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<br /> <br /> <br /> <br /> <br /> <br />3rd & Broadway, Santa Ana, CA <br />Volume 1 - Basis of Design June 17, 2024 | Project # S21043.00 <br /> pg. 32 <br />2.5.3.2 HOTEL BUILDING <br />The structural (seismic) design for the Hotel tower is based on modal response spectrum analysis. <br />A model of the Hotel with its portion of the basement ‘podium’ is constructed in ETABS. Note that <br />modeling this portion of the basement with an ‘open end’ conservatively minimizes any helpful <br />backstay effect from the basement and L1 slab. <br />The defined building mass, material properties, and geometry of the structure contribute to a <br />calculated set of periods and shapes for 30 modes using Ritz-vectors analysis, where the number <br />of modes analyzed must result in a mass participation ratio greater than 90%. The site -specific <br />response spectrum function shown in Table 2.6.2-2 is defined and applied to the model in two <br />orthogonal directions as response spectrum load cases. Along with a scale factor inversely <br />proportional to the response modification factor R/I, this produces applied story shears and an <br />overall base shear. Response spectrum forces must be scaled per ASCE 7 -16 section 12.9.1.4, <br />which stipulates that the response spectrum base shear must be scaled up to 1.0 times the <br />equivalent lateral force procedure base shear for strength design purposes. <br />Calculations of the equivalent lateral force procedure base shear and subsequent response <br />spectrum base shear are shown below. A more detailed description of the ETABS models is also <br />shown in Volume 2 Section 4.2. <br /> <br /> <br />Figure 2.5-3: ETABS 3D View for Hotel building