General Instructions for the Designer
These general instructions for the Designer are provided to ensure proper selection and installation of Simpson Strong-Tie Company Inc. products and must be followed carefully. These general instructions are in addition to the specific design and installation instructions and notes provided for each particular product, all of which should be consulted prior to and during the design process.
- The term "Designer" is intended to mean a licensed/certified building design professional, a licensed professional engineer, or a licensed architect.
- All connected members and related elements shall be designed by the Designer.
- All installations should be designed only in accordance with the allowable load values set forth in this catalog.
- Unless otherwise noted, connector allowable loads published in this catalog are limited to the lowest of: average recorded test load at 1/8" deflection, lowest ultimate recorded test load of 3 tests specimens divided by 3 (or the average of 6 specimens divided by 3), or the calculated value based on steel, wood bearing, and/or fastener capacity.
- Allowable simultaneous loads in more than one direction on a single connector must be evaluated as follows:
Design Uplift/Allowable Uplift + Design Lateral Parallel to Plate /
Allowable Lateral Parallel to Plate
+ Design Lateral Perpendicular to Plate / Allowable Lateral Perpendicular to Plate < 1.0.
The three terms in the unity equation are due to the three possible directions that exist to generate force on a connector. The number of terms that must be considered for simultaneous loading is at the sole discretion of the Designer and is dependent on their method of calculating wind forces and the utilization of the connector within the structural system.
As an alternate, certain roof to wall connectors (embedded truss anchors, seismic and hurricane ties, and twist straps) can be evaluated using the following: The design load in each direction shall not exceed the published allowable load in that direction multiplied by 0.75.
- Loads are based on the 2005 National Design Specifications (NDS) and the 2001 AISI Standard - North American Specification for the Design of Cold-Formed Steel Structural Members (NASPEC) if applicable, unless otherwise specified. Other code agencies may use different allowable loads.
- Duration of load
adjustments as specified by the code are as follows:
“FLOOR” and “DOWN” (100) — no increase
for duration of load.
“SNOW” (115) — 115% of design load for 2 month duration
“ROOF LOAD” (125)— 125% of design load for 7 day duration
“EARTHQUAKE/WIND” (160) — 160% of
for earthquake/wind loading.
- Unless otherwise noted, wood shear is not considered in the loads given; reduce allowable loads when wood shear is limiting.
- Simpson Strong-Tie strongly
recommends the following addition to construction drawings and specifications:
"Simpson Strong-Tie connectors are specifically required
to meet the structural calculations of plan. Before substituting another
brand, confirm load capacity based on reliable published testing data
or calculations. The Engineer/Designer of Record should evaluate and
give written approval for substitution prior to installation."
- Verify that the
dimensions of the supporting member are sufficient to receive the specified
fasteners, and develop the top flange bearing length.
- Some catalog illustrations
show connections that could cause cross-grain tension or bending of
the wood during loading if not sufficiently reinforced. In this case,
mechanical reinforcement should be considered.
- For holdowns, anchor bolt nuts should be finger-tight plus 1/3 to 1/2 turn with a hand wrench, with consideration given to possible future wood shrinkage. Care should be taken to not over-torque the nut. Impact wrenches should not be used as they may preload the holdown.
- Simpson Strong-Tie will provide
upon request code testing data on all products that have been code tested.
- The allowable loads published in this catalog are for use when utilizing the traditional Allowable Stress Design methodology. A method for using Load and Resistance Factor Design (LRFD) for wood has been published
in AF&PA/ASCE 16. A method for using LRFD for cold-formed steel has also been published in the 2001 AISI NASPEC. When designing with LRFD, reference lateral
resistances must be used. Contact Simpson for reference lateral
resistances of products listed in this catalog. For more information,
refer to the American Forest and Paper Association "Guideline to
Pre-engineered Metal Connectors" and ASCE 16. The "Guideline"
contains a soft-conversion procedure that can be used to derive
reference lateral resistances.
- For joist hangers, Simpson Strong-Tie recommends the hanger height shall be at least 60% of joist height for stability.
- For cold-formed steel applications, all screws must comply with Society of Automotive Engineers (SAE) Standard J78, Steel Self-Drilling/Tapping Screws, and must have a Type II coating in accordance with ASTM B 633, Electrodeposited Coatings of Zinc on Iron and Steel. Screw strength shall be calculated in accordance with 2001 AISI NASPEC Section E4, if applicable, or shall be based on the manufacturer’s design capacity determined from testing.
- Local and/or regional building codes may require meeting special
conditions. Building codes often require special inspection of anchors
installed in concrete and masonry. For compliance with these requirements,
it is necessary to contact the local and/or regional building
authority. Except where mandated by code, Simpson Strong-TIe products do not
require special inspection.
- Holdown and Tension Tie allowable loads are based on installations with an anchor rod length of 6" from the concrete to top of holdown seat, yet these products may be raised to any height with consideration of the increased deflection due to additional bolt elongation. For cases where the anchor bolt is offset, Simpson Strong-Tie offers recommendations, subject to the approval of the Designer, which permit holdowns to be raised up to 18" maximum with a corresponding horizontal anchor bolt offset of 1 1/2". See “General Instructions for the Installer” (note q).
- Throughout the catalog there are installation drawings showing the load transfer from one element in the structure to another. Additional connections may be required to safely transfer the loads through the structure. It is the Designer’s responsibility to specify and detail all necessary connections to ensure that a continuous load path is provided as required by the building code.
- Top flange hanger allowable loads are typically based on testing with solid headers. Load reductions may apply when using headers comprised of multiple plies of dimensioned lumber or SCL.
See T-MPLYHEADER for more information