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Abstract:
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This study developed a ductile concrete for precast wall systems which are capable of resisting high wind in excess of 500 mph . The developed concrete mix design consists of sand , cement , glass fiber , and a foaming agent to produce lightweight concrete in the range of 87 pcf (1392 kg /m3 ) to 90 pcf (1440 kg /m3 ) .
A comprehensive testing program for evaluation of the developed concrete material was undertaken . The mix designs were prepared both in the laboratory and in the mix truck with drum capacity of 27 ft3 (0 .77 m3 ) , and 177 .6 ft3 (5 m3 ) , respectively . The large concrete batches using trucks were prepared at the Hanson plants in Grand Prairie , Texas and News Orleans , Louisiana .
The material test included : 188 compressive strength tests (ASTM C39 ) ; 166 Modulus of rupture tests (ASTM C78 ) ; and 310 Pull -out test (ASTM C234 -86 ) for both sites . From each mix design , three specimens for 1 , 3 , 7 , 14 , 28 , 56 , and 90 day (s ) were prepared and tested on the designated test day . The relationships between the concrete unit weight and each of the a aforementioned properties were obtained and recorded .
Two types of pull out test (ASTM C234 -86 ) were conducted : (1 ) the steel bar ( #4 ) was embedded at 4 in . (10 .16 cm . ) in the 6 in . (152 .4 mm . ) x 12 in . (304 .8 mm . ) cylinders and (2 ) the steel bar was embedded at 12 in . (304 .8 mm . ) in the 6 in . (152 .4 mm . ) x 12 in . (304 .8 mm . ) cylinders . This was done to document both the pull -out and fracture mode of the failure during the pull -out test .
Full -scale beam tests with specimen sizes of 8 in . (20 .32 cm . )x 20 in . (50 .8 cm . ) x 96 in . (243 .8 cm . ) were conducted with and without reinforcements . A total of 124 beams (95 without reinforcement and 29 with reinforcement ) were tested in four -point bending . The crack patterns and failure loads were identified and recorded . Also , the behavior of the non -reinforced full -size test beams were compared with the ASTM C78 beams . The full -scale testing was continued by testing lightweight precast wall panel with two types of opening configurations : (1 ) window opening and (2 ) door opening . Four full -scale walls were tested by being subjected to a single concentrated load at the center of the panel and being loaded to failure . These wall panels were cast at the Hanson's News Orleans's site (Site2 ) and were transported for testing to the University of Texas at Arlington structural field laboratory at the Hanson's Grand Prairie plant (site1 ) . The wall panels were loaded to failure in an incremental manner and the crack initiation and propagations were identified and recorded . Also the load -deformation plots were obtained .
Finally , a three dimensional nonlinear finite element model (FEM ) of the wall panels were developed which included elements for the lightweight ductile concrete and the reinforcements . The material geometric and contact algorithms were coupled with the smeared crack model was incorporated in the analysis . The developed FEM is capable of predicting crack initiation and propagation which verified against the experimental tests . Also , the load -deformation plots from the experimental results were compared with those obtained from the FEM analysis , which showed very close correlations . |