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1.当前发展状况1977年,奥地利建成世界上第一座采用预压应力钢筋的阿尔姆(Alm)桥,引起了各国工程界的极大关注。所谓预压应力钢筋体系,是指给配置于混凝土受压区内的预应力筋施加压力,然后把它锚固,使混凝土内产生拉应力以降低该区的压应力。以简支梁为例,在“双预应力体系”情况下,即预压应力筋和传统的预拉应力筋同时并用的情况下,其跨中截面的应力状态如图1所示(此处假定了预加压力和预加拉力值相等),使截面能力得到最大限度的发挥。
1. Current Developments In 1977, Austria built the world’s first Alm bridge with prestressed steel bars, attracting great attention from the engineering community in various countries. The so-called pre-stressing rebar system refers to the prestressed tendons placed in the concrete compression zone to exert pressure, and then anchoring it, resulting in tensile stress in the concrete to reduce the area of compressive stress. In the case of simply supported beams, under the condition of “double prestressed system”, that is, when the prestressing tendons and the traditional prestressed tendons are used simultaneously, the stress state of the midsection cross section is shown in Figure 1 Assuming pre-pressure and pre-tension value equal), so that the cross-section ability to maximize the play.