半刚性基层沥青路面连续施工工艺

沥青路面是我国高等级公路的常见路面结构类型之一,施工效果良好。但在实践应用中仍存在诸多问题,如路面裂缝等。为有效阻止沥青路面裂缝产生,该文以2段施工段进行对比分析,经施工检测可见,掺抗裂缝剂半刚性基层沥青路面连续施工工艺路段压实度在高于98%,抗剪强度为0.81 MPa,拉拔强度为0.06 MPa,上述各值均高于传统施工工艺路段,由此可见,该施工法可有效提升施工效率,施工效果良好,具有可行性。     

半刚性基层沥青路面病害分析与预防

根据半刚性基层沥青路面的典型病害特征及产生原因,针对病害路面提出了预防对策。     

半刚性基层沥青路面反射裂缝的研究现状

主要从反射裂缝的产生机理和防治措施两个方面简要论述反射裂缝的研究现状和防治措施,并且提出进一步的研究方向。     

浅析高级公路半刚性基层沥青路面的养护

通过高等级公路半刚性基层沥青路面的典型病害特征的分析,提出了路面养护维修的主要对策。     

半刚性基层沥青路面的病害分析与维护措施

本文根据半刚性基层沥青路面的典型病害特征及产生原因的分析，提出了路面养护维修的主要对策。     

半刚性基层沥青路面裂缝危害及防治

随着市场经济的迅速发展,我国公路网功能日益完善。当前,我国已建公路90%以上选用半刚性基层沥青路面,但这种"强基薄面"的路面类型,已不适应重载交通的发展。按照现行公路设计标准,多数公路均需在建成通车3-5年进行大中修。其中,最常见的病害为裂缝,此类病害的长期发展,将严重降低路面使用性能,影响行车舒适性与安全。为此,该文在全面了解半刚性基层沥青路面裂缝危害的基础上,结合某具体工程案例,对沥青路面裂缝处治方案、防治措施进行了分析与探讨。     

沥青路面柔性基层与半刚性基层的优化组合研究

半刚性基层具有许多优点的同时,存在排水不良、反射裂缝等不足;而柔性基层则反之。通过改革柔性基层传统的材料与工艺,实现柔性与半刚性基层的优化组合。从重交通对沥青路面使用性能相互矛盾的要求,通过提高柔性基层质量,提高柔性基层的模量,以减少沥青路面的疲劳裂缝,实现柔性基层与半刚性基层的优化组合。     

半刚性基层沥青路面的车辙形成机理及防治措施

本文通过对车辙类型的分析，阐述了半刚性基层沥青路面车辙的形成机理，在分析的基础上，总结了车辙的影响因素，并针对不同类型的车辙提出了相应的预防和处理措施。实际工程证明，这些预防和处理措旋可以很好的预防车辙产生，较好的提高沥青路面的服务功能和使用寿命。     

半刚性基层沥青路面裂缝成因与处治对策

沥青路面开裂的原因和裂缝的形式是多种多样的。本文分析了半刚性基层沥青路面裂缝的成因，针对裂缝的不同成因，提出相应的处治对策。     

半刚性基层沥青路面反射裂缝扩展过程分析的Williams单元

该文对半刚性基层沥青路面结构采用弹性层状体系平面应变分析模型,利用改进的Williams级数,结合广义参数有限元法和常规等参元,建立了反射裂缝裂尖应力强度因子分析的广义参数Williams单元,并推导了Williams单元的刚度方程,据此研究了正对称荷载和偏载分别作用时,反射裂缝扩展过程中应力强度因子的变化规律;重点分析了偏载作用下路面结构层参数与应力强度因子之间的关系。Williams单元中含有与应力强度因子相关的参数,可以直接获得裂尖应力强度因子。算例分析表明：Williams单元与传统方法的计算结果吻合较好,且格式简单,计算精度高,适用于沥青路面反射裂缝扩展过程分析。     

Dynamic model and criteria indices of semi-rigid base asphalt pavement

This paper presents a dynamic model of asphalt pavement by considering the characteristics of moving tyre load, visco-elastic performance of material and layered system of pavement. The pavement is defined as an infinite layered system with the tyre load moving at a constant speed, and asphalt concrete (AC) is characterised as a kind of visco-elastic material. Using the spectrum analysis method, a complex tyre load is decomposed into a series of harmonic loads. Based on the frequency characteristics of a linear system, a universal formulation pattern for differential visco-elastic constitutive relations is provided. And then, a model is set up to analyse the dynamic response of asphalt pavement under moving harmonic load, and then to extend to the arbitrary moving load according to the superposition principle of a linear system. The dynamic responses of seven typical semi-rigid base asphalt pavements are analysed using the model. Analysis results indicate that the tensional strain at the bottom of the AC layer and the vertical compression strain at the top of the roadbed are not suitable for key indices of the semi-rigid base asphalt pavement. The shearing strain at the bottom of the AC layer can be taken as a key index to evaluate the fatigue performance, and the vertical compression strain at the top of the pavement surface can be taken as a key index to evaluate pavement rutting, and the vertical shearing strain at the top of pavement surface can be taken as a key index to evaluate top–down crack.     

基于压电智能骨料的沥青混凝土路面车辆动态荷载监测

本文提出了一种基于压电智能骨料（Smart aggregate, SA）的沥青混凝土（Asphalt concrete, AC）路面车辆荷载监测方法。首先,考虑不同车速进行了埋入SA的AC块体动态加载试验研究,采用电液伺服试验机进行动态荷载加载,给出了SA在给定边界条件下的灵敏度,并分析了加载速率对其影响;其次,建立了嵌入SA的AC块体的有限元模型,模拟了试验中实际加载边界条件,分析了AC中的应力分布,进而得出了SA的灵敏度,并与试验结果进行了对比。最后,通过有限元模拟,研究了AC弹模变化对SA灵敏度的影响。研究表明,对于埋入SA的AC路面,车辆动态荷载下SA灵敏度为线性,常温下AC弹模变化对SA灵敏度影响可忽略不计。本文提出的基于SA的AC路面车辆荷载监测方法是可行的。     

Ultimate load behaviour of reinforced concrete plates and shells under dynamic transient loading

This paper considers a layered thick shell finite element procedure for determining the dynamic transient nonlinear response of plates and shells. The degenerated three-dimensional isoparametric shell element with independent rotational and translational degrees-of-freedom is employed and a layered formulation is adopted to represent the steel reinforcement and to simulate progressive concrete cracking through the thickness. The dynamic yielding function is assumed to be a function of the current strain rate, in addition to being total plastic strain or work dependent. The concrete model also simulates both compressive crushing and tensile cracking behaviours and an implicit Newmark algorithm is employed for time integration of the equations of motion. Several numerical examples are presented for both slab and shell structures and the results obtained compared with those from other sources wherever available.     

Dynamic response of top-down cracked asphalt concrete pavement under a half-sinusoidal impact load

A 3D finite element analysis model of cracked asphalt pavement is established by the FEM software ABAQUS. Based on dynamics mechanics, fracture mechanics and finite element theory, this paper studies the influence of various vehicle speeds, crack location, crack depth, damping ratio etc. on the dynamic response. The results show that the surface deflection, the maximum tensile strain at the bottom of the asphalt layer, and the maximum shear stress of the asphalt layer decreased with the increase in vehicle velocity when there is no crack in the pavement. No matter where the transverse position of the crack is the stress intensity factors increase with the increase in crack depth and decrease exponentially with the increase in longitudinal distance between the vehicle center and the crack. In the case of the crack locating in the center of wheel clearance, the surface deflection increases with the crack depth increasing. But if the crack is at the edge of the wheel track, there will be a critical vehicle velocity where the surface deflection is smaller than the asphalt pavement without crack if the vehicle velocity is above it. The maximum tensile strain at the bottom of the asphalt layer and the maximum shear stress of the asphalt layer are also smaller than the asphalt pavement without crack. The maximum tensile strain and the maximum shear stress decrease with the damping ratio increasing. So the increase in damping ratio can help to alleviate the propagation of cracks.     

An examination of compaction meter value for asphalt pavement compaction evaluation

Abstract

The potential of using compaction meter value (CMV) for evaluating the compaction of asphalt pavements has been hindered by the fact that the value of CMV can be affected by many factors, which include not only roller operation parameters, but also the temperature of asphalt layer and the underlying support. However, the conventional data processing of CMV usually ignores these factors. The study proposed a new approach to thoroughly examine the relationships between CMV and other factors. Using a field project in Tennessee, USA, the intelligent compaction data were examined to establish the relationships between CMV and other operation parameters such as roller frequency and amplitude first, then the effects of asphalt temperature and underlying support were analysed further utilising the original Witczak model and Abaqus software. After eliminating the influence of other factors, the proposed method could improve the correlation between the asphalt mixture density and CMV.     

Strengthening of reinforced concrete beams in flexure by partial jacketing

This work investigates the structural behaviour of reinforced concrete beams strengthened in bending by the addition of concrete and steel on their tension sides using expansion bolts as shear connectors, technique here denominated partial jacketing. The experimental program comprised tests on eight full-scale reinforced concrete beams, simply supported, with rectangular cross section (150 mm × 400 mm) and 4,500 mm length. Five of these beams were strengthened in bending by partial jacketing, while the other three did not receive any strengthening and served as reference beams. The flexural reinforcement ratio in the beams varied between 0.49% and 2.33% and the beams target concrete strength was 35 MPa. On the basis of the obtained test results, the studied strengthening technique proven to be efficient in terms of increasing the resistance and stiffness of the beams. The used expansion bolts as shear connectors proven to be practical and added ease to the application of this technique.     

Fatigue strength of steel fibre reinforced concrete in flexure

The paper presents a study on the fatigue strength of steel fibre reinforced concrete (SFRC). An experimental programme was conducted to obtain the fatigue-lives of SFRC at various stress levels and stress ratios. Sixty seven SFRC beam specimens of size 500×100×100 mm were tested under four-point flexural fatigue loading. Fifty four static flexural tests were also conducted to determine the static flexural strength of SFRC prior to fatigue testing. The specimens incorporated 1.5% volume fraction of corrugated steel fibres of size 0.6×2.0×30 mm. Concept of equivalent fatigue-life, reported for plain concrete in literature, is applied to SFRC to incorporate the effects of stress level S, stress ratio R and survival probability L_R into the fatigue equation. The results indicate that the statistical distribution of equivalent fatigue-life of SFRC is in agreement with the two-parameter Weibull distribution. The coefficients of the fatigue equation have been determined corresponding to different survival probabilities so as to predict the flexural fatigue strength of SFRC for the desired level of survival probability.     

沥青路面导热系数测试及其对路面温度场影响的模拟

沥青路面温度场是沥青路面车辙计算和沥青混合料粘弹性分析的重要参数,路面温度场的精确预估涉及到面层各层材料热物理参数的精确测试,因此沥青混合料热物理参数的准确测试变得越来越重要.基于对测试结果重现性和可比性的考虑,采用瞬态热线法进行沥青混合料导热系数的测试,选取几种有代表性的混合料进行了导热系数测试,分析了影响导热系数的因素.基于ABAQUS模拟计算路面温度场分布,通过改变路面上、中、下面层的导热系数,计算路面温度场分布变化的情形,对计算结果的分析发现,上面层导热系数对面层温度场分布的影响更显著,可以预期通过改变上面层导热系数能达到主动改善沥青路面工作温度的目的.