CA1259813A - Composite, pre-stressed structural member and method of forming same - Google Patents
Composite, pre-stressed structural member and method of forming sameInfo
- Publication number
- CA1259813A CA1259813A CA000491171A CA491171A CA1259813A CA 1259813 A CA1259813 A CA 1259813A CA 000491171 A CA000491171 A CA 000491171A CA 491171 A CA491171 A CA 491171A CA 1259813 A CA1259813 A CA 1259813A
- Authority
- CA
- Canada
- Prior art keywords
- support member
- mold
- composite
- flange
- beams
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C3/00—Structural elongated elements designed for load-supporting
- E04C3/02—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces
- E04C3/29—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces built-up from parts of different material, i.e. composite structures
- E04C3/293—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces built-up from parts of different material, i.e. composite structures the materials being steel and concrete
- E04C3/294—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces built-up from parts of different material, i.e. composite structures the materials being steel and concrete of concrete combined with a girder-like structure extending laterally outside the element
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28B19/00—Machines or methods for applying the material to surfaces to form a permanent layer thereon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
- B28B23/00—Arrangements specially adapted for the production of shaped articles with elements wholly or partly embedded in the moulding material; Production of reinforced objects
- B28B23/02—Arrangements specially adapted for the production of shaped articles with elements wholly or partly embedded in the moulding material; Production of reinforced objects wherein the elements are reinforcing members
- B28B23/04—Arrangements specially adapted for the production of shaped articles with elements wholly or partly embedded in the moulding material; Production of reinforced objects wherein the elements are reinforcing members the elements being stressed
- B28B23/06—Arrangements specially adapted for the production of shaped articles with elements wholly or partly embedded in the moulding material; Production of reinforced objects wherein the elements are reinforcing members the elements being stressed for the production of elongated articles
-
- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
- E04B5/00—Floors; Floor construction with regard to insulation; Connections specially adapted therefor
- E04B5/16—Load-carrying floor structures wholly or partly cast or similarly formed in situ
- E04B5/17—Floor structures partly formed in situ
- E04B5/23—Floor structures partly formed in situ with stiffening ribs or other beam-like formations wholly or partly prefabricated
- E04B5/29—Floor structures partly formed in situ with stiffening ribs or other beam-like formations wholly or partly prefabricated the prefabricated parts of the beams consisting wholly of metal
Abstract
ABSTRACT
An improved composite, pre-stressed structural member and method of forming such a member of the type provided by upside down forming which includes connecting the steel beams of the composite member to the upper side of a mold so that a parallel deflection of the mold and beams occurs as the mold is filled with concrete. The improvement comprises utilizing a steel beam having a flange at or near the neutral axis with respect to a vertical deflection of the support member. After the composite structure is formed, the flange is away from the neutral axis with respect to a vertical deflection of the composite structure. This flange, therefore, significantly increases the section modu-lus of the composite structure while not adding signifi-cantly to the resistance to bending of the beam during pre-stressing. Stacked and welded I-beams are an example of a support in accordance with this invention.
An improved composite, pre-stressed structural member and method of forming such a member of the type provided by upside down forming which includes connecting the steel beams of the composite member to the upper side of a mold so that a parallel deflection of the mold and beams occurs as the mold is filled with concrete. The improvement comprises utilizing a steel beam having a flange at or near the neutral axis with respect to a vertical deflection of the support member. After the composite structure is formed, the flange is away from the neutral axis with respect to a vertical deflection of the composite structure. This flange, therefore, significantly increases the section modu-lus of the composite structure while not adding signifi-cantly to the resistance to bending of the beam during pre-stressing. Stacked and welded I-beams are an example of a support in accordance with this invention.
Description
1~5~13 IMPROVED COMPOSITE, PRE-STRESSED STRUCTURAL MEMBER
AND METHOD OF FORMING SAME
Backqround of the Invention 1. Field of the Invention This invention relates in general to structural members and methods of forming structural members. More particularly, but not by way of limitation, it relates to composite, pre-stressed structural members and methods and apparatus for forming, designing, and pre-stressing such structural members.
AND METHOD OF FORMING SAME
Backqround of the Invention 1. Field of the Invention This invention relates in general to structural members and methods of forming structural members. More particularly, but not by way of limitation, it relates to composite, pre-stressed structural members and methods and apparatus for forming, designing, and pre-stressing such structural members.
2. Description of the Prior Art In the field of constructing composite, pre-stressed structural members, many methods of pre-stressing are available. A particularly desirable method of pre-stressing such composite structural members is shown in U.S. Patent No. 4,493,177 and U.S. Patent No. 4,700,516. The pre-stressing disclosed in this patent and patent application is achieved by forming the composite structure upside down.
The upside down forming includes connecting the steel beams of the composite member to the upper side of a mold so that shear connectors extend downwardly into the mold. The steel beams and the mold are joined and supported so that deflection of the mold causes a parallel deflection of the steel beams. As the mold is filled with concrete, the steel beams and mold deflect downwardly from the weight of the beams, mold and concrete, thus pre-stressing the beams.
The top flange of the inverted beams (bottom flange when upright) receives a compression pre stress. After the concrete hardens, the mold is removed and the connected beams and concrete slab . . . . .
98~3 are inverted so that the composite structure is upright. In the upright position the bottom flange of the beams receives a tension stress which is reduced by the compression pre-stress achieved by the inverted molding. The concrete, of course, receives a compression stress.
This type of pre-stressing is especially desirable because it produces an improved pre-stress resulting from the pouring of the concrete itself. No separate pre-stress activity is required. In addition, because the uppermost or surface concrete is the concrete formed at the bottom of the mold, the concrete surface is less permeable and harder than concrete structures which are not inverted. Still further, this type of pre-stressing results in a pre-stress rela-tionship based upon the weight distribution of the concrete and beam combination. This pre-stress relationship is much improved compared to pre-stressing resulting from jacks which concentrates more of the pre-stressing at a single point.
Despite the great improvements over the structures and methods of the prior art, my method and apparatus can be further improved by the invention described herein.
Particularly, the present invention provides improved strength and resistance to bending with less cost.
Summary of the Invention The present invention provides an improved composite, pre-stressed structural member and method of forming the same. The structure includes a concrete slab supported by a metal support member and connected to the support member by shear connectors. The method of forming the composite structure and pre-stressing the support member comprises an ~.S~38~L3 inverted parallel deflection of the slab mold and support member as described in my U.S. Patent No. 4,493,177. The improvement in the method and structure result from the sup-port member having a flange at or near the neutral axis with respect to a vertical deflection of the inverted support member. Thus, as the support member is deflected in the inverted position, this flange, at or near the neutral axis, does not add significantly to the resistance to bending.
However, after the concrete is hardened and the composite, pre-stressed structural member is placed upright, the neutral axis of the composite structure is near the top of the support member and away from this flange. The flange, therefore, increases the section modulus of the upright com-posite structure while not producing a significant resistance to bending in the formation process.
A particularly desirable lower support member includes first and second beams which have first and second flanges, respectively, which together form the flange near the neutral axis of the inverted support member. For example, two I-beams can be stacked and their flanges welded together to form the support member. Often the cost per pound of the smaller beams is less than the cost per pound of the larger beams reducing the cost even further than simply the savings produced by reducing the amount of steel.
For a further understanding of the invention, and further objects, features and advantages thereof, reference may now be had to the following description taken in con-junction with the accompanying drawings.
Brief Description of the Drawings FIG. 1 is a perspective view of a portion of two stacked 1;~5'3~3 and joined beams in accordance with the present invention;
FIG. 2 is a cross-sectional view of a composite, pre-stressed structural member being formed in accordance with the method and apparatus of the present invention;
FIG. 3 is a schematic side elevational view of the structural member of the present invention during one of the formation steps;
FIG. 4 is a schematic side elevational view of a struc-tural member of the present invention ready for use; and FIG. 5 is an end view of a structural member constructed in accordance with the present invention.
Description of the Preferred Embodiments The method and apparatus of the present invention are especially suited for use in connection with the method and apparatus described in U.S. Patent No. 4,493,177 and U.S.
Patent No. 4,700,516. For a further understanding of this invention, reference should be made to the descriptions in these patents.
Referring now to FIG. 1, the present invention provides a support for a composite, pre-stressed structural member which comprises stacked steel I-beams 11 and 13. The upper beam 11 is welded at its lower flange 15 to the upper flange 17 of the lower beam 13. If, as shown in FIG. 1, the I-beams 11 and 13 are of sufficiently different size, a welding surface 19 is provided on the larger flange. A con-tinuous weld 21 (or spotwelds at regular intervals) along the welding surface 19 is necessary in order to completely secure the I-beams 11 and 13 with respect to each other.
.~, ~, 1~i9813 Referring now to FIG. 2, once the stacked beams 11 and 13 have been joined, they are inverted and placed in a molding apparatus 23. The molding apparatus includes a mold bottom 25 and mold sides 27 which form the mold into which the concrete is to be poured. Spacers 29 support the beams 11 and 13 at the ends of the mold so that the beams have a proper height with respect to the bottom surface 25 of the mold. The spacers are also part of the end support system.
Shear connectors 47 extend downwardly into the mold from flange 30 of beam 11.
A connection assembly including upper cross beams 31 and lower cross beams 33 joined by connection rods 35 connect the beams 11 and 13 to the mold. The connection assemblies are spaced along the beams 11 and 13 and the mold so that deflection of the mold causes a parallel deflection of the beams 11 and 13. Nuts 37 are threaded to opposite ends of the rods 35 to adjustably join the upper cross beam 31 to the lower cross beam 33. The entire connected mold and cross beams are sùpported at opposite ends by end supports 39.
Referring now to FIG. 3, following the preparation of the connected mold and beams, concrete is poured into the mold causing the beams 11 and 13 and the mold to deflect downwardly between the supports 39. As the beams 11 and 13 deflect downwardly due to the weight of the beam, the mold and the wet concrete, the neutral axis A-A of the inverted deflected beams is at or near the joined middle flanges 15 and 17.
After the concrete has been poured into the mold causing deflection of the beams and mold, the concrete is allowed to :1~5'-~8~
harden into a concrete slab 41. The concrete slab 41 is fixed to the beams 11 and 13 by the shear connectors 47 which extend from the flange 30 of beam 11 into the concrete slab 41. Following hardening of the concrete slab 41, the mold is removed from the concrete and the composite slab and beams are turned upright as shown in FIG. 4. When in use, this composite structural member will be supported at its ends 43 and 45. Considering the composite structure sup-ported at its ends, the bending moment of live and dead loads on the composite member causes a downward deflection of the composite member. The neutral axis B-B of the com-posite structure with respect to a vertical deflection is at or near the upper flange 30 of beam 11. With the neutral axis B-B near the flange 30, the flanges 15 and 17 are suf-ficiently below the neutral axis to greatly increase the section modulus of the composite structure compared to a composite structure supported by appropriately designed single I-beams. This provides a much improved resistance to bending of the composite, pre-stressed structural member.
The advantage of the stacked beams 11 and 13 in the method and apparatus described herein is that a high section modulus in the combined structural member is obtained while retaining a low section modulus in the beams 11 and 13 as the concrete is poured to form slab 41. This allows less steel to be used while obtaining the same or a higher sec-tion modulus. Further, because the cost of the combined, smaller beams is often less than the cost of a single beam of the same weight, the cost reduction is even more than the savings in steel.
Referring now to FIG. 5, an end view of the composite :1~5981~
structure is shown including haunches 45 in the concrete slab 41 providing a neutral axis of the composite member farther from the flanges 15 and 17 of the bea~s 11 and 13.
The haunches 45 can be formed by pouring the concrete in two steps. First, the concrete is poured to a desired slab level in the mold and allowed to sufficiently harden so as to support a second pour. New forms are placed on either side of the shear connectors 47 to form the mold space for the haunches 45. The haunches 45 are then poured up to the height of the flange 30 of beam 11. The shear connectors 47 extend into the first pour through the haunches 45.
While the above embodiments show stacked and welded I-beams, many beams or combinations of beams having a flange near the neutral axis of the beam or beams can achieve the desired result of a low section modulus as the beams are pre-stressed and a high section modulus in the composite structure. For example, T-shaped beams could be welded to a middle plate (the neutral axis flange) to achieve a custom-designed ratio of beam section modulus to composite struc-ture section modulus.
Examples The following calculations detail the design of two com-posite structures having a 60 foot span with a slab 10.67 feet wide and 7 inches thick. Example 1 is supported by two single cover plated I-beams (W24x55) and Example 2 is sup-ported by two stacked I-beams (W14x22, top and W18x35, bottom). The two structures are pre-stressed and formed as described above, except Example 1 uses single beams without flanges at the neutral axis.
125~38~3 List of Symbols:
I = Moment of inertia (in.3) fb~ ft = Calculated stress in bottom or top flange underload (PSI) (C) = Compressive Stress (PSI) (T) = Tensile Stress (PSI) LL = Live Load N = Ratio of modulus of elasticity of steel to modulus of elasticity of concrete (7 for short term live loads and 21 for long term dead loads.
fc = Calculated stress of concrete (PSI) M = Moment (Ft-Lb) Example 1:
1. Neutral Axis of Steel =10.40 IN
2. Weight of one Girder =65.20 LBS/FT
The upside down forming includes connecting the steel beams of the composite member to the upper side of a mold so that shear connectors extend downwardly into the mold. The steel beams and the mold are joined and supported so that deflection of the mold causes a parallel deflection of the steel beams. As the mold is filled with concrete, the steel beams and mold deflect downwardly from the weight of the beams, mold and concrete, thus pre-stressing the beams.
The top flange of the inverted beams (bottom flange when upright) receives a compression pre stress. After the concrete hardens, the mold is removed and the connected beams and concrete slab . . . . .
98~3 are inverted so that the composite structure is upright. In the upright position the bottom flange of the beams receives a tension stress which is reduced by the compression pre-stress achieved by the inverted molding. The concrete, of course, receives a compression stress.
This type of pre-stressing is especially desirable because it produces an improved pre-stress resulting from the pouring of the concrete itself. No separate pre-stress activity is required. In addition, because the uppermost or surface concrete is the concrete formed at the bottom of the mold, the concrete surface is less permeable and harder than concrete structures which are not inverted. Still further, this type of pre-stressing results in a pre-stress rela-tionship based upon the weight distribution of the concrete and beam combination. This pre-stress relationship is much improved compared to pre-stressing resulting from jacks which concentrates more of the pre-stressing at a single point.
Despite the great improvements over the structures and methods of the prior art, my method and apparatus can be further improved by the invention described herein.
Particularly, the present invention provides improved strength and resistance to bending with less cost.
Summary of the Invention The present invention provides an improved composite, pre-stressed structural member and method of forming the same. The structure includes a concrete slab supported by a metal support member and connected to the support member by shear connectors. The method of forming the composite structure and pre-stressing the support member comprises an ~.S~38~L3 inverted parallel deflection of the slab mold and support member as described in my U.S. Patent No. 4,493,177. The improvement in the method and structure result from the sup-port member having a flange at or near the neutral axis with respect to a vertical deflection of the inverted support member. Thus, as the support member is deflected in the inverted position, this flange, at or near the neutral axis, does not add significantly to the resistance to bending.
However, after the concrete is hardened and the composite, pre-stressed structural member is placed upright, the neutral axis of the composite structure is near the top of the support member and away from this flange. The flange, therefore, increases the section modulus of the upright com-posite structure while not producing a significant resistance to bending in the formation process.
A particularly desirable lower support member includes first and second beams which have first and second flanges, respectively, which together form the flange near the neutral axis of the inverted support member. For example, two I-beams can be stacked and their flanges welded together to form the support member. Often the cost per pound of the smaller beams is less than the cost per pound of the larger beams reducing the cost even further than simply the savings produced by reducing the amount of steel.
For a further understanding of the invention, and further objects, features and advantages thereof, reference may now be had to the following description taken in con-junction with the accompanying drawings.
Brief Description of the Drawings FIG. 1 is a perspective view of a portion of two stacked 1;~5'3~3 and joined beams in accordance with the present invention;
FIG. 2 is a cross-sectional view of a composite, pre-stressed structural member being formed in accordance with the method and apparatus of the present invention;
FIG. 3 is a schematic side elevational view of the structural member of the present invention during one of the formation steps;
FIG. 4 is a schematic side elevational view of a struc-tural member of the present invention ready for use; and FIG. 5 is an end view of a structural member constructed in accordance with the present invention.
Description of the Preferred Embodiments The method and apparatus of the present invention are especially suited for use in connection with the method and apparatus described in U.S. Patent No. 4,493,177 and U.S.
Patent No. 4,700,516. For a further understanding of this invention, reference should be made to the descriptions in these patents.
Referring now to FIG. 1, the present invention provides a support for a composite, pre-stressed structural member which comprises stacked steel I-beams 11 and 13. The upper beam 11 is welded at its lower flange 15 to the upper flange 17 of the lower beam 13. If, as shown in FIG. 1, the I-beams 11 and 13 are of sufficiently different size, a welding surface 19 is provided on the larger flange. A con-tinuous weld 21 (or spotwelds at regular intervals) along the welding surface 19 is necessary in order to completely secure the I-beams 11 and 13 with respect to each other.
.~, ~, 1~i9813 Referring now to FIG. 2, once the stacked beams 11 and 13 have been joined, they are inverted and placed in a molding apparatus 23. The molding apparatus includes a mold bottom 25 and mold sides 27 which form the mold into which the concrete is to be poured. Spacers 29 support the beams 11 and 13 at the ends of the mold so that the beams have a proper height with respect to the bottom surface 25 of the mold. The spacers are also part of the end support system.
Shear connectors 47 extend downwardly into the mold from flange 30 of beam 11.
A connection assembly including upper cross beams 31 and lower cross beams 33 joined by connection rods 35 connect the beams 11 and 13 to the mold. The connection assemblies are spaced along the beams 11 and 13 and the mold so that deflection of the mold causes a parallel deflection of the beams 11 and 13. Nuts 37 are threaded to opposite ends of the rods 35 to adjustably join the upper cross beam 31 to the lower cross beam 33. The entire connected mold and cross beams are sùpported at opposite ends by end supports 39.
Referring now to FIG. 3, following the preparation of the connected mold and beams, concrete is poured into the mold causing the beams 11 and 13 and the mold to deflect downwardly between the supports 39. As the beams 11 and 13 deflect downwardly due to the weight of the beam, the mold and the wet concrete, the neutral axis A-A of the inverted deflected beams is at or near the joined middle flanges 15 and 17.
After the concrete has been poured into the mold causing deflection of the beams and mold, the concrete is allowed to :1~5'-~8~
harden into a concrete slab 41. The concrete slab 41 is fixed to the beams 11 and 13 by the shear connectors 47 which extend from the flange 30 of beam 11 into the concrete slab 41. Following hardening of the concrete slab 41, the mold is removed from the concrete and the composite slab and beams are turned upright as shown in FIG. 4. When in use, this composite structural member will be supported at its ends 43 and 45. Considering the composite structure sup-ported at its ends, the bending moment of live and dead loads on the composite member causes a downward deflection of the composite member. The neutral axis B-B of the com-posite structure with respect to a vertical deflection is at or near the upper flange 30 of beam 11. With the neutral axis B-B near the flange 30, the flanges 15 and 17 are suf-ficiently below the neutral axis to greatly increase the section modulus of the composite structure compared to a composite structure supported by appropriately designed single I-beams. This provides a much improved resistance to bending of the composite, pre-stressed structural member.
The advantage of the stacked beams 11 and 13 in the method and apparatus described herein is that a high section modulus in the combined structural member is obtained while retaining a low section modulus in the beams 11 and 13 as the concrete is poured to form slab 41. This allows less steel to be used while obtaining the same or a higher sec-tion modulus. Further, because the cost of the combined, smaller beams is often less than the cost of a single beam of the same weight, the cost reduction is even more than the savings in steel.
Referring now to FIG. 5, an end view of the composite :1~5981~
structure is shown including haunches 45 in the concrete slab 41 providing a neutral axis of the composite member farther from the flanges 15 and 17 of the bea~s 11 and 13.
The haunches 45 can be formed by pouring the concrete in two steps. First, the concrete is poured to a desired slab level in the mold and allowed to sufficiently harden so as to support a second pour. New forms are placed on either side of the shear connectors 47 to form the mold space for the haunches 45. The haunches 45 are then poured up to the height of the flange 30 of beam 11. The shear connectors 47 extend into the first pour through the haunches 45.
While the above embodiments show stacked and welded I-beams, many beams or combinations of beams having a flange near the neutral axis of the beam or beams can achieve the desired result of a low section modulus as the beams are pre-stressed and a high section modulus in the composite structure. For example, T-shaped beams could be welded to a middle plate (the neutral axis flange) to achieve a custom-designed ratio of beam section modulus to composite struc-ture section modulus.
Examples The following calculations detail the design of two com-posite structures having a 60 foot span with a slab 10.67 feet wide and 7 inches thick. Example 1 is supported by two single cover plated I-beams (W24x55) and Example 2 is sup-ported by two stacked I-beams (W14x22, top and W18x35, bottom). The two structures are pre-stressed and formed as described above, except Example 1 uses single beams without flanges at the neutral axis.
125~38~3 List of Symbols:
I = Moment of inertia (in.3) fb~ ft = Calculated stress in bottom or top flange underload (PSI) (C) = Compressive Stress (PSI) (T) = Tensile Stress (PSI) LL = Live Load N = Ratio of modulus of elasticity of steel to modulus of elasticity of concrete (7 for short term live loads and 21 for long term dead loads.
fc = Calculated stress of concrete (PSI) M = Moment (Ft-Lb) Example 1:
1. Neutral Axis of Steel =10.40 IN
2. Weight of one Girder =65.20 LBS/FT
3. Moment of Inertia of one Girder = 1716.32 IN-4
4. Sect. Mod. - Top of one Girder = 125.57 IN-3
5. Sect. Mod. - Bottom of one Girder = 165.00 IN-3
6. The Concrete Strength = 5000. PSI
7. Top Reinf. Steel in slab = 15 Number 4 Bars
8. Bottom Reinf. Steel in slab = 8 Number 4 Bars
9. The Value of N is: 7.
10. Neutral Axis Location: 23.70 IN
11. I - Composite Section: 12710.01 IN-4
12. Section Modulus - Conc: 1723.94 IN-3
13. Sect. Mod. - Top Flange: 34107.49 IN-3
14. Section Modulus - Bottom: 536.35 IN-3
15. The Value of N is: 21.
16. Neutral Axis Location: 19.93 IN
17. I - Composite Section: 9859.51 IN-4
18. Section Modulus - Conc: 885.16 IN-3
19. Sect. Mod. - Top Flange: 2382.29 IN-3
20. Section Modulus - Bottom: 494.67 IN-3
21. Prestress fb = =19.71(C) ft = =25.89(T)
22. Turnover fb = =24.18(T) Overlay fb = =2.25(T) (LL+I) fb = =21.75(T) fb =28.47(T) 27KSI
12~98:13
12~98:13
23. 1.47 M = (Extra required pre-stress moment)
24. ft = 25.89 +
= 25.89 + 5.80 - 6.10 - 0.34 ft = 25.25(T) 27KSI
= 25.89 + 5.80 - 6.10 - 0.34 ft = 25.25(T) 27KSI
25. Turnover fc = = 0.781(C) + Overlay + Pre-stress (LL+I) fb = = 0.967(C) fc = 1.748(C) 2.0KSI
Example 2:
1. Neutral Axis of Steel = 14.92 IN
2. Weight of one Girder = 57.00 LBS/FT
3. Moment of Inertia of one Girder = 1689.98 IN-4 4. Sect. Mod. - Top of one Girder = 102.28 IN-3 5. Sect. Mod. - Bottom of one Girder = 113.29 IN-3 6. The Concrete Strength= 5000. PSI
7. Top Steel = 15 Number 4 Bars 8. Bottom Steel = 8 Number 4 Bars 9. The Value of N is: 7.
10. Neutral Axis Location: 30.88 IN
11. I - Composite Section: 14615.64 IN-4 12. Section Modulus - Conc: 1933.54 IN-3 13. Sect. Mod. - Top Flange:26146.51 IN-3 14. Section Modulus - Bottom:473.29 IN-3 15. The Value of N is: 21.
16. Neutral Axis Location: 26.66 IN
17. I - Composite Section:11422.92 IN-4 18. Section Modulus - Conc: 969.97 IN-3 19. Sect. Mod. - Top Flange:2391.44 IN-3 20. Section Modulus - Bottom:428.41 IN-3 ~Z5~ 3 21. Prestress fb = = 28.70(C) ft = - 31.79(T) 22. Turnover fb = = 27.92(T) Overlay fb = = 2.60(T) (LL+I) fb = = 24.65(T) fb = 26.47(T) 27KSI
23. Turnover ft = = 5.47(C) + Overlay (LL+I) ft = = 0.45(C) ft = 25.87(T) 27KSI
24. Turnover fc = = 0.642(C) + Overlay (LL+I) fb = 0.862(C) fc = 1.504(C) 2.0KSI
Both of the above designs are acceptable resulting in very similar final stresses. However, the stacked beam example is clearly superior because it uses less steel, requires no added pre-stress momen, has a lower concrete stress, and will deflect less. One way of determining the superiority of the stacked beam example versus the cover plated rolled beam (I-beam) example is to compare the ratio of composite to non-composite section modulii.
The example 1 section modulus ratio is 536.35 2 x 165 = 1.63 while the example 2 section modulus ratio is 1259~3~3 473.~9 2x113.29 = 2.09 Thus, the composite, pre-stressed structural member of the present invention and the method and apparatus for forming the structural member are well adapted to attain the objects and advantages mentioned as well as those inherent therein. While presently preferred embodiments of the invention have been described for the purpose of this disclosure, numerous changes in the construction and arrangement of parts and in the steps of the method can be made by those skilled in the art, which changes are encom-passed within the spirit of this invention is defined by the appended claims.
The foregoing disclosure and the showings made in the drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense.
Example 2:
1. Neutral Axis of Steel = 14.92 IN
2. Weight of one Girder = 57.00 LBS/FT
3. Moment of Inertia of one Girder = 1689.98 IN-4 4. Sect. Mod. - Top of one Girder = 102.28 IN-3 5. Sect. Mod. - Bottom of one Girder = 113.29 IN-3 6. The Concrete Strength= 5000. PSI
7. Top Steel = 15 Number 4 Bars 8. Bottom Steel = 8 Number 4 Bars 9. The Value of N is: 7.
10. Neutral Axis Location: 30.88 IN
11. I - Composite Section: 14615.64 IN-4 12. Section Modulus - Conc: 1933.54 IN-3 13. Sect. Mod. - Top Flange:26146.51 IN-3 14. Section Modulus - Bottom:473.29 IN-3 15. The Value of N is: 21.
16. Neutral Axis Location: 26.66 IN
17. I - Composite Section:11422.92 IN-4 18. Section Modulus - Conc: 969.97 IN-3 19. Sect. Mod. - Top Flange:2391.44 IN-3 20. Section Modulus - Bottom:428.41 IN-3 ~Z5~ 3 21. Prestress fb = = 28.70(C) ft = - 31.79(T) 22. Turnover fb = = 27.92(T) Overlay fb = = 2.60(T) (LL+I) fb = = 24.65(T) fb = 26.47(T) 27KSI
23. Turnover ft = = 5.47(C) + Overlay (LL+I) ft = = 0.45(C) ft = 25.87(T) 27KSI
24. Turnover fc = = 0.642(C) + Overlay (LL+I) fb = 0.862(C) fc = 1.504(C) 2.0KSI
Both of the above designs are acceptable resulting in very similar final stresses. However, the stacked beam example is clearly superior because it uses less steel, requires no added pre-stress momen, has a lower concrete stress, and will deflect less. One way of determining the superiority of the stacked beam example versus the cover plated rolled beam (I-beam) example is to compare the ratio of composite to non-composite section modulii.
The example 1 section modulus ratio is 536.35 2 x 165 = 1.63 while the example 2 section modulus ratio is 1259~3~3 473.~9 2x113.29 = 2.09 Thus, the composite, pre-stressed structural member of the present invention and the method and apparatus for forming the structural member are well adapted to attain the objects and advantages mentioned as well as those inherent therein. While presently preferred embodiments of the invention have been described for the purpose of this disclosure, numerous changes in the construction and arrangement of parts and in the steps of the method can be made by those skilled in the art, which changes are encom-passed within the spirit of this invention is defined by the appended claims.
The foregoing disclosure and the showings made in the drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense.
Claims (9)
1. An improved composite, pre-stressed structure of the type including with the structure in upright condition, a molded upper concrete slab supported by a lower metal support member extending beneath and connected by shear connection means to said molded upper concrete slab, said metal support member having been joined with said slab and pre-stressed by connecting the support member to the upper side of a mold so that deflection of the mold causes an approximately parallel deflection of the support member, with the mold and support member being supported so that deflection of the mold and support member can occur, and the concrete slab having been formed by filling the mold with concrete which deflects the mold and support member so that the support member is pre-stressed by the deflection; the improvement comprising:
the support member having a flange at or near the neutral axis with respect to a vertical deflection of the support member in inverted condition and away from the neutral axis with respect to a vertical deflection of the composite structure in the upright condition, for increasing the resistance to bending of the composite structure in the upright condition.
the support member having a flange at or near the neutral axis with respect to a vertical deflection of the support member in inverted condition and away from the neutral axis with respect to a vertical deflection of the composite structure in the upright condition, for increasing the resistance to bending of the composite structure in the upright condition.
2. The composite structure of claim 1 wherein said support member comprises:
first and second beams stacked and joined at said flange.
first and second beams stacked and joined at said flange.
3. The composite structure of claim 2 wherein said first and second beams have first and second flanges, respectively, which together, form said flange.
4. The composite structure of claim 3 wherein said first and second flanges are welded together to form said flange.
5. A method of forming a composite, pre-stressed structural member of the type having an upper molded surface supported by a lower support member comprising:
connecting a lower support member having a flange at or near the neutral axis with respect to a vertical deflection of the support member to the upper side of a mold so that deflection of the mold causes deflection of the support member and such that support member connector means extend downwardly into said mold;
supporting the mold and lower support member so that deflection of the mold and lower support member can occur;
filling the mold with a moldable material which hardens to form a composite structural member with said lower support member;
deflecting the mold during hardening of the moldable material such that the support member is placed in a pre-stressed condition to form a composite, pre-stressed structural member upon hardening of the moldable material; and after hardening of the moldable material, inverting the composite, pre-stressed structural member such that the lower support member is beneath and supports the hardened moldable material and such that the composite, pre-stressed structural member has a neutral axis with respect to vertical deflection which is above said flange.
connecting a lower support member having a flange at or near the neutral axis with respect to a vertical deflection of the support member to the upper side of a mold so that deflection of the mold causes deflection of the support member and such that support member connector means extend downwardly into said mold;
supporting the mold and lower support member so that deflection of the mold and lower support member can occur;
filling the mold with a moldable material which hardens to form a composite structural member with said lower support member;
deflecting the mold during hardening of the moldable material such that the support member is placed in a pre-stressed condition to form a composite, pre-stressed structural member upon hardening of the moldable material; and after hardening of the moldable material, inverting the composite, pre-stressed structural member such that the lower support member is beneath and supports the hardened moldable material and such that the composite, pre-stressed structural member has a neutral axis with respect to vertical deflection which is above said flange.
6. The method of claim 5 wherein said moldable material comprises concrete.
7. The method of claim 6 wherein said lower support member comprises a steel beam.
8. The method of claim 5 wherein said lower support member comprises first and second steel beams joined at said flange.
9. The method of claim 8 wherein said first and second steel beams have first and second flanges, respectively, which are joined to form said flange.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US719,339 | 1985-04-03 | ||
| US06/719,339 US4646493A (en) | 1985-04-03 | 1985-04-03 | Composite pre-stressed structural member and method of forming same |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1259813A true CA1259813A (en) | 1989-09-26 |
Family
ID=24889684
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000491171A Expired CA1259813A (en) | 1985-04-03 | 1985-09-20 | Composite, pre-stressed structural member and method of forming same |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4646493A (en) |
| EP (1) | EP0198600B1 (en) |
| JP (1) | JPS61274907A (en) |
| CN (1) | CN1007917B (en) |
| AT (1) | ATE50528T1 (en) |
| AU (1) | AU5504986A (en) |
| BR (1) | BR8601492A (en) |
| CA (1) | CA1259813A (en) |
| DE (1) | DE3669124D1 (en) |
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|---|---|---|---|---|
| US4785600A (en) * | 1988-02-16 | 1988-11-22 | Ting Raymond M L | Buildup composite beam structure |
| US5152112A (en) * | 1990-07-26 | 1992-10-06 | Iota Construction Ltd. | Composite girder construction and method of making same |
| US5144710A (en) * | 1991-02-28 | 1992-09-08 | Grossman Stanley J | Composite, prestressed structural member and method of forming same |
| DE69420001T2 (en) * | 1993-04-01 | 2000-03-23 | Dae Nung Ind Co Ltd | METHOD FOR PRODUCING A PRELOADED COMPOSITE BEAM STRUCTURE |
| US5617599A (en) * | 1995-05-19 | 1997-04-08 | Fomico International | Bridge deck panel installation system and method |
| US6416693B1 (en) | 1996-07-01 | 2002-07-09 | William D. Lockwood | Method of strengthening an existing reinforced concrete member |
| US5894003A (en) * | 1996-07-01 | 1999-04-13 | Lockwood; William D. | Method of strengthening an existing reinforced concrete member |
| US5978997A (en) * | 1997-07-22 | 1999-11-09 | Grossman; Stanley J. | Composite structural member with thin deck portion and method of fabricating the same |
| US6588160B1 (en) | 1999-08-20 | 2003-07-08 | Stanley J. Grossman | Composite structural member with pre-compression assembly |
| US6857156B1 (en) | 2000-04-05 | 2005-02-22 | Stanley J. Grossman | Modular bridge structure construction and repair system |
| KR100427405B1 (en) * | 2001-03-07 | 2004-04-17 | 박재만 | Pssc complex girder |
| US20030093961A1 (en) * | 2001-11-21 | 2003-05-22 | Grossman Stanley J. | Composite structural member with longitudinal structural haunch |
| US7370452B2 (en) * | 2002-09-16 | 2008-05-13 | Rogers Melissa B | Mat assembly for heavy equipment transit and support |
| US7930866B2 (en) * | 2004-08-02 | 2011-04-26 | Tac Technologies, Llc | Engineered structural members and methods for constructing same |
| US8266856B2 (en) | 2004-08-02 | 2012-09-18 | Tac Technologies, Llc | Reinforced structural member and frame structures |
| US7721496B2 (en) * | 2004-08-02 | 2010-05-25 | Tac Technologies, Llc | Composite decking material and methods associated with the same |
| US8065848B2 (en) | 2007-09-18 | 2011-11-29 | Tac Technologies, Llc | Structural member |
| US7213379B2 (en) * | 2004-08-02 | 2007-05-08 | Tac Technologies, Llc | Engineered structural members and methods for constructing same |
| US7600283B2 (en) * | 2005-01-21 | 2009-10-13 | Tricon Engineering Group, Ltd. | Prefabricated, prestressed bridge system and method of making same |
| US8161691B2 (en) * | 2008-05-14 | 2012-04-24 | Plattforms, Inc. | Precast composite structural floor system |
| US8297017B2 (en) | 2008-05-14 | 2012-10-30 | Plattforms, Inc. | Precast composite structural floor system |
| US8381485B2 (en) | 2010-05-04 | 2013-02-26 | Plattforms, Inc. | Precast composite structural floor system |
| US8453406B2 (en) | 2010-05-04 | 2013-06-04 | Plattforms, Inc. | Precast composite structural girder and floor system |
| US20120090254A1 (en) * | 2010-10-14 | 2012-04-19 | Mr. Venkata Rangarao Vemuri | Method of forming flat strip stepped slab floor system of reinforced concrete |
| CN103128851B (en) * | 2013-03-06 | 2015-03-25 | 中铁二十五局集团建筑安装工程有限公司 | Manufacturing method of nonstandard T-shaped beam suitable for different spans |
| CN103273567B (en) * | 2013-06-06 | 2015-04-22 | 浙江金筑交通建设有限公司 | Movable steel pedestal with adjustable jacking and construction method thereof |
| US10895047B2 (en) | 2016-11-16 | 2021-01-19 | Valmont Industries, Inc. | Prefabricated, prestressed bridge module |
| CN108943359B (en) * | 2018-08-20 | 2020-07-24 | 西平县华鼎电气装备有限责任公司 | Production method of concrete pole |
| CN109537787B (en) * | 2018-12-28 | 2024-02-13 | 上海建工五建集团有限公司 | Assembled prestress large plate reverse camber self-adjusting system and using method thereof |
| US10718094B1 (en) * | 2019-02-12 | 2020-07-21 | Valmont Industries, Inc. | Tub girders and related manufacturing methods |
| CN116787012A (en) * | 2023-06-27 | 2023-09-22 | 中国航空制造技术研究院 | Preparation method of high-efficiency low-cost ribbed integral plate blank |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2725612A (en) * | 1955-12-06 | Lipski | ||
| US152794A (en) * | 1874-07-07 | Improvement in girders and columns | ||
| AT50958B (en) * | 1911-01-30 | 1911-11-25 | Witkowitzer Bergb Gewerkschaft | Dismountable iron bridge. |
| US1652056A (en) * | 1927-04-21 | 1927-12-06 | Edward B Selway | Adjustable floor and roof form |
| US2382138A (en) * | 1941-07-02 | 1945-08-14 | Porete Mfg Company | Composite beam structure |
| US2382139A (en) * | 1941-07-16 | 1945-08-14 | Porete Mfg Company | Prestressed composite structure |
| US2373072A (en) * | 1941-08-19 | 1945-04-03 | Ernest M Wichert | Rigid frame bridge and method of making the same |
| US3166830A (en) * | 1962-05-02 | 1965-01-26 | Greulich Gerald Gregory | Method of making prestressed girder |
| US3305612A (en) * | 1964-06-05 | 1967-02-21 | Conodec Inc | Method for forming a prefabricated truss deck |
| BE719675A (en) * | 1968-08-19 | 1969-02-19 | ||
| ES370274A1 (en) * | 1968-08-19 | 1971-04-01 | Lipski | Method for manufacturing a prebent girder embedded in concrete |
| US4093689A (en) * | 1974-03-14 | 1978-06-06 | Licencia Talalmanyokat Ertekesito Vallalat | Process for producing reinforced concrete building units, especially floor panels having smooth surfaces and coffer-like inner holes, and formwork especially for carrying out the process |
| JPS6041404B2 (en) * | 1975-03-14 | 1985-09-17 | マイエフエール・ソシエテ・アノニム | Cooling equipment used to produce insulated metal wire |
| US4279680A (en) * | 1978-07-28 | 1981-07-21 | Watson Jr Louis L | Methods for forming thinwall structures |
| US4493177A (en) * | 1981-11-25 | 1985-01-15 | Grossman Stanley J | Composite, pre-stressed structural member and method of forming same |
-
1985
- 1985-04-03 US US06/719,339 patent/US4646493A/en not_active Expired - Lifetime
- 1985-09-20 CA CA000491171A patent/CA1259813A/en not_active Expired
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1986
- 1986-03-14 AT AT86301876T patent/ATE50528T1/en not_active IP Right Cessation
- 1986-03-14 DE DE8686301876T patent/DE3669124D1/en not_active Expired - Fee Related
- 1986-03-14 EP EP86301876A patent/EP0198600B1/en not_active Expired - Lifetime
- 1986-03-24 AU AU55049/86A patent/AU5504986A/en not_active Abandoned
- 1986-03-29 CN CN86103048A patent/CN1007917B/en not_active Expired
- 1986-04-02 BR BR8601492A patent/BR8601492A/en unknown
- 1986-04-03 JP JP61077501A patent/JPS61274907A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| ATE50528T1 (en) | 1990-03-15 |
| US4646493A (en) | 1987-03-03 |
| CN86103048A (en) | 1986-12-17 |
| JPS61274907A (en) | 1986-12-05 |
| AU5504986A (en) | 1986-10-09 |
| EP0198600A1 (en) | 1986-10-22 |
| EP0198600B1 (en) | 1990-02-28 |
| BR8601492A (en) | 1986-12-09 |
| DE3669124D1 (en) | 1990-04-05 |
| CN1007917B (en) | 1990-05-09 |
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