6.5.6 Settlement of Cohesive and Organic Soils Cohesive and organic soil can be susceptible to a large amount of settlement from structural loads. It is usually the direct weight of the structure that causes settlement of the cohesive or organic soil. The settlement of saturated clay or organic soil can have three different components: immediate (also known as initial settlement), primary consolidation, and secondary compression. Immediate Settlement. In most situations, surface loading causes both vertical and horizontal strains. This is referred to as two- or three-dimensional loading. Immediate settlement is due to undrained shear deformations, or in some cases contained plastic flow, caused by the two- or three-dimensional loading. Common examples of three-dimensional loading are from square footings and round storage tanks. Many different methods are available to determine the amount of immediate settlement for two- or three-dimensional loadings. Examples include field plate load tests, equations based on the theory of elasticity, and the stress path method (see R. W. Day, Geotechnical and Foundation Engineering: Design and Construction, Mc- Graw-Hill Publishing Co., New York). Primary Consolidation. The increase in vertical pressure due to the weight of the structure constructed on top of saturated soft clays and organic soil will initially be carried by the pore water in the soil. This increase in pore water pressure is known as an excess pore water pressure (ue). The excess pore water pressure will decrease with time as water slowly flows out of the cohesive soil. This flow of water from cohesive soil (which has a low permeability) as the excess pore water pressures slowly dissipate is known as primary consolidation, or simply consolidation. As the water slowly flows from the cohesive soil, the structure settles as the load is transferred to the soil particle skeleton, thereby increasing the effective stress of the soil. Consolidation is a time-dependent process that may take many years to

Type of construction of a building is determined, in general, by the fire ratings assigned to its components. A code usually establishes two major categories: combustible and noncombustible construction. The combustible type may be subdivided in accordance with the fire protection afforded major structural components and the rate at which they will burn; for example, heavy timber construction is considered slow-burning. The noncombustible type may be subdivided in accordance with the fire-resistive characteristics of components. Building codes may set allowable floor areas for fire-protection purposes. The limitations depend on occupancy group and type of construction. The purpose is to delay or prevent spread of fire over large portions of the building. For the same reason, building codes also may restrict building height and number of stories. In addition, to permit rapid and orderly egress in emergencies, such as fire, codes limit the occupant load, or number of persons allowed in a building or room. In accordance with permitted occupant loads, codes indicate the number of exits of adequate capacity and fire protection that must be provided. Like building codes, zoning codes are established under the police powers of the state, to protect the health, welfare, and safety of the public. Zoning, however, primarily regulates land use by controlling types of occupancy of buildings, building height, and density and activity of population in specific parts of a jurisdiction. Zoning codes are usually developed by a planning commission and administered by the commission or a building department. Land-use controls adopted by the local planning commission for current application are indicated on a zoning map. It divides the jurisdiction into districts, shows the type of occupancy, such as commercial, industrial, or residential, permitted in each district, and notes limitations on building height and bulk and on population density in each district. The planning commission usually also prepares a master plan as a guide to the growth of the jurisdiction. A future land-use plan is an important part of the master plan. The commissions objective is to steer changes in the zoning map in the direction of the future land-use plan. The commission, however, is not required to adhere rigidly to the plans for the future. As conditions warrant, the commission may grant variances from any of the regulations. In addition, the planning commission may establish land subdivision regulations, to control development of large parcels of land. While the local zoning map specifies minimum lot area for a building and minimum frontage a lot may have along a street, subdivision regulations, in contrast, specify the level of improvements to be installed in new land-development projects. These regulations contain criteria for location, grade, width, and type of pavement of streets, length of blocks, open spaces to be provided, and right of way for utilities. A jurisdiction may also be divided into fire zones in accordance with population density and probable degree of danger from fire. The fire-zone map indicates the limitations on types of construction that the zoning map would otherwise permit. In the vicinity of airports, zoning may be applied to maintain obstruction-free approach zones for aircraft and to provide noise-attenuating distances around the FIGURE 1.11 Examples of limitations placed by zoning codes on building height: (a) height limitations for buildings constructed along lot boundaries; (b) setbacks required by a 3:1 sky exposure plane; (c) height of a sheet tower occupying only part of a lot is limited by the total floor area permitted. (Reprinted with permission from F. S. Merritt and J. Ambrose, Building Engineering and Systems Design, 2d ed., Van Nostrand Reinhold, New York.) airports. Airport zoning limits building heights in accordance with distance from

To be successful, a contracting company should have a person specifically assigned to attract new business. This person might be the proprietor of the construction company. In large firms, a complex organization with sales and public relations personnel, backed up by engineers and cost estimators, is used. The organization should be geared to follow up on all possible sources of new business. Public Works. The following sources for leads to new jobs and submitting proposals can be used for public work bids: Dodge Bulletin, or other construction industry newsletters. ENRPulse and Official Proposals sections. Bid invitations, as a result of requests to be placed on bid-invitation mailing lists of various government agencies. Newspaper and trade-paper announcements and articles. Official publications of government agencies that contain advertisements of contracts to be bid. Private Contracts. All the sources for public works. Contacts with and letters to architects and designers. Contacts with and letters to owners and facilities personnel. Personal recommendation. Sponsorship. Applying for sponsorship of any of the following: Government-encouraged housing programs. Urban redevelopment. Purchase of land, with financing of building construction to be provided by various government programs. Owner-Builder/Developer Construction and rental of apartment buildings. Construction and rental of commercial and office facilities. Construction and leasing of government buildings. Professional Construction Manager Applications to city and state agencies or large corporations awarding this type