by george a. fernandez - university of...

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WIND LOAD RESISTANCE OF COMPOSITE STRUCTURAL INSULATED PANELS

By

GEORGE A. FERNANDEZ

A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT

OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENGINEERING

UNIVERSITY OF FLORIDA

2013

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© 2013 George A. Fernandez

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To my mom, Claudia, my brother, Kevin and my grandparents, Coco and Papa Mundo

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ACKNOWLEDGMENTS

I would like to thank my advisor, Forrest J. Masters, Ph.D., P.E.; and my

committee members, Kurtis R. Gurley, Ph.D. and David O. Prevatt, Ph.D., P.E. for their

support and guidance throughout this project. I thank my colleagues, Dany Romero,

Abraham Alende, Carlos Lopez, Scott Bolton, Jimmy Jesteadt, Alex Esposito, Jason

Smith, James Austin, Johann Weekes, Sylvia Laboy, Alon Krauthammer, Anthony

Chanlee and Justin Henika, for their support and assistance throughout this project.

I would also like to acknowledge NSF CMMI for supporting this project and Dr.

Ed Sutt from Simpson Strong-Tie for their assistance.

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TABLE OF CONTENTS

page

ACKNOWLEDGMENTS .................................................................................................. 4

TABLE OF CONTENTS .................................................................................................. 5

LIST OF TABLES ............................................................................................................ 7

LIST OF FIGURES .......................................................................................................... 8

LIST OF ABBREVIATIONS ........................................................................................... 12

LIST OF NOMENCLATURE .......................................................................................... 13

ABSTRACT ................................................................................................................... 14

CHAPTER

1 INTRODUCTION .................................................................................................... 16

Scope of Research ................................................................................................. 17 Organization of this Document ................................................................................ 17

2 BACKGROUND ...................................................................................................... 18

Traditional Light Wood Frame Construction ............................................................ 18

Applicable Standards ....................................................................................... 19 Prior Research ................................................................................................. 19

Sandwich Panels .................................................................................................... 20 Composite Beam Theory .................................................................................. 20 Structural Insulated Panels ............................................................................... 21

Composite structural Insulated Panels ............................................................. 21

3 EXPERIMENTAL DESIGN ..................................................................................... 24

4 DESIGN AND EVALUATION OF CSIP WALL CONNECTION ............................... 26

5 EVALUATION OF CSIPS WALL ASSEMBLY SUBJECTED TO WIND PRESSURE LOADING ........................................................................................... 32

Pressure step loading function ................................................................................ 33 Individual Test Results Static Step Loading 48.05 kg/m3 (3 pcf) ...................... 33

Test #1 ....................................................................................................... 33 Test #2 ....................................................................................................... 34 Test #3 ....................................................................................................... 35 Test #4 ....................................................................................................... 36

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Individual Test Results Static Step Loading 16.02 kg/m3 (1 pcf) ...................... 37

Test #1 ....................................................................................................... 37 Time-varying pressure sequence ............................................................................ 38

Individual Test Results Dynamic Loading 48.05 kg/m3 (3 pcf) .......................... 39 Test #1 ....................................................................................................... 39 Test #2 ....................................................................................................... 40 Test #3 ....................................................................................................... 41 Test #4 ....................................................................................................... 42

Test #5 ....................................................................................................... 43 Test #6 ....................................................................................................... 44

Individual Test Results Dynamic Loading 16.02 kg/m3 (1 pcf) .......................... 44 Test #1 ....................................................................................................... 44 Test #2 ....................................................................................................... 45

Summary of Pressure Loading Results................................................................... 46 Comparison of Capacity and Failure Modes ........................................................... 48

6 EVALUATION OF CSIP WALL ASSEMBLY SUBJECTED TO SHEAR LOADING ................................................................................................................ 85

Methodology ........................................................................................................... 85 Results .................................................................................................................... 85

7 CONCLUSIONS ..................................................................................................... 90

APPENDIX

RESULTS OF LATERAL LOAD TEST .......................................................................... 93

LIST OF REFERENCES ............................................................................................... 98

BIOGRAPHICAL SKETCH .......................................................................................... 101

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LIST OF TABLES

Table page 3-1 CSIP Panel Inventory ........................................................................................ 25

3-2 Testing Matrix .................................................................................................... 25

4-1 Fastener summary ............................................................................................. 31

4-2 T-test results for single fastener at two different temperatures .......................... 31

5-1 Static pressure step and equivalent mean wind speed ...................................... 83

5-2 Time varying basic wind speed and mean pressure .......................................... 83

5-3 Maximum pressure comparison table ................................................................ 83

5-4 Maximum deflection table .................................................................................. 84

6-1 Racking test results ........................................................................................... 89

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LIST OF FIGURES

Figure page

2-1 SIP wall anatomy ................................................................................................ 23

2-2 CSIP cross sectional illustration ......................................................................... 23

4-1 Proposed construction assembly ........................................................................ 28

4-2 Lateral resistance testing. Photo courtesy of George Fernandez, University of Florida. ............................................................................................................... 28

4-3 Lateral capacities of nail fasteners ..................................................................... 29

4-4 Lateral capacities stratified by effective area ...................................................... 30

5-1 Two photographs of the pressure testing components A) HAPLA testing apparatus B) exterior view of testing chamber. Photo courtesy of George Fernandez and Forrest Masters, University of Florida. ....................................... 50

5-2 Strain gauge location .......................................................................................... 51

5-3 Reaction frame connection detail ....................................................................... 51

5-4 Pressure step loading function ........................................................................... 52

5-5 48.05 kg/m3 (3 pcf) CSIP Test 1 pressure time history ....................................... 52

5-6 48.05 kg/m3 (3 pcf) CSIP Test 1 deflection time history ..................................... 53

5-7 48.05 kg/m3 (3 pcf) CSIP Test 1 de-bonding and failure sketch ......................... 53

5-8 48.05 kg/m3 (3 pcf) CSIP Test 1 failure. Photo courtesy of George Fernandez, University of Florida. ........................................................................ 54

5-9 48.05 kg/m3 (3 pcf) CSIP Test 1 summary ......................................................... 54






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5-24 16.02 kg/m3 (1 pcf) CSIP Test 1 failure. Photo courtesy of George Fernandez, University of Florida. ........................................................................ 62


5-26 Complete time-varying pressure sequence ........................................................ 63

5-27 Sample of the time-varying pressure sequence.................................................. 63

5-28 48.05 kg/m3 (3 pcf) CSIP Test 1 time varying pressure time history ................... 64

5-29 48.05 kg/m3 (3 pcf) CSIP Test 1 time varying pressure deflection time history .. 64

5-30 48.05 kg/m3 (3 pcf) CSIP Test 1 time varying pressure deflection-load plot ....... 65




5-34 48.05 kg/m3 (3 pcf) CSIP Test 2 time varying pressure deflection-load plot ...... 67

5-35 48.05 kg/m3 (3 pcf) CSIP Test 2 de-bonding and failure sketch ........................ 67





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5-54 16.02 kg/m3 (1 pcf) CSIP Test 1 time varying pressure deflection-load plot ....... 77






5-60 Deflection-load results for the 16.02 kg/m3 (1 pcf) panels .................................. 80

5-61 Deflection-load results for the 48.05 kg/m3 (3 pcf) panels .................................. 80

5-62 Observed damage. Photo courtesy of George Fernandez, University of Florida. ............................................................................................................... 81

5-63 Un-filtered mid-span deflection versus pressure................................................. 81

5-64 Filtered mid-span deflection versus pressure ..................................................... 82

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5-65 Time-varying pressure vs. mid-span strain ......................................................... 82

6-1 Diagram of racking test setup ............................................................................. 87

6-2 Racking test load deflection interaction .............................................................. 87

6-3 Racking test face-sheet de-bonding. Photo courtesy of George Fernandez and Scott Bolton, University of Florida. ............................................................... 88

6-4 Racking test face-sheet wrinkling. Photo courtesy of George Fernandez and Scott Bolton, University of Florida. ...................................................................... 88

A-1 Lateral nail capacity failure results A-S-8d. Photo courtesy of George Fernandez, University of Florida. ........................................................................ 93

A-2 Lateral nail capacity failure results B-RS-8d. Photo courtesy of George Fernandez, University of Florida. ........................................................................ 94

A-3 Lateral nail capacity failure results C-S-6d. Photo courtesy of George Fernandez, University of Florida. ........................................................................ 95

A-4 Lateral nail capacity failure results SST-SS-6d. Photo courtesy of George Fernandez, University of Florida. ........................................................................ 96

A-5 Lateral nail capacity failure results SST-RS-6d. Photo courtesy of George Fernandez, University of Florida. ........................................................................ 97

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LIST OF ABBREVIATIONS

ASCE AMERICAN SOCIETY OF CIVIL ENGINEERS

ASTM AMERICAN SOCIETY FOR TESTING AND MATERIALS

CSIP COMPOSITE STRUCTURAL INSULATED PANELS

FEMA FEDERAL EMERGENCY MANAGEMENT AGENCY

IBHS INSTITUTE OF BUSINESS & HOME SAFETY

NOAA NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

UF UNIVERSITY OF FLORIDA

UAB UNIVERSITY OF ALABAMA AT BIRMINGHAM

SIP STRUCTURAL INSULATED PANELS

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LIST OF NOMENCLATURE

Efz Face sheet modulus of elasticity

Ecz Foam core modulus of elasticity

G Shear modulus

B Width

C Core thickness

A Cross sectional area

T Face thickness

D Distance between center-lines of opposite faces

q Distributed load per unit length

H Overall thickness

Δ Displacement at mid-span

L Span length

D Flexural rigidity of beam

𝑙 Integral length scale

𝑓 Frequency

U Mean velocity

Cp Pressure coefficient

Ρ Density of air

v Velocity (mph)

qz Velocity pressure (psf)

Kz 0.85, Velocity pressure coefficient

Kzt 1.0, Topographic factor

Kd 0.85, Wind directionality factor

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the

Requirements for the Degree of Master of Engineering

WIND LOAD RESISTANCE OF COMPOSITE STRUCTURAL INSULATED PANELS

By

George A. Fernandez

December 2013 Chair: Forrest Masters Major: Civil Engineering

The study evaluates the out-of-plane wind load resistance and in-plane shear

resistance of a new thermoplastic CSIP developed by the University of Alabama at

Birmingham, to address the growing demand for affordable, energy efficient building

materials. Uniaxial bending response of these panels under realistic hurricane wind load

conditions was evaluated. The panels were subjected to a step- loading pressure

sequence and a dynamic wind pressure time history sequence. The dynamic wind

pressure time history was derived from boundary layer wind tunnel model experiments.

Similar failure mechanisms were observed for both load sequences. Damage was

confined primarily to the timber connection plate, however de-bonding between the skin

and foam was observed. The pressure step loading function ranged from 0.24-6.96 kPa

and an average mid-span deflection of 9.00 cm over a 243.84 cm span was observed.

The dynamic pressure loads ranged from 0.24-5.00 kPa with an average mid-span

deflection of 7.00 cm over a 243.84 cm span. A load-deflection relationship was

established and the use of a theoretical Equation, developed by Allen (1969), was used

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to compare the test data. Investigative testing of in-plane shear resistance was

conducted and compared with test conducted by Kermani et al. (2006).

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CHAPTER 1 INTRODUCTION

Coastal communities have experienced an increase of 39% in shoreline county

population from 1970 to 2010 (2012 NOAA). The increase in coastal population requires

a higher demand on infrastructure (e.g. homes, apartments, high rises, roads and

bridges). Coastal communities contribute nearly $6.6 trillion dollars or half of the gross

domestic product in the United States. As engineers strive to provide improved methods

and building materials for construction to mitigate damages arising from hurricane

episodes, composite materials have received greater attention. Composite material form

parts of a pre-engineered and modular building system originally developed for cladding

(Davies 1993), and are becoming more widespread in civil, aerospace, and automotive

applications (Schnabl 2007). There are many benefits for its current use in construction.

This innovative resource is stronger than conventional wood fibers and highly resistant

to mold, mildew, and decay. Composites provide the opportunity to remove organic

material from structural components of the home, (e.g loadbearing walls and floor

systems) and make them less vulnerable to natural decay. Another benefit is its energy

efficiency. The insulation is not interrupted by studs in the wall and closed-cell

polystyrene foams have a high R-value (Cathcart 1998).

This study focuses on the out-of-plane bending behavior and in-plane shear

resistance of the CSIP described in Vaidya (2010). The results bridge the knowledge

gap and augment prior work in the characterization of CSIP mechanical properties. us

to recreate such extreme events and quantify the behavior of such components.

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Scope of Research

The research objectives of this study are as follows:

1. Quantify the resistance for lateral nail loads, and temperature effects on CSIP thermal composite face-sheets

2. Design connection details for wall-to-foundation and wall-to-roof connections

3. Evaluates the performance of the composite panels under uniaxial bending

4. Evaluate the performance of the composite panels under shear in line with the wall

Organization of this Document

Chapter 2 provides the background to CSIP and current numerical methods for

evaluation of mechanical performance. Chapter 3 describes the experimental

methodology for structural testing and the significance of the data being collected.

Chapter 4 discusses the design and results of CSIP wall connection detail. Chapter 5

focuses on the results of the quasi static pressure loading and the time varying pressure

loading. Chapter 6 addresses the preliminary findings on shear wall behavior from

racking test. Chapter 7 concludes with recommendations for future research.

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CHAPTER 2 BACKGROUND

Composite structural insulated panels (CSIPs) are a derivative of sandwich

panels, which were first introduced into the consumer market in the form of structural

insulated panels (SIP) in 1951 (Cathcart 1998). SIPs gained popularity in the residential

construction industry due to their competitive material costs, energy efficiency, and a

decrease in the amount of time and labor required for construction. Pre-fabricated

panels allowed for wall assemblies to be brought in assembled and offer time saving

options such as electrical pre wiring, as well as rough opening for items such as glazing

and exterior finishes.

Options for SIP skin materials include oriented strand board (OSB), plywood,

gypsum wallboard, or wafer board. A SIP panel is usually termed a ‗composite‘

structural insulated panel (CSIP) if the face-sheet material is a thermoplastic, carbon

fiber, or e-glass. This chapter discusses light-wood frame construction and sandwich

panel construction. Sandwich panel construction will encompass both SIP panels and

CSIP panels.

Traditional Light Wood Frame Construction

Light wood frame construction has seen little to no change since the 1950s with

the introduction of plywood sheathing for light frame construction. Variation in lumber

properties provided a difficult material to produce standard prediction methods (1983

Gromola). Light frame wood walls presented a unique challenge to early researchers as

the varying lumber properties and indefinite combination made it cost prohibitive to test

every wall system. The development of computer based analysis in the early 1970s

made it possible to create analytical models that would allow for the prediction of infinite

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lumber combinations (1983 Gromola). Additional research demonstrated that a good

strength prediction for light frame wood walls was a series of composite I- joist. In his

early research, Polensek (1984) found that wall studs have the greatest effect on overall

wall capacities.

Applicable Standards

Current wood frame construction is governed by American Wood Council (AWC)

formerly ANSI / AF & PA. The standards designed focus on nail capacity as they have

been identified to be the weak point for connection to adequately transfer loads from

one member to another. Per AWC, Special Design provisions for wind and seismic

(SDPWS) wall capacity prior to design factors, for uniform load capacities (psf) for wall

sheathing resisting out of plane loads, are summarized in table 3.2.1. Sheathing

capacity is prescribed according to stud spacing, sheathing type and sheathing

thickness.

ASTM E 72 is used to conduct strength testing of panels for building

construction. ASTM E 72 p section 12 describes the method for the transverse loading

of a vertical wall with either a uniform pressure in a chamber or, a uniform load with a

bag or, loading the wall specimen at its quarter points. The significance of this testing is

to quantify the resistance of the wall subjected to out of plane loads. Section 14 of

ASTM E 72 refers to racking test for shear walls.

Prior Research

The forestry and paper group has been conducting and publishing research on wood

products as early as the 1970s. Several models presently exist to estimate the

capacities of wood wall.

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Sandwich Panels

Composite Beam Theory

The first approaches to composite beam theory were developed in the early 20th

century (e.g, Timoshenko 1921; Newmark 1951). Most studies assume linear elastic

behavior and perfect bonding between different layers to estimate mechanical behavior,

however, these assumptions are simplifications of complex behavior that was difficult to

quantify during this time period. Recent research on composite sandwich panels

includes Baehre (1994), Roberts (2002), Girhammar (2008a, 2008b, 2009), Manalo

(2010), Uddin (2010), Fam (2010), Vaidya (2010) and Mohammed (2011). Perhaps the

most accepted method to account for an imperfect bond can be found in Newmark

(1951); Girhammer and other researchers developed closed-form solutions with the

advancement of computer algorithms and technology. (Girhammer et al., 1993, 2008,

2009).

This analysis herein applies classical beam theory to benchmark results. Euler-

Bernoulli beam theory with a shear deformation term is shown to match the load

deflection relationship within an acceptable tolerance (5%). The closed form solution

developed by Allen (1969) Equation 2-1 and 2-2 appear to be good predictors of load

deflection relationship for uniaxial bending of CSIP panels. Ultimately Equations 2-3 and

2-4 were used to estimate deflection.

(2-1)

(2-2)

(

)

(2-3)

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(2-4)

Structural Insulated Panels

Since introduced in the 1950s, SIP research and development was primarily

done by private companies and most of the advancements were considered proprietary.

Figure 2-1 shows the cross-section of a typical SIP wall. SIP panels consist of a foam

core sandwiched between two wood fiber skins. The wood fiber skins are primarily

oriented strand board but are also made out of plywood, gypsum wallboard, or wafer

board. These materials are susceptible to organic decay and can foster various types of

mold if left unattended.

Composite structural Insulated Panels

The panels in this study (Figure 2-2) consist of a low-cost thermoplastics

orthotropic glass/ propylene (glass-PP) laminate exterior face-sheet and expanded

polystyrene foam (EPS) for the core material (Mousa 2010). With recent developments

in cost effective textile including, hot-melt impregnation, direct reinforced thermoplastics

(DRIFT), vacuum thermoforming, and long fiber thermoplastics (LFTs), it is now

possible to combine various high strain-energy fibers with a wide variety of

thermoplastic polymers to produce very low cost composite product, such as the

aforementioned test subject. Advantages of these CSIP panels include:

1. Faster construction: CSIPS can be constructed in one-third of the time of conventional light wood frame construction.

2. Environmental consciousness: The use of this product causes waste reduction and allows the recycling of any remaining material.

3. Design flexibility: These panels can be used for the construction of a simple storage building or even a large office building.

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4. High thermal performance: It maintains a high R-value ~3.85-5.50/in of thickness

5. Corrosion resistance: E-glass and EPS foam exhibit resistance to mold and corrosion.

CSIP construction can have a potential impact beyond the coastal United States.

Its low manufacturing cost and the ease of shipping worldwide make it an excellent

candidate to address some of the needs of many underdeveloped coastal communities.

Neither cost effective, nor fortified construction form part of the methodology for building

construction for many underdeveloped countries (Prevatt et al., 1994). As a result,

modular construction can have a positive impact by providing an alternative method of

construction and aid in mitigation of home loss in coastal communities around the world.

Limitations do exist for this type of composite assembly, which were highlighted

in the research conducted by Vaidya et al. (2010). He found that delamination occurred

between the foam and the exterior skin during axial loading of the wall assembly.

Similar results were observed in this study that applied uniaxial bending. Delamination

and its contribution to the findings of this research is further delineated in chapter 5

however it is important to note that delamination may have contributed to the nonlinear

strain behavior observed in the compression face-sheet.

Part of the research initiative was to quantify the performance characteristics of

such panels and compare test results to analytical results. A classical beam theory will

be applied to the analysis of the test results. This research applies closed form

composite beam theory approach.

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Figure 2-1. SIP wall anatomy

Figure 2-2. CSIP cross sectional illustration

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CHAPTER 3 EXPERIMENTAL DESIGN

The principal objective of this study was to develop a testing framework to

evaluate CSIP wall assemblies subjected to uniaxial bending caused by pressure

loading and in-plane shear transferred from the diaphragm to the foundation through the

shear wall. Table 3-1 provides a summary of CSIP panel inventory provided by UAB.

Table 3-2 identifies the testing matrix of the panels that will be subjected to uniaxial

bending caused by pressure loading and racking.

The study was conducted in three phases.

Phase one studied the interaction and failure modes of five different nail type fasteners (see Table 4-1), subjected to single shear to design the optimal connection.

Phase two subjected the completed wall assembly and connection to a pressure step loading function and a time-varying pressure sequence.

Phase three consisted of the preliminary investigation of shear resistance with two complete wall assemblies.

The pressure data was derived from wind load tests conducted on a model of a

low-rise rectangular building at the University of Western Ontario (UWO) Boundary

Layer Wind Tunnel. (Ho et al., 2003) The final stage of the research applied in-plane

shear loads to two wall assemblies using the racking procedure described in ASTM

E72. The connection details were identical to the bending test configuration.

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Table 3-1. CSIP Panel Inventory

Table 3-2. Testing Matrix Panel Type Test type A B C Sum Static 1 4 0 5 Dynamic step-loading 2 6 0 8 Racking 0 0 4 4

Total 17

Panel type Panel Dimension Core Density Panels #

A 139.7 x 1219.2 x 2438.4 mm

(5.5‖ x 4‘ x 8‘) 16.02 kg/m3 (1 pcf) 4

B 139.7 x 1219.2 x 2438.4 mm

(5.5‖ x 4‘ x 8‘) 48.05 kg/m3 (3 pcf) 11

C 254.0 x 1219.2 x 2438.4 mm

(10‖ x 4‘ x 8‘) 48.05 kg/m3 (3 pcf) 8

D 139.7 x 1219.2 x 1828.8 mm

(5.5‖ x 4‘ x 6‘) 48.05 kg/m3 (3 pcf) 1

E 254.0 x 1219.2 x 2438.4 mm

(10‖ x 4‘ x 8‘) 48.05 kg/m3 (3 pcf) 1

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CHAPTER 4 DESIGN AND EVALUATION OF CSIP WALL CONNECTION

The objective of this phase was to design an easily constructible connection

detail for the implementation in the field as depicted in Figure 4-1. Ease of construction

will help to promote the use of such panels in under developed regions.

The lateral capacities of five nail type fasteners, presented in Table 4-1, were

quantified using a modified lateral resistance ASTM D 1761 test performed on a Tinius

Olson 400 Super ―L‖ Hydraulic Test Machine. Thermoplastic material constitutive

properties are temperature dependent, thus face-sheets were tested at two ambient

temperatures: 21.1˚C and 32.2˚C (70˚F, 90˚F). ASTM D 1761 loading rates were

modified to 30-40 times faster than prescribed to minimize temperature effects on

cooling of the face-sheets. The thermoplastic composite face-sheets were first

separated from the foam core and cut into 38.1 cm x 8.8 cm (15 in x 3.5 in) specimens,

then stored in a temperature controlled room. Samples were assembled in two stages.

Stage one prepared a southern yellow pine (SYP) 2 x 4 on edge with a steel bar at one

end. Stage two, immediately preceded testing, attached a face-sheet specimen to the

opposite end of the SYP 2 x 4 with a single fastener. The single fastener was driven in

by a Bostitch Magnesium Model No. F21PL nail gun 620 at 53 kPa (90 psi). The Bostich

nail gun was calibrated to a pressure that set the fastener flush. The modified ASTM D

1761 loading was required to maintain the face-sheets at prescribed temperature for the

duration of the test with surface cooling kept to less than 0.9 ˚C (0.5 ˚F).

Figure 4- shows a photo of a sample and an illustration of the individual

components of the test sample. Figure 4-3 and Figure 4-4 provide a summary of the

initial test conducted to aid in the selection of a fastener that would provide the greatest

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lateral resistance. A single fastener was chosen based on the results. Thirty additional

tests were performed on the chosen fastener to quantify dependency on the lateral

capacity as a function of specific gravity and moisture content. Specific gravity and

moisture content were obtained using ASTM standards, ASTM 2395 and ASTM 4442

respectively. From each of the samples tested multiple sections of timber member were

taken and evaluated for specific gravity and moisture content and then recorded. This

provided a direct comparison to NDS lateral capacity of sheathing to main members.

Connection Testing Results: Tests were performed under two temperatures:

21.1˚C (70˚F) and 32.2˚C (90˚F), and a student‘s t-test was performed to compare the

results (Table 4-2). All but one fastener failed to reject the null hypothesis, which

indicates that temperature did not play a significant role in the determination of the

lateral capacity of a face-sheet attached with a single nail. The only nail that failed to

reject the null hypothesis was B-RS-8d, which is a ring shank common 8d nail. Figure 4-

4 groups the results per effective area. All of the fasteners were found to be suitable for

assembling the CSIP systems. The stainless steel ring shank 6d common nail (SST-SS)

was selected for its resistance to rusting in corrosive coastal environments.

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Figure 4-1. Proposed construction assembly

Figure 4-2. Lateral resistance testing. Photo courtesy of George Fernandez, University

of Florida.

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Figure 4-3. Lateral capacities of nail fasteners

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Figure 4-4. Lateral capacities stratified by effective area

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Table 4-1. Fastener summary

ID Shank Shank diameter Head diameter Shank length Aeff

mm in mm in mm in mm2 in2

A-S Smooth 3.33 0.131 7.19 0.283 63.50 2.500 31.612 0.049

B-RS Ring 3.33 0.113 6.99 0.275 60.33 2.375 31.612 0.049

C-S Smooth 3.33 0.113 7.19 0.283 50.80 2.000 34.193 0.053

SST-RS Ring 3.33 0.113 6.99 0.275 50.80 2.000 31.612 0.049

SST-SS Spiral 3.33 0.113 6.71 0.264 50.80 2.000 29.032 0.045

Table 4-2. T-test results for single fastener at two different temperatures

Paired test 32.22⁰C

A-S-8d B-RS-8d C-S-6d SST-SS-6d SST-RS-6d

21.1

1⁰C

A-S-8d 0

B-RS-8d 1

C-S-6d 0

SST-SS-6d 0

SST-RS-6d 0

0=Failed to reject null hypothesis

1=Rejected null hypothesis

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CHAPTER 5 EVALUATION OF CSIPS WALL ASSEMBLY SUBJECTED TO WIND PRESSURE

LOADING

Phase two experiments used the High Airflow Pressure Loading Actuator

(HAPLA Figure 5-1 A), which is based on the Pressure Loading Actuator system (PLA)

developed by UWO (Kopp et al., 2010). This system was used to apply time-varying

pressure to surfaces of buildings and other structures. The HAPLA consists of two 75

hp centrifugal blowers connected to a valve with a rotating central disk actuated by a

servo motor. The servo controls the disk‘s position, which in turn regulates the system

pressure with a three chamber design. Custom LabVIEW 8.5 software operating on a

National Instruments PXI system, controls the pressure in the chamber through a 100

Hz PID loop that receives feedback from an Ashcroft XLdp transducer attached to the

test chamber. Currently, the HAPLA can simulate up to a 3Hz sinusoidal waveform and

a peak pressure of ±7 kPa. Time-varying pressure sequences with the HAPLA are

limited to frequency components as high as 2Hz in the target pressure time history. Mid-

span deflections were recorded with a Balluff BOD63M photoelectric distance sensor.

The reaction frame consisted of two similar attachment points to represent the

floor and roof connection seen in Figure 4-1. Complete test assembly walls were

instrumented with six TML model PFL-30-11-3L strain gauges on the exterior face-

sheets. Additionally, three were installed on the compression face and three on the

tension face at the third points along the mid-section of the wall, as illustrated on Figure

5-2. Figure 5-3 is a detail for both the top and bottom connection for the out of plane test

frame.

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Pressure step loading function

The step loading pressure time history was applied to determine the peak static

load at failure (Figure 5-4). The function was generated using an initial pressure of 0.24

kPa (5 psf) and increasing by 0.48 kPa (10 psf) up to 6.96 kPa (145 psf) with duration of

ninety seconds per pressure step. The pressures were chosen based on the capabilities

of the system. Table 5-1 shows the fifteen unique pressures tabulated in the center

column, the right column was determined by solving for the equivalent design wind

speed based on ASCE7-10.

Equation 5-1 from section 27.3.2 ASCE 7-10 Main Wind Force Resisting System

(MWFRS) envelope was used to find the equivalent wind velocity for the static pressure

step. This equation required certain assumptions to be made about the velocity

pressure coefficient, topographic factors, and the wind directionality factor. The

equivalent basic wind speeds are presented in Table 5-1.

qz 0.000256* z* zt d*v

2 (5-1)

Individual Test Results Static Step Loading 48.05 kg/m3 (3 pcf)

Test #1

Test one demonstrated the need for adjustment to the PID parameters at loads

greater than 3.60 kPa for subsequent test. Figure 5-5 is a time history plot presenting a

target and measured pressure sequence for visual comparison. This figure shows that

the PID parameters were not correctly calibrated above 2.5 kPa pressure target. Figure

5-6 represents the deflection time history for this test. The specimen was still able to

obtain a max pressure of 6.45 kPa. Figure 5-7 is a sketch of the de-bonding that was

observed at the conclusion of the test. The large de-bonding that was observed on the

bottom of the panel‘s interior factsheet was not caused by mechanical failure and can

34

be attributed to manufacturing error. The top timber split longitudinally into three

segments however, de-bonding between the top section of the interior face-sheet was

measured to be less than the bottom where the connection remained without fracture.

Though the ultimate load of the system was approximately 6.45 kPa, the plot on

Figure 5-9 shows the limit state was exceeded at approximately at 1 kPa. The blue line

represents a deflection limit state of L/180. This pressure corresponds to a wind speed

between 40 and 51 m/s (90 and 100 mph). The theoretical deflection was validated with

the data collected as can be seen on Figure 5-9. Figure 5-9 confirms the equation used

accurately predicted the mid-span deflection.

The strain profile exhibit a linear behavior up to approximately 2 kPa when they

begin to show nonlinear trends. The center strain gauge SG5 on the tension face

reported the highest strain, as expected, and SG2 on the compression face had the

largest compression strains. The panel, however, was not performing as a perfectly

bonded composite beam evidenced by the unequal opposite strains. At 3 kPa the

compression strain gauges begin to lose their compression, leading the author to

conclude the face-sheet is slipping from the core and no longer behaving as an ideal

composite system.

Test #2

Test two pressure sequence demonstrates the corrections to the PID parameters

have improved the tracking of the system to the pressure sequence. Figure 5-10

presents a target and measure pressure sequence. Figure 5-11 represents the

deflection time history for this test. Failure is evident at approximately 4.6 kPa with a

sudden drop in the measure pressure; at this point failure of the top timber plate

occurred. Figure 5-12 is a sketch of the de-bonding that was observed at the end of the

35

testing. Based on the failure, it was difficult to quantify the de-bonding along the inside

face.


Figure 5-13 shows the limit state was exceeded approximately at 1 kPa. The blue line

represents a deflection limit state of L/180. This pressure corresponds to a wind speed

between 40 and 51 m/s (90 and 100 mph). Nonetheless the theoretical deflection was

substantiated by the data, as shown in Figure 5-13. As with the initial test, Figure 5-13

validates the equation used does predict the mid-span deflection accurately.

The strain profile exhibited linear behavior up to approximately 3.5 kPa on the

tension face and SG5 and 2 kPa for the compression face SG2 just before failure when

they begin to show nonlinear trends. As anticipated, the largest strains for both the

tension and compression face were located at the center with SG5 on the tension face

and SG2 on the compression face. The unequal opposite strains prove the panel is not

behaving as a perfectly bonded composite beam. At 2.5 kPa the compression strain

gauges begin to lose their compression, which suggests the face-sheet is slipping from

the core and no longer behaving as an ideal composite system.

Test #3

Maintaining the same PID parameters from test two, the HAPLA was able to

maintain the accurate pressure throughout the fifteen different pressure steps. Figure 5-

14 presents a target and measure pressure sequence. The panel and timber

connections were exposed to all fifteen quasi static pressure steps reaching an ultimate

pressure of approximately 6.9 kPa without failure. Figure 5-15 shows the deflection time

history for this test. Figure 5-16 depicts the de-bonding. At the completion of the

36

pressure test, the panel was examined for de-bonding and the inside bottom left corner

showed no signs of de-bonding between the face-sheets and the foam core.

The limit state was exceeded at approximately at 1.5 kPa and that the ultimate

pressure was 6.9 kPa (Figure 5-17). The blue line represents a deflection limit state of

L/180. This pressure corresponds to a wind speed between 40 and 51 m/s (90 and 100

mph). However the theoretical deflection in this test overestimated the actual deflection

as can be seen in the plot on Figure 5-17. This plot also shows the wall system

deflection not behaving linearly with pressure in contrast to the other tests described in

this section.

The strain profile exhibited linear behavior up to approximately 3.5 kPa on the

tension face with SG5 and 2 kPa for the compression face with SG2 just before failure,

which is when they begin to show nonlinear trends. As expected, the center strain

gauge SG5 on the tension face reported the highest strain, yet the SG2 on the

compression face had the largest compression strains. The panel however is not

behaving as a perfectly bonded composite beam and is evident with the unequal

opposite strains. At 2.5 kPa the compression strain gauges begin to lose their

compression strain which leads the author to believe the face-sheet is slipping from the

core and no longer behaving as an ideal composite system.

Test #4


maintain the accurate pressure throughout the eleven different pressure stages. The

pressure sequence shown in Figure 5-18 depicts the target and the measured pressure

sequences. The panel and timber connections were able to withstand all fifteen quasi

static pressure steps and failed at the eleventh stage of the pressure sequence. Figure

37

5-19 shows the deflection time history. This panel did not have data for de-bonding at

the conclusion of testing.


Figure 5-20 shows the limit state was exceeded approximately at 1 kPa, indicated by

the blue line. The blue line represents a deflection limit state of L/180. This pressure

corresponds to a wind speed between 40 and 51 m/s (90 and 100 mph). The theoretical

deflection in this test was an accurate predictor of the actual deflection, as can be seen

in the plot on Figure 5-20. This plot also shows the theoretical deflection is

underestimating the true wall system deflection.

The strain profile exhibited linear behavior up to approximately 3 kPa on the

tension face and SG5 and 2 kPa for the compression face SG2 when they begin to

show nonlinear trends. The center strain gauge SG5 on the tension face reported the

highest strain, which was expected, and SG2 on the compression face had the largest

compression strains. The panel did not behave as a perfectly bonded composite beam

as proven by the unequal opposite strains. At 2.5 kPa the compression strain gauges

begin to lose their compression strain, leading the author to believe the face-sheet is

slipping from the core and no longer behaves as an ideal composite system.

Individual Test Results Static Step Loading 16.02 kg/m3 (1 pcf)

Test #1


maintain the accurate pressure throughout the ten different pressure stages. The

pressure sequence on Figure 5-21 presents a target and the measured pressure

sequence for panel test number one.The measured pressure sequence begins to show

evidence of not achieving the target pressure at the fifth pressure step. The panel and

38

timber failed at the eleventh stage of the pressure sequence. Figure 5-22 represents the

deflection time history for this test. Figure 5-23 is a sketch of the de-bonding that results

at the end of the testing. At the completion of the pressure test the panel was examined

for de-bonding. Separation of the wall assembly from the timber connection hindered

the ability to collect de-bonding data.


Figure 5-25 shows the limit state, which is the blue line, was exceeded approximately at

1 kPa. The blue line represents a deflection limit state of L/180. This pressure

corresponds to a wind speed between 40 and 51 m/s (90 and 100 mph). The theoretical

deflection in this test was an accurate predictor of the actual deflection as can be seen

in the plot on Figure 5-25. This plot also shows the theoretical deflection is under

estimating the true wall system deflection.

The strain profile exhibited linear behavior up to approximately 3 kPa on the

tension face and SG5 and 2 kPa for the compression face SG2 when they begin to

show nonlinear trends. The center strain gauge SG5 on the tension face reported the

highest strain, which was expected, and SG2 on the compression face had the largest

compression strains. The panel however is not behaving as a perfectly bonded

composite beam and is evident with the unequal opposite strains.

Time-varying pressure sequence

The time varying pressure sequence was derived from a ‗worst case‘ scenario on

a 12.19 m W x 19.05 m L x 7.32 m H (40 ft W x 62.5 ft L x 24 ft H) building in the NIST

Aerodynamic Database (Ho et al., 2003). The NIST database provides time histories of

Cp values for all taps from a particular wind tunnel model along with other prudent

information. For the time-varying pressure sequence the Cp values taken from the NIST

39

database must be converted from model scale to full scale values using the reduced

frequency relationship Equation 5-2, f is the frequency of the data, l is the integral length

scale, U is the mean wind speed. Equation 5-3 was used to obtain the full-scale

pressure time history from converted Cp time history.

(fl

U)model

(fl

U)full-scale

(5-2)

P(t) 1

2 U̅

2Cp(t) (5-3)

Each segment was filtered to 2 Hz using a low pass filter to improve

controllability. The mean of the record was increased by 10% to account for internal

pressurization (1994 Vickery). For this pressure sequence, segments of full records

were concatenated to form a full record length of 10394 sec (173.2 min). The basic wind

speed was incremented in steps of 4.47 m/s beginning with 44.7 m/s, a total of eleven

basic wind speeds were used to formulate the pressure sequence. Mechanical

limitations of the HAPLA prevented peak pressure in stage 11 from being achieved;

Figure 5-26 is a full-time history of the target pressure. Figure 5-27 is a narrow segment

of time to show the reduction in peak pressure gain and the fidelity of the HAPLA. Table

5-2 show the basic wind speed used with Equation 5-2 to compute the pressure time

history. The mean pressure in Table 5-2 is the measured mean pressure from the data

recorded.

Individual Test Results Dynamic Loading 48.05 kg/m3 (3 pcf)

Test #1

The pressure sequence in the following figure presents the data that was

recorded from subjecting the CSIP panel to the time varying pressure sequence. The

plot on Figure 5-28 is the target and measured pressure vs. time. The HAPLA system

40

was unsuccessful at achieving the higher peaks on the final stage of the sequence,

however, the system was able to reproduce smaller amplitude fluctuations with

accuracy. Figure 5-29 is the displacement vs. time; this plot has a disjunction in the data

at approximately the 7500 second mark due to the movement of the displacement

traducer for safety reasons.

Figure 5-30 shows the deflection vs. pressure relationship. The red line

represents the theoretical equation previously used in the quasi static pressure results

plots. The blue line once again represents the deflection limit state of L/180 for light

wood frame construction. Equation 2-4 was an accurate predictor of the mean deflection

for this CSIP wall. The limit state line, unlike that of the static walls, is exceeded at

approximately 0.4 kPa. Figure 5-31 is a sketch of the de-bonding and failure observed

after the pressure sequence was completed and the wall removed from the test frame.

Test #1 had no visual de-bonding at the conclusion of the test and both the top and

bottom plate remain undamaged.

Test #2

The pressure sequence in Figure 5-32 presents the data that was recorded from

subjecting the second CSIP panel to the same time varying pressure sequence

described in the previous chapter. The plot on Figure 5-32 is the target and measured

pressure vs. time. The HAPLA system was unsuccessful at achieving the higher peaks

on the final stage of the sequence, however the system was able to reproduce smaller

amplitude fluctuation with accuracy. Figure 5-33 is the displacement vs. time, this plot

has a disjunction in the data at approximately the 10,500 second mark, due to a large

movement of the wall assembly. Inspection after completion of the sequence yielded no

visual evidence for failure and timber connection remained intact.

41



plots. The blue line again represents the deflection limit state of L/180 for light wood

frame construction. Equation 2-4 was an accurate predictor of the mean deflection for

this CSIP wall, yet it slightly over predicts loads below 1.4 kPa and under predicts

deflection for higher loads. The limit state line, unlike that of the static walls, is exceeded

at just above 0.4 kPa based on the theoretical deflection line and at 0.6 kPa based on

the measured data. Figure 5-35 is a sketch of the de-bonding and failure observed after

the pressure sequence was completed and the wall removed from the test frame. Test

#2 had no visual de-bonding at the conclusion of the test and both the top and bottom

plate remain undamaged.

Test #3


subjecting the third CSIP panel to the same time varying pressure sequence described

in this chapter. The plot on Figure 5-36 is the target and measured pressure vs. time.

The HAPLA system was unsuccessful at achieving the higher peaks on the final stage

of the sequence, however the system was able to reproduce smaller amplitude

fluctuation with accuracy. Figure 5-37 is a plot of the displacement vs. time. This plot

has a jump in the data at approximately 10,000 seconds. After inspection of the wall

assembly, at the completion of the sequence, the cause of the discontinuity was partial

cracking of the bottom timber plate.

Figure 5-38 plots the deflection vs. pressure. The red line represents the

theoretical equation previously used in the quasi static pressure results plots. The blue

line represents the deflection limit state of L/180 for light wood frame construction.

42

Equation 2-4 was an accurate predictor of the mean deflection for this CSIP wall, yet it

slightly over predicts loads below 1.4 kPa and under predicts deflection for higher loads.

The limit state line, unlike that of the static walls, is exceeded at just above 0.4 kPa

based on the theoretical deflection line and at 0.6 kPa based on the measured data.

Figure 5-39 is a sketch of the de-bonding and failure observed after the pressure

sequence was completed and the wall removed from the test frame. Test #3 had no

visual de-bonding at the conclusion of the test and only the top plate remained

undamaged. The bottom plate had visual evidence of partial cracking.

Test #4


subjecting the fourth CSIP panel to the same time varying pressure sequence described


The HAPLA system was unsuccessful at achieving the higher peaks on the final stage

of the sequence, however the system was able to reproduce smaller amplitude

fluctuation with accuracy. Figure 5-41 is the displacement vs. time. This plot shows that

the system exhibits a non-linear behavior at lower loads that was not seen in previous

test. This change in slope on Figure 5-41 indicates a change in the load deflection

response because it is occurring during the fourth repetition of the final stage segment.



plots. The blue line represents the deflection limit state of L/180 for light wood frame

construction. Equation 2-4 was an accurate predictor of the mean deflection for this

CSIP wall, there was an over prediction of loads below 1.4 kPa and under prediction of

deflection for loads higher than 1.4 kPa. The limit state line, unlike that of the static

43

walls, is exceeded at just above 0.4 kPa based on the theoretical deflection line and at

0.6 kPa based on the data. Figure 5-43 is a sketch of the de-bonding and failure

observed after the pressure sequence was completed and the wall removed from the

test frame. Test #4 had no visual de-bonding at the conclusion of the test and only the

top plate was damaged with visual evidence of partial cracking.

Test #5


subjecting the fifth CSIP panel to the same time varying pressure sequence described


This wall sample was successful sustaining loads until the eleventh stage, but only

completed two repetitions of the stage before failing. Figure 5-45, which is the deflection

vs. time plot, illustrates at approximately 5000 seconds there was either some de-

bonding or failure based on the CSIP walls deflection response.





CSIP wall. It slightly over predicts loads below 1.4 kPa and under predicts deflection for

higher loads. The limit state line, unlike that of the static walls, is exceeded at just above

0.4 kPa based on the theoretical deflection line and at 0.6 kPa based on the data.


sequence was completed and the wall removed from the test frame. Test #5 had no

visual de-bonding at the conclusion of the test and neither the top plate nor bottom plate

had any visual signs of damage.

44

Test #6

The pressure sequence in Figure 5-48 presents the data that was recorded after

subjecting the sixth CSIP panel to the same time varying pressure sequence described

in the previous chapter. The plot on Figure 5-48 is the target and measured pressure vs.

time. This wall sample was successful sustaining loads through the sixteenth stage

before failing. Figure 5-49, which is the deflection vs. time plot, illustrates at

approximately 5,000 seconds and 9,000 seconds that there was some form of either de-

bonding or failure based on the CSIP walls deflection response.





CSIP wall. It does over predict for loads below 1.4 kPa and under predicts deflection for

higher loads. The limit state line, unlike that of the static walls, is exceeded at just above

0.4 kPa based on the theoretical deflection line and at 0.6 kPa based on the data.


sequence was completed and the wall removed from the test frame. Test number six

had visual de-bonding on the top of the inside face-sheet. At the conclusion of the test

the top plate had no signs of damage, but the bottom plate had a partial crack as a

visual sign of damage.

Individual Test Results Dynamic Loading 16.02 kg/m3 (1 pcf)

Test #1



45


time. This wall sample successfully sustained loads through the seventh stage before

failing. Figure 5-53, the deflection vs. time plot, illustrates at approximately 5500

seconds there was some form of either de-bonding or failure based on the CSIP walls

deflection response.





CSIP wall; it under predicts loads above 0.5 kPa. The limit state line, unlike that of the

static walls, is exceeded at just above 0.5 kPa as per the theoretical equation and the

measured data. Figure 5-55 is a sketch of the de-bonding and failure observed after the

pressure sequence was completed and the wall removed from the test frame. Test

number one of the light core density did show visual de-bonding on the bottom of the

inside face-sheet and the top right of the outer face-sheet. At the conclusion of the test,

the top plate had no signs of damage but the bottom plate was damaged in the process

of removal from the test frame. As a result, it could not be determined whether it was a

partial crack or a full failure of the member.

Test #2




time. This wall sample was successful sustaining loads through the eighth stage before

failing. Figure 5-57, which is the deflection vs. time plot, illustrates at approximately

46

6,000 seconds there was some form of either de-bonding or failure based on the CSIP

walls deflection response.




construction. Equation 2-4 was not an accurate predictor of the mean deflection for this

CSIP wall. The limit state line, unlike that of the static walls, is exceeded at just above

0.4 kPa based on the theoretical deflection line and the data. Figure 5-59 is a sketch of

the de-bonding and failure observed after the pressure sequence was completed and

the wall removed from the test frame. Test number two of the light core density did

show visual de-bonding on the bottom of the inside face-sheet and the top of the outer

face-sheet. At the conclusion of the test, the top plate had partial cracking but the

bottom plate was damaged and had complete failure.

Summary of Pressure Loading Results

The pressure step loading sequence provided a reference for load deflection

relationship for a complete wall assembly and verification of theoretical equations

presented in Equation 2-4. A total of five CSIP wall assemblies were tested, by

subjecting them to the pressure step load sequence. The results of the five CSIP walls

are given in Table 5-3 and Table 5-4 for the 16.02 kg/m3 (1 pcf) and four 48.05 kg/m3

(3pcf) wall assemblies. The plots on Figures 5-55 and 5-56 indicate the summary of the

load vs. deflection data for each of the two density groups tested with the step pressure

loading sequence. The summary results show that the wall assemblies have a linear

relationship between load and deflection. The solid line was computed using Eq. 2.

Though currently only prudent to the state of Florida, both the International Residential

47

Code (IRC 2009) and Florida Building Code (FBC 2010) Section R613 makes reference

to max deflection of SIP type walls to be L/254. The blue line presented in chapter five

corresponded to a deflection limit state of L/180 for standard light wood frame stud

walls. It was determined from analyzing the load deflection data that the mid-span

deflection was exceeded at a pressure load of 0.72 kPa and 1 kPa which correspond to

the L/254 and L/180 deflection limit state respectively.

When analyzing the strain data, it was observed, as shown in Figure 5-9, Figure

5-13, Figure 5-17, Figure 5-20, and Figure 5-25, - a strain vs. load plot, that the

compressive strain exhibits a form of strain release. This type of behavior was also

observed in research performed by Roberts et al. (2002). This strain behavior was

observed in all tested panels, with some being more prominent than others. This strain

behavior has a possibility indicative of active de-bonding. When de-bonding initiates it

would cause the compressive sheet to alter its behavior from a composite material to a

single membrane in tension. Figure 5-62 presents four photographs of failures observed

during testing. Within both parts of phase two all but one wall assembly did not fail.

Failure was primarily observed in the connection plates with splitting of the timber

parallel to grain.

Morrison (2011) conducted a study focused on fasteners in wood that

emphasized the importance of understanding a) the ultimate capacity under static

loading and b) the failure load under cyclic loading. This study conducted tests similar to

those described by Morrison et al. (2011). The results exhibit a decrease of

approximately 70% in the capacity of the CSIP panel subjected to time varying ―realistic‖

loading rather than static loading conditions, even though average peak loads reflected

48

a lower difference of approximately 26%. Figure 5-63 is a load vs. deflection plot of one

test with minimal filtering that shows a high variability, making it difficult to predict the

dynamic behavior. However, as shown in the individual results discussion, with limited

filtering it is possible to predict mean deflection vs mean pressure per stage of the

dynamic sequence. Figure 5-64 is a summary of both 48.05 kg/m3 (3 pcf) and 16.02

kg/m3 (1 pcf) CSIP wall subjected to the dynamic pressure sequence. It was observed

that the wall, although flexible, had difficulty returning to a natural state after load was

removed. Therefore, it is concluded that this scatter is difficult to predict because current

equation used do not take previous conditions into consideration. It could be possible to

correct some uncertainty using a coefficient of restitution to account for some of the

variability. Results shown in Figure 5-65 also suggest that shear deformation in the core

may have a larger influence in dynamic loading.

As first introduced with the pressure step-loading, the strain behavior may be a

sign of de-bonding (not visible during testing). Figure 5-65 is a representation of similar

behavior observed on all CSIP walls subjected to dynamic loading. It demonstrates that

while tensile behavior is linear with regard to applied load, mid-span strain compression

does not follow any particular pattern and almost demonstrates a plateau effect at

approximately 100 micro strains.

Comparison of Capacity and Failure Modes

Table 5-3 tabulates the results for the maximum pressure through the duration of

a specific test and provides a mean with one standard deviation. The maximum

pressure a 48.05 kg/m3 (3 pcf) and a16.02 kg/m3 (1 pcf) CSIP panel was able to resist

was 6.90 kPa 5.05 kPa, respectively, during the Pressure step loading sequence. As

49

per the results, prior to failure during the dynamic pressure sequence, the mean

maximum pressure for both core densities was approximately 25% less than the mean

maximum measured pressure observed in the step loading, whose mean was 5.71 kPa

compared to 4.21 kPa. Table 5-4 provides a summary of the maximum deflection and

compares the results and means of both the step loading test and the dynamic test.

When comparing the mean max deflection between step loading and dynamic test

results, we find a difference of approximately 30%.

50

Figure 5-1. Two photographs of the pressure testing components A) HAPLA testing

apparatus B) exterior view of testing chamber. Photo courtesy of George Fernandez and Forrest Masters, University of Florida.

51

Figure 5-2. Strain gauge location

Figure 5-3. Reaction frame connection detail

52

Figure 5-4. Pressure step loading function

Figure 5-5. 48.05 kg/m3 (3 pcf) CSIP Test 1 pressure time history

0 200 400 600 800 1000 12000

1

2

3

4

5

6

7

Time (Seconds)

Pre

ssu

re (

KP

a)

Target

Measured

53

Figure 5-6. 48.05 kg/m3 (3 pcf) CSIP Test 1 deflection time history

Figure 5-7. 48.05 kg/m3 (3 pcf) CSIP Test 1 de-bonding and failure sketch

0 200 400 600 800 1000 1200

10

20

30

40

50

60

70

80

90

100

110

Time (Seconds)

Deflection (

mm

)

CSIP Static -06-2011

T cf.t

54

Figure 5-8. 48.05 kg/m3 (3 pcf) CSIP Test 1 failure. Photo courtesy of George Fernandez, University of Florida.

Figure 5-9. 48.05 kg/m3 (3 pcf) CSIP Test 1 summary

55



0 100 200 300 400 500 600 700 8000

1

2

3

4

5

Time (Seconds)

Pre

ssu

re (

KP

a)

Target

Measured

0 100 200 300 400 500 600 700 800

10

20

30

40

50

60

70

80

90

100

110

Time (Seconds)

Deflection (

mm

)


T cf.t

56



57



0 200 400 600 800 1000 1200 14000

1

2

3

4

5

6

7

Time (Seconds)

Pre

ssu

re (

KP

a)

Target

Measured

0 200 400 600 800 1000 1200

10

20

30

40

50

60

70

80

90

100

110

Time (Seconds)

Deflection (

mm

)


T cf.t

58



59



0 100 200 300 400 500 600 700 800 9000

1

2

3

4

5

6

Time (Seconds)

Pre

ssu

re (

KP

a)

Target

Measured

0 100 200 300 400 500 600 700 800 900

10

20

30

40

50

60

70

80

90

100

110

Time (Seconds)

Deflection (

mm

)


T cf.t

60



0 100 200 300 400 500 600 700 800 9000

1

2

3

4

5

6

Time (Seconds)

Pre

ssu

re (

KP

a)

Target

Measured

61



0 100 200 300 400 500 600 700 800 900

10

20

30

40

50

60

70

80

90

100

110

Time (Seconds)

Deflection (

mm

)


T cf.t

62

Figure 5-24. 16.02 kg/m3 (1 pcf) CSIP Test 1 failure. Photo courtesy of George

Fernandez, University of Florida.


63

Figure 5-26. Complete time-varying pressure sequence

Figure 5-27. Sample of the time-varying pressure sequence

64

Figure 5-28. 48.05 kg/m3 (3 pcf) CSIP Test 1 time varying pressure time history

Figure 5-29. 48.05 kg/m3 (3 pcf) CSIP Test 1 time varying pressure deflection time

history

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000

1

2

3

4

5

6

Time (Seconds)

Pre

ssu

re (

KP

a)

CSIP Dynamic 09-12-2011 3pcf

Target

Measured

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000

10

20

30

40

50

60

70

80

90

100

Time (Seconds)

Def

lect

ion

(m

m)


Measured

65

Figure 5-30. 48.05 kg/m3 (3 pcf) CSIP Test 1 time varying pressure deflection-load plot


0 10 20 30 40 50 60 70 80 90 1000

0.5

1

1.5

2

2.5P

ress

ure

(K

Pa)

Deflection (mm)


Experimental

Theoretical Deflection

66



history

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000

1

2

3

4

5

6

Time (Seconds)

Pre

ssu

re (

KP

a)CSIP Dynamic 09-21-2011 3pcf

Target

Measured

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000

20

40

60

80

100

120

140

Time (Seconds)

Def

lect

ion

(m

m)


Target

67



0 20 40 60 80 100 1200

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2P

ress

ure

(K

Pa)

Deflection (mm)


Experimental


68



history

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000

1

2

3

4

5

6

Time (Seconds)

Pre

ssu

re (

KP


Target

Measured

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000

10

20

30

40

50

60

70

80

Time (Seconds)

Def

lect

ion

(m

m)


Target

69



0 10 20 30 40 50 60 700

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2P

ress

ure

(K

Pa)

Deflection (mm)


Experimental


70



history

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000

1

2

3

4

5

6

Time (Seconds)

Pre

ssu

re (

KP

a)


Target

Measured

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000

5

10

15

20

25

30

35

40

Time (Seconds)

Def

lect

ion

(m

m)


Target

71



0 5 10 15 20 25 30 350

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2P

ress

ure

(K

Pa)

Deflection (mm)


Experimental


72



history

0 1000 2000 3000 4000 5000 6000 7000 8000 90000

1

2

3

4

5

6

Time (Seconds)

Pre

ssu

re (

KP

a)


Target

Measured

0 1000 2000 3000 4000 5000 6000 7000 8000 90000

10

20

30

40

50

60

70

Time (Seconds)

Def

lect

ion

(m

m)


Measured

73



0 10 20 30 40 500

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2P

ress

ure

(K

Pa)

Deflection (mm)


Experimental


74



history

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Figure 5-60. Deflection-load results for the 16.02 kg/m3 (1 pcf) panels

Figure 5-61. Deflection-load results for the 48.05 kg/m3 (3 pcf) panels

81

Figure 5-62. Observed damage. Photo courtesy of George Fernandez, University of

Florida.

Figure 5-63. Un-filtered mid-span deflection versus pressure

0 10 20 30 40 50 60 70 80 90 1000

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Figure 5-64. Filtered mid-span deflection versus pressure

Figure 5-65. Time-varying pressure vs. mid-span strain

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Table 5-1. Static pressure step and equivalent mean wind speed Step # Mean Pressure kPa (psf) Mean Wind Velocity m/s (mph)

1 0.24 (5) 23.24 (52) 2 0.72 (15) 40.23 (90) 3 1.20 (25) 51.85 (116) 4 1.68 (35) 61.24 (137) 5 2.16 (45) 69.73 (156) 6 2.64 (55) 76.89 (172) 7 3.12 (65) 83.59 (187) 8 3.60 (75) 89.85 (201) 9 4.08 (85) 95.66 (214)

10 4.56 (95) 101.03 (226) 11 5.04 (105) 106.39 (238) 12 5.52 (115) 111.31 (249) 13 6.00 (125) 115.78 (259) 14 6.48 (135) 120.70 (270) 15 6.96 (145) 125.17 (280)

Table 5-2. Time varying basic wind speed and mean pressure Step # Basic Wind Velocity m/s (mph) Mean Pressure kPa (psf)

1 44.71 (100) 0.409 (8.5) 2 49.17 (110) 0.496 (10.4) 3 53.69 (120) 0.593 (12.4) 4 58.11 (130) 0.697 (14.5) 5 62.58 (140) 0.811 (16.9) 6 67.05 (150) 0.933 (19.48) 7 71.52 (160) 1.064 (22.22) 8 75.99 (170) 1.204 (25.24 9 80.46 (180) 1.352 (28.23)

10 84.93 (190) 1.509 (31.51) 11-16 89.40 (200) 1.675 (34.98)

Table 5-3. Maximum pressure comparison table Foam core density

Maximum step loading pressure (kPa) Maximum dynamic pressure (kPa) Sample Mean ± Std Sample Mean ± Std

48.05 kg/m3 (3 pcf)

6.45

5.71 ± 1.13

4.42

4.21 ± 0.28

4.60 4.63

6.90 4.22 4.90 3.89

--- 4.13 --- 3.96

16.02 kg/m3 (1 pcf)

5.05 5.05

3.78 3.81

--- 3.84

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Table 5-4. Maximum deflection table Foam core density

Maximum quasi-steady deflection (mm) Maximum dynamic deflection (mm) Sample Mean ± Std Sample Mean ± Std

48.05 kg/m3 (3 pcf)

101.0

90.4 ± 22.2

53.0

62.1 ± 17.1

64.0 77.1 114.7 69.8

81.9 36.4

--- 55.0

--- 81.5

16.02 kg/m3 (1 pcf)

95.0 95.0

46.1 76.5

--- 106.9

85

CHAPTER 6 EVALUATION OF CSIP WALL ASSEMBLY SUBJECTED TO SHEAR LOADING

Methodology

Racking loads were applied to two separate CSIP wall assemblies in accordance

with ASTM E72. The panels tested had a core thickness of 25.4 cm (10 in), however

their density was 48.05 kg/m3 (3 pcf). Two separate tests were conducted. Each test

used two CSIP wall segments of dimension 254.0 x 1219.2 x 2438.4 mm (10‖ x 4‘ x 8‘)

joined along the top and bottom with a reduced timber member. The bottom connection

was the same as the connection detail in the pressure loading wall assembly. The top

connections consisted of a timber member affixed to the wall and resting on fixed roller

to prevent vertical translation. Loads were applied using an Enerpac 10,000 psi

hydraulic hand pump connected to a 12 ton Enerpac hydraulic bottle jack model number

RCH123. The loads were measured using an Omega 2,267.96 Kg (5,000 lb) load cell

model number LCH-5k. The data was recoded using a NI-PXI at 50 Hz. Displacement

was measured using two Unimeasure Linear Position Transducers (JX-P420-25-N11-

11S-31N and JX-PA-80-N11-11S-321) and one Balluff BOD63M photoelectric distance

sensor measured displacements. Figure 6-1 is a diagram of the test set up per ASTM

E72. The location of instrumentation, supports, and restrains of the wall assembly are

labeled in Figure 6-1.

Results

The racking tests were completed at the University of Florida (UF) Weil Hall

structural engineering test laboratory. Table 6-1 presents a summary of the data

collected during these two tests. Figure 6-2 Panel 1 performed with a 38% higher

capacity than panel two. This difference in load capacity between both wall assemblies

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highlights the requirement for further testing. It is evident from Figure 6-3 that de-

bonding could be a possible explanation for the difference between the performances of

the two test setups. Figure 6-3 and Figure 6-4 present the failure observed at the

completion of test 1. Comparing the data from this study with results observed by

Kermani et al. (2006) our study can be recognized as conservative. The test

configuration exceeded SIP panels with a core of 95 mm with no vertical load by 77%

and performed equivalent to a solid OSB SIP wall with 25 kN (5620.22 lb) of vertical

load. The panel assemblies, tested at the UF, were only fastened with a top plate and

bottom plate.

87

Figure 6-1. Diagram of racking test setup

Figure 6-2. Racking test load deflection interaction

0 1 2 3 4 5 6 7 80

5

10

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30

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(kN

)

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Test 2

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Figure 6-3. Racking test face-sheet de-bonding. Photo courtesy of George Fernandez

and Scott Bolton, University of Florida.

Figure 6-4. Racking test face-sheet wrinkling. Photo courtesy of George Fernandez and

Scott Bolton, University of Florida.

89

Table 6-1. Racking test results

Test # Vertical Loads

kN (lb) Test Ultimate Load

kN (lb)

Maximum displacement

cm (in) Failure observed

1 0 27.9 (6271.4) 7.06 (2.78) Wrinkling of the

face-sheet 2 0 20.1 (4519.8) 7.80 (3.07)

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CHAPTER 8 CONCLUSIONS

An experimental study was performed to characterize the out-of-plane bending

and shear capacity of composite structural insulated panels. This experimental work

was conducted to evaluate adequacy of a connection detail and to improve the

understanding of CSIP wall assemblies subjected to uniaxial bending caused by

pressure loading and shear response to racking loads.

Phase one of the testing investigated the design of the connection detail. The

investigation of the connection design began with the selection of five nail type, though

all fasteners were found to be suitable for the connection ultimately a stainless steel 6d

nail was chosen. A conservative approach was taken when specifying the nail spacing

of 76.2 mm (3 in) on center for interior nails and 38.1 mm (1.5 in) for the end nails.

Unlike timber construction nails are only placed along the top and bottom edge of face

sheets to connect to the timber members. With the elimination of studs the quantity of

nails required diminishes. Typical perimeter spacing for timber walls may vary from 51

mm (2 in) to 153 mm (6 in) and 305 mm (12 in) for field nails. (Lindt et al., 2005)

Following the design of the connection, the two core densities of CSIP walls were

subjected to wind pressures using the HAPLA, a total of 19 walls were tested. The wall

assemblies were tested with both increasing step loading and time varying pressures.

The walls with a step loading condition were able to obtain an average peak load

capacity of 5.71 kPa (119 psf). In comparison the wall tested with a time varying

pressure averaged a maximum load of 4.21 kPa (88 psf). These pressures correspond

to instantaneous wind velocities of approximately 110 m/s (246 Mph) and 100 m/s (223

Mph) respectively, exceeding the highest wind observed by only 20 m/s (46 Mph).

91

Though the likelihood of exposure to sustained winds of that magnitude due to a tropical

cyclone is minimal, the possibility does seem to be plausible in a tornado.

Ultimate loads comprise only part of the criteria for building materials, another

facet of the material designers must concern themselves with would be the

serviceability. The walls subjected to step pressure and time varying pressure failed to

meet deflection limit states of L/254 at the design pressure. (FBC, 2010) The wall

assemblies exceeded the deflection limit state at approximately 0.72 kPa equivalent to a

wind velocity of 40 m/s (90 mph) during the step loading. The walls exceeded the

deflection limit state at 0.4 kPa during the time varying pressure sequence, which would

be equivalent to a mean 60 sec wind speed of 44 m/s (100 mph). However, most

coastal communities require a design wind speed of 58 m/s (130 mph) or greater.

(ASCE 7, 2010)

Delamination was observed at the conclusion of 7 of the 14 pressure tests. The

step loaded walls experience delamination in 4 of the 5 test in contrast to the time

varying pressure loaded walls experiencing delamination in 3 of the 9 walls. The

difference in the observed delamination suggests that the walls may vary in

performance based on load time exposure and perhaps be susceptible to creep.

In plane loads are also a consideration for design. Based on a limited sample

size only two wall assemblies were tested for their in plane shear capacities.

Consequent to the vertical timber end members and a joint between two individual wall

segments not being installed, the racking test setup can be considered to be a

conservative approach to the racking capacities of such wall assemblies. It is the

author‘s opinion that this facet of the testing program should be revisited to include

92

timber connection around the perimeter and having the two panels joined at the center.

However, the two shear walls tested did exceed comparable timber shear walls tested

by 77% with no vertical load. (Kermani et al., 2006)

CSIP walls have been introduced to aid in the advancement of building materials

and technologies. Based on the small sample size, the ability to conduct statistical

comparison between core densities and loading conditions for this study was limited.

The recommendation for future testing are as followed:

Select one core density and one thickness to allow for larger sample size, enabling probabilistic modeling.

Alternative adhesives should be explored to prevent delamination between face sheets and core to maximize potential composite behavior.

Testing of shear walls with varying location and size of openings and vertical load to compare with equivalent timber wall studies.

93

APPENDIX A RESULTS OF LATERAL LOAD TEST

Figure A-1. Lateral nail capacity failure results A-S-8d. Photo courtesy of George Fernandez, University of Florida.

94

Figure A-2. Lateral nail capacity failure results B-RS-8d. Photo courtesy of George Fernandez, University of Florida.

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Figure A-3. Lateral nail capacity failure results C-S-6d. Photo courtesy of George Fernandez, University of Florida.

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Figure A-4. Lateral nail capacity failure results SST-SS-6d. Photo courtesy of George Fernandez, University of Florida.

97

Figure A-5. Lateral nail capacity failure results SST-RS-6d. Photo courtesy of George Fernandez, University of Florida.

98

LIST OF REFERENCES

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Pergamon Press.

2. ASTM D1761-06 (2006) Standard Test Methods for Mechanical Fasteners in

Wood, West Conshohocken, PA: American Society for Testing and Materials,

100 Barr Harbor Drive, PO-Box C700, 1942

3. Baehre, R., & Ladwein, T. (1994). Diaphragm action of sandwich panels. Journal

of Constructional Steel Research, 31(2), 305-316.

4. Daniel, I. M., & Abot, J. L. (2000). Fabrication, testing and analysis of composite

sandwich beams. Composites Science and Technology, 60(12), 2455-2463.

5. Davies, J. M. (1993). Sandwich Panels. Thin-WalledStructures,16, 179-198.

6. Fam, A., Sharaf, T., & Shawkat, W. (2010). Structural performance of sandwich

wall panels with different foam core densities in one-way bending. Journal of

Composite Materials, 44(19), 2249-2263.

7. Florida Building Commission and International Code Council (2010) Florida

building code 2010 International Code Council, Country Club Hills, IL

8. Florida Building Commission and International Code Council (2009) International

Residential Code 2009 International Code Council, Country Club Hills, IL

9. Girhammar, U. A. (2008). Composite beam–columns with interlayer slip—

Approximate analysis. International Journal of Mechanical Sciences, 50(12),

1636-1649.

10. Girhammar, U. A. (2009). A simplified analysis method for composite beams with

interlayer slip. International Journal of Mechanical Sciences, 51(7), 515-530.

11. Girhammar, U. A. (2008). Composite beam-columns with interlayer slip-

approximate analysis.

12. Hartsock, J. A. (1969). Design of foam-filled structures. Stamford, Conn:

Technomic Pub. Co.

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13. Heuer, R., Adam, C., & Ziegler, F. (2003). Sandwich panels with interlayer slip

subjected to thermal loads. Journal of Thermal Stresses, 26(11-12), 1185-1192.

14. T.C. E. Ho, D. Surry, and D.P. Morrish (2003). BLWT-SS20-2003 NIST/TTU

Cooperative Agreement - Windstorm Mitigation Initiative: Wind Tunnel

Experiments on Generic Low Buildings.

15. T.C. E. Ho, D. Surry, and M. Nywening (2003). BLWT-SS21-2003 NIST/TTU

Cooperative Agreement - Windstorm Mitigation Initiative: Further Experiments on

Generic Low Buildings.

16. Kermani, A., Hairstans, R. (2006). Racking Performance of Structural Insulated

Panels. Journal of Structural Engineering, 132, 1806-1812.

17. Kopp, G., Morrison, M., Gavanski, E., Henderson, D., and Hong, H. (2010).

―Three Little Pigs‖ Project: Hurricane Risk Mitigation by Integrated Wind Tunnel

and Full-Scale Laboratory Tests. Natural Hazards Review, 11(4), 151–161.

18. Manalo, A. C., Aravinthan, T., & Karunasena, W. (2010). Flexural behaviour of

glue-laminated fibre composite sandwich beams. Composite Structures, 92(11),

2703-2711.

19. Mohammed A. M., Nasim U. (2011) Global buckling of composite structural

insulated wall panels, Materials & Design, 32(2), 766-772.

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realistic wind loading. Engineering Structures, 33(1), 69-76.

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residential construction process. Journal of Construction Engineering and

Management-ASCE, 132(7), 786-794.

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Engineering and Industrial Aerodynamics 52 305-319

23. Roberts, J. C., Boyle, M.P., Wienhold, P. D., Ward, E. E. and White, G. J. (2002).

Strains and deflections of GFRP sandwich panels due to uniform out-of-plane

pressure. Marine Technology and SNAME News, 39(4), 223.

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24. Schnabl, S., Saje, M., Turk, G., & Planinc, I. (2007). Locking-free two-layer

Timoshenko beam element with interlayer slip. Finite Elements in Analysis &

Design, 43(9), 705-714.

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sandwich panels. Journal of Reinforced Plastics and Composites, 29(22), 3380-

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Insulated Panels for Exterior Wall Applications. Journal of Composites for

Construction, Vol. 14, No. 4, 464-469.

27. Viswanathan, A. V., Tamekuni, M., Boeing Commercial Airplane Company., &

Langley Research Center. (1973). Elastic buckling analysis for composite

stiffened panels and other structures subjected to biaxial inplane loads.

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28. Wood, L. W., Forest Products Laboratory (U.S.), & University of Wisconsin.

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Construction, Aug 2005, 46-50.

101

BIOGRAPHICAL SKETCH

George Fernandez was born in 1986 in Jacksonville, North Carolina. At a young

age he moved to Miami, Florida, where he remained until 2005 when he graduated from

Miami Coral Park Sr. High. Raised by a single mother, his mother‘s hard work and

dedication served to motivate George in pursuing his academic endeavors. Always

intrigued by dismantling and reassembling household items, George was afforded a

unique opportunity to enter an engineering magnet program at his high school. During

his time at Miami Coral Park Sr. High George was actively involved in student

government and the robotics team. He was inducted into his school‘s Hall of Fame for

his contribution and dedication in the field of technology. He later moved to Winston-

Salem, North Carolina where he went on to complete the majority of the requirements

for his Associates of Arts degree. George also had the privilege of becoming the first

Hispanic to join a local volunteer fire department and be a registered firefighter in that

state.

In the fall of 2006 George returned to Florida and enrolled in Santa Fe College.

Upon completion of his Associates degree he was admitted into the University of

Florida‘s Civil and Coastal engineering program. Eager to contribute to the University of

Florida‘s community he began his academic career by teaching incoming freshmen

AutoCAD for the deptartment. His first exposure to research was a position assisting

professors with their individual projects at various labs within the civil engineering

department. It was during this time he found his passion for Hurricane research, to

which he would invest the following seven years of his life. Under the guidance and

tutelage of Dr. Forrest Masters and Dr. Kurt Gurley, George was welcomed into the

Hurricane research group in UF‘s civil engineering department. For the duration of his

102

undergraduate degree George was afforded the opportunity to work with some of the

leading experts and professors in the fields of wind engineering and civil engineering.

He became a part of the Florida Coastal Monitoring Program (FCMP), a unique joint

multi university venture established in 1996 that focuses on experimental methods to

quantify tropical cyclone wind behavior and the resulting loads on residential structures.

He assisted in preparation of field deployable instruments to quantify near-surface

cyclone winds for all named storms from fall 2006 through fall 2012.

After completing his Bachelor of Arts degree in the fall of 2009, George was

extended an offer to continue in his research as a graduate student under the

mentorship of Dr. Forrest J. Masters. His graduate work was focused on wind load

resistance Composite Structural Insulated Panels (CSIP), retrofitting FCMP field

observation towers, and serving as the student lead for the Hurricane Hazard

Immersion Program. The latter is an outreach program focused on providing current

event information and hands on research experience to middle school Science,

Technology, Engineering, and Mathematics (STEM) teachers for the development of a

hurricane mitigation curriculum.

George Fernandez is currently a student member of the American Association for

Wind Engineering and American Society of Civil Engineers. Following his graduation

with his Master of Engineering degree, George will join Florida International University

as a research scientist.

by george a. fernandez - university of...

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