(1)Systems of reinforcing concrete for strength and ductility, (2) serviceability of concrete structures

(1) 增强混凝土强度和延展性的系统，(2) 混凝土结构的适用性

• 批准号: 3319-2007
• 负责人: Ghali, Amin
• 金额: $ 3.13万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=361054
• 关键词: Systems; reinforcing; concrete; strength; ductility

1) Systems of Reinforcing Concrete for Strength and DuctilityA steel reinforcing bar in concrete can resist a force equal to its full yield strength only when it is positively anchored to the concrete. Conventional stirrups and crossties rely on hooks or bends for anchorage. However, where there is demand for the yield strength of the bar adjacent to a hook or a bend, experiments typically exhibit crushing or splitting of the concrete at the interface, accompanied by anchorage slip. Systems of steel reinforcement are developed for use in concrete in lieu of conventional stirrups and crossties. The basic component of the new systems is a stud with an anchor head at each end, capable of developing the full yield strength of the stud without slip. This anchorage quality makes the studs more efficient than conventional stirrups in providing strength and particularly ductility (essential for earthquake-resistant structures). Examples of applications of studs are: punching shear reinforcement in slabs, crossties in columns, walls and bridge piers, longitudinal bars in deep (or short) beams and corbels, and anti-splitting reinforcement at bearings and ends of prestressing tendons.(2) Serviceability of Concrete StructuresThis project aims at development of robust techniques of computing stresses and strains due to temperature, creep and shrinkage of concrete and relaxation of prestressing reinforcement and, accordingly, design the minimum reinforcement and its detailing to ensure satisfactory service life and durability. The work involves considering material and geometric nonlinearities, caused by cracking of concrete, yielding of reinforcement, presence of axial forces and use of unbonded or external prestressing tendons. The analysis considers the deformation up to failure of concrete members subjected to increasing load introduced after occurrance of creep, shrinkage and relaxation.

1)钢筋混凝土的强度和韧性系统混凝土中的钢筋只有在正锚固到混凝土上时才能抵抗等于其全部屈服强度的力。传统的箍筋和十字撑依靠钩子或弯头进行锚固。然而，如果需要弯钩或弯头附近钢筋的屈服强度，试验通常会显示混凝土在界面处压碎或劈裂，并伴随着锚固滑移。钢筋系统被开发用于混凝土中，以取代传统的箍筋和横梁。新系统的基本组件是两端都有锚头的螺柱，能够在不打滑的情况下发挥螺柱的全部屈服强度。这种锚固质量使螺柱在提供强度和特别是延性(对抗震结构至关重要)方面比传统的箍筋更有效。立柱的应用实例有：冲切楼板中的剪切钢筋，柱、墙和桥墩中的横梁，深(或短)梁和牛腿中的纵向钢筋，以及预应力筋的支座和端部的抗裂钢筋。(2)混凝土结构的适用性本项目旨在开发可靠的技术，计算由于温度、混凝土蠕变和收缩以及预应力钢筋松弛引起的应力和应变，并相应地设计最小钢筋及其细节，以确保满意的使用寿命和耐久性。这项工作涉及到考虑由混凝土开裂、钢筋屈服、轴向力的存在以及无粘结或体外预应力筋的使用而引起的材料和几何非线性。分析考虑了混凝土构件在发生徐变、收缩和松弛后，在增大荷载作用下产生的直至破坏的变形。