Revista Tecnológica

POST-BUCKLING ANALYSIS ON CELLULAR STEEL PROFILE WITH TUBULAR FLANGES AXIALLY LOADED

2024-08-02T22:31:37+00:00

This work investigates the structural behavior of cellular metal profiles with tubular flanges axially loaded. The structural analysis aims to assess the load-carrying capacity of these profiles, as well as possible instabilities. Using numerical methods through ABAQUS software, 18 profiles with different geometric configurations were studied. Different strength classes for steel were also considered. The findings show that a thicker profile enhances resistance, on average, by 76,6%. Profiles with higher slenderness exhibit overall instability, whereas those with lower slenderness around the axis of greatest inertia show local instabilities. Furthermore, increasing the mechanical steel strength contributes to 21% gain, on average, in the profile's ultimate strength.

Seismic response control of a plane frame using viscous dampers

2024-08-02T22:27:45+00:00

This present study consists of comparing the dynamic response of a steel building modeled as a flat frame when subjected to a real seismic excitation, both in scenarios without control and with passive control. Passive control is implemented through an energy dissipation strategy using viscous dampers, devices added externally to the structure. The results show that viscous damping applied to the structure significantly reduces the dynamic response in terms of displacement, achieving a reduction of around 70% throughout the seismic event.

EFFECTS OF LOADING ON CONCRETE QUALITY THROUGH ULTRASOUND TESTING

2024-08-02T22:30:43+00:00

Considering the importance of non-destructive testing in inspecting existing structures, this study aims to analyze the effects of external loading on the quality of concrete using the ultrasonic pulse velocity (UPV) test. To this end, a multidirectional UPV measurement is proposed on concrete samples under compressive stresses, considering their porosity and anisotropy. Twenty cylindrical specimens measuring 10 × 20 cm (diameter × height) were made from low-strength concrete (< 20 MPa). Compressive strength (f_c), tensile strength (f_ct), porosity (P), and UPV were then measured in the direction of the height of the specimen and also radially, under increasing compressive stresses in this case. Scanning electron microscopy (SEM) was also carried out. The results (UPV = 3716.20 m/s) made it possible to classify the quality of the low-strength concrete (f_c = 17.48 MPa, f_ct = 1.65 MPa) as "good", which is attributed, among other things, to its high porosity (P = 6.73%) and quantity of macropores, confirmed via SEM. However, under increasing compressive loads, the curve fitting the data (R² = 79.42%) revealed a reduction in the UPV in the radial direction, significantly reducing the quality of the concrete.

A comparative study of standardized methods for calculating the resistance of concrete-filled steel tubes

2024-08-02T22:30:24+00:00

In concrete-filled steel tube (CFST) composite columns, the passive confinement effect provided by the steel tube to the concrete core is of high importance. In light of this, the present study aimed to compare, through numerical analyses, the compressive strength capacity of numerical models of concrete-filled tubular section pillars with the predictions of the main existing technical standards. To achieve this, initially, a numerical model was constructed and verified, followed by a parametric analysis involving 10 CFSTs. The parameters varied included the diameter and thickness of the circular profile, the steel ratio, and the unbraced length. It was observed that as the D/t ratio of CFSTs increased, there was a lower percentage divergence between the strengths of the analytical models and that of the numerical model. This was attributed to the reduction of the confinement effect caused by the increased D/t ratio. Some standards provided predictions of strength capacity higher than that of the numerical model, although the greatest discrepancy was only 7%.

POTENTIAL APPLICATION OF UHPC IN COMPOSITE STRUCTURES FOR WIND POWER GENERATION

2024-08-02T22:27:27+00:00

The significant growth in demand for renewable energy in recent years has posed a challenge to structural engineering due to the need for larger and more slender structures to increase generation capacity. Market demands have led to the replacement of steel towers and platforms with reinforced concrete structures, which can incorporate new advanced materials. This paper presents a literature review on the use of ultra-high-performance concrete in mixed structures for onshore and offshore wind energy generation systems. Initially, specific regulatory prescriptions for the use of reinforced concrete in offshore platforms are presented. The properties of ultra-high-performance concrete (UHPC) as well as its applications in energy generation structures are discussed. The results indicate that it is possible to reduce the passive reinforcement of reinforced concrete structures through the use of advanced cementitious materials, and that there is the possibility of applying these materials in steel-concrete composite elements.

AVALIAÇÃO DA RESISTÊNCIA AO ARRANCAMENTO DE PINOS ARTESANAIS EMBUTIDOS EM CRFA

2024-08-02T22:31:17+00:00

The fracture mechanics concept for predicting the concrete strength capacity under axial stud pull-out force only takes into account the influence of the conical area projection and the concrete tensile strength; therefore, the accuracy of the model only depends on the fit coefficient (k) of the model, obtained experimentally. This work presented experimental results of the strength capacity of isolated studs embedded in steel fiber concrete blocks to evaluate the accuracy of literature empirical models. The study parameters were the stud heads' thickness and the steel fiber's volumetric rates. The experimental results showed strength gains of around 50% and 60%, respectively, for 0.5% and 1.0% of fiber addition, for a concrete compressive strength of 25 MPa and a head thickness t_h > 5.0 mm. The comparison with the theoretical models proved to be very conservative, with a k value of less than 17, and more accurate with the effect of head stud thickness consideration.

ANALYSIS OF CONCRETE PROPERTIES USING IRON ORE TAILING

2024-08-02T22:29:32+00:00

This study evaluated the properties of concrete with partial replacement of fine aggregate with iron ore tailings (IOT) to contribute to sustainability in civil construction and reduce the environmental impact of mining. Specifically, the compressive strength (fc), modulus of elasticity (E), the real specific mass (ρ_real), water absorption (Abs), and voids index (i_vazios) of samples with IOT at different contents (30% and 50%) and ages (7, 28 and 150 days) were investigated. It was found that 30% IOT improves the fc by up to 50% after 150 days, while 50% IOT decreases it, suggesting that there is an optimum limit for substitution that benefits structural integrity. Incorporating IOT also reduced E and Abs in samples with 30% IOT, indicating that IOT can act efficiently as a filler up to this substitution level. The study suggests that IOT is a viable alternative that can reduce the extraction of natural resources, lower production costs, and contribute to the circular economy in construction, with the potential for significant changes in the consumption of conventional materials and the management of mining waste.

COMPARAÇÃO DOS PARÂMETROS DE MODELOS CONSTITUTIVOS MODIFICADOS DE CARREIRA E CHU PARA UHPC ATRAVÉS DE REGRESSÃO NÃO LINEAR

2024-08-14T11:50:27+00:00

The Carreira & Chu (1985) constitutive model, which describes the stress-strain behavior of concrete under simple compression, is widely employed in analyses of cementitious matrices due to its simplicity. However, this model has limitations when dealing with concretes and mortars containing fibers, as is the specific case with UHPC. To overcome these limitations, modifications to the model have been proposed by Ezeldin & Balaguru (1992) and by Mansur et al. (1999). This study aims for a computational approach using nonlinear regressions, developed in the R language, and Leverberg–Marquardt optimization for parameter adjustment for the compression behaveor of UHPC. The validation data were obtained from compression tests on UHPC with the addition of 1% and 2% metallic fibers. The models satisfactorily converged to the performed tests. The model by Mansur et al. (1999) stood out mainly in representing post-peak behaviors.

ANÁLISE NUMÉRICA DO COMPORTAMENTO À FLEXÃO DE PISOS MISTOS DE PEQUENA ALTURA COM INOVADORA CONEXÃO DE CISALHAMENTO

2024-08-02T22:30:06+00:00

Abstract: With globally established composite structures, space is now open for innovative composite structural elements, such as slim floor. This system consists of steel beams and concrete or composite slabs supported on the lower flange of the profiles, resulting in a reduction of the total floor height. A numerical study was conducted on two typologies of slim floors composed of steel profiles with openings in the web: the Shallow Cellular Composite Floor Beam (SCCFB) and the Composite Slim-Floor Beam (CoSFB). These typologies allow the use of an innovative shear connection, with steel bars and in-situ cast concrete passing through the profile openings. The objective was to evaluate the contribution of this shear connection to flexural behavior, concluding that the presence of bars increases the resistant capacity of the systems, and the larger the opening, the greater this capacity.

Português

2024-08-02T22:30:59+00:00

The objective of the present work was to compare the values of axial force resistant to compression calculations of encased composite columns, obtained using the calculation methodologies of ABNT NBR 8800:2008 and AISC: 360-22. Composite columns were initially used unpretentiously for fire situations in the 1940s, however, in the 1960s the first studies appeared on the use of this type of structure for High-rise buildings. In this sense, as tall buildings are not traditional in Brazil, the study calculated the value of the resistant axial force in the compression calculation of the fully encased composite pillar and the central metallic profile of the composite pillar, and compared the results. An example of a encased composite column was used for the study and the two different standards were applied to it, after which the results were compared. Although both standards use limit states for calculation, the results obtained by ABNT NBR 8800:2008 presented higher values than those obtained by AISC:360-22. In this way, the American standard presented more conservative values for calculating the resistant axial force.

DESIGN METHODS FOR RECYCLED AGGREGATE CONCRETE-FILLED STEEL TUBE (RACFST) STUB COLUMNS UNDER CONCENTRIC COMPRESSION

2024-08-02T22:26:48+00:00

The confinement of Recycled Aggregate Concrete (RAC) has become an interesting alternative for its application in structures due to its greater deformability and lower resistance. Recycled Aggregate Concrete-Filled Steel Tube (RACFST) is an economical alternative to Concrete-Filled Steel Tube (CFST), in addition to reducing environmental impact and consumption of natural resources. However, the existing recommendations refer to CFST columns, while there is currently only one design standard for RACFST columns. The aim of this study is to determine the applicability of standards and methods from the literature in RACFST column design. For this, seven standards for CFST, one for RACFST and four methods from the literature for RACFST were tested on 97 experimental results of short RACFST columns. All standards were found to be efficient in calculating the load-bearing of RACFST columns, with the RAC compressive strength being the main parameter differentiating the methods. The confinement effect is taken into account in the methods in different ways, which also affects the load-bearing capacity of the RACFST columns.

EVALUATION OF THE PROPERTIES OF FOAMED CELLULAR CONCRETE PRODUCED WITH PARCIAL REPLACEMENT OF CEMENT BY RICE HUSK ASH

2024-08-02T22:29:15+00:00

Portland cement is, by mass, the most consumed manufactured product on the planet and its industry is responsible for approximately 7% of the world's anthropogenic CO2 emissions. The manufacture of cement's main component, clinker, requires a great deal of energy consumption and fuel burning, which generates high pollutant emissions. The use of supplementary cementitious materials (SCM) as a partial substitute for cement is an effective alternative for reducing cement consumption. Residual ash from agricultural activities is a good alternative for SCMs, including rice husk ash (RHA). This research therefore studied the effects of introducing RHA on the properties of foam cellular concrete. Three concrete dosages were used: REF, RHA-10 and RHA-20, with 0%, 10% and 20% cement replacement by RHA, respectively, by mass. The mechanical performance after 7 days of curing indicates that concrete with RHA can be used for non-structural purposes, while the performance after 21 days indicates that the RHA-10 mix is suitable for use as lightweight structural concrete. The addition of ash reduced the concrete's water absorption rate.

EVALUATION OF CONFINED CONCRETE BEHAVIOR IN CONCRETE-FILLIED STEEL COLUMNS

2024-08-02T22:25:48+00:00

Concrete-filled steel columns stand out in the construction industry due to their advantages, such as high load-bearing capacity and deformation. This study aimed to investigate the behavior of concrete confinement in composite columns under different parametric conditions, using numerical simulations via the ABAQUS software. It was observed that confined concrete increases the compression strength of the column; however, this is accompanied by a loss of ductility as the strength of the concrete increases. It was also observed that columns with slimmer proportions tend to exhibit global instability before complete confinement of the concrete core occurs. These findings underscore the importance of considering such aspects in the design and sizing of composite columns to ensure the safety and efficiency of confined concrete structures.

NUMERICAL ANALYSIS OF THE BEHAVIOR OF CONCRETE-FILLED STEEL TUBES

2024-08-02T22:28:39+00:00

The use of concrete-filled steel tubes in civil construction offers significant advantages, such as increased strength, ductility, and energy absorption, compared to steel or reinforced concrete columns. This study aims to investigate the compressive behavior of concrete-filled rectangular composite columns. A finite element model was developed and validated using ABAQUS software. It was observed that parameters such as length and thickness of the tube, cross-sectional area, and concrete strength influence the resistance capacity. The results of the numerical models were compared with analytical models to verify the ultimate load. It was found that the normative models were conservative in predicting the resistance capacity of concrete-filled rectangular composite columns.

ANÁLISE NUMÉRICA DE CONEXÕES METÁLICAS EM ESTRUTURAS DE MADEIRA EM SITUAÇÃO DE INCÊNDIO

2024-08-02T22:27:08+00:00

Steel connections play a crucial role in load transmission and structural integrity in timber elements, as their behavior governs the overall structure's performance. At high temperatures, the mechanical properties of materials change and they lose strength. With the aim of investigating the behavior of steel connection devices used for connecting timber structural elements, this study conducts thermal numerical analyses, considering two types of connections: one composed of only steel dowels and bolts, and the second composed of dowels and a steel plate. The numerical analyses were performed using the ABAQUS computational package, considering the advanced calculation method proposed by EN 1995-1-2, and validated with results from experimental tests. A difference in behavior was observed between steel bolts and dowels, with the bolt head region showing a greater temperature increase than that found in connections using dowels due to direct exposure to flames. The charring rate determined by numerical analysis shows more conservative values than those found in the standard and in experimental tests used as a basis in this article.

ANALYSIS OF DESIGN MODELS FOR PARTIALLY ENCASED COMPOSITE COLUMNS

2024-08-02T22:26:29+00:00

New methodologies for producing composite columns have been the subject of recent research, such as recycled aggregates and steel fibers' incorporation into concrete. Not yet included in current standards, they need validation through design models. This work compared the experimental results of partially encased composite columns with steel fiber reinforced concrete and recycled aggregate concrete to the resistance according to the ABNT NBR 8800 (2008) and EN-1994-1-1 (2004). The design models yielded satisfactorily prediction for the resistance, with higher discrepancies for slender columns. Furthermore, the imperfection eccentricity and the second-order effects must be considered to obtain representative results.

CALIBRAÇÃO DOS PARÂMETROS DE PLASTICIDADE DANIFICADA DO CONCRETO PARA LAJES LISAS NO ABAQUS

2024-08-02T22:28:21+00:00

In this work, nonlinear finite element analyses were conducted to investigate the punching shear capacity of flat slabs. The analyses were conducted by calibrating the plasticity parameters of the Concrete Damaged Plasticity (CDP) model, present in ABAQUS, and then compared to the experimental results of slab-column joints with circular openings adjacent to the internal column. The calibration indicated the dependence of the models on some parameters, and also that the proposed models can appropriately predict the punching shear capacity of the slabs.

NUMERICAL SIMULATION OF THE BEHAVIOR OF COLD-FORMED SHEAR CONNECTORS

2024-08-02T22:26:06+00:00

The shear connector is a device applied to the steel-concrete interface of composite structural elements, with the function of transferring efforts between the steel element and the concrete element, and vice versa. The U shear connector made up of a cold-formed profile is a low-cost alternative connector, however, more studies to understand its mechanical behavior need to be developed. In this sense, this work aims to numerically simulate the mechanical behavior of U-shaped shear connectors consisting of a cold-formed profile. The numerical model developed was validated with experimental tests from the literature. The results obtained were satisfactory and consistent with the experimental results, indicating that the developed model is capable of simulating the behavior of U-shaped shear connectors with a cold-formed profile.

ESTUDO COMPARATIVO DO CUSTO DE VIGAS MISTAS DE AÇO-CONCRETO COM STUD BOLT E CONECTOR TRELIÇADO

2024-08-02T22:25:30+00:00

Steel-concrete composite beams are structural elements consisting of a reinforced concrete slab connected to a steel profile. The connection between these two elements is made using shear connectors. Much research has developed alternative connectors to the stud bolt that are low cost and guarantee good structural performance. Among them, the Truss-Type connector can be highlighted. The present work aims to compare the costs of applying stud bolt and Truss-Type connectors to composite beams. The formulations present in NBR 8800:2008 and in the study of Lima (2021) were used. Finally, the composition of inputs for each connector was prepared and, therefore, the unit cost of both was determined. It was found that the unit cost of the lattice connector was approximately 46% lower when compared to the stud bolt. Furthermore, the final cost of the lattice connectors for the structure was approximately 51% lower than stud bolts, representing a notable economic advantage.

INVESTIGAÇÃO DE COLUNAS TIPO DOUBLE-SKIN PREENCHIDAS COM CONCRETO

2024-08-02T22:25:11+00:00

This work investigates the performance of CFDST columns from the perspective of the formulation proposed by Castanheira (2021). These columns, composed of two concentric steel tubes (stainless and carbon) filled with concrete, represent an efficient solution, combining the strength of steel with the properties of concrete. The study focuses on the methodology developed by Castanheira (2021), applying it to studies by Rodrigues (2018) and Ribeiro (2023). In column design, it is necessary to consider parameters such as tube thickness, external and internal diameters, strength of the concrete and steel tubes. After a critical evaluation of the Castanheira (2021) proposed formulation in relation to the experimental and numerical results, it is highlighted that the authors' results are very close to the values of the proposed equation, however 1 in 5 answers proved to be unsafe. Indicating the need to define regions that require further studies, such as carrying out experimental and finite element tests for a deeper discussion of the behavior of CFDST columns and existing formulations in literature.

VIABILIDADE TÉCNICO-FINANCEIRA E EFICIÊNCIA CONSTRUTIVA DAS ESTRUTURAS MISTAS NA CONSTRUÇÃO CIVIL

2024-08-02T22:28:58+00:00

In civil engineering, steel and concrete composite structures represent a harmonious synergy that provides strength, durability, and efficient load distribution. Their structural performance ensures construction stability while enabling cost and time reduction, with significant material savings, making them an economical and innovative choice for various architectural and engineering projects. Additionally, the construction efficiency of these structures facilitates rapid execution, minimizing material waste and ensuring construction quality, representing a significant technological advancement in the civil engineering sector.

ANÁLISE DE SENSIBILIDADE DE VIGAS MISTAS DE AÇO E CONCRETO SUBMETIDAS A MOMENTO FLETOR NEGATIVO PARA MODELOS CONSTITUTIVOS DO AÇO

2024-08-02T22:28:03+00:00

Composite steel and concrete beams stand out as an efficient structural solution for multi-story buildings, contributing to the reduction of overall height and self-weight of the structure. Current research in this field predominantly relies on numerical modeling to enhance understanding. However, there exists a gap in sensitivity analysis for different constitutive models of the steel profile. This study aims to explore the predictive capability of four constitutive models for the steel profile of composite beams. The models will be evaluated through numerical simulations using the ABAQUS® program, considering experimental tests. The findings indicate that the assessed constitutive models demonstrate a strong predictive capacity for the real structural behavior.

EXPERIMENTAL INVESTIGATION ON THE DYNAMIC RESPONSE OF STEEL-CONCRETE BOX BEAMS FOR DIFFERENT FABRICATION PROCESS

2024-08-02T22:24:52+00:00

This study aims to compare results obtained via experimental tests and analytical method for the dynamic response (natural frequencies) of a steel hollow section beam for different concrete-filled configurations. Six different configurations are considered herein: steel hollow section beam with no concrete-filled; steel concrete-filled hollow beam with release agent applied on the interface steel-concrete; steel concrete-filled hollow beam without release agent applied on the interface steel-concrete; concrete-filled hollow beam with one rebar layer on the bottom side; concrete-filled hollow beam with two rebar layers on the bottom side; concrete-filled hollow beam with connected concrete slab. The results were presented in terms of the parameter named Frequency Response Function (FRF). It was seen that the results obtained via experimental tests and analytical formulation showed a good correlation between them. The results for the hollow steel-box beams with no concrete filled showed a significant different dynamic response in comparison with the other types of beams, as expected. All concrete filled beams presented similar results in terms of their dynamic responses.