Development of Methods for Evaluating the Impact of ...

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ScienceDirect Transportation Research Procedia 20 (2017) 301 – 304

12th International Conference "Organization and Traffic Safety Management in Large Cities", SPbOTSIC-2016, 28-30 September 2016, St. Petersburg, Russia

Development of Methods for Evaluating the Impact of Stress-Strain State Uniformity of Composite Pavements on Road Safety Maria Klekovkina 1a*, Viktor Gorshkov 1b, Anatolii Lialinov 2c 1

Saint Petersburg State University of Architecture and Civil Engineering, 4 2nd Krasnoarmeyskaya str., Saint Petersburg, 190005, Russia 2 Emperor Alexander I St. Petersburg State Transport University, 9 Moskovsky av., Saint Petersburg, 190031, Russia

Abstract The most important quality indicator to optimize the cement concrete and composite structural and technological solutions is the uniformity indicator which is not duly covered in existing regulatory and procedural documents. The proposed findings will increase the service life of pavements and as a result will improve road safety. 2016Published The Authors. Published B.V. © 2017 by Elsevier B.V. by ThisElsevier is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 12th International Conference "Organization and Traffic Peer-review under responsibility of the organizing committee of the 12th International Conference “Organization and Traffic Safety Safety Management in large cities". Management in large cities” Keywords: Uniformity, composite pavements, calculation and designing of road pavements, stress and strain state, sections, reliability, service life

1. Main text According to the results of research and practical works, the most important quality indicator for optimizing cement concrete and composite (asphalt concrete pavements on cement concrete base course) design and technological solutions is the indicator of uniformity of the composition of materials and the technology which ensures uniformity of concrete during laying and consolidation as well as uniform temperature and humidity conditions when curing the concrete layer, selection of the most preferable stress and strain state for the structure (in this case, preferred compression behaviour of the structure); establishing the links between layers and layer components which provide

* Corresponding author. Tel.: 8921-775-12-42. E-mail address: [email protected] a*, [email protected] b, [email protected] c

2352-1465 © 2017 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 12th International Conference “Organization and Traffic Safety Management in large cities” doi:10.1016/j.trpro.2017.01.027

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Maria Klekovkina et al. / Transportation Research Procedia 20 (2017) 301 – 304

the pavement with the stress-strain state with the maximum degree of uniformity based on the minimum coefficient of variation. Uniformity is the degree of stability of physical and mechanical properties, geometric dimensions, process parameters, operating and production conditions [Federation Council (2007)]. The study of the indicator uniformity of the stress and strain state (SSS) of road pavement is not duly covered in existing regulatory documents and, therefore, constitutes the subject of this research. The scope of research is composite pavements. The target of research is to develop a method to study the uniformity of indicators of stress-strain state (SSS) of road pavement to improve traffic safety and their service life. The introduction states that according to the regulations the basic principles of construction of pavements are: x alternative solutions for selection of the optimal "uniformity" as a quality indicator which ensures the longest road service life; x design with regard to "the category of a road, traffic composition, traffic density, climatic conditions, stress state and strain mechanism (including the nature and type of SSS) of individual layers and structural components [Ministry of Regional Development (2012)]; x minimum number of layers of a pavement with maximum use of local and modern building materials; x increasing the robustness of a road (due to high load carrying capacity of all layers except for the upper wear layer in a composite structure) due to the use of rigid pavement layers; x appreciation of the use of joint structural and technological solutions for design, construction and operation of a road structure. Currently used traditional design and technological solutions are not consistent with the principles presented above regarding the quality indicators and do not meet the requirements of modern road and transport infrastructure, including: modern competitive cement concrete pavements and cement concrete bearing layer of composite structures are currently not used, except for one standard alternative, and are rejected in the projects. Currently, the researchers deal only with the analysis of operation of existing structures and fail to address issues of development of new improved structures by carrying out calculations for a standard design using more precise (analytical and more often numerical) methods. Uniformity criteria are considered normally only for materials and are not applied for the study of SSS uniformity of structural elements, and especially road structure in general. Issues related to controlling the SSS of a road structure in terms of its reduction, and most importantly, in terms of its transition into another kind (for example, for concrete from SSS with tensile bending into SSS with compression) are completely disregarded. The accepted design practices are particularly fraught with negative consequences for composite road structures, where the thickness of the asphalt pavement with a high load-bearing capacity of the bearing layer is recommended to be 14-26 cm, which requires three-layer asphalt pavements. In accordance with existing regulations [Ministry of Regional Development (2012)] the following requirements must be met to maintain the necessary transport and performance and load bearing capacity of rigid pavements: x strength, cracking resistance of a pavement and structural layers that can resist bending [Ministry of Regional Development (2012)]. The main criterion is considered to be the permissible tensile stress in bending a cast-in place plates on the elastic base course when exposed to repeated dynamic loads and temperature. At the same time, a major disadvantage of cement concrete with its extremely low resistance to bending is disregarded. Apparently, the main target for optimizing structural solutions is to develop a structure where concrete could work primarily in compression or where tensile stresses go down abruptly; x strength of a pavement on the whole [Ministry of Regional Development (2012)]. Since shear stress is used here as a criterion of strength in discrete layers of the base course and working layer of the subgrade, we believe it correct to speak about the importance of pavement vertical stability, related to changes in the calculation scheme, including areas of where plates have no contact with the base course; emerging of ledges in joints due to incorrect selection of plate sizes, types of joints and their connections. For stability purposes the structural solutions of plates


should be such that the bottom of plates would act on the base course as a hard stamp (to avoid tensile stresses in the plate). Three conditions of stability of a plate shall be noted here as suggested by [Klekovkina (2010)]: a) the first condition of stability will be achieved if the entire bottom of a plate will have compressive stresses (positive) and only in the most remote point of an edge, on the back side of the load application, the stress can be zero. This condition is typical of low moment SSS of operating elements of a fragmented cement concrete plate: σj = 0, where j is an corner point with coordinates хj = – l/2; уj = – b/2; b) the second condition is that the largest absolute value of stress must not exceed the limit for this type of ground during compression:

VQ

V limit ,

where v – the most loaded corner point of a plate; its coordinates are: хv = l/2; уv = b/2; σlimit – design subgrade resistance to compression; c) the third condition is the vertical displacement of the most loaded corner of a plate: Wv = |σv|K = Wlimit, where K – is a coefficient of subgrade reaction; Wlimit – design limit elastic deflection. x according to longitudinal stability of the pavement [Ministry of Regional Development (2012)]. Stability of cement concrete pavement to longitudinal buckling of the pavement due to linear (longitudinal) temperature forces shall be regarded. Regulatory requirements shall provide for calculations in a linear arrangement (in accordance with the design of a pavement which involves the use of joints perpendicular to the longitudinal axis). To reduce and improve the uniformity of SSS it is advisable to have a design solution of a pavement which will ensure a planar setting (compression through the length and breadth of a pavement due to oblique joints); x according to frost resistance of a pavement [Ministry of Regional Development (2012)]. Regulations use allowable winter heaving based on only the force component excluding the kinematic component, determined on the basis of uneven frost heaving – precipitations. Special literature and regulations [Ministry of Regional Development (2012)] on the structural and technological solutions and calculation of cement concrete pavements treat joints separately as thermal expansion joints and transmission links of forces from one plate to the adjacent one, with the plate within its sizes calculated separately with the given boundary conditions. Such an approach can not be considered fair and consistent with actual work of a pavement which shall be viewed as a continuous plate with joints distributed in a most reasonable way. In order to increase the uniformity of SSS (equal strength) the joints shall be used to control the changes in SSS of a bearing layer in a reasonable direction (increasing the uniformity or changing the type of SSS). This refers to the increase of the degree of contact between elements of the pavement and the base course, redistribution of forces in the bearing layer. Compression joints can be regarded as plastic hinges with the statically indeterminate structure as a concrete plate of a pavement or bearing layer. Using the method of limit equilibrium and formation of plastic hinges along the specified directions (for example, due to the weakening of a cross section by notching) will allow adjusting the SSS and optimizing the structural and technological solution to improve uniformity. It is advisable to replace the chaotic cracking in the concrete bearing layer, typical of traditional design and technological solutions with directional (adjustable) cracking, which will reduce the amount of the SSS and its appearance and increase uniformity (equal strength of a structure). Reasonable cuts of a bearing layer in composite pavements will allow adjusting the cohesion between the cement concrete bearing layer and asphalt concrete pavement to prevent cracking in the pavement due to traffic load and climatic factors. Such structures with joints together with

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tight fitting of operating elements to the base coarse provide vibration damping in the structure with joints working as dampers. An alternative of such a structure can be a fragmented concrete base course which includes laying concrete in layers with subsequent fragmenting using a special machining, to make notches which will weaken the cross-section as well as dents of a certain shape to establish the estimated sizes, connections and shape of future bearing elements and subsequent arrangement of an asphalt concrete layer. Conclusion This study gives recommendations – for the design, development and optimization of structural and technological solutions, construction and maintenance of roads – the use of the original quality criterion of uniformity which will increase the reliability and service life of roads. This criterion is not duly covered in the existing regulations. Assessing the level of reliability and service life of the road structure has a determining coefficient, which takes into account the changes in the uniformity of its indicators. This coefficient describes the rate of reduction of uniformity over time which is currently not considered in the design and optimization of a road structure, in particular, for allocation of joints which control the SSS in structural layers between the layers and between the fragments of bearing layers. The research of pavement uniformity during all the life cycle stages of the pavement focuses special attention on development of structural and technological solutions of composite pavements by reasonable fragmentation of a bearing layer which can reduce cracking, rutting and increase the reliability and traffic safety. References Fedotov, G.A., Pospelov, P.I. (2007). Encyclopedia of Road Building. Designing of roads. Moscow, vol.5. Federation Council (2007). Federal Law No. 257-FZ dd. 8.11.2007 On Highways and on Road Works in the Russian Federation and on Amending Specific Legal Acts of the Russian Federation. Klekovkina, M.P. (2010). Improvement of Structures and Building Technology of Pavements with Concrete Base Course. Volgograd: VSUACE, 189 p. Mednikov, I.A. (1988). Strength of Concrete Structures on Elastic Base Course Exposed to Arbitrary Loads Casts. Omsk: SibADI, pp. 94–98. Ministry of Regional Development (2012). Code of Rules. Automobile Roads SP 34.13330.2012 (Revised edition of SNiP 2.05.02-85). Moscow, 109 p. Ministry of Transportation (2004). Design Guidelines for Rigid Pavements. Moscow: INFORMAVTODOR, 128 p Ministry of Transportation (2001). Designing of Non-Rigid Pavements, ODN 218.046-01. Moscow, 144 p. Rocas S.Y. (1977). Statistical Quality Control in Road Building. Moscow: Transport, 152 p. Semenov, V.A. (1989). Quality and Uniformity of Automobile Roads. Moscow: Transport, 125 p.