Subsection [BS] 805.3 - Existing structural elements carrying lateral loadsExcept as permitted by Section 503.13, where the alteration increases design lateral loads, results in prohibited structural irregularity as defined in ASCE 7, decreases the capacity of any existing lateral load-carrying structural element, the structure of the altered building or structure shall meet the requirements of Sections 1609 and 1613 of the International Building Code. Reduced seismic forces shall be permitted.
Exception:
1. Any existing lateral load-carrying structural element whose demand capacity ratio with the alteration considered is not more than 10 percent greater than its demand-capacity ratio with the alteration ignored shall be permitted to remain unaltered. For purposes of calculating demand-capacity ratios, the demand shall consider applicable load combinations with design lateral loads or forces in accordance with International Building Code Sections 1609 and 1613. Reduced seismic forces shall be permitted. For purposes of this exception, comparisons of demand-capacity ratios and calculation of design lateral loads, forces and capacities shall account for the cumulative effects of additions and alterations since original construction. Add exception as follows.
2. Buildings in which the increase in the demand-capacity ratio is due entirely to the addition of rooftop-supported mechanical equipment individually having an operating weight less than 400 pounds (181.4 kg) and where the total additional weight of all rooftop equipment placed after initial construction of the building is less than 10 percent of the roof dead load. For purposes of this exception, "roof" shall mean the roof level above a particular story. 904.1.1High-rise buildings. Delete the word municipal before the word water.780 CMR, ch. 34, pt. 1, 307, [BS] 805.3
Amended by Mass Register Issue 1532, eff. 10/11/2024.