Durability Assessment Methods Research Articles

The durability of acetylated beech (Fagus sylvatica L.) laminated veneer lumber (LVL) against wood-destroying basidiomycetes

The overall aim of this study was to investigate the durability of acetylated beech (Fagus sylvatica L.) laminated veneer lumber (LVL) against wood-destroying basidiomycetes. The secondary objective was to test whether the specimen size affects the mass loss and durability assessment of wood-material under test. The durability test was based on the pre-standard prEN 113-3. Six materials (acetylated beech LVL, untreated beech LVL, beech solid wood, pine sapwood (Pinus sylvestris L.), larch (Larix decidua Mill.) 3-layer slab, larch solid wood) were tested using three specimen geometry designs (50 × 25 × 15 mm3 as well as 50 × 50 × 19 mm3 with and without sealed edges) against Coniophora puteana, Rhodonia placenta, Gloeophyllum trabeum, Trametes versicolor, and Pleurotus ostreatus. The durability assessment was made using the arithmetic mean and median percentage mass loss (ML), the relative ML (x-values), and the decay susceptibility index (DSI). It was found that mass loss was affected by the test fungus, the material, and the specimen size and design, with the latter being the most essential factor in this study. In addition, the assessment parameter had a significant effect on the durability classification. Furthermore, small differences in ML resulted in different durability classes (DC) in some cases, whereas large differences in ML did not. However, acetylated beech LVL was always considerably durable (DC 1) against all tested fungi independent of the specimen design and durability assessment method.

Diesel Engine Emission Aftertreatment Device Aging Mechanism and Durability Assessment Methods: A Review

To meet more and more stringent emission standards, the combined technologies must be used to purify the emission pollutants of vehicle exhaust. Among them, the aftertreatment devices, including DOC, SCR, DPF, and so on, are the most efficient methods. However, after long-term running, the performance of the aftertreatment devices will inevitably degrade. There are several mechanisms that can be used to explain the aging phenomena. For the catalytic devices, such as DOC and SCR, thermal aging and poisoning aging are the most important reasons for their performance deterioration. As for DPF, ash clogging is a key problem for its stable working. To develop and test aftertreatment devices better and faster, the accelerated aging methods must be researched and applied. The small-sample aging method enables accelerated aging of catalyst samples at a very low cost, but its aging accuracy may not be good enough. Although the results of the whole-vehicle aging method and bench engine aging method are more in accord with the real using course, they take too much time and are too expensive to be used widely. Burner aging is a promising way to simulate the long-term running of the catalysts.

Dynamic Bayesian network for durability of reinforced concrete structures in long-term environmental exposures

Reinforced concrete (RC) structures under the marine environment may be subjected to chloride-induced corrosion of reinforcement, which significantly impacts the structural serviceability and reliability and further affects the sustainability and development of society. However, most of the existing durability assessment methods for RC structures only address their static and deterministic durability prediction and assessment at the design stage given the constant environment, ignoring the influences of stochastic environmental effects, uncertainties in structural properties, and inspection results. To this end, this paper proposes a dynamic Bayesian network (DBN) based durability assessment framework combined with a deterioration model that considers random changes in environmental parameters, convective chloride ion transport, and corrosion-induced cracking of concrete. In this framework, two-dimensional chloride transport and its influences on the durability deterioration assessment are concerned and achieved using the finite difference method. Besides, to reduce the deviations in probabilistic evaluation, the good-lattice-point-set-partially stratified-sampling (GLP-PSS) method is employed to establish a DBN framework. The proposed DBN framework is used for sensitivity analysis through a real-world example to examine the effects of the environmental model, chloride transport mode, and inspection results of concrete crack on durability assessment.

Durability Assessment Method of Hollow Thin-Walled Bridge Piers under Rockfall Impact Based on Damage Response Surface

Continuous rigid-frame bridges across valleys are often at risk of rockfalls caused by heavy rainfalls, earthquakes, and debris flow in a mountainous environment. Hollow thin-walled bridge piers (HTWBP) in valleys are exposed to the threat of impact from accidental rockfalls. In the current research, ANSYS/LS-DYNA is used to establish a high-precision rockfall-HTWBP model. The rockfall-HTWBP model is verified against a scaled impact test performed in previously published research. A mesh independence test is also performed to obtain an appropriate mesh size. Based on the rockfall-HTWBP model, the impact force, damage, and dynamic response characteristics of HTWBP under a rockfall impact are studied. In addition, a damage assessment criterion is proposed, based on the response surface model, combined with the central composite design method and Box–Behnken design method. The main conclusions are as follows: (1) the impact force of the rockfall has a substantial impulse characteristic, and the duration of the impulse load is approximately 0.01 s. (2) The impacted surface of the pier is dominated by the final elliptic damage, with conical and strip damage areas as the symmetry axis. The cross-sectional damage mode is from compression failure in the impact area and shear failure at the corner. (3) The maximum displacement occurs in the middle height of the pier. The maximum displacement increases with impact height, impact velocity, and rockfall diameter and decreases with the uniaxial compressive strength of the concrete. (4) The initial impact velocity and diameter of the rockfall are the most significant parameters affecting the damage indices. In addition, a damage assessment method, with a damage zoning diagram based on the response surface method, is established for the fast assessment of the damage level of impacted HTWBP.

A New Durability Assessment Method for Volcanic Rocks Used as Building Stones; ‘Modified Static Rock Durability Index’

A New Durability Assessment Method for Volcanic Rocks Used as Building Stones; ‘Modified Static Rock Durability Index’

Relationship between chloride diffusion coefficient and ASTM C1202 electric flux under different environments and durability evaluation

The relationship of the diffusion coefficient and charge passed is developed employing the analysis of the traditional model and 244 groups of experimental data. The differences in the types of concrete were considered to determine the variation coefficient of the diffusion coefficient in the models. Results revealed that the different environmental conditions of the concrete chloride diffusion coefficient cannot be described solely by the existing maturity method. Reasonably good agreement is observed between the experimental and computational model of this paper, thus indicating that the proposed prediction model can be successfully used to estimate the chloride diffusion coefficient. An example of a durability assessment is performed to verify the applicability of the concrete durability assessment method. The concrete durability assessment method can control the durability quality and direction of the production of concrete.

A new durability assessment method of the tuffs used in some historical buildings of Cappadocia (Turkey)

Cappadocia region in Turkey is known as a touristic and historical area with volcanic rocks formed by the effect of intense Neogene calcalkaline volcanism. Rhyolitic to trachyandesitic tuffs, being widespread as a volcanic rock in this region, are used as building stone in historical structures and many monuments with cultural heritage. However, since they have variable durability performances, it is important to evaluate the durability of tuffs for restoration purposes. The aim of this study is to characterize the tuffs using their properties including effective porosity, water absorption, dry and saturated unit weights, dry and saturated uniaxial compressive strengths, dry and saturated point load strengths, dry and saturated sonic velocities and slake durability index, and to estimate the long-term durability of tuffs based on the correlation between field performances and measured properties of the tuffs. In the context of this study, 13 tuff samples used in ancient monuments with good durability performances were taken from nine quarries of Kayseri and Aksaray areas in the Cappadocia region. The physical and mechanical properties of these tuffs were investigated. The properties of these tuffs and the ones with poor durability based on the literature data were compared. A series of correlation graphs using unit weight, effective porosity, water absorption, sonic velocity, and uniaxial compressive strength values of all tuffs has been developed to identify durable and non-durable tuffs. Among these, effective porosity (by volume)-dry sonic velocity and effective porosity (by volume)-dry uniaxial compressive strength pairs yield better durability assessment for the tuffs.

Methods of improving the fire and explosion safety of operation of liquefied hydrocarbon gas transportation tanks

Introduction. The problem of fire and explosion safety of liquefied hydrocarbon gas transportation arose in the 1970s. The task was set to design new generation tanks having improved technical and economic parameters and indicators to ensure fire and explosion safety. The co-authors have conducted the analysis of regulatory documentation covering the fire and explosion safety of hydrocarbon gas transportation tanks, which shows the absence of any unified policy in the design of cars designated for hazardous cargoes. Hence, a number of models, having no or insufficiently effective protective devices, are produced. Therefore, the issues of fire and explosion safety were understudied in the earlier research works on design of railroad cars, and the problem has not been resolved. Principal actions aimed at the fire and explosion safety of hydrocarbon gas transportation tanks were implemented by the Russian University of Transport (MIIT). Statistical information on fire hazardous failures and fleet tank accidents, as well as their detailed investigation has been collected. Tank barrel vulnerabilities have been identified; reliability and durability assessment methods have been developed. Priorities for improving the pressurized tank design are outlined. The following items of work have been performed: ● analysis of statistical data on hazardous cargo transportation accidents, ● development of fire hazard emergency scenarios; ● improvement of “Railroad car analysis and design regulations”, ● development of mathematical models designated for the analysis of tanks, ● identification of an unstable temperature field inside a tank barrel, if in the seat of fire, using non-linear heat conduction equations and the finite element method (FEM), ● identification of the stress-strain state of a tank barrel during a fire. Conclusions. Following the completion of the work performed by the Russian University of Transport (MIIT), hydrocarbon gas tanks have obtained a better barrel emergency impact protection. A unified policy in the design of cars for hazardous cargoes is needed and regulatory documentation requirements must be harmonized.

Durability assessment of structural sealant glazing systems applying a performance test method

ABSTRACT During the service life of a Structural Sealant Glazing (SSG) facade, its silicone bond is simultaneously exposed to climatic and mechanical loads. Current durability assessment methods yet schedule separate test programmes for accelerated weathering and mechanical loading. This study presents a durability test that applies mechanical loading and weather cycling simultaneously simulating 50 years of use. Two common structural sealants are tested. The mechanical behaviour of medium-scale system specimens in tension, compression and shear is recorded for performance assessment during exposure. Moduli and dissipated energies show a characteristic decrease, indicating stress relaxation and degradation. Tensile and shear moduli and strengths of sections cut out from the system specimens after exposure are notably reduced by combined loading compared to those of reference and weathered specimens. Differences between performance and durability characteristics of the two sealants are consistent, also regarding supplementary visual inspection and hardness measurements. The approach introduced in this article provides a basis for more comprehensive performance-related durability testing of SSG-systems.

Calculation method for the service life of Chinese historical reinforced concrete buildings

Almost all of the existed studies on the corrosion of rebars were based on round-section rebars. However, the square-section steel rebars were widely used in China from 1912 to 1949, and there was no specific calculation model or durability assessment method for this type of historical buildings. In this study, based on the original configuration design of this kind of structures, the experiments of the corrosion-induced cover cracking of a certain number of reinforced concrete members with square-section rebars were carried out with the electrochemical acceleration method. The average rust depths of the square-section rebars at the critical corrosion-induced cover cracking moment were obtained. Then, the calculation method of critical rust depth of steel rebars at the concrete cover cracking moment was presented with data fitting method. Finally, combining with predication of carbonization life of concrete, a calculation method of the service life for Chinese historical RC buildings using square-section rebars was proposed. The research results can provide the basis for the durability assessment and conservation for Chinese historical RC buildings.

Durability Assessment of Lightweight Cellular Concrete in Subgrade by the Method of Analytic Hierarchy Process Combined with Fuzzy Comprehensive Evaluation

The durability of lightweight cellular concrete (LCC) and the corresponding assessment method are studied in this paper to improve the utilization of LCC in subgrade construction engineering. The durability assessment method is established by combining the analytic hierarchy process (AHP) with fuzzy comprehensive evaluation (FCE). The main assessment processes are as follows. Firstly, based on the physical and mechanical properties of LCC, the influencing factors are selected in terms of preliminary design, construction technology, and operation and management after completion of construction. The grading standard of influencing factors is established as well. Secondly, a multilevel assessment model with targets level, criteria level, and indexes level is established. AHP determines the effective weight of the lower level relative to the upper level. The consistency check of the judgment matrix is conducted to prove the rationality of the distribution of influencing factors’ effect weight. Thirdly, the membership function which is suitable for each influencing factor is built to calculate the membership degree. Besides, the practicality and reliability of AHP combined with FCE are demonstrated through a practical engineering case, which is the third section of a highway in Guangdong Province, China.

Experimental study of a controlled variable double-baffle distortion generator engine test rig

In order to explore the total-pressure distortion test assessment method for a turbofan engine, a Controlled Variable Double-Baffle Distortion Generator (CVDBDG) with a horizontal symmetry moving form was developed, which can adjust the steady-state and time–variant distortion separately in real time. The inlet total-pressure distortion test was conducted on an afterburner turbofan engine. The distortion parameters of CVDBDG and the instability characteristics of the engine were measured. The experimental data were modeled and analyzed by using back propagation artificial neural networks, and the work envelope of CVDBDG was obtained. Based on the analysis of the data on the engine’s instability, the properties of CVDBDG used for the stability assessment were preliminarily evaluated. The results show that CVDBDG can simulate both steady-state and time–variant distortions simultaneously in a range determined by three envelopes. Under the condition of symmetric double baffles, a critical depth of insertion exists, beyond which the symmetric baffles will generate an asymmetric flow field. In the case of double baffles, compared to a single baffle, the engine exhibited different instability characteristics. Based on CVDBDG, it is expected that more efficient engine stability and durability assessment methods can be developed.

Durability Assessment of Reinforced Concrete Bridge Based on Fuzzy Neural Networks

In the operation process of bridge structures, some bridges appear early failure without reaching design reference period due to the influences of external environment, vehicle load and other factors. Therefore, the problem of structure durability is very obvious. In this paper, a new durability assessment method is proposed based on fuzzy neural networks, which can take account of the defects and deficiencies of existing durability assessment methods. The simulation for learning and testing samples indicates that the proposed method possesses good learning ability and predictive analysis ability. Actual project verifies the effectiveness of the method

Physical durability of PermaNet 2.0 long-lasting insecticidal nets over three to 32 months of use in Ethiopia

BackgroundEthiopia scaled up net distribution markedly starting in 2006. Information on expected net life under field conditions (physical durability and persistence of insecticidal activity) is needed to improve planning for net replacement. Standardization of physical durability assessment methods is lacking.MethodsPermanet®2.0 long-lasting insecticidal bed nets (LLINs), available for distribution in early 2007, were collected from households at three time intervals. The number, size and location of holes were recorded for 189 nets used for three to six months from nine sites (2007) and 220 nets used for 14 to 20 months from 11 sites (2008). In 2009, a “finger/fist” sizing method classified holes in 200 nets used for 26 to 32 months from ten sites into small (<2 cm), medium (> = 2 to < =10 cm) and large (>10 cm) sizes. A proportionate hole index based on both hole number and area was derived from these size classifications.ResultsAfter three to six months, 54.5% (95% CI 47.1-61.7%) of 189 LLINs had at least one hole 0.5 cm (in the longest axis) or larger; mean holes per net was 4.4 (SD 8.4), median was 1.0 (Inter Quartile Range [IQR] 0–5) and median size was 1 cm (IQR 1–2). At 14 to 20 months, 85.5% (95% CI 80.1-89.8%) of 220 nets had at least one hole with mean 29.1 (SD 50.1) and median 12 (IQR 3–36.5) holes per net, and median size of 1 cm (IQR 1–2). At 26 to 32 months, 92.5% of 200 nets had at least one hole with a mean of 62.2 (SD 205.4) and median of 23 (IQR 6–55.5) holes per net. The mean hole index was 24.3, 169.1 and 352.8 at the three time periods respectively. Repairs were rarely observed. The majority of holes were in the lower half of the net walls. The proportion of nets in ‘poor’ condition (hole index >300) increased from 0% at three to six months to 30% at 26 to 32 months.ConclusionsNet damage began quickly: more than half the nets had holes by three to six months of use, with 40% of holes being larger than 2 cm. Holes continued to accumulate until 92.5% of nets had holes by 26 to 32 months of use. An almost complete lack of repairs shows the need for promoting proper use of nets and repairs, to increase LLIN longevity. Using the hole index, almost one third of the nets were classed as unusable and ineffective after two and a half years of potential use.

Evaluation of Ultimate Serviceable State of the Cross-Sea Bridge Pier under Freeze-Thaw and Erosion Coupling Effect

In order to put forward a durability assessment method of concrete structure based on the engineering calculation and analysis, combining with the characteristics of northern freezing coastal areas and the non-navigable spans bridge construction，the paper built the Ottosen strength criterion on concrete under freeze-thaw and erosion coupling effect. By the application of strength criterion, calculation and analysis, it has been evaluated the crack resistance at a few key points of the concrete pile cap on the bottom. The result illustrates that there will appear concrete cracks at the middle of the cushion cap bottom after a 130-year serviceable period when the bridge is attacked by the once-in-a-century wave load or ice load, that is, the safety serviceable period of the bridge pier is 130 years.

Durability assessment of the Alaçatı tuff (Izmir) in western Turkey

Alacati tuff has been used extensively as a source of building stone for outdoor and indoor decorations since the historical times in and around the tourist town of Alacati (western Turkey). The use of the Alacati tuff in buildings has been made compulsory by the Alacati municipality, for preserving the historical appearance of the buildings, after 2005 in Alacati. It has been noticed that, evident deteriorations developed in tuff surfaces of the stone buildings and garden walls within 5–6 years of their emplacement. Durability properties of the Alacati tuff are evaluated by determining the mineralogical, chemical, and physico-mechanical properties of the fresh tuff samples obtained from the only operative quarry in the area. Ageing tests such as Na2SO4 and MgSO4 salt crystallization, freezing–thawing, and wetting–drying were conducted on the fresh tuff samples to assess their durability. Additionally, the durability of the tuff is also evaluated by determining its average pore diameter, saturation coefficient, wet-to-dry strength ratio, static rock and slake-durability indices. Fresh Alacati tuff has high porosity and low unit weight and strengths and are classified to be very poor to moderately durable stone based on the test results of different durability assessment methods. Mineralogical and geochemical analyses have also been carried out on the deteriorated tuff samples collected from the surfaces of the stone buildings to determine the effect of weathering on tuff and the test results have been compared with those of the fresh tuff samples. There is no major difference observed between the mineralogy and chemistry of the fresh and weathered tuff samples thus, it has been concluded that physical weathering has been dominant in the area in deterioration of tuff.

Deterioration mechanisms of tuffs in Midas monument

Slightly weathered white and pink tuffs of the Midas monument have deterioration problems. In this study, depths and characteristics of the weathering zones developed within the tuffs are investigated through optical microscopy, X-ray diffractometry (XRD), chemical analyses, scanning electron microscopy (SEM) and some index parameters. Accelerated weathering tests including wetting–drying, freezing–thawing and salt crystallization are performed, and durability assessment methods are used to predict the durabilities of the tuffs. The findings are compared with field observations. By examining quantitative weathering indices and comparing them with thin section studies, it is found that thin section analyses of the crystals, LoI, and WPI are good indicators to quantify the depth of weathering for the tuffs. However, thin section studies have limited value for fine-grained tuffaceous matrix. The chemical weathering of the tuffs produces weathered zones that are 4.5-cm thick within the white tuff and 2.5-cm thick within the pink tuff. Physical weathering causes scaling of outer layers of the tuffs and fracturing of feldspars along their cleavage planes. However, variations of the index properties of the tuffs due to weathering are not so significant to quantify the weathering depths in the tuffs. Among the accelerated weathering tests, salt crystallization is found to be the most destructive environmental condition. Pigeon droppings rich in NO 3 1− are found to be the main source of soluble salt at the Midas monument. The salt transported up by capillary rise due to surface water causes spalling of the tuffs in the capillary zone. Surface water and salt of any kind in the close vicinity of the monument should be totally eliminated for the purpose of conservation. Field observations and the durability equations reveal that the white tuff is less durable than the pink tuff. Wet-to-dry strength ratio yields a better stone durability assessment among various durability methods used in this study.

Analyses of deterioration of the Cappadocian tuff, Turkey

The Cappadocian tuff contains unique erosional features, the so-called fairy chimneys, some of which in the past were dwelled in and contain valuable wall paintings. These historical heritages, however, are undergoing chemical and physical deterioration due to atmospheric effects. For the conservation studies, understanding of the deterioration phenomenon of the tuff is essential. In this study, engineering geological and physicochemical characteristics of the tuff were determined. The durability of the tuff was assessed through wetting-drying, freezing-thawing, and salt crystallization. The test results suggest that chemical weathering may be traced to a depth of 2 cm below lichen-covered surfaces and 20 cm adjacent to discolored joint walls. Based on durability assessment methods, the tuff may be classified as having poor to very poor durability.