Appeal 13338

OSSC 2010 720.1(1)

Per ASCE 7-10 section 13.5.3, Exterior Nonstructural Wall Elements and Connections shall be designed to accommodate the relative seismic displacements defined in section 13.3.2 and movements due to temperature changes.

The allowable story drift ratio for the project, Risk Category I is 0.02hx which is equal to 3.9” at the 2nd floor, 2.6” at the 3rd and 4th floors and 3.1” at the roof. These allowable drifts will include the seismic drift amplification factor of 5 at the 2nd floor concrete portion and factor of 4 at the 3rd to roof steel stud bearing wall system. These factors are included in the drift limit to account for inelastic drifts corresponding to MCE (Maximum Considered Earthquake).

Per city of Portland interpretation, the brick horizontal and vertical joints to accommodate drift which will be 2.2” at the 2nd floor, 1.7” at the 3rd and 4th floor and 1.6” at the roof.

We understand that the intent of the code is for Life Safety and preventing large chunk of the cladding elements from detaching from structure and causing life safety hazard. We are presenting the commentary section of ASCE 7-10 section C13.5.3 that explains the intent and the standard practice of ½” – ¾” joints. We are also presenting pages from ASCE 41-13 that shows the acceptance criteria for cladding elements for Life Safety is to limit the drift ratio to 0.02 and provide the ties as required in the documents.

We believe that by limiting our structure drift to less than 0.02 drift ratio, the structure is meeting the Life Safety performance of the code. We will provide the required brick tie spacing and ledger angles at every floor as described in the code. We propose ¾” horizontal joints at the ledger angles and ½” vertical joints at the windows. We will provide tighter brick tie spacing at the brick corners with the intent to prevent large chunks of bricks separating from the structure. The actual drifts correspond to the designed level earthquake for the project is 0.44” at 2nd floor, 0.425” at 3rd and 4th floors and 0.4” at the roof.

We believe that larger brick joints will not guarantee that the brick will not be damaged or fall off after the Maximum Considered Earthquake event. It’s not reasonable for the building owner to have this expectation on the performance of the cladding system after the MCE event.

We believe that larger joints will increase the risk of water penetrate thru and corrode the brick ties during the life of the building. This risk will increase the likelihood that brick may fall of the building during the building’s service life even after minor earthquakes.

It has been our experience designing similar projects in states of WA, CA, and OR that the brick joints are only as large as what’s required for thermal expansion, wood shrinkage (for wood building) and beam/slab deflection under superimposed dead and live loads. This experience matches the industry standard practice.

OSSC 1812

OSSC 1812 – RADON CONTROL METHODS – GROUP R-2 AND R-3 OCCUPANCIES

• THERE ARE THREE DWELLING UNITS (RESIDENTIAL LIVING UNITS) ON THE GROUND FLOOR OF THE BUILDING.
• ADDITIONAL RESIDENTIAL USES ON THE GROUND FLOOR USES INCLUDE LOBBY, BIKE PARKING MAIL ROOM AND TRASH ROOM. ALL ROOMS ARE MECHANICALLY VENTILATED PER CODE.
• UNDER THE GROUND FLOOR IS A FULL BASEMENT USED FOR PARKING. THIS PARKING GARAGE IS CONSIDERED CONTINUOUSLY VENTILATED/EXHAUSTED PER THE OMSC AT THE CONTINUOUS EXHAUST RATE IS 0.05 CFM/SF AND THE INTERMITTENT RATE (WHEN CO SENSOR TRIGGERS) IS 0.75 CFM/SF. THE TOTAL CFM EXHAUSTED IS 950 CFM AND 13,900 CFM, RESPECTIVELY.
• THE PROPOSED DESIGN REQUESTS NO SUBFLOOR PREPARATION, SOIL GAS RETARDER AND SUB-SLAB SOIL EXHAUST SYSTEM BE REQUIRED IN THIS PROJECT.

SECTION 1812 PROTECTS RESIDENTIAL OCCUPANTS FROM POSSIBLE RADON GAS EXPOSURE IN THEIR LIVING SPACES. IT WAS INTENDED PROVIDE RADON MITIGATION FOR GROUND FLOOR AND BASEMENT SPACES THAT ARE IN CONTACT WITH THE UNDERLYING SOIL AND / OR ROCK. THE PROPOSED DESIGN PROVIDES CODE-COMPLIANT MECHANICALLY VENTILATED/EXHAUSTED SUB-GRADE PARKING LEVEL THAT SEPARATE THE RESIDENTIAL USE FROM DIRECT SLAB-ON-GRADE CONTACT; THIS EXCEEDS THE RADON CONTROL REQUIREMENTS LISTED IN SECTION 1812. WE UNDERSTAND THIS STRATEGY OF RADON CONTROL HAS BEEN APPROVED THROUGH THE FOLLOWING APPEALS: APPEAL ID 12045, 10907, 10533.