Response analysis of orthotropic steel deck pavement based on interlayer contact bonding condition

In this research the interlayer contact condition was considered between the adjacent layers of orthotropic steel deck pavement, and an interface contact bonding model was applied to simulate the interlayer bonding condition and evaluate the response of deck pavement under vehicle loads. An advantage of this model is that it can simulate not only the full-bond condition but also the debonding condition at somewhere between adjacent layers. The responses of the orthotropic steel deck pavement were calculated and analyzed by the model, and it found that this model is reasonable and credible to evaluate the responses of the deck pavement comparing with the previous researches. The full-bond condition was an ideal condition between adjacent layers, which was prone to underestimate the responses and deformation of the deck pavement. Moreover, the position and size of the disengaging area have a notable influence on the tensile strain at the top of SMA layer and the bottom of GA layer, and the tensile strain of them also increase with the increase of the disengaging area. Finally, the responses of the steel deck pavement changed obviously when the vehicle speed increase, so the suitable speed limit may reduce the responses and deformation for prolonging the service life of the orthotropic steel deck pavement.

New refined analytical models for various bonding conditions of an adhesively bonded smart PZT transducer using the EMI technique

The electro-mechanical impedance (EMI) technique has emerged as a cost-effective and non-destructive technique to detect the possible damages in the structure using a piezoelectric transducer, especially, lead zirconate titanate (PZT). The adhesive bond layer plays an important role in the PZT patch-host structure interaction for monitoring structural damage. Two bonding conditions are investigated in this research paper. Primarily, the debonding phenomenon of the adhesive bond layer may misinterpret the EMI response on the damage caused in structure. Subsequently, the investigation included the protective layer at the top of the PZT transducer to avoid sensor degradation. However, the analytical models developed so far have not considered a protective layer at the top of the PZT transducer. This paper presents the novel two-dimensional (2D) analytical model for incorporating debonding concepts and the new refined 2D analytical model to include a protective layer in the study of surface-bonded PZT transducers. The proposed analytical models are verified with the experimental studies. The experimental and analytical results show good agreement, which confirms the effectiveness of the new models. This paper also incorporated the effect of each bonding condition for monitoring structural damage by implementing the EMI technique. For the simulation, the numerical investigations on the PZT transducer bonded on the metallic (aluminum and steel) and concrete blocks are performed using coupled field analysis through finite element (FE) modeling. It is found that each bonding condition has influenced the resulting signatures. The signatures obtained from developed theoretical models and numerical simulations using three-dimensional FE models for each bonding condition are compared to highlight the influence on structural damage detection. The trend of signatures is found to be matching satisfactory. Several parametric studies have been conducted to show the efficacy of the new refined model with a protective layer. It considers the different input properties of an adhesive layer, host structure, and temperature conditions. The influence of debonding of the protective layer is also studied, and the obtained results support the need for a protective layer in the models.

Application of Wireless Communication in Experimental Research of the Interface Bonding Condition between Asphalt Layers by Tensile Testing

The vigorous development of communication technology, especially the development of wireless network communication technology, has accelerated its informatization process in more and more industrial applications. In the field of monitoring and detection applications, the many advantages of wireless network transmission technology provide an important reference for high-quality compaction monitoring. Engineering practice shows that the construction technology of asphalt pavement is the ultimate guarantee of engineering quality. It is important to recognize that pavement performance is greatly influenced by interface bonding condition and interface failure can reduce the serviceability of pavements rather than their overall structural lifetime. This paper presents a laboratory test to investigate the bonding tensile performance between asphalt layers by tensile testing. The test methods and devices for determining the bond regarding tensile testing are summarized as follows. Different interface conditions have been analyzed herein: 0.2, 0.4, and 0.6 kg/m2 with corresponding emulsified asphalt (MA) and SBS-modified MA. It is found that the stress-strain relationship of tensile testing for interface bonding is similar with low-carbon steels and it can be categorized into four zones. The results of tensile strength and damage displacement are discussed which are key parameters in describing the interface bonding condition and evaluating pavement performance.

A Feasibility Study on Monitoring Pile-Soil Bonding Condition Using Piezoceramic Transducer and Horizontal Impact

The in situ evaluation of pile-soil bonding condition plays an important role for pile safety assessment in its life cycle. However, so far, there is still no fully mature tool to analyze such couplings, since the pile-soil coupling exhibits complex and time-varying relationships. This paper innovatively proposes a health monitoring approach to evaluate the bonding status of the soil and pile contact area. An impact method based on a piezoelectric ceramic sensor is proposed to monitor the bond of pile and soil. A horizontal impact was introduced near the top of the pile, and the induced stress waves were detected by the piezoceramic smart aggregate (SA) sensor embedded in the pile. Different crack damage sizes were made between the soil and the pile to investigate the change of the bonding. An energy index was developed to quantitatively evaluate the quality of the bonding as a pile-soil bonding index. The proposed approach inspired a potential way to directly judge if there is crack damage between the pile and soil and to evaluate pile safety.

Influence of moisture content on NO2 sorption ability of cedar wood

This study examined the influence of moisture content (MC) on NO2 sorption ability of cedar (Cryptomeria japonica) wood using the specimens with different MCs. Four MC conditions were applied, namely 0%, 8.6%, 12.7% and 16.5%, based on the differences of bonding condition of water molecule in the wood substances. As a result, the NO2 sorption volume increased drastically due to the presence of water, and as the MC increased, the NO2 sorption volume increased slightly. The NO generation volume and nitric acid concentration in the specimens were evaluated after an aeration test, and it was strongly indicated that the NO2 reacted with water in the specimen, and that the NO generation volume increased as the content of multilayer adsorbed water increased. The nitric acid seemed to be formed by the reaction between NO2 and water, and it was then held in the specimen. Based on the NO2 sorption volume calculated using the NO generation volume, it was shown that the NO2 sorption after 12-h aeration was caused mainly by the reaction between NO2 and water. Furthermore, the presence of both water and extractives contributed to the NO2 sorption in the initial period, and the presence of water contributed greatly to the NO2 sorption over the long term.

Enhanced CRCP Backcalculation Procedure and Interface Bond Assessment: Volume 3

Falling weight deflectometer (FWD) testing is effective in evaluating the structural response of in-situ concrete pavements through the backcalculated pavement layer parameters. Since Continuously Reinforced Concrete Pavement (CRCP) has closely spaced transverse cracks, the traditional backcalculation assumption of an infinite slab can lead to significant errors in the backcalculated results. In this study, solutions for backcalculated k-value, elastic modulus of concrete (E), and effective thickness (heff) for different crack spacing have been derived from 2-D finite element analysis for both interior- and edge-loaded CRCP. AASHTO sensor configuration (0, 12 in, 24 in, 36 in.) was recommended for CRCP with crack spacing greater than or equal to 6ft, and an alternative solution for crack spacing of 4 and 5ft was proposed with AREA24. Crack load transfer efficiency (LTE) across transverse cracks had limited impact on backcalculated results if the LTE was greater than 80%. According to the sensitivity study, both positive and negative temperature differentials less than 16oF had limited impact on backcalculated parameters. As expected, the backcalulation values were very sensitive to the load plate’s longitudinal position relative to the transverse crack especially for crack spacings smaller than 8ft. For edge-loaded condition, it is important to drop within a 2-inch lateral offset from edge in order to achieve accurate backcalculated results. In addition, the over width of the base provided extra support to CRCP slab resulting in higher backcalculated heff. The proposed backcalculation procedure system was applied to the Tollway field CRCP test section with different crack spacing, reinforcement ratio, and base types. Finally, a procedure for evaluating the slab-base bonding condition using simplified friction model along with backcalculated heff was extended and applied to one of the CRCP test section on Illinois Tollway near Itasca and one on Interstate 57 near Effingham. Based on the analysis of friction coefficient from measured deflection basin, cement treated base (CTB) was shown to provide good support to CRCP slab given the interface bonding condition between slab and base is stable in the long-term (more than 20 years). The combination of warm mix asphalt (WMA) and CTB also has good performance, even though the dynamic modulus of asphalt changes with the temperature causing decreased interface bonding condition in the summer.

The Fabrication of Polymethyl Methacrylate Nozzles for Electrohydrodynamic Printing

Electrohydrodynamic (EHD) jet printing enables rapid prototyping high-resolution and low-cost lines with width of micrometer or even nanometer. However, EHD printing always suffers from nozzle clogging when the nozzle inner-diameter decrease to micro-scale. Thus fabrication of low cost nozzles becomes significantly important. In this work, 50 μm wide and 12.5 μm deep PMMA (Polymethyl Methacrylate) nozzles were fabricated without using traditional expensive glass capillary pulling approach. To replicate PMMA nozzle with high precision, the embossing condition was optimized according to replication precision, the deformation rate, and maximum stress. To nearly fully bond PMMA nozzle with intact PMMA microchannel, the bonding condition was optimized according the bonding rate and dimension loss of PMMA microchannel. The availability of the fabricated PMMA nozzle was finally verified by EHD printing experiments.

Analysis of the Strain Distribution and Texture Measurements in Asymmetric Rolling (AR) and Asymmetric Accumulative Roll Bonding (AARB)

Severe plastic deformation (SPD) with strong shear component is required to promote both grain refinement and texture randomization. When Asymmetric rolling (AR) is applied as asymmetric accumulative roll bonding (AARB), it enables the production of architectured microstructures and metallic composites. Finite element (FE) simulations of AR and AARB were employed to understand the influence of pass thickness reduction (PTR) on the through thickness variation of the velocity gradient. The influence of the PTR up to a total thickness reduction of 50% and the effect of a single 50% reduction step in a bi-layer bonding condition was analyzed. The influence of these process parameters on the strain and rigid body rotation components was compared with the experimental data obtained on an AA1050 aluminum. A better shear to compression ratio across the sheet thickness is achieved by PTRs lower than 30%; at a PTR of 50% the texture is dominated by the frictional shear generated at the roll-sheet interface and the process has a stronger compressive character. This indicates that simple ARB followed by AR with smaller PTRs should generate a better shear distribution than AARB alone.

Full-Scale Evaluation of Concrete-Asphalt Interphase in Thin Bonded Concrete Overlay on Asphalt Pavements

Thin bonded concrete overlay on asphalt (BCOA) pavements rely on concrete-asphalt bonding to resist traffic loading. To investigate variables affecting bonding, experimental data were used from 15 instrumented thin BCOA sections, with 11 tested with heavy vehicle simulators (HVS). Sections included three slab sizes, four rapid-strength concrete mixes, new and old asphalt bases, and three asphalt surface texturing techniques. Analysis of strain data from HVS testing served to determine the concrete-asphalt bonding condition. Laboratory testing and forensic data from the sections were also evaluated. Overall, the performance of concrete-asphalt bonding in the sections with 1.8 × 1.8 m (6 × 6 ft) slabs was excellent. In these sections, concrete-asphalt bonding remained intact throughout the HVS testing despite the unfavorable testing conditions, which included flooding of the section, channelized traffic at the slab edge, and HVS wheel (half axle) loading of up to 100 kN (22.5 kips). The sections with 3.6 × 3.6 m (12 × 12 ft) slabs presented a delamination band between the asphalt and concrete along the perimeter of the slabs. This delamination was a tensile break occurring in the asphalt around 5–10 mm (0.2–0.4 in.) below the concrete-asphalt interphase caused by the large vertical hygrothermal deformations in the slabs. Because of this asphalt failure, the concrete and asphalt worked as two independent layers near the transverse joints. Based on laboratory procedures, it was observed that cement paste penetration into the asphalt layer caused a reinforcing effect in the concrete-asphalt interphase. It was also observed that milling and micromilling did not improve the concrete-asphalt bonding.