沥青混合料的拌和控制与配合比调试

从沥青混凝土拌合楼的主要组成和工作原理入手 ,结合AC 2 0Ⅰ沥青混凝土拌和的实践经验 ,提出了其拌和控制及配合比调试的具体技术措施     

沥青混合料生产配合比的控制与调试

介绍了沥青混合料拌合耧的工作原理 ,并对拌合耧的调试过程、冷料仓、热料仓等进行了叙述 ,在实际施工中确定生产配合比 ,加强拌合耧成品料的质量 ,提供了一些具体方法     

SBS改性沥青混合料配合比设计及施工技术

结合工程实例,对沥青混合料的配合比设计进行了阐述,并对其设计过程中的注意问题进行了说明,论述了SBS改性沥青的施工技术要求,供类似工程参考借鉴。     

静力及低周往复荷载作用下端板连接的力学性能研究

由于端板连接节点的多样性,不同构造形式端板连接节点力学性能存在一定差异.有限元分析方法可以通过变化多组几何参数建立大量模型来研究连接节点受力性能,是有效的研究方法之一.在已有试验模型基础上,衍生了一系列端板连接节点有限元模型,考虑材料非线性、几何非线性以及构件之间接触引起的状态非线性影响,对有限元模型进行静力和低周往复荷载计算.计算结果与试验进行了比较,验证了有限元模型的可靠性和有效性,并研究了构造形式对端板连接节点力学性能的影响.     

沥青稳定碎石ATB-30柔性基层的配合比设计

介绍了ATB-30结构特点,阐述了ATB-30沥青稳定碎石混合料的矿料组成设计、油石配比选择,并对目标配比进行了检验,达到了合理配比指导施工的目的,对类似工程有积极的借鉴意义。     

碳纤维布加固开门洞实心粘土砖墙的拟静力试验研究

通过碳纤维布加固的带门洞粘土砖墙在周期性反复荷载作用下的拟静力试验,对加固前、后墙体的破坏形态、变形性能、耗能能力和承载力作了全面的研究,探讨了碳纤维布加固带门洞粘土砖墙的受力和变形特性及粘贴碳纤维布加固开门洞砖墙的加固机理,证明碳纤维布用于带门洞粘土砖墙的抗震加固是有效的.     

Mechanical performances and stress states of rock bolts under varying loading conditions

A comprehensive study including laboratory tests and numerical modeling was performed to investigate factors of rock bolt fracture. Experimental tests were performed to evaluate the mechanical performances of bolt ends including the thread and adjacent. The effects of installation angle, pretension and accessories (plate, washer and nut) were evaluated. It is found that a bolt installed with an oblique angle to roadway surface suffers a complex stress combination of tensioning, bending and twisting on the bolt. This complex stress is much greater than the tensile stress, leading to cracking and growth at the location of bending causing the thread to fail even though the tensile stress is less than the yield strength. Bolt thread is more vulnerable to fracture than rebar.     

Structural recycled concrete: Behaviour under low loading rate

In this work the influence of the substitution of 100% of natural coarse aggregate with recycled coarse aggregate has been analysed in order to know the behaviour of the structural concrete in one particular aspect: that is, the behaviour of the recycled concretes under sustained load.To know the behaviour under sustained load, tests under very low loading rate were carried out, using concretes with 100% of recycled coarse aggregate. The results indicated that the ratio of strength under very low loading rate over strength under standard loading rate in compression and in tension is very similar in conventional and recycled concretes.     

冲击荷载作用下钢管混凝土梁的力学行为

通过对钢管混凝土的研究，介绍了用大型通用有限元计算软件ansys计算钢管混凝土梁在不同冲击荷载下的力学行为，取得在冲击荷载下的变形曲线，应力应变，加速度时程曲线，为进一步了解钢管混凝土提供了参考。     

再生陶瓷混凝土的力学性能与配合比设计

使用废弃陶瓷代替天然骨料配制再生混凝土技术,因具有明显的环境效益、经济效益和社会效益,正逐步受到人们的重视.详细分析了再生陶瓷混凝土力学特性之间的关系,特别是抗压强度、密度、劈拉强度、抗折强度和弹性模量之间的关系.结果表明,再生陶瓷混凝土力学性能之间的关系与普通混凝土不同,基于统计回归分析提出了一些改进公式来预测再生陶瓷混凝土力学特性之间的关系.研究表明,在进行再生混凝土配合比耐久性设计时,配合比设计列线图法是一种新型的实效的工具.     

Fatigue behaviour of a PET-Geogrid under cyclic loading

The lines of ‘damage-begin’ and ‘specimen-break’ for dynamic loading of a geogrid were determined in a series of laboratory testing. The cyclic load ratio was set to R = 0.5, loading frequency f = 10 Hz and f = 3 Hz. The test results show clearly that the chosen procedure for the determination and analysis of the beginning of damage and break is reproducible and allow for safe extrapolation for lower load levels. Furthermore the method chosen enables explicit decrease of the required testing time. The assumption of linear damage accumulation was examined in two-step-trials. The number of load cycles to ‘break’ evaluated in ‘one-step-tests’ compared with those of ‘two-step-loading’ are practically the same. The existence of ‘damage-lines’ for the examined geogrid under a dynamic pulsating load of 10 Hz and 3 Hz and a R-value of 0.5 could be verified. Damage of the specimens occurs only for load-cycles lying between the ‘damage-line’ and the ‘stress-cycle-diagram’ (‘Woehler-curve’). When it comes to dimensioning against ‘damage-beginning’ or ‘break’, higher loading frequencies present the critical case.     

钢管再生混凝土偏压柱受力性能及承载力计算

为了研究钢管再生混凝土偏压柱的受力性能,设计15个试件进行静力单调加载试验,考虑了再生粗骨料取代率、长细比和偏心距3个变化参数。观察试件的破坏形态,获取试件受力的全过程曲线,给出截面应变的分布情况,分析各变化参数对钢管再生混凝土偏压柱受力性能的影响,利用相关理论方法计算钢管再生混凝土偏压柱的极限承载能力。研究结果表明:钢管再生混凝土偏压柱与普通钢管混凝土偏压柱的受力过程及破坏形态相似,钢管最终表现为鼓曲破坏;钢管再生混凝土偏压柱具有较高的承载能力和良好的变形性能;偏心距、长细比对钢管再生混凝土偏压柱的受力性能影响显著,而再生粗骨料取代率对其影响不大。     

Failure behavior of highly stressed rocks under quasi-static and intensive unloading conditions

Unloading failure of rocks, especially highly stressed rocks, is one of the key issues in construction of underground structures. Based on this, analytical models for rocks under quasi-static and intensive unloading conditions are established to study the failure behavior of highly stressed rocks. In case of rock failure under quasi-static unloading, the rock mass ahead of working face is regarded as an elasto-brittle material, and the stress–displacement curves are used to characterize the tensile fracture of peak-stress area. It is observed that, when intensive unloading happens, there is an elastic unloading wave (perturbation wave) propagating in the rock mass. If the initial stress exceeds the critical stress, there will be a fracture wave, following the elastic unloading wave. To study the propagation feature of fracture wave, the conservation laws of mass, momentum and energy are employed. Results show that the post-peak deformation, strength and energy dissipation are essential to the failure process of highly stressed rocks.     

徐州地区混凝土配合比设计研究

本文主要论述了水泥强度检测采用ISO法后,研究混凝土配合比设计的必要性。通过大量的试验研究,测试混凝土及水泥的28天强度回归分析得到了混凝土配合比计算鲍罗米公式中徐州地区的回归系数。     

大直径钻孔群桩在横向荷载作用下的反应

应用三维有限元程序结合p-y曲线法研究大直径钻孔桩设计参数的确定方法，得出荷载-挠度的双曲线关系，为确定桩在横向作用下的极限承载力提供了一个方法。     

Experimental investigation of bitubal circular energy absorbers under quasi-static axial load

In this article, bitubal circular energy absorbers consist of two AL-6063-O tubes with unequal diameters placed coaxially and compressed under quasi-static axial load are studied experimentally. The effects of diameter and wall-thickness of each tube and the interaction between two tubes on the crashworthiness parameters are investigated in detail. In order to reduce the high value of peak load induced in the bitubal absorbers, two worthwhile solutions are proposed. The first one is to use two tubes with different lengths and the other one is to cut groove at the end portion of one of the tubes.     

Effects of loading rate on rock fracture

By means of a wedge loading applied to a short-rod rock fracture specimen tested with the MTS 810 or SHPB (split Hopkinson pressure bar), the fracture toughness of Fangshan gabbro and Fangshan marble was measured over a wide range of loading rates, =10⁻²–10⁶ MPa m^1/2 s⁻¹. In order to determine the dynamic fracture toughness of the rock as exactly as possible, the dynamic Moiré method and strain–gauge method were used in determining the critical time of dynamic fracture. The testing results indicated that the critical time was generally shorter than the transmitted wave peak time, and the differences between the two times had a weak increasing tendency with loading rates. The experimental results for rock fracture showed that the static fracture toughness K_Ic of the rock was nearly a constant, but the dynamic fracture toughness K_Id of the rock ( ≥10⁴ MPa m^1/2 s⁻¹) increased with the loading rate, i.e. log(K_Id)=a log +b. Macroobservations for fractured rock specimens indicated that, in the section (which was perpendicular to the fracture surface) of a specimen loaded by a dynamic load, there was clear crack branching or bifurcation, and the higher the loading rate was, the more branching cracks occurred. Furthermore, at very high loading rates ( ≥10⁶ MPa m^1/2 s⁻¹) the rock specimen was broken into several fragments rather than only two halves. However, for a statically fractured specimen there was hardly any crack branching. Finally, some applications of this investigation in engineering practice are discussed.     

十天高速AC-20沥青混合料配合比设计

对十天高速HL-M04标中面层AC-20沥青混合料在室内进行了原材料质量检验、配合比设计和路用性能检验,并通过目标配合比设计和生产配合比设计,指出其各项马歇尔体积指标和路用性能均能满足相关规范要求,为十天高速HL-M04标中面层的施工应用提供了技术基础。     

环境与荷载共同作用下混凝土内钢筋锈蚀特征分析

通过人工模拟不同腐蚀环境,研究了混凝土内部钢筋在环境-荷载共同作用下的锈蚀特征.运用体视显微镜、扫描电镜、电子探针微区分析等手段,研究了混凝土与锈蚀钢筋界面锈蚀层的细微观结构及元素分布特征.研究表明:混凝土与锈蚀钢筋界面存在明显过渡层.荷载-杂散电流-氯盐溶液腐蚀试件锈蚀层SEM形貌呈散粒状结构,而荷载-碳化腐蚀试件锈蚀层SEM形貌呈紧密排列的连续片状结构.过渡层被铁锈和水泥水化产物的混合物所充满,是锈蚀产物和水泥基体相互渗透的结果.     

Dynamic behavior of a Mediterranean natural stone under tensile loading

Historical buildings are important structures commonly occurring in Mediterranean cities. The behavior of their constituent materials under high dynamic loads is fundamental to investigate the vulnerability of such structures under extreme dynamic events. The main aim of our investigation was to study the effect of high dynamic loading conditions on a classical porous natural stone from the Naples area, namely yellow tuff, used in hundreds of historical buildings and monuments in Naples and other Mediterranean cities. Hence, dynamic characterization was performed through high strain-rate failure tensile tests. A wide range of strain-rates was investigated, from 10^?5 s^?1 to 50 s^?1. The obtained data were processed to obtain stress–strain relationships at different strain-rate levels. The results reveal that Neapolitan yellow tuff presents a significantly strain-rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain-rate, up to about three times that from quasi-static conditions in the case of very high strain-rates. Dynamic increase factors (DIFs) vs. strain-rate curves for tensile failure stress were also evaluated and discussed.