高性能半柔性路面在重载交通十字路口的应用

半柔性路面是一种向大空隙开级配沥青混合料中灌注特种灌浆材料的新型路面技术,半柔性路面材料兼具沥青路面的柔性和水泥混凝土路面的刚性,具有承载力强、抗车辙性能好、抗渗透性能好、无接缝、快速铺装等优越性能。以衢州市柯城区十字路口改建项目中半柔性路面的运用为工程依托,结合原有路段病害情况,探讨了半柔性路面的结构特点、施工工艺、技术性能及社会效益等方面内容。结果表明,半柔性路面技术可大幅提高路面的承载能力、抗车辙和抗渗能力,能够有效延长路面使用寿命,尤其适用于十字路口等病害频发区域,具有很好的应用前景。

Ultimate flexural strength of normal section of FRP-confined RC circular columns

Numerical analysis is carried out to study the sectional properties of the fiber-reinforced polymer（FRP）-confined reinforced concrete（RC）circular columns. The axial load ratio, the FRP confinement ratio and the longitudinal reinforcement characteristic value are the three main parameters that can influence the neutral axis depth when concrete compression strain reaches an ultimate value. The formula for computing the central angle θ, corresponding to the compression zone, is established according to the data regression of the numerical analysis results. The numerical analysis results demonstrate that the concrete stress enhancement from transverse confinement and strain hardening of the longitudinal reinforcement can cause a much greater flexural strength than that defined by the design code. Based on the analytical studies and the test results of 36 large scale columns, the formula to calculate the flexural strength when columns fail under seismic loading is proposed, and the calculated results agree well with the test results. Finally, parametric studies are conducted on a typical column with different axial load ratios, longitudinal reinforcement characteristic value and FRP confinement ratios. Analysis of the results shows that the calculated flexural strength can be increased by 50% compared to that of unconfined columns defined by the code.

Strength of circular concrete columns under concentric compression

An experimental study, in which six columns were loaded concentrically toinvestigate the behavior of reinforced normal strength and high strength circular columns underconcentric compression, is described. The concrete strengths of the columns were 30 MPa and 60 MPa.The primary variables considered were the concrete strength and the amount of transversereinforcement. Test results indicate that smaller hoop spacing provides higher column capacity andgreater strength enhancement in a confined concrete core of columns. For the same lateralconfinement, high strength concrete columns develop lower strength enhancement than normal strengthconcrete columns. Both the strength enhancement ratio (f'_(cc) /f'_(co)) and the column capacityratio (P_(test)/P_o) were observed to show linear increase variations with rho_s f_(yt)/f'_c incircular columns.

铁路桥墩新型延性构造及抗震设计方法研究

为解决延性抗震设计中铁路桥墩线刚度需求与承载力超强的矛盾,基于国内抗震相关规范,系统分析了问题的成因及影响,通过内缩截面降低承载力,增加外围材料提高刚度与强度的方法,提出了一种适用于铁路桥墩的塑性铰区新型延性构造;通过对墩柱性能曲线分段设计的方法,在抗震验算中引入基础承载力相关参数作为抗震设计控制条件,分别计算内缩截面后的核心墩柱与补强后墩柱的性能曲线,建立了基于该延性构造形式的抗震设计方法及完整的设计流程;以典型铁路桥墩为研究对象,验证了新型延性构造及抗震设计方法的有效性。采用新型延性构造的桥墩,在保证线刚度与容许应力强度需求的同时,显著的控制了墩柱承载力超强,降低了基础的建造成本。

Seismic ultimate bearing capacity of strip footings on slope

The influence of earthquake forces on ultimate bearing capacity of foundations on sloping ground was studied. A solution to seismic ultimate bearing capacity of strip footings on slope was obtained by utilizing pseudo-static analysis method and taking the effect of intermediate principal stress into consideration. Based on limit equilibrium theory, the formulae for computing static bearing capacity factors, Nq, Nc, Nγ, and dynamic bearing capacity factors, Nqd, Ned, Nγd, which are associated with surcharge, cohesion and self-weight of soils respectively, were presented. A great number of analysis calculations were carried out to obtain the relationship curves of the static and dynamic bearing capacity factors versus various calculation parameters. The curves can serve as the practical engineering design. The calculation results also show that when the values of horizontal and vertical seismic coefficients are 0.2, the dynamic bearing capacity factors Nqd, Ned and Nγd, in which the effects of intermediate principal stress are taken into consideration, increase by 4%-42%, 3%-27% and 34%-57%, respectively.

Ultimate end bearing capacity of rock-socketed pile based on generalized nonlinear unified strength criterion

In order to study the mechanism of bearing behavior at the tip of a pile embedded in rock, the generalized nonlinear unified strength criterion and slip line principle for resolving the differential equation systems which govern the stress field were applied to derive the ultimate end beating capacity based on some reasonable hypothesis and failure plane model. Both numerical simulation and test results were compared with the theoretic solution. The results show good consistency with each other and verify the validity of the present approach. The depth effect with respective to embedment ratio and other influence factors like geological strength index, intermediate principal stress, overburden factor, and damage on end bearing capacity were discussed in the analytical solution. The results show that the proposed yield criterion can be much better for investigating the ultimate end bearing performance of rock-socketed pile. The end bearing capacity increases with embedment ratio and the increasing degree is influenced intensely by the above parameters. Furthermore, ignoring intermediate stress effect would underestimate the strength properties of the rock material and lead to a very conservative estimation value.

Mechanical property of single-bolted composite laminates

In order to investigate the effects of different geometrical parameters and pretightening loads on failure mode and bearing strength,a large number of single-bolted T300/QY8911 composite laminates were tested under static tension load.Box-plot was used to extract the singular testing values of bearing strength and effective statistical values were obtained.T-test method of independent samples was used to study how much pretightening loads influence bearing strength.The results show that the geometrical parameters,such as ratios of width to hole diameter(w/d) and edge distance to hole diameter(e/d),remarkably influence failure mode and bearing strength.Net-section failure will occur when w/d is smaller than 4,and shear-out failure will occur when e/d is smaller than 2.Bearing failure or bearing and shear-out combined failure will occur when w/d is greater than 4 and e/d is greater than 2.There is an optimal combination of geometrical parameters to achieve the highest bearing strength.For most of specimens,pretightening loads do not explicitly influence bearing strength.

Low cyclic fatigue performance of concrete-filled steel tube columns

Eight concrete-filled steel tubular(CFT) columns were tested subjected to cyclic loading under constant axial load. Experimental parameters included axial compression ratio, loading sequences, and strength of concrete and steel. The seismic performance of CFT columns and failure modes were analyzed. The test results show that different axial load ratios and loading sequences have effects on the load carrying capacity, ductility and energy dissipation capacity of CFT columns, as well as the failure modes of the CFT columns. The failure pattern can be categorized into two types: local buckling failure of steel tube in compression zone, and low cycle fatigue tearing rupture failure of steel tube. The seismic behavior was evaluated through the energy index obtained from each cycle.

Experimental study on bearing capacity of shell strip footings near geotextile-reinforced earth slopes

From a financial point of view,urbanization frequently enforces the clients to construct superstructures near the slopes,giving rise to increasing the risk of building instability.By conducting a series of small-scale plate load tests,this work aims to investigate the effects of installing geotextile reinforcement layers in sandy slope and reducing the apex angle of triangular shell strip footings.The results show considerable effect of using geotextile-reinforced layers and decreasing the apex angle on the ultimate bearing capacity of shell foundations.With increasing foundation distance from the slope,the adverse effect of the slope is reduced.However,as the distance decreases,the effect of reinforcement and apex angle is increased.For practical applications,empirical equations are also presented for determining the ultimate bearing capacity of the footings and scale effect as well.Finally,3D numerical simulations are executed and compared with the experimental results.

A Hybrid Device for Anchoring FRP Sheets Aimed to Enhance the Flexural Capacity of RC Elements

The potential of externally applied FRP （fiber-reinforced plastic） sheets, being employed in retrofitting schemes aimed to repair and strengthen RC （reinforced concrete） structural elements damaged by prototype strong earthquakes, is presented and discussed in this study. The limitation of the debonding mode of failure of these FRP sheets is highlighted and the necessity to develop efficient anchoring devices for these FRP sheets is underlined. The behavior of such a novel HAD （hybrid anchoring device） capable of anchoring CFRP （carbon fiber reinforcing plastic） sheets to RC structural elements, is presented and discussed. The behavior of the device itself was studied through a 3D non-linear numerical simulation at the preliminary design stage in order to establish certain desired features such as the ductile behavior of the device itself as well as the satisfactory performance of the FRP sheets wrapped around this device. This HAD was next applied as part of a strengthening scheme aimed to upgrade the flexural capacity of an RC bridge-type pier specimen subjected to a cyclic seismic-type loading sequence. The obtained results demonstrated an increase in the specimen＇s flexural capacity by 100% as well as a similar increase in its capability of dissipating energy in a ductile manner during the cyclic load sequence. Moreover, the employed 3D non-linear numerical simulation yielded reasonably good agreement between the measured and the predicted cyclic response of this specimen strengthened by CFRP layers, which were anchored by the novel HAD. The successful behavior of this novel HAD, which has been patented with No. WO2011073696, is currently being tried with a number of other retrofitting schemes employing FRP sheets externally attached on RC structural elements.

15辆恒通客车进驻莱芜

本报讯莱芜市公交集团向重庆恒通客车有限公司订购的15辆新型公交车即将下线,并于近日奔赴莱芜。新订购的公交车为恒通新曼CKZ6116HN3,发动机均为国Ⅲ排放的纯天然气发动机。这是恒通客车首次进入莱芜地区,有望开创莱芜绿色公共交通新局面。