Comparison of Stress Fields near Longitudinal Construction Joints of Tied and Doweled Sections in Portland Cement Concrete Pavements

In Portland cement concrete (PCC) pavements, tie bars are commonly used at longitudinal construction joints (LCJs) to prevent the lanes from separating. Meanwhile, the increase in multiple lanes due to greater traffic volumes has raised concerns about potential longitudinal cracking; this has led to the use of dowel bars instead of tie bars at LCJs. However, there is a paucity of studies focused on the comparison between the behaviors of concrete pavement based on the restrained conditions provided by tie and dowel bars at LCJs. In this study, we investigated the effects of the placement of tie and dowel bars at LCJs on the potential for longitudinal cracking in response to the increase in concrete stress that may occur when the lanes are tied together in PCC pavements. Field testing verified that the variation in concrete strain was more restrained in the case of a tie bar than a dowel bar, whereas it resulted in higher stress in the concrete element in the tie bar section. However, the use of dowel bars caused more movement in the transverse direction at LCJs as compared with tie bars. Thus, our results indicate that using dowel bars reduces the potential for longitudinal cracking; however, it may increase the potential for lane separation.

THE METHODS OF NON-DESTRUCTIVE TESTING OF POSITIONING OF METALLIC DOWEL BARS IN JOINTS OF RIGID PAVEMENTS

Introduction. In the world-wide practice on construction of rigid road pavements significant attention has been given to jointed plain concrete pavements (JPCP) with transverse joints strengthened by dowel bars. Performance of JPCP is sufficiently affected by right alignment and location of dowel bars thereby the methods of non-destructive testing of dowel bar positioning have been gain in great importance. This paper represents analytical review of methods of non-destructive testing of dowel bar alignment and location emphasizing an attention on standard method using magnetic pulse induction which is applicable to testing of metallic bar position in concrete pavements. General Part. In the general part of this paper, several main aspects of reviewed test method were analyzed: the classification of dowel bars misalignment and their impact on pavement performance; the comparison of implemented methods of non-destructive testing of dowel bar positioning; possibilities of method of magnetic impulse induction and an approach to analytical evaluation of transverse joints dowel bar misalignment using magnetic image tomography; the usage of results of testing of transverse joints dowel bar position to eliminate dowel bars misalignment; examples of predictive estimation of results of testing of transverse joints dowel bar position and their impact on performance of JPCP. The reviewed method of testing and test results estimation concerns practice on application of two levels of performance (e.g. acceptable level and rejectable level) to evaluate the performance of each individual dowel bar or each doweled transverse joint and also a section of rigid road pavement with several consecutive transverse joints with restricted performance. Conclusions. 1. World-wide implemented standard method of non-destructive testing of dowel bar alignment and location allows to detect and to eliminate dowel bars misalignment thus ensuring required load transfer efficiency and international roughness index of rigid road pavements. The estimation of road pavement sections with several consecutive joints considering each joint performance allows to ensure the designed service life of road pavement. 2. Standard method of non-destructive testing of dowel bar alignment and location for transverse joints of rigid road pavement using magnetic pulse induction developed by American Society for Testing and Materials assures high precision of measurement of metallic bar position in doweled bar of concrete pavement joints and enables to detect five types of dowel bar misalignment. 3. In connection with the intensification of issues on construction of rigid road pavements in Ukraine as well as the high importance of the considering test method, an important task should be the development and implementation of an appropriate national standard.

Comparative Study and Analysis of Dry and Wet Connections of Precast Beam-Column under Cyclic Load

At present the Precast building are more focus for the building industrialization and main objective of this study to find the most appropriate types of beam-column connection, the purpose of this study is to investigate and high result of precast beam column joint with two types of dry mechanical connection & two types of wet connection were analysis and compared with monolithic connection to know the performance of the joints. the primary test variable were the type of connection cleat angle, dowel bar, fibre reinforced concrete, steel plate, anchor rod and the pre tension bolt are used in this joints the advantage of the precast concrete structure components are assemble in which are fabricated off-site and then connect on-site in term of less resource consumption, more rapid construction, better quality control and less field wet operation.

Experimental and Numerical Investigation of Deformable Concrete Median Barrier

In South Korea, the number of vehicles is gradually increasing. The number of heavy vehicles in 2010 increased up to 19% in less than five years. Therefore, the chances of heavy vehicle-concrete median barrier (CMB) collision also became higher than in the past; therefore, a need to study a stricter design level for improving the current CMB (CMB-15) under harsher environments arose. Accordingly, in the present study, a new concrete median barrier was designed under a stricter impact severity, SB6(420 kJ), compared to the current design impact severity, SB5-B (270 kJ). In particular, shock absorbing devices to absorb impact energy were applied to the CMB. An empty space allows the dowel bars to deform and absorb collision energy. Therefore, deformable CMB was designed and tested. The key parameters selected in our study were dowel bar and wire-mesh. A series of numerical analyses were conducted to evaluate the proposed new deformable CMB designs with shock absorbers. Finally, the optimal design, CMB-17S, was proposed after several evaluations of the proposed designs and a full-scale field test. It was found that, although the developed model did not accurately predict the impact sequence due to certain differences between the actual truck and the truck model, the permanent deformation after collision could be well predicted. Based on the observations from a full-scale impact test, it was recommended that the top part of the CMB should be strengthened since major volume loss occurred due to local impact, which appeared to be due to punching shear failure.

CYCLIC PERFORMANCE OF HDR HOOK-END PRECAST BEAM-COLUMN JOINT: A FINITE ELEMENT ANALYSIS

Small concrete cover to dowel’s diameter reduces the cyclic performance of precast concrete frame with pinned dowel beam-column connection due to brittle concrete splitting failure around the dowel joint. Besides, utilisation of bearing pad thicker than half of dowel’s diameter causes the dowel bar to sustain greater tensile stress and plastic elongation up to their breaking point due to larger inclination of the dowel bar, particularly under the action of cyclic loading. Hence, a new precast beam-column joint with hook-end configuration and utilizing the advantage of high damping rubber (HDR), was proposed as the alternative for precast structures. Therefore, this study presented the horizontal and vertical cyclic performances of the precast frames with the proposed joint, through numerical analysis using finite element software. The numerical results were compared with a numerical modelled single pinned dowel connected precast frame, which was verified with the experimental results under horizontal cyclic loading. In terms of accumulative energy dissipation capacity, the numerical results showed that precast frames with the proposed joint demonstrated approximately 230% and 120% of improvement at 40 mm of horizontal cyclic level and 7 mm of vertical cyclic level, respectively, than the precast frame with single pinned dowel connection. It indicates that the viscoelastic behavior of HDR has contributed the benefit in this improvement.

A Rapid Detection Method for Bridges Based on Impact Coefficient of Standard Bumping

The evaluation method of load transfer efficiency using falling weight deflectometer is unworkable in remote mountain areas and transportation difficult region. Therefore, a novation method of load transfer efficiency evaluation is proposed using the index of amplitude ratio. Finite element method is applied to study the influence of dowel bar parameters (diameter, length, spacing, and elastic modulus) and pavement structures parameters (thickness and modulus) on load transfer efficiency, frequency, and the ratio of amplitude. Results of finite element model show that the effects of dowel bar and pavement structure parameters on load transfer efficiency and the ratio of amplitude are similar. The load transfer efficiency, frequency, and the ratio of amplitude enhance with the increase of dowel bar diameter, length, and elastic modulus and the decrease of dowel bar spacing. The subgrade modulus has more significant influence on the load transfer efficiency, frequency, and the ratio of amplitude than other pavement parameters. Polynomial function method is utilized to established load transfer mode between deflection-based load transfer efficiency and the ratio of amplitude. The feasibility and reliability of new method is verified by static and dynamic load test. All results are helpful for the development of highway engineering and airport engineering.

Experimental Study on Doweled Expansion Joints on Behavior for Plain Concrete Pavement System

This paper deals with load-deflection behavior the jointed plain concrete pavement system using steel dowel bars as a mechanism to transmit load across the expansion joints. Experimentally, four models of the jointed plain concrete pavement system were made, each model consists of two slabs of plain concrete that connected together across expansion by two dowel bars and the concrete slab were supported by the subgrade soil. Two variables were dealt with, the first is diameter of dowel bar (12, 16 and 20 mm) and the second is type of the subgrade soil, two types of soil were used which classified according to the (AASHTO): Type I (A-6) and type II (A-7-6). Experimental results showed that increasing dowel bar diameter from 12 mm to 20 mm has a little effect on load-deflection behavior of the tested specimens with only 5% increase in failure load. This may be attributed to that the failure (caused by flexural crack) depends mainly on concrete strength. Results also showed that decreasing CBR value of subgrade soil from 7% to 5% decreases failure load by about 33%.