The reaction of the subgrade is vertical only and is proportional to the. Pdf rigid pavement stress analysis topic 8 rigid pavement. Friction stresses l l2 h friction between concrete slab and its foundations induces internal tensile stresses in. Rigid pavementrigid pavement 20 deflection is very small hence the name rigid pavement. In the design of a rigid pavement, the flexural strength of concrete is the major factor and not the strength of subgrade. In rigid pavement the stresses are not transferred from the grain to grain to the lower layers. The effect of wheel loads on pavements matti huhtala technical research centre of finland vit, finland abstract the effects of wheel loads on pavements are important for technical reasons pavement design and bituminous mixture design, for administration regulation of legal axle and total loads of vehicles, for economical calculations. Rigid pavement is designed and analyzed by using the elastic theory. A major functiop of any pavement is to spread the concentrated load delivered to it by the wheel sufficiently so that the stress ultimately transmitted to the underlying soil will not cause shear nor excessive deformation. Typically, the target consistence is about 50 mm and below, when determined in the form of slump, or between 0. However, the dynamic effects were not taken into account in most pavement design and studies. On the contrary, in rigid pavements, wheel loads are transferred to subgrade soil by flexural strength of the pavement and the pavement acts like a rigid plate e. Many of the photos used in this appendix are from the ltppdistress identification manual.
Rigid pavement has sufficient flexural strength to transmit the wheel load stresses to wider below. Twolayer theory burmister topic 3 flexible pavement stress analysis 5. Guide to using existing pavement in place and achieving long life. The rigid pavements are made of cement concrete either plan, reinforced or prestressed concrete. The flexible pavement system action is more complexthe load is spread. Critical condition of stress in the rigid pavement is the maximum flexural stress occurring in the slab due to wheel load and the temperature changes. Differences in temperature between the top and bottom surfaces of a pcc slab will cause the slab to curl.
These factors tend to result in deformations of the concrete slab. The following results were obtained 1 subgrade deflection 0. Vertical stresses in subgrades beneath statically loaded. The rigid pavement undergoes temperature, wheel load and frictional stresses. Paul guyer is a registered civil engineer, mechanical engineer, fire protection engineer, and architect with over 35 years experience in the design of buildings and related. For a given pavement structure stress or strain of xkip load on axle type y. Rigid pavements respond to loading in a variety of ways that affect performance both initial and longterm. The civilweb aashto rigid pavement design spreadsheet completes the design of concrete roads or pavements in accordance with aashto 1998. The asphalt institute in college park, maryland has issued a asphalt thickness and design, manual that suggests that asphalt. Material containing subgrade and environment condition are also responsible for stresses in the pavement. The top most paved surface of such type of pavement is flexible, that is extremely dependent on the underlying layers.
Two dimensional finiteelement programs have been in use for the past two decades to analyze rigid pavement response. Pdf a rigid pavement is a structure consisting of superimposed layers of processed materials above the natural soilsubgrade, whose primary. Topic 3 flexible pavement stress analysis developed solutions for. Due to this property of pavement, when the subgrade deflects. The flexible pavement, having less flexural strength, acts like a flexible sheet e. Finiteelement analysis is not new to the pavement design and research community. The load pulse generated by the fwd momentarily deforms the pavement under the load plate into a dish. There are various types of stresses yields in flexible and rigid pavements under the applied live load. Based on the force imparted to the pavement and the. A 30in rigid plate was used to determine the load deflection characteristics.
Stresses in flexible pavement rutting engineering intro. To investigate the influences of roadway roughness on pavement stresses, this study developed a coupled system consisting of a quartercar model and an equivalent lump pavement model. Pavement roughness causes pavement stress fluctuation along the road. Stresses in pavements elastic halfspace solutions 1. Introduction to rigid pavement design ced engineering. The fwd generates a load pulse by dropping a weight. Stress in rigid pavement 203477 pavement structure 1 weerakaset suanpaga d. Christos drakos university of florida topic 8 rigid pavement stress analysis cause of stresses in rigid pavements. Rigid pavement analysis and design fhwa us department of.
The high flexural strength is predominant and the subgrade strength does not have much importance as in case of flexible pavement. The stresses are not transferred from grain to grain to the. A certain flexible pavement consists of 2in bituminous surface, 7in crushed stone base course, and 9in sandy subbase. Effects of pavement roughness on rigid pavement stress. This report will be of interest to engineers involved in rigid pavement design and anal ys i s. National academies of sciences, engineering, and medicine. In the present study, a rigid pavement test section consisting of two jointed reinforced concrete pavements and two jointed plain. Stresses are the response of loading on the pavement. Higher stress is less favourable under a total evaluation, e. In rigid pavement applications, the consistence of concrete is normally very low, due to the operation requirements.
For critical design, a combination of load stress, frictional stress and warping stress is considered. Design of rigid pavements is based on westergaards analysis, where modulus of subgrade reaction, radius of relative stiffness, radius of wheel load distribution are used. At each point in the system there exists a certain orientation of the element such that the shearing stresses acting on each face are zero. The rigid pavement does this by beam or slab action. Pdf stresses and strains in flexible pavement using. The normal stresses under this condition are principal stresses and are denoted by s. Section 5 rigid pavement construction standard specification for urban infrastructure works 51 edition 1, revision 0 september 2002 contents 5 rigid pavement construction 53 5. Pavements and surface materials page 2 slabs and paver stone embedded in reinforced concrete are examples of rigid pavement. Although the calculation and measurement of deflections on the pavement. With respect to asphalt concrete pavements, the current failure criteria used are the horizontal tensile strain at the bottom of the asphalt concrete layer and the vertical strain at the top of the subgrade layer. Or rigid pavements are those, which reduces the stress concentration and distributes the reduced stresses uniformly to the area under the. In rigid pavement, load is distributed by the slab action, and the pavement behaves like an elastic plate resting on a viscous medium figure 19. Figure 30 is a nomograph that determines the effective modulus of subgrade reaction. Bumps, settlements, and heaves in concrete pavements may be due to frost heave, swelling or collapsing soils, or localized consolidation.
The rigid pavements are made of portland cement concrete either plain, reinforced or prestressed concrete. Highway engineering became prominent towards the latter half of the 20th century after world war ii. Photo 1 water logging problems with flexible pavements photo 2 cracks in rigid pavement. Types of pavements flexible pavement rigid pavement. Highway engineering is an engineering discipline branching from civil engineering that involves the planning, design, construction, operation, and maintenance of roads, bridges, and tunnels to ensure safe and effective transportation of people and goods. This load pulse is transmitted to the pavement through a 300millimeter mm diameter circular load plate. Westergaard solved for stresses and displacements in rigid pavements for three loading conditions denoted as interior, edge, and corner loading. Stresses in rigid pavements stresses in rigid pavements result from variety of sources, of which the applied vehicle loads, changes in temperature of the slab, friction between the slab and the subgrade or base course are the most important. Several accelerated pavement tests have been recently completed on fullscale jointed plain and continuously reinforced concrete pavements and are summarized below. Experimental study on structural response of rigid pavements. Flexural strength a measure to control quality of rigid concrete pavements.
Effects of warping stresses on rigid pavements why vignan. Maintenance and rehabilitation is to be properly done to. Engcandidate department of civil engineering faculty of engineering, kasetsart university. This lecture includes following topics design of rigid pavements what are rigid pavements. Onelayer theory can be applied as an approximation for a conventional flexible pavement with granular basesubbase with a thin asphaltic layer on a stiff subgrade comparable to the basesubbase. Analytical and experimental stresses in concrete pavements. A project description form pdf was prepared for state agencies interested in. Properties of rigid pavements components of rigid pavements created by aman dembla help the. Rigid pavements are those which posses note worthy flexural strength or flexural rigidity.
Example total twoway traffic 3000 cvpd at the end of construction period flexural strength of concrete 45kgcm2 modulus of subgrade reaction 8 kgcm3. Appendix a pavement distress types and causes this appendix provides descriptions of the types and causes of the distresses that occur in asphalt, concrete, and asphaltoverlaid concrete pavements, and asphalt and concrete shoulders. Westergaard considered the rigid pavement slab as a thin elastic plate resting on soil subgrade. Twolayer systems the exact case of a twolayer system is the fulldepth asphalt pavement construction in which a thick layer of hotmix asphalt is placed directly on the subgrade. Computed tensile stresses across bottom of pcc slab at midpoint. Temperature differential between the top and bottom of the slab causes curling warping stress in the pavement. Conclusion rigid pavement distress is a serious issue all over the world, the distresses causes some serious problems at wide range. Stresses in rigid pavements principles of pavement design. Rigid pavements are constructed by portland cement concrete pcc and should be analyzed by plate theory instead of layer theory, assuming an elastic plate resting on viscous foundation.
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