5.3—Interior reinforcement
5.3.1 Description (repair of cracks)—A common method
of providing additional reinforcement across cracked surfaces
is to install new dowels into holes drilled perpendicular to
the crack surfaces. The entire length of the dowel is fixed to
the concrete by the use of a bonding matrix. Figure 5.1 to 5.4
show this repair method.
The structure should be shored and jacked if it is desired
to relieve the member’s dead load stresses so the new reinforcement
resists the original dead load. At yield stress,
however, the added reinforcement would normally be effective
in resisting all loads.
Several bonding materials may be used. Portland-cement
grouts, epoxy, epoxy mortar, latex-modified cement slurry,
and other chemical adhesives have been successfully
installed within the annular space between the dowel and
sides of the predrilled hole. Creep, shear stress, tensile-bond
strength, and other long-term changes of such resins and
grouts should be considered when selecting the materials. In
addition, properties such as heat generation and shear
strength should be considered when sizing the hole diameter
for dowels or anchors.
The dowels may be deformed reinforcement, smooth, or
threaded steel or stainless steel bars, carbon fiber reinforcement,
or bolts. Coating steel dowels with either zinc galvanizing or
fused epoxy is acceptable if all components are chemically
compatible with the bonding material. The protective coating of
dowels should be considered when evaluating the bond
strength between concrete and dowel.
Dowels for providing shear transfer between adjoining
sections of moving pavement may be placed in slots cut from
the top to mid-depth of the adjoining sections. In one section,
the dowel is bonded; in the other, the dowel is unbonded
using a sleeve or debonding agent.
5.3.2 Advantages and typical uses—Internal reinforcement
can strengthen concrete cracked by flexural and shear
stresses and restrained volume changes. The repair procedure is
simple and uses commonly available equipment.
5.3.3 Limitations—Cutting or damaging existing
embedded reinforcing bars or conduits during the drilling
operation should be avoided. Nondestructive testing and
design drawings can be used to determine the locations of
embedded items. Heavily reinforced structural members
may not permit drilling, and these members should be
strengthened by external techniques.
Space constraints from the outside of the member may
5.3—Interior reinforcement5.3.1 Description (repair of cracks)—A common methodof providing additional reinforcement across cracked surfacesis to install new dowels into holes drilled perpendicular tothe crack surfaces. The entire length of the dowel is fixed tothe concrete by the use of a bonding matrix. Figure 5.1 to 5.4show this repair method.The structure should be shored and jacked if it is desiredto relieve the member’s dead load stresses so the new reinforcementresists the original dead load. At yield stress,however, the added reinforcement would normally be effectivein resisting all loads.Several bonding materials may be used. Portland-cementgrouts, epoxy, epoxy mortar, latex-modified cement slurry,and other chemical adhesives have been successfullyinstalled within the annular space between the dowel andsides of the predrilled hole. Creep, shear stress, tensile-bondstrength, and other long-term changes of such resins andgrouts should be considered when selecting the materials. Inaddition, properties such as heat generation and shearstrength should be considered when sizing the hole diameterfor dowels or anchors.The dowels may be deformed reinforcement, smooth, orthreaded steel or stainless steel bars, carbon fiber reinforcement,or bolts. Coating steel dowels with either zinc galvanizing orfused epoxy is acceptable if all components are chemicallycompatible with the bonding material. The protective coating ofdowels should be considered when evaluating the bondstrength between concrete and dowel.Dowels for providing shear transfer between adjoiningsections of moving pavement may be placed in slots cut fromthe top to mid-depth of the adjoining sections. In one section,the dowel is bonded; in the other, the dowel is unbondedusing a sleeve or debonding agent.5.3.2 Advantages and typical uses—Internal reinforcementcan strengthen concrete cracked by flexural and shearstresses and restrained volume changes. The repair procedure issimple and uses commonly available equipment.5.3.3 Limitations—Cutting or damaging existingembedded reinforcing bars or conduits during the drillingoperation should be avoided. Nondestructive testing anddesign drawings can be used to determine the locations ofembedded items. Heavily reinforced structural membersmay not permit drilling, and these members should bestrengthened by external techniques.Space constraints from the outside of the member may
การแปล กรุณารอสักครู่..
