Search Results (136)

This paper presents a dual-band shielding approach in which two concentric square rings, fabricated on a single 0.2 mm copper sheet, are embedded in the mortar joint of prefabricated concrete blocks. The outer ring targets n78 (design center 3.5 GHz) and the inner ring targets n79 (design center 4.7 GHz). Both rings are dimensioned from the effective wavelength inside the concrete medium (ε_r = 5.0): the outer ring has an outer side of 9.93 mm and the inner ring an outer side of 7.43 mm, with a 180° gap offset between the two elements to suppress inter-ring coupling. CST Microwave Studio simulations predicted two shielding peaks of 37.2 dB at 3.48 GHz and 35.8 dB at 4.72 GHz, with −10 dB bandwidths of 580 MHz and 490 MHz, respectively. Computer numerical control (CNC)-milled copper panels cast into ordinary Portland cement (OPC) concrete blocks achieved measured peak SE of 34.9 dB (n78) and 33.4 dB (n79), with bandwidths of 510 MHz and 420 MHz. The 2.3–2.4 dB shortfall relative to simulation is attributed to coupling-gap drift during milling and spacer-induced surface voids. A permittivity sweep from ε_r = 4.5 to 6.0 showed that peak SE remains above 30 dB throughout. Full article

Masonry retaining walls are widely used in mountainous regions but are susceptible to progressive internal damage under environmental and operational loads, which is often difficult to detect through conventional visual inspection. To address this problem, this study proposes a baseline-free vibration-based damage identification method for existing masonry retaining walls. The method combines impulse response function (IRF) estimation with wavelet packet decomposition (WPD) and introduces a scalar damage index, termed the energy ratio standard deviation (ERSD). Unlike conventional WPD energy ratio deviation (ERD) vectors, ERSD condenses multi-band energy redistribution into a single positive scalar for each sensor location, thereby facilitating spatial interpolation and field-level damage localization without modal extraction. The method was validated through four monthly impact hammer tests on a masonry retaining wall in Zhenjiang, China. The results show that non-zero ERD vectors indicate vibration energy redistribution between successive monitoring states, while the spatial peak of ERSD identifies the most likely damage zone. The ERSD maximum occurred at point 5 and was confirmed by post-test visual inspection, which revealed a local crack of approximately 0.8–1.2 mm in the adjacent mortar joint. To avoid overfitting with the limited four-test dataset, the temporal trend of ERSD was evaluated using a linear regression and finite-difference progression rates rather than a high-order polynomial. The proposed method provides a practical preliminary screening tool for field damage localization; however, its quantitative damage severity calibration requires further validation using controlled stiffness-reduction tests and environmental compensation models. Full article

This study experimentally investigates the structural behavior of hexagonal- and square-shaped composite specimens subjected to vertical compression, vertical tension, and diagonal tension loading. The specimens were fabricated using four- and six-layer alkali-resistant (AR) glass textile reinforcements embedded in a modified cementitious mortar via pull, pour, and roll manufacturing techniques. The mechanical performance of polyvinyl alcohol (PVA) fiber-reinforced composite connectors and steel clamp-type elements was also evaluated at the joints of hexagonal specimens under vertical tension and lateral shear loading. The results show that increasing the number of textile layers significantly enhances structural performance. A 50% increase in textile layers improved load-carrying capacity by up to 56% in compression, 104% in tension, and 216% in diagonal tension. Corresponding increases of approximately 20–42% in ductility and up to 266% in energy dissipation capacity were observed. No failure occurred in the connecting elements, confirming their adequate stiffness, strength, and ductility. In addition, validated three-dimensional finite element models were developed to simulate the response of the hexagonal specimens. Overall, the proposed system demonstrates strong potential for applications such as infill walls, cladding, and sandwich panels due to its favorable strength, ductility, and energy absorption capacity. Full article

The generation of slag from copper smelting is between 40 and 45 Mt per year. However, the utilisation of this material in large-scale applications remains limited. This study evaluates the combined use of copper slag as a fine natural aggregate substitute (50, 75, and 100%) and natural mordenite-type zeolite as a partial cement replacement (25, 40, and 55%) in the development of sustainable mortars. The samples were characterised using XRF, particle size distribution, and density analysis, and sixteen mixtures were produced. The consistency and water demand in fresh state, the flexural and compressive strength at 7 and 28 days, and the porosity measurements of the hardened mortars were analysed. The results demonstrate that zeolite significantly increases water demand, leading to higher porosity (27–34%) and reduced mechanical strength (14–31 MPa). Conversely, copper slag decreases the water-to-cement ratio and produces denser matrices with the lowest porosity values (8–13%), achieving compressive strengths at 28 days that are higher (53–58 MPa) than the reference mortar (50 MPa). In hybrid mixtures, slag partially mitigates the porosity increase induced by zeolite, revealing a favourable interaction between both materials. Mixtures containing 75–100% copper slag and 25% zeolite (MZ-8 and MZ-9) exhibited balanced porosity (18–21%) and mechanical performance (38–39 MPa), confirming their suitability for mortar applications. The findings demonstrate that the joint incorporation of copper slag and natural zeolite is a viable strategy for producing eco-efficient mortars while reducing clinker and natural aggregate consumption. Full article

The quality of interlayer bonding in roller-compacted concrete dam construction is significantly influenced by environmental factors, and traditional methods for determining initial and final setting are ill-suited for complex field conditions. Based on the Lower Kafue Hydropower Project in Zambia, a quality control method integrating maturity indicators and interlayer exposure time is proposed. Through designing and conducting field tests, roller-compacted concrete specimens were evaluated under varying exposure times (4–62 h) and interlayer treatment methods (cement slurry treatment, mortar treatment, no treatment, roughening, etc.). Based on a maturity calculation model, interlayer joints were classified into three categories—“hot joints,” “warm joints,” and “cold joints”—with corresponding evaluation criteria and treatment measures established. Experimental results indicate that shorter interlayer exposure time and lower maturity yield higher interlayer bond strength. Cement slurry treatment outperforms mortar treatment, while roughening further enhances bonding quality. A dynamic adjustment model based on monthly average temperatures effectively guides construction decisions under varying climatic conditions. Engineering applications demonstrate that this method enhances interlayer bonding quality and construction controllability, thereby ensuring the quality of interlayer pouring in roller-compacted concrete dams and improving the overall quality of such dams to meet design requirements. Full article

Acoustic emission (AE) is a vital non-destructive technique for monitoring damage in materials, yet its simulation via the Discrete Element Method (DEM) has historically been limited to material-scale analysis. This research presents a novel application of block-based DEM to simulate AE signals in masonry structures at the structural scale under quasi-static in-plane loading. Using a simplified micro-modeling approach, the study first validates the method by monitoring crack initiation and AE energy in single mortar bed joints under tensile and shear conditions. The methodology is then scaled to a large-scale masonry wall panel (1.835 × 1.170 × 0.15 m³) subjected to monotonic shear loading. A critical finding is the influence of local damping; a reduced damping ratio of 0.3 is recommended to preserve the kinetic energy necessary for capturing clear velocity signals. Numerical results show strong agreement with experimental force-displacement and cumulative AE energy curves, confirming the model’s robustness. Furthermore, frequency analysis of the simulated signals successfully distinguishes between tensile and shear failure modes. This study fills a significant gap in the literature by demonstrating that DEM is an effective predictive tool for structural-scale failure analysis and AE monitoring in heterogeneous masonry. Full article

An integrated rebar box connection is proposed for the horizontal joints of fully prefabricated composite walls to simplify joint detailing and reduce on-site wet construction. Experimental tests and numerical analyses were conducted to evaluate the behavior of this connection. The results show that both specimens exhibited shear-dominated failure. The box connection and horizontal joint did not experience obvious fracture or pull-out failure, although local cover spalling, mortar crushing, and connector deformation were observed, suggesting effective force transfer between the upper and lower wall panels under the tested conditions. Compared with the cyclically loaded specimen, the monotonically loaded specimen exhibited higher peak load and larger deformation capacity under monotonic loading, whereas the initial stiffness was similar. The numerical results agree reasonably well with the experimental responses. The parametric finite element analyses indicate that increasing the integrated rebar diameter, the longitudinal reinforcement ratio in the rib columns, the concrete grid strength, and the axial compression ratio improves the load-carrying capacity of the wall, although a higher axial compression ratio reduces ductility. The proposed connection shows promising potential for use in the horizontal joints of fully prefabricated composite walls, and further studies with additional specimens and comparative connection details are warranted. Full article

To investigate the mechanical performance and failure modes of Prestressed Concrete Cylinder Pipe (PCCP) bell-and-spigot joints under conditions such as differential settlement, this study conducted a full-scale rotation test on a DN1400 PCCP joint and established a three-dimensional non-linear finite element model using ABAQUS. The experimental results indicate that when the relative rotation angle reaches approximately 1.92°, the primary failure mode is the slipping of the rubber gasket from the spigot groove, leading to sealing failure. Meanwhile, the strains in the concrete, mortar coating, and prestressing wires at the joint increase significantly with the rotation angle. The finite element simulation results align well with the experimental data, with an average error of 1.88%. Based on the validated model, a parametric analysis was performed on PCCP joints with diameters ranging from 1400 mm to 4000 mm. The study determined the ultimate relative rotation angle for different diameters based on the concrete visible crack criterion and revealed a significant size effect, characterized by a decrease in the ultimate rotation angle with increasing pipe diameter. These findings provide a theoretical basis for the design, construction, and safety assessment of PCCP pipelines. Full article

This work experimentally examines the seismic performance of steel frames with masonry infill walls produced with geopolymer and traditional mortars under both rigid and flexible joint configurations. Four single-span specimens were evaluated on a uniaxial shake table utilizing eleven scaled earthquake records that represent both in-plane and out-of-plane excitations. Flexible joints markedly diminished acceleration requirements and enhanced deformation capacity in comparison to stiff systems. Rigid frames attained maximum accelerations of 1.82 ± 0.21 g, whilst flexible-joint specimens measured 1.15 ± 0.18 g; the associated lateral displacements were 6.8 ± 0.9 mm and 10.5 ± 1.1 mm, respectively. Geopolymer mortar improved interface adhesion and rigidity, elevating dominant frequencies in rigid systems by around 40% and fostering more ductile behavior in flexible structures. Frequency-domain analysis indicated that decreases in dominant frequency correlated with stiffness deterioration. Geopolymer–flexible systems yielded the minimal acceleration responses and displayed only negligible cracking, indicating enhanced seismic performance. Full article

Simulating damage phenomena in masonry structures remains a significant challenge because of the intricate and heterogeneous nature of this material. An accurate evaluation of fracture behavior is essential for assessing the bearing capacity of these structures, thereby mitigating dramatic failures. This paper proposes an innovative adaptive concurrent multiscale model for evaluating the bearing capacity of in-plane masonry structures under in-plane loadings. Developed within a Finite Element (FE) set, the proposed model employs a domain decomposition scheme to solve a combination of fine- and coarse-scale sub-models concurrently. In regions requiring less detail, the masonry is represented by homogeneous linear elastic macro-elements. The material properties for these macro-elements are derived through a first-order computational homogenization strategy. Conversely, in areas with higher resolution needs, the masonry is modeled by accurately depicting individual brick units and mortar joints. To capture strain localization effectively in these finer regions, a Phase Field Cohesive Zone Model (PF-CZM) formulation is employed as the fracture model. The adaptive nature derives from the fact that at the beginning of the analysis, the model is entirely composed of coarse regions. As nonlinear phenomena develop, these regions are progressively deactivated and replaced by finer regions. An activation criterion identifies damage-prone regions of the domain, thereby triggering the transition from macro to micro scales. The proposed model’s validity was assessed through multiscale numerical simulations applied to a targeted case study, with the results compared to those from a direct numerical simulation. The results confirm the effectiveness and accuracy of this innovative approach for analyzing masonry failure. Full article

The failure behaviour of historic unreinforced masonry (URM) structures is strongly influenced by the properties of bricks and mortar. Over time, degradation processes compromise these materials, with significant effect on structural response and safety. Nevertheless, deterioration effects on the nonlinear behaviour of masonry have been only marginally investigated. This study investigates the mechanical behaviour and failure mechanisms of historic brick masonry with weak and irregular mortar joints, representative of Mediterranean traditional constructions. An extensive experimental programme was conducted on mortars, historic clay bricks, prisms, wallets, and triplet specimens, complemented by in-situ flat jack tests. Results confirm the critical role of mortar quality and joint irregularities in reducing compressive and shear strength and in influencing deformation capacity of historic masonry. The experimental findings served as a basis for the calibration of a Finite Element Model (FEM), subsequently employed to gain deeper insight into the governing failure mechanisms in a real study case. A critical discussion of compression and shear failure criteria is presented, focusing on historic masonry. Experimental and analytical comparisons show major discrepancies in classical criteria, especially with degraded mortars. The study shows that in historic masonry with weak joints, failure is often governed by compression rather than shear. Full article

Identification of the strength characteristics of mortars in brick or stone masonry is crucial in the structural analysis of heritage buildings and selecting materials for their repairs and reconstruction. Non-destructive, minimally destructive, and minor-destructive tests have been developed to establish the strength of mortar in existing masonry. This paper presents strength tests on mortar samples extracted from bed joints of heritage buildings erected in the historic center of Cracow during the 19th and 20th centuries. The mortar samples were tested using the double-punch method, a minor-destructive technique especially useful for heritage structures where cutting out large masonry specimens is not possible due to conservation reasons. The impact of sample thickness and type of capping materials on the test results were analyzed in detail. Practical recommendations are also proposed for the procedure of the double-punch method in relation to historical mortars. Full article

This study aims to investigate the mechanical behavior and failure mechanisms of tunnel-type anchorages for suspension bridges under complex geological conditions, using the Wujiagang Yangtze River Bridge as a case study. A scaled physical model (1:40) was employed to systematically examine deformation patterns, stress transfer, and ultimate bearing capacity under incremental loading. Key results demonstrate a quasi-symmetrical “double-hump” deformation response under service load, with axial stress concentrated at the rear anchorage face. The critical safety threshold was identified at 9 times the design load (9P), beyond which plastic damage initiates. Uplift resistance was found to rely primarily on rear rock mass confinement, while sandstone interlayers and mortar joints showed negligible impacts on stability. These findings provide practical criteria for the design and safety assessment of tunnel anchorages in rock-dominated environments. Full article

The use of single-layer aerated concrete walls in residential construction has a tradition of over 60 years. Its main advantage is thermal insulation. It is the most advantageous among construction materials used for the construction of external walls. The possibility of modifying the dimensions of the blocks leads to meeting subsequent restrictive values of the heat transfer coefficient U. The high dimensional accuracy of the blocks allows the use of dry vertical joints and thin joints with a thickness of 1–3 mm, the thermal influence of which is omitted. However, the thermal uniformity of such a wall is strictly dependent on the quality of workmanship. The main objective of the analysis is to assess the impact of moisture on the U_wall of walls as a function of vertical joint spacing and horizontal joint thickness. It should be said that the effect of humidity and manufacturing accuracy on the thermal properties of aerated concrete walls has not been sufficiently studied. Further study of these patterns is necessary. Particular attention should be paid to the thin-bed mortar, which depends on the manufacturing accuracy. The separation of AAC masonry elements that occurs during bricklaying significantly affects the thermal insulation of walls. This issue has not yet been analysed. The scientific objective of this article is to develop a procedure for determining the thermal properties of a small, irregular air space created as a result of the separation of masonry elements and the impact of this separation on the thermal insulation of the wall. Based on the analysis of the thermal conductivity of voids and masonry elements, it was determined that this impact is visible at low AAC densities. A detailed analysis taking into account both these joints and horizontal joints, as well as different moisture levels, made it possible to determine the permissible separation of AAC blocks, at which the high thermal insulation requirements applicable in most European countries are met. The analysis showed that it is possible to meet the thermal protection requirements for 42 cm wide blocks intended for single-layer walls with a maximum vertical contact width of 3 mm and a joint thickness of up to 2 mm. AAC moisture content plays a major role in thermal insulation. Insulation requirements can be met for AAC in an air-dry state, as specified by ISO 10456. Full article

This study investigates the bond behavior of fabric-reinforced cementitious matrix (FRCM) composites with three common masonry substrates—solid clay bricks (SBs), perforated bricks (PBs), and concrete hollow blocks (HBs)—using knitted polyester grille (KPG) fabric. Through uniaxial tensile tests of the KPG fabric and FRCM system, along with single-lap and double-lap shear tests, the interfacial debonding modes, load-slip responses, and composite utilization ratio were evaluated. Key findings reveal that (i) SB and HB substrates predominantly exhibited fabric slippage (FS) or matrix–fabric (MF) debonding, while PB substrates consistently failed at the matrix–substrate (MS) interface, due to their smooth surface texture. (ii) Prism specimens with mortar joints showed enhanced interfacial friction, leading to higher load fluctuations compared to brick units. PB substrates demonstrated the lowest peak stress (69.64–74.33 MPa), while SB and HB achieved comparable peak stresses (133.91–155.95 MPa). (iii) The FRCM system only achieved a utilization rate of 12–30% in fabric and reinforcement systems. The debonding failure at the matrix–substrate interface is one of the reasons that cannot be ignored, and exploring methods to improve the bonding performance between the matrix–substrate interface is the next research direction. HB bricks have excellent bonding properties, and it is recommended to prioritize their use in retrofit applications, followed by SB bricks. These findings provide insights into optimizing the application of FRCM reinforcement systems in masonry structures. Full article