cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.14307236.v1
title: Effect of carbon nanotubes sonication on mechanical properties of cement pastes

description: Abstract The excellent mechanical properties of carbon nanotubes (CNTs) make them a highly attractive material for use as reinforcement in cement composites. However, it is established that this nanomaterial presents a severe dispersion problem in cement matrices owing to its high specific surface area. An alternative method for dispersing the CNTs is the use of sonication in the presence of a superplasticizer admixture. However, high energy sonication can severely damage CNTs, which can affect their behavior in cement pastes. Thus, it is necessary to optimize the CNTs sonication parameters to optimize the performance of CNT-cement pastes. After sonication with different energies of CNTs water suspensions, the CNTs dispersion was evaluated through UV-Vis spectroscopy and the eventual CNTs damage observed by TEM. Workability, compressive and flexural strengths of the CNTs-cement pastes were also measured. The results revealed that the sonication parameters can be optimized to enhance the effect of CNTs on cement paste behavior.
DOI: 10.6084/m9.figshare.14307233.v1
title: Characterization of pervious concrete focusing on non-destructive testing

description: Abstract This study aims to investigate the properties of pervious concrete focusing on characterization tests by the Ultrasound Method. For this, three mixtures were produced with the paste/aggregate (P/Ag) ratio ranging from 0.45 to 0.65, water to cement ratio (w/c) of 0.3, and all the specimens were compacted with a steel rod. The application of the ultrasound method deserves special attention for the characterization of pervious concrete, due to a lack of research and the potential to develop analytical models for predicting properties from ultrasonic pulse velocity (UPV) as an independent variable. The UPV obtained in this study ranged from 3642 to 4262 m/s for an approximately 12% reduction in porosity, with a correlation (R²) of 0.91. It is noteworthy that the high porosity of pervious concrete causes attenuation of the ultrasonic wave. The measurements of UPV had higher values for specimens with higher densities (R²=0.87), higher compressive and tensile strengths (R² of 0.79 and 0.84, resp.), and lower permeability (R² = 0.91).
DOI: 10.6084/m9.figshare.14307231.v1
title: Evaluation of the impact of two types of steel fibers (SE), mono and 3D, on concrete properties, when added isolated or blended

description: Abstract The brittle behavior of concrete can be compensated by the addition of reinforcements, providing benefits such as improved crack control, residual strength and increased flexural strength. It is usual to apply mono fibers to concrete, but their positioning in the matrix may not be homogeneous, consequently increasing the susceptibility to fracture planes with fewer reinforcements. This study aimed to evaluate the use and behavior of simple (mono) and space (3D) steel fibers (SE), in order to achieve a more homogeneous mixture, increase the effectiveness of fibers in restricting cracks and improve mechanical properties. The fresh-state was assessed through slump and VeBe tests, whereas the hardened-state tests comprised axial compressive strength, flexural strength and the flexural toughness factor. The volume content of simple and space fibers varied from 0 to 0.93%. Based on the results, it can be stated that space and simple fiber contents improved rheological and mechanical properties of the composite in isolated (0.29%) and hybrid (0.64%) combinations, since their overall performance exceeded the other mixtures’. However, space fibers caused considerable workability losses compared to the conventional concrete, hindering its casting and harming its hardened-state properties.
DOI: 10.6084/m9.figshare.14307228.v1
title: Fire behavior of shallow prestressed hollow core slabs from computational modeling

description: Abstract Prestressed hollow core slabs are one of the structural systems whose use has increased the most in recent years in Brazil due to its efficiency and versatility. They can be used in many types of structural systems, such as masonry, precast concrete, cast-in-place concrete and steel structures. However, there are few analytical models to evaluate the fire behavior of hollow core slabs. In a simplified way, the fire resistance is evaluated indirectly through the minimum distance of the surface in contact with fire to the reinforcement axis. In this paper, some numerical models in finite element software were developed to analyze the variation of temperature with ﬁre exposure time of shallow hollow core slabs, focusing on the presence of voids in the transversal section of the slab. The 500 °C isotherm method applied to 20 cm high slabs confirmed the Standard Fire Resistance obtained from the tabular method. However, when applied to shallow prestressed hollow core slabs that are 16 cm high, the 500 °C isotherm method indicated that the Standard Fire Resistance of these slabs is lower than values obtained from tabular methods.
DOI: 10.6084/m9.figshare.14307227.v1
title: Experimental study on precast beam-column connections with continuity reinforcement for negative bending moments

description: Abstract In this paper, an experimental investigation is presented on semi-rigid interior beam-to-column connections constituted by precast concrete beams supported on precast concrete column corbels and bending continuity reinforcement bars for bending negative moments. The main purpose of this paper was to analyze the influence of vertical interface grout filling between the corbel and the beam and the position of the bending continuity reinforcement bars (crossing only the column or crossing only the slab) on the behavior of this type of connection. Tests on eight specimens were performed. It was noticed that the vertical interface grout filling contributed to increase both rotational flexural stiffness and flexural strength capacity of the connections when compared to the connections without grout filling. It was also noticed that in the specimens in which the continuity bars crossed only the column, the rotational flexural stiffness was higher. For these last ones, coefficients k and β for predicting the secant stiffness by simplified expression present in Brazilian Code NBR 9062 were evaluate from experimental results. These evaluated coefficients may be regarded as indicative values for structural designers and helpful for future researches.
DOI: 10.6084/m9.figshare.14307225.v1
title: Numerical model of beam-to-column composite connection between slim floor system and composite column

description: Abstract The slim floor system has been used mainly due to the structural and constructive advantages of it, such as the capacity to overcome large spans with the low height of the composite floor system. There is a lack of finite element modelling researches of composite connections between the slim floor system and columns, especially with the concrete infilled steel tube columns. This paper presents the numerical approach based on the solid modelling, for the simulation of the nonlinear structural behavior of composite connection between partially encased composite beam and concrete infilled steel tube column; in this model, the composite beam represents the slim floor. The ABAQUS finite element code was used to investigate the behavior of composite connection that consists of a shear steel plate and negative reinforcement of the composite slab. In this paper, the authors discusses the procedures to the numerical model construction including finite elements and boundary conditions. Besides, the influence of stress-strain relationships for concrete and steel and the parameters that defines each model are presented and discussed, as well as the different steel to concrete interface conditions. Based on the results obtained, the effectiveness of the numerical model developed was verified against experimental results showing a good agreement response for the Moment vs. Rotation response, as well as the moment resistance of the composite connection.
DOI: 10.6084/m9.figshare.14307224.v1
title: Reliability analysis of a prestressed bridge beam designed in serviceability limit state as recommended by NBR 6118 and 7188

description: Abstract Nowadays it is known that it is important to study the safety of structures to avoid tragic accidents or economic losses. The most widely used method in the world to evaluate the safety of structures is structural reliability. The reliability index of prestressed precast beams of bridges designed using Brazilian standards (NBR6118 and NBR7188) is not known. This work evaluates the annual reliability indexes of a prestressed precast beam bridge at the serviceability limit state (SLS) projected using the Brazilian standard and compares it with results from the literature. The studied bridge has 33.5 meters of span, is simply supported, constituted by five precast concrete beams with U section. The reliability analysis was carried out using two methods for the four limit state equations: First Order Mean Value (FOMV) and First Order Reliability Method (FORM). Sensitivity analyzes were performed to consider both the relative contribution of these variables and the effect of their distributions on the annual reliability indexes for SLS. It was verified that the effect of load trains and the allowable stress significantly reduce the reliability index obtained for Brazilian standard. The service limit state equations are particularly sensitive to load trains, allowable stress and prestress losses, as well as their respective distributions.
DOI: 10.6084/m9.figshare.14307222.v1
title: Port structures - the distribution of forces on infrastructure due to mooring and berthing of vessels

description: ABSTRACT This work presents a study on the project actions required for the design and analysis of port structures, with regard to the impacts of mooring and berthing of vessels. This study sought to conduct a literature review, with emphasis on technical standards and codes, encompassing both national and international publications, including the Brazilian Standard NBR 9782/1987, the British Standard BS 6349, and the German Standard EAU 2004, in addition to the recommendations of the Permanent International Association of Navigation Congresses (PIANC 2002), and those of Jayme Mason (1982) in “Port Works”. The design procedures proposed by these different references regarding the computation of forces induced by mooring and berthing of vessels were evaluated in this work. Additionally, a case study of a port’s substructure was carried out, and a comparative analysis of the results, obtained with each recommendation of the aforementioned publications, was performed. The results showed a remarkable dispersion, revealing that the standards used strongly influence the design loads of port structures.
DOI: 10.6084/m9.figshare.14307221.v1
title: Factors influencing ultrasonic pulse velocity in concrete

description: Abstract The hydration process of Portland cement triggers reactions of stabilization of minerals from the contact of the clinker with water, which is the Hydrated Calcium Silicate (C-S-H), the Etringite (3CaO.Al2O3.3CaSO4.32H2O) and the Portlandite (Ca(OH)2). In order to understand the effects of the evolution of hydration in cement, it is possible to apply non-destructive tests. In this context, the objective of this work is to evaluate the influence of the type of cement, the curing age, of the format and humidity of the test specimens of concrete in the ultrasonic pulse velocity (UPV). In order to do that, 36 cylindrical test specimens (10 x 20 cm) and 9 cubic ones with 25 cm of edges, with mix proportion of 1:2,7:3,2 (cement/sand/gravel), water/cement ratio of 0.58 and three types of Portland cement (CP II-Z-32, CP IV-32 RS and CP V-ARI) were molded. With data obtained it was possible to correlate the increase of concrete strength along time (at ages of 7, 14, 28, 70 and 91 days) with the increase of the ultrasonic pulse velocity. Besides, it was possible to prove the direct influence of the concrete moisture and of the degree of hydration in the UPV. The shape of the test specimen generally had no influence on the results, except in the case of cement CP V ARI.
DOI: 10.6084/m9.figshare.14307218.v1
title: Analysis of soil-structure interaction in buildings with deep foundation

description: Abstract In this paper it is presented how the influence of soil-structure interaction (SSI) interferes on reinforced concrete structures in small buildings with deep foundations, with the objective of analyzing the influence of SSI on the loads and repressions, global stability and costs of materials. The analysis were based on numerical-computational simulations of a commercial building using CAD/TQS commercial software. The building was simulated with 4, 6 and 8 floors with 3 different profiles of soils, generating 8 case studies. When considering SSI, the loads and repressions did not present significant variations and the parameters of global instability were within the normative recommendations. Among the variables analyzed, the material cost of the structure was the least affected item with the SSI consideration.
DOI: 10.6084/m9.figshare.14307216.v1
title: Concrete crack repair analysis with metakaolin-based geopolymer cement

description: Abstract Among the advances in the use of geopolymer cements is their use as repair materials in concrete structures. The objective of this work was to use a geopolymer cement to repair cracks in concrete specimens, observing its mechanical performance and fracture modes. Cubic test specimens were produced and two types of cracks were evaluated as variables. Cracks were induced by steel sheets during concreting. The geopolymer cement paste and an epoxy adhesive, as reference, were used for the repairs. The results showed a 13% decrease in compressive strength for unrepaired concrete, and 3.7% in concrete repaired with geopolymer. The binder presented mechanical performance similar to that of the epoxy resin regarding crack recovery. In conclusion, repairs made with geopolymer cement are a viable and efficient means of crack recovery.
DOI: 10.6084/m9.figshare.14307213.v1
title: Proposal of a simplified criterion to estimate second order global effects in reinforced concrete buildings

description: Abstract This work proposes a new simplified parameter for the calculation of second order global effects, based on the Galerkin’s Method by Weighted Residuals. The proposed criterion was analysed based on 21 planar frames associated with shear wall, reaching results that present satisfactory accuracy compared to the second order global analysis, even for cases where the γz coefficient is greater than 1.30.
DOI: 10.6084/m9.figshare.14307212.v1
title: Statistical analysis of second order effects variation with the stories height of reinforced concrete buildings

description: Abstract In this paper the simplified method to evaluate final efforts using γ z coefficient is studied considering the variation of the second order effects with the height of the buildings. With this purpose, several reinforced concrete buildings of medium height are analyzed in first and second order using ANSYS software. Initially, it was checked that the (z coefficient should be used as magnifier of first order moments to evaluate final second order moments. Therefore, the study is developed considering the relation (final second order moments/ first order moments), calculated for each story of the structures. This moments relation is called magnifier of first order moments, "γ", and, in the ideal situation, it must coincide with the γ z value. However, it is observed that the reason γ /γ z varies with the height of the buildings. Furthermore, using an statistical analysis, it was checked that γ /γ z relation is generally lower than 1.05 and varies significantly in accordance with the considered building and with the presence or not of symmetry in the structure.
DOI: 10.6084/m9.figshare.14307209.v1
title: The influence of connecting pile cap-column in the mechanisms of break in the two pile caps

description: Abstract The paper analyzes the two pile caps with partially embedded socket and subject a center load. Three models were experimentally tested, varying the type of conformation of the column and walls of the socket, with a smooth, the other rough, and a monolithic two pile cap, used for reference. The roughening of the column-socket interface was examined with the aim of verifying the difference of the distribution of compressive and tensile stresses in the strut an tie model used for design. The experimental test to show that the two pile caps with conformation rough of the column and walls of the socket, support more load in comparison with two pile caps with smooth of the column and walls of the socket. Both however underperformed the monolithic two pile cap, with values of 66% and 36% respectively.
DOI: 10.6084/m9.figshare.14307207.v1
title: Setting process on mortars containing sugarcane bagasse ash

description: Abstract This paper presents an experimental study of the effect of partially replace of fine aggregate by sugarcane bagasse ash (CBA) in mortar mixtures in cement reactivity at early ages. The setting times and the initial development of the ultrasonic velocity for mortars produced at various water/cement ratios were evaluated. The objective of this study was to characterize the effects of the partial replacement of fine aggregate by sugarcane bagasse ash in the initial process of cement hydration. Therefore, the CBA used in this study went through different beneficiation processes, by grinding, reburning and sieving, with the objective of improve its features. The results suggest the viability of CBA use to accelerate cement hydration at early ages, with also an observed higher compressive strength.
DOI: 10.6084/m9.figshare.14307206.v1
title: Filter paper method to determine the water retention curves for mortar and cement samples

description: Abstract This study deals with the application of the filter paper method to determine water retention curves for mortar and concrete samples. A water retention curve exhibits the relationship between water content and energy state in interstitial water, normally expressed as a negative value when compare to normal conditions of temperature and pressure, being referred to as suction. Considering the water retention curve as a basic characterization tool for unsaturated soils, its usage in the engineering field concerning most of the construction materials remains as a pending task. However, stating that not only permeability, but also the water retention curve performs a significant role for water and soluble substances flow through a material's pores makes this observation essential for life-span estimation in cases like reinforced-concrete structures. This research paper offers results for water retention curves obtained in mortar and concrete samples. The experimental curves went through a fitting adjustment process using Van Genutchen's [1] model, showing consistency with the obtained results. Furthermore, the water/cement mix ratio does not indicate or suggest a direct influence for water retention curves.
DOI: 10.6084/m9.figshare.14307201.v1
title: Ultrasonic assessment and finite element modelling of thermo-mechanical damage in mortar

description: ABSTRACT Experiments were conducted to evaluate degradation of mechanical properties in mortar specimens subjected to thermal and mechanical loading. Ultrasonic pulse velocity was used to assess changes in the microstructure of the specimens due to thermal and mechanical loads applied separately. Both longitudinal and transverse waves were used. At first the specimens were tested in the undamaged stage, and then they were also tested after their exposure to a non-uniform thermal load only, finally, mechanical loading was applied until peak load. A finite element model was used in the dynamic simulation of pulses propagation. Results showed that mortar mix with a larger proportion of coarser aggregates is more sensitive to mechanical loading after exposure to heat than mortar with lesser and smaller aggregate contents. Mortar mix design with less and finer aggregate did not show a reduction in the pulse velocity as intense as the mortar with more coarse aggregate, which indicates a less severe diffuse microcracking.
DOI: 10.6084/m9.figshare.14307200.v1
title: Ultra High-Performance Fiber-Reinforced Concrete (UHPFRC): a review of material properties and design procedures

description: ABSTRACT This paper does a review of the recent achievements on the knowledge of UHPFRC properties and in the development of design procedures. UHPFRC is defined as a new material, with unique properties (high ductility, low permeability, very high strength capacity in compression, higher toughness) in comparison to conventional concrete. It is important to know both material and mechanical properties to fully take advantage of its outstanding properties for structural applications. However, since this is a new material, the current design codes are not well suited and should be reviewed before being applied to UHPFRC. In the first part, the following material properties are addressed: hydration process; permeability; fibers role; mix design; fiber-matrix bond properties workability; mixing procedure; and curing. In the second part, the mechanical properties of the material are discussed, together with some design recommendations. The aspects herein examined are: size effect; compressive and flexural strength; tensile stress-strain relation; shear and punching shear capacity; creep and shrinkage; fracture energy; steel bars anchorage and adherence. Besides, the tensile mechanical characterization is described using inverse analysis based on bending tests data. In the last part, material behavior at high temperature is discussed, including physical-chemical transformations of the concrete, spalling effect, and transient creep. In the latter case, a new Load Induced Thermal Strain (LITS) semi-empirical model is described and compared with UHPC experimental results.
DOI: 10.6084/m9.figshare.14307197.v1
title: Adherence between steel bars and lightweight concrete with EPS beads

description: Abstract This paper describes the adherence behavior of a structural lightweight concrete with EPS beads (SLCEB) in a monotonic loading, based in a bibliographic review and in pull-out tests. The results of these SLCEB tests were compared with those of an ordinary concrete (OC) and with the values based in indications of the Brazilian code ABNT NBR 6118:2014 - Design of concrete structures. The pull-out tests of two batches of SLCEB and one of OC were analyzed, in a total of 60 tests. Mechanical characteristics were determined too, such as: compressive strength and tensile strength in split cylinder test. The calculated results according to the above mentioned standard were very different from those obtained in the tests, indicating that the theoretical values are more conservative than the experimental ones. It was also verified that it is possible to use SLCEB in structures with respect to the adequate adherence of reinforcement in the concrete.