Revista de la Construcción. Journal of Construction

An experimental and numerical investigation on reinforced concrete beams damaged at different levels of shear damage and strengthening with CFRP sheets

2024-02-28T23:03:47+00:00

In this study, a series of investigations have been planned to examine the altered mechanical properties of reinforced concrete beams that have experienced different levels of shear damage under vertical loads, through the application of Carbon Fiber-Reinforced Polymer (CFRP) strengthening. Both experimental and numerical approaches will be utilized to analyze these effects comprehensively. Within the scope of this study, four reinforced concrete beams with rectangular cross-sections and inadequate shear strength were subjected to vertical loads. One of these beams was designated as the reference beam, while the other three beams were loaded to induce varying levels of damage, corresponding to 50%, 65%, and 85% of the reference beam's shear capacity. Subsequently, these beams were strengthening with CFRP strips at shear spans of 12.5/10 cm width and spacing. The experiments were then repeated with this strengthening. Models were created using the ABAQUS finite element program, considering support, load, and material conditions, to simulate the experiments accurately. At the conclusion of the study, the maximum load-carrying capacity obtained from the Finite Element Model (FEM) was found to be between 95% to 105% of the maximum experimental Load-Carrying Capacity (Pu). Additionally, the study demonstrated that the crack mechanisms occurring in the beams during the experiments were in perfect agreement with those predicted by the finite element analysis.

Compatibility study of sargassum-based aggregate in Portland cement-based cementitious matrix

2024-05-20T21:22:36+00:00

Presently, because of the mounting environmental concerns that the construction sector is responsible for, given its high demand for natural resources and energy, there has been a surge in interest among various research groups in developing environmentally friendly construction materials that can reduce energy consumption during the occupancy phase of a building project. Among the solutions that have gained prominence are plant-based concretes.

The present study examined the compatibility between a Portland cement-based matrix and a Sargassum-based aggregate (Sargassum fluitans) obtained from the Mexican Atlantic coast. The raw materials were subjected to a physical and chemical characterization test to achieve this. Subsequently, a series of treatments were applied to the aggregate, including immersion in Ca(OH)₂, boiling in NaOH, coating with solid paraffin, and hornification. Subsequently, the compatibility of the raw materials was assessed based on the heat of hydration rate and compressive strength of the samples, as well as microstructural tests on the cement paste, which identified by-products of OPC hydration.

The results show that the application of Ca(OH)₂ immersion treatments improves the compressive strength at 28 days of curing by approximately 15 % concerning the sample with untreated aggregate, reaching a strength of 21.2 MPa. Conversely, the NaOH, solid paraffin, and hornification treatments diminish the compatibility, leading to a decline in the composite strength capacity.

Thermal effects on the engineering behavior of sand-bentonite and zeolite-bentonite mixtures for nuclear waste repositories

2024-07-29T15:42:56+00:00

Bentonite/bentonite-containing mixtures are used as an impermeable engineering barrier and backfilling undergoes temperature and hydraulic changes over time. Soils around energy geo-structures should preserve their engineering characteristics under different thermal, mechanical, and hydraulic conditions. The present study reports the impact of temperature (25 and 80 °C) and temperature cycles on the hydraulic conductivity and volume deformation properties of compacted sand-bentonite and zeolite-bentonite mixtures. In addition, the effect of tincal, a boron mineral with high thermal resistance, on the behavior of these mixtures at high temperatures was investigated. The conventional test apparatuses were modified to perform consolidation and hydraulic conductivity tests at high temperature. The results have shown that the tincal additive had a negative effect by increasing the deformation. Moreover, high temperature caused irreversible contraction under the thermal cycle. An increase in temperature created an increase in hydraulic conductivity. However, tincal added mixtures were more hydraulically stable against high temperature.

Predicting the mechanical characterization of polymer hybrid fiber-reinforced concrete using linear regression analysis and various codes

2024-07-29T22:22:58+00:00

The current study examined the Mechanical Properties (MP) of the concrete with the addition of the hybrid fibers and acrylic polymer in various proportions. Additionally, the MP of the concrete are compared using linear regression analysis and various design codes. A total of 56 mixes were examined the MP of the concrete, also the 56 mixes are divided in the 8 groups. The main objectives of the study, examine the mechanical properties of the concrete, find out the optimum mix proportions, and compare the experimental results to the proposed results. Based on the experimental results, the hybrid fiber RC carried out better than the remaining mixes. The Flexural Strength (FS) of the concrete improved by 16.99%, 26.66%, 12.43%, 8.26%, 20.37%, 24.63%, 13.96%, and 7.97%, respectively, which is compared to the control mix. Also, the proposed methods help to predict the results of experimental methods. Based on the analytical study, the ACI code and linear regression analysis results are highly correlated compared to the remaining codes.

Investigation of the sufficiency of CBR method sections used in the design of mine haul roads with the mechanistic method

2024-07-29T23:43:47+00:00

Mine haul roads are one of the most critical components of mining operation sites, both in terms of vehicle operating conditions and costs and in terms of providing the stable rolling surface required for sustainable haulage. There are many methods to determine layer materials and thicknesses in a traditional mine haul road section consisting of sub-base, base, and surface layers. The "California Bearing Ratio (CBR) Cover Curve" method, which is simple and practical to apply, is a common method frequently preferred in the design of mine haulage roads. However, the CBR method has disadvantages, such as being empirical and ignoring the surface layer stiffness in the design. In this study, vertical strain values on the subgrade were obtained by mechanical analysis of the pavement sections recommended by the CBR method and having different subgrade CBR values, loading conditions, and surface layer stiffnesses. The obtained strain values were compared with the limit strain values given in the literature, and the sufficiency of the CBR method was analyzed based on different design parameters. The results obtained from the study show that the limit strain values exceeded in the sections recommended by the CBR method, depending on the increase in the subgrade CBR value and the wheel load values on the section. One of the most notable results of the current study is that the stiffness of the surface layer in direct contact with vehicle wheels is one of the most essential parameters in the design of mine haul roads. In mine haul roads where the surface layer rigidity is low or there is no surface layer, the sections recommended by the CBR method are insufficient, and it has been revealed that a high-rigidity unbound layer, bituminous surface layer, or rigid pavement should be used as the surface layer.

Incomplete-type welding imperfection on fatigue assessment of tubular T-joints

2024-05-20T10:19:35+00:00

T-joints are structural parts of tubular steel skeletal structural systems. The connection of these joints is assembled by seam-welding. The fatigue strength of the seam-welded T-joint is one of the most determinative factors for sustainable performance. Manufacturing-related incomplete-type welding imperfections affect this strength parameter. In this study, the influence of incomplete-type welding imperfection on the fatigue life of tubular T-joint is investigated for the different loading conditions with the equivalent structural stress-based approach. A total of 7 numerical models are established, including a reference model of a tubular T-joint and its variants with incomplete welding imperfections in the crown and saddle regions. Each numerical model is subjected to 14 static analyses including combinations of axial tension, in-plane bending, and out-of-plane bending loads. The results are evaluated in terms of fatigue life and the location of the damage. It is demonstrated that incomplete welding causes a decrease in the fatigue life and a change of location of the fatigue.

The structural performance of beam reinforced with steel bars and glass fiber reinforced polymer bars subjected to static and static cyclic loads

2024-02-27T18:11:59+00:00

Glass fiber reinforced polymer (GFRP) bar has recently emerged as a viable alternative solution to conventional steel bars due to its stronger corrosion resistance and lightweight nature. The mechanical properties of the GFRP bar exhibits superior tensile strength than the steel bar. Hence, an experimental study was carried out on the beam specimen of size 1000 mm X 150 mm X 200 mm replacing the traditional steel bars with GFRP bars. The study focuses on the short-term behavior of beam specimens subjected to static and static cyclic loads. A comparative analysis was conducted between the beam with GFRP bars and traditional steel reinforcement and their moment resisting parameters such as deflection, load-carrying capacity, strain distribution, failure mode, ductility and deformability factor under static load were measured. Also, comparison studies discussed the stiffness and energy dissipation capacity under static cyclic loading. Results concluded that the beam with GFRP bars has 13% higher load-carrying capacity and 17% higher deflection than the conventional steel bars reinforced beam in static loading condition. In static cyclic loading condition, comparatively the beam with GFRP bars shows 15% higher load-carrying capacity and 21% higher deflection than the beam with steel reinforcement. A greater number of cracks appeared in the beam with GFRP reinforcement than the conventional steel reinforcement specimen. Overall, the results concluded the performance of the specimens with GFRP bars is superior to the conventional reinforcement in the concrete specimens.

Investigation of compressive strength and flexural behavior of dissreinforced cementitious mortar: Experimental study, statistical analysis and optimization

2024-07-30T01:32:51+00:00

The current study uses an experimental approach combined with statistical analysis to investigate the effect of incorporating Diss fibers on the mechanical behavior of cementitious mortars. The primary goal of this research is to investigate and optimize the effects of various factors on the compressive strength and flexural behavior of cementitious composites reinforced with Diss fibers. These variables include fiber percentage, fiber length, sodium hydroxide (NaOH) solution concentration, and immersion time. Using a Box-Behnken design of experiments (L27), samples of composites consisting of diss plant fibers and a cement matrix were prepared in accordance with a reference mortar. The 30-day evaluation period included measurements of compressive strength, flexural strength, and dynamic modulus of elasticity. The results showed that incorporating a lower percentage of diss fiber resulted in an improvement in mechanical properties. Regression models were developed for all responses using the Response Surface Methodology, and the influence of each parameter on the models was determined using ANOVA analysis. Using a combined approach of RSM and the desirability function, optimal values (1% diss fiber, 10 mm length, 3% NaOH concentration, and 60 minutes of immersion time) were determined. These optimal values agreed well with the experimental results, with differences in compressive strength of 0.65%, flexural strength of 0.00%, and dynamic elastic modulus of -0.43%.

Effects of using pumice, lime and marble in stabilization of expansive soils

2024-02-27T18:50:27+00:00

Expansive soils can cause severe damage to infrastructure. Extensive studies have been carried out on the stabilization of clayey soils using lime. Recently, the effect of pozzolanic materials on stabilization expansive soils has gained the attention of researchers due to their high content of SiO₂ and Al₂O₃, which catalyze pozzolanic reactions. Turkey is rich in natural pozzolana, lime, and marble. However, few studies have been conducted to investigate the effect of adding natural pozzolana on the geotechnical properties of lime and marble-treated expansive soils. This study aims to fill that gap by conducting laboratory tests to examine the influence of pumice, lime, and marble, both individually and in combination, on the geotechnical characteristics of expansive soils. Pumice was added to soil in a range of 0%-25% with increments of 5%, whereas marble and lime are added to soil within the range of 0%-15% and 0%-8%, respectively. The study investigates consistency limits, compaction parameters, and swelling parameters. Results show that expansive soils can be successfully stabilized by combining pumice, marble, and lime.

Design for sustainability approach on material selection preferences of LEED certificated buildings

2024-01-18T19:40:13+00:00

Design for sustainability (D4S) has been developed to help companies enhance their product life cycle processes, starting from the materials used in their products, while considering environmental and social aspects. The Material and Resources criteria of LEED share a similar focus with D4S. This alignment allows for exploring the practical application of D4S principles in the built environment. This study investigates the material selection preferences within LEED-certified buildings in Türkiye, specifically focusing on Gold, Platinum, Silver, and Certified-rated New Construction buildings under LEED V4 and LEED 2009 certifications. Through statistical analyses, the study examines how sub-criteria impact certification levels and how impacted sub-criteria are affected by project characteristic critically and discusses these findings in the context of D4S criteria. The results highlight (1) distinctions among certifications, particularly in relation to regional materials, certified wood, sourcing of raw materials and construction and demolition waste management criteria, and (2) project characteristics have varying impacts on the LEED certification criteria that have impact on variation in certification types. These results are interpreted from a D4S perspective, underscoring the importance of prioritizing reuse, renewable energy, waste reduction, and considering user impacts. In conclusion, this study underscores areas that require improvement in building material selection practices when viewed through the D4S principles.

Behavior of high strength concrete encased steel composite short columns subjected to axial load

2024-02-27T19:06:22+00:00

Present-day high strength concrete (HSC) encased steel composite (ESC) columns play a significant role in the construction industry. ESC resists steel sections from corrosion and fire resistance, increasing the load-carrying capacity compared to conventional reinforced concrete columns. This study investigated the behaviour of high-strength concrete encased steel composite short columns subjected to axial load. This study included analytical, experimental and numerical studies. The main objectives of this study are the axial load-carrying capacity of columns, mode of failure, peak ductility and stiffness at yield and ultimate point. A total of three column specimens were chosen in this study: one is a strength concrete ESC column, the second one is a strength reinforced concrete column, and the final one is a steel column; all columns were designed with the Indian standard code. The experimental study was compared to the analytical and numerical analysis; analytical and numerical studies also help predict the experimental research. Analytical and numerical study results were highly correlated to the experimental test results.

Evaluation of irregular reinforced concrete buildings according to different soil classes

2024-05-20T09:55:47+00:00

Determining the performances of existing reinforced concrete (RC) buildings under seismic effect is an important issue in structural engineering in terms of preventing losses that may occur in future earthquakes. Especially, a more detailed study is required to determine the behaviors of irregular buildings. In this study, seismic performances of existing RC buildings that have A3 irregularity defined in the Turkish Building Earthquake Code-2018 are investigated by non-linear static analysis method. Floor plans, story heights, material properties and section details of the structural members are common for the 3 modelled buildings. SAP2000 finite elements software is utilized in computer analyses. Performance analyses are performed for two local soil classes. Plasticization regions and plastic hinge definitions that are effective in the determination of seismic performance are carried out for each structural member according to lumped plasticity model. As a result of the performance analysis, performances of the buildings in different soil classes are investigated. In addition, seismic performances of the buildings with different story numbers and building heights in the same soil class are also evaluated. Analysis results are comparatively presented according to different local soil classes and building heights and suggestions are proposed for future studies.

Axial compression behavior of fully encased composite columns reinforced with longitudinally in glass fiber reinforced polymer (GFRP) bars

2024-11-28T11:24:53+00:00

The current study investigated the axial compression behavior of fully encased composite columns (FECC) reinforced with glass fiber reinforced polymer (GFRP) bars. Totally three conventional FEC columns and three FEC columns with the addition of alkali resistant glass fiber (ARGF) made with High Strength Concrete (HSC) are tested under axial compression. The inclusion of ARGF enhances the adhesion between the concrete and the steel reinforcement in the FECC. This increased bond strength facilitates a more efficient transfer of stresses and strains, thereby improving the load-carrying capacity. The dimensions of the FEC columns are 150mm x 150mm x 1000mm, and the steel section is ISMB 50mm x 100mm. All columns were designed as per Indian Standard (IS). The main parameter was studied in axial load carrying capacity, axial-deformation response, failure mode, peak ductility, and stiffness. The experimental results of conventional FEC columns were compared to those of FEC columns with the addition of AFGR. The axial load-carrying capacity and stiffness increased by 3.77% and 32.27%, respectively, while ductility decreased by 15.46% compared to conventional FEC columns. The analytical study was conducted in all columns; the analytical results were agreed to the experimental results.

Investigation of numerical and experimental behavior of infill walls under out-of-plane impact load

2024-07-30T00:19:06+00:00

During earthquakes, infill walls (IW) frequently interact with the reinforced concrete (RC) frames that surround them, despite the fact that they are considered to be non-structural components. In the event that the in-plane and out-of-plane behaviors are mixed together, this interaction has the potential to result in a variety of failure scenarios. In order to develop effective strengthening solutions to prevent collapse and improve their performance in future earthquakes, as well as to reduce their seismic vulnerability, it is crucial to understand the out-of-plane non-linear behavior of IWs. For this reason, the contribution of infill panels should be taken into account in the structural response analysis of existing buildings.

The influence of IWs on the seismic performance of reinforced concrete structures is a complex issue. The justification for this is because the interaction between the IW and the frame system is still insufficiently understood. This study addresses the intricate topic already referenced. On January 24, 2020, a magnitude M_w 6.8 earthquake transpired in the middle of Sivrice (Elazig). Upon examination of the earthquake-affected structures, it is observed that the IWs are significantly compromised, and it is presumed that the dynamic loads exerted on the structure are predominantly mitigated by the IWs. This study examined the reaction of the IW subjected to out-of-plane dynamic loads. This study examined the performance of IWs under out-of-plane dynamic loads, considering variables such as plastered versus unplastered IWs, the size effect of the IW, and the presence or absence of a door gap. Experiments were conducted on the walls of two earthquake-damaged carcass structures, which were subsequently modeled and assessed using the ANSYS software, followed by verification. The displacement data on the wall's rear, resulting from the out-of-plane load applied to the walls, were acquired by image processing techniques utilizing a MATLAB.