3.2 GENERAL CONSTRUCTION FASTENER DESIGN AND SELECTION
Direct Fastening Technical Guide , Edition 24
3.2 GENERAL CONSTRUCTION FASTENER DESIGN AND SELECTION
3.2.1 FASTENING TO CONCRETE
3.2.1.1 GENERAL SUITABILITY
When a powder , battery or gas-actuated fastener is driven into concrete , the concrete around the fastener shank is displaced . This displaced concrete compresses against the shank creating a friction hold . In addition , heat generated during the driving process causes a sintering of the concrete to the fastener .
A fastener driven into concrete is influenced by the following factors :
• Depth of penetration
• Compressive strength of the concrete
• Fastener spacing and edge distance
• Fastener shank diameter
• Concrete aggregate
3.2.1.2 DEPTH OF PENETRATION INTO CONCRETE
Generally , as the fastener penetration increases , so does the load capacity ( 1 ) See chart
at right . However , a penetration depth which is too shallow or too deep may cause an increase in fastening failure . Depth of Penetration Guide 1
Material
Concrete block and joints
Average concrete ( 2000-4000 psi )
Precast or prestressed concrete ( 5000 psi +)
Typical
3 / 4 " to 1 " ( 19 to 25 mm )
Sprinkler installations with W10 stud only
3 / 4 " to 1-1 / 4 " 1 " to 1-5 / 8 " ( 19 to 32 mm ) ( 25 to 41 mm )
3 / 4 " to 1 " 1 " to 1-1 / 4 " ( 19 to 25 mm ) ( 25 to 32 mm )
1 For allowable load capacities at specific embedment depths refer to specific product sections .
–
Sintering Zone
Compression Zone
Fastener point magnified at sintering zone
3.2.1.3 COMPRESSIVE STRENGTH OF CONCRETE / AGGREGATE HARDNESS
Generally , as the concrete compressive strength increases , so does the fastener ’ s load capacity . However , the characteristics of the fastener , and additional concrete properties aside from compressive strength influence the fastener holding power and potential for making a successful fastening . Fastener properties include the shape of the tip , the diameter , and the hardness . Concrete properties include aggregate size , hardness , and density . For these reasons , it is always recommended that test fastenings under jobsite conditions are carried out , in order to verify the fastener selection . In general , concrete compressive strength is an indicator as follows :.
Concrete compressive strength
Optimum 2000 – 6000 psi ( 14-41 MPa ) Maximum 8500 psi ( 55 MPa )*
* May require pre-drilling with DX KWIK System ( Section 3.2.1.10 )
3.2.1.4 FASTENER SPACING , EDGE DISTANCE AND BASE MATERIAL THICKNESS REQUIREMENTS FOR CONCRETE NAIL SHANK DIAMETER d nom in . ( mm ) C min in . ( mm ) S min in . ( mm ) 0.118 ( 3.0 ) X-C G2 , G3 2-3 / 8 ( 60 ) 2-3 / 8 ( 60 )
0.138 ( 3.5 ) X-C 2-3 / 4 ( 70 ) 2-3 / 4 ( 70 ) 0.145 ( 3.7 ) X-CR 2-3 / 4 ( 70 ) 2-3 / 4 ( 70 ) 0.157 ( 4.0 ) X-P , X-U 3 ( 76 ) 4 ( 102 ) 0.177 ( 4.5 ) DS 3 ( 76 ) 4 ( 104 ) 0.205 ( 5.2 ) W10 4 ( 104 ) 4 ( 104 )
S min
C min
Depth of Penetration
t II
C min
= Min . edge distance 1
S min
= Min . fastener spacing 2 t II
= Min . concrete thickness = 3 x fastener penetration depth 3
1 Unless otherwise noted in corresponding load tables ( e . g . sill plate application ).
2 Unless otherwise noted in corresponding load tables ( e . g . perimeter wall applications ).
3 Unless otherwise noted in corresponding load tables ( e . g . lightweight concrete over metal deck applications ).
19