Allowable Stress Design (ASD) Method and Strength Design (SD) Method Information

Allowable Stress Design (ASD) Method

In allowable stress design (ASD), the Designer must size the anchorage such that the service load does not exceed the allowable load for any anchor:

T_service ≤ T_allowable

V_service ≤ V_allowable

The Designer must read the allowable load from the applicable table and adjust the allowable load for all applicable design parameters for the anchor, such as spacing, edge distance, in-service temperature or allowable-stress increase for short-term loads. Load-adjustment factors for anchors are applied cumulatively. For adhesive anchors, the designer must also ensure that the service load does not exceed the allowable load of the steel insert.

For anchors subjected to simultaneous tension and shear loading, the following equation must be satisfied, where the value of n is product-specific. Use a value of n=1 unless otherwise specified in the applicable products' load table.

Linear interpolation of allowable loads between embedment depths and/or compressive strengths shown in the load tables is permitted. Linear interpolation of load-adjustment factors in the edge distance and spacing tables is also permitted.

The allowable loads in this catalog are derived from full-scale testing, calculations, and/or experience. In general, the allowable load is determined by taking the average ultimate load from full scale tests and dividing by a safety factor (Ω).

For some anchors, the average ultimate load and/or allowable load is also controlled by anchor displacement limits.

The allowable loads for steel inserts used with adhesive anchors is determined as follows:

For threaded rod: T_allowable = 0.33F_u A_g ; V_allowable = 0.17F_u A_g

For Grade 60 rebar: T_allowable = (24,000 psi)A_g ; V_allowable = 0.17(90,000 psi)A_g

Where:

A_g = Gross cross-sectional area of the insert

Where:

F_u = Ultimate tensile strength of steel insert

Strength Design (SD) Method (Under ACI 318 APPENDIX D, ICC-ES AC193, and ICC-ES AC308)

In strength design (SD), the Designer must size the anchorage such that the required strength (i.e. factored load) does not exceed the lowest design strength of the anchor or anchor group considering all possible failure modes.

N_ua ≤ ΦN_n

V_ua ≤ ΦV_n

Calculations are performed in accordance with the applicable design standards: ICC-ES AC193 and ACI 318 Appendix D for mechanical anchors and ICC-ES AC308 for adhesive anchors. The additional design provisions of AC308 are shown elsewhere in this catalog.

The nominal strengths and design data in this catalog are derived from testing and calculations in accordance with ACI 355.2. ACI 355.4, ICC-ES AC193 and ICC-ES AC308. In general, nominal strengths are 5% fractile strengths calculated using the average ultimate load, and standard deviation of full-scale test results. A 5% fractile strength is the nominal strength for which there is a 90% confidence that there is a 95% probability of the actual strength exceeding the nominal strength.

For anchors that are designed using ACI 318 Appendix D, AC193, or AC308, it is possible to convert design strengths (i.e. ΦN_n or ΦV_n) to allowable loads using the following approach from AC193:

Where:

T_{allowable,ASD} = Allowable tension load

V_{allowable,ASD} = Allowable shear load

ΦN_n = Lowest design strength of an anchor or anchor group in tension as determined per ACI 318 Appendix D, AC193, AC308 and the IBC.

ΦV_n = Lowest design strength of an anchor or anchor group in shear as determined per ACI 318 Appendix D, AC193, AC308 and the IBC.

α = Conversion factor calculated as a weighted average of the load factors for the controlling load combination. In addition, α shall include all applicable factors to account for non-ductile failure modes and required over-strength.

Interaction shall be calculated as follows:

For tension loads, T ≤ 0.2T_allowable, the full allowable load in shear shall be permitted.

For shear loads, V ≤ 0.2V_allowable, the full allowable load in tension shall be permitted.

For all other cases: