QUESTION: (SUMMER2014) I am involved with evaluation of an existing building structure for compliance with the current code. The structure is in a sound condition. It satisfies the building code and CSA S16-09 for the intended occupancy except that the column bases have 2 anchor rods instead of 4. In one area, a row of small wide-flange columns sit on a concrete wall. The x-axis of these columns, their anchor rods and the centre line of the wall all lie in the same plane. It is impossible to install 4 anchor rods in the normal configuration to this relatively thin wall. However, I can provide 4 collinear rods per column by adding 2 more. Is this collinear pattern acceptable?

ANSWER: I see two parts in your question:

a) Is collinear distribution of 4 anchor rods in compliance with Clause 25.2 of S16? The requirement for a minimum of 4 anchor rods aims to ensure erection safety. The rods should be positioned to provide an adequate lever arm against overturning in more than one direction. Clause 25.2 of S16-14 specifies 4 non-collinear rods per column, unless special precautions are taken.

b) Does Clause 25.2 apply to a structure that has been completed and in service? No, it is an erection safety requirement.

QUESTION: (FALL2013) When anchor bolts are used to transfer lateral shear in a column base, what is the maximum hole size permitted? I have come across a guide in the literature recommending a maximum hole diameter of 1/16” larger than the anchor bolt diameter but the contractors demand much larger holes.

ANSWER: Typically, a shear lug(s) is used to transfer large shear forces between a column base and the footing. Anchor rods are also used, generally to transfer smaller shear. Use of standard hole size for bolts, or 1/16” hole clearance, is not a practical solution as larger holes are necessary in order to accommodate anchor rod installation tolerances, etc. In that case, appropriately designed washers with standard holes are field-welded to the base plate in the erected position to transfer the shear forces. It has been reported in research studies that these anchor rods are subjected to bending as well as shear and any tension where present.

QUESTION: (SUMMER2013) Is there a standard for anchor bolts?

ANSWER: Yes, ASTM F1554 covers three grades of anchor bolts: Grade 36 (248 MPa), Grade 55 (380 MPa) and Grade 105 (724 MPa).The vast majority of anchor bolts (or anchor rods as defined in CSA S16-09) are used to position, level and secure base plates for concentrically loaded gravity columns. Fabricators have traditionally supplied these anchor rods manufactured from round bar stocks produced to ASTM A36 (or CSA G40.21 300W). Since the introduction of ASTM F1554, Grade 36 products fill this role.Grades 55 and 105 are produced to meet higher specified strengths. In addition, when specified in the purchased order as a ‘supplementary requirement,’ they are supplied to meet specific Charpy notch-toughness with test values.