Rebar: Steel Reinforcement for Concrete Structures
Thursday 17 July 2014
Three things would be Very Careful While lifting Anchors. Origin, Magnitude and Distribution of Load
Lifting anchors are loaded by the self weight of the concrete element, by forces due to adhesion and form friction and by dynamic actions due to acceleration.
The self weight of the precast concrete element can be calculated using a specific gravity of 23 to 25 kN/m3 for normal weight concrete, depending on the percentage of reinforcement. Mostly this value is already known from the static calculation.
Inertia forces act when the element is accelerated or decelerated by the lifting equipment. These forces must also be transferred by the lifting anchors. The size of the inertia forces scatters between 5 and 50 % of the elements weight depending on the type of crane and the ratio between the weight of the element and the capacity of the crane. Under normal conditions it should be conservative to calculate inertia forces with 30 % of the self weight . Additional considerations have to be made for special situations like transport of elements through rough terrain, for example with an excavator. Inertia forces up to 300 % of the self weight can be expected in such cases.
When the concrete element is lifted out of the mould, forces between the concrete and the formwork surface, due to adhesion and form friction must be added to the self weight. As long as the formwork is fixed to the floor or heavy enough to stay in place (it normally is), dynamic actions must not be considered together with adhesion and form friction. Only in cases where the form is not fixed and not heavy enough to stay in place, inertia forces have to be taken into account on the mass of the element and on the mass of the formwork as well. Later, when the element is moved in the precast plant or on site, self weight and inertia forces both have to be considered.
After the estimation of the forces acting on the element, forces on each anchor have to be calculated, taking into account the position of anchors, number and length of ropes or chains and the static system. In most cases, the aim is to have a statically determinate system, because then the forces on each anchor and on each rope or chain can be clearly calculated. In statically indeterminate systems, load distribution depends on length and stiffness of the ropes, which are mostly unknown. If statically indeterminate systems are used for special reasons, only the statically determinate part should be used in calculating the load distribution, and additional ropes or chains should only be used for stabilization.
Thursday 10 July 2014
Design Basis for (FRP) Fiberglass Reinforcement Concrete
A design basis for FRP reinforced concrete has been recommended by a number of standards and professional organization. The LRFD basis is recommended by the ACI 440,1R-03; at this time resistance factors are not probabilistically based. ;load factors are those recommended for all concrete structures by AC! 318-95 (1995)
For the design of flexural members reinforced with FRP rebars the ACI 440.1R-03 recommends the following resistance factors:
Flexural capacity (tensile reinforcement only):
ø= 0.5 for an under reinforced beam section (pf< pfb)
ø=0.7 for a substantially over reinforced beam section (pf> 1.4Pfb)
ø= 0.5pf/pfb, for a lightly over reinforced beam section (pfb< p < 1.4pfb)
Shear capacity (stirrups):
ø =0.85 per ACI 318-95.
where Pf is the FRP reinforcement ratio and Pfb is the balanced FRP reinforcement ratio.
Characteristic strength (also called the guaranteed strength) and strain to failure of FRP rebar’s are defined as the mean minus three standard deviations of a minimum of 25 test samples. The design strength, fro, and design failure strain, Efu, are obtained from the characteristic strength and failure strain by multiplying them by an environmental decline factor, CE, which relies on the fiber type in the bar and the type of intended service of the structure. For example, for weather exposed concrete with glass FRP rebar’s, CE is 0.7 (ACI 440.1R-03 2003).
Since FRP rebar’s typically have a lower modulus than steel rebar’s, the serviceability limit state (deflections and crack widths) can often control the design of FRP reinforced concrete sections. The ACI 440.1 R-03 provides procedures for calculating deflections and crack widths in FRP reinforced members.
Friday 20 June 2014
Do You Know TUF-BAR™ rebar is an environmentally friendly product.........!
Tuf Bar
Tuf Bar Solution (Fiberglass Rebar) |
Keeping excellence and worth in mind, every Tuf-Bar creation is crafted with high-class materials and progressive design. So, Tuf-Bar, step bars and Tuf-Bar bull bars are tough enough to survive day by day abuse, delivering the crucial protection for your journey. Actually, Tuf-Bar supports their stainless steel goods with an unbelievable Lifetime Warranty, and their black powder covered products come up with 3-years warranty.
In addition, most parts of the Tuf-Bar and accessories feature are very easy, no-drill fixing that you can complete yourself in just an hour.
When you are seeing for the best possible choice of Tuf-Bar parts at the lowly prices available, look no further than BP-Composites. We are dealing with a extensive collection of Tuf-Bar products, and we also give you a surety of the lowest prices. Plus, we can ship your Tuf-Bar get right to your front door with no cost
Tuesday 20 May 2014
Tie Your Home Wall's with Fiberglass Re-inforcing Bar
Reinforcing bar, or "rebar" as it is commonly known as is simply steel rod fixed in the concrete to tie all the
stonework together. Re-bar helps to safe your work from fracturing or breaking apart when the ground settles or shifts under your house.
If an proprietor desires to eliminate large amounts of conductive metal from structure, it is possible to use Fiberglass Reinforcing Bar. These re-bar's were originally made for bridges construction, because they do not rust, or dissolve from galvanic procedures. As fiberglass re-bar's cannot be turned onside and must be pre-ordered, you should plan well in advance if you want to use this product. It can be ordered through Till-co or V-rod. If you plan to use fiberglass re-bar's, ask your near code enforcement officials earlier to purchase whether they will accept a particular product.
We have used fiberglass effectively in a few homes, but have found it to be expensive and not convenient. You can also decrease electric fields by using foundation of metal re-bar's, but the presence of the metal can still give a potential pathway for stray magnetic fields.
I think Fiberglass re-bar's is a appropriate alternatives to steel reinforcing in architectural concrete, in concrete bare to de-icing or marine salts, and in concrete used near electromagnetic gear.
Re-bar is amazingly cheap, pricing only about three dollars for a 20-ft length of ½" diameter rod, but it still adds up when you buy a lot of it. Luckily, you can use about any practically clean, skinny peace of steel for re-bar's. We joined all the walls together in our house above the door and window frames with 40-ft lengths of 1" diameter steel cables we found. Our walls and footings are full of all types of other cables, steel fence posts and barb wire. You may find that masonry work can be productive way to clean up your neighbourhood.
Purchased rebar comes in many sizes such as 3/8", ½", 5/8". ¾", 1" etc. You can order it by the diameter, but in construction business it is known as #3, #4, #5, etc. The numbers stands for eighths, so #4 rebar means 4/8" or ½" rebar. That is normal size used in mainly masonry work. Re-bar comes in 20-foot lengths. You can always have it custom cut when you buy it, but an extra cost. It is just an simple way to pick up a masonry blade for a circular saw and cut your own.
There are non-steel options to rebar too. Some home builders have become anxious about the long term health effects of surrounding oneself in a metal cage. Fiberglass rebar is more expensive, but reduces this concern.
Monday 21 April 2014
Fiberglass Concrete Form Ties
Form-tie assemblies for
architectural concrete should permit tightening of forms and leave no metal
closer to the surface than I-1/2 inches (38 mm) for steel ties and 1 inch (25 mm)
for stainless tell ties. The ties should not be fitted with lugs, cones,
washers, or other devices that will leave depressions in the concrete less than
the diameter of the device, unless specified. Ties should be tight fitting or
tie holes in the form should be sealed to prevent leakage at the holes in the
form. If texture surfaces are to be formed, ties should be carefully evaluated
as to fit, pattern, grout leakage, and aesthetics.
Ties and Inserts
Form ties and accompanying tie
holes are an almost inescapable part of wall surface. Architects frequently tie
holes into the visual design quality of the surface. If this is planned and any
effects or materials other than those provided in the upper heading are
desired, they should be clearly specified as to both location and type.
Where tie holes are to patched or
fitted, the architect should specify the treatment desired, unless it has been
shown on the pre-construction mock up.
Monday 7 April 2014
Fiberglass Reinforced Concrete
Fiberglass reinforced concrete is
composed of cement-rich concrete or mortar modified with additive and
reinforced with alkali-resistant glass fibers. Colors is provided by the cement
and aggregated used in the mix, or from a small proportion of added pigment. The
material is sprayed or poured into forms to create thin-shelled panels, 12.7 to
15.8mm (1/2 to 5/8 in) thick with an anchorage system embedded in the
fiberglass reinforced concrete. The panels, which can be left uncoated or
painted, are erected on concrete or steel structural frames.
Fiberglass Reinforced Concrete is
a relatively recent (30 years) technological development. It has been used
primarily for architectural claddings. The combination of glass fibers with
concrete technology has created its own set of issues to be addressed,
including loss of strength, embrittlement of the glass fibers, and variable
expansion and contraction characteristics.
Fiberglass reinforced concrete
has the following advantages;
- The material is lightweight compared to cast stone, terra cotta, and precast concrete, and is therefore easier to handle during installation.
- Fiberglass reinforced concrete can be readily molded into panels with intricate details. Because it adapts easily to molding. Section of repetitive design or sculptural element can be produced efficiently.
- Less shrinkage occurs during fabrication than with terra cotta or cast metal. It may therefore be possible to make molds for fiberglass reinforced concrete units directly from the existing elements to be replicated.
- Fiberglass reinforced concrete is vapor permeable, and therefore moisture that enters the unit can escape. This mitigates the potential for damage to occur from entrapped moisture.
- Fiberglass reinforced concrete is fire resistant.
Wednesday 12 March 2014
Fiberglass Rebar
I cannot exaggerates the need for
appropriate reinforcement. When earthquakes kill thousands of people in foreign
lands. Generally, because people are existing in masonry type homes that do
not have any sort of reinforcement bar. Masonry construction with concrete,
stone, adobe, mud, etc., all are very inflexible. These sorts of materials do
not flex with the shaking earth, so they break into pieces.
Reinforcement bar, or “rebar”
commonly known as steel rod rooted in the concrete to attach all the masonry work
together. Rebar helps to guard your work with fracturing or breaking apart when
the ground mend or shifts under your house.
Reinforcement bar is extremely
cheap, estimate only three dollars for 20-foot length of ½” diameter rod, but it’s
still includes up when you purchase a lot of it.
The most significant part is to ensure
you always include enough reinforcement, no matter where you are building. If
you are using unprepared reinforcement material then make sure to add extra.
It is also significant to
consider the adjustment of rebar in the masonry. As illustrated, reinforcement
provides the most strength if positioned opposite the load. In footing and
beams that means the rebar is placed near the bottom.
Adjustments issues and fix
working together etc., BP Composites is providing you each and every solution regarding
fiberglass reinforcement bars.
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