【作者】 李亮；

【导师】 王景全； 戚家南；

【作者基本信息】 东南大学 ， 桥梁与隧道工程， 2021， 硕士

【摘要】 超高性能混凝土(Ultra high performance concrete,UHPC)具有超高强、高韧、高耐久等优异性能,近年来在桥梁工程领域得到了广泛的应用。值得注意,因UHPC材料成本高,全截面使用UHPC代替传统普通混凝土(Normal concrete,NC)不但大幅增加工程造价,而且顶板处的UHPC的抗压性能不能完全发挥。为充分发挥UHPC材料优异力学性能,降低工程造价,保证UHPC桥梁建造质量,提升UHPC桥梁施工速度,装配式无腹筋UHPC-NC组合梁结构形式逐渐获得了应用,该组合梁的预制无腹筋UHPC梁和预制普通混凝土桥面板通过剪力槽口连接。由于取消腹筋设置,钢纤维对于组合梁的斜截面受剪性能的影响和贡献不容忽视。同时,装配式UHPC-NC组合能否良好地协同工作在很大程度上取决于组合梁界面的力学行为。因此,本文针对无腹筋UHPC梁斜截面受剪性能以及装配式UHPC-NC组合梁界面纵向受剪性能开展研究,主要的研究内容与结论如下:(1)无腹筋UHPC梁受剪数据库建立与承载力计算方法对比研究广泛搜集国内外无腹筋UHPC梁受剪试验数据,建立了总数为247片无腹筋UHPC梁的受剪数据库。针对受剪数据库进行样本整体研究,分析以往试验研究重点及参数分布情况。基于抗剪数据库研究了无腹筋UHPC梁受剪承载力随各主要影响因素的变化规律,并对法国UHPC规范(NF P 18-710)、日本UHPC指南(JSCE-2006)、欧洲规范(Model Code-2010)、中国规范(DBJ 43/T 325-2017)和瑞士UHPC指南(SIA 2052)中的混凝土梁受剪承载力计算公式进行评估和分析。结果表明,各规范公式均不同程度地保守估计了无腹筋UHPC梁的受剪承载力;法国UHPC规范NF P18-710预测结果误差最小;各规范未充分体现剪跨比、钢纤维含量特征值等因素对无腹筋UHPC梁受剪承载力的影响。(2)基于纤维-箍筋等代原理的无腹筋UHPC梁受剪承载力计算方法通过分析无腹筋UHPC梁斜截面抗剪机理,结合现有学者研究结论,依据最小配箍用量原则,量化了纤维-箍筋等代作用,提出了无腹筋UHPC梁所需纤维掺量。基于法国UHPC规范受剪承载力计算公式,考虑钢纤维特性、纤维-基体界面强度和剪跨比等参数影响,提出无腹筋UHPC梁受剪承载力钢纤维影响系数和剪跨比影响系数;通过搜集的无腹筋UHPC梁受剪数据库试验结果,以85%安全保证率为基准,得到钢纤维影响系数和剪跨比影响系数的表达式,建立了无腹筋UHPC梁受剪承载力计算公式。将该公式计算结果与数据库试验结果对比,表明提出公式可较好地预测无腹筋UHPC梁的受剪承载力。(3)装配式UHPC-NC组合梁界面纵向受剪性能与计算方法研究对采用UHPC剪力槽连接的装配式UHPC-NC组合推出试件进行非线性有限元分析,研究了抗剪钢筋直径、钢筋间距、钢筋数量等参数对界面受剪承载力的影响。分析结果表明,装配式UHPC-NC组合梁界面受剪承载力随着抗剪钢筋直径、钢筋数量的增加而增大,抗剪钢筋间距对于组合界面受剪承载力影响很小。根据推出试件发生钢筋剪断的破坏模式,考虑UHPC强度以及钢筋在UHPC中销栓作用的影响,发展了采用UHPC剪力槽的装配式UHPC-NC组合梁界面受剪计算公式,通过比较该公式计算结果与试验结果表明其能够较好预测装配式UHPC组合梁界面受剪承载力。更多还原

【Abstract】 Because of the excellent properties of Ultra-high performance concrete(UHPC),such as ultra-high strength,high toughness,and high durability,it has been widely used in bridge engineering in recent years.Note that replacing all the normal strength concrete(NC)components using UHPC components is uneconomical in bridge engineering due to the high cost of UHPC materials.In addition,it is also found that the compression performance of UHPC can not be fully developed in the UHPC bridge.To give full play to the excellent mechanical properties of UHPC material,reduce the project cost,ensure the construction quality of the UHPC bridge,and improve the construction speed of the UHPC bridge,the precast UHPC-NC composite beam without web reinforcement was proposed.The precast UHPC beam is connected to the NC deck using the shear pocket,which was filled using UHPC.Due to the elimination of the web reinforcement,the influence and contribution of steel fiber on the shear performance of the composite beam can not be ignored.At the same time,whether the assembled UHPC-NC combination can work well depends on the shear behavior of the interface between the UHPC beam and the NC deck.Therefore,the vertical shear behavior of the inclined section of UHPC beams without web reinforcement and the longitudinal shear behavior of the interface of assembled UHPC-NC composite beams are studied.The research contents and conclusions were as follows:(1)Comparative study on shear test database establishment and capacity calculation method of UHPC beam without web reinforcementThrough collecting the shearing failure tests of UHPC beams without web reinforcement,a total of 247 test database is established.Based on the test database,the influencing factors,such as the shear span ratio,and the volume fraction of steel fiber,which have a significant influence on the shear performance of UHPC beam,were investigated.The test results were compared with the calculation results,which was obtained using the shear strength formula of French UHPC code(NF P 18-710),Japanese UHPC Guide(JSCE-2006),European Code(Model code-2010),Chinese code(DBJ 43/T 325-2017),and Swiss UHPC Guide(SIA 2052).The calculation results show that the shear capacity of reinforced UHPC beams is estimated conservatively in different codes;The prediction deviation of the formula in NF P18-710 is the smallest and the safety reserve is reasonable.However,it is found from this formula in these design codes that the influence of shear span ratio and characteristic value of steel fiber content on the shear capacity of UHPC beams without web reinforcement is not fully reflected in these codes.(2)Shear bearing capacity calculation method of UHPC beams without web reinforcement based on fiber-stirrup equivalent actionBy analyzing the shear mechanism of non-web reinforced UHPC beams and combining it with the existing research conclusions,the concept of fiber-stirrup equivalent action is proposed.Based on the shear performance of the steel fiber,the minimum fiber volume fraction of nonweb reinforced UHPC beams is determined according to the principle of minimum stirrup amount.Then,based on the shear capacity calculation formula of NF P 18-710,the shear capacity calculation formula of UHPC beams without web reinforcement is obtained by modifying the test results of the shearing test database of UHPC beams without web reinforcement,which takes into account the influence of steel fiber characteristics,fiber-matrix interface strength,and shear span ratio.The comparison between the calculation results of the formula and the test results of the database shows that the formula can better predict the shear capacity of UHPC beams without web reinforcement..(3)Study on shear behavior and calculation method of the longitudinal interface of the precast UHPC-NC composite beamsThe nonlinear finite element analysis was carried out to investigate the shear performance of the push-out specimens,and the influence of design parameters,such as the diameter of shear reinforcement,the spacing of reinforcement,and the number of reinforcement on the shear performance of the interface is studied.The results show that the shear capacity of the interface increases with the increase of the diameter of shear reinforcement and the number of reinforcement,while the spacing of shear reinforcement has little effect on the shear capacity of the composite interface.Then,according to the failure mode of the push-out specimen that only the steel bar is sheared,and considering the tensile and compressive strength of UHPC and the influence of the dowel action of steel bar in UHPC,the formula is developed to predict the shear strength of the UHPC-NC interface,which was connected using the UHPC shear pocket.By comparing the calculated results with the experimental results,it shows that the formula can predict the interfacial shear capacity of precast UHPC composite beams更多还原