Visual Condition Assessment Research Articles

A visual condition assessment of a reinforced concrete railway bridge subject to alkali silica reaction (ASR) deterioration in Johannesburg

In the 1940’s, a reinforced concrete (RC) railway bridge located in central Johannesburg was constructed using Witwatersrand Quartzite, at the time, unknown to be an alkali-silica reactive aggregate. The bridge currently displays signs of distress in the form of severe map-cracking. This study presents preliminary results of a series of tests that have been conducted to characterise the severity of alkali silica reaction (ASR) deterioration in the bridge. Twelve concrete cores were extracted for testing from various locations of the railway bridge, which displayed varying degrees of distress. A visual assessment was conducted globally on the entire structure as well as locally (using modified damage rating index (DRI) approach) on the extracted cores. The findings showed that there was extensive map-cracking present on all thirteen railway bridge elements examined, revealing signs of distress in the bridge. Even elements that were sheltered from exposure to direct rain, such as the underside of three arch surfaces, also exhibited extensive map-cracking. Furthermore, the modified DRI method was a useful technique to assess and compare the relative extent of damage of concrete taken from various locations of a RC structure, using local images of the cylindrical surface of the concrete cores.Graphical

Performance evaluation of continuous reinforced concrete pavement constructed in hilly region

Continuously reinforced concrete can be an excellent pavement solution for heavy traffic. The CRCP technique eliminates the transverse joints as it contains longitudinal reinforcement. This paper presents the details of CRCP road constructed by author, challenges faced due to steep gradient and heavy rainfall and the techniques adopted to resolve the issues. This CRCP road is being utilized for mixed type of traffic, including heavy traffic for last four years without any maintenance. The performance evaluation has been carried out recently by adopting Visual Condition Assessment Survey Technique. The measurements for various distress parameters such as longitudinal cracking, transverse cracking, punchouts, hairline cracks and joint deterioration, have been carried out. Also, the special observations noted during the Visual condition assessment survey have been discussed in detail. The performance evaluation shows that the CRCP is in ‘Low Severity Level’. The case study presented in detail and the performance evaluation carried out shows that CRCP is an effective technique for pavement construction.

Can Prediction and Understanding of Water Quality Variation Be Improved by Combining Phosphorus Source and Waterbody Condition Parameters?

Phosphorus (P) pollution impairs river systems globally. There is long-standing interest in understanding catchment source P loads to inform mitigation to improve water quality. However, P sources to the hydrosphere differ individually in discharge behaviour, P intensity, bioavailability, and cumulative impacts. River condition also varies (e.g., riparian disturbance, climate change impacts) such that source and river resilience are likely synergistic but poorly studied controls on water quality variation. To challenge the use of overly-simplistic factors (e.g., basic soils and landcover) in empirical catchment pollution source-impact assessments, we pooled spatial data according to conceptual aspects of P source mechanisms and waterbody riparian condition. These were related empirically to P concentrations and loads, and trophic diatom indices, for 19 Scottish catchments (~10–250 km2) representing some mechanistic aspects of pollution loading and river impacts. Sources of P from septic tanks and farmyards influenced loads and ecological impacts. Some secondary calculations pooling spatial data such as septic tank source-delivery methods were novel, involving complex, but available, soil water flowpath data. In contrast, inclusion of channel condition and farmyard P loads used simple aerial imagery. Multiple Factor Analysis combined with Redundancy Analysis showed that source P loads expressed as bioavailable forms of P were better explanatory factors of diatom classification groups than stream soluble reactive P concentrations, although used together they improved explanation further. Riparian quality metrics were less powerful predictors than expected, likely with more scale-dependant effects on ecological functions than can be quantified by visual condition assessment on isolated short reaches. There was strong justification for examining separate P fractions (total, dissolved, particulate and bioavailable forms) by distinct catchment source types to understand better nutrient dynamics across land to waters, ecosystem degradation and waterbody impacts in the contemporary hydrosphere.

Understanding Durability Problems with Dolerite in Roads in South Africa

Dolerite is one of the most widely used road pavement construction materials in South Africa and is classified as a basic crystalline rock. The variable performance of road pavements constructed with such rocks in South Africa has frequently been linked to the durability of the freshly crushed dolerite which can undergo rapid deterioration in service. This poor durability affects the life cycle of the road as they can fail prematurely. The prevailing conditions under which rapid deterioration of dolerite occurred on the road are somewhat contradictory. The objective of this study was to provide insight into what influences rapid deterioration in dolerite when used in the base course of road pavements. The evaluation was completed by conducting surveys, field investigations and laboratory experiments comprising mineralogical analyses and engineering tests. Surveys were done to identify the investigation sites. Field investigations comprise visual condition assessment of road pavement surface and pavement structure using test pits. Field investigations were followed by a sampling of material from the identified investigation sites for laboratory material testing. Laboratory testing included standard engineering soil tests and specialised techniques for mineralogical analysis. Two approaches for durability investigations were followed. For each approach, two samples were used (control sample and investigated sample), and the results of the sample investigated were compared with the control sample results. Findings from both approaches were compared. An interesting finding was that, contrary to conventional wisdom, not all of the dolerites investigated contained discernible smectite contents.

MONITORING PERFORMANCE OF LATERITE BASE TRIAL SECTION: A CASE OF ADDIS ABABA, ETHIOPIA

This paper is aimed to present an overview of the provision of a demonstration/research trials with particular reference to pavement performance of a laterite base under a double bituminous surface treatment (DBST) as part of a long-term pavement performance (LTPP) monitoring in Ethiopia. The research components were aimed at increasing the use of locally available materials and solving specific problems related to the performance of some roads constructed with thin asphalt seals. In Ethiopia, most roads are built using crushed rock for road base. The project aim was to demonstrate that whether laterite can be used for base course, assess and evaluate the effect of sealed and unsealed shoulder in cut and fill sections. Out of the various field data measurements carried out in each monitoring period (wet and dry season) the paper reviews the in-situ dynamic cone penetrometer (DCP) test results and visual condition assessment observations. It is demonstrated that for such low volume roads laterite base trial sections are performing well, however DCP test results in these sections reveals that the crushed base control sections perform slightly better than the laterite base trial sections and the sections in cut are stronger than in fill while the shoulder sealing doesn’t provide consistent effect on the layer strengths.

Detection and Imaging of Debonding in Adhesive Joints of Concrete Beams Strengthened with Steel Plates Using Guided Waves and Weighted Root Mean Square.

Strengthening of engineering structures is an important issue, especially for elements subjected to variable loads. In the case of concrete beams or slabs, one of the most popular approaches assumes mounting an external reinforcement in the form of steel or composite elements by structural adhesives. A significant disadvantage of adhesive joints is the lack of access to the adhesive film for visual condition assessment, thus, there is a need for non-destructive diagnostics of these kinds of connections. The aim of this paper was the identification and visualization of defects in adhesive joints between concrete beams and steel plates using the guided wave propagation technique. The initial theoretical and numerical analyses were performed. The experimental wave field was excited and measured by the scanning laser Doppler vibrometry. The collected signals were processed by the weighted root mean square (WRMS) calculation. As a result, 2-D damage maps were obtained. The numerical simulations were performed to corroborate the experimental results. The results showed that the guided waves could be successfully applied in non-destructive diagnostics of adhesive joints between concrete and steel elements. However, the quality of damage visualizations strongly depended on the location of excitation.

Live‐Pressure Main Investigations Yield Unique Insights

Water utilities that need to investigate their assets without shutting down service can now do so with visual and acoustic methods that inspect pressurized potable water mains. Such technology frequently uses a high‐definition closed‐circuit television camera for visual condition assessment, a hydrophone for leak detection, and a sonde for pipeline tracing or asset location.

Biological responses to environmental contamination. How can metal pollution impact signal honesty in avian species?

Environmental pollution, for example with metals, can significantly affect the ecosystem balance leading to severe changes. Biologically active pigments are relevant for the appearance and condition of birds. Melanin and carotenoid particles are the most frequently deposited pigments in avian integument. They are responsible for the majority of colors of bird plumage. The phenotypic expression can be affected by metal contamination. It can be manifested as color bleaching or differences in the size of plumage badges. In this study, we performed a comprehensive review of related studies in order to estimate the underlying population effect of this potential dependency. The study is based on the review of the literature regarding several avian species. It was designed to identify an area where the effect of the exposure is still poorly known. The analysis was specifically conducted to investigate the correlation between trace element concentration and eumelanin deposition. Moreover, we searched for factors that could affect spectral properties of feathers with carotenoid‐based pigmentation. As a result, we found carotenoid‐based pigmentation to be of a good use in terms of visual condition assessment. Changes in melanin‐based pattern should be analyzed separately for eu‐ and pheomelanin as well as for a range of essential and toxic elements. Comprehensive studies on the subject are still scarce. Therefore, the issue requires further investigation.

Phytoextraction with Salix viminalis in a moderately to strongly contaminated area.

We tested the suitability of Salix viminalis for phytoextraction with the analysis of selected elements in soil, root, and leaf, and by visual tree condition assessment in an area with varying levels of contamination. Bioconcentration factor (BCF) and translocation factor (TF) were used to assess the phytoextraction potential of willows. The middle part of the study area was strongly contaminated, while the northern and southern parts were moderately contaminated. We found increasing element concentrations toward deeper layers. Mean concentrations of elements in roots were similar among the three parts, while in leaves the highest concentrations were found in the strongly contaminated part of the study area. Tree condition scores were the lowest in the strongly contaminated part of the study area, which was caused by Al, Ca, K, Mg, Ni, Sr, and Zn concentration. These elements induced leaf disease and leaf feeders. The highest BCF values were found for Cu, Fe, Mn, and Zn in root, and for Cd and Zn in leaves, indicating that S. viminalis had high accumulation potential of these elements. Furthermore, TF values were high for Cd, Mn, Sr, and Zn. Our results also demonstrated that soil element composition has major influence on the condition of S. viminalis individuals. Furthermore, visual condition assessment was found to be a useful tool to assess the phytoextraction potential of trees.

Evaluation of Condition Assessment of Tunnel Lining using Inspection Manual of CIRIA and FHWA

Maintenance need to be provided as the tunnel has serves such a long time and it is to ensure no severe failure in the tunnel will occur that would lead to the unwanted causalities. This paper presents visual condition assessment of tunnels of hydroelectric power station to determine deterioration level of shotcrete lining based on FHWA, and CIRIA report C671. From the assessment, it is found that 40% of leakage condition is in rating 2 for MAT and 63% also leakage in rating 2 for CVT. The most severe area is along Chainage 0+300 for MAT and Chainage 0+400 for CVT. Shotcrete lining is also found able to function properly to provide drainage diverting the leaking.

City of Santa Rosa Addresses Hidden Vulnerabilities with Comprehensive Condition Testing

City of Santa Rosa Addresses Hidden Vulnerabilities with Comprehensive Condition TestingThe City of Santa Rosa retained Carollo Engineers to conduct a comprehensive condition assessment of their Laguna Treatment Plant (LTP) to improve reliability. Phase 1 of the project involved a multi-discipline visual condition assessment of the plant. This phase was conducted to evaluate the condition, remaining useful service life, criticality, and risk for each mechanical and structural asset...Author(s)Rebecca OveracreJoseph SchwallMike DadikThomas MossingerSourceProceedings of the Water Environment FederationDocument typeConference PaperPublisherWater Environment FederationPrint publication date Oct, 2013ISSN1938-6478DOI10.2175/193864713813673758Volume / Issue2013 / 16Content sourceWEFTECCopyright2013Word count288

Mapping stone surface temperature fluctuations: Implications for lichen distribution and biomodification on historic stone surfaces

Abstract The exposure of historic stone to processes of lichen-induced surface biomodification is determined, first and foremost, by the bioreceptivity of those surfaces to lichen colonization. As an important component of surface bioreceptivity, spatiotemporal variation in stone surface temperature plays a critical role in the spatial distribution of saxicolous lichen on historic stone structures, especially within seasonally hot environments. The ornate limestone and tufa stairwell of the Monastery of Cartuja (1516), Granada, Spain, exhibits significant aspect-related differences in lichen distribution. Lichen coverage and diurnal fluctuations in stone surface temperature on the stairwell were monitored and mapped, under anticyclonic conditions in summer and winter, using an infrared thermometer and Geographical Information Systems approach. This research suggests that it is not extreme high surface temperatures that determine the presence or absence of lichen coverage on stonework. Instead, average stone surface temperatures over the course of the year seem to play a critical role in determining whether or not surfaces are receptive to lichen colonization and subsequent biomodification. It is inferred that lichen, capable of surviving extreme surface temperatures during the Mediterranean summer in an ametabolic state, require a respite period of lower temperatures within which they can metabolize, grow and reproduce. The higher the average annual temperature a surface experiences, the shorter the respite period for any lichen potentially inhabiting that surface. A critical average temperature threshold of approximately 21 °C has been identified on the stairwell, with average stone surface temperatures greater than this generally inhibiting lichen colonization. A brief visual condition assessment between lichen-covered and lichen-free surfaces on the limestone sections of the stairwell suggests relative bioprotection induced by lichen coverage, with stonework quality and sharpness remaining more defined beneath lichen-covered surfaces. The methodology employed in this paper may have further applications in the monitoring and mapping of thermal stress fatigue on historic building materials.

Is what you see what you get? Visual vs. measured assessments of vegetation condition

An important step in the conservation of biodiversity is to identify what exists, its quantity and its quality (i.e. condition). This can be a daunting task at the landscape-scale, so vegetation communities are often used as surrogates for biodiversity. Satellite imagery has improved our ability to rapidly measure vegetation parameters but the need for calibration still requires rapid and cost-effective on-ground condition assessment. Some management agencies address this need by using visual condition assessments, with unknown consequences for the different purposes of condition data. It is therefore vital to examine the comparability of visual and systematic condition assessment methods to guide their use in conservation decision making. We compared visual assessments of vegetation condition with more systematic and higher resolution on-ground assessments, using a method where both assessments were made for the same quadrats. We determined both the condition parameters observers respond to when making visual assessments of condition, and the consequences of any differences for the application of these data. We found that visual assessment of vegetation condition broadly represented measured assessments of the same vegetation, but that observers simplify their assessments by responding to only some of the measured condition parameters. No consistent trends were found in the parameters observers responded to across the different vegetation types sampled.. Synthesis and applications. We conclude that visual estimates of vegetation condition are only of sufficient resolution to replace more expensive, high-resolution assessments at a landscape-scale, when condition results are combined over multiple areas and vegetation types. Visual assessment methods potentially can provide an efficient measure of overall condition for conservation management agencies where practitioners can make assessments of condition in the course of their daily management activities - an important step forward. At smaller scales, idiosyncratic effects render visual estimates highly variable when compared with systematic condition assessments. This variability, especially among vegetation types, suggests that more systematic assessments are necessary when management decisions require higher-resolution estimates of changes in individual condition parameters, such as when measuring the success of individual management actions. These findings provide a valuable guide for selecting the most appropriate approach for the different objectives of condition assessments for biodiversity conservation. © 2010 The Authors. Journal compilation

Role of mortars in the decay of granite

Conservation work carried out at Trinity College, Dublin, highlighted problems of decay in granite which is widely regarded as a durable stone. Visual condition assessment of stone work identified an association between decay of granite and the presence of salts. Salt build-up was related to the presence of sources of soluble salts. Mortar joints and limestone features in particular were identified as potential sources of damaging salts. Petrographic analysis of thin sections taken from high and low salt surface environments revealed decay processes typical of granite weathering. Fracturing and chemical alteration of minerals were evident. Decay processes in the sample from the high salt location were more extreme. Analysis of calcium and sulphate in these locations revealed an association between disruption of the stone and high levels of salts. The physical role of mortar in controlling the water movement through the stone is also important in determining where damaging salts are deposited. A new repointing mortar was developed and tested. This mortar has high permeability and flexibility while having a low soluble salt content.