Expanded polystyrene formwork for cast in place concrete structures

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:

Publication	Title
Designation: C 203-99	Standard Test Methods for Breaking Load
	and Flexural Properties of Block-Type
	Thermal Insulation
Designation: C 578-03b	Standard Specification for Rigid, Cellular
	Polystyrene Thermal Insulation
Designation: D 732-02	Standard Test for Shear Strength of Plastics
	by Punch Tool
Designation: D 1621-00	Standard Test Method for Comprehensive
	Properties of Rigid Cellular Plastics
Designation: D 1622-03	Standard Test for Apparent Density of Rigid
	Cellular Plastics
Designation D 1623-03	Standard 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 hours	Dry to touch
	4-6 hours	Dust-free
	18 hours	Through 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,	5000	cps
	2-component mix:
	Specific Gravity,	1.30
	2-component mix:
	Tensile Strength:	25000	psi
	Comprehensive Strength:	40000	psi
	Maximum Use Temperature:	220°	F.
	Shelf Life:	1	Year

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

Property	Units	ASTM Test	Type XI	Type I	Type VIII	Type II	Type IX
Density, Minimum	pcf	D1622	.7	.9	1.15	1.35	1.8
Density Range	pcf		.70-.89	.90-1.14	1.15-1.34	1.35-1.79	1.80-2.20
Strength Properties
Compressive 10% Deformation	psi	D1621	5-9	10-14	13-18	15-21	25-33
Flexural	psi	C203	10-18	25-30	32-38	40-50	55-75
Tensile	psi	D1623	14-18	16-20	17-21	18-22	23-27
Shear	psi	D732	11-13	18-22	23-25	26-32	33-37
Shear Modulus	psi		190-230	280-320	370-410	460-500	600-640
Modulus of Elasticity	psi		110-150	180-220	250-310	320-360	460-500

R-Control EPS Fabricators

Property	Type XI	Type I	Type VIII	Type II	Type 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 Properties	Unit	1	1.5	2	2.5	3	3.3	4

Stress @ 10%	psi	13	24	30	42	64	67	80
Compression
Flexural Strength	psi	29	43	58	75	88	105	125
Tensile Strength	psi	31	51	62	74	88	98	108
Shear Strength	psi	31	53	70	92	118	140	175

Pacemaker Plastics Corp.

Property	Type XI	Type I	Type VIII	Type II	Type 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 (319	3200 (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

Property	Units	ASTM Test	Type XI	Type I	Type VIII	Type II	Type IX
Density, Minimum	pcf	D1622	.7	.9	1.15	1.35	1.8
Density Range	pcf		.70-.89	.90-1.14	1.15-1.34	1.35-1.79	1.80-2.20
Strength Properties
Compressive 10% Deformation	psi	D1621	5-9	10-14	13-18	15-21	25-33
Flexural	psi	C203	10-18	25-30	32-38	40-50	55-75
Tensile	psi	D1623	14-18	16-20	17-21	18-22	23-27
Shear	psi	D732	11-13	18-22	23-25	26-32	33-37
Shear Modulus	psi		190-230	280-320	370-410	460-500	600-640
Modulus of Elasticity	psi		110-150	180-220	250-310	320-360	460-500

Minimum Properties

Specification reference: ASTM C578

Property	Units	ASTM Test	Type XI	Type I	Type VIII	Type II	Type IX

Density, Minimum	pcf	D1622	.7	.9	1.15	1.35	1.8
Density Range	pcf		.70-.89	.90-1.14	1.15-1.34	1.35-1.79	1.80-2.20
Strength Properties
Compressive 10% Deformation	psi	D1621	5	10	13	15	25
Flexural	psi	C203	10	25	32	40	55
Tensile	psi	D1623	14	16	17	18	23
Shear	psi	D732	11	18	23	26	33
Shear Modulus	psi		190	280	370	460	600
Modulus of Elasticity	psi		110	180	250	320	460

Plywood Properties

Strength Properties

	Compressive 10% Deformation	psi	210
	Flexural	psi	1545
	Shear	psi	57
	Modulus of Elasticity	psi	1500000

Plywood Properties for 12″ Nominal Width

	Nominal Thickness	I	S	lb/Q
	in	in{circumflex over ( )}4	in{circumflex over ( )}3	in{circumflex over ( )}2

	¼	0.008	0.059	2.01
	⅜	0.027	0.125	3.088
	½	0.077	0.236	4.466
	⅝	0.129	0.339	5.2824
	¾	0.197	0.412	6.762
	⅞	0.278	0.515	8.05
	1	0.423	0.664	8.882
	1⅛	0.548	0.82	9.883

Appendix A3

Properties of a 12″ Wide Rectangluar Section

	Ht.	c	I	S	Q	lb/Q
	(in)	(in)	(in{circumflex over ( )}4)	(in{circumflex over ( )}3)	(in{circumflex over ( )}3)	(in{circumflex over ( )}2)

	0.5	0.25	0.125	0.5	0.375	4
	1	0.5	1	2	1.5	8
	1.5	0.75	3.375	4.5	3.375	12
	2	1	8	8	6	16
	2.5	1.25	15.625	12.5	9.375	20
	3	1.5	27	18	13.5	24
	3.5	1.75	42.875	24.5	18.375	28
	4	2	64	32	24	32
	4.5	2.25	91.125	40.5	30.375	36
	5	2.5	125	50	37.5	40
	5.5	2.75	166.375	60.5	45.375	44
	6	3	216	72	54	48
	6.5	3.25	274.625	84.5	63.375	52
	7	3.5	343	98	73.5	56
	7.5	3.75	421.875	112.5	84.375	60
	8	4	512	128	96	64
	8.5	4.25	614.125	144.5	108.375	68
	9	4.5	729	162	121.5	72
	9.5	4.75	857.375	180.5	135.375	76
	10	5	1000	200	150	80
	10.5	5.25	1157.625	220.5	165.375	84
	11	5.5	1331	242	181.5	88
	11.5	5.75	1520.875	264.5	198.375	92
	12	6	1728	288	216	96
	12.5	6.25	1953.125	312.5	234.375	100
	13	6.5	2197	338	253.5	104
	13.5	6.75	2460.375	364.5	273.375	108
	14	7	2744	392	294	112
	14.5	7.25	3048.625	420.5	315.375	116
	15	7.5	3375	450	337.5	120
	15.5	7.75	3723.875	480.5	360.375	124
	16	8	4096	512	384	128
	16.5	8.25	4492.125	544.5	408.375	132
	17	8.5	4913	578	433.5	136
	17.5	8.75	5359.375	612.5	459.375	140
	18	9	5832	648	486	144
	18.5	9.25	6331.625	684.5	513.375	148
	19	9.5	6859	722	541.5	152
	19.5	9.75	7414.875	760.5	570.375	156
	20	10	8000	800	600	160
	20.5	10.25	8615.125	840.5	630.375	164
	21	10.5	9261	882	661.5	168
	21.5	10.75	9938.375	924.5	693.375	172
	22	11	10648	968	726	176
	22.5	11.25	11390.63	1012.5	759.375	180
	23	11.5	12167	1058	793.5	184
	23.5	11.75	12977.88	1104.5	828.375	188
	24	12	13824	1152	864	192
	24.5	12.25	14706.13	1200.5	900.375	196
	25	12.5	15625	1250	937.5	200
	25.5	12.75	16581.38	1300.5	975.375	204
	26	13	17576	1352	1014	208
	26.5	13.25	18609.63	1404.5	1053.375	212
	27	13.5	19683	1458	1093.5	216
	27.5	13.75	20796.88	1512.5	1134.375	220
	28	14	21952	1568	1176	224
	28.5	14.25	23149.13	1624.5	1218.375	228
	29	14.5	24389	1682	1261.5	232
	29.5	14.75	25672.38	1740.5	1305.375	236
	30	15	27000	1800	1350	240
	30.5	15.25	28372.63	1860.5	1395.375	244
	31	15.5	29791	1922	1441.5	248
	31.5	15.75	31255.88	1984.5	1488.375	252
	32	16	32768	2048	1536	256
	32.5	16.25	34328.13	2112.5	1584.375	260
	33	16.5	35937	2178	1633.5	264
	33.5	16.75	37595.38	2244.5	1683.375	268
	34	17	39304	2312	1734	272
	34.5	17.25	41063.63	2380.5	1785.375	276
	35	17.5	42875	2450	1837.5	280
	35.5	17.75	44738.88	2520.5	1890.375	284
	36	18	46656	2592	1944	288
	36.5	18.25	48627.13	2664.5	1998.375	292
	37	18.5	50653	2738	2053.5	296
	37.5	18.75	52734.38	2812.5	2109.375	300
	38	19	54872	2888	2166	304
	38.5	19.25	57066.63	2964.5	2223.375	308
	39	19.5	59319	3042	2281.5	312
	39.5	19.75	61629.88	3120.5	2340.375	316
	40	20	64000	3200	2400	320
	40.5	20.25	66430.13	3280.5	2460.375	324
	41	20.5	68921	3362	2521.5	328

Appendix A4

Plyform B-B Class 1 (Strong with Span)

Nominal F′b = 1545 psi

(for 12″ width)

	Nominal Thickness	S	S * F′b	S * F′b
	(in.)	(in{circumflex over ( )}3)	(in.-lb.)	(ft.-lb)

	¼	0.059	91.16	7.60
	⅜	0.125	193.13	16.09
	½	0.236	364.62	30.39
	⅝	0.339	523.76	43.65
	¾	0.412	636.54	53.05
	⅞	0.515	795.68	66.31
	1	0.664	1025.88	85.49
	1⅛	0.82	1266.90	105.58

Type II Foam

Allowable F′b = 10 psi

(for 12″ width) (Fb = 40 psi :: Safety Factor of 4)

	Nominal Thickness	S	S * F′b	S * F′b
	(in.)	(in{circumflex over ( )}3)	(in.-lb.)	(ft.-lb)

	2	8	80	6.67
	2.5	12.5	125	10.42
	3	18	180	15.00
	3.5	24.5	245	20.42
	4	32	320	26.67
	4.5	40.5	405	33.75
	5	50	500	41.67
	5.5	60.5	605	50.42
	6	72	720	60.00
	6.5	84.5	845	70.42
	7	98	980	81.67
	7.5	112.5	1125	93.75
	8	128	1280	106.67
	8.5	144.5	1445	120.42
	9	162	1620	135.00
	9.5	180.5	1805	150.42
	10	200	2000	166.67

Moment Resistance (Flexural Strength Comparison)

	Needed	Weight	Needed
Given	Plywood	per	Type II	Weight per	Weight Savings
Moment	Thickness	sq. foot	Thickness	Sq. Foot	Per 100 Sq. Ft.
(ft.-lb)	(in.)	lbs.	(in.)	lbs.	(lbs.)

5	¼	0.80	2	0.23	58
10	⅜	1.10	2.5	0.28	82
15	⅜	1.10	3	0.34	76
20	½	1.50	3.5	0.39	111
25	½	1.50	4	0.45	105
30	½	1.50	4.5	0.51	99
35	⅝	1.80	5	0.56	124
40	⅝	1.80	5	0.56	124
50	¾	2.20	5.5	0.62	158
60	⅞	2.60	6	0.68	193
70	1	3.00	6.5	0.73	227
80	1	3.00	7	0.79	221
90	1⅛	3.30	7.5	0.84	246
100	1⅛	3.30	8	0.90	240

Appendix A5

Plyform B-B Class 1 (Strong with Span)

Nominal F′v = 57 psi

(for 12″ width)

Nominal
Thickness	lb/Q	lb/Q * F′v = Vallowed
(in.)	Rolling Shear (in.{circumflex over ( )}2)	(lbs.)

¼	2.01	114.57
⅜	3.088	176.02
½	4.466	254.56
⅝	5.2824	301.10
¾	6.762	385.43
⅞	8.05	458.85
1	8.882	506.27
1⅛	9.883	563.33

Type II Foam

Allowable F′v = 6.5 psi

(for 12″ width, Fv = 26 psi :: Safety Factor of 4)

Nominal	lb/Q
Thickness	Rolling Shear Equivalent	lb/Q * F′v = Vallowed
(in.)	(in.{circumflex over ( )}2)	(lbs.)

2	16	104
2.5	20	130
3	24	156
3.5	28	182
4	32	208
4.5	36	234
5	40	260
5.5	44	286
6	48	312
6.5	52	338
7	56	364
7.5	60	390
8	64	416
8.5	68	442
9	72	468
9.5	76	494
10	80	520
10.5	84	546
11	88	572

Appendix A5

Shear Resistance (Shear Strength Comparison)

Given	Needed	Weight	Needed		Weight
Shear	Plywood	per sq.	Type II	Weight per Sq.	Savings Per
Load	Thickness	foot	Thickness	Foot	100 Sq. Ft.
(lbs)	(in.)	lbs.	(in.)	lbs.	(lbs.)

100	¼	0.80	2	0.225	58
125	⅜	1.10	2.5	0.281	82
150	⅜	1.10	3	0.338	76
175	⅜	1.10	3.5	0.394	71
200	½	1.50	4	0.450	105
225	½	1.50	4.5	0.506	99
250	½	1.50	5	0.563	94
275	⅝	1.80	5.5	0.619	118
300	⅝	1.80	6	0.675	113
350	¾	2.20	7	0.788	141
400	⅞	2.60	8	0.900	170
450	⅞	2.60	9	1.013	159
500	1	3.00	10	1.125	188
550	1⅛	3.30	11	1.238	206

Appendix A6

Plyform B-B Class 1 (Strong with Span)

Nominal E = 1500000 psi

(for 12″ width)

Nominal Thickness	I	Flexural Stiffness El
(in.)	(in.{circumflex over ( )}4)	(lbs-in{circumflex over ( )}2)

¼	0.008	12,000
⅜	0.027	40,500
½	0.077	115,500
⅝	0.129	193,500
¾	0.197	295,500
⅞	0.278	417,000
1	0.423	634,500
1⅛	0.548	822,000

Type II Foam

Allowable E = 320 psi

(for 12″ width, E = 320 :: No Safety Factor for Deflection)

Nominal Thickness	I	Flexural Stiffness EI
(in.)	(in.{circumflex over ( )}4)	(lbs-in{circumflex over ( )}2)

2	8	2,560
2.5	15.625	5,000
3	27	8,640
3.5	42.875	13,720
4	64	20,480
4.5	91.125	29,160
5	125	40,000
5.5	166.375	53,240
6	216	69,120
6.5	274.625	87,880
7	343	109,760
7.5	421.875	135,000
8	512	163,840
8.5	614.125	196,520
9	729	233,280
9.5	857.375	274,360
10	1000	320,000
10.5	1157.625	370,440
11	1331	425,920
11.5	1520.875	486,680
12	1728	552,960
12.5	1953.125	625,000
13	2197	703,040
13.5	2460.375	787,320
14	2744	878,080

Appendix A6

Deflection Comparison for Given Stiffness

	Needed	Weight	Needed	Weight	Weight
Given Stiffness	Plywood	per sq.	Type II	per Sq.	Savings Per
Requirement	Thickness	foot	Thickness	Foot	100 Sq. Ft.
(EI = lbs-in{circumflex over ( )}2)	(in.)	lbs.	(in.)	lbs.	(lbs.)

10,000	¼	0.80	3.5	0.394	41
40,000	⅜	1.10	5	0.563	54
50,000	½	1.50	5.5	0.619	88
75,000	½	1.50	6.5	0.731	77
100,000	½	1.50	7	0.788	71
150,000	⅝	1.80	8	0.900	90
200,000	¾	2.20	9	1.013	119
250,000	¾	2.20	9.5	1.069	113
300,000	⅞	2.60	10	1.125	148
400,000	⅞	2.60	11	1.238	136
500,000	1	3.00	12	1.350	165
600,000	1	3.00	12.5	1.406	159
700,000	1⅛	3.30	13	1.463	184
800,000	1⅛	3.30	14	1.575	173