Guidelines for Roof Mounted Outdoor Air-Conditioner Installations, 1992, Air- Conditioning & Refrigeration Institute, Arlington, Va., National Roofing Contractors Association, Rosemont, Ill., Sheet Metal and Air Conditioning Contractors National Association Inc., Chantilly, Va. C. W. Griffin and Richard Fricklas, The Manual of Low-Slope Roof Systems, 1996, McGraw-Hill, New York, N.Y. Quality Control Guidelines in Application of Built-Up Roofing, 1993, Asphalt Roofing Manufacturers Association, Calverton, Md., National Roofing Contractors Association, Rosemont, Ill. The Manual for Inspection and Maintenance of Built-Up and Modified Bitumen Roof Systems: A Guide for Building Owners, 1996, Asphalt Roofing Manufacturers Association, Calverton, Md., National Roofing Contractors Association, Rosemont, Ill. Quality Control Guidelines for the Application of Polymer Modified Bitumen Roofing, 1996, Asphalt Roofing Manufacturers Association, Calverton, Md., National Roofing Contractors Association, Rosemont, Ill. Quality Control Guidelines for the Applications of Thermoset Single-Ply Roof Membranes, 1997, National Roofing Contractors Association, Rosemont, Ill., Single Ply Roofing Institute, Needham, Mass. SPRI/NRCA Manual of Roof Inspection, Maintenance, and Emergency Repair for Existing Single-Ply Roofing Systems, 1992, National Roofing Contractors Association, Rosemont, Ill., Single Ply Roofing Institute, Needham, Mass. Quality Control Guidelines for the Application of Sprayed Polyurethane Foam Roofing, 1997, National Roofing Contractors Association, Rosemont, Ill., Spray Polyurethane Foam Division, Washington, D.C. The Manual for Inspection and Maintenance of Spray Polyurethane Foam-Based Roof Systems: A Guide for Building Owners, 1998, National Roofing Contractors Association, Rosemont, Ill., Spray Polyurethane Foam Division,Washington, Repair Manual for Low-Slope Membrane Roof Systems, 1997, Asphalt Roofing Manufacturers Association, Calverton, Md., National Roofing Contractors Association, Rosemont, Ill., Single Ply Roofing Institute, Needham, Mass. Steep-Slope Roofing Materials Guide, 2000, National Roofing Contractors Association,

Assumptions in design of total losses in tendon stress of 35,000 psi for pretensioning and 25,000 psi for posttensioning to allow for elastic shortening, frictional losses, slip at anchorages, shrinkage, creep, and relaxation of the prestressing steel FIGURE 9.61 Prestressed-concrete beam: (a) with straight tendons; (b) with curved tendons; (c) midspan stresses with straight or curved tendons; (d) stresses between midspan and supports with curved tendons. Net stresses near the supports become tensile with straight tendons. usually gives satisfactory results. Losses greater or smaller than these values have little effect on the design strength but can affect service-load behavior, such as cracking load, deflection, and camber. Elastic Shortening of Concrete. In pretensioned members, when the tendons are released from fixed abutments and the steel stress is transferred to the concrete by bond, the concrete shortens under the compressive stress. The decrease in unit stress in the tendons equals PsEs /AcEc
nc, where Es is the modulus of elasticity of the steel, psi; Ec the modulus of elasticity of the concrete psi; n the modular ratio, Es /Ec; c the unit stress in the concrete, psi; Ps the prestressing force applied by the tendons; and Ac the cross-sectional area of the member. In posttensioned members, the loss due to elastic shortening can be eliminated by using the members as a reaction in tensioning the tendons. Frictional Losses. In posttensioned members, there may be a loss of prestress where curved tendons rub against their enclosure. The loss may be computed in terms of a curvature-friction coefficient . Losses due to unintentional misalignment may be calculated from a wobble-friction coefficient K (per lin ft). Since the coefficients vary considerably, they should, if possible, be determined experimentally. A safe range of these coefficients for estimates is given in the Commentary on ACI 318-99, American Concrete Institute. Frictional losses can be reduced by tensioning the tendons at both ends, or by initial use of a larger jacking force which is then eased off to the required initial force for anchorage. Slip at Anchorages. For posttensioned members, prestress loss may occur at the anchorages during the anchoring. For example, seating of wedges may permit some shortening of the tendons. If tests of a specific anchorage device indicate a shortening L, the decrease in unit stress in the prestressing steel is equal to EsL/L, where L is the length of the tendon. This loss can be reduced or eliminated by overtensioning initially by an additional strain equal to the estimated shortening. Shrinkage of Concrete. Change in length of a member caused by concrete shrinkage results in a prestress loss over a period of time. This change can be determined from tests or experience. Generally, the loss is greater for pretensioned members than for posttensioned members, which are prestressed after much of the shrinkage has occurred. Assuming a shrinkage of 0.0002 in / in of length for a pretensioned member, the loss in tension in the tendons is 0.0002Es
0.0002  30  106

Individual room 1 per room 1 per room 1 per room Ward room 1 per 8 patients 1 per 10 patients 1 per 20 patients 1 per 75 Hospital waiting rooms 1 per room 1 per room 1 per 75 Hospitals Male Female Male Female for employee use 1 for 115 1 for 115 0 for 19 1 per 40 1 per 40 2 for 1635 3 for 1635 1 for 1050 3 for 3655 4 for 3655 Over 55, add 1 fixture for Add one fixture for each each additional 40 persons additional 50 males Penal Institutions 1 per cell block for prison use floor (Continued) TABLE 14.2 Minimum Plumbing Fixtures for Various Occupanciesa Type of building Bathtubs or Drinking or occupancy Water closets b Urinals Lavatories showers fountains c (Continued) Cell 1 per cell 1 per cell 1 per exercise Exercise room 1 per exercise room 1 per exercise room 1 per exercise room room Penal Institutionsfor Male Female Male Female 1 per 75 employee use 1 for 115 1 for 115 0 for 19 1 per 40 1 per 40 2 for 1635 3 for 1635 1 for 1050 3 for 3655 4 for 3655 Add one fixture for each Over 55, add 1 fixture for each additional 50 males additional 40 persons Worship places, principal Male Female 1 per 150 1 per 2 water closets 1 per 75 assembly place 1 per 150 1 per 75 2 for 151300 2 for 76150