Precast concrete beam

1. A precast concrete bridge beam for use in construction of a long span vehicle bridge structure, the beam including:

a) a substantially planar web extending longitudinally between ends of the beam;

b) a pair of flanges formed integrally with the web, each flange extending laterally from a first elongate edge of the web and extending longitudinally between the ends of the beam so as to define a structure engaging surface of the beam;

c) an enlarged bulb formed integrally with the web, the bulb extending along a second elongate edge of the web opposing the flanges, an array of prestressed reinforcement members being located inside the bulb;

d) a plurality of diaphragms formed integrally with the web and the flanges, each diaphragm spanning laterally between a side of the web and one of the flanges, wherein each diaphragm is substantially triangle shaped and a portion of each diaphragm is connected to the bulb, and wherein the diaphragms are spaced apart along the beam to thereby support the flanges; and,

e) an end block at each end, each end block being formed integrally with an end portion of the web and having a substantially increased thickness compared to a thickness of the web.

2. A beam according to claim 1 , wherein the beam is cast from concrete as a unitary body.

3. A beam according to claim 1 , wherein the beam includes at least one pair of diaphragms such that the diaphragms in each pair span between respective sides of the web and respective flanges at the same longitudinal position along the beam.

4. A beam according to claim 3 , wherein the beam includes a plurality of pairs of diaphragms, each pair of diaphragms being spaced apart by a spacing distance, and wherein the spacing distance is selected so that at least one of:

a) a load applied to an outer portion of one of the flanges will be transmitted to the web via one of the diaphragms;

b) the spacing distance is less than 30 times a flange thickness of the flanges; and,

c) the spacing distance is between 20 times the flange thickness and 30 times the flange thickness.

5. A beam according to claim 1 , wherein the beam includes a plurality of reinforcement members located inside the beam, and wherein at least some of the reinforcement members are prestressed when the beam is formed.

6. A beam according to claim 1 , wherein the beam includes two secondary beams, each secondary beam being formed integrally with one of the flanges and extending longitudinally between ends of the beam, and wherein at least one of:

a) the two secondary beams are offset laterally from opposing sides of the web;

b) each secondary beam protrudes from the flange away from the structure engaging surface;

c) each secondary beam is located at an intermediate position with respect to the perpendicular extension of the respective flange from the web, such that an inner flange portion is defined between the web and the secondary beam and an outer flange portion is defined extending outwardly from the secondary beam;

d) each secondary beam is located at an outer edge of the flange;

e) each diaphragm terminates at a respective secondary beam; and,

f) each secondary beam has a cross section profile of one of:

i) a square shape;

ii) a rectangular shape;

iii) a triangular shape;

iv) a rounded shape; and,

v) a semi-circular shape.

7. A beam according to claim 1 , wherein the structure engaging surface is at least one of:

a) a substantially planar surface; and,

b) configured to engage a slab.

8. A beam according to claim 1 , wherein at least one of the diaphragms includes a service hole for allowing services to be routed through the diaphragm.

9. A beam according to claim 1 , wherein the flanges extend laterally from the web at an angle to define a sloped structure engaging surface.

10. A beam according to claim 1 , wherein the beam includes laterally extending internal reinforcements at least at longitudinal positions coinciding with the diaphragms.

11. A beam according to claim 1 , wherein the beam includes diagonal beams extending between adjacent diaphragms, and wherein the diagonal beams extend from a base of a first diaphragm to an end of a second diaphragm adjacent to the first diaphragm.

12. A beam according to claim 1 , wherein the beam includes an integral slab portion formed integrally with the flanges, the integral slab portion defining a substantially planar slab surface of the beam.

13. A beam according to claim 12 , wherein at least one of:

a) the slab surface is sloped relative to the web;

b) the integral slab portion is formed at least in part from thickened regions of the flanges;

c) the integral slab portion is formed such that the slab surface is aligned with a lateral extension direction of the flanges relative to the web; and,

d) the web is substantially symmetrical about a longitudinally extending symmetry plane and the flanges extend laterally from the web at an angle relative to the symmetry plane, such that the slab surface is sloped relative to the symmetry plane.

14. A beam according to claim 12 , wherein the beam includes a recessed region formed along an outer edge of the integral slab portion, to thereby allow adjacent beams to be joined by abutting respective outer edges of the adjacent beams so that the respective recessed regions form an effective joint recess and forming a concrete infill in the effective joint recess.

15. A beam according to claim 14 , wherein the beam includes reinforcement members embedded into the flanges and protruding into the recessed regions, such that the concrete infill is reinforced by the reinforcement members when adjacent beams are joined.

16. A beam according to claim 14 , wherein the beam includes reinforcement couplers embedded into the integral slab portion for supporting reinforcement bars protruding laterally across the recessed regions, such that the concrete infill is reinforced by the reinforcement bars when adjacent beams are joined.

17. A beam according to claim 16 , wherein the reinforcement bars extend laterally beyond an outer edge of the beam to thereby protrude into an adjacent recessed region when adjacent beams are joined.

18. A beam according to claim 1 , wherein the beam is used in construction of a long span vehicle bridge structure.

19. A long span vehicle bridge structure including a plurality of beams according to claim 1 .