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    Permanence¡¡¡¡Steel frames that are properly maintained£¨Î¬»¤£©will last indefinitely£¨³¤Æڵأ©. Research on some of the newer steels indicates that under certain conditions no painting£¨Í¿Æᣩmaintenance whatsoever £¨Ò»µãÒ²²»£©will be required.

    ³Ö¾ÃÐÔ¡¡¡¡Êʵ±Î¬»¤µÄ¸Ö¿ò¼Ü½«»á³¤ÆÚµØά³ÖÏÂÈ¥¡£¶ÔһЩ½ÏиֲĵÄÑо¿ÏÔʾÔÚijЩÌõ¼þÏ£¬Ò»µãÒ²²»ÐèҪͿÆáµÄά»¤¡£
    Ductility¡¡¡¡The property of a material by which it can withstand extensive£¨´óÁ¿µÄ£©deformation without failure under high tensile stresses is said to be its ductility. When a mild£¨µÍ̼£©or low-carbon structural steel member is being tested in tension£¨ÊÜÀ­²âÊÔ£©, a considerable£¨Ï൱´óµÄ£©reduction in cross section and a large amount elongation will occur at the point of failure before the actual fracture occurs. A material that does not have this property is generally unacceptable and is probably hard and brittle and might break if subjected to a sudden shock£¨³å»÷£©.

    ÑÓÐÔ¡¡¡¡²ÄÁÏÔڸߵÄÀ­Ó¦Á¦ÏÂÄܳÐÊÜ´óµÄ±äÐζø²»ÆÆ»µµÄÐÔÄܱ»³ÆΪÊÇÑÓÐÔ¡£µ±Ò»¸ùµÍ̼½á¹¹¸Ö¹¹¼þÕýÔÚ½øÐÐÊÜÀ­²âÊÔʱ£¬ÔÚʵ¼ÊµÄ¶ÏÁÑ·¢Éú֮ǰ£¬ÔÚÆÆ»µµã´¦½«»á·¢Éúºá¶ÏÃæµÄ´ó´óËõСÒÔ¼°²úÉúºÜ´óµÄÉ쳤¡£²»¾ßÓÐÕâÖÖÐÔÄܵIJÄÁÏͨ³£ÊDz»±»½ÓÊܵÄ£¬²¢ÇҸòÄÁÏ¿ÉÄÜÊǼáÓ²ºÍ´àÐԵģ¬Èç¹û³ÐÊÜÒ»¸öͻȻµÄ³å»÷£¬¿ÉÄÜ»á¶ÏÁÑ¡£
    ¡¡¡¡In structural members under normal£¨Õý³£µÄ£©loads, high stress concentrations develop£¨Ðγɣ©at various points. The ductile nature of the usual£¨ÆÕͨµÄ£©structural steels enables them to yield locally at those points, thus preventing premature£¨¹ýÔçµÄ£©failures. A further£¨ÁíÒ»¸ö£©advantage of ductile structures is that when overloaded their large deflections give visible £¨Ã÷ÏԵģ©evidence of impending failure£¨¼´½«ÆÆ»µµÄ¼£Ïó£©(sometimes jokingly referred to as “running time” “ÌÓÅÜʱ¼ä”).

             ÔÚÕý³£ºÉÔØϵĽṹ¹¹¼þÖУ¬ÔÚ²»Í¬µÄµãÉÏ»áÐγɸßÓ¦Á¦¼¯ÖС£ÆÕͨ½á¹¹¸ÖÑÓÐÔµÄÌصãʹËüÃÇÔÚÕâЩµãÉϾֲ¿µØÇü·þ£¬ÕâÑù×èÖ¹Á˹ýÔçµÄÆÆ»µ¡£ÑÓÐԽṹµÄÁíÒ»¸öÓÅÊÆÊǵ±³¬ÔØʱ£¬ËüÃǵĴó±äÐÎÏÔʾ³öÃ÷ÏԵļ´½«ÆÆ»µµÄ¼£Ïó£¨ÓÐʱºòÏ·³ÆΪ“ÌÓÅÜʱ¼ä”£©¡£
    In Fracture Toughness¡¡¡¡Structural steels are tough£¨¼áÈ͵ģ©; that is, they have both strength and ductility. A steel member loaded until it has large deformations will still be able to withstand large forces. This is a very important characteristic because it means that steel members can be subjected to large deformations during fabrication and erection£¨°²×°£©without fracture – thus allowing them to be bent, hammered, sheared£¨¼ôÇУ©, and have holes punched£¨³å¿×£©in them without visible damage. The ability of a material to absorb energy in large amounts is called toughness”).

    ¶ÏÁÑÈÍÐÔ¡¡¡¡½á¹¹¸ÖÊǼáÈ͵ģ»Ò²¾ÍÊÇ˵£¬ËüÃǼÈÓÐÇ¿¶ÈÓÖÓÐÑÓÐÔ¡£Ò»¸ù¸Ö¹¹¼þ¼ÓºÉÖÁ´ó±äÐÎʱ½«ÈÔÈ»Äܹ»³ÐÊÜ´óµÄÁ¦¡£ÕâÊǷdz£ÖØÒªµÄÌØÐÔ£¬ÒòΪÕâÒâζןֹ¹¼þÔÚÖÆ×÷ºÍ°²×°ÆÚ¼äÄܳÐÊÜ´óµÄ±äÐζø²»¶ÏÁÑ—Õâ¾ÍÔÊÐíËüÃDZ»ÍäÇú¡¢´¸»÷¡¢¼ôÇÐÒÔ¼°ÔÚÉÏÃæ³å¿×¶øûÓÐÃ÷ÏÔµÄË𺦡£²ÄÁÏÎüÊÕ´óÁ¿ÄÜÁ¿µÄÄÜÁ¦³ÆΪÈÍÐÔ¡£
    Additions to Existing Structures¡¡¡¡Steel structures are quite well£¨Ï൱£©suited to having additions made to them. New bays£¨½Ú¼ä£©or even entire£¨Õû¸ö£©new wings£¨Òí£©can be added to existing steel frame buildings, and steel bridges may often be widened.

    ÔÚ¶ÔÒÑÓнṹµÄÌí¼Ó¡¡¡¡¸Ö½á¹¹Ï൱Êʺ϶ÔÆä×ÔÉí½øÐÐÌí¼Ó¡£ÐµĽڼä¡¢ÉõÖÁÕû¸öеÄÒíÄܱ»Ìí¼Óµ½ÒÑÓеĸֿò¼Ü½¨ÖþÉÏ£¬Òò´Ë¸ÖÇų£³£¿ÉÒÔ±»¼Ó¿í¡£
    Miscellaneous¡¡¡¡Several other important advantages of structural steel are: (a) ability to be fastened together by several simple connection devices£¨·½·¨£© including welds and bolts; (b) adaptation to prefabrication£¨Ô¤ÖÆ£©; (c) speed of erection; (d) ability to be rolled into a wide variety of £¨¸÷ÖÖ¸÷ÑùµÄ£© sizes and shapes; (e) fatigue strength; (f) possible reuse£¨ÔÙÀûÓã©after a structure is disassembled£¨·Ö½â£©, and (g) scrap value£¨²ÐÓà¼ÛÖµ£©, even though not reusable£¨¿ÉÔÙÀûÓõģ©in its existing form. Steel is the ultimate recyclable£¨¿ÉÑ­»·µÄ£©material.

    ÆäËü¡¡¡¡½á¹¹¸ÖÆäËüµÄһЩÖØÒªÓŵãÊÇ£º£¨a£©Äܹ»Í¨¹ýһЩ¼òµ¥µÄÁ¬½Ó·½·¨°üÀ¨º¸·ìºÍÂÝ˨½«ÆäÁ¬½ÓÆðÀ´£»£¨b£©ÊʺÏÔ¤ÖÆ£»£¨c£©°²×°Ëٶȣ»£¨d£©Äܹ»ÔþÖƳɸ÷ÖÖ¸÷ÑùµÄ³ß´çºÍÐÎ×´£»£¨e£©Æ£ÀÍÇ¿¶È£»£¨f£©Ôڽṹ±»·Ö½âºó¿ÉÄܵÄÔÙÀûÓã»ÒÔ¼°£¨g£©²ÐÓà¼ÛÖµ£¬¼´Ê¹²»ÄÜÒÔÆäÒÑÓеÄÐÎʽ±»ÔÙÀûÓ᣸ֲÄÊÇ×îÖÕ¿ÉÑ­»·µÄ²ÄÁÏ¡£
Disadvantages of Steel as a Structural Material
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In general, steel has the following disadvantages.

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Maintenance Costs¡¡¡¡Most steels are susceptible to£¨Ò×ÊÜ..Ó°Ï죩corrosion£¨ÐâÊ´£©when freely£¨Ö±½ÓµØ£© exposed to air and water and must therefore be periodically£¨¶¨Ê±µØ£©painted. The use of weathering£¨·ç»¯£©steels, in suitable design applications, tends to eliminate£¨±ÜÃ⣩this cost.