T字型三维机织物设计及其复合材料弯曲性能

为探究不同梁高的T 字型三维整体机织复合材料的弯曲力学性质,经合理设计,使用玄武岩长丝束在普通小样织机上,低成本织造3 种不同梁高的T 字型三维整体机织物,采用真空辅助树脂传递模塑成型工艺,制备Ｔ 字型三维整体机织复合材料。用电子万能试验机测试,得到相应的载荷位移曲线和吸收能量位移曲线。由实验结果可知,梁越高的T 型三维整体机织复合材料所承受的载荷和吸收的能量也越高,且不同梁高的T 型三维整体机织复合材料也表现出不同的弯曲破坏模式。该研究结果表明,梁高对T 字型三维整体机织复合材料的弯曲载荷、吸能和破坏模式影响显著。     

Corner crack mechanism of boron-containing LCAK steel slabs

At Baoshan Iron Steel Co., Ltd., corner cracks of boron containing LCAK steel slabs had caused remarkable quality loss and mass flow disorder. With the help of fractography and thermodynamics analysis,the embrittlement mechanism of this steel grade was studied and the results are as follows: ① The transformation from γ to α starts at the austenite grain boundaries and a layer of thin ferrite film gradually forms around the austenite grains. Strain concentration will preferentially start inside the ferrite phase when the stress accumulates to a certain level.② The coarse BN particles acceleratedly precipitated at the γ/α interfaces further deteriorate the ductility of the ferrite film,and brittleness results in strain concentration and microvoid coalescence inside the ferrite film.Therefore the austenite grain boundaries are prone to intergranular failure.③ The stoichiometry among Al,N and B is a very important factor influencing the hot ductility of this steel grade.By controling the B-to-N atomic ratio to above 1,all N can be fixed by B instead of Al.Thus coarse-grained steel is available and fewer grain boundaries and higher ductility can reduce the risk of corner cracks.④ By adjusting the B-to-N atomic ratio,Baoshan Iron Steel Co. ,Ltd.successfully reduced the number of cracks to nearly one tenth of that in the past and the hot tensile tests confirmed remarkable improvement in the hot ductility of this steel.     

石庙特大桥T型刚构0号梁段施工

基于0号梁段在T型刚构施工中的重要作用,介绍了石庙特大桥T型刚构中0号梁段的施工工艺和施工方法,并总结了施工过程中的几点体会,对同类型桥梁施工具有指导意义。     

两层预制板砖砌体结构房屋模型双向拟动力试验研究

对一栋缩尺为1∶2的两层单开间预制板砖砌体结构房屋模型进行不同强度地震作用下的双向拟动力试验和非线性地震响应分析,研究该结构在地震作用下的破坏机制、变形、滞回特性及耗能能力等。结果表明：构造柱与圈梁的存在,使得预制板砌体结构具有较好的延性,地震破坏主要集中在底层,即使墙体严重开裂,也不至于整体结构垮塌;双向地震作用下一个方向的承载力与刚度退化会加剧另一个方向承载力与刚度的退化,从而导致砌体结构整体抗震能力的下降;滞回曲线由弓形最后发展到反S形,具有明显的捏缩和滑移效应;建立的砌体结构非线性空间有限元模型,能够反映预制板砌体结构的弹塑性地震响应,计算结果与实测结果基本吻合;两层砌体结构房屋能够满足设计规范的抗震要求。     

蜂窝状钢骨混凝土T形柱抗震性能有限元分析

利用大型有限元软件ANSYS对蜂窝状钢骨混凝土T形柱在低周反复荷载作用下的抗震性能进行分析,并考虑不同轴压力系数、剪跨比、体积配箍率、钢骨开洞率等参数对蜂窝状钢骨混凝土T形柱的影响。分析结果表明:轴压力系数和剪跨比对试件的延性有很大影响;而体积配箍率对于提高柱子的延性和承载力有一定贡献,但不显著;适当的钢骨腹板开洞率可以提高试件的延性和承载能力。     

高速铁路CRTS Ⅰ型轨道板快速封锚技术研究

针对高速铁路CRTS I型轨道板传统封锚工艺效率低、工序繁琐、质量差、易脱落等问题,提出了一种全新的快速封锚施工技术.该工艺具有封锚材料生产工厂化和封锚施工操作标准化的特点,采用半机械化施工,可将轨道板封锚施工时间缩短为传统工艺的1/6,且能确保封锚质量,满足轨道板快速生产工艺要求.工程应用情况表明,该技术能大幅提高轨道板封锚施工效率,缩短轨道板生产周期,保证轨道板封锚施工的标准化.     

钢筋混凝土T形截面连续梁穿翼栓锚绕杆自锁U形碳纤维布抗剪加固试验研究

U形纤维布外贴加固混凝土梁易因纤维剥离导致脆性剪切破坏,为此,针对T形截面梁提出了布端绕双杆自锁且用螺栓穿翼锚固的方案,并开展了连续梁负弯矩段受剪加固模型试验。结果表明：加固梁受剪承载力平均提高46.6%,最高达到了61.1%,有效防止了剥离破坏的发生,延性亦有不同程度的改善。绕杆自锁形成的可靠端部锚固使得纤维应变曲线具有“S”形上升的典型特征。既有规范基于常规矩形截面梁封闭粘贴加固试验建立的承载力计算公式对于绕杆锚固开口向上的U形纤维布受剪加固负弯矩T形梁段的适用程度不一,其中英国规范TR55和中国规范GB 50608—2010能够较好地预测主要参数对承载力影响的走势,澳洲规范HB305计算结果平均值与试验值最为接近。     

T型地下综合管廊电缆火灾数值模拟

针对特殊结构的T 型地下综合管廊,运用FDS 软件模拟不同火源位置及风速条件下管廊内电缆火灾的蔓延情况,分析火灾发生后管廊温度场以及烟气蔓延情况。对T 型管廊内不同位置处起火的火灾危险性进行排序,得到管廊内部风速为1.5m/s 且电缆处于稳定燃烧期时,交叉口处的烟气层高度最低,发现T 型交叉口处的烟气特性,为T 型地下综合管廊消防设计提供参考。     

整体预制钢-混凝土组合梁桥合理结构研究

为了在中小跨径桥梁中推广使用钢-混凝土组合结构桥梁,提高桥梁的工业化建造水平和组合梁桥的装配化程度,提出了一种整体预制钢-混凝土组合梁桥结构。结合常用的中小跨径的需求,考虑公路运输条件和吊装能力,构建了整体预制钢-混组合梁结构基本单元,并提出了单元之间的连接方式,进一步形成整体桥梁。计算分析表明:所提出的整体预制钢-混组合梁,在受力性能方面均优于传统分离预制钢-混组合梁,在全寿命周期的经济性能方面优于现有的预制混凝土箱梁、预制混凝土T形梁,在施工性能方面相比于现有的预制混凝土箱梁、预制混凝土T形梁以及分离预制钢-混组合梁会明显提高施工效率、缩短施工工期,而且更容易保证施工质量,为桥梁工程提供了一种结构合理、施工便捷的结构形式。     

Blast Testing of Aluminum Foam–Protected Reinforced Concrete Slabs

Aluminum foam is a newly developed mobile and lightweight material with excellent energy absorption capacities. Applying aluminum foam as a sacrificial protection layer on the bearing faces of protected structures can mitigate blast effects on the resistance capacities of structures against impact or blast loading. The aluminum foam undergoes great plastic deformation under transient dynamic loads before becoming fully densified, making it excellent for mitigating blast effects on these structures. In this paper, we conducted quasi-static testing on two types of aluminum foam specimens and obtained the primary parameters for the mechanical properties of aluminum foam specimens. We then used these two types of aluminum foams to protect the reinforced concrete (RC) slabs, and we conducted a series of tests to investigate the performance of the aluminum foam–protected RC slabs against blast loads. We tested a total of five foam-protected slabs and one control RC slab in the blast test program. The test results, including displacement and acceleration histories, performance of specimens, and maximum and permanent deflections, were fully reported. We then discussed the efficiency of aluminum foam to mitigate blast loads on protected RC slabs.