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Appendix. Box Beam Design Details

Publication Number: FHWA-HRT-17-093 Date: February 2018

Publication Number: FHWA-HRT-17-093
Date: February 2018

Adjacent Box Beam Connections: Performance and Optimization

APPENDIX. BOX BEAM DESIGN DETAILS

Drawings associated with the fabrication of the box beams are found in this appendix.

This illustration shows the box beam design details for beams with partial-depth connections. It is broken into five parts. The first part in the upper left-hand corner shows the external dimensions of the box beam as well as the spacing and sizing of the voids inside the beam, the size and position of the diaphragms, holes for post-tensioning (PT) and hold downs, and the spacing of the stirrup bars. It shows the beam as 50 ft (15.2 m) long with two 14-inch (356-mm) internal diaphragms 15 ft (4.6 m) away from each end. Precast holes are provided at the end and intermediate diaphragms for PT rods. Web stirrup bars are shown to be spaced every 16 inches (406 mm), and a 24-inch (610-mm) minimum lap distance is shown for the longitudinal bars. The second part in the upper right-hand corner details the reinforcement that is protruding from the ultra-high performance concrete (UHPC) connections. It has U hook bars spaced 16 inches (406 mm) on the center, with the first exposed reinforcement being 6 inches (152 mm) from the end of the beam. The third section is in the bottom right-hand corner and details the geometry of the UHPC shear key. The reinforcement protrudes 5.5 inches (140 mm) from the trapezoidal shear key that is 7 inches (178 mm) tall and 3 inches (76 mm) deep. It is indicated that in-form set retarders should be used on the surfaces of the UHPC shear key. The fourth section is at the bottom center and details the conventionally grouted shear key. This key is 14 inches (356 mm) deep and 0.75 inch (19 mm) wide. The fifth and final section is at the bottom left of the figure and depicts the reinforcement included in the beams. There are a total of 27 0.6-inch (15-mm) pretension strands in three layers. The first layer has 13 strands and is 2.25 inches (57 mm) from the bottom of the beam. The second layer has 12 strands and is 4.25 inches (108 mm) from the bottom of the beam. Four of these strands are debonded 60 inches (1.5 m) from the end of the beam, and another four strands are debonded 120 inches (3.0 m) from the end of the beam. The last two strands are located 28.25 inches (718 mm) from the bottom of the beam. There are four #4 (M13) bars in the top flange spaced at 8 inches (203 mm) on center. The top flange also includes five pieces of 0.75-inch (19-mm) copper tubing spaced 8 inches (203.2 mm) on the center.

Source: FHWA.
1 inch = 25.4 mm.
Figure 113. Drawing. Box design with partial-depth shear keys showing plan, elevation, section, and shear key details.

This illustration shows the box beam design details for beams with partial-depth connections. This figure is broken into four parts. The first part is at the top of the figure and includes the construction notes as well as the reinforcement schedule for all of the reinforcement. The notes include prestressing size and grade of 0.6 inch and 270 ksi (15 mm and 1,860 MPa), strand jacking force of 44 kip (196 kN), concrete strength of 4 ksi (27 MPa), and reinforcing grade 60 (grade 420M). The reinforcement schedule gives the number and dimensions for all the reinforcement in the beam. A total of 175 pieces of reinforcement are required: 16 straight, 139 U bars, and 12 hoops. The second section in the bottom right corner shows the elevation for the beam lifter detail. This detail shows the loops embedded in the beam ends to lift them with an overhead hoist. Two lifting hoops of 4.5-inch (144-mm) diameter strands are included at each end that are embedded 27 inches (686 mm) into the beam and protruding 8 inches (203.2 mm) from the top of the beam. The third part is in the bottom center of the figure and depicts the plan and elevation views of the diaphragm reinforcement. The top half of the figure shows the plan view, with two L bars 6 inches (152.4 mm) from either side of the beam. There are two additional horizontal bars on each side of the diaphragm mid-height, as seen in the elevation view on the bottom half. There is 1 inch (25.4 mm) clear cover in all cases. The fourth section at the bottom left shows the reinforcement detail at the end block of each beam. This part includes the plan and elevation views of the end reinforcement in the top and bottom of the section. The reinforcement used is typical of most end blocks with four horizontal U bars, six vertical L bars, and seven stirrups.

Source: FHWA.
1 inch = 25.4 mm.
Figure 114. Drawing. Box design with partial-depth shear keys showing notes, details, and reinforcement schedule.

This illustration shows the box beam design details for the beams with full-depth connections. This figure is broken into five parts. The first part in the upper left-hand corner shows the external dimensions of the box beam as well as the spacing and sizing of the voids inside the beam, the size and position of the diaphragms, holes for post-tensioning (PT) and hold downs, and the spacing of the stirrup bars. It shows the beam as 50 ft (15.2 m) long with two 14-inch (356-mm) internal diaphragms 15 ft (4.6 m) away from each end. Precast holes are provided at the end and intermediate diaphragms for PT rods. Web stirrup bars are shown to be spaced every 16 inches (406 mm), and a 24-inch (610-mm) minimum lap distance is shown for the longitudinal bars. The second part in the upper right-hand corner details the reinforcement that is protruding from the ultra-high performance concrete (UHPC) connections. It has U hook bars spaced 16 inches (406 mm) on the center, with the first exposed reinforcement being 6 inches (152 mm) from the end of the beam. The third section is in the bottom right corner and details the geometry of the UHPC shear key. The detail shows the reinforcement protruding 5.5 inches (140 mm) from the top trapezoidal shear key and 5 inches (127 mm) from the bottom trapezoidal shear key. The top trapezoidal key measures 6.813 inches (173 mm) tall and 2.625 inches (67 mm) deep. The bottom trapezoidal key measures 6.125 inches (156 mm) tall and 2.5 inches (64 mm) deep. It is indicated that in-form set retarders should be used on the surfaces of the UHPC shear key. The fourth section is at the bottom center and details the conventionally grouted shear key. This key is 25 inches (635 mm) deep and 0.75 inch (19 mm) wide. The fifth and final section is at the bottom left of the figure and depicts the reinforcement included in the beams. There are a total of 27 0.6-inch (15-mm) pretension strands in three layers. The first layer has 13 strands and is 2.25 inches (57 mm) from the bottom of the beam. The second layer has 12 strands and is 4.25 inches (108 mm) from the bottom of the beam. Four of these strands are debonded 60 inches (1.5 m) from the end of the beam, and another four strands are debonded 120 inches (3.0 m) from the end of the beam. The last two strands are located 28.25 inches (718 mm) from the bottom of the beam. There are four #4 (M13) bars in the top flange spaced at 8 inches (203 mm) on the center. The top flange also includes five pieces of 0.75-inch (19-mm) copper tubing spaced 8 inches (203.2 mm) on the center.

Source: FHWA.
1 inch = 25.4 mm.
Figure 115. Drawing. Box design with full-depth shear keys showing plan, elevation, section, and shear key details.

This illustration shows the box beam design details for the beams with full-depth connections. This figure is broken into four parts. The first part is at the top of the figure and includes the construction notes, as well as the reinforcement schedule for all of the reinforcement. The notes include prestressing size and grade of 0.6 inch and 270 ksi (15 mm and 1860 MPa), strand jacking force of 44 kip (196 kN), concrete strength of 4 ksi (27 MPa), and reinforcing grade 60 (grade 420M). The reinforcement schedule gives the number and dimensions for all the reinforcement in the beam. A total of 175 pieces of reinforcement are required: 16 straight, 139 U bars, and 12 hoops. The second section in the bottom right corner shows the elevation for the beam lifter detail. This detail shows the loops embedded in the beam ends to lift them with an overhead hoist. Two lifting hoops of 4.5-inch (144-mm) diameter strands are included at each end that are embedded 27 inches (686 mm) into the beam and protruding 8 inches (203.2 mm) from the top of the beam. The third part is in the bottom center of the figure and depicts the plan and elevation views of the diaphragm reinforcement. The top half of the figure shows the plan view, with two L bars 6 inches (152.4 mm) from either side of the beam. There are two additional horizontal bars on each side of the diaphragm mid-height as seen in the elevation view on the bottom half. There is 1 inch (25.4 mm) clear cover in all cases. The fourth section at the bottom left shows the reinforcement detail at the end block of each beam. This part includes the plan and elevation views of the end reinforcement in the top and bottom of the section. The reinforcement used is typical of most end blocks with four horizontal U bars, six vertical L bars, and seven stirrups.

Source: FHWA.
1 inch = 25.4 mm.
Figure 116. Drawing. Box design with full-depth shear keys showing notes, details, and reinforcement schedule.

Page Owner: Office of Research, Development, and Technology, Office of Infrastructure, RDT

Topics: research, infrastructure, structures
Keywords: research, structures, Box beam bridge, Connection, Shear key design, Transverse post-tension, Transverse shear, Transverse tension, Ultra-high performance concrete, UHPC
TRT Terms: research, infrastructure, Facilities, Structures
Scheduled Update: Archive - No Update needed

This page last modified on 10/10/2018