Astm stp 1434 2002

STP 1434 The Use of Glass in Buildings VaIerie L Block, editor ASTM Stock Number: STP1434 ASTM International 100 Barr Harbor Drive PO Box C700 West Conshohocken, PA 19428-2959 Printed in the U.S.A Library of Congress Cataloging-in-Publication Data ISBN: Symposium on the Use of Glass in Buildings (1st : 2002 : Pittsburgh, Pa.) The use of glass in buildings/[edited by] Valerie L Block p cm. ASTM special technical publication; 1434 Includes bibliographical references and index "ASTM stock number: STP1434." ISBN 0-8031-3458-4 Glass construction Congresses Glazing Congresses Safety glass Congresses I Block, Valerie L., 1951- II Title TH1560 S96 2002 691'.6 dc21 2002038238 Copyright 2002 ASTM International, West Conshohocken, PA All rights reserved This material may not be reproduced or copied, in whole or in part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of the publisher Photocopy Rights Authorization to PhOtocopy items for internal, personal, or educational classroom use, or the internal, personal, or educational classroom use of specific clients, is granted by ASTM International (/L~TM) provided that the appropriate fee is paid to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923; Tel: 978-750-8400; online: http:// www.copyright.com/ Peer Review Policy Each paper published in this volume was evaluated by two peer reviewers and at least one editor The authors addressed all of the reviewers' comments to the satisfaction of both the technical editor(s) and the ASTM International Committee on Publications To make technical information available as quickly as possible, the peer-reviewed papers in this publication were prepared "camera-ready" as submitted by the authors The quality of the papers in this publication reflects not only the obvious efforts of the authors and the technical editor(s), but also the work of the peer reviewers In keeping with long-standing publication practices, ASTM International maintains the anonymity of the peer reviewers The ASTM International Committee on Publications acknowledges with appreciation their dedication and contribution of time and effort on behalf of ASTM International Printed in Bridgeport, NJ December 2002 Foreword The Symposium on The Use of Glass in Buildings was held in Pittsburgh, Pennsylvania on 14 April, 2002 ASTM International Committee E06 on Performance of Buildings served as its sponsor The symposium chair of this publication was Valerie L Block Contents vii Overview SESSION I: QUALITY ISSUES ASTM C 1036: Does It Work for Field Inspections of Surface Blemishes?-TED W MAZULA AND IVAR HENNINGS Codes and Standards Affecting Glass in Buildings: The U.S and Beyond-8 VALERIE L BLOCK The Impact of Serf.CleaningGlass -CHRISTOPHER J BARRY AND THOMAS O'DAY PC.Based Stress Measuring System for On-line Quality Control of Tempered and Heat.Strengthened GlasS -ALEXS REDNER 20 26 SESSION II" PERFORMANCE ASSESSMENTS In-Situ Dew-Point Measurement to Assess Life Span of Insulating Glass U n i t s - - - G E O R G E R TOROK, WERNER LICHTENBERGER, AND ALLAN MAJOR 35 Evaluation of the Condensation Resistance Rating as Determined Using the NFRC 500 Progedure DAN1EL J WISE AND BIPIN V SHAH 49 SESSION III: GLASS DESIGN Structural Performance of Laminated Glass Made with a "Stiff" Interlayer-STEPHEN J BENNISGN, C ANTHONY SMITH, ALEX VAN DUSER, AND ANAND JAGOTA 57 Development of Design Methodology for Rectangular Glass Supported on Three Sides to Resist Lateral Uniformity Distributed Loads-MOSTAFA M, EL-SHAM! AND H SCOTT NORVILLE 66 Wind Load Resistance of Large Trapezoidal Glass Lites H scoyr NORVILLE, MOSTAFA M EL-SHAMI, RYAN JACKSON, AND GEORGE JOHNSON 79 Window Glass Design Software STEPHEN M MORSE 90 A Thermal Stress Evaluation Procedure for Monolithic Annealed Glass-W LYNN BEASON AND A WILLIAM LINGNELL SESSION IV: GLASS 105 IN HURRICANES Retrofitting Commercial Structures with Laminated Glass to Withstand Hurricane E f f e c t s - - P A U L E BEERS, MARK A PILCHER, AND JEFFREY C SCIAUDONE 121 Testing of Annealed Glass With Anchored-Film Glass Retention Systems for Fallout Protection after Thermal Stress Cracking BRUCE S KASKEL, JOHN E PEARSON, MARK K SCHMIDT, AND ROGER E PELLETIER 131 SESSION V: GLASS FOR FIRE SAFETY AND SECURITY The Advantages of Glazing in Overall Security Strategy MiCHAELBETTEN AND HENRI BERUBE The Relationship Between Sprinkler Systems and GlasS JERRY RAZWICK 147 153 Design Procedure for Blast.Resistant Laminated Glass H SCOTTNORVILLE AND EDWARD J CONRATH Index 159 171 Overview This book represents the work of numerous authors at the first Symposium on the Use of Glass in Buildings, April 14, 2002, Pittsburgh, PA Architectural glass was the broad focus for this symposium Papers and presentations were targeted to deliver information the user may find useful related to the quality, design, use, and performance of architectural glass The symposium had a broad focus that incorporated a variety of glass-related topics Emphasis on glass design was also a key feature to the symposium The papers contained in this publication represent the commitment of the ASTM E-06.51 subcommittee to providing timely and comprehensive information on glass used in buildings Common themes throughout the tenure of this symposium can be found in this issue Papers discussing quality issues, performance assessments, glass design glass in hurricane-prone areas, and glass for fire safety and security were presented Quality Issues Quality issues were addressed from several points of view One paper focused on the problems associated with the use of ASTM C1036 for field inspections of glass Another paper examined the interrelationship between building codes and glass standards A third paper discussed an on-line quality control measuring system for tempered and heatstrengthened glass A fourth paper assessed the impact of self-cleaning glass Performance Assessments The intent of this section was to present developments around the performance of insulating glass and glass facades One paper discussed in-situ dew point testing to assess life span of insulating glass units A second presented an assessment of annual energy consumption of ventilated double glass facades using computer simulation A third paper focused on the evaluation of a condensation resistance rating as determined using the National Fenestration Rating Council (NFRC) 500 procedure Glass Design A series of papers were presented on glass design One paper examined the structural performance of laminated 'glass made with stiff interlayers Several papers dealt with design methodologies for glass, including rectangular window glass supported on three sides, large trapezoidal window glass lites, and window glass design software based on ASTM El300 Another paper introduced a new procedure for thermal stress evaluation of monolithic glass Glass in Hurricanes Glass used in hurricane-prone areas requires special design consideration In this session, one speaker addressed retrofitting commercial structures with laminated glass to withstand hurricane effects A second paper discussed testing of annealed glass with anchored-film glass retention systems vii viii THE USE OF GLASS IN BUILDINGS Glass for Fire Safety and Security This section was developed to cover a broad spectrum of topics, including security glazing, fire rated glass and sprinklers, and a design procedure for blast resistant laminated glass Ms Valerie Block Narberth, PA QUALITY ISSUES Ted W Mazula I and Ivar Hennings ASTM C 1036: Does It Work for Field Inspections of Surface Blemishes? References: Mazula, T.W and Hennings, I., "ASTM C 1036: Does It Work for Field Inspections of Surface Blemishes?" The Use of Glass in Buildings, ASTM STP 1434, V Block, Ed., ASTM International, West Conshohocken, PA, 2002 Abstract: Glass can be damaged after installation, and often the home or building owner is left trying to determine if the resulting surface damage is acceptable Glass quality is addressed in ASTM C1036, Standard Specification for Flat Glass However, this standard is not intended for use in the field It is useful for the proper specification of glass quality, and in lieu of any other field inspection standards, parts of ASTM C1036 are helpful in defining acceptable scratch criteria Keywords: damaged glass, scratched glass, glass inspection, glass specification, glass storage Introduction Inspecting scratched glass in the field is far from an exact science It is quite common for the project specifications to overlook the type of scratches that are acceptable The owner and contractor are both exposed to risk in this situation When a project has damaged glass, the parties look for an industry quality standard, and often turn to ASTM C1036, Standard Specification for Flat Glass to inspect the glass Under ASTM C1036, medium-intensity scratches are allowed for glass quality Glazing Select (Q3) This level of quality is recommended for architectural applications including reflective and low emissivity coated glass products, and other select glazing applications It is the most commonly specified quality of glass in the industry I and refers to Table criteria (Figure 1) for the maximum allowable blemishes for 6.0 mm (1/4 in.) or less glass thickness 1Associate Consultant, Glazing Consultants, Inc., 1325 Rotonda Point, Ste 329, Lake Mary, FL, 32746 2Vice President, Glazing Consultants, Inc., 11910 Cypress Links Drive, Fort Myers, FL, 33913 Copyright9 by ASTM International www.astm.org H Scott Norville ~and Edward J C o u r a t h Design Procedure for Blast-Resistant Laminated Glass Reference: Norville, H S and Conrath, E J., "Design Procedure for Blast-Resistant Laminated Glass," The Use of Glass in Buildings, STP 1434, V Block, Ed., ASTM International, West Conshobocken, PA, 2002 Abstract: When an explosive threat exists, building owners should strongly consider using blast-resistant glazing in windows and curtain walls Architects and engineers have few, if any, publicly available tools, procedures, or formal guidelines to aid in designing blast-resistant glazing This paper presents a design procedure for blast-resistant laminated glass The procedure finds its basis in an empirical relationship between air blast pressure, positive phase impulse, and 60-second equivalent design loading for laminated glass and window glass constructions fabricated with laminated glass The procedure is relatively simple to use The paper also addresses framing considerations for the blast-resistant glazing It gives a design example and shows comparisons with experimental results Keywords: air blast pressure, glazing design, laminated glass, insulating glass, blast resistance The Purpose of Blast-Resistant Glazing Design When explosions occur in populated areas, air blast pressure typically fractures windows, causing catastrophic results In the worst scenarios, the shards flying and failing from fractured window glass injure and kill persons [1-6], even in the absence of building collapse At the same time, air blast pressure entering buildings can cause severe damage to ears that can result in diminished hearing ability, loss of balance, and headaches [3] Relatively small explosions can cause significant window glass breakage, requiting window glass replacement and substantial cleanup Blast-resistant glazing should minimize and possibly eliminate flying and falling glass shards in any explosion In addition, under air blast pressure loading, blast-resistant glazing should maintain closure of its fenestration, significantly reducing air blast pressure-related injuries and cleanup costs Even with blast-resistant glazing, air blast pressure will fracture windows, necessitating replacement However, blast-resistant z Professor and Director, Glass Research and Testing Laboratory, Department of Civil Engineering, Texas Tech University, Box 41023, Lubbock, TX 79409 Structural Engineer, Protective Design Center, U.S Army Corps of Engineers, 12565 W Center Road, Omaha, Nebraska 68144-3869 159 Copyright9 by ASTM International www.astm.org 160 THE USE OF GLASS IN BUILDINGS glazing should remain in its openings, thus reducing the urgency for immediate replacement Explosive threats in today's uncertain world require architects and engineers to produce designs that afford protection from air blast pressure To accomplish this, they must make a prediction of a potential blast threat to a building They can define the potential blast threat in terms of (1) an amount of explosive and (2) a standoff distance from a building They design and install blast-resistant glazing based upon this predicted design threat Should an explosion larger than the design threat occur, provided it does not cause building collapse, properly designed blast-resistant glazing should (1) minimize flying and falling glass shards and their associated lacerative hazard and (2) maintain closure of most of the glazed openings The more probable scenario for blast-resistant glazing arises when no explosion occurs during its in-service life In this case, the blast-resistant glazing must perform the functions of standard glazing, i.e., providing a barrier between environments inside and outside a building while allowing light to enter the building and building occupants to observe the outside world Blast-resistant glazing must perform these everyday glazing functions economically, without maintenance beyond that which standard glazing requires In summary, the primary goal of blast-resistant glazing design consists of protecting people inside or near a building subjected to an air blast pressure loading To afford this protection, blast-resistant glazing must not contribute to the hazards associated with the blast Blast-resistant glazing accomplishes this by remaining in its frame following fracture and eliminating or greatly reducing the number and sizes of flying and falling glass shards In the vast majority of its applications, blast-resistant glazing will never experience loading from air blast pressure Consequently, blast-resistant glazing must economically perform the functions of standard glazing Window Glass Design and Blast-Resistant Glazing Design For design of vertical glazing, window glass must usually resist only wind loading For design of sloped glazing, window glass must resist loading from snow, its own weight, and wind Consequently, window glass design consists of determining the appropriate window glass type, construction, and thickness designation(s) to resist uniform loads from wind, snow, and its own weight, as appropriate Designers assume these loads act in a quasi-static manner The failure prediction methodology [ 7-9] provides the theoretical model that describes load resistance of window glass for US design procedures The failure prediction methodology addresses all factors known to affect window glass strength [8] It relates a uniform load having constant magnitude over specified time duration to a probability of breakage Under this theory, any uniform loading having finite time duration that acts on an annealed window glass lite induces a non-zero probability of breakage Within traditional window glass design, any breakage occurring in a window glass lite, i.e., a crack or fracture, constitutes failure Standard Practice for Determining Load Resistance of Glass in Buildings (E 130000) uses the failure prediction methodology as a basis for design procedures This document defines the load resistance, i.e., strength, of a window glass lite, in terms of the NORVILLE AND CONRATH ON BLAST-RESISTANT GLASS 161 magnitude of the uniform loading which acts over a time duration of 60-seconds to produce a nominal probability of breakage of eight lites per thousand, PB = 0.008, at its first occurrence Currently, US model building codes [10-12] have adopted the E 130000 methodology in some form to facilitate design to resist uniform loading E 1300-00 presents load resistance for annealed glass, termed nonfactored load, in 12 charts one for each nominal thickness designation Figure shows a nonfactored load chart for window glass having nominal 6-mm (1/4 in.) thickness, similar to that contained in E 1300-00 Plate Length(in,) 140 120 20 40 60 80 ' ' ' ' ' mm (1/4 in.)' .Glass' 100 120 ' ' ' ' ' ' Nonfactored Load (kPa) ~Pb = 0.008 140 ' ' ' '/" / l J ~ o.rs~ I 100 180 200 ' " ' ' ' ' ' " '~' " ' ' ~ /~/"- o.so~ j kPa = psf 160 ~// ,,I 3000 J , , % tE _.q v oox 80 i i N / ,.25/I ,-i /" / I L.-. "" vE 2000 = 60 I1 40 lOOO 20 o o I ooo 2000 3000 4000 5000 P l a t e L e n g t h (rnm) Figure 1-NonfactoredLoad Chart E 1300-00 uses glass type factors that relate the strength of other monolithic window glass types (heat strengthened and fully tempered) and constructions (insulating glass and laminated glass) to that of monolithic annealed window glass Current window glass theory does not precisely define the relationship between loading, time duration, and probabilities of breakage for window glass constructions and heat treated monolithic window glass When designed using E 1300-00, the probability of breakage for heat treated monolithic window glass and window glass constructions with any glass types has nominal values less than or equal to 0.008 at the first occurrence of the design loading Traditional window glass design methodology assumes that loads act quasi-statically with durations measured in seconds or longer periods When an explosion occurs, air blast pressure loads window glass lites dynamically over very short time durations Figure shows the approximate relationship between stress duration and stress magnitude at which fracture occurs for annealed window glass [13] Figure indicates 162 THE USE OF GLASS IN BUILDINGS that under short duration loading the stress at which fracture is initiated, which somehow correlates with window glass load resistance, increases dramatically I == == 10,000 m 5,000 second hour day week month Duration of Stress Figure - ApproximateRelationship Between Magnitude of Fracture Stress and Stress Duration On the other hand, the dynamic air blast pressure loading associated with an explosion excites higher mode shapes in a window glass lite causing much larger deflections and stresses than would a quasi-static loading having the same magnitude of pressure Because of the excitation of higher modes, the stress distribution for a dynamically loaded window glass lite differs significantly from the stress distribution under quasi-static loading of the same magnitude in that stresses having high magnitudes occur over large regions of a window glass lite [14] In addition to their dynamic nature, air blast pressure loadings tend to have much larger magnitudes than wind and snow loadings that typically govern window glass design Incorporating these factors, the failure prediction methodology indicates that under air blast loadings, the probability of breakage for typical monolithic window glass lites or window glass constructions approaches 1.0 even for relatively small air blast pressure loading [14] In short, the distribution and severity of the load-induced tensile stresses in a window glass lite subjected to loading from air blast pressure typically overcome any increase in resistance resulting from the relatively short duration of the loading Some designers attempt to devise "strong" monolithic window glass lites or window glass constructions to resist a design air blast pressure without fracture Many factors NORVlLLE AND CONRATH ON BLAST-RESISTANT GLASS 163 tend to make this approach undesirable First, any window glass construction designed to withstand even an air blast pressure loading of low magnitude would be very thick and would most probably involve heat treated window glass Such window glass constructions would have prohibitive costs Furthermore, a window glass construction with sufficient strength to resist without fracture an air blast pressure loading would transfer a large portion of the loading into the structural frame This load transfer would require a frame design that could resist such loading without collapse Finally, if the design employs monolithic window glass, regardless of its load resistance, it would have a finite probability of breakage under air blast pressure loads When monolithic glass fractures under air blast pressure dire consequences ensue The authors recommend that blast-resistant glazing constructions using glass should fracture under air blast pressure loading Following fracture, they should rely on post breakage behavior characteristics to eliminate flying and falling glass shards and maintain closure of fenestrations Because window glass constructions that fracture transfer much less load into the structural frame, the designer should find this approach desirable when considering the effect of air blast pressure on an entire building The designer must base blast-resistant glazing designs on maintaining closure of fenestrations and eliminating flying and falling glass shards to the greatest extent possible Blast-resistant glazing that performs these functions will minimize damage to building contents and maximize safety to building inhabitants For these reasons, laminated glass makes an excellent blast-resistant glazing material Laminated Glass and Insulating Glass in Blast-Resistant Glazing Laminated glass consists of two or more plies of monolithic glass bonded together using an elastomeric interlayer Laminators use polyvinyl butyral (PVB) most commonly as the interlayer material in fabricating laminated glass The glass plies can consist of annealed, heat strengthened, fully tempered, or a combination or window glass types Also, a single laminated glass lite can consist of glass plies having different thicknesses Aesthetically, annealed plies make the best, distortion-free laminated glass Its post breakage behavior characteristics make laminated glass an excellent blastresistant glazing When laminated glass fractures, the majority of glass shards adhere to the PVB interlayer Small shards may spall from laminated glass in a blast, especially if the PVB tears If the blast-resistant glazing must completely hold all shards, no matter how small, the designer should consider using a plastic film over the inner glass ply Manufacturers provide commercially available laminated glass constructions with a layer ofpoly(ethylene terephthalate) (PET) laminated to the inside glass ply using PVB PET can be scratched easily although it does not degrade from ultraviolet exposure in these constructions nearly as rapidly as it does in retrofit window film applications In properly designed blast-resistant laminated glass, the interlayer material should not tear under loading from air blast pressure In addition, laminated glass should remain in its frame after fracture The designer should strive to ensure that blast-resistant laminated glass behaves in this manner Insulating glass consists of two window glass lites with a sealed air space between them The two window glass lites can be monolithic glass or laminated glass As its name implies, insulating glass provides thermal insulation far superior to that of single 164 THE USE OF GLASS IN BUILDINGS window glass lites When fabricated using laminated glass, insulating glass provides excellent sound insulation Norville, et al [2] observed that insulating glass fabricated with two lites of monolithic glass could provide some minimal additional protection over monolithic glass under air blast pressure loading in the Oklahoma City bombing (Figure 3) The authors feel that insulating glass fabricated using two laminated glass lites provides one of the most economical and effective blast-resistant glazing constructions available Figure 3-Insulating Glass with Outside Lite Fractured in the Oklahoma City Bombing Design Recommendation for Blast-Resistant Glazing In designing a blast-resistant glazing system, the architect or engineer must consider four factors: the windowglass type and construction, the framing system, the attachment of the window glass construction to the framing, and anchorage of the window frame to the structural system The authors observe that most blasts in the US come from relatively small quantities of conventional explosives In window glass design discussions encompassed herein, small amounts of explosives produce blast waves that will have passed the windows before they fracture The positive phase duration of the air blast pressure occurs on the order of milliseconds In other words, by the time the window has fractured the blast pressure is long gone 165 NORVILLE AND CONRATH ON BLAST-RESISTANTGLASS Window Glass Type and Construction The authors feel that laminated glass and insulating glass fabricated with laminated glass comprise the most effective and economical blast-resistant glazing materials The authors offer a simple chart (Figure 4) that provides an empirical relationship between the weight of a hemispherical TNT charge detonated on the ground surface and its standoff distance from a window glass lite to a 60-second duration static design load In developing this chart the authors considered magnitude of reflected air blast pressure, magnitude of positive phase impulse, and experimental results [15] from blast tests involving laminated glass and insulating glass fabricated using laminated glass [16] Standoff Distance (m) 200 8910 \ ~ 175 "o 150 O~ o "J 125 m Or) 100 o 90 20 ~ 30 40 50 60 70 80 100 120 I I I I I! 6.00 t,- ~ 80 -i 0= ~ 5.00 ~ e- 70 _o 9.00 ~" 8.00 ,, , 7.00 "o 45 50 I '/ 4.00 ~ 3,(X~ ! e2.00 ~ 4O 30 20 1.50 ~ t 3O 40 50 75 100 125 150 200 250 300 400 Standoff Distance (ft) Figure 4- Chart Relating Equivalent TArTCharge Size and Standoff Distance to 60Second Equivalent Load Designers should use this chart to obtain 60-second duration equivalent design loads for laminated glass and insulating glass fabricated using laminated glass The values in the chart not apply to any monolithic glass type, insulating glass fabricated with monolithic glass lites only, or to monolithic glass with retrofit window film In comparing designs obtained using values from this chart, the authors observe that designers using this approach will obtain laminated glass thickness designations equal to or slightly higher than they would obtain using more esoteric procedures To use the chart, the designer defines the design threat explosion in terms of an equivalent weight of a hemispherical TNT charge and a standoffdismnce The designer enters the chart in Figure by projecting a vertical line from the horizontal axes that represent standoff distance to the sloping line that represents the charge weight From the intersection of the vertical projection and the sloping line, the designer projects a 166 THE USE OF GLASS IN BUILDINGS horizontal line to the vertical axes and reads the equivalent 60-second duration equivalent design load For charge sizes other than those shown, but less than 231 kg (500 lb), the designer can interpolate between the sloping lines The designer then uses procedures in E 1300-00 to select the laminated window glass type(s) (annealed, heat strengthened, or fully tempered) and to determine the required thickness designation(s) to resist the 60second duration equivalent design load If the wind load for a given design exceeds the magnitude of the 60-second duration static design loading determined from the chart in Figure 4, then the designer should use wind load to design the laminated glass or insulating glass fabricated using laminated glass The PVB in laminated glass should have 1.58 mm (0.060 in.) thickness in blastresistant glazing [16], although 0.762 mm (0.030 in.) PVB will usually suffice for smaller explosions Thicker PVB will result in larger forces that the window frame must accommodate the laminated glass plies should be annealed or heat strengthened glass Upon fracture, annealed and heat strengthened glass plies tend to produce larger shards than fully tempered glass plies The larger shards adhere well to the PVB thus reducing flying and falling glass shards and giving the laminated glass some stiffness following fracture, helping to maintain it in its frame If blast-resistant glazing is designed using values obtained from this chart, glass will fracture and require replacement Laminated glass and insulating glass fabricated with laminated glass and designed using values from this chart will more than satisfy GSA Level 3B Criteria in that it fractures "safely," producing minimum hazard The chart in Figure coupled with standard window giass design procedures provides a means to arrive at a laminated glass design suitable to resist the specified design threat explosion The chart in Figure also indicates that the best protection from a bomb is standoff distance, i.e., the 60-second equivalent design loading associated with a given bomb goes down rapidly with increasing standoff distance Framing System Under air blast pressure loading, the designer should design the window glass framing system and its anchorage to the surrounding structure to resist the maximum loading that the window glass would transfer to its supporting frame at fracture The authors interpret this as the frame loading that would result ifa 60-second equivalent loading associated with a probability of breakage of 0.5 acted on the window glass lite [16] The designer can also use dynamic analysis techniques with a design blast loading to determine the loading that the lite would transfer to the frame if it never fractured, although this might prove overly conservative, Procedures in E 1300-00 present load resistance values based on maximum nominal frame deflections of L/175 The authors note that blast tests on curtain walls indicate that more flexible frames supporting window glass constructions tend to provide better glass performance under blast loading [17] Attachment of Window Glass Construction to Framing For blast-resistant glazing, the designer should avoid "dry glazing," in which gaskets alone hold the blast-resistant glazing in its frame Standard glazing bites with gaskets NORVILLE AND CONRATH ON BLAST-RESISTANTGLASS 167 will not restrain fractured laminated glass under air blast pressure loading and the entire lite could fly from the frame The use of very deep bites with gaskets might restrain the blast-resistant glazing but could lead to other problems Blast-resistant glazing should attach to the frame using either structural silicone sealant or adhesive glazing tape The bite depth should not exceed standard depths any more than necessary to facilitate the width of the structural silicone bead or the glazing tape, where the width is measured parallel to the plane of the glass When using structural silicone sealant, the width of the bead forming the structural connection should equal the thickness designation of the blast-resistant glazing material with which it is in contact This thickness will usually be less than the thickness of the entire blast-resistant glazing construction For example, if the blast-resistant glazing construction consists of an insulating glass unit with two nominal mm (1/4 in.) lites and a 12 mm (1/2 in.) air space, the authors reeornmend a mm (1/4 in.) structural silicone bead In the event of an explosion, this width should result in some tearing of the silicone bead before the PVB interlayer tears but should maintain the laminated glass in its frame This mode of failure will tend to eliminate flying and falling glass shards while maintaining the blast-resistant glazing in its frame, especially insulating glass units Glazing tape has more flexibility than structural silicone and the designer should use a width of glazing tape to times the thickness of the blast-resistant glazing material with which it is in contact Design Example Compared With Test Result Design Procedure Consider selecting the thickness of a single laminated glass lite required to glaze a fenestration having rectangular dimensions of 1190 x 1640 mm The design blast loading results from a 25 kg TNT charge situated 25 m from the window To use the chart in Figure 4, the designer projects a line down from 25 meters, the standoff distance, to a point corresponding to the 25 kg, determined by interpolation From this point, the designer projects a horizontal line to the vertical axis This intersection indicates that the lite should resist a 60-second equivalent design loading should of approximately 2.05 kPa Going through procedures in E 1300 -00 to design the laminated glass gives a thickness designation of 10 mm For this size opening the load resistance of a 10 mm laminated glass lite is 2.39 kPa As mentioned above, the authors recommend using a PVB interlayer with 1.52 mm thickness and using a 10 mm structural silicone bead to attach the glass to the frame Comparison with an Experiment Figure shows a nominal mm thick laminated glass test specimen with rectangular dimensions of 1190 x 1640 mm after being subjected to a blast loading that corresponds to the design loading in this example The laminated glass specimen has a 0.76 mm thick PVB interlayer Clearly the specimen fractured in a safe manner, producing minimal hazard The design approach presented herein would require a larger thickness designation Under the same blast conditions, a laminated glass lite designed with this procedure would have broken in a similar manner 168 THE USE OF GLASS IN BUILDINGS Figure 5-Specimenfrom Blast Test Conclusions The authors present this design approach to give guidance to the window glass and engineering community on how to size laminated glass and laminated window glass constructions to resist blast loadings They note that in formulating the empirical relationship between air blast pressure, positive phase impulse, and 60-second equivalent loading, the authors looked at results f~om numerous blast tests with laminated glass and laminated glass constructions Use of this approach results in laminated glass designs NORVILLE AND CONRATH ON BLAST-RESISTANTGLASS 169 that will produce minimal hazard in the occurrence of an air blast pressure loading of design size or smaller For explosions with higher than design air blast pressures or positive impulses, laminated glass designed according to this approach will still provide a significant level of protection References [1] Norville, H S., Smith, M L., and King, K W., "Survey of Window Glass Broken by the Oklahoma City Bomb on April 19, 1995," Glass Research and Testing Laboratory, Texas Tech University, Lubbock, TX, 1995 [2] Norville, H S., Swofford, J L., Smith, M L., and King, K W., "Survey of Window Glass Broken by the Oklahoma City Bomb on April 19, 1995, Revised." Glass Research and Testing Laboratory, Texas Tech University, Lubbock, TX, 1996 [3] Norville, H S., Harvill, N., Conrath, E J., Shariat, S., Mallonee, S., "Glass-Related Injuries in the Oklahoma City Bombing "Journal of Performance of Constructed Facilities, American Society of Civil Engineers, 13(2), 1999 [4] Blocker, V and Blocker, Jr., T G., "The Texas City Disaster: a Survey of 3000 Casualties." American Journal of Surgery, 78, 1949, pp 756-771 [5] Brismar B and Bregenwald, L., "The Terrorist Bomb Explosion in Bologna, Italy, 1980: an Analysis of the Effects and Injuries Sustained." Journal of Trauma, 22(3), 1982,pp 215-220 [6] GRTL, "Misty Picture Data: Window Glass Experiment, Final Data Report, '" Glass Research and Testing Laboratory, Texas Tech University, Lubbock, TX, 1987 [7] Beason, W L., "A Failure Prediction Model for Window Glass, "NTIS Accession Number PB81-148421, Institute for Disaster Research, Texas Tech University, Lubbock, TX, 1980 [8] Norville, H S., and Minor, J E., "The Strength of Weathered Window Glass." Bulletin of the American Ceramic Society, 64(11), 1984, pp 1467-1470 [9] Beason, W L and Norville, H S.,"Development of a New Glass Thickness Selection Procedure," Journal of Wind Engineering and Industrial Aerodynamics, Vol 36, Elsevier Science Publishers, 1990, pp.1135-1144 [10] International Code Council (ICC), "International Building Code," Falls Church, Virginia, 2000 [11] Southern Building Code Congress International (SBCCI), "Standard Building Code," Birmingham Alabama, 1999 170 THE USE OF GLASS IN BUILDINGS [12] Building Officials and Code Administrators International, Inc., (BOCA), "The BOCA National Building Code/1999," Country Club Hills, Illinois, 1999 [13] Minor, J E., "Basic Glass Strength Factors." Glass Digest 69(9), 1990 [14] Norville, H S., "Dynamic Failure Prediction for Annealed Window Glass Lites," Glass Research and Testing Laboratory, Texas Tech University, Lubbock, TX, December, 1990 [ 15] WinDAS, "Window Design and Analysis Software." Protective Design Center, Omaha District Corps of Engineers, 215 N 17th Street, Omaha, NE, 2000 [16] Norville, H S., and Conrath, E J., "Considerations for Blast Resistant Glazing Design," Journal of Architectural Engineering, American Society of Civil Engineers, Vol 7, No 3, 2001, pp 80-86 [17] Smilowitz, R., Termant, D., Rubin, D., and Lawver, D., "Las Vegas Courthouse Curtain Wall Project; Blast Prediction, Test Planning, and Post-Shot Analysis." Report No WANY 99-01, Weidlinger Associates, Inc., New York, NY, 1999 STP1434-EB/Dec 2002 Author Index B Barry, Christopher J., 20 Beason, W Lynn, 105 Beers, Paul E., 121 Bennison, Stephen J., 57 Berube, Henri, 147 Betten, Michael, 147 Block, Valerie L., Mazula, Ted W., Morse, Stephen M., 90 N Norville, H Scott, 66, 79, 159 O O'Day, Thomas, 20 C P Conrath, Edward J., 159 E Pearson, John E., 131 Pelletier, Roger E., 131 Pilcher, Mark A., 121 E1-Shami, Mostafa M., 66, 79 R H Razwick, Jerry, 131 Redner, Alex S., 26 Hennings, Iva~ S Jackson, Ryan, 79 Jagota, Anand, 57 Johnson, George, 79 Schmidt, Mark K., 131 Sciaudone, Jeffrey C., 121 Shah, Bipin V., 49 Smith, C Anthony, 57 K T Kaskel, Bruce S., 131 Torok, George R., 35 Lichtenberger, Werner, 35 Lingnell, A William, 105 V Van Duser, Alex, 57 M Major, Allan, 35 W Wise, Daniel J., 49 171 Copyright9 by ASTMInternational www.astm.org STP1434-EB/Dec 2002 Subject Index G A Air blast pressure, 159 Airport control towers, 79 Anchored-film glass retention systems, 131 Annealed glass, 131 thermal stress evaluation, 105 ASTM C 1036, ASTM C 1048, 26 ASTM C 1279, 26 ASTM E 1300, 66, 79, 90 ASTM E 1886, 131 ASTM E 1996, 131 Glass, breakage during fire, 131 Glass inspection, Glass lites, 79 Glass quality, Glass retention, 131 Glass specification, Glass storage, Glass strength, 8, 57 Glazing, security, 147 Glazing design, 66, 79, 90 blast resistance, 159 wind load resistance, 79 H B Heat-strengthened glass, 26 High winds, 121 Hurricane resistance, 121, 131 Hydrophilic, 20 Hydrophobic, 20 Blast resistance, 159 Building codes, Burglary, 147 C Coatings, 20 Computer software, 90 Computer technology, 90 Condensation resistance rating, 49 Creep resistance, 57 Cyclic pressure cycles, 121 Impact resistant glass, 121 Insulating glass, 35 blast resistance, 159 Interlayers, 57 International standards, D Damaged glass, Design standards, 90 Dew-point measurement, 35 Laminated glass, 57, 66, 121 blast-resistant, 159 Load resistance, 66 Longevity, 35 M E Edge strength failure prediction model, 105 Edge stress, 66 F Failure prediction, 79 Fallout protection, 131 Fenestration, 131 Finite element analysis, 66, 79, 105 Fire-rated glass, 131 Missile impact test, 121 N National standards, NFRC 100, 49 NFRC 500 Procedure, 49 P Photocatalytic, 20 Polyvinyl butyral interlayers, 57 173 174 THE USE OF GLASS IN BUILDINGS Q Quality control, 26 Stress maximum, 66, 79 measurement, 26 Surface damage, R T Retrofitting, hurricane resistant glass, 121 Safety glazing, Scratched glass, Security, 147 Self-cleaning glass, 20 SentryGlas Plus, 57 Serivce life, 35 Skylights, Sprinkler systems, 131 Standards Design Group, Inc., 90 Stiff interlayer, 57 Stiffness, 57 Storm shutters, 121 Temperature differential, 131 Temperature performance, 57 Tempered glass, 26 Tensile stress, 105 THERM 2.1, 49 Thermal shock, 131 Thermal stress cracking, 13 i evaluation procedure, 105 Three-sided support, 66 W Windbome debris, 121, 131 WINDOW 4.1, 49 Wind resistance, 79