Mullion/Frame Design – Allowable Stress Design. ▫ Design Load = Equivalent 3 second design load ASTM F ▫ Info Required –. ▫ 1) Level of Protection. F Standard Practice for Specifying an Equivalent 3-Second Duration Design Loading for Standard + Redline PDF Bundle ASTM License Agreement. ASTM F (ballistics and physical attack); as well as the UL standards for burglary resistant glazing and bullet resistant glazing. These standards enable.
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ASTM F is a standard practice for specifying an equivalent 3-Second Duration design Print/export. Create a book · Download as PDF · Printable version. download ASTM F PRACTICE FOR SPECIFYING AN EQUIVALENT 3- SECOND DURATION DESIGN LOADING FOR BLAST. ¼” screws at four jamb corners – screws bending corners screws bending. - tearing in frame wall at connections pushing limits of ASTM F □ Minimal.
Blast mitigation design is a rapidly evolving trend in the building industry.
The purpose of blast resistant design is to minimize the hazards caused by a blast as opposed to preventing damages. Conditions vary with respect to the travel distance astmm the breakage debris.
Since then, ISC has taken on a new approach to address the full spectrum of security threats through a series of documents outlining new security levels; baseline security countermeasures and implementation; risk assessment and identification; and performance measurement. With each assumed case, both the size of the weapon and location of the threat are crucially important.
ASTM F 2248
The main keywords to present this standard are air blast pressure, blast resistant glazing, explosion, insulating glass, and laminated glass. Window Design for Blast Hazard Mitigation Reducing damage caused by explosive blasts has become an emerging area of interest due to several high-profile incidents over the last two decades. The report aztm security standards and levels for existing facilities.
The standard explain different methods to check the thickness and type of blast resistant glazing fabricated with laminated glass to glaze a fenestration The main keywords to present this standard are air blast pressure, blast resistant glazing, explosion, insulating glass, and laminated glass. Referenced Documents download separately The documents c below are referenced within the subject standard but are not provided as part of the standard.
A range of manufacturers produce various lamination products based on desired response and performance characteristics. Yet there are obvious limitations in cases of cities and densely populated areas. ASTM F 2248 As a supplement to the GSA Security Criteria, ISC issued their own security criteria inestablishing additional requirements for glazing protection, standoff distances, vehicular access control, and security of air intake systems.
In addition to specific requirements for glass size, lamination, deflection limitation, and testing, UFC design criteria is generally based on ASTM F The system shall be designed to ensure 2248 the glazing fails prior to the framing system that supports the glazing and its attachment to the structural framing system. A secondary threat to consider is a hand-carried weapon that may potentially be placed directly against the building envelope.
The performance of building envelopes and cladding components during an explosive blast is more geared towards d the hazards caused by the blast, as it has been found that many of the injuries and fatalities have been a direct result of flying glass and wall debris.
Blast pressures also increase zstm with the weapon size and exponentially with the distance from the explosion.
As a result of increased terrorist activity in the past few decades, there has been growing demand for explosive blast resistance to be 22248 into the design of building structures and envelope components. Shortcomings 53 and limitations in those design standards and test methods are briefly discussed. This paper extends 56 their previous research work to apply their modeling techniques to analyze LG panels under 57 blast loads.
The comprehensive information provided through such analysis will not only 58 enhance the understanding on the blast response of LG panels, but also facilitate their design. Results from FE analysis are used to examine 61 the failure of glass, interlayer and sealant joints.
Energy absorption of different components is studied and the importance of 64 the interlayer properties is highlighted, as they are not accounted for in the current design 65 standards. In practice, engineers do blast testing to check their designs that they had carried 66 out according to design standards.
Modeling techniques presented in this paper could be used 67 to complement and supplement existing design standards for the design of LG panels, where 68 applicable, and also as a solution when they are not applicable, reducing costs, risks and 69 environmental pollution involved with blast testing. Existing design standards and their 74 limitations are reviewed below. This standard recommends 78 using either annealed or heat strengthened glass types for the glass panes than using fully 79 tempered glass which has shown a poor post-blast performance during blast testing.
For a given 82 charge weight and standoff distance, the 3-second duration equivalent design load should be 83 selected from the chart shown in Fig. This chart was 84 developed using the results from a number of blast tests conducted on LG panels for 85 hemispherical charge weights at ground level.
The width bite of the 90 structural silicone sealant bed should be at least equal to or greater than 10 mm or the 91 nominal thickness of the glass panes, while less than twice the nominal thickness of glass 92 panes to which it adheres. The minimum thickness of the structural silicone sealant bed 93 should be 5 mm.
The glazing tape should be within two to four times the thickness of the 94 glass pane. Framing system supporting the glazing should be attached mechanically 98 to the structural framing system using fasteners that should be designed to resist uniform load 99 acting on the glazing.
ASTM F 2248
The design load of the fasteners should be two times the magnitude of 100 the load resistance of the glazing if the maximum air blast pressure is greater than one half 101 the magnitude of the load resistance of glazing. On the other hand, the fasteners should be 102 designed to a load equal to the load resistance of the glazing if the maximum air blast 103 pressure is less than one half the magnitude of the load resistance of glazing.
When a 107 LG panel fails under a minimal hazard, it is expected to fracture but it should remain in the 108 frame without any failure at the sealant joints and the supportive frame.
The chart shown in Fig. This standard 117 therefore does not account the effects due to the variations of the thickness of the interlayer 118 and also the effects of different interlayer materials with varied material properties for the 119 blast response of LG panels.
A conservative design approach based on static analysis is used to design window 122 frames, fasteners and other supporting elements. The former describes an approach of designing blast resistant windows 128 basically with LG, while the later provides a design approach with monolithic fully tempered 129 glass.
UFC 4-010-01 DoD 2013 defines 133 different levels of protections known as below at standard, very low, low, medium and high, 134 which correspond to high hazard, low hazard, very low hazard, minimal hazard and no hazard 135 respectively according glazing hazard ratings defined in ASTM F 1642-04 ASTM 2010b.
Conventional construction standoff distance 141 implies the minimum standoff distance required by a DOD building to achieve either very 142 low or low level of protections without any measures for blast resistance. Buildings must at 143 least satisfy the minimum standoff distance requirement and those that do not meet 6 144 conventional construction standoff distances or that required a higher level of protection 145 should be designed for the potential blast threat at the available standoff distance.
Minimum interlayer thickness should be 0. Design should be carried out using 1 for both load and strength 160 reduction factors for all methods of analysis referenced in UFC 4-010-01 DoD 2013. The blast load is treated as a triangular load and a 164 simplified single degree of freedom SDOF model is used to simulate the dynamic response 165 of the glass panels. The glass panels are analyzed based on large deflection plate theory since 166 the panel deflections are large compared to thickness of the panel.
The maximum allowable 167 principal tensile stress of glazing is used as 16000 psi 110 Mpa in the standard. Design 7 168 deflection is the center deflection which corresponds to maximum principal tensile stress at 169 any point in the glass panel. In addition to charts, set of formulae is given in the 175 standard to design blast resistant glazing.
Framing members should be designed for the load 176 transferred from the glass panel and static design blast load applied to all exposed members.
This 181 standard uses a simplified SDOF analysis method to study the blast response of glazed panels 182 by accounting for the positive phase of the blast load only. The design charts developed in 183 this standard are applicable for monolithic fully tempered glass only.
The maximum length 184 and width of the glass panels that could be designed with UFC 3-340-02 DOD 2008 are 185 limited to about 3 and 1. However, it could be noted that the generalized 186 analyse and design method given in this standard can be applied for the design of LG or any 187 glazing type with different sizes, if the corresponding load-resistance curve is determined 188 from an analytical or experimental study. Pre-crack resistance function is derived based on large 194 deflection plate theory by considering the dynamic breaking strength of glass.
The dynamic 195 breaking strengths used in the design are 80 MPa for annealed glass and 200 MPa for fully 196 tempered glass. The post-crack resistance function is derived considering the membrane 197 action of PVB interlayer, but neglecting the stiffness of cracked glass panes. Based on the 198 extensive blast tests conducted for common window sizes used in the UK about 1.
Each contour line in the diagram connects P-I pairs giving same 205 deflection and stress, and those are called iso-damage lines. The lower contour line represents 206 the P-I pairs causing initial crack of the glass pane while the upper contour line represents P-I 207 pairs causing tearing of the PVB interlayer. Known blast threats can be marked on the P-I 208 diagram of a selected LG panel to estimate its performance under the blast threat.
The panel 209 edges should be securely held in robust frames by using structural silicone sealant with a 210 width bite of about 35 mm. Support reactions can be obtained based on equivalent SDOF 211 factors for two-way spanning simply supported panes with a uniform load. It is restricted to military use 213 giving limited access to the external users. The authors could not find a copy of this 214 document and hence limited information is given in the paper.
UK Glazing Hazard Guide 215 1997 is limited to a few window sizes used in the UK and therefore has a limited 216 application in designing blast resistant glazing in real buildings. This report describes two design approaches known as 221 static and dynamic approach that could be used to design single glazing units or insulated 222 glazing units fabricated with LG to blast loads.
This 225 approach was described earlier in the paper and is also described in detail in PDC-TR 10-02 226 2012 with some worked examples. The 229 authors prefer the use of FE codes when analyzing and designing glazing under blast loads 230 and their approach is described later.
However, PDC-TR 10-02 2012 provides some useful 231 information on computer programs and their applications to design window systems under 232 blast loads.
These programs are based on SDOF analysis where 235 their approach is an iterative process of selecting initial glazing or member size and then 236 repeating the analysis until the window system is found to have an acceptable response. One of the major limitations is that the design outcome will be much conservative as 10 241 it is based on simplified SDOF analysis. On the other hand, a comprehensive knowledge and 242 an understanding about the computer program are required to achieve feasible and safe 243 design.
However, these programs generate the output results in numbers unlike in the FE 244 codes where it is possible to observe the predicted response and the failure pattern. These test methods can be classified into 248 two types as arena air blast test and shock tube test.
An arena air blast test is carried out in an 249 open environment and is expensive compared to the shock tube test, but it tests several test 250 panels simultaneously.
A shock tube test is carried out in a closed tube and is not a realistic 251 test, but is capable of reproducing the same shock repeatedly. The hazard rating of a glazing system is determined based on the severity 258 of fragments generated during the blast testing.
The severity of fragments is determined by 259 considering the number, size and location of fragments observed after the test. A fragment is 260 defined as any particle having a united dimension of 2.
Testing can be conducted using either arena air blast or shock tube test types from 265 which the blast load is obtained. This standard requires at least three test specimens 266 representative of a glazing or glazing system to be tested at a given blast load and an 267 additional specimen should be used for pre-test measurements.
Pressure transducers are used 268 to record the blast pressure on the test panel during the testing. ISO 16933 ISO 2007a covers broad 274 range of blast parameters incorporating 7 standard blasts simulating vehicle bombs and 7 275 standard blasts simulating smaller hand-carried satchel bombs. On the other hand, ISO 16934 276 ISO 2007b applies for blast waves generated in shock tube facility, simulating the reflected 277 pressures and impulses generated from high-explosive detonations of approximately 30-2500 278 kg TNT at standoff distances from about 35-50 m.
However, 286 non-standard test specimens could only be tested, but not classified according to these 287 standards. They provide 6 hazard ratings: A-F no break, no hazard, minimum hazard, very 12 288 low hazard, low hazard and high hazard based upon the severity of fragments and hazard 289 effects, evidenced by distribution of fragments and damage to the witness panel occurred 290 during the blast test.
Most 294 of the universities and government organizations do not have sufficient funds and space to 295 conduct blast testing. As described above, all these standards require at least three specimens 296 to be tested under a given blast load, as repetitive testing is required to accurately predict the 297 behavior and the failure of a glazed panel under a blast load. On the other hand, these test 298 methods are valid for small test specimens with standard dimensions and large glazed panels 299 used in most buildings could not be classified according to the above standards.
Health and 300 safety issues and environmental pollution are some other negative effects of blast testing. However, current design standards and test methods have some 303 limitations and they were briefly discussed above.
This emphasizes the need for a new 304 analytical procedure for the design of glazing to blast loads. Numerical analysis with FE 305 codes is a feasible method that has been used to investigate the behavior of LG panels under 306 blast loads Chung et al. This approach is presented below. However, most of the research was 314 unable to account for the post-crack load carrying capacity of LG as well as the effects of 315 structural sealant joints.One-quarter of the panel was analyzed using symmetry, 391 assuming that the blast load is uniformly distributed over the entire front glass pane.
Results from FE analysis are used to examine 61 the failure of glass, interlayer and sealant joints. Kaziktilar New and improved technologies are continuously being researched, developed and tested. This approach is presented below. The system shall be designed to ensure that the glazing fails prior to the framing system that supports the glazing and its attachment to the structural framing system. This analytical method for glazing should be used with caution for glazing panels larger than 1.
The design blast overpressure time history curve obtained from the Friedlander 381 equation is shown in Fig. Referenced Documents download separately The documents c below are referenced within the subject standard but are not provided as part of the standard.