UHPC深梁及小剪跨区设计理论与分析方法

The ultra high performance concrete (UHPC) has been gradually used in the continuous bridges due to its high performance in tension and compression. However, the existing codes and analysis methods are still not sufficient in design of the disturbed regions (D regions) in UHPC structures. This program is devoted to develop theoretical models to design the UHPC beams with small shear span ratios and deep beams in ultimate limit state and serviceability limit state. First, an advanced strut and tie model (STM) with deformation compatibility is generated based on the principle of stationary complementary energy, for the purpose of studying the load transfer mechanisms of the UHPC beams throughout the loading process, and rational designation of UHPC beams in limit state. After that, incorporating the STM and the appropriate bond stress-slip relation under the complex stress state in the tension chord model to derive a method to evaluate the crack width analysis of the UHPC beams. Furthermore , experimental tests including UHPC beams with small shear span ratios and deep beams will be conducted, for studying the load-carrying mechanisms and validating the proposed models. In a word, this study will greatly facilitate the limit state design of D regions in UHPC bridges, and will provide effective techniques for safety and cracking control of the UHPC bridges.

超高性能混凝土（UHPC）材料因其优越的力学性能，已逐渐被应用于大跨预应力混凝土桥梁中。然而，现有的规范还不能进行UHPC梁应力扰动区（D区）的设计与分析。本课题拟以深梁和小剪跨区为研究对象，探索UHPC桥梁典型D区承载能力极限状态和正常使用状态的设计理论与分析方法。首先，拟基于余能驻值原理，建立满足变形协调的弹塑性拉压杆模型，探索UHPC深梁及小剪跨区受力全过程力流传递机制的演变规律，以期进行承载能力极限状态和正常使用状态的合理设计；其次，拟在弹塑性拉压杆模型中引入复杂应力状态下钢筋与UHPC的粘结本构关系，探讨深梁及小剪跨区裂缝宽度的计算方法；最后，还将开展模型试验，研究UHPC深梁和小剪跨区受力机制的演变规律，并验证所提出的理论模型。研究成果有助于完善现有UHPC桥梁结构极限状态设计理论框架，为保障UHPC桥梁结构的安全性提供技术支撑。

超高性能混凝土因其优越的力学性能，已逐步应用于桥梁工程中。然而，现有的UHPC设计规范还不能进行UHPC应力扰动区（D区）的设计与分析。为此，本项目首先根据模型试验研究，提出了配筋UHPC构件受拉的应力应变关系；其次，以UHPC简支深梁为研究对象，基于弹塑性拉压杆模型理论，探明了简支深梁中力流传递机理，建立了UHPC深梁在承载能力极限状态和正常使用状态时的设计理论与分析方法，并开展模型试验进行验证；最后以UHPC梁小剪跨区为研究对象，通过试验研究，探明了小剪跨区抗剪机制的演变规律，提出了基于改进修正压力场理论的抗剪承载能力计算方法，并进一步在桁架拱模型中引入弹塑性拉压杆模型理论，通过余能驻值原理将拱机制和桁架机制进行解耦，建立了的UHPC小剪跨区受力全过程的分析方法，并与试验结果进行对比验证。综合而言，本项目提出了UHPC梁抗弯和抗剪的设计理论和分析方法，进一步完善了UHPC结构设计理论，为相关技术标准编制和实桥工程应用提供了参考。