Title:
Expanded polystyrene formwork for cast in place concrete structures
Kind Code:
A1


Abstract:
A formwork for use in constructing concrete structures is made out of expanded polystyrene coated with an epoxy hard coat on the surfaces of the formwork against which concrete is applied or poured in the construction of concrete structures. A method of making the formwork involves constructing the expanded polystyrene to a desired shape and applying the epoxy to the surfaces of the polystyrene to be used to contact concrete and allowing the epoxy to cure. A method of constructing concrete structures involves using the formwork described.



Inventors:
Fulbright III, Joe Richard (Morrisville, NC, US)
Application Number:
10/912579
Publication Date:
03/31/2005
Filing Date:
08/05/2004
Assignee:
FULBRIGHT JOE RICHARD
Primary Class:
International Classes:
E04G9/05; (IPC1-7): E04B9/00
View Patent Images:



Primary Examiner:
WENDELL, MARK R
Attorney, Agent or Firm:
Joe R Fulbright III (Morrisville, NC, US)
Claims:
1. A formwork for cast in place concrete structures, comprising: a formwork structure made of expanded polystyrene; and an enamel coating on at least one surface of said formwork to be in contact with poured or applied concrete which will make up at least a part of a concrete structure.

2. The formwork of claim 1, wherein said expanded polystyrene has a density of at least about 1.35 pcf.

3. The formwork of claim 2, wherein said expanded polystyrene has a density of at least about 1.35 pcf to about 1.79 pcf.

4. The formwork of claim 1, wherein the strength properties of said expanded polystyrene comprises: Compressive 10% Deformation Strength of at least about 15 psi; Flexural Strength of at least about 40 psi; Tensile Strength of at least about 18 psi; Shear Strength of at least about 26 psi; Shear Modulus of at least about 460 psi; and Modulus of Elasticity of at least about 320 psi.

5. The formwork of claim 1, wherein the strength properties of said expanded polystyrene comprises: Stress at 10% Compression of at least about 30 psi; Flexural Strength of at least about 58 psi; Tensile Strength of at least about 62 psi; and Shear Strength of at least about 70 psi.

6. The formwork of claim 1, wherein the enamel coating is polyurethane.

7. The formwork of claim 6, wherein the polyurethane coating is made from a two component unfilled epoxy mixed with a catalytic hardener, the resulting polystyrene having tensile strength properties of about 25,000 psi and comprehensive strength properties of about 40,000 psi.

8. A method of manufacturing a formwork for cast in place concrete structures, comprising: shaping a piece of expanded polystyrene into a predetermined formwork shape; applying an enamel coating on at least one surface of said formwork to be in contact with poured or applied concrete; and curing the enamel coating.

9. A method of manufacturing a concrete structure comprising: shaping a piece of expanded polystyrene into a predetermined formwork shape; applying an enamel coating on at least one surface of said formwork to be in contact with poured or applied concrete; curing the enamel coating; applying or pouring concrete into contact with the cured enamel coating to have the concrete assume a desired shape; allowing the concrete to cure; and removing the formwork after the concrete has cured sufficiently to result in at least a portion of a concrete structure.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to Provisional Application Ser. No. 60/493,114 filed Aug. 6, 2003, the disclosure of which is incorporated by reference herein in its entirety, and to which priority is explicitly claimed herein to the filing date thereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention, in general, relates to the field of building construction. More precisely, the invention relates to the construction of concrete structures using a new formwork. Specifically, the present invention relates to using a formwork composed of expanded polystyrene (EPS) coated with a two-part liquid epoxy hard coat for the construction of concrete structures.

2. Discussion of the Related Art

Historically, builders have used formworks in the construction of elevated concrete slabs and beams. For example, when forming an elevated slab, concrete is poured on top of a formwork deck and over horizontally projected rebar (structural steel). The formwork deck is held in place at the desired elevation by numerous methods. These include, but are not limited to, scaffolding and wooden posts. Concrete columns and walls have been poured previously in order to hold up the elevated deck and beams. Upon sufficient curing of the concrete, the formwork is removed from below to leave a free-standing elevated concrete deck and beam system.

Currently, elevated concrete beam and slab systems are constructed using formwork systems which are composed of plywood, steel, or fiberglass. Each of these methods is costly, and takes large amounts of work to install properly. Plywood formwork beam and slab systems are the easiest of the three. The finished surface left by plywood typically contains wood grain impressions retained in the concrete from the wooden surface of the plywood sheets. This can be remedied by employing the use of high grade plywood. However, this increases the cost tremendously. Steel pans are also used in the construction of beam and slab systems.

Steel pans are more expensive than using plywood decking. They are also much larger in weight, making the man hours required for construction of the beam and slab system even higher. The finished surface that is left by steel pans is better than that left by plywood decking. Fiberglass formwork for beam and slab systems is the most expensive means of constructing a concrete deck.

Fiberglass formwork is also much heavier than either plywood decking or steel pans, and is an even more labor-intensive construction practice. The finished surface of the concrete, using fiberglass for formwork, is typically much better than that of both steel pans and plywood.

The possibility of reusing plywood, steel, and fiberglass varies. Plywood can be reused several times, with the finished surface of the concrete decreasing in quality with each reuse. Plywood also demands the harvesting of valuable natural resources required for its production. It cannot be recycled at the conclusion of its usefulness and must be disposed of in landfills. Similarly, steel pans can be reused as formwork numerous times. Steel pans produce a finished surface on the concrete that also diminishes with use of the steel pans. Steel pans, however, can be melted down for reuse at the end of a job. Fiberglass forms can typically be used for multiple pours for the duration of a construction project with minimal decline in the finished surface of the concrete. However, at the conclusion of a construction project fiberglass formwork cannot be recycled and must be disposed of.

With the current implementation of plywood, steel, or fiberglass formwork, there is a limit to the shapes which are attainable in concrete construction. Irregular shapes, such as intricate curves, are not an option using current construction methods.

An alternative approach more recently available from a company known as Alkus ((http://alkus.de/gb/NN_index.html) Aug. 3, 2004) involves manufacturing formwork panels out of polypropylene reinforced with aluminum or glass fiber mat. A problem with such panels is that they are difficult to shape and suffer the same disadvantages and more than the aforementioned steel and fiberglass forms, and cannot be molded into intricate shapes.

SUMMARY OF THE INVENTION

The present invention is directed towards constructing a static mold or formwork structure. The mold may be used to form a building structure such as an elevated beam and slab system. A generally U-shape channel form is especially adapted to form a concrete beam for the system. The slab is an outwardly extending section of concrete that is constructed at the same time as the beam. The system will be composed of a plurality of beams. The system will typically contain horizontally extending rebar (structural steel reinforcement bars). The formwork is composed of a certain density of Expanded Polystyrene (EPS). The density will depend on the structural requirements for the safe construction of said concrete system. Ordinarily, it is anticipated that the formwork will be made of two pound density expanded polystyrene. The EPS will be cut to the desired shape, and placed into a restrained system in order to preclude movement occurring at the time of concrete placement. The EPS will then be coated with a two-part epoxy/polyurethane enamel in order to provide a finish currently unattainable with present Cast in Place (CIP) forming methods. When properly vibrated and placed, the polyurethane “hard-coat” will leave the bottom surface (ceiling) of the elevated deck with a finish that will appear to be smooth and polished. This finish is currently unattainable solely with current formwork approaches. Upon sufficient curing of the concrete, the EPS CIP forms will be removed for reuse, recycling, or disposal.

A primary object of the invention is to provide a cheaper means of cast in place concrete construction. Another objective of the invention is to provide the finished concrete surface with an appearance that will be smooth and polished. The EPS formwork will be much lighter than typical wood, steel, or fiberglass decks, thus facilitating a construction cycle that is much quicker in installation than is currently attainable in industry. Another benefit of using EPS formwork is that it is recyclable after construction use. EPS formwork will not contribute to refuse in landfills, and does not require the use of valuable natural resources—such as those required by steel and wood formwork. Another benefit of using EPS formwork is the shapes which are currently unattainable in concrete cast in place construction. The EPS formwork can be cut into intricate designs and then cast into the bottom, or “ceiling” of the concrete beam and slab system.

BRIEF DESCRIPTION OF THE DRAWINGS

Having briefly described the invention, the same will become better understood from the appended drawings, wherein:

FIG. 1 is a perspective view representative of a formwork constructed in accordance with the invention; and

FIG. 2 is an isometric cross-sectional view of the formwork of FIG. 1

DETAILED DISCUSSION

In accordance with the invention as illustrated in FIG. 1, a preferred embodiment of the formwork 11 includes a central portion 13 typically made of expanded polystyrene, while shown as a rectangular structure, it will be appreciated by those of ordinary skill in the art that the formwork can be copied into intricate shapes as appropriate to the concrete structure being poured or constructed. Once cut to the desired shape, the formwork or formwork panel is placed into a restraint system in order to preclude movement at the time of concrete placement or pouring. Prior to pouring the concrete, an epoxy polyurethane enamel is applied on the surfaces which will be in contact with the concrete, and allowed to cure. Thereafter, the formwork is properly vibrated and placed and the concrete poured. Upon sufficient curing of the concrete, the formwork is removed for reuse, recycling or disposal, and the polyurethane hard coat leaves a smooth surface which appears to be both smooth and polished.

FIG. 2 illustrates in greater detail the formwork 11 of FIG. 1 shown in cross-section. As may be appreciated, the center section 13 is made of expanded polystyrene may have on both upper and lower surfaces, for example in the case where it is used to construct an elevated deck, the epoxy polyurethane enamel portions 15 can be both on the top and bottom side and used to leave the bottom surface, i.e. ceiling of an elevated deck with a finish which appears to be smooth and polished.

In implementing the invention, specific types of expanded polyurethane are used, for example, as described in Appendix A1- A6 entitled “Typical Physical Properties of Expanded Polystyrene for Use in the Formwork”, which follow and are part of the specification, are incorporated by reference herein, and are located before the claims.

Appendix A2 also compares the material used (polystyrene) for the invention favorably relative to the use of plywood, and also describes other properties of the polystyrene material applicable for use in the invention.

As will be appreciated by those of ordinary skill in the art, this information is readily available from numerous websites such as www.carpenter.com as of Aug. 3, 2004 and others.

In the case of the invention, the expanded polystyrene is shown having certain properties in the shaded area in Appendix A1 and identified as type II exhibiting a density (in pcf) of at least 1.35, and preferably about 1.35 to about 1.79 is most preferred for use in accordance with the invention. While a preferred expanded polystyrene has been identified herein, it will be readily apparent to those of ordinary skill in the art, that alternative types can be employed as may be appropriate to the particular or specific application, depending on structural need and what is being built.

More specifically, in arriving at desired formwork load bearing calculations, published ASTM methods were reviewed and used to arrive at the desired load bearing calculations. More specifically, these ASTM methods are described in the following ASTM international publications, the disclosures of which are specifically incorporated by reference herein. The publications are as follows:

PublicationTitle
Designation: C 203-99Standard Test Methods for Breaking Load
and Flexural Properties of Block-Type
Thermal Insulation
Designation: C 578-03bStandard Specification for Rigid, Cellular
Polystyrene Thermal Insulation
Designation: D 732-02Standard Test for Shear Strength of Plastics
by Punch Tool
Designation: D 1621-00Standard Test Method for Comprehensive
Properties of Rigid Cellular Plastics
Designation: D 1622-03Standard Test for Apparent Density of Rigid
Cellular Plastics
Designation D 1623-03Standard Test Method for Tensile and Tensile
Adhesion Properties of Rigid Cellular Plastics

With respect to the epoxy/polyurethane enamel employed in accordance with the invention, one such enamel is available from Demand Products, Inc. under the name Liquid Rock. A Technical Data Sheet and Material Safety Data Sheet provide details about the specific material and is available form Demand Products, Inc. of Alpharetta, Ga. More specifically, a link to that company's website on the Internet is available at http://www.demandproducts.com and http://www.demandhotwire.com as of Aug. 3, 2004.

The material is a 2-component unfilled epoxy with low viscosity and good flow qualities which can be applied over plastic foam surfaces where a hard, durable, and smooth coating is required. With respect to its specific properties, they are set forth in the following Tables:

TABLE 1
Encapsulant is a two-component, unfilled epoxy with low
viscosity and flow quantities. Can be applied over plastic
foam surfaces where a hard, durable, and smooth coating is
required.
Ratio Parts by Weight:100
Catalyst (Hardener): 16
Ratio Parts by Volume: 4.99
Catalyst (Hardener) 1
Room Temp., 72° F.: 20 mins.
Cure: 2-3 hoursDry to touch
4-6 hoursDust-free
 18 hoursThrough Cure

*Pot Life 100 gram Mass

*These times will change depending on volume and temperature.

TABLE 2
Physical Properties @ 72° F.
Color:Off-white
Shore “D” Hardness ASTM D2240:82
Viscosity,5000cps
2-component mix:
Specific Gravity,1.30
2-component mix:
Tensile Strength:25000psi
Comprehensive Strength:40000psi
Maximum Use Temperature:220°F.
Shelf Life:1Year

Thus, as may be appreciated not only does the invention involve a new and integrated structure for formwork to be used in concrete applications, there is also provided a method of making such formwork structures. The method generally involves cutting a shape in a structure made of expanded polystyrene into a desired shape for use in poured or applied concrete applications. An epoxy polyurethane enamel is then applied to the surface of the expanded polystyrene which is to bear against poured or applied concrete. The enamel is allowed to cure and the concrete is thereafter poured or applied to be in contact with the enamel. In a yet still further aspect, the invention involves constructing concrete structures using the formwork in accordance with the invention by assembling the formwork as previously described, thereafter pouring or applying the concrete and when the concrete has substantially or sufficiently cured, removing the formwork to result in a concrete surface which appears smooth and polished.

Having thus generally described the invention, the same will become better understood from the appended claims in which it is set forth in a non-limiting manner.

Appendix A1

typical physical properties of expanded polystyrene:

Specification reference: ASTM C578
PropertyUnitsASTM TestType XIType IType VIIIType IIType IX
Density, MinimumpcfD1622.7.91.151.351.8
Density Rangepcf.70-.89 .90-1.141.15-1.341.35-1.791.80-2.20
Strength Properties
Compressive 10% DeformationpsiD16215-910-1413-1815-2125-33
FlexuralpsiC20310-1825-3032-3840-5055-75
TensilepsiD162314-1816-2017-2118-2223-27
ShearpsiD73211-1318-2223-2526-3233-37
Shear Moduluspsi190-230280-320370-410460-500600-640
Modulus of Elasticitypsi110-150180-220250-310320-360460-500

R-Control EPS Fabricators

PropertyType XIType IType VIIIType IIType IX
Nominal Density, lb/ft3 (kg/m3)0.75 (12)1.00 (16)1.25 (20)1.50 (24) 2.00 (32)
Density1, min., lb/ft3 (kg/m3)0.70 (12)0.90 (15)1.15 (18)1.35 (22)0.180 (29)
Compressive strength1 @10% def., min., psi  5  10  13  15  25
Flexural strength1,  10  25  30  40  50

1See ASTM C-578 Standard Specification for complete information

Alliance of Foam Packaging Recyclers:

Density (pcf)
Strength PropertiesUnit11.522.533.34
Stress @ 10%psi13243042646780
Compression
Flexural Strengthpsi2943587588105125
Tensile Strengthpsi315162748898108
Shear Strengthpsi31537092118140175

Pacemaker Plastics Corp.

PropertyType XIType IType VIIIType IIType IX
Nominal Density, lb/ft3 (kg/m3) 0.75 (12) 1.00 (16) 1.25 (20) 1.50 (24) 2.00 (32)
Density1, min., lb/ft3 (kg/m3) 0.70 (12) 0.90 (15) 1.15 (18) 1.35 (22) 1.80 (29)
Compressive strength1 @10% def., min., psi (kPa)  5.0 (35) 10.0 (69) 13.0 (90) 15.0 (104) 25.0 (173)
Flexural Strength1, min., psi (kPa) 10.0 (69) 25.0 (173) 30.0 (208) 40.0 (276) 50.0 (345)
Compressive Resistance2 @1% deformation, min., kPa (psi) 22 (3.2) 32 (4.6) 43 (6.2) 57 (8.3) 82 (11.9)
Modulus of Elasticity2, min., kPa (psi)2200 (3193200 (464)4300 (624)5700 (827)8200 (1189)

Pacemaker Expanded Polystyrene (EPS) Properties per ASTM C 578 and UL Tests

Appendix A2

Published Properties

Specification reference: ASTM C578
PropertyUnitsASTM TestType XIType IType VIIIType IIType IX
Density, MinimumpcfD1622.7.91.151.351.8
Density Rangepcf.70-.89 .90-1.141.15-1.341.35-1.791.80-2.20
Strength Properties
Compressive 10% DeformationpsiD16215-910-1413-1815-2125-33
FlexuralpsiC20310-1825-3032-3840-5055-75
TensilepsiD162314-1816-2017-2118-2223-27
ShearpsiD73211-1318-2223-2526-3233-37
Shear Moduluspsi190-230280-320370-410460-500600-640
Modulus of Elasticitypsi110-150180-220250-310320-360460-500

Minimum Properties

Specification reference: ASTM C578
PropertyUnitsASTM TestType XIType IType VIIIType IIType IX
Density, MinimumpcfD1622.7.91.151.351.8
Density Rangepcf.70-.89.90-1.141.15-1.341.35-1.791.80-2.20
Strength Properties
Compressive 10% DeformationpsiD1621510131525
FlexuralpsiC2031025324055
TensilepsiD16231416171823
ShearpsiD7321118232633
Shear Moduluspsi190280370460600
Modulus of Elasticitypsi110180250320460

Plywood Properties

Strength Properties
Compressive 10% Deformationpsi210
Flexuralpsi1545
Shearpsi57
Modulus of Elasticitypsi1500000

Plywood Properties for 12″ Nominal Width

Nominal ThicknessISlb/Q
inin{circumflex over ( )}4in{circumflex over ( )}3in{circumflex over ( )}2
¼0.0080.0592.01
0.0270.1253.088
½0.0770.2364.466
0.1290.3395.2824
¾0.1970.4126.762
0.2780.5158.05
10.4230.6648.882
1⅛0.5480.829.883

Appendix A3

Properties of a 12″ Wide Rectangluar Section

Ht.cISQlb/Q
(in)(in)(in{circumflex over ( )}4)(in{circumflex over ( )}3)(in{circumflex over ( )}3)(in{circumflex over ( )}2)
0.50.250.1250.50.3754
10.5121.58
1.50.753.3754.53.37512
2188616
2.51.2515.62512.59.37520
31.5271813.524
3.51.7542.87524.518.37528
4264322432
4.52.2591.12540.530.37536
52.51255037.540
5.52.75166.37560.545.37544
63216725448
6.53.25274.62584.563.37552
73.53439873.556
7.53.75421.875112.584.37560
845121289664
8.54.25614.125144.5108.37568
94.5729162121.572
9.54.75857.375180.5135.37576
105100020015080
10.55.251157.625220.5165.37584
115.51331242181.588
11.55.751520.875264.5198.37592
126172828821696
12.56.251953.125312.5234.375100
136.52197338253.5104
13.56.752460.375364.5273.375108
1472744392294112
14.57.253048.625420.5315.375116
157.53375450337.5120
15.57.753723.875480.5360.375124
1684096512384128
16.58.254492.125544.5408.375132
178.54913578433.5136
17.58.755359.375612.5459.375140
1895832648486144
18.59.256331.625684.5513.375148
199.56859722541.5152
19.59.757414.875760.5570.375156
20108000800600160
20.510.258615.125840.5630.375164
2110.59261882661.5168
21.510.759938.375924.5693.375172
221110648968726176
22.511.2511390.631012.5759.375180
2311.5121671058793.5184
23.511.7512977.881104.5828.375188
2412138241152864192
24.512.2514706.131200.5900.375196
2512.5156251250937.5200
25.512.7516581.381300.5975.375204
26131757613521014208
26.513.2518609.631404.51053.375212
2713.51968314581093.5216
27.513.7520796.881512.51134.375220
28142195215681176224
28.514.2523149.131624.51218.375228
2914.52438916821261.5232
29.514.7525672.381740.51305.375236
30152700018001350240
30.515.2528372.631860.51395.375244
3115.52979119221441.5248
31.515.7531255.881984.51488.375252
32163276820481536256
32.516.2534328.132112.51584.375260
3316.53593721781633.5264
33.516.7537595.382244.51683.375268
34173930423121734272
34.517.2541063.632380.51785.375276
3517.54287524501837.5280
35.517.7544738.882520.51890.375284
36184665625921944288
36.518.2548627.132664.51998.375292
3718.55065327382053.5296
37.518.7552734.382812.52109.375300
38195487228882166304
38.519.2557066.632964.52223.375308
3919.55931930422281.5312
39.519.7561629.883120.52340.375316
40206400032002400320
40.520.2566430.133280.52460.375324
4120.56892133622521.5328

Appendix A4

Plyform B-B Class 1 (Strong with Span)
Nominal F′b = 1545 psi
(for 12″ width)
Nominal ThicknessSS * F′bS * F′b
(in.)(in{circumflex over ( )}3)(in.-lb.)(ft.-lb)
¼0.05991.167.60
0.125193.1316.09
½0.236364.6230.39
0.339523.7643.65
¾0.412636.5453.05
0.515795.6866.31
10.6641025.8885.49
1⅛0.821266.90105.58

Type II Foam
Allowable F′b = 10 psi
(for 12″ width) (Fb = 40 psi :: Safety Factor of 4)
Nominal ThicknessSS * F′bS * F′b
(in.)(in{circumflex over ( )}3)(in.-lb.)(ft.-lb)
28806.67
2.512.512510.42
31818015.00
3.524.524520.42
43232026.67
4.540.540533.75
55050041.67
5.560.560550.42
67272060.00
6.584.584570.42
79898081.67
7.5112.5112593.75
81281280106.67
8.5144.51445120.42
91621620135.00
9.5180.51805150.42
102002000166.67

Moment Resistance (Flexural Strength Comparison)
NeededWeightNeeded
GivenPlywoodperType IIWeight perWeight Savings
MomentThicknesssq. footThicknessSq. FootPer 100 Sq. Ft.
(ft.-lb)(in.)lbs.(in.)lbs.(lbs.)
5¼0.8020.2358
101.102.50.2882
151.1030.3476
20½1.503.50.39111
25½1.5040.45105
30½1.504.50.5199
351.8050.56124
401.8050.56124
50¾2.205.50.62158
602.6060.68193
7013.006.50.73227
8013.0070.79221
901⅛3.307.50.84246
1001⅛3.3080.90240

Appendix A5

Plyform B-B Class 1 (Strong with Span)
Nominal F′v = 57 psi
(for 12″ width)
Nominal
Thicknesslb/Qlb/Q * F′v = Vallowed
(in.)Rolling Shear (in.{circumflex over ( )}2)(lbs.)
¼2.01114.57
3.088176.02
½4.466254.56
5.2824301.10
¾6.762385.43
8.05458.85
18.882506.27
1⅛9.883563.33

Type II Foam
Allowable F′v = 6.5 psi
(for 12″ width, Fv = 26 psi :: Safety Factor of 4)
Nominallb/Q
ThicknessRolling Shear Equivalentlb/Q * F′v = Vallowed
(in.)(in.{circumflex over ( )}2)(lbs.)
216104
2.520130
324156
3.528182
432208
4.536234
540260
5.544286
648312
6.552338
756364
7.560390
864416
8.568442
972468
9.576494
1080520
10.584546
1188572

Appendix A5

Shear Resistance (Shear Strength Comparison)
GivenNeededWeightNeededWeight
ShearPlywoodper sq.Type IIWeight per Sq.Savings Per
LoadThicknessfootThicknessFoot100 Sq. Ft.
(lbs)(in.)lbs.(in.)lbs.(lbs.)
100¼0.8020.22558
1251.102.50.28182
1501.1030.33876
1751.103.50.39471
200½1.5040.450105
225½1.504.50.50699
250½1.5050.56394
2751.805.50.619118
3001.8060.675113
350¾2.2070.788141
4002.6080.900170
4502.6091.013159
50013.00101.125188
5501⅛3.30111.238206

Appendix A6

Plyform B-B Class 1 (Strong with Span)
Nominal E = 1500000 psi
(for 12″ width)
Nominal ThicknessIFlexural Stiffness El
(in.)(in.{circumflex over ( )}4)(lbs-in{circumflex over ( )}2)
¼0.00812,000
0.02740,500
½0.077115,500
0.129193,500
¾0.197295,500
0.278417,000
10.423634,500
1⅛0.548822,000

Type II Foam
Allowable E = 320 psi
(for 12″ width, E = 320 :: No Safety Factor for Deflection)
Nominal ThicknessIFlexural Stiffness EI
(in.)(in.{circumflex over ( )}4)(lbs-in{circumflex over ( )}2)
282,560
2.515.6255,000
3278,640
3.542.87513,720
46420,480
4.591.12529,160
512540,000
5.5166.37553,240
621669,120
6.5274.62587,880
7343109,760
7.5421.875135,000
8512163,840
8.5614.125196,520
9729233,280
9.5857.375274,360
101000320,000
10.51157.625370,440
111331425,920
11.51520.875486,680
121728552,960
12.51953.125625,000
132197703,040
13.52460.375787,320
142744878,080

Appendix A6

Deflection Comparison for Given Stiffness
NeededWeightNeededWeightWeight
Given StiffnessPlywoodper sq.Type II per Sq.Savings Per
RequirementThicknessfootThicknessFoot100 Sq. Ft.
(EI = lbs-in{circumflex over ( )}2)(in.)lbs.(in.)lbs.(lbs.)
10,000¼0.803.50.39441
40,0001.1050.56354
50,000½1.505.50.61988
75,000½1.506.50.73177
100,000½1.5070.78871
150,0001.8080.90090
200,000¾2.2091.013119
250,000¾2.209.51.069113
300,0002.60101.125148
400,0002.60111.238136
500,00013.00121.350165
600,00013.0012.51.406159
700,0001⅛3.30131.463184
800,0001⅛3.30141.575173





 
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