ASCE Risk Categories Explained

Background Building codes require that buildings be classified by their level of importance in determining the risk taken with safety factors against their failure under critical design loads. Calculations for the structure’s overall stability, flexure, and fatigue are all based on the assumption of a given risk category design level.  ASCE 7 references risk category…

Flood Engineering Glossary

FLOOD GLOSSARY The following is provided as a curated summary of terms taken from the referenced standards that appear in the article footing. NATIONAL FLOOD INSURANCE PROGRAM (NFIP) The Federal program, create by an act of Congress in 1968, that makes flood insurance available in communities that enact satisfactory floodplain management regulations.   FLOOD INSURANCE…

Flood Resistant Design & Floodproofing of Buildings

An engineer’s walk through of the design requirements for flood resistant design of building components With Engineering Express’s early start with floodproofing designs for floor barriers and exterior glazing in projects across the US, we quickly became experts in this field.  We’ve witnessed and directed static and dynamic flood testing, sat on industry meetings, met…

Wind Speed vs. Wind Pressure Explained

Many who don’t understand how wind works will state a product is rated to a specific wind velocity which is false advertising and not true. “Rated to 180 MPH wind” is frequently seen in marketing materials which is a false and misleading statement that comes with many unwritten disclaimers.   The formula that converts wind velocity to…

ASCE 7 Main Wind Force vs. Components & Cladding Explained (MWFRS vs. C&C)

ASCE 7 separates wind loading into three types: Main Wind Force Resisting System (MWFRS), Components and Cladding (C&C), and Other Structures and Building Appurtenances. MWFRS is defined as “(a)n assemblage of structural elements to provide support and stability for the overall structure.” Typically, members which receive loading from two surfaces are designed to resist MWFRS…

About ASCE 7’s Directionality Factor Kd

The directionality factor (Kd) used in the ASCE 7 wind load provisions for components and cladding is a load reduction factor intended to take into account the less than 100% probability that the design event wind direction aligns with the worst case building aerodynamics.   Per ASCE 7-10,Section 26.6, the Directionality Factor Kd is defined…

ASCE 7 Wall and Roof Zones Explained

Per ASCE 7-10, buildings are composed of 5 different zones, depending on the wind loading they are subjected to. These zones are defined as follows: Zone 1: Has the lowest load; this zone accounts for approximately 80% of the roof surface, represented in the interior zones of the roof. Zone 2: Higher loading than Zone 1; this…

Mean Roof Height (ASCE 7)

Per ASCE 7, the Mean Roof Height (h) is defined as the average of the roof eave height and the height to the highest point on the roof surface, except that, for roof angles of less than or equal to 10°, the mean roof height is permitted to be taken as the roof eave height. Visually, AAMA TIR A15-14…

How do I tell if my building is considered “enclosed”?

A building is considered “enclosed” if it does not comply with the requirements for open or partially enclosed buildings (ASCE 7-10, Section 26.2, “BUILDING, ENCLOSED”).   From the ASCE 7-05 Commentary   BUILDING, ENCLOSED, OPEN, PARTIALLY ENCLOSED: These definitions relate to the proper selection of internal pressure coefficients, GCpi . Building, open and building, partially enclosed are specifically…

How do I calculate the effective opening area on window or door products? – What opening area should be used for wind pressure determination on a multi-panel product?

The Building Codes in the US reference ASCE-7 for the design of the components and cladding of buildings (26.1.2.2 ASCE 7-(10)).  The theory of wind design goes that the smaller the area in consideration, the greater the probability that a maximum burst of wind will occur in that area over any 3 second period.  Wind…

What wind speed should I use for my project?

The answer to that question varies with location and type of building, but feel free to download the attachment listed below which is an exhaustive list of the wind speeds used in the general Florida locale and another general map for the country. Please be sure to verify with your local Building Department as these…

Should a professional utilize the ASD (“Allowable Stress Design”) method or the LRFD (“Load Resistance Factored Design”) method when calculating the required wind pressure for use with tested / approved systems?

Most all products are evaluated using the ASD method (unless noted otherwise). ASD method in, then ASD method out. Among the notable changes in ASCE 7-10, the wind speed map and the importance factor for wind loads have been replaced with three wind load maps based on difference and newly defined return periods and for…