【作者】 陈浩；

【导师】 刘君平；

【作者基本信息】 福州大学 ， 桥梁与隧道工程， 2017， 硕士

【摘要】 超高性能混凝土(UHPC)具有超高强度、超高韧性和超高耐久性等特征,其受力性能明显优于普通混凝土,在桥梁工程中具有良好的应用前景。目前,传统混凝土桥面板存在自重较大、易开裂和耐久性差等缺点,若用UHPC取代普通混凝土来制作桥面板,可在较大程度上将板厚减薄,减少材料的消耗量,并极大地减轻结构自重。但是,桥面板减薄后是否会发生冲切破坏,这是UHPC桥面板在实际工程应用中需要解决的一个关键问题。同时,考虑到UHPC原材料价格较高,结合课题组研究成果,采用花岗岩石粉取代部分硅灰以降低成本,同时具有较大的环保意义。为此,本文开展了掺花岗岩石粉UHPC桥面板抗冲切性能及承载力计算方法研究。研究的主要内容与结论如下:(1)开展了 UHPC桥面板弯曲破坏与冲切破坏的临界厚度试验研究。以板厚为参数,进行了 5块掺花岗岩石粉UHPC与1块普通混凝土桥面板的弯曲与冲切破坏临界厚度试验研究,结果表明,6块试验板都发生了冲切破坏,且底板呈“锅底”形状,而顶板则冲切出一个明显的锥体。在达到极限荷载之前,随着板厚的提高,底板的挠曲变形随之变大。在板厚相同的情况下,对比普通混凝土板与UHPC板,由于钢纤维的阻裂、耗能和“桥接”等作用,UHPC试验板在破坏时的脆性得到明显改善。当UHPC桥面板厚度提高幅度为30%～100%时,极限承载力提高幅度为32.5%～65.8%,且试验板的变形、破坏范围等都逐步地增大。对比分析试验结果与理论分析结果,提出避免UHPC桥面板发生冲切破坏的临界厚度建议值为不小于100mm。(2)考察了 UHPC桥面板抗冲切受力性能的影响因素。以钢纤维体积掺量、配筋率、花岗岩石粉取代率为参数,进行了 6块等厚度的UHPC桥面板抗冲切受力性能的试验研究。结果表明,钢纤维从0%增加到3%,承载力则从250kN增大到355kN。配筋率从0%增加到3.50%,承载力则从180kN增大到355kN。10%掺量的花岗岩石粉对抗冲切承载力的影响较小,降低幅度仅为3.17%。(3)提出了 UHPC桥面板抗冲切承载力的计算方法。归纳对比了目前各种混凝土板抗冲切承载力的计算方法,结合本文试验结果,探讨了各计算值产生偏差的原因。最后,结合掺花岗岩石粉UHPC桥面板出现冲切破坏时的特征,提出了抗冲切承载力的简化计算方法。更多还原

【Abstract】 Ultra-high performance concrete(UHPC)has a good propect in bridge engineering not only because it has the characteristics such as ultra-high strength,high durability,and high toughness,but also because its mechanical performance is significantly better than the normal concrete.At present,the traditional concrete bridge deck have the disadvantages of large weight,easy cracking and poor durability.So if the normal concrete is replaced by UHPC to produce bridge deck,it will effectively reduce the thickness,save the materials and decrease the structural weight.However,there is a key issue urgent to be solved of UHPC in its application to the bridge deck.That is whether it will bring the problem of punching shear failure after thinning the bridge decks.At the same time,taking the high price of UHPC raw materials and the research results from our research group into account,the use of the granite stone powder to replace some part of the silica fume can not only reduce the costs,but also have a significant environmental effect.Therefore,the punching shear performance of UHPC bridge deck which mixed granite stone powder is researched in this paper.Based on the research of the critical thickness of the UHPC bridge deck at bending and punching shear failure,different parameters will be investigated to explore their influence on the punching shear performance of UHPC bridge deck.Finally,a calculation formula of ultimate bearing capacity will be put forward.The main contents and conclusions in this paper are as follows:(1)Researching the critical thickness between bending and punching shear failure.Regarding the deck thickness as the main parameter,we manufactured five tested decks of UHPC mixed with granite stone powder and one piece of normal concrete deck to research the critical deck thickness between bending and punching shear.The experimental results show that,all tested decks failed in punching shear,the bottom deck shapes like a "pot bottom",and the top deck punches out a clear cone.Before the slabs reach the ultimate bearing capacity,the bottom deck deflection deformations are increase with the thickness increasing.On the condition of the same thickness,the problem of brittle failure was improved when using the UHPC deck compared with the normal concrete because the UHPC deck is significantly better than the normal deck.Because its steel fiber has the function of crack resistance,energy dissipation and "bridging" effect.When the thickness of UHPC bridge deck was increased 30%～100%,the ultimate bearing capacity increased 32.5%～65.8%,besides the deformation and damage range of the tested plate were gradually increased According to the experimental results and the theoretical analysis,it should be recommended that the critical thickness of UHPC bridge deck mixed with granite stone powder be no less than 100mm in order to avoid punching failure.(2)Investigated the punching shear performance of UHPC bridge deck in different influence factors.Six equal thickness of UHPC bridge decks were fabricated to study the punching shear performance based on the parameters of the volume fraction of steel fiber,the reinforcement ratio and the replacement rate of granite stone powder.The results show that the ultimate bearing capacity increased from 250kN to 355kN when the volume fraction of steel fiber changed from 0%to 3%.When the reinforcement ratio increased from 0%to 3.50%,the ultimate bearing capacity increased from 180kN to 355kN.The granite stone powder mixed with 10%silica fume has little influence to the punching shear ultimate bearing capacity and the reduction scope was only 3.17%.(3)Put forward the calculation method of UHPC bridge deck punching shear bearing capacity.After summarizing and comparing the calculation methods of punching shear ultimate bearing capacity,the reasons of deviation under each calculation resultsare discussed based on the experimental results.Finally,according to the punching shear stress mechanism of UHPC bridge deck mixed with granite stone powder,a simplified punching shear ultimate bearing capacity formula is put forward.更多还原