Search Results (33)

This research suggested natural hemp fiber-reinforced ropes (FRR) polymer usage to reinforce recycled aggregate square concrete columns that contain fired-clay solid brick aggregates in order to reduce the high costs associated with synthetic fiber-reinforced polymers (FRPs). A total of 24 square columns of concrete were fabricated to conduct this study. The samples were tested under a monotonic axial compression load. The variables of interest were the strength of unconfined concrete and the number of FRR layers. According to the results, the strengthened specimens demonstrated an increased compressive strength and ductility. Notably, the specimens with the smallest unconfined strength demonstrated the largest improvement in compressive strength and ductility. Particularly, the compressive strength and strain were enhanced by up to 181% and 564%, respectively. In order to predict the ultimate confined compressive stress and strain, this study investigated a number of analytical stress–strain models. A comparison of experimental and theoretical findings deduced that only a limited number of strength models resulted in close predictions, whereas an even larger scatter was observed for strain prediction. Machine learning was employed by using neural networks to predict the compressive strength. A dataset comprising 142 specimens strengthened with hemp FRP was extracted from the literature. The neural network was trained on the extracted dataset, and its performance was evaluated for the experimental results of this study, which demonstrated a close agreement. Full article

Channel steel-reinforced brick column technology has gained significant popularity in rural China due to its convenience and cost effectiveness. However, current research on channel steel reinforcement is sparse, and engineering applications often rely solely on construction experience. This reliance leads to significant construction errors, inconsistent reinforcement effects, and, in some cases, tragedies such as the collapse of Changsha’s “4.29” self-built houses. Therefore, in this paper, experimental and simulation studies on brick columns reinforced with external channel steel were conducted, and the results show that channel steel reinforcement can significantly enhance the axial load capacity of brick columns. However, increased initial stress levels and height-to-thickness ratios substantially reduce the reinforcement effect. Under axial pressure, the outer channel steel fails mainly through bending and buckling instability. Still, due to its good ductility, its failure occurs later than the brick column after being restrained by sufficient wall screws. Based on the experimental and simulation results, a method for calculating the axial compressive bearing capacity of the reinforced column is proposed, providing theoretical support and engineering guidance for applying this reinforcement method. Full article

To improve the out-of-plane collaborative performance of timber frames and walls, a metal connector is proposed and designed. A finite element model of the wall is established, and the composite block damage criteria and surface contact behavior are validated. Additionally, one group without metal connectors and three groups with different numbers of metal connectors placed at various positions in traditional residential wall models are established. Using static loading simulation, the influence of different numbers of metal connectors on the out-of-plane damage patterns, deformation characteristics, and shear force distribution is analyzed. The study reveals that top metal connectors significantly reduce the out-of-plane displacement of the top wall by up to 84.6%. Metal connectors have a significant impact on the deformation capacity of brick walls, with a maximum enhancement of 65.3%. The metal connectors in the middle and lower parts transfer the wall loads to the columns, increasing the horizontal shear at the column head by approximately 7%. The connectors in the middle and lower parts effectively improve the collaborative performance of brick walls and wooden frames. Full article

Kaolinite-rich soils were used to prepare zeolite-based composites via alkaline activation. The porous material was characterized by conducting XRD and microporosity measurements, as well as ESEM microscopy. The Weber and Morris (W-M) model was used for studying adsorption kinetics of radioactive cations on synthesized alkali-activated material. These investigations evidenced the effects of pore structure and the importance of the intrinsic characteristics of hydrated cations (ionic potential; hydrated radius; B-viscosity parameter; molar Gibbs energy of hydration of cation) on W-M kinetic rate constants. The application of diffusion-based models permitted us to assess the key diffusion parameters controlling successive diffusion regimes, and to reveal strong contributions of surface diffusion to adsorption kinetics during the course of the second and third kinetics stages of the W-M model. The magnitude of the surface diffusion coefficient was related to the capacity of hydrated cationic species to lose water molecules when penetrating brick pores. The HSDM model were tested for predicting radionuclide adsorption in a fixed-bed column. A breakthrough curve simulation indicated the predominance of the surface diffusion regime, which was in agreement with mathematical analysis of (batch) adsorption kinetics data. Ionic diffusion was linked to the characteristics of capillary porosity and connectivity of capillary pores in the composite, suggesting the generation of hydrated nuclides and their immobilization in the form of outer-sphere complexes. Full article

Through low-cycle reciprocating tests on 11 masonry wall specimens strengthened using reinforced-concrete–masonry composite columns, the effects of the position of the composite column, height-to-width ratio, column reinforcement ratio, and axial load ratio on their load-carrying capacity, stiffness, ductility, and energy dissipation capacity were investigated. It was experimentally found that, by strengthening brick walls with RC–masonry composite columns, the concrete and masonry parts can work together effectively, the failure mode shifts from shear to flexural failure, and the strengthened walls exhibit improved bearing capacity, ductility, and energy dissipation performance compared to unstrengthened masonry walls. It is suggested the composite columns can be placed at the ends of the wall if a strengthening measure is required. For walls with height-to-width ratios greater than 1, placing composite columns in the middle of a wall has little effect on the bearing capacity and stiffness of the wall but can improve the ductility of the wall. The height-to-width ratio is a primary factor influencing the structural performance of masonry walls strengthened using composite columns. A smaller height-to-width ratio leads to higher load-carrying capacity and stiffness but may result in reduced ductility. In comparison, the impact of the column reinforcement ratio and axial load ratio is relatively weaker. The flexural capacity of the masonry wall after strengthening can be obtained using the calculation method for concrete members subjected to a combined action of flexure and compression, in which the compressive strength of the masonry is considered. Full article

Based on the three-dimensional (3D) steady-state CFD numerical simulations conducted previously on an industrial Kalugin top combustion hot blast stove, a two-dimensional (2D) transient CFD numerical model for a single channel (hole) of a column of checker bricks in the regenerator of the same hot stove was established in the present work. The average mass flowrate and temperature of the flue gas flowing into the checker brick holes during the combustion period predicted by the 3D model were used as the inlet boundary conditions of the 2D model. Inside the hole of the checker bricks, processes of fluid flow and heat transfer of the flue gas during the combustion period and those of cold air during the hot-air-supply period were simulated using the 2D model for multiple operation cycles (combustion and hot-air-supply periods) of the hot stove, enabling rapid predictions of hot-air temperature under different operating conditions. The simulation results show that when the fuel gas flowrate and air consumption coefficient during the combustion period are controlled within the range of 80,000–100,000 Nm³/h and 1.02–1.28, respectively, a hot-air temperature in the range from 1273 °C to 1295 °C can be obtained during the hot-air-supply period. Applying this optimized operating condition to the industrial hot stove investigated in this study can achieve significant effects of reducing fuel gas flowrate by 8.6% and increasing hot-air temperature by 32 °C. In addition, a regression analysis on the numerical simulation results and the data measured from the industrial hot stove yields a roughly linear relationship between the dome temperature during the combustion period and the hot-air temperature during the hot-air-supply period, that is, the hot-air temperature would be increased by about 16 °C for every increment of 10 °C in the dome temperature, for instance. Therefore, the influences of the operating parameters on heat transfer characteristics in the regenerator and on hot-air temperature obtained in the present work provide a useful reference for guiding the hot stove operation optimization to achieve significant energy saving and emission reduction through facilitating more efficient combustion to minimize fuel gas consumption in steel plants. Full article

An experimental investigation on partially PBO (short of Polyparaphenylenebenzobisthiazole) FRCM (Fiber Reinforced Cementitious Mortar) confined clay brick masonry columns has been conducted. Ten small-scale specimens measuring 445 mm high with a square cross-section of the 250 mm side have been tested under monotonic axial loading until collapse. Two columns were unconfined, while the remaining ones were confined with single-layer PBO FRCM jackets varying the geometric configuration along their height. The vertical spacing ratio sf’/sf, being sf’ and sf the center-to-center and the net spacings between two consecutive jackets, respectively, was considered as the key parameter of the confinement configuration. The failure modes, stress–strain curves and peak axial stress and strain values are reported. The experimental results have been compared to the predictions of models found in the Italian guidelines CNR DT 215/2018 and the American ACI 549-R20 standards. The main aspects analyzed involved (i) the evaluation of the effectiveness of partial confinement on the mechanical response of columns, (ii) the definition of the mechanical and geometrical parameters that influence the structural response of partially confined columns, and (iii) the development of appropriate analytical models for the prediction of the resisting capacity of masonry columns partially confined with PBO FRCM. Full article

Damage to adobe constructions might occur due to a long wall and a lack of effective restraint in the middle of the wall, causing it to collapse under an earthquake. Aiming at these problems, a technology for improving the seismic performance of a modified adobe-brick-masonry composite wall with a wooden-construction center column is proposed. It uses modified mud, a wooden center column, steel-wire mesh, and nylon ropes to reinforce the wall. On this basis, four specimens of composite wall and one specimen of modified adobe wall were subjected to proposed quasistatic, cyclic in-plane loading tests to study their failure modes and seismic performance indicators. The results show that the failure modes of all walls were shear failure. The difference is that the modified adobe wall had horizontal cracks in the middle, whereas the composite walls were largely intact. Moreover, the composite walls relied on the modified mud to improve the seismic bearing capacity of each wall. They relied on the center column and the tie materials to form a second line of defense that would increase the wall ductility and collapse residual area. As a result, the phenomenon that caused wall damage and stiffness degradation was lessened. Full article

Half of global material consumption involves mineral material. The circularity is still low so that the enhanced use of secondary building material is required to close loops. Three different secondary building materials are discussed based on exemplary research results: construction and demolition waste (C&D waste), soil-like material, and incineration bottom ash (IBA). Focus was placed on the environmental compatibility of the materials examined mainly by standardized leaching tests. C&D waste was investigated after a wet treatment using a jigging machine, and soil-like material and IBA were characterized with respect to their material composition. Their environmental compatibilities in particular were studied using standard leaching tests (batch tests and column tests). It was concluded that soil-like material can mostly be utilized even when the precautionary limit values set are exceeded by a factor of less than two. For C&D waste, the fine fraction below 2 mm and the content of brick material is problematic. IBA fulfills quality level “HMVA-2” following German regulations. Improved levels of utilization might be achievable with better treatment technologies. Full article

A common practice in the construction of residential and commercial buildings in Saudi Arabia is to insulate the outer walls and windows only. Other building components such as the roof, columns and slabs, and doors are usually neglected. Moreover, vital components such as the roof and windows are especially neglected in commercially built residential and commercial buildings. The aim of this study is to put this common impression and practice to the test by quantifying the contribution of every building component to the overall air-conditioning load of the building. The hypothesis evaluated in this paper is that despite the common practices, there could be an optimum selection of insulators for the building components that yields the lowest energy consumption and maximum savings not only in energy costs but also installation costs. The required air-conditioning load is determined using manual calculations and the HAP software package for 1022 possible configurations. The findings of the analysis point to the importance of the roof, as it is the major contributor to the thermal load, followed closely by columns and slabs, with 44.2% of the overall cooling load. It is found that a single wall consisting of 2 cm of cement plaster, 20 cm of cement–polyurethane brick, and 2 cm of cement plaster is less expensive and has higher thermal resistance than any of the more expensive double walls. The study found one scenario of possible configurations with the optimized selection of building materials and their insulation materials that provides the most effective insulation at the lowest cost. Full article

The higher the process efficiency, the lower the fuel consumption, and the less impact carbon emissions have on the environment. The flow characteristics around brick settings are an important field of investigation to acquire control over the energy intake and production process. The current work is a numerical CFD investigation to demonstrate fluid flow characterization inside the cooling zone in a brick tunnel kiln for lattice settings (the number of bricks in each layer is identical). Four different lattice settings were examined, and three were validated with published experimental data (settings 1, 2 and 3). In the current study, the BSL κ-ω turbulent model agrees well with the published experimental results. The numerical investigation presents the flow characteristics through four different lattice brick settings (e.g., velocity vectors, velocity contours and streamlines) that could not be measured experimentally. The investigation also looks at the flow zones of the vortex formation upstream, downstream and through the brick column. It was discovered that for settings 1 and 11, the quick air flow in the wall channels is much greater than in the column channels. Setting 3 has a larger vortex formation region, whereas setting 1 has a weaker vortex than the other settings. The cooling of the lattice bricks in Setting 3 is superior to the cooling in the other settings. Full article

The “Caliphal City of Medina Azahara” was built in 936–937 CE or 940–941 CE (depending on the source) by the first Caliph of al-Andalus Abd al-Rahman III, being recently inscribed (2018) on the UNESCO World Heritage List. The abandonment and destruction of the city have been traditionally related to the civil war (“fitna”) that started between 1009 and 1010 CE. However, we cannot rule out other causes for the rapid depopulation and plundering of the city just a few decades after its foundation. The archaeoseismological study provides the first clues on the possible role played by an earthquake in the sudden abandonment and ruin of the city. Eleven different types of Earthquake Archaeological Effects (EAEs) have been identified, such as dropped key stones in arches, tilted walls, conjugated fractures in brick-made walls, conjugated fractures and folds in regular pavements and dipping broken corners in columns, among others. Besides that, 163 structural measures on EAEs were surveyed resulting in a mean ground movement direction of N140°–160° E. This geological structural analysis clearly indicates a building-oriented damage, which can be reasonably attributed to an earthquake that devastated Medina Azahara during the 11st or 12th centuries CE. If this were the case, two strong earthquakes (≥VIII MSK/EMS) occurred in 1024–1025 CE and 1169–1170 CE could be the suspected causative events of the damage and destruction of the city. Full article

Incorporating geopolymeric recycled brick aggregate concrete into steel tubes provides a promising solution to reduce environmental impact of construction and demolition waste. In this paper, geopolymeric recycled brick aggregate concrete-filled steel tubular column (GRBACFST) was developed to improve the environmental sustainability of composite column. Considering the replacement ratio of recycled brick aggregate (RBA), the thickness of the steel tube, type of cementitious materials and the axial compression ratio as the variation parameters, experimental research was performed to explore the cyclic behavior of GRBACFST columns, including the failure mode, bearing capacity, hysteresis curve, ductility and degradation characteristics. Results demonstrated that the failure of GRBACFST columns occurred in the region at column bottom, with the bulge of steel tube and crush of geopolymeric recycled brick aggregate concrete. The proposed GRBACFST columns exhibited favorable hysteretic behaviors with desired bearing capacity, excellent ductility, and energy dissipation behavior, which were enhanced by the increased thickness of the steel tube. The bearing capacity and ductility were reduced with the increase of axial compression ratio, while enhanced with thicker steel tube. Moreover, the degradation of stiffness and strength was more obvious under larger axial compression ratio. The increase of replacement ratio of RBA caused a significant reduction of bearing capacity, while it had few effect on the hysteretic index. It was concluded that the hysteretic behavior of proposed GRBACFST column was not sensitive to the types of cementitious material and geopolymers could serve as an eco-friendly binder for concrete. Full article

An earthquake of magnitude 6.4 occurred in Yangbi County, Yunnan Province on 21 May 2021, with a focal depth of 8 km, and strong ground motion with vertical components was monitored by Yangbi station (53YBX). A total of 14,122 houses were damaged in Yangbi in the earthquake, and 232 of them collapsed. Vertical components of ground motions have been gained more attention for its effect on structure’s seismic response in epicenter or near-fault regions at present. Taking the three earthquake ground motions of Yangbi, Chi-Chi, and Loma Prieta as inputs, and modeling based on Perform-3D, this research carried out the seismic dynamic time history analysis of an RC (reinforced concrete) frame structure and a brick-concrete structure under both horizontal and vertical working conditions. The results showed that vertical components of the three ground motions had no evident impact on the top horizontal displacement and acceleration of the two types of structures. Among the three ground motions, the vertical component of Yangbi ground motion has largely influenced the top vertical displacement, acceleration, and axial force of the frame column bottom (or masonry wall bottom). The vertical component had different amplification effects on the axial pressure and the bending moment of a single column at the bottom of the RC frame structure, thus causing resonance amplification effect of the brick-concrete structure floors and amplifying the vertical acceleration of the top floor. In addition, it considerably increase the maximum axial tensile strain of masonry walls and the possibility of faster tensile failure of the brick-concrete structure. Influence of vertical ground motion on the bearing capacity of RC frame structure’s columns and the brick-concrete structure’s masonry walls should not be ignored. The results of the research may provide a reference for the earthquake-resistant design of building structures, especially the earthquake-resistant design considering the vertical seismic effect. Full article

Masonry wall is a key construction subsystem, but it embodies significant environmental and energy burdens within the life cycle of buildings. Soil-cement bricks and blocks stand as an alternative low-cost masonry material, but despite the widespread claim to be environmentally friendly, more systematic investigation is lacking. This study aimed to assess the life cycle environmental and energy performance of 1.0 m² of a soil-cement brick masonry wall from cradle-to-construction in terms of carbon, energy, and water footprints, and fossil and mineral resource use, as well as compare it with conventional technologies such as ceramic and concrete block masonries in Brazil. Results showed that raw materials are a major contribution to soil cement masonry walls, followed by the joints and links with columns, in which cement stands out among other inputs. Hydraulic pressing in brick production had a negligible burden increase compared with manual pressing. The PVA mortar joint outperformed the PVA glue one, whereas resin coating performed better than cement mortar. In comparison with ceramic and concrete masonry walls, the soil cement masonry presented overall better environmental and energy performance and was the least affected by the inclusion of finishing coating layers and transport of materials in the sensitivity analysis scenarios, although improved scenarios of conventional options could be competitive, e.g., ceramic masonry with blocks produced by firing reforested wood for the carbon footprint. Scale-up analysis revealed that widespread deployment of soil cement masonry in the built environment would substantially avoid environmental and energy burdens compared with conventional technologies. Full article