Search Results (123)

Structural design codes provide safe procedures for verifying steel–concrete composite beams but do not directly guide engineers toward cost-effective configurations. This study aims to develop and evaluate a surrogate-assisted framework that combines a Multilayer Perceptron neural network with Bayesian Optimization for the preliminary flexural-resistance and material-cost optimization of simply supported steel–concrete composite beams designed according to the Brazilian code NBR 8800. A dataset containing 20,000 beam configurations and 15 input variables was generated using a Python-based analytical routine that implements the NBR 8800 provisions for the positive bending resistance of composite beams. The generated dataset was used to train a Multilayer Perceptron neural network to predict the design bending resistance. The trained surrogate model was then integrated with Bayesian Optimization to search a discrete design space comprising commercial steel profiles, concrete slab thicknesses, shear connector quantities, and connector diameters. The selected neural network architecture achieved validation MAE and RMSE values of 2.128 kN·m and 3.013 kN·m, respectively, with an $R^2$ of 0.9999. In ten benchmark scenarios, the BO–MLP framework identified candidate solutions using only 60 objective-function evaluations. This corresponds to 3% of the evaluation budget adopted for GA and PSO and approximately 0.057% of the configurations examined by exhaustive search. Despite this limited sampling budget, the resulting candidate solutions presented an average optimality gap of approximately 12.1% relative to the global reference. In computational terms, GA and PSO required approximately 4.1 and 4.9 times the execution time of BO–MLP, respectively, while exhaustive search required approximately 18.4 times the execution time. Overall, the proposed framework offers a computationally efficient means of exploring discrete composite-beam configurations and identifying cost-competitive candidate solutions. Direct NBR 8800 verification showed that seven of the ten selected candidates satisfied the resistance requirement, while three presented resistance-to-demand ratios slightly below unity. Therefore, the framework should be used as a preliminary screening tool, with the selected configurations subsequently verified using the complete code-based procedure. Within the restricted structural domain investigated, the framework can support preliminary decisions related to positive bending resistance and material cost. Full article

A simply supported rectangular isotropic ferromagnetic plate with magnetocaloric properties subjected to convective heating on its upper surface is considered. The governing equations comprise a system of two-dimensional transient equations for the thickness-averaged temperature characteristics of the plate and the two-dimensional bending equations for isotropic plates expressed in terms of generalized displacements within the framework of first-order shear deformation theory. Closed-form solutions to the governing equations are obtained by expanding all thermal and mechanical field quantities in double Fourier sine series satisfying the prescribed boundary conditions, combined with the Laplace transform in time applied to the thermal quantities. A comparative numerical analysis is carried out for the magnetocaloric ferromagnetic plate and a carbon steel plate under ambient temperature rising at a finite rate to a prescribed value. The dependences of all quantities under investigation on the ambient temperature rise rate, time, convective heat transfer coefficient, thermal conductivity of the ferromagnetic material, and geometric parameters of the plate are analyzed and presented graphically. The results obtained provide a quantitative basis for assessing the thermoelastic state and for optimizing the geometry and operating conditions of active magnetic regenerator plate stacks with a view to enhancing their structural reliability. Full article

All-light shale ceramsite concrete (ALSCC) is a lightweight building material suitable for self-weight-sensitive flexural members in prefabricated and long-span structures, but experimental data on its flexural behavior remain limited. This study aims to characterize the physical and mechanical properties of ALSCC and evaluate its flexural behavior under the present test conditions through comparison with C30 normal concrete. Cubic material-property tests and four-point bending tests on simply supported beams were conducted. Material tests showed that the average density of ALSCC was 65.2% of that of normal concrete, while its cube compressive strength and splitting tensile strength were 80.6% and 82.3% of the corresponding values for normal concrete, respectively. Cracks in the ALSCC material specimens tended to propagate through the ceramsite aggregates, indicating a relatively brittle fracture response at the material level. Three ALSCC beams (AL-B1, AL-B2, and AL-B3) and one normal-concrete control beam (NC-B1) were tested to analyze failure modes, load–deflection responses, sectional strain distributions, and reinforcement-strain responses. Test results showed that the ALSCC beams exhibited typical under-reinforced flexural failure, with cracking loads of 5.0–6.5 kN and peak loads of 40.4–42.5 kN, which were comparable to the 41.6 kN peak load of the normal-concrete control beam. The peak loads of the ALSCC beams occurred at midspan deflections of 13.10–14.47 mm. Under continued displacement-controlled loading, maximum recorded midspan deflections of 38.01–40.45 mm were reached at test termination. Within the present test program, the ALSCC beams exhibited lower elastic-stage stiffness than the normal-concrete control beam, while approximately linear sectional strain distributions were observed within the measured load range. The reinforcement-strain responses of the ALSCC beams were also broadly comparable to the response of the control beam. This work provides preliminary material-specific experimental evidence on the flexural behavior of ALSCC simply supported beams under the present test conditions and provides a basis for further validation using larger specimen sets. Full article

The free vibration behaviour of functionally graded (FG) doubly curved nanoshells is explored by adopting a refined first-order shear deformation theory (FSDT) formulated with only four displacement variables. The presented kinematic model, which decomposes the transverse displacement to bending and shear components, provides an efficient and accurate framework for capturing structural response while requiring substantially lower computational effort than traditional higher-order theories. By utilising a power-law pattern, the nanoshell’s material properties are changing continuously within the thickness. Eringen’s nonlocal elasticity theory is implemented, which considers the size-dependent impact that occurs at the nanoscale. The governing equations of motion are constructed via the application of Hamilton’s principle and solved analytically by Navier’s method for simply supported boundary conditions. The current model’s accuracy and dependability are validated by comparisons with published results for various limiting cases such as spherical, cylindrical, and hyperbolic paraboloidal shells. A thorough parametric study is then carried out to examine the effects of the nonlocal parameter, power-law index, side-to-thickness ratio, curvature ratio, and aspect ratio on natural frequencies. Full article

The first approximation ($N=1$) of a three-dimensional micropolar elastic prismatic body in moments of displacement and rotation, obtained via Legendre polynomial expansion, is applied to two related problems: field reconstruction and damage identification. In the first problem, two- and three-dimensional field distributions are reconstructed for a simply supported square prismatic body under three loading configurations, with first-order moment loading as the primary case. Two distinct resonances are identified within the $N=1$ framework. At the material cutoff ${\omega }_c=\sqrt{4\alpha /J}$, micro-rotation amplitudes are amplified while translational amplitudes are suppressed (displacement locking). At the geometric cutoff ${\omega }_{\mathrm{geo}}\propto h^{-1}$, the bending mode is resonantly excited while micro-rotation remains near its quasi-static level. In the second problem, a scalar damage model ${\alpha }_{\mathrm{eff}}=\alpha (1-D)$ is introduced. The material cutoff follows ${\omega }_c\left(D\right)={\stackrel{o}{\omega }}_c\sqrt{1-D}$, confirmed numerically for all four decoupled subsystems and different prismatic body thicknesses. Geometric branches remain insensitive to damage, producing a spectral separation that may serve as a damage indicator. A critical thickness $h^{*}$ is identified where ${\omega }_{\mathrm{geo}}={\stackrel{o}{\omega }}_c$, leading to role reversal between material and geometric branches. Numerical results are presented for the polyurethane foam of Lakes. Full article

This study presents an analytical model for the long-term bending behavior of simply supported laminated glass (LG) plates with temperature-dependent viscoelastic interlayers. The glass layers are described based on three-dimensional elasticity theory, and the governing stress and displacement equations are formulated using the state-space method. The polymer interlayer is characterized by the generalized Maxwell model and the Williams–Landel–Ferry equation, while its time-dependent response is described through the Boltzmann convolution principle. By combining double Fourier series expansions with the Laplace-transform technique, analytical solutions for the stresses and displacements of multilayer LG plates are derived. The comparison shows that Kirchhoff–Love plate theory gives results close to the present solution for relatively thin LG plates, whereas the discrepancy becomes increasingly pronounced as the plate thickness increases. The finite element results agree well with those obtained from the proposed model; however, for the representative benchmark case, the present solution is approximately 1.13 × 10³ times faster than the FE simulation, and its memory usage is only about 10.88% of that required by the FE model. Parametric studies further reveal the effects of temperature, interlayer thickness, interlayer material, number of glass layers, and aspect ratio on the stress redistribution and deflection development of LG plates. Full article

This study experimentally investigates the structural behavior of steel–concrete composite beams with circular web openings under monotonic loading to evaluate the effects of opening location and number on structural performance while maintaining feasibility for integrating mechanical, electrical, and plumbing (M.E.P.) systems. Six simply supported composite beam specimens were tested, including one reference beam without openings and five beams with 80 mm diameter circular web openings. The investigated variables were limited to the presence, number, and longitudinal location of the openings, while the beam dimensions (IPE160 section, 2.8 m clear span), material properties, reinforcement details, shear connector arrangement, and loading conditions were kept constant. The study addresses a specific research gap: Previous studies have primarily focused on the effects of opening number and size on ultimate load capacity, with limited systematic investigation of how opening location influences not only ultimate load but also stiffness and ductility. Openings were strategically placed in three critical zones: the shear zone (low stress region), the bending zone (high moment region at mid-span), and the region under load points. The experimental results demonstrated that opening location is more critical than opening number. Openings in the shear zone achieved the best performance with only 2.13% reduction in ultimate load capacity, making it the preferred location for service openings. Openings in the bending zone (mid-span) or under load points caused reductions ranging from 9.62% to 11.70%, attributed to interference with high bending stresses. Notably, the configuration with ten openings achieved a load reduction similar to the two-opening configurations when located in the shear zone, confirming the dominant role of location over opening number within the experimental program. These results support a location-driven design philosophy for composite beams with web openings. However, these findings are restricted to the present experimental configuration—specifically 80 mm circular openings, IPE160 steel section, 2.8 m clear span, and the tested loading condition—and should not be generalized to composite beams with different geometric parameters, material properties, or loading conditions without additional research. Full article

This study investigates the use of magnetoelastic sensing for vibration-based structural health monitoring (SHM) of cementitious beam specimens under intact and damaged conditions. Prismatic mortar beams with dimensions of 160 × 40 × 40 mm³ were fabricated following standardized preparation procedures and equipped with annealed amorphous ferromagnetic ribbons, Metglas 2826MB3, for nondestructive magnetoelastic vibration sensing. The specimens were tested under free-vibration conditions in a simply supported configuration, and their vibration response was measured using a detection coil and subsequently analyzed using MATLAB software. The undamaged specimen exhibited a dominant resonance frequency at 6531 Hz, which closely corresponded to the fourth bending mode predicted by Euler–Bernoulli beam theory. Controlled notch-shaped cracks with varying locations and depths were subsequently introduced to evaluate the sensitivity of the sensing system to structural damage. Experimental results showed that the frequency shift is strongly influenced by the location of damage relative to the modal nodes, with maximum sensitivity observed between nodal regions and minimal variation near the nodes. Furthermore, increasing notch-shaped crack depth produced progressively larger frequency shifts, revealing a monotonic and non-linear relationship between damage severity and dynamic response. Polynomial fitting and 3D surface analysis further highlighted the combined influence of crack location and depth on the measured frequency variation. The findings confirm that the magnetoelastic sensor is capable of accurately detecting and magnetically transmitting the vibration state and damage-induced changes in cementitious structures, demonstrating high sensitivity and strong potential for application in vibration-based structural health monitoring systems, particularly in materials characterized by strong vibration damping. Full article

This paper investigates the thermal buckling behavior of a four-edge simply supported bimodular functionally graded rectangular thin plate subjected to thermal loads. Unlike existing studies, this work introduces the bimodular effect into the thermal buckling analysis of functionally graded thin plates for the first time, accounting for the influence of tension–compression modulus on the critical temperature difference. The problem is challenging due to the complexity of materials and the nonlinearity of structural thermal buckling. For the theoretical analysis, we propose a simplified mechanical model which contains the four important assumptions: there exists a neutral plane in bending; the influence of shear stresses may be neglected; the membrane effect and bending effect are considered separately; and there are two different buckling regimes: a compression-dominated pre-buckling state and a bending-dominated post-buckling state. Three types of thermal loading cases are considered, including uniform temperature rise, linear temperature gradient through the thickness, and nonlinear temperature distribution satisfying Fourier’s law of heat conduction. Within the framework of the simplified mechanical model, the pre-buckling membrane forces, equilibrium equations, and stability equations are derived, thus obtaining a closed-form analytical expression for the critical buckling temperature difference under three different temperature rise modes. The reliability of the present analytical model is validated through comparison with finite element results. Furthermore, a detailed parametric study is conducted to reveal the influences of aspect ratio, width-to-thickness ratio of plate, bimodular indices, and gradient parameters of materials on the critical temperature difference. The results provide a theoretical basis for the thermal stability design of bimodular functionally graded plates operating in high-temperature environments. Full article

This paper innovatively employs an epoxy-free composite layer with basalt fiber-reinforced polymer (BFRP) and engineered cementitious composite (ECC) to reinforce the two-way concrete slab structure. Five strengthened slabs and one reference slab were tested under biaxial bending moments with four-side simply supported conditions. The thickness of ECC (15, 25, 35 mm) and BFRP grid (1, 2, 3 mm) were selected as two main variables in the test program. The experimental results showed that the cracking and ultimate load of the strengthened slabs were substantially improved. Notably, the cracking pattern was shifted from diagonally concentrated cracks to discontinuous short cracks, with no apparent debonding of the composite layer. As the thickness of the BFRP grid and ECC increases, both the flexural capacity and stiffness improve, with decrease in the maximum deflection and effective utilization rate of steel reinforcement and BFRP grid at mid-span. Furthermore, a theoretical model considering different positional distribution of yield line was proposed to predict the bearing capacity of the strengthened slabs, with the calculated values aligned well with the experimental results. This research highlights the FRP–ECC composite as a robust reinforcement method for two-way slabs, and offers a good design-oriented reference basis in the field. Full article

To address the technical challenges associated with complex connection configurations and excessively long lap zones in the industrialized and prefabricated construction of reinforcements, this study proposes a novel parallel-lap splice that incorporates a third overlapping reinforcement. This innovative design offers several advantages, including neat ends, ease of construction, and enhanced economic efficiency. An experimental investigation was conducted to evaluate the effects of this new splice on the flexural behavior of reinforced concrete (RC) beams, with lap length (l_l) as the key variable (l_l = 64d, 40d, and 25d). A total of nine simply supported RC beams (three groups of three specimens each), all incorporating parallel-lap splices, were tested under four-point bending. The key mechanical properties were analyzed, including the mechanical characteristics, failure modes, flexural capacity, bending stiffness, and maximum flexural crack width. The experimental and analytical results reveal that RC beams with the new parallel-lap splice exhibit a distinctive “one primary + two secondary” crack pattern, characterized by a dominant flexural crack at midspan and secondary cracks at the ends of the lap zone. At the ultimate limit state, specimens with l_l = 64d experienced concrete crushing at the top surface of the midspan while those with l_l = 40d and l_l = 25d did not. Additionally, the l_l = 64d and l_l = 40d beams showed slight strength hardening, whereas the l_l = 25d beams exhibited rapid strength degradation. In terms of load-bearing capacity, both the l_l = 64d and l_l = 40d beams met the requirements specified in current design codes, while the l_l = 25d specimens showed a reduction in capacity exceeding 20%. Under serviceability limit states, midspan deflections and maximum crack widths for the l_l = 64d, l_l = 40d, and l_l = 25d specimens were found to fully comply with, marginally satisfy, and fail to meet the requirements of the design code, respectively. Based on these findings, as well as regression analysis of the relationship between peak load and lap length, it is recommended that a reasonable lap length for the proposed parallel-lap splice be taken as 60d, with a lap length correction factor of 1.5. Full article

This study examines the bending of cross-ply laminated composite nanoplates coupled to a piezoelectric fiber-reinforced composite layer via the nonlocal strain gradient theory. The aim is to accurately capture size-dependent impacts and electromechanical interaction in nanoscale composite structures. The mechanical response is modeled utilizing a refined four-variable shear deformation theory, with the governing equilibrium equations developed using the virtual work assumption. The nanoplate is examined under simply supported boundary conditions exposed to both mechanical loading and applied electric voltage. A detailed parametric investigation is done to assess the contribution of non-local and strain gradient factors, imposed voltage, and geometric ratios on the bending behavior. The results show that the nonlocal parameter generates a softening result, increasing deflection, whereas the strain gradient parameter raises stiffness and minimizes deformation. Moreover, the applied voltage successfully controls the bending response by electromechanical actuation, underlining the potential of PFRC-integrated nanoplates in smart nanoscale systems. Full article

The size-dependent out-of-plane vibrational behavior of graphene-based nanoelectromechanical (NEMS) resonators is investigated using a molecular mechanics (MM) finite element approach. Each carbon–carbon (C–C) bond is modeled as an Euler–Bernoulli beam element, with the bending stiffness derived from the bond-angle potential, yielding an equivalent plate flexural rigidity D = (√3/6) kθ. The natural frequencies of the first four vibration modes are computed for square graphene sheets of increasing size with both zigzag (ZZ) and armchair (AC) chirality configurations under simply supported boundary conditions on all four edges. A chirality-induced frequency deviation δ(L) is defined to quantify the difference between ZZ and AC results, and a threshold size L* is identified as the sheet size at which δ falls below 1%. For mode 1, the threshold is L* = 18.5 nm; the values increase monotonically to 24.5 nm, 28.0 nm, and 31.5 nm for modes 2 through 4, indicating that higher modes require larger sheet dimensions before continuum plate theory becomes reliable. A dimensionless frequency parameter Ω = f_MM/f_CT is introduced to directly compare MM predictions with the Kirchhoff plate theory analytical solution, and the AC frequency ratio Ω = f_MM/f_CT is shown to converge toward unity with increasing sheet size. The present results provide quantitative design guidelines for graphene NEMS resonators and establish the minimum device dimensions for which isotropic continuum models yield accurate dynamic predictions. Full article

In structural engineering practice, the problem of thick plate bending occurs in designing shelters, foundations of high-rise buildings, counter-slabs, etc. In such cases, neglecting shear deformation can lead to significant errors in predicted behavior, especially when a plate is subjected to a concentrated force. In practice, neither a fully clamped nor an ideal simple support can be achieved during construction, so the plates are partially clamped, and this also applies to thick plates. Bending of thick rectangular plates with partially clamped edges has not been studied in the literature, so this paper addresses this issue. A comprehensive numerical analysis using a developed simple analytical model in the form of a Lévy-type solution based on Reissner theory has been carried out. The presented model is able to account for different degrees of rotational restraint in plates with two opposite edges simply supported and the other two partially clamped by introducing the fixity factor. The obtained results are compared with those available in the literature, as well as with a numerical FEM model, whereby good agreement is observed. The significant difference when using the proposed model to analyze a thick plate, as opposed to the models based on Kirchhoff theory, is underlined. Full article

To address the inherent inaccuracies of the classical beam theory (which overestimates the flexural stiffness) and the “quasi-plane section method” (which neglects the shear deformation) in the deflection analysis of steel truss web–concrete composite beams, this study homogenizes discrete steel truss web members into a continuous steel web with equivalent thickness based on the strain energy equivalence principle. This homogenization is conducted under the assumption of fixed-end constraints for web members, thus establishing a sandwich laminated beam model. Incorporating the assumptions of zigzag axial displacement and layer-wise quadratic parabolic transverse shear stress, this study adopts the governing equations for static bending of composite beams derived via Hamilton’s mixed energy variational principle—this theory eliminates the need for an artificial shear correction factor, as the transverse shear stress naturally satisfies the zero boundary conditions at the upper and lower surfaces and the continuity condition at the interlayers. Analytical solutions for bending deflection under uniformly distributed loads are derived and validated against three-dimensional (3D) finite element (FE) models. The analysis results of a 45-meter-span beam demonstrate that the relative error in the maximum deflection of both simply supported beams and cantilever beams calculated by the proposed method is approximately 5%, which is significantly superior to the classical beam theory; the deflection induced by the zigzag effect at the mid-span of simply supported beams accounts for 15% of the total deflection, making it an indispensable key component in structural design. This method enables accurate deflection prediction and provides reliable technical guidance for the preliminary design of steel truss web–concrete composite beam bridges. Full article