Web Results
Content Results
  • Culvert


    Steel culvert with a plunge pool below A multiple culvert assembly in Italy A stone lintel culvert or box culvert. A culvert under the Vistula river levee and a street in Warsaw. A culvert is a structure that allows water to flow under a road, railroad, trail, or similar obstruction from one side to the other side. Typically embedded so as to be surrounded by soil, a culvert may be made from a pipe, reinforced concrete or other material. In the United Kingdom, the word can also be used for a longer artificially buried watercourse. Culverts are commonly used both as cross-drains for ditch relief, and to pass water under a road at natural drainage and stream crossings. A culvert may be a bridge-like structure designed to allow vehicle or pedestrian traffic to cross over the waterway while allowing adequate passage for the water. Culverts come in many sizes and shapes including round, elliptical, flat-bottomed, open-bottomed, pear-shaped, and box-like constructions. The culvert type and shape selection is based on a number of factors including requirements for hydraulic performance, limitations on upstream water surface elevation, and roadway embankment height.

  • Precast concrete


    A precast concrete walled house under construction An example of low-quality precast concrete with exposed dowels, connectors, indications of cracks, and malformations, even during its installation.Barangay Lantic, Carmona, Cavite, Philippines Interior view of the walls, supports, and roof of a precast commercial shop. Utilities are preassembled into the precast components.Williston, North Dakota, USA.Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place ("tilt up"). In contrast, standard concrete is poured into site-specific forms and cured on site. Precast stone is distinguished from precast concrete using a fine aggregate in the mixture, so the final product approaches the appearance of naturally occurring rock or stone. More recently expanded polystyrene is being used as the cores to precast wall panels. This is lightweight and has better thermal insulation. Precast is used within exterior and interior walls. By producing precast concrete in a controlled environment (typically referred to as a precast plant), the precast concrete is afforded the opportunity to properly cure and be closely monitored by plant employees. Using a precast concrete system offers many potential advantages over onsite casting. Precast concrete production can performed on ground level, which helps with safety throughout a project. There is greater control over material quality and workmanship in a precast plant compared to a construction site. The forms used in a precast plant can be reused hundreds to thousands of times before they have to be replaced, often making it cheaper than onsite casting when looking at the cost per unit of formwork. Many state and federal transportation projects in the United States require precast concrete suppliers to be certified by either the Architectural Precast Association (APA), National Precast Concrete Association (NPCA) or Precast Prestressed Concrete Institute (PCI). There are many different types of precast concrete forming systems for architectural applications, differing in size, function, and cost. Precast architectural panels are also used to clad all or part of a building facades or free-standing walls used for landscaping, soundproofing, and security walls, and some can be prestressed concrete structural elements. Stormwater drainage, water and sewage pipes, and tunnels make use of precast concrete units. The New South Wales Government Railways made extensive use of precast concrete construction for its stations and similar buildings. Between 1917 and 1932, they erected 145 such buildings. Beyond cladding panels and structural elements, entire buildings can be assembled from precast concrete. Precast assembly enables fast completion of commercial shops and offices with minimal labor. For example, the Jim Bridger Building in Williston, North Dakota, was precast in Minnesota with air, electrical, water, and fiber utilities preinstalled into the building panels. The panels were transported over 800 miles to the Bakken oilfields, and the commercial building was assembled by three workers in minimal time. The building houses over 40,000 square feet of shops and offices. Virtually the entire building was fabricated in Minnesota. To complete the look of the four precast wall panel types — sandwich, plastered sandwich, inner layer and cladding panels — many surface finishes are available. Standard cement is white or grey, though different colors can be added with pigments or paints. The color and size of aggregate can also affect the appearance and texture of concrete surfaces. The shape and surface of the precast concrete molds have an effect on the look: The mold can be made of timber, steel, plastic, rubber or fiberglass, each material giving a unique finish.

  • Box girder bridge


    Erskine Bridge, near Glasgow. Single box girder bridge (concrete), Australia. A similar bridge on this river was fabricated ashore and pushed across its pylons. Single box girder bridge (steel), flyover above eastern approach of the San Francisco–Oakland Bay Bridge. A box girder bridge is a bridge in which the main beams comprise girders in the shape of a hollow box. The box girder normally comprises either prestressed concrete, structural steel, or a composite of steel and reinforced concrete. The box is typically rectangular or trapezoidal in cross-section. Box girder bridges are commonly used for highway flyovers and for modern elevated structures of light rail transport. Although normally the box girder bridge is a form of beam bridge, box girders may also be used on cable-stayed bridges and other forms.

Map Box 1