

Thermographic inspection refers to the nondestructive testing (NDT) of parts, materials or systems through the imaging of the temperature fields, gradients and/or patterns ("thermograms") at the object's surface. It is distinguished from medical thermography by the subjects being examined: thermographic inspection generally examines inanimate objects, while medical thermography generally examines living organisms. Generally, thermographic inspection is performed using an infrared sensor.

Infrared vision is the capability of biological or artificial systems to detect infrared radiation. The terms thermal vision and thermal imaging, are also commonly used in this context since infrared emissions from a body are directly related to their temperature: hotter objects emit more energy in the infrared spectrum than colder ones.

<span class="mw-page-title-main">Cellular confinement</span> Confinement system used in construction and geotechnical engineering

Cellular confinement systems (CCS)—also known as geocells—are widely used in construction for erosion control, soil stabilization on flat ground and steep slopes, channel protection, and structural reinforcement for load support and earth retention. Typical cellular confinement systems are geosynthetics made with ultrasonically welded high-density polyethylene (HDPE) strips or novel polymeric alloy (NPA)—and expanded on-site to form a honeycomb-like structure—and filled with sand, soil, rock, gravel or concrete.

<span class="mw-page-title-main">Infrared and thermal testing</span>

Infrared and thermal testing refer to passive thermographic inspection techniques, a class of nondestructive testing designated by the American Society for Nondestructive Testing (ASNT). Infrared thermography is the science of measuring and mapping surface temperatures.

"Infrared thermography, a nondestructive, remote sensing technique, has proved to be an effective, convenient, and economical method of testing concrete. It can detect internal voids, delaminations, and cracks in concrete structures such as bridge decks, highway pavements, garage floors, parking lot pavements, and building walls. As a testing technique, some of its most important qualities are that (1) it is accurate; (2) it is repeatable; (3) it need not inconvenience the public; and (4) it is economical."

Concrete has relatively high compressive strength, but significantly lower tensile strength. The compressive strength is typically controlled with the ratio of water to cement when forming the concrete, and tensile strength is increased by additives, typically steel, to create reinforced concrete. In other words we can say concrete is made up of sand, ballast, cement and water.

Terahertz nondestructive evaluation pertains to devices, and techniques of analysis occurring in the terahertz domain of electromagnetic radiation. These devices and techniques evaluate the properties of a material, component or system without causing damage.

Microwave imaging is a science which has been evolved from older detecting/locating techniques in order to evaluate hidden or embedded objects in a structure using electromagnetic (EM) waves in microwave regime. Engineering and application oriented microwave imaging for non-destructive testing is called microwave testing, see below.

Carbon fiber testing is a set of various different tests that researchers use to characterize the properties of carbon fiber. The results for the testing are used to aid the manufacturer and developers decisions selecting and designing material composites, manufacturing processes and for ensured safety and integrity. Safety-critical carbon fiber components, such as structural parts in machines, vehicles, aircraft or architectural elements are subject to testing.

Active thermography is an advanced nondestructive testing procedure, which uses a thermography measurement of a tested material thermal response after its external excitation. This principle can be used also for non-contact infrared non-destructive testing (IRNDT) of materials.

Welding of advanced thermoplastic composites is a beneficial method of joining these materials compared to mechanical fastening and adhesive bonding. Mechanical fastening requires intense labor, and creates stress concentrations, while adhesive bonding requires extensive surface preparation, and long curing cycles. Welding these materials is a cost-effective method of joining concerning preparation and execution, and these materials retain their properties upon cooling, so no post processing is necessary. These materials are widely used in the aerospace industry to reduce weight of a part while keeping strength.

References

  1. Kirk, Robert S.; Mallett, William J. (January 17, 2018). Highway Bridge Conditions: Issues for Congress (PDF). Washington, DC: Congressional Research Service. Retrieved 27 January 2018.
  2. Weil, Gary J. “Nondestructive Testing of Large Concrete Structures.” SPIE 3397 (1998).
  3. Weil, Gary J. Non Destructive Testing of Bridge, Highway and Airport Pavements, Gateway Engineer Magazine, 1992, pages 5-7
  1. Weil, Gary J. “Nondestructive Testing of Large Concrete Structures.” SPIE 3397 (1998).
  2. Weil, Gary J. "Non Destructive Testing of Bridge, Highway and Airport Pavements", Gateway Engineer Magazine, 1992, pages 5-7
  3. Weil, Gary J. "Toward an Integrated Nondestructive Pavement Testing Management Information System Using Infrared Thermography," Proceedings of the U.S. Transportation Research Board, Washington D.C., June 22, 1989
  4. Weil, Gary J. "Detecting the Defects", Civil Engineering Magazine, American Society of Civil Engineering, Volume 59, Number 9, 1989, pages 74-77