Pile integrity test
A pile integrity test (also known as low strain dynamic test, sonic echo test, and low strain integrity test) is one of the methods for assessing the condition of piles or shafts. It is cost effective and not very time consuming.
The test is based on wave propagation theory. The name "low strain dynamic test" stems from the fact that when a light impact is applied to a pile it produces a low strain. The impact produces a compression wave that travels down the pile at a constant wave speed (similarly to what happens in high strain dynamic testing). Changes in cross sectional area - such as a reduction in diameter - or material - such as a void in concrete - produce wave reflections.
This procedure is performed with a hand held hammer to generate an impact, an accelerometer or geophone placed on top of the pile to be tested to measure the response to the hammer impact, and a data acquisition and interpretation electronic instrument.
The test works well in concrete or timber foundations that are not excessively slender. Usually the method is applied to recently constructed piles that are not yet connected to a structure. However, this method is also used to test the integrity and to determine the length of piles embedded in structures.
This method is covered under ASTM D5882-00 - Standard Test Method for Low Strain Integrity Testing of Piles.
Girder bridge
A girder bridge, in general, is a bridge built of girders placed on bridge abutments and foundation piers. In turn, a bridge deck is built on top of the girders in order to carry traffic. There are several different subtypes of girder bridges:
A rolled steel girder bridge is made of I beams that are rolled into that shape at a steel mill. These are useful for spans between 10 meters and 30 meters (33 feet to 100 feet). Rolled steel girders are practically available with a web height of up to one meter (3 feet).
A plate girder bridge is made out of (mostly) flat steel sections that are later welded or otherwise fabricated into an I beam shape. Plate girders can have a greater height than rolled steel girders. Plate girder spans can be used for spans between 10 meters and more than 100 meters (33 feet to more than 330 feet). The web (vertical section) of a plate girder can be taller than that of a rolled steel girder, providing greater strength than a rolled steel girder. The thickness of the top and bottom flanges of a plate girder does not have to be constant; the thickness can be changed (typically at a field splice) to save on material costs. Stiffeners are occasionally welded between the compression flange and the web to increase the strength of the girder.
A concrete girder bridge is made of concrete girders, again in an I beam shape. The concrete girders can be either prestressed cast concrete or post-tensioned girders. Concrete girder bridges are best for spans between 10 meters and 50 meters (33 feet to 164 feet). Prestressed, precast concrete girders are readily available.
A box girder bridge is built from girders in a rectangular box shape instead of an I beam shape.
The stubs at the eastern end of the Dunn Memorial Bridge give a good cross section of girder bridge construction.
An I beam bridge is simple to design and build, and works well for straight spans. However, if the bridge needs to be curved, the beams are subject to twisting forces (torque). This can be alleviated by building several shorter, straight spans with a curved bridge deck, or by using box girders. Building metal box girders is more difficult, though, because the welding of the inner corners between the flanges and the webs has to be done either by a robot or a human, depending on who can fit inside
مشروع تقاطع الزهور -بغداد 2006
مقتربات جسر 14 رمضان -عام 1985
Curing Concrete“holding water in the concrete”
Will:
- Increase concrete strength
- Increase concrete abrasion resistance
- Lessen the chance of concrete scaling
- Lessen the chance of surface dusting
- Lessen the chance of concrete crackingCURING DEFINED
Curing can be defined as a procedure for insuring the hydration of the portland
cement in newly-placed concrete. It generally implies control of moisture loss and
sometimes of temperature. The hydration of portland cement is the chemical reaction
between grains of portland cement and water to form the hydration product, cement gel:
and cement gel can be laid down only in water-filled space. Hydration can proceed until all
the cement reaches its maximum degree of hydration, or until all the space available for the
hydration product is filled by cement gel, whichever limit is reached first.Water curing -is
when the
concrete is
covered with a
layer of water for
a period of time
and the
evaporation of
moisture is from
the surface of the
water.The curing of the concrete is dependent on the quality of the film, the thickness, and
the uniformity of the film applied to the concrete. The curing membrane used is the least
expensive component in the completion of quality concrete construction, and the most over
looked.
جسر مشاة في محافظة الانبار-عام 1987
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