Tuesday, November 4, 2014

Anchoring Connections at Bay Windows

Source: Astor Windows's Photo Archives

A bay window projects on the outside of a building as shown on the picture above.  The most common type we find in Miami is called canted bay windows, which have a flat front and angled sides.  Bay windows became very popular during the Victorian architectural era and hold their appeal today.  When performing remove-and-replace jobs of existing homes in Miami Beach, Miami Shores, Coral Gables, South Miami and other non-incorporated Miami areas built in the 40's, 50's and 60's, we come across these types of windows.


Issue At Hand

There are typically two structural issues we encounter when replacing old bay windows for new impact windows: 

First, because these windows are set outside of the building envelope, the window header is most probable a wood build-out.  This condition was designed and built prior to establishing the High Velocity Hurricane Zone requirements.  As a result, the window header might not be designed and anchored appropriately to windstand the lateral loads exerted by hurricane-driven forces.  This is a problem for us.  Installing impact-resistant windows requires anchoring to either the main structure of the house or to members that are capable of transferring the loads to the main structure of the building. 


The second issue has to do with the connection between the window frame and the existing steel posts.  Existing bay windows have round metal posts (shown in gray in the illustration below) joining together the center window with the two flanking units.  Impact windows' frames must be installed to flat substrates, which is not the case when anchoring to a round post.  Hence, when presented with these conditions, the window contractor needs to make modifications in order to comply with the product approval of the window being installed.


Solutions

We, at Astor Windows, have encountered the the above described scenarios several times.  For the missing header issue, we custom-fabricate a steel header (previously designed by a license structural engineer) anchored to the main structure.  For the second issue of the round post and flat window frame connection, we have fabricated a continuous u-channel aluminum (or steel) wedge anchored or welded to the existing posts.  This wedge solution has been designed by a license engineer and fabricated by Astor Windows's industrial welding technicians.  Refer to 3D illustration below for details.


Source: Astor Windows


Source: Astor Windows

Thursday, October 2, 2014

Designing Structures to Provide Full Support to 3-Track Door Systems

Designing Structures to Provide Full Support to 3-Track Door Systems Impact-Resistant Sliding Glass Door
Source: Astor Windows's Photo Archives

This article is intended for design professionals who plan to specify sliding glass doors with three moving panels on three independent tracks. A three-track system allows for wide openings with unobstructed views when all panels stack on one end behind each other. It is important, though, to understand that heavy-duty, three-track configurations could measure more than 8 inches in depth. As a result, door tracks can extend beyond tie beams' and columns' depths, which presents a problem: Structural substrate must provide full support to the door tracks.

The table below provides dimensions for four sliding glass door systems rated for impact resistance and approved by Miami-Dade County. On one column we show the nominal track width, assuming NO screen rail tracks. On the other column, we present our estimated jamb or tie beam necessary depth to appropriately offer full support to the sliding glass door system.
Door System 3-Track Width
excluding screen track
(inches)
Recommended Minimum
Column/Tie Beam Depth
(inches)
PGT SGD770 7.140 9.5
PGT SGD780 9.323 11.5
CGI SGD150 5.921 8
CGI SGD560 8.625 11.5
Disclaimer: Astor Windows and Doors cannot be held responsible for the accuracy of these dimensions. These article has been written for illustration purposes. A formal analysis must be presented by Window/Door Contractor.

It is important that architects and structural engineers learn about these dimensions before they finalize their designs for new structures.