section 9.0 structural design

SECTION 9.0 Structural Design

SECTION 9.0 - STRUCTURAL DESIGN

9.1 INTRODUCTION 9.1.1 General Requirements The structural system and materials shall be suitable for permanent facilities, capable of carrying the required loads, and compatible with fire protection requirements and architectural and functional concepts. Structural systems and materials not already defined in these standards shall be selected for economy, general availability, desirability, resistance to fire, aesthetic impact, and low maintenance costs over the design life of the facility. In selecting the type of structural system, the total cost of the facility shall be considered in conjunction with utilities, HVAC, lighting, finish materials, and other architectural features. In choosing miscellaneous structural materials for this project, consideration shall be given to the site environment, climate, subsurface conditions, accessibility, wind velocity and seismic ratings, skill and experience of prospective contractors, the design life of the facility and maintenance cost over this period, availability of labor and materials, and the feasibility of pre-assembling or pre-casting major structural elements. For simple rectangular building plans, consider the use of pre-engineered metal structural systems. As an example, the reduced-scope design of the Consolidated Support Center uses a pre-engineered metal frame that is economical and adaptable to future functions. 9.1.2 Design Loads The source for design loads and load conditions for new structures and/or rehabilitation of existing structures is American Society of Civil Engineers Manual 7, Minimum Design Loads for Buildings and Other Structures. (Note that Manual 7 has wind loadings and factors which are different from current building codes.) Consideration should be given to the use of bearing walls, because past designs indicate their economic advantages. Any design using a column-and-beam system must be analyzed to determine the most economical system. Floor, ceiling, and roof structures should be investigated to determine the most economical system consistent with the desired acoustical attenuation. Walls and partitions should be held to a minimum thickness to obtain maximum livable areas within the gross area limitations.

Foundations for the Global Hawk Dorms

Rebar and formwork

Reinforced truck aprons at fuel farm


The selection of walls and partition systems must take into consideration acoustical separation, fire protection, maintenance, structural requirements, and utility systems. Design Notes. Include general structural notes on drawings such as: roof, floor, wind and seismic loads; material types and design stresses; unusual members’ sectional properties; survey references; and other pertinent notes relating to conformance to codes or construction practices. Compatibility with Finishes. Structural systems that require the use of cast in place concrete in conjunction with concrete masonry units should be carefully designed and detailed to present an attractive and acceptable appearance allowing for expansion/contraction and not allowing any leakage.

Global Hawk dorms in construction

Metal stud and drywall interior partition provide economical room enclosures

Concrete reinforcement


9.2 GENERAL DESIGN CRITERIA Structural design and construction shall comply with the criteria below and/or those dictated by DoD. General structural design should follow the latest edition of the UBC or 2001 CBC. 1) Beale AFB is located in Seismic Zone 3 classified per

latest edition of the UBC. Nearness factors to be used as follows: Na = 1.0; Nv = 1.0

2) Wind design criteria is as follows: design wind speed = 85 mph, Exposure C

3) The above requirements shall be evaluated against the latest version of the American society of Civil Engineers, “Minimum Design Loads for Buildings and Other Structures.” The more stringent of the criteria shall be followed.

9.2.1 Geology Soils on the hilly eastern portion of the base are gravelly and rocky with depth to bedrock varying from 10-inches to 40-inches. Occasional rock outcrops occur. The flatter central and western areas of the base have gravelly loam and gravelly clay soils of alluvial origin. Impervious hardpan or claypan layers are common to these soils, and over-compaction from previous training operations often exists, creating constraints on construction and landscape development. Soil borings are required for all subsurface design. For more information about soils on base, refer to the Soil Survey of Beale AFB (Soil Conservation Service, 1985). 9.2.2 Frost Depth 1) The ground at Beale AFB is not subject to deep

ground freezing but is subject to surface frost. 2) Foundations and pipe shall be placed at elevations

appropriate for the respective uses. 9.2.3 Structural Systems 1) Structural systems shall comply with all applicable

DoD and other government criteria and guidance. 2) Structural systems shall conform to industry

standards and shall use commonly accepted methods of practice.

Mission Control Tech Building

Foundations and pipe placed at appropriate elevations

Cast in place concrete slab


3) When selecting an appropriate structural system, the following elements shall be evaluated and addressed:

a) Quantify the total life cycle cost effectiveness of the structural system.

b) Review the design for constructability. c) Determine the experience level of the local

contractors and labor force. d) Consider the existing and projected bid climate

in the area. e) Verify the availability and use of local materials. f) Consider the opportunity to incorporate

sustainable design features into the system design.

9.2.4 Geotechnical Report The geotechnical report shall be performed by the A/E and prescribe foundation requirements for new project facilities. These requirements shall include but are not limited to the following design parameters: 1) Define bearing values for alternate foundations

systems (i.e., drilled pier, spread footings, etc.), along with settlement characteristics for each system.

2) Define the expansion characteristics of the soil. 3) Define active (unrestrained conditions), at-rest

(restrained) and passive earth pressures. Acknowledge an increase in allowable earth pressure values for seismic and wind loads.

4) Define the shear strength characteristics of all soil layers. Laboratory shear testing should be performed on undisturbed samples of cohesive soils and in-situ testing (SPT, CPT, etc.) should be performed on cohesionless soils.

5) Define the sub-grade preparation and modulus of sub-grade reaction for slabs on grade.

6) Consider any unique site conditions such as existing structures, septic tanks, old fill, certified fill, perched water table, etc.

7) Address potential drainage problems that may influence the structural design.

8) Make recommendations regarding inspection of

foundations.

Aero Club metal structural framing

Metal reinforcement for Global Hawk dorms

Steel framing system on concrete foundation detail


9) Define the seismic parameters required by ASCE 7. 10) Define the depth of frost penetration. 11) Make recommendations for special types of cement

for concrete on and below grade. 9.2.5 Requirement for Seismic and Wind Analysis 1) All new construction and all major renovations to

existing buildings shall have a seismic and wind analysis completed by a registered structural engineer. Major items that can trigger this requirement include but are not limited to: a) Removal/alteration of shear walls b) Removal/alteration of load-bearing elements c) Alteration of roof systems d) Alteration of foundation elements

2) A seismic evaluation of major facilities was conducted in 1997 by Winzler & Kelly Consulting Engineers. Copies can be furnished up request; however, the requirements listed above are still valid.

9.2.6 Foundations The average design soil load bearing capacity for the base is 1500 - 3000 psi based upon previous design and construction experience in the area. The A/E shall confirm the soil bearing load capacity at the project site prior to beginning design. 1) Base facilities are normally constructed on

continuous foundations. Deep foundation systems should be evaluated when large loads are being distributed to the soil mass or when the floating slab approach cannot achieve the desired support elements.

2) Foundations constructed on fill shall be designed to keep overall settlements to less than 25 mm and differential settlements to 12 mm.

3) Under any main roads or taxiways, a tunnel system shall be used for drainage.

Concrete slab preparation for Building 1200

Aggregate fill for slab foundation


9.3 SITE CONSTRUCTION 9.3.1 Basic Site Materials and Methods Environmental Protection Environmental Impact Analysis Process (EIAP) The design agent is required to have a completed Environmental Impact Analysis Process (EIAP) document in the project folder before the design is completed. The design agent should demonstrate that the required environmental issues, permits, and mitigations have either been accounted for in the contract documents or that the Environmental Flight has accepted responsibility (in writing) for the required mitigations. 9.3.1.1 Existing Paint The contractor should assume that all existing paint on all exterior surfaces contains lead unless otherwise determined by a state certified hazardous material consultant/survey. Areas specially coated with lead-containing paint include fascias, eaves, joists, painted brick or concrete, around all windows and doors, and vertical wood louvers at garages. 9.3.2 Site Preparation, Earthwork, Tunneling, Boring and Jacking, Foundation and Load-bearing Elements, Roads and Parking Lots Use 2-inch minimum asphalt concrete on 6-inch Class 2 aggregate base. The Architect/Engineer (A/E) shall conform to CalTrans Standards and shall be manufactured at local approved batch plants. 9.3.3 Utility Services Water required flow at peak demands should be ample at 40 psi minimum pressure. Existing water in the area has already been treated and is potable. Cathodic protection is required on any metallic piping. Use Schedule 40 PVC for solvent cement joint and Schedule 80 PVC for screwed-joint piping for underground service and galvanized steel for aboveground (outside). Install a water meter at each new facility. Disinfect the plumbing lines in accordance with AWWA and UPC standards and provide for bacteriological and pressure testing of the water after the building is completed.

Mission Control Tech Building

Slab and column detail


All underground water meters shall be provided with a concrete box with sufficient size to enclose the meter and shutoff valve plus 6 in all-around clearances for maintenance and repair. The lid shall have the word “WATER” cast on it. 9.3.4 Sanitary Sewage The minimum service size for a new facility shall be 6-inch PVC. If required, a new 6-inch or 8-inch main shall be designed and constructed to serve the site from the closest manhole which can be reached via gravity flow. The A/E shall study the most economical gravity sewer design option. Verify capacities of existing sewer to handle additional flows once they are determined. A sanitary sewer master plan is available from the Base Civil Engineer. 9.3.4.1 Manholes and Cleanouts Use standard precast manholes with nominal 25-inch diameter cast iron cover. Maximum manhole spacing shall be 400-feet. A new manhole or cleanout shall be required if there is a significant change in direction for the new line. Minimum wastewater flow velocity is 2-feet per second. 9.3.4.2 Pipeline Clearance and Obstructions Insure that adequate separation exists between water and sewer mains (typically 10-feet minimum). Landscaping plans shall include a utility layer and insure that planter areas are not overlying the utility lines. Utility crossings should not be in close proximity to trees due to root intrusion in the sewer lines. 9.3.5 Repair/Renovation of Existing Buildings Contract documents will transfer risk to the contractor as the party responsible for identifying and abating hazardous materials such as asbestos and lead containing materials. Include a hazardous material survey by State certified asbestos and lead consultant to identify asbestos containing and lead containing materials, their location and quantities, as part of the design. Include asbestos and lead based paint abatement as a contractor responsibility if they are known or potentially present in the building areas to be disturbed. The design agent shall consult with the base Cultural Resources Manager early in the design process to determine if consultation with the State Historic Preservation Office is required before remodeling an existing building.

Sewage lines under slab


9.3.6 Drainage and Containment 9.3.6.1 Site Drainage Drainage shall generally be surface drainage away from building with paved areas sloping a minimum of one percent; earth areas a minimum of 2%; and pipes, gutters and swales a minimum of 0.5%. Use bituminous coated CSP (Corrugated Steel Pipe) or RCP (Reinforced Concrete Pipe) for culverts. Use precast concrete catch basins with cast iron grates. Provide concrete splash blocks at outlets of downspouts. Where slope exceeds 20%, a system of erosion control should be provided. A new manhole or cleanout shall be provided in piping when there is a significant change in direction per UPC requirements. 9.3.6.2 Soil and Foundation Conditions Site specific soil borings are required to determine soil bearing, pH, and resistivity characteristics. Blueprints of boring logs for Beale AFB are available. The ground water table is low enough such that is has not been a factor for foundation design at Beale AFB. Hardpan/claypan soil is common on Beale AFB; specifications should include requirements for dealing with these soils if encountered. 9.4 REFERENCES Refer to the following sections for relationship to structural design issues: Section 3.0 - Site Design Section 4.0 - Landscape Design Section 12.0 - Force Protection Section 13.0 - Sustainable Design Section 15.0 - Environmental Standards Section 16.0 - General Provisions for Construction for contractor’s obligations. Section 17.0 - CADD/GIS Drawing Standards Refer to Appendix B for applicable references, codes, and regulations.

Grading for drainage

section 9.0 structural design

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