Fiber-reinforced polymer (FRP) composites have gained increasing recognition and application in the field of civil engineering in recent decades due to their notable mechanical properties and ...chemical resistance. However, FRP composites may also be affected by harsh environmental conditions (e.g., water, alkaline solutions, saline solutions, elevated temperature) and exhibit mechanical phenomena (e.g., creep rupture, fatigue, shrinkage) that could affect the performance of the FRP reinforced/strengthened concrete (FRP-RSC) elements. This paper presents the current state-of-the-art on the key environmental and mechanical conditions affecting the durability and mechanical properties of the main FRP composites used in reinforced concrete (RC) structures (i.e., Glass/vinyl-ester FRP bars and Carbon/epoxy FRP fabrics for internal and external application, respectively). The most likely sources and their effects on the physical/mechanical properties of FRP composites are highlighted herein. In general, no more than 20% tensile strength was reported in the literature for the different exposures without combined effects. Additionally, some provisions for the serviceability design of FRP-RSC elements (e.g., environmental factors, creep reduction factor) are examined and commented upon to understand the implications of the durability and mechanical properties. Furthermore, the differences in serviceability criteria for FRP and steel RC elements are highlighted. Through familiarity with their behavior and effects on enhancing the long-term performance of RSC elements, it is expected that the results of this study will help in the proper use of FRP materials for concrete structures.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
We examined the effect of point-source inputs from wastewater treatment plants (WWTP) on in-stream uptake of ammonium, nitrate and phosphate and compared it between two streams draining catchments ...with contrasting land use. The selected streams were La Tordera and Gurri (NE Spain), draining a forest- and an agriculture-dominated catchment, respectively. In each stream, we compared nutrient uptake metrics, estimated from nutrient additions, between two reaches located upstream and downstream of a WWTP input. Measurements were done on 8–9 dates during 2002–2003.
In La Tordera, the point-source increased concentrations of all studied nutrients; whereas in Gurri, this effect was less evident. Point-source effects on nutrient uptake differed between the two streams, and among solutes. In La Tordera, uptake lengths (S
w) of ammonium and phosphate averaged hundreds of meters above the point-source, and increased (i.e., decreased uptake efficiency) 4 and 5 times, respectively, below the point-source. S
w of nitrate was ≥
2
km regardless of reach location. In Gurri, S
w of all studied nutrients was within the km range in the two reaches. In this stream, diffuse nutrient inputs from adjacent fields may overwhelm the local effect of the point-source input.
Uptake velocities (v
f) of the studied nutrients ranged between 10EXP
−
6
and 10EXP
−
4
m/s in the two streams, and were similar between the two reaches in each stream. However, phosphate v
f decreased under increasing concentrations following a power function. This trend remained significant when combining our results with those compiled from literature, suggesting the efficiency loss response may be a general trend for phosphate across streams.
The relative increases in uptake rates (U) below the point-source were proportional to the relative point-source contribution to downstream nutrient loads, especially for ammonium and nitrate. However, the increases in U were not enough to compensate for the increases in nutrient loads downstream of the WWTP input.
►Point-sources can affect stream hydrology and chemistry. ►Consequently, point sources can affect stream functioning (i.e., nutrient uptake). ►These effects may be modulated by the landscape context (e.g., catchment land use).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Early surgical procedures on patients with infective endocarditis (IE) have shown a clearly benefit to reduce embolization at the central nervous system. We conducted a retrospective cohort in ...Mexican population to evaluate mortality and clinical outcomes in patients with IE with or without surgical intervention.
Our aim was to evaluate factors associated with mortality in patients with IE and compare both groups with and without a surgical intervention.
We evaluated a retrospective cohort of patients who had been diagnosed with IE according to the Duke's criteria at our Institution in SLP, Mexico, from January 2001 to September 2016. We compared the risk factors associated to mortality of patients with or without surgery. Our primary outcome was mortality within 6 months of follow-up after the diagnosis.
We included 105 patients, 51 (48.6%) were men, median age 46 Q1 30, Q3 59 years, 36 patients (34.3%) received surgical treatment (STG), and 69 (65.7%) only medical treatment (MTG) group; 41 patients (39%) died during the study period; in the surgery group eight patients died (22%); and 33 in the MT group (47%) p = 0.049. Adjusted for APACHE II, surgery, creatinine levels and the size of vegetation, the surgery group had lower mortality than patients on MTG (HR 0.36, p = 0.047).
As previously described in the literature, patients who underwent surgery had lower mortality than the patients who only received medical treatment; however, the Mexican population is different to other populations group, due to higher risk of diabetes mellitus (28%) versus (10%) in global risk of DM in the world and its complications and other chronic diseases as arterial systemic hypertension. Thus, surgical treatment must be elected as goal standard treatment in patient's whit IE and presence of vegetation.
We found Rickettsia parkeri in Amblyomma ovale ticks collected in Veracruz, Mexico, in 2018. We sequenced gene segments of gltA, htrA, sca0, and sca5; phylogenetic reconstruction revealed ...near-complete identity with R. parkeri strain Atlantic Rainforest. Enhanced surveillance is needed in Mexico to determine the public health relevance of this bacterium.
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DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Fiber-reinforced polymer (FRP) composites offer a corrosion-resistant, lightweight, and durable alternative to traditional steel material in concrete structures. However, the lack of established ...inspection methods for assessing reinforced concrete elements with externally bonded FRP (EB-FRP) composites hinders industry-wide confidence in their adoption. This study addresses this gap by investigating non-destructive testing (NDT) techniques for detecting damage and defects in EB-FRP concrete elements. As such, this study first identified and categorized potential damage in EB-FRP concrete elements considering where and why they occur. The most promising NDT methods for detecting this damage were then analyzed. And lastly, experiments were carried out to assess the feasibility of the selected NDT methods for detecting these defects. The result of this study introduces infrared thermography (IR) as a proper method for identifying defects underneath the FRP system (wet lay-up). The IR was capable of highlighting defects as small as 625 mm2 (1 in.2) whether between layers (debonding) or between the substrate and FRP (delamination). It also indicates the inability of GPR to detect damage below the FRP laminates, while indicating the capability of PAU to detect concrete delamination and qualitatively identify bond damage in the FRP system. The outcome of this research can be used to provide guidance for choosing effective on-site NDT techniques, saving considerable time and cost for inspection. Importantly, this study also paves the way for further innovation in damage detection techniques addressing the current limitations.
To increase the knowledge and experience gained from the existing literature regarding the bond behavior of glass fiber-reinforced polymer (GFRP) rebars, a total of sixteen full-scale GFRP-reinforced ...concrete beams were subjected to a four-point bending test. The GFRP reinforcement comprised a single M16 (No.5) GFRP sand-coated bar without confinement reinforcement in the constant moment region. The research parameters encompassed three different lap-spliced lengths (i.e., 40-, 60- and 80-db) and two distinct concrete clear covers (i.e., 19 mm and 38 mm) to assess their impact on bond strength and failure modes. Strain gauges along the GFRP rebar and small potentiometers positioned at the end of the splice within the constant moment zone allowed detailed measurements. Rebar slippage in lap-spliced specimens was observed to have a limited impact on bond stress transfer capacity and member flexural stiffness until reaching maximum slippage. Concrete cover significantly influenced the behavior of lap-spliced GFRP-RC beams, with 38 mm-cc specimens exhibiting an average 21% higher capacity compared to 19 mm-cc specimens. The ACI expression exhibited an average overestimation of 24% for 19 mm-cc specimens, whereas for 38 mm-cc specimens, it offered a more accurate estimation, with only a 10% over-prediction. However, the computed lap splice length to achieve the required tensile stress was reduced from the one required by ACI due to extra factors implemented in the development length equation. This aligns with prior research findings that identified unconservative values of bond stress when employing the ACI provisions for specific combinations of parameters, highlighting the necessity for refinements in predictive models.
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•Inadequate lap splice lengths lead to premature failure modes characterized by concrete splitting.•Lap-spliced and un-spliced specimens exhibits similar deflection levels under the same applied load.•Rebar slippage in lap-spliced specimens has a limited impact on bond stress transfer capacity and member flexural stiffness until reaching maximum slippage.•Concrete cover significantly influenced the behavior of lap-spliced GFRP-RC beams.•Current ACI 440.11–22 equation may not reliably predict bond capacity for lap-spliced GFRP rebars.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Antecedentes: El cuestionario de discapacidad de brazo, hombro y mano (DASH, Disabilities of the Arm, Shoulder and Hand) mide el impacto de patologías del miembro superior en la calidad de vida. Sin ...embargo, su uso en la población mexicana no ha sido formalmente validado. Objetivo: Realizar la adaptación cultural y validación del cuestionario DASH para conocer la perspectiva de pacientes con trastornos neurogénicos del miembro superior respecto al impacto en su calidad de vida. Método: Se realizó una adaptación al vocabulario mexicano de la versión española del cuestionario DASH y se aplicó en 478 voluntarios. Se estimaron el efecto techo, el efecto suelo, la correlación ítem-total, las medidas de tendencia central de ítems y el puntaje total, la consistencia interna, la precisión y la validez transversal y longitudinal mediante la comparación de individuos sanos y enfermos con diferente nivel de discapacidad. Resultados: Nuestra versión del cuestionario DASH resultó equivalente a las previamente aprobadas y mostró homogeneidad de los ítems respecto al valor total del cuestionario (alfa de Cronbach > 0.96). Además, tuvo una precisión de 7.25 puntos y se documentó la validez transversal y longitudinal con diferencias significativas entre grupos y subgrupos con diferente nivel de discapacidad. Conclusiones: El cuestionario DASH puede ser empleado con un nivel de confianza alto en la población mexicana.
•Integration of chemical, biological and ecotoxicological studies is here assessed.•DGTs and BCR are good tools to predict metal accumulation in macroinvertebrates.•Microtox is useful when chemical ...and biological quality tests are in disagreement.
The objective of the present work was to assess the ecosystem status of Francolí river (Catalonia, Spain), a Mediterranean stream basin with contrasting human influences. An integrated approach was designed by combining physicochemical, biological and ecotoxicological analyses. The content of metals (As, Cd, Cr, Co, Cu, Hg, Ni, Pb, and Zn) was analyzed in samples of water, benthic sediments and aquatic macroinvertebrates. In addition, the potentially bioavailable fraction of metals in water and sediments was determined by using diffusive gradient in thin-films (DGTs) and sequential extraction of sediments (BCR), respectively. The biological quality was evaluated through aquatic macroinvertebrate communities, while the ecotoxicological status was assessed by Microtox® with Vibrio fischeri. Finally, an analysis of acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) was performed to evaluate the sediment toxicity associated to metal content. According to the results, DGTs and BCR are suitable methodologies to predict the potential bioavailable fraction of metals in freshwater systems. Moreover, ecotoxicity evaluation by means of V. fischeri, in combination with the chemical characterization and the biological quality assessment, should be complementarily used to get a better diagnose of freshwater systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Fiber-Reinforced Polymer (FRP) composites have emerged as a promising alternative to conventional steel reinforcements in concrete structures owing to their benefits of corrosion resistance, higher ...strength-to-weight ratio, reduced maintenance cost, extended service life, and superior durability. However, there has been limited research on non-destructive testing (NDT) methods applicable for identifying damage in FRP-reinforced concrete (FRP-RC) elements. This knowledge gap has often limited its application in the construction industry. Engineers and owners often lack confidence in utilizing this relatively new construction material due to the challenge of assessing its condition. Thus, the main objective of this study is to determine the applicability of two of the most common NDT methods: the Ground-Penetrating Radar (GPR) and Phased Array Ultrasonic (PAU) methods for the detection of damage in FRP-RC elements. Three slab specimens with variations in FRP type (glass-, carbon- and basalt-FRP, i.e., GFRP, CFRP, and BFRP, respectively), bar diameter, bar depths, and defect types were investigated to determine the limitations and detection capabilities of these two NDT methods. The results show that GPR could detect damage in GFRP bars and CFRP strands, but PAU was limited to damage detection in CFRP strands. The findings of this study show the applicability of conventional NDT methods to FRP-RC and at the same time identify the areas with a need for further research.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Abstract
Fiber-reinforced polymer (FRP) composites are becoming increasingly popular as an alternative to conventional civil engineering materials in existing structures as externally applied systems ...for strengthening purposes, and in new structures as internal reinforcements in the form of bars, meshes, and strands. The next phase of development in the application of FRPs in concrete structures could culminate in elements possessing both internal and external FRP systems simultaneously. With these advancements in the application of FRP in civil engineering, it is conceivable that traditional steel reinforcements could become obsolete in certain aggressive and hostile environments, such as coastal areas. Although higher durability and performance are associated with FRP materials in some respects when compared to steel, concerns remain regarding the damage and defects in this material, many of them related to their unique features. Regardless, similarly to other structural materials, it is necessary to understand the damage and defects associated with the use of FRP composites, as well as to identify their sources. This knowledge will support the positive prospects for FRP technology, promoting its application in civil infrastructure. Accordingly, this study investigated the types, characteristics, and identification of the observed or expected damage and defects associated with using FRP in reinforced and strengthened concrete elements. The damage was classified according to location and time of initiation. In addition, the sources of these defects and damage were determined, and a damage etiology was established for preventing the occurrence of such damage in future use. The results of this study are intended to provide the background for the development of a guide and training material for the inspection of structures that use FRP materials. The ability to inspect and properly maintain structures containing FRP will result in the enhanced durability and service life of concrete structures reinforced or strengthened with FRP materials.
Practical Applications
With advancements in the application of fiber-reinforced polymer (FRP) in civil engineering and the development of practical means for its use in design and construction, it is conceivable that traditional steel reinforcements could become obsolete in certain aggressive and hostile environments, such as coastal areas. Although higher durability and performance is associated with FRP when compared to steel, concerns remain regarding the potential damage and defects that could be associated with its use. To help the owners of concrete structures feel comfortable with this relatively new application, guides and procedures are needed that will support the inspection and detection of potential damage in FRP. For this, it is necessary to understand the damage and defects that can occur in externally and internally applied FRP, and to be able to identify their sources. In this study, we investigated the types, characteristics, and identification of observed or expected damage and defects associated with using FRP in reinforced and strengthened concrete elements. In addition, the sources of these defects and damage were determined and a damage etiology established as a basis for developing a guide and training materials for the inspection of structures that use FRP materials. An accurate understanding of such damage and its sources could be used for maintenance and preventive measures for structures that were constructed using FRP materials.
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