承受平面内剪应力和正应力的钢筋混凝土和预应力混凝土薄膜元的软化桁架模型已经发展起来。这种模型满足二维应力平衡条件、莫尔应变协调条件和混凝土的双轴软化本构关系。它不仅能预估薄膜元的强度，而且能表达荷载－变形关系的全过程。本文叙述了两种软化桁架模型，它们的区别是对混凝土压杆角度的假定不同。首先概述已完整建立起来的转角软化桁架模型，然后给出定角软化桁架模型的新发展。 Reinforced concrete and prestressed concrete membrane element softening truss models that withstand in-plane shear stress and normal stress have been developed. This model satisfies two-dimensional stress equilibrium conditions, Mohr strain coordination conditions, and biaxial softening constitutive relations of concrete. It can not only predict the strength of the thin film element, but also express the whole process of the load-deformation relationship. This article describes two softened truss models, the difference being the assumption of different angles for the concrete struts. First, we outline the corner softening truss model that has been completely established, and then give a new development of the fixed angle softened truss model.