Two precast girders with welded splices were tested as simply supported beams to determine the resistance of the splices to shear. The girders consisted of thin web channels assembled by welding to produce members of a hollow section. The addition of six Inclined bars on each side of the welded splices in Tee-Head No. 3 resulted in a marked increase in the shear resistance of the specimen as compared with Tee-Head No. 2 which contained no inclined stirrups.
Four box girders with lap welded splices were tested to determine the effect of rotation of eccentrically loaded lap welded reinforcing bars on the lateral rigidity of the splice and precast thin-shelled concrete framing members. Each specimen was made of six precast thinshelled elements that were welded and spliced together to form a hollow box girder 1-by 2-ft in cross section and 8 ft 10 in. long. These girders were used to compare the relative rigidities of lap welded splices with and without transverse reinforcement.The comparative results of flexural tests of these girders indicate that there was little difference in the observed lateral displacements up to stresses in splices of about 35,000 psi.However, at higher stresses, the lateral movement of the end portion of the girders and the concrete surrounding the splices was significantly greater in the girders which contained no transverse reinforcement .
Five specimens representing grout pocket assemblies used to protect welded joints in precast concrete panels were subjected to 250 cycles of freezing and thawing in order to determine the effectiveness of epoxy/Thiokol adhesives when applied to the surfaces of grout pockets prior to grouting. The specimens of plain concrete were cast in two halves and were 14-by 14-by 2 5/8 in. in size when placed together. The resulting grout pocket was 8 1/4 in. square at the top surface and 1 5/8 in. deep. The sides of the pockets were cast at an angle of 45°w ith the horizontal so that the bottom of the pocket was a 5 in. square. The sides and bottom of four of the specimens were coated with various epoxy/ Thiokol adhesive compounds just prior to grouting.The fifth specimen was used as a control specimen and was not coated. The specimens were frozen in air at a temperature of 2 ± 1°F, and were thawed in a water bath at a temperature of 77 ± 1°F. The control specimen failed after 96 cycles of freezing and thawing while no visible damage was apparent in the coated specimens after 250 cycles. These results clearly indicate that the use of epoxy/Thiokol adhesive mixtures significantly increases the durability of grout pocket assemblies by improving the bond between the grout and the hardened concrete.
Currently used lead paint hazard elimination techniques have been analyzed in terms of the attributes that can be associated 'with those methods. The attributes are concerned with hazard inaccessibility, implementation considerations, and in use performance properties. Cost implications can be associated with each of the factors involved in implementation. i
The rigidity and strength of two precast girders with welded splices of two different designs were determined in tests of the girders as beams continuous over three supports. The girders consisted of three reinforced concrete box sections welded and grouted together to form a beam 1-by 2-ft in cross section and 2 $ ft long.The splices located at points of inflection were formed by lap welding suitable lengths and amounts of positive and negative reinforcement projecting from the ends of adjoining sections and then grouting the pockets . The designs of the splices of the two girders were identical, except that girder No. 2 contained an additional amount of reinforcement consisting of three inclined stirrups of No, I 4 . bars on each side of the splice. The addition of the inclined stirrups resulted in an Increase of 6? percent in load carrying capacity of girder No. 2 as compared with girder No. 1, 1.
Two additonal specially designed specimens were constructed and subjected to pure bending following the completion of the investigation in which twenty nine 5-by 5-ft prestressed cellular slabs tested under concentrated loads (see NBS Report 6321).One slab was made of reinforced blocks and the other was made of unreinforced blocks.Both slabs contained epoxy resin joints and were prestressed to 1000 psi in both directions. De-flections, strains, crack patterns, and maximum bending moments were recorded.Since the cellular portions of the slabs were not subjected to shear, both slabs developed flexural failures as the top flanges of the blocks failed in compression.
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