Browsing by Subject "Anchorage"

Now showing 1 - 5 of 5
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    Anchorage of Epoxy-Coated Rebar Using Chemical Adhesives
    (2018-09) Mills, Connor
    Post-installed reinforcement is used to connect a new concrete member to an existing concrete structure. Typically, uncoated rebar post-installed with a chemical adhesive is used in these applications, which may lead to corrosion. Departments of Transportation and local bridge owners have used and continue to use epoxy-coated rebar in post-installed applications due to its inherent corrosion resistance. Unfortunately, chemical adhesive manufacturers provide tensile strengths of their products for use with uncoated rebar and not epoxy-coated rebar. This work examined what effects the epoxy coating had on the tensile pullout strength and compared the results for epoxy-coated and uncoated rebar. Two slabs were constructed. One slab contained epoxy-coated rebar post-installed using four different chemical adhesive products and the other slab contained uncoated rebar post-installed using the same four different chemical adhesive products. Results indicated that the epoxy coating slightly reduced the tensile pullout strength of the post-installed rebar. The ratio of the tensile pullout strength of the epoxy-coated reinforcing bars to the tensile pullout strength of the uncoated reinforcing bars ranged from 0.94 to 1.05 and varied based on the chemical adhesive manufacturer. T-Test results indicated that differences in the tensile pullout strength for epoxy-coated rebar compared to uncoated rebar were statistically different when using three of the four chemical adhesives during installation.
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    Anchorage of shear reinforcement in prestressed concrete bridge girders
    (2014-06) Mathys, Brian Thomas
    The Minnesota Department of Transportation has typically used epoxy coated straight legged stirrups anchored in the tension zone as transverse reinforcement in prestressed concrete bridge girders. With the straight legs of the U-shaped stirrups anchored into the bottom flange of the girders, this configuration is readily placed after stressing the prestressing strands. American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO) specifications require stirrups with bent legs that encompass the longitudinal reinforcement to properly anchor the stirrups. Such a configuration is specified to provide mechanical anchorage to the stirrup, ensuring that it will be able to develop its yield strength with a short anchorage length to resist shear within the web of the girder. AASHTO specifications for anchoring transverse reinforcement are the same for reinforced and prestressed concrete; however, in the case of prestressed concrete bridge girders, there are a number of differences that serve to enhance the anchorage of the transverse reinforcement, thereby enabling the straight bar detail. These include the precompression in the bottom flange of the girder in regions of web-shear cracking. In addition, the stirrup legs are usually embedded within a bottom flange that contains longitudinal strands outside of the stirrups. The increased concrete cover over the stirrups provided by the bottom flange and the resistance to vertical splitting cracks along the legs of the stirrups provided by the longitudinal prestressing reinforcement outside of the stirrups help to enhance the straight-legged anchorage in both regions of web-shear cracking and flexure-shear cracking. A two-phase experimental program was conducted to investigate the anchorage of straight legged epoxy coated stirrups that included bar pullout tests performed on 13 subassemblage specimens which represented the bottom flanges of prestressed concrete girders in a number of configurations to determine the effectiveness of straight legged stirrup anchorage in developing yield strains. Additionally, four girder ends were cast with straight legged stirrup anchorage details and tested in flexure-shear and web-shear. The straight leg stirrup anchorage detail was determined to be acceptable for Minnesota Department of Transportation M and MN shaped girders as nominal shear capacities were exceeded and yield strains were measured in the stirrups prior to failure during each of the tests.
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    Bond Behavior of Post-Installed GFRP Bars in Structural Connections
    (2018-06) Bajwa, Muhammad Shahraiz
    This research presents an experimental study with GFRP bars from three manufacturers, each having different bar textures (silica coated with helical wraps, silica coated and ribbed) used as post-installed (epoxy and cementitious adhesive) and cast-in-place reinforcement. Twenty test specimens were constructed and tested under static load. A test specimen was composed of two identical vertical elements, which were anchored into the base of the specimen using post-installed GFRP bars. The variables tested among different specimens included: concrete compressive strength (3 and 6 ksi), embedment length of GFRP bars (6 and 11.5 in.), and size of the post-installed GFRP bars (#4, #6, and #8). Concrete breakout was the only failure mode in all of the specimens with post-installed GFRP. Bond strengths and peak applied loads improved by increasing concrete strengths and embedment depths. The larger diameter bars (#6 and #8) showed a loss of bond strength compared to #4 bars.
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    Comprehensive evaluation of multistrand post-tensioning anchorage systems for seismic resilient rocking wall structures
    (2013-05) Abramson, Daniel Arden
    This thesis presents results from a comprehensive laboratory evaluation of the fracture and ultimate strength and deformation capacities of multistrand PT anchorage systems for use in seismic resilient rocking wall structures. The testing program encompassed two anchorage manufacturers, two anchorage alignment configurations, and two wedge geometries under both monotonic and cyclic loading.
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    Embedded Plate Anchorage Strength in Precast Hollowcore Slabs
    (2024-06) Entinger, Justin
    In current practice, hollowcore slabs are connected to supporting elements bycasting a headed stud embedment plate in the hollowcore. This provides an area that can be welded to the supporting elements. When the supporting elements consist of foundation retaining walls or exterior walls, load is applied to the supporting element and is transferred to the hollowcore in the form of shear force. The capacity of anchors cast-in concrete can be calculated using design codes for structural concrete; however, these design procedures were developed using experimental data on solid concrete slabs. Due to the longitudinal voids in hollowcore slabs, it is uncertain if the design procedures developed for solid concrete apply to hollowcore. This research aimed to determine the applicability of the current design procedures to hollowcore and provide insight into the anchorage strength of the embedded plate in hollowcore slabs. Experimental testing was performed on hollowcore slabs to establish the anchorage strength in three directions. The results indicated that for the out-of-plane suction direction the headed stud nearest the slab edge may not be effective and the anchorage capacity should be designed using only the headed stud further from the slab edge. Additionally, the breakout strength in this direction should be calculated using a projected failure area that accounts for the longitudinal voids. The predicted failure mode matched the experimental failure mode for most tests, but the experimental capacity varied in comparison to the predicted capacity for the tests.