There is one type of media converter worth mentioning, it changes multimode to copper at the workstation. Two versions of the media converter are the Alcatel FIGURE 18.10 Lucent 600B one-unit high-sliding combination shelf, splice tray, and patch panel. (Copyright
1999, Lucent Technologies, used by permission.) FIGURE 18.11 Lucent Lightguide Interconnection Unit, LIUs. (Copyright
1999, Lucent Technologies, used by permission.) and the 3M. The Alcatel version fits in a junction box and has two 8-pin modular jacks. The 3M version plugs into a fiber jack at the workstation and is then plugged in on, or under, the desk. The expense for the two versions is allocated differently in accounting. The Alcatel version would typically be a capital expense in the construction budget; the 3M product, typically an office expense. Previously, making a media conversion in the PC would be an expense for the IT department, along with the PC. Since fiberoptic cable is presently comparable in price with copper UTP, we may finally see a fiber that is practical for use up to the desktop. Fiberoptic connector types include SC, ST, FC, Biconic, FDDI, ESCON, MTRJ, LC, and Volition (e.g., Figs. 18.12, 18.13, and 18.14). Connectors and cables are FIGURE 18.12 Lucent STll fiberoptic connectors. (Copyright
1999, Lucent Technologies, used by permission.) FIGURE 18.13 Lucent SC fiberoptic connectors. (Copyright
1999, Lucent Technologies, used by

Stiffer cohesive soils (su  30 to 60 kPa, 600 to 1200 psf) Relatively expensive Grouting Injection of grout Deep mixing Fill soil voids with cementing agents to strengthen and reduce permeability Jetting or augers used to physically mix stabilizer and soil Wide spectrum of coarse- and finegrained soils Wide spectrum of coarse- and finegrained soils Expensive; more expensive grouts needed for finergrained soils; may use pressure injection, soil fracturing, or compaction techniques Jetting poor for highly cohesive clays and some gravelly soils; deep mixing best for soft soils up to 165 ft deep Thermal Heat Freezing Heat used to achieve irreversible strength gain and reduced water susceptibility Moisture in soil frozen to hold particles together and increase shear strength and reduce permeability Cohesive soils All soils below the groundwater table; cohesive soils above the groundwater table High energy requirements; cost limits practicality Expensive; highly effective for excavations and tunneling; high groundwater flows troublesome; slow process Geosynthetics Geogrids, geotextiles,

A limit state is defined as a condition in which a structure or structural component becomes unfit for further structural service. A structural member can have several limit states. Strength limit states relate to maximum load-carrying capacity. Serviceability limit states relate to performance under normal service conditions with respect to such factors as deflection and vibration. Design specifications establish load factors to be applied to each type of service load, such as dead, live, and wind loads, the values of the factors depending on the specific combination of loads to be imposed on a structure (Art. 5.1.3). The AISC Load and Resistance Factor Design Specification for Structural Steel Buildings requires that structures be designed so that, under the most critical combination of factored loads, the design strength of the structures or their individual elements is not exceeded. For each strength limit state, the design strength is the product of the nominal strength and a resistance factor , given in the specification. Derived with the use of probability theory,  provides an extra margin of safety for the limit state being investigated. Nominal strength of a member depends on its geometric properties, yield or ultimate strength, and type of loading to be resisted, such as tension, compression, or flexure. The AISC LRFD specification permits structural analysis based on either elastic or plastic behavior. Elastic theory is most commonly used. Where plastic theory is used for complex structures, all possible mechanisms that may form in the structure should be investigated. The collapse mechanism is the one that requires the lightest load for collapse to occur. Numerous computer programs for analysis and design of members or structures are available. If data input describing the structure and loading are accurate, most of these programs yield a quick and accurate design. For complex structures, care should be taken in use of computer programs to check the results to ensure that they are logical, since a critical input error may not be easily found. If a program can produce a plot of the configuration of the loaded structure based on the data input, the plot should be used as a check, inasmuch as omission of a member or other errors in connectivity data can be readily discerned from the plot. (Plastic Design in SteelA Guide and Commentary, M & R No. 41, American Society of Civil Engineers.) Design procedures using either the ASD or the LRFD specifications require the use of many numerical values which represent the section properties of the individual shapes or plates under consideration. Several publications in the form of handbooks have been developed by the industry to provide the designer with this and other useful information. In addition, many steel producers publish handbooks which TABLE 7.9 Handbooks and Design Guides Publisher Title Content American Institute of Steel Construction (AISC) One East Wacker Drive Chicago, IL 60601-2001 ASD Manual of Steel