Bolt Holes 5.1. Maximum hole sizes for bolts are specified in the Specification Table J3.3. What if an actual hole dimension is between two of the values? When deformation is a design consideration, the design strength is limited to the force at which the hole edge has deformed by a maximum of ¼ in. When deformation is.
When an anchor is installed into concrete, there is an area surrounding the anchor called a cone of influence in which the anchor is affecting and it is affected. When two anchors are spaced too closely to one another and/or too closely to an edge, the anchor’s cone of influence reduces or becomes interfered with. When this occurs the anchor’s tension and shear capacities, which are obtained from test data, are significantly reduced. Most manufacturers provide reductions for tension and shear capacities for these limitations as these are common occurrences in the field.As embedment increases, the anchor’s cone of influence increases and there will be an increase in tension and shear capacities. However, embedding an anchor too close to the opposite face of the concrete can lead to spalling damage.
A rule of thumb is that an anchor should have a minimum of 12x the diameter of anchor spacing to an adjacent anchor or to any concrete edge. Also, the concrete should have a minimum thickness of 1.5x the depth of embedment.Watch a video of this happening:Topic Credit: Zach Rubin, PE.
The connection consists of a 5″ x 1/2″ plate connected to a 3/8″ gusset plates through (4) three- quarter inch bolts. The material type of both the tension and gusset plate is A36 steel. The center to center distance of bolts in the longitudinal and transverse direction, s, is equal to 2.5″. The distance from the centerline of the edge bolts to the edge of the gusset plate in the longitudinal and transverse direction, L e, is equal to 1.25″. A dead dead load of 10 kips and live loads of 40 kips are applied to the tension plate.The first step is to check the spacing between bolts in the longitudinal and transverse direction per AISC J3.3.The second step is to check the edge distance requirements per AISC Table J3.4 in the longitudinal and transverse direction. We assume sheared edges just to be on the safe side.The third step is to calculate the bearing strength of the connection.
To calculate the bearing strength, we first determine “h” which is equal to the bolt diameter plus 1/16″. Next we consider L c for the edge bolts which is equal to L e minus “h” divided by 2. Once this is known, the bearing strength of the edge bolts is found using AISC Equation J3-6a. After calculating the bearing strength of the edge bolts, we turn our attention to the remaining holes and calculate L c for them which is equal to “s” minus “h”.The bearing strength for the remaining holes can now be found using AISC Equation J3-6a. The nominal bearing strength of the connection is equal to the number of edge bolt holes times the bearing strength of the edge holes plus the number of remaining holes times the bearing strength of the remaining holes.
It should be noted that the bearing strength for both the gusset and tension plate must be considered and the lower value will serves as the nominal bearing strength of the connection.The fourth step is to calculate the required and design strength per LRFD. If the design strength is greater than or equal to the required strength, then the connection is adeqaute. If the design strength is less than the required strength, then the connection is inadeqaute.The last step is to calculate the required and allowable strength per ASD. If the allowable strength is greater than or equal to the required strength, then the connection is adeqaute. If the allowable strength is less than the required strength, then the connection is inadeqaute.Abdul Siraj.