【正文】 trongly bonded to the concrete, a strong, stiff, and ductile construction material is produced. This material, called reinforced concrete, is used extensively to construct foundations, structural frames, storage takes, shell roofs, highways, walls, dams, canals, and innumerable other structures and building products. Two other characteristics of concrete that are present even when concrete is reinforced are shrinkage and creep, but the negative effects of these properties can be mitigated by careful design. A code is a set technical specifications and standards that control important details of design and construction. The purpose of codes it produce structures so that the public will be protected from poor of inadequate and construction. Two types f coeds exist. One type, called a structural code, is originated and controlled by specialists who are concerned with the proper use of a specific material or who are involved with the safe design of 青島理工大學(xué)畢業(yè)設(shè)計（論文） 第 96 頁 a particular class of structures. The second type of code, called a building code, is established to cover construction in a given region, often a city or a state. The objective of a building code is also to protect the public by accounting for the influence of the local environmental conditions on construction. For example, local authorities may specify additional provisions to account for such regional conditions as earthquake, heavy snow, or tornados. National structural codes genrally are incorporated into local building codes. The American Concrete Institute ( ACI ) Building Code covering the design of reinforced concrete buildings. It contains provisions covering all aspects of reinforced concrete manufacture, design, and construction. It includes specifications on quality of materials, details on mixing and placing concrete, design assumptions for the analysis of continuous structures, and equations for proportioning members for design forces. All structures must be proportioned so they will not fail or deform excessively under any possible condition of service. Therefore it is important that an engineer use great care in anticipating all the probable loads to which a structure will be subjected during its lifetime. Although the design of most members is controlled typically by dead and live load acting simultaneously, consideration must also be given to the forces produced by wind, impact, shrinkage, temperature change, creep and support settlements, earthquake, and so forth. The load associated with the weight of the structure itself and its permanent ponents is called the dead load. The dead load of concrete members, which is substantial, should never be neglected in design putations. The exact magnitude of the dead load is not known accurately until members have been sized. Since some figure for the dead load must be used in putations to size the members, its magnitude must be estimated at first. After a structure has been analyzed, the members sized, and architectural details pleted, the dead load can be puted more accurately. If the puted dead load is approximately equal to the initial estimate of its value ( or slightly less ), the design is plete, but if a significant difference exists between the puted and estimated values of dead weight, the putations should be revised using an improved value of dead load. An accurate estimate of dead load is 青島理工大學(xué)畢業(yè)設(shè)計（論文） 第 97 頁 particularly important when spans are long, say over 75 ft ( m ), because dead load constitutes a major portion of the design load. Live loads associated with building use are specific items of equipment and occupants in a certain area of a building, building codes specify values of uniform live for which members are to be designed. After the structure has been sized for vertical load, it is checked for wind in bination with dead and live load as specified in the code. Wind loads do not usually control the size of members in building less than 16 to