浅谈预应力混凝土路面设计

论述了预应力混凝土路面在我国的应用,分析了预应力混凝土路面的优缺点,探讨了预应力混凝土路面设计考虑的因素,详细介绍了预应力混凝土路面的设计,以推广预应力混凝土路面的应用.     

预应力技术在道路工程中的应用

从使用性能上阐述了预应力混凝土路面的优势及存在的不足,借鉴世界各国对预应力混凝土路面设计的研究和经验,提出了预应力混凝土路面的设计方法和步骤,最后对预应力混凝土路面的施工方法和质量控制等有关问题进行了分析和探讨。该研究对预应力混凝土路面的设计与施工具有一定的参考价值。     

斜向预应力无缝水泥混凝土路面研究

针对传统水泥混凝土路面的不足和缺点,提出了斜向预应力无缝水泥混凝土路面这一新概念,并对其施工关键技术进行了研究,通过与其他路面对比分析,指出斜向无缝水泥混凝土路面理论上减少了纵向和横向开裂的可能性,可减少后期养护。     

有效预应力对无粘结预应力梁受力性能的影响

利用有限元方法,研究了有效预应力对无粘结预应力混凝土梁受力性能和无粘结预应力筋极限应力增量的影响.设计了以有效预应力值为变量的分别承受跨中单点集中荷载以及均布荷载作用的无粘结预应力混凝土梁,利用建立的有限元模型对这些梁进行非线性全过程分析.结果表明,随着有效预应力的提高梁的开裂荷载和开裂弯矩显著提高,若梁破坏时无粘结预应力筋仍处于弹性阶段,则梁的极限荷载和极限弯矩亦显著提高,而无粘结预应力筋极限应力增量逐渐降低.     

预应力混凝土路面浅析

我国目前许多省份的普通混凝土路面都存在严重的裂缝和断板现象,严重影响公路的运行状况,解决普通混凝土路面病害的方法之一是采用预应力混凝土路面,预应力混凝土路面减少养护费用,提高路面的使用性能,社会经济效益十分显著,预应力混凝土路面将会有良好的发展前景。     

预应力框架施工阶段的裂缝问题

近年来,预应力混凝土框架因其显著的优点得到越来越广泛的应用。但是,由于设计及施工处理不当在施工阶段出现裂缝的情况时有发生,引起混凝土结构开裂的因素很多,要准确地判断引起开裂的原因十分困难。本文从预应力设计、施工及材料(混凝土)等几个方面分析引起施工阶段裂缝的原因,供从事预应力设计和施工的技术人员参考。     

体外预应力钢-混凝土组合梁

在钢-混凝土组合梁中采用体外预应力技术,具有提高组合梁的刚度以及承载能力,减小混凝土的收缩徐变开裂,提高结构的耐久性等优点。近年来,国内已相继建造了采用体外预应力组合梁的城市桥梁和结构,但在体外预应力钢-混凝土组合梁的受力性能、施工和使用阶段的受荷机理以及设计和应用方面仍存在许多有待解决的问题。回顾了国内外体外预应力组合梁研究及应用进展,对一些关键技术进行了论述,可供研究及设计人员参考。     

混合配筋新型预应力混凝土管桩抗弯性能研究

提出了在预应力混凝土管桩中加入一定数量的非预应力钢筋的新型混合配筋预应力混凝土管桩的概念,以提高预应力管桩的抗弯承载力和延性.通过5根配有非预应力钢筋的混合配筋新型预应力混凝土管桩原型和2根普通预应力混凝土对比管桩的标准抗弯试验,研究了配置非预应力钢筋后的新型管桩的极限弯矩和刚度.基于混凝土规范和试验结果,建议了新型管桩抗弯承载力设计计算理论公式和用于管桩出厂检验的桩身极限弯矩检验值理论计算公式,均和试验结果符合良好,且满足管桩设计要求.提出了新型管桩开裂前和开裂后抗弯刚度的计算公式,和试验结果吻合良好.     

道路桥梁施工过程中预应力技术存在问题及应对措施

在设计道路桥梁结构预应力中应充分考虑混凝土强度变化问题,因为预应力的存在,在道路和桥梁结构的设计中应该考虑预应力混凝土强度变化问题,由于预应力结构载荷的存在产生拉应力时,首先是消除预应力,然后满足增加,预应力的存在可以延迟开裂的结构,以提高结构的抗裂度和刚度。合理的预应力是一种新的思想和方法,在道路和桥梁的建设具有非常重要的意义。     

论预应力混凝土路面在路桥施工中的技术

1预应力混凝土路面的优缺点许多研究工作表明预应力混凝土路面有以下几方面的优点:路面板厚度只需传统混凝土路面板厚的40%￣60%,就能提供很高的承载力和较高的抗变形能力,对减薄机场道面的厚度非常有利;预应力混凝土路面由于板较长,接缝数量可大大减少。改善了行车的平稳性;预应力的存在使路面板体性较强,     

Effects of overlay designs on reliability of flexible pavements

Management of flexible pavements requires timely application of preventive maintenance and rehabilitation actions such as overlays. These actions are an integral part of a design strategy that minimises the use of recourses over the pavement's life-cycle. The objective of this paper is to develop a reliability model for flexible pavements that accounts for the effects of overlay designs. In this paper, the pavement responses are determined by the linear theory of elasticity for the system of pavement layers, while the pavement reliability is represented as a series system of two failure criteria: fatigue cracking and rutting. To illustrate the developed model, a numerical study is presented. Sensitivity and importance measures are computed for the parameters and the random variables included in the limit state functions. The sensitivity measures suggest that the initial asphalt layer thickness and the sub-grade stiffness are the critical predictors of the pavement performance after application of a structural overlay.     

水泥混凝土路面加罩沥青面层设计方法

旧水泥混凝土路面进行改造,常采用的处理方法是加铺沥青面层。介绍了旧水泥混凝土路面处理、防止反射裂缝措施、道路设计中纵断面设计和横坡确定。最后以工程实例介绍了设计过程。     

Effect of asphalt film thickness on the moisture sensitivity characteristics of hot-mix asphalt

Temperature, air and water are the common factors that profoundly affect the durability of asphalt concrete mixtures. In mild weather conditions, distresses such as permanent deformation, fatigue cracking can be encountered on the pavements due to traffic loading. But when a severe climate is in question, these stresses increase in poor materials; under inadequate control; with traffic as well as with water which are key elements in the degradation of asphalt concrete pavements. Many variables affect the amount of water damage in asphalt concrete layer. Among them, mixture design properties such as air void level, permeability, asphalt content and asphalt film thickness are the ones that must be investigated carefully.     

路用半刚性基层材料抗裂缝剂应用研究

将研究出的半刚性基层抗裂缝剂添加于道路基层混合料中,通过扫描电子显微镜观测材料微结构形成过程,发现其具有膨胀性和增密性.收缩试验证明,该抗裂缝剂可使道路基层结构因温度和湿度变化所引起的收缩空间大大减少.试验还分析了延迟成型时间对碎石混合料强度的影响,发现抗裂缝剂具有缓凝性能.耐久性试验显示,掺加抗裂缝剂的半刚性基层混合...     

Besonderheiten bei Alkali‐Kieselsäure‐Reaktionen in Betonfahrbahndecken

Characteristics of Alkali Silica Reactions in Concrete Pavements In the last few years cracking in concrete pavements was often associated with an alkali silica reaction (ASR). Even if relevant reaction products were detected in appropriate samples, cracks result only in the rarest cases from an ASR solely. Rather it is assumed, that cracks were caused by a superposition of several stress impacts. Beside restraint stresses due to disabled thermal and hygric self‐deformations, concrete pavements are also stressed by traffic. However, the influence of the alkali silica reaction in concrete pavements can not be neglected. Here especially the infiltration of alkalis from external resources is of a substantial importance. Alkaline deicing agents applied in the winter months are more or less intensively penetrating into the concrete by the following traffic, which leads to a continuous increase of the alkali potential in the concrete. The penetration of the alkalis is forwarded by already existent damages (cracks). Within these circumstances more extensive measures are necessary to avoid damaging alkali silica reactions for concrete pavements in comparison to conventional concrete constructions. In the meantime such measures were decreed by the BMVBS in a relevant circular. The contained requirements refer in particular to the evaluation of critical aggregates and to the permitted alkali content of the cements. The regulations of this decree are initially based on general empirically revealed findings. The actual influence of the alkali silica reaction referring to cracking in concrete pavements is examined in current research projects.     

沥青混合料路面排水存在的问题及解决措施

许多沥青路面道路建成运营后,发生早期损害较为严重,主要表现在开裂、坑槽、车辙、下沉、松散、脱皮、麻面等方面。产生这些病害的主要原因是水的破坏。针对这些问题进行了分析,找出了路面排水存在的问题并提出了相应的解决措施。     

反射裂缝的足尺疲劳试验研究及其力学分析

通过室内足尺疲劳试验,研究了常温和低温条件下反射裂缝的产生过程、产生部位以及特种金属网格防治反射裂缝的效果.试验结果显示,(1)在合适的基础条件下,特种金属网格能有效地防治荷载型反射裂缝,且不因温度的变化而变化;(2)双反射裂缝的产生过程分三阶段第一,拉开阶段,沥青罩面层与旧水泥板因竖向拉应力过大而被拉开,并在荷载的重复作用下,层间拉开范围不断扩大;第二,裂缝产生阶段,层间拉开使得罩面层最大拉应力点内移,裂缝产生的位置也相应地内移,至接缝一定距离处;第三,裂缝扩展阶段,重复荷载拉应力的作用使得裂缝垂直向上扩展,最终以"双裂缝"的形式,反射至薄罩面层的表面.采用三维有限元分析方法,对反射裂缝的产生过程进行了分析,分析结果与试验结果完全一致.     

复合路面荷载型反射裂缝的力学分析和试验路验证

应用经三维光弹试验验证的三维有限元方法分析了层间接触条件、层间拉开宽度、脱空、罩面层厚度、基础模量对反射裂缝产生的单因素和多因素综合影响。同时应用断裂力学原理分析了裂缝长度对反射裂缝扩展速度的影响 ,最后修筑试验路验证了上述力学分析结果     

Design and maintenance criteria for Saudi bituminous concrete mixes

Premature rutting has occurred on a number of highways recently built in Saudi Arabia. The Ministry of Communications, in an effort to solve the problem, has initiated a number of studies and started to replace affected pavements. The aim of this study is to identify possible factors which may relate to rutting and to recommend maintenance and repair criteria for existing rutted pavements. The study covers nineteen sections of eleven major highways. Results indicate a direct relationship between rutting and the percentage of air voids; the percentage of voids in mineral aggregate; the percentage of voids filled with asphalt, resilient modulus at 25°C; and bitumen viscosity. These properties were used as bases for maintenance criteria as well as criteria for the design of mixes to resist rutting on Saudi roads. © 1999 Elsevier Science Ltd. All rights reserved.     

Application of Markov chains and Monte Carlo simulations for developing pavement performance models for urban network management

Existing performance models developed for interurban pavements are not applicable to urban pavements due to differences in traffic demands and deterioration trends. The objective of the study was to develop performance models for the management of urban pavement networks. Markov chains and Monte Carlo simulation were applied to account for the probabilistic nature of pavements deterioration over time, using data collected in the field. One of the advantages of this methodology is that it can be used by local agencies with scarce technical resources and historical data. Eight performance models were developed and successfully validated for asphalt and concrete pavements in humid, dry and Mediterranean climates with different functional hierarchies. The resulting models evidence the impact of design, traffic demand, climate and construction standards on urban pavements performance. Predicted service life of asphalt and concrete pavements in primary networks are consistent with design standards. However, pavements in secondary and local networks present shorter and longer service life compared to design life, respectively. Climate is a relevant factor for asphalt pavements, where higher deterioration was observed compared to that expected. Opposite to this, no relevant differences between design and performance can be attributed to climate in concrete pavements.