华北理工大学土木工程中英文1教程.doc

学 号：200804010305  HEBEI UNITED UNIVERSITY 毕业设计外文 GRADUATE DESIGN 设计题目：唐山市中山宾馆建筑结构设计 学生姓名：史知广 专业班级：08土木3班 学 院：建筑工程学院 指导教师：韩建强 副教授 2012年05月25日 外文 Prestressed Concrete Concrete is strong in compression,but weak in tension:its tensile strength varies from 8 to 14 percent of its compressive strength. Due to such a love tensile capacity ,flexural cracks develop at early stages of loading .In order to reduce or prevent such cracks from developing, a concentric or eccentric force is imposed in the longitudinal direction of the structural element. This force prevents the cracks from developing by eliminating or considerably reducing the tensile stresses at the critical midspan and support sections at service load,thereby raising the bending,shear,and torsiona capacity of the concrete in compression can be efficiently utilized across the entire depth of the concrete sections when all loads act on the structure. Such an imposed longitudinal force is called a prestressing force,i.e.,a compressive force that prestresses the sections along the span of the structural element prior to the application of the transverse gravity dead and live loads or transient horizontal live loads.The type of prestressesing force involved,together with its magnitude,are determined mainly on the basis of the type of system to be constructed and the span length and slenderness desired.Since the prestressing force is applied longitudinally along or parallel to the axis of the member, the prestressing principle involved is commonly known as linear prestressing. Circular prestressing, used in liquid containment tanks, pipes, and pressure reactor vessels, essentially follows the same basic principles as does linear prestressing, The circumferential hoop, or”hugging” stress on the cylindrical or spherical structure, neutralizes the tensile stresses at the outer fibers of the curvilinear surface by the internal contained pressure. It is plain that permanent stresses in the prestressed structura