Expansion anchors

ANCHOR BOLTS AS REQUIRED WOOD CANT SECURED WITH EXPANSION ANCHORS OR BOLT"IN CONCRETE CANT-... 

Post-installed bolts will be required at times for attachment of equipment which may be subjected to large accelerations during a blast. Expansion anchors should be avoided for most blast design applications unless the load levels are low. Typically "wedge" type anchors are qualified for dynamic loads although most of these ratings are for vibratory loads and are based on cyclic tests at low stress levels. These should only be used where ultimate loads are less than the rated capacity with a margin of safely. Epoxy anchors have shown excellent dynamic capacity and may be considered for critical applications. 

VJhen choosing any type of expansion joint or bend it is essential that a number of important factors be considered. These include the required Traverse, presetting, pipe expansion, anchors, alignment and supports. 

The racks for the storage of shim-safety rods are confined to groups of 16, four in a row and four tiers high. One rack is installed, while the future installation of racks in the other side of the canal is provided for by expansion anchors for the racks in the floor of the canal. 

Expansion anchors transfer tension loads to the hase material via friction between the expansion elements of the anchor and the wall of the hole. The magnitude of the friction resistance is directly proportional to the degree of expansion force developed by the anchor. Expansion forces are produced in response to the relative movement of sloping surfaces within the anchor mechanism. The maimer in which this relative movement is produced is important for distinguishing the anchor function in response to tension loads. The two most common mechanisms for producing expansion forces are represented by displacement-controlled and torque-controlled anchors ... 

Undercut anchors represent a superior class of post-installed mechanical anchor. By relying on bearing to transfer tension loads, they offer several advantages over expansion anchors ... 

Screw anchors (Figure 4.4) transfer tension loads via the interlock of the screw threads with matching female threads cut into the concrete by the hardened forward threads. They are often used for light and medium-duty applications where speed and ease of installation are a factor. The high hardness required for cutting the threads into the concrete makes screw anchors susceptible to hydrogen embrittlement and stress corrosion, particularly under the head, and caution should be exercised where they are used in unprotected environments. Depending on the depth of the threads, screw anchors may have superior tension resistance relative to other expansion anchor types in cracked concrete conditions. 

Post-installed anchor connections may be deserving of special attention if they a) transfer loads as part of the structural load path of a building or other structure, b) are used in a building or structure that has been assigned a high importance classification (for example, emergency response facilities), or c) should be designed with post-installed anchor systems that are more robust. Post-installed anchor bolts that tend to be more robust include most undercut anchor systems, some heavy-duty expansion anchors, and many adhesive anchor systems. 

When setting the bonded anchor, no expansion forces are produced. These forces are produced due to all types of fastening on the prestress and due to the loading of the anchor. However, they are much lower than for metal expansion hence, anchors are bonded especially at small component thicknesses and fixtures with a low edge distance to the mechanical expansion anchors (Geiss 2006b). 

Use EPRI data (EPRI NP-5228, Seismic Verification of Nuclear Plant Equipment Anchorage, Volume 1, Development of Anchorage Guidelines, May 1987) converted to the 2500 psi concrete for cast-in-place and grouted-in-place bolts, expansion, lead shield and lead cinched anchors. Use safety factors of 3 and 4 for non-shell and shell expansion anchors, respectively. Use 1973 AISC Code (Manual of Steel Construction, 7th Edition) requirements for steel connecting members and bolts. Use ACI Standard 349-85 (Code Requirements for Nuclear Safety Related Concrete Structures, 1985) for concrete evaluation. 

Thermal-expansion and -contraction loads occur when a piping system is prevented from free thermal expansion or contraction as a result of anchors and restraints or undergoes large, rapid temperature changes or unequal temperature distribution because of an injection of cold liquid striking the wall of a pipe cariying hot gas. 

Bending or torsional flexibihty may be provided by bends, loops, or offsets by corrugated pipe or expansion joints of the bellows type or by other devices permitting rotational movement. These devices must be anchored or otherwise suitably connected to resist end forces from fluid pressure, frictional resistance to pipe movement, and other causes. 

Expansion joints for free-movement systems can be designed for axial or offset movement alone, or for combined axial and offset movements (see Fig. 10-171). For offset movement alone, the end load due to pressure and weight can be transferred across the joint by tie rods or structural members (see Fig. 10-172). For axial or combined movements, anchors must be provided to absorb the imbalanced pressure load and force bellows to deflect. 

To protect terminal equipment or other (weaker) portions of the system, restraints (such as anchors and guides) shall be provided where necessary to control movement or to direct expansion into those portions of the system that are adequate to absorb them. The design, arrangement, and location of restraints shall ensure that expansion-joint movements occur in the directions for which the joint is designed. In addition to the other thermal forces and moments, the effects of friction in other supports of the system shall be considered in the design of such anchors and guides. 

Anchors for Expansion Joints Anchors (such as those of the corrugated, omega, disk, or shp type) shall be designed to withstand the algebraic sum of the forces at the maximum pressure and temperature at which the joint is to be used. These forces are ... 

The force required to overcome the static friction of the pipe in expanding or contracting on its supports, from installed to operating position. The length of pipe considered should be that located between the anchor and the expansion joint. 

The amount of movement to be taken up by the piping and any device incorporated into it can be reduced by the use of cold draw . The total amount of expansion is first calculated for each section between fixed anchor points. The pipes are left short by half this amount, and stretched cold, as by pulling up bolts at a flanged joint, so that at ambient temperature the system is stressed in one... 

If expansion fittings are to work as intended, it is essential that the steam line is properly anchored at some point between the expansion fittings. Guiding is also important to ensure that any movement does not interfere with the designed fall towards the drain points. 

Piping should easily fit the compressor connections without needing to spring or twist it to fit. It must be supported independently of the compressor and anchored, as necessary, to limit vibration and to prevent expansion strains. Improperly installed piping may distort or pull the compressor s cylinders or casing out of alignment. 

The dimensions of typical standard saddle designs are given in Figure 13.26. To take up any thermal expansion of the vessel, such as that in heat exchangers, the anchor bolt holes in one saddle can be slotted. 

We used recombinant DNA technology to design unique substrates for in vitro expansion of rat NSCs. For example, we fused a small peptide sequence of six consecutive histidine (His) residues to the C-terminus of human EGF (EGF-His). This EGF-His was anchored to the surface of a glass-based substrate by coordination with Ni2+ ions, which were fixed on the surface of a SAM of alkanethiol. Strikingly, neither a covalently immobilized EGF-His nor a physically adsorbed... 

The method for immobilizing EGF-His on SAMs gave rise to the need for fabricated cultureware that could allow large-scale expansion of pure NSCs. We attempted to construct culture modules with surface areas much larger than the laboratory-scale substrates described above. For uniformly anchoring EGF-His over a large area, we utilized a glass plate with amine functionalities on the surface. 

Nakaji-Hirabayashi T, Kato K, Iwata H (2009) Surface-anchoring of spontaneously dimerized epidermal growth factor for highly selective expansion of neural stem cells. Bioconjug Chem 20 102-110... 

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