Project. San Jose City College Physical Education Building. Prepared For. Prepared By PLACE IMAGE HERE. Ken Bauer, AIA Principal

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1 Project San Jose City College Physical Education Building PLACE IMAGE HERE Prepared For Ken Bauer, AIA Principal LPAS 2484 Natomas Park Drive Sacramento, CA Prepared By Steve Ratchye, S.E., P.E., R.A., LEED AP BD+C Senior Associate Thornton Tomasetti Inc. 650 California Street, Suite 1400 San Francisco, CA July 9, 2014

2 1.0 INTRODUCTION This narrative offers Schematic Design structural information for the new Physical Education Building at San Jose City College (SJCC) in San Jose, California. The information presented here is preliminary and may change as design progresses. The project totals roughly 45,000 square feet. The Physical Education Building has approximately 39,000 square feet, all of which is above grade. Some of the building is twostory and some is a single story. The rest of the project will be in an existing 6000 square foot building which has previously been used for racquetball. 2.0 STRUCTURAL SYSTEMS 2.1 LATERAL The lateral force resisting system for the PE Building consists of tilt-up concrete panels acting as shear walls in both east-west and north-south directions. The structural thicknesses of the tilt wall are indicated on the accompanying lateral structure Schematic Design sketches. Assume 200 lb/cubic yard for rebar in the structural portion of the tilt walls. Thornton Tomasetti (TT) understands that LPAS plans to include a layer of rigid insulation on the outside of the structural tilt walls and also a few inches of architectural concrete at the outside face. Alternatively, LPAS may add a ¾ reveal on the outside face of the tilt walls if the insulated sandwich proves too costly. The tilt-up panels at the two-story portion are in the range of 12 to 20 feet wide and have no horizontal joints. The tilt wall panels need to be continuous from ground to some level that braces them against out-of-plane forces, such as a floor or roof. The panels at the one-story portion can be up to 40 feet wide because they are not as tall and can be kept to a weight that is economical to construct. Assume floors and roofs at the one-story portions consist of 3.25 lightweight concrete fill in 3 deep metal deck for a total slab thickness of The high roofs are all bare metal deck. Both floor and roof act as structural diaphragms. If tilt-wall panels were to prove uneconomical, the other lateral system under consideration for the Physical Education Building is steel Special Concentric Braced Frames (SCBF). It should be noted that any cost comparison of braced frames to tilt-up panels should take into account the usable floor area lost by introduction of the braces and metal stud walls as well as additional requirements for finishes and fireproofing of a steel lateral system. 2.2 GRAVITY Typically wide flange members are used as columns and beams, although in some areas rectangular steel tubes or pipes are used for architectural reasons. Columns need to be coordinated with the final architectural design, but a first pass of column layout is included in the floor plans. Assume 10 psf for gravity steel in the project typically, which includes an allowance for connections. Over the gym assume there are four structural steel trusses that span in the north-south Page 1 of 4

3 direction, and small wide flange beams that span between trusses. Assume the gym roof is 12 psf, which includes connections. Bar joists are light weight and economical and were considered for the gym roof, but these were discarded because they cannot brace the concrete walls out of plane. The tilt-wall panels carry gravity loads from roof and floor structure in addition to lateral forces such as seismic and wind. At areas where tilt walls carry beams or trusses with long spans, flat pilasters are detailed within the thickness of the wall that support the trusses and include hoops for confinement. The typical connection for girder or truss support consists of a blockout in the wall that gets grouted in after the beam is fixed in place with anchor rods cast into the wall. Beams are typically supported on continuous channels that run along the tilt walls. The ground floor consists of a normal-weight concrete slab-on-grade with rebar. Assume it s 5 thick and has #4@18 o.c. each way. The Fitness Area may have depressed areas in order to accommodate a rubber mat. Wide flange beams at this area are depressed and detailed with steel tees where necessary to accommodate the level change. Various mechanical equipment occurs at the roofs, and TT understands that some of these units will require concrete pads. The ones that do not require concrete pads will have dunnage for support. Stairs have steel stringers, and their connections are detailed to allow differential drifts between floors. The stairs in the main lobby are steel, and the stairs to the south are supported on tilt walls. 2.3 FOUNDATIONS Geosphere Consultants, Inc. has prepared a geotechnical engineering and geologic hazards study for the site at 2100 Moorpark Avenue dated March 12, The report recommends conventional spread and strip footings for the new gym. Top of footing is typically 12 below top of slab-on-grade. Assume strip footings eight feet wide and 3-0 thick under tilt-up concrete walls two stories high. Assume strip footings five feet wide and 2-0 thick under tilt-up concrete walls one story high. Assume these strip footings have 150 lb/cubic yard of reinforcement. As mentioned above, the columns are not yet placed, but they will be roughly 25 or 30 feet on center. At two story columns, assume footings 8-0 square and 2-0 thick. At one story columns, assume footings 5-0 square and 1-6 thick. The soil report states the near-surface soils at the site have a moderately low to low expansion potential, and it recommends moisture conditioning of those areas. The report goes on to state that other hazards such as collapsible soils, flooding, land-sliding, subsidence, dynamic compaction of dry sands, lateral spreading, and liquefaction are low. The report says that the sulfate content of the soil should have negligible impact and the corrosive potential of the soil is low. The groundwater levels were measured to be deeper than 50 feet. Finally, the report says that differential settlement risk is small. Page 2 of 4

4 4.0 DESIGN CRITERIA 4.1 CODES AND STANDARDS The 2013 California Building Code (CBC) with DSA amendments governs the structural design of the Physical Education Building. Other standards include the following: 1. American Concrete Institute Building Code, ACI American Institute of Steel Construction (AISC) Manual of Steel Construction, Fourteenth Edition 3. American Institute of Steel Construction (AISC) Seismic Provisions for Structural Steel Buildings, AISC American Society of Civil Engineers ASCE GRAVITY LOADS LIVE LOADS Offices, classrooms Assembly spaces, corridors, stairs, lobbies Gymnasium, fitness center Roof (maintenance access) Mechanical equipment spaces 50 psf (+ 20psf partition load where applicable) 100 psf non-reducible 100 psf 20 psf 125 psf or weight of equipment, whichever is greater. Concrete pads as required. SUPERIMPOSED DEAD LOADS Mechanical, lights, ceiling Roofing, typical Cladding, windows 10 psf 10 psf 20 psf (to be confirmed) Page 3 of 4

5 5.03 WIND PARAMETERS Exposure C Risk/occupancy category = III Basic wind speed (V) = 115 mph 5.04 SEISMIC PARAMETERS S S = 1.500g Soil report S 1 = 0.600g Soil report S DS = 1.00g Soil report S D1 = 0.600g Soil report Site Class = D Seismic Design Category = D I = 1.25 Occupancy Category = III R = 5 Special Reinforced Concrete Bearing Walls 5.05 REINFORCED CONCRETE 5.06 STEEL Structural concrete has strength as follows: 1. Foundations: normal weight concrete (145 pcf); f c = 3000 psi at 56 days 2. Tilt-Up Panels: (145 pcf); f c = 5000 psi at 28 days 3. All other concrete: normal weight concrete (145 pcf); f c=4000 psi at 28 days Reinforcement for concrete meets the following standards: 1. Mild steel reinforcement: ASTM A615 or ASTM A706, all Grade 60. Structural steel is of the following grades: 1. Wide flange sections: ASTM A992 (F y = 50 ksi) 2. Tubes: ASTM A500 Grade B (F y = 46 ksi) 3. Pipes: ASTM A500 Grade B (F y = 42 ksi) 4. Steel angles, channels & rods: ASTM A36 (F y = 36 ksi) 5. Steel plates: ASTM A572 Grade 50 (F y = 50 ksi) Page 4 of 4