Cracked Beams Research Articles

Analysis of Strengthening Beam Structure Case Study on Food Court Building of Ruang Terbuka Hijau (RTH) Project at Alun-Alun Kota Kediri

The Green Open Space (RTH) construction in Kediri City includes a food court building utilizing reinforced concrete structures. During construction, cracking issues occurred in several beam structures due to the inability to bear the design loads effectively, necessitating a strengthening approach. This study aims to develop and evaluate a strengthening method for cracked beam structures by employing concrete jacketing. The specific objective is to improve the structural integrity and load-bearing capacity of these beams to ensure the durability and safety of the building. A concrete jacketing technique was used to reinforce the cracked beams, utilizing K-300 ready-mix concrete and additional reinforcing steel. The study involved structural analysis to assess the load-bearing capacity before and after jacketing, and on-site evaluation was conducted to monitor the method's effectiveness. The findings indicate that the jacketing method significantly increased the beams' bending moment capacity and overall structural strength, successfully addressing the cracks and enhancing the beams' ability to bear the intended loads. The reinforced beams showed improved load distribution and structural resilience performance. Concrete jacketing proved to be an effective method for strengthening the cracked beam structures in the Green Open Space project. The study provides valuable insights for similar future construction projects, suggesting that concrete jacketing can be a reliable reinforcement technique to enhance the durability and safety of building structures.

Automated Surface Crack Identification of Reinforced Concrete Members Using an Improved YOLOv4-Tiny-Based Crack Detection Model

In recent times, the deployment of advanced structural health monitoring techniques has increased due to the aging infrastructural elements. This paper employed an enhanced You Only Look Once (YOLO) v4-tiny algorithm, based on the Crack Detection Model (CDM), to accurately identify and classify crack types in reinforced concrete (RC) members. YOLOv4-tiny is faster and more efficient than its predecessors, offering real-time detection with reduced computational complexity. Despite its smaller size, it maintains competitive accuracy, making it ideal for applications requiring high-speed processing on resource-limited devices. First, an extensive experimental program was conducted by testing full-scale RC members under different shear span (a) to depth ratios to achieve flexural and shear dominant failure modes. The digital images captured from the failure of RC beams were analyzed using the CDM of the YOLOv4-tiny algorithm. Results reveal the accurate identification of cracks formed along the depth of the beam at different stages of loading. Moreover, the confidence score attained for all the test samples was more than 95%, which indicates the accuracy of the developed model in capturing the types of cracks in the RC beam. The outcomes of the proposed work encourage the use of a developed CDM algorithm in real-time crack detection analysis of critical infrastructural elements.

Fatigue damage analysis and mitigation for steel structures using UHM-CFRP prestressed technique

Fatigue stresses in steel bridges can lead to crack propagation, gradually decreasing the structural stability of the bridge. Conventional strengthening techniques for structures have shown limited effectiveness in preventing crack growth. The objective of this research is to enhance the fatigue life of cracked steel beams through the application of ultra-high modulus carbon fiber reinforced polymer (UHM-CFRP) plates. Two sets of tests, including quasi-static testing and fatigue testing, were conducted on both cracked and uncracked steel beams. All beams were tested under identical loading conditions, with a total of five beams examined. Control beams were used to compare fatigue life under different loading ranges. One beam was reinforced with UHM-CFRP plates, another utilized prestressed UHM-CFRP plates, and another employed UHM-CFRP plates with end clamps. The experimental study revealed a significant 8 times increase in fatigue lives for cracked steel beams repaired using the UHM-CFRP compared to the control beam. Additionally, the (10 %) prestressed UHM-CFRP plate not only doubled the fatigue life of identical beams compared to UHM-CFRP plates but also significantly reduced residual deflection during fatigue crack growth, highlighting its efficacy in fatigue resistance.

Flexural behavior and numerical simulation of reinforced concrete beams with a UHPC stay-in-place formwork

To overcome the shortcomings of traditional concrete structures such as long construction cycle, high construction cost and poor durability, seven composite beams with a UHPC stay-in-place formwork (UCB) and one reinforced concrete (RC) beam were designed. An experimental study was conducted to investigate the flexural behavior of composite beams under the static load. The research parameters include formwork thickness, reinforcement rate, and formwork surface treatment. The results revealed that roughening the surface of UHPC formwork has a positive impact on enhancing the integrity of composite beams. The utilization of UHPC stay-in-place formwork can effectively improve the stiffness, cracking load, and peak load of members. Compared with that of the RC beam, the cracking load and peak load of composite beams increased by 63% ~ 103% and 6% ~ 15%, respectively, and the yielding stiffness increased by 23% ~ 41%. Different from the RC beam, new cracks occurred on one side of the initial crack's end and continued to extend upwards rather than along the original crack. The existence of a significant quantity of tiny cracks in composite beams effectively slowed down the increase in the width of pre-existing cracks in the early stage of loading. Due to the multi-crack pattern exhibited by the UHPC formwork, the strain concentration of the steel bars was effectively mitigated. When subjected to the same load level, the strain of the longitudinal steel bars in composite beams was smaller than that of the RC beam. The formula for calculating the flexural bearing capacity of composite beams is established through theoretical analysis. In addition, the numerical model of the composite beam is established by the finite element method (FEM). The influence of the contact method of the UHPC-NC interface on the flexural performance of the composite beam is explored. The supplementary analysis of the parametric study of the reinforcement rate and the UHPC formwork thickness is carried out. When using ABAQUS for the numerical analysis of the composite beam, it is appropriate to adopt the cohesion model or the Tie model for the UHPC-NC interface, and it is not appropriate to use the Coulomb friction model.

Potential of Non-Contact Dynamic Response Measurements for Predicting Small Size or Hidden Damages in Highly Damped Structures.

Vibration-based structural health monitoring (SHM) is essential for evaluating structural integrity. Traditional methods using contact vibration sensors like accelerometers have limitations in accessibility, coverage, and impact on structural dynamics. Recent digital advancements offer new solutions through high-speed camera-based measurements. This study explores how camera settings (speed and resolution) influence the accuracy of dynamic response measurements for detecting small cracks in damped cantilever beams. Different beam thicknesses affect damping, altering dynamic response parameters such as frequency and amplitude, which are crucial for damage quantification. Experiments were conducted on 3D-printed Acrylonitrile Butadiene Styrene (ABS) cantilever beams with varying crack depth ratios from 0% to 60% of the beam thickness. The study utilised the Canny edge detection technique and Fast Fourier Transform to analyse vibration behaviour captured by cameras at different settings. The results show an optimal set of camera resolutions and frame rates for accurately capturing dynamic responses. Empirical models based on four image resolutions were validated against experimental data, achieving over 98% accuracy for predicting the natural frequency and around 90% for resonance amplitude. The optimal frame rate for measuring natural frequency and amplitude was found to be 2.4 times the beam's natural frequency. The findings provide a method for damage assessment by establishing a relationship between crack depth, beam thickness, and damping ratio.

Experimental and numerical study on behavior of demountable T-shaped bolt shear connectors in sustainable composite beams

This paper proposed a new type of demountable T-bolt shear connector to improve the disassembly efficiency of composite beams and realize the sustainable of the structure components. The shear behavior of nine groups of push-out specimens was experimentally investigated through monotonic loading push-out tests. The finite element analysis (FEA) models were validated against the test results, specifically in terms of the load-slip responses and failure modes of the T-bolt shear connectors in these push-out specimens. The obtained results show that all the specimens have no obvious deformation and cracks in the steel beam and RC slab. The separation between the slab and the steel beam is no more than 1 mm, indicating that the anti-lifting ability is excellent. Moreover, parametric analysis demonstrates that increasing the bolt pretension of the T-shaped shear connector and the friction coefficient between the bridge gasket and the steel beam significantly enhances the initial stiffness and ultimate strength of the shear connectors. However, the shear behavior is relatively insensitive to variations in the channel thickness and bolt grade. Based on regression analysis, a load-slip mechanical model has been proposed. This model accurately describes the mechanical properties of this type of shear connector, providing a theoretical foundation for the application of demountable composite beams.

Flexural behavior of coral aggregate concrete beams reinforced with BFRP bars under seawater corrosion environments

The combined utilization of fiber-reinforced polymer (FRP) composites with coral aggregate concrete (CAC) in remote island areas contributes to the reduced construction cost and construction period, offering a promising application. However, the evolution pattern and deterioration mechanism of flexural behavior for FRP bars reinforced CAC beams in marine service environments remains unclear. Thus, this paper investigates the flexural behavior of basalt-FRP (BFRP) bars reinforced CAC beams under seawater immersion and dry-wet cycle conditions using laboratory-accelerated aging methods. The research considers the effects of exposure temperature and corrosion age on their failure modes, flexural stiffness, ultimate loading capacity, and deformation deflection. The experimental results revealed that with the increase in corrosion age and exposure temperature, the amount of vertical cracks of CAC beams decreased and their crack depth also exhibited a slight reduction, but their crack width and spacing at failure significantly increased. After being attacked by seawater environments, the load-deflection curves of CAC beams experienced an enhanced slope of the ascending section (i.e., flexural stiffness), but this strengthened flexural stiffness did not result in an enhancement in the ultimate load capacity. Instead, with prolonged corrosion and higher temperatures, the ultimate load of CAC beams displayed significant degradation, accompanied by reduced mid-span deflection. After 12 months of seawater exposure to wet-dry cycle conditions at 60 °C, the ultimate load and mid-span deflection of CAC beams degraded by approximately 25.0 % and 56.6 %, respectively. The study also predicted the flexural bearing capacity of CAC beams utilizing existing specifications for FRP-reinforced normal aggregate concrete (NAC). It was concluded that the formulae for flexural loading capacity for FRP-reinforced NAC beams were still suitable for CAC beams.

Fatigue life prediction of cracked cross beam of mining linear vibrating screen under cyclic load

The cross beam of a mining linear vibrating screen is prone to cracking under long-term cyclic load. In order to accurately predict the fatigue life of the cracked cross beam, a coupled analysis method of vibration and crack propagation is proposed. A 2D dynamic model of the vibrating screen is established based on the finite element method, which is verified by the vibration test platform. The cracked Euler beam element is used to model the cracked cross beam. The effects of crack depth, amplitude of excitation force, frequency of excitation force, and crack location on the crack-tip stress intensity factor of the cracked cross beam are investigated in detail. In addition, an iterative method is proposed on the basis of the Paris model. The residual service life of the beam under different frequencies of excitation force, amplitudes of excitation force, spring stiffness, crack positions, and degrees of stiffness imbalance are discussed. The results demonstrate that the fatigue life of the beam increases as the frequency of excitation force and spring stiffness increase. The increase of the amplitude of excitation force and spring permanent deformation reduces the fatigue life. The conclusion obtained provide some theoretical guidance for the design and routine maintenance of mining linear vibrating screens.

Bending performance of lightweight aggregate concrete beam subjected to reinforcement corrosion: Experimental and numerical study

The application of lightweight aggregate concrete (LWAC) benefits the structural behavior of long-span and high-rise buildings. However, the corrosion-related durability issue of bending elements made of LWAC has remained unresolved for decades, and the bending performance of corroded LWAC beam, including load-bearing capacity, stiffness, cracking, and etc., has not yet been clearly defined due to limited knowledge in the available literature. This study aims to investigate the bending performance of LWAC beams subjected to reinforcement corrosion, and the test results provide valuable data for addressing the research gap relevant to the topic and contribute fundamental knowledge to the promotion of structural LWAC elements. Seven reinforced LWAC beams were tested to examine the cracking behavior, characteristic loads and deflections, deformation ability, and distribution of cross section strain at various moments. The modelling method considering the effect of rebar corrosion for LWAC beam was proposed. It was concluded that the corrosion of longitudinal rebar led to decreased cracking, yielding, and ultimate moment of LWAC beam, while the corrosion of stirrups increased the cracking moment and had little effects on the yielding and ultimate moments. The ductility of the tested specimens initially decreased and then increased with the raising corrosion level of the longitudinal rebar, which was attributed to the variation in bond performance between the rebar and LWAC. All tested beams exhibited a yielding deflection smaller than 1/235 of the span length. The strain distribution of the mid-span cross-section exhibited a nonlinear feature with increasing mass loss of the corroded longitudinal steel rebar. The proposed modelling procedure considering the corrosion effect showed good agreement with the test results, and a preliminary analysis of the bending performance of LWAC beams with different steel reinforcement corrosion ratios was completed. Data Availability StatementAll data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.

Vibration-based damage detection of beams using Hybrid Genetic Algorithm with combined l0 and l1 regularization

Vibration-based damage detection is an effective way of identifying beam damages before they become severe and potentially catastrophic. This paper introduces a novel and robust method for detecting multiple cracks in beams using a Hybrid Genetic Algorithm (HGA). The objective function of the proposed method, based on dynamic properties, can be employed with partial modal information and is enhanced by including the initial residuals between numerical and experimental models along with combined l0 and l1 regularization. This enhancement mitigates the impact of limited modal data, experimental noise, and modeling inaccuracies. Additionally, a method of selecting an appropriate regularization parameter by analyzing residual and solution norm curves is presented. The performance of the proposed method is evaluated and verified using both numerical simulations and experimental studies on a steel cantilever beam under four damage scenarios. In the experimental study, natural frequencies and mode shapes were determined under ambient vibration conditions using Enhanced Frequency Domain Decomposition (EFDD) and the Stochastic Subspace Identification (SSI) method. Finite element models of the beam were developed in ABAQUS software for numerical analysis, and a comparative study of numerical and experimental data was conducted. The proposed approach successfully identifies, locates and quantifies single and multiple damages in the beam, demonstrating its reliability and effectiveness, particularly in scenarios with limited modal data and significant experimental noise.

Dynamics of a cross beam with a straight crack in a mining linear vibrating screen

Cross beam fracture is one of the common failures of vibrating screens, and crack is the early manifestation of fracture, which is hard to detect. In order to meet the screening requirement of the vibrating screen and improve the service life of the cracked beam, the cracked Euler-Bernoulli beam model is established to investigate the dynamics of the cross beam with a straight crack under different weights of eccentric block, processing capacities, and Rayleigh damping coefficients based on the finite element method in this paper. The local flexibility coefficients are derived from the principles of fracture mechanics and strain release energy and solved by the adaptive five-point Gaussian Legende algorithm. The stiffness matrix of the cracked beam element is calculated through the inverse method of total flexibility. The four order Runge-Kutta algorithm and MATLAB tools are used to solve the dynamic equation of the cracked cross beam. The relationship between the vibration amplitude of the cracked cross beam and the weight of the eccentric block is studied by fitting formulas using the least squares method. The influence of different weights of eccentric block, processing capacities, and Rayleigh damping coefficients on the vibration amplitude and service life of the cracked beam are discussed. The results show that the greater the weight of the eccentric block, the shorter service life of the beam. When the damping is greater, the service life of the cracked beam is longer.

Dynamic analysis of extensible beam with multiple cracks

We present the governing equation and study vibrations of multiple crack beams undergoing large deflections subject to transverse loads. First, the primary motion equation is derived using Hamilton’s principle applied to energy functions accounting for cracks. Then we derive a normalized equation governing the vibration of the extensible cracked beam. Single and multiple crack beam examples are considered and analyzed numerically to verify the validity of the derived equations. We propose a modified cracked extensible beam model accounting for the axial force by considering the reduced cross-sectional area. It is expressed by a new reduction parameter. Using the proposed model, we numerically investigate how the cracked extensible beam’s natural frequencies change depending on various model parameters.

Comparison Between the Behavior of Reinforced Concrete Beams and RPC Beams Under Bending and Torsion Moments

Abstract Typically, the beams were subjected to bending and torsion moments especially at building edge. However, most of the studies focus on the flexural or torsional behavior of the beams independently, and few studies investigated these two combined effects. The research intends to explore the structural behavior of eight 1500mm x 200 mm x 150 mm rectangular beams that were tested under the combined effects of bending and torsional moments, with four main values of (T/M) ratio: pure bending, pure torsion, and two combined cases. The research investigates the effect of using reactive powder concrete (RPC) on beam behavior compared to normal concrete (NC). The outcome demonstrates that using RPC in beams instead of NC beams will significantly increases the cracking capacity by 136.4% in the case of pure bending and significantly increases the ultimate capacity by 118% in the case of combined moments with (T/M = 1). Also, using RPC leads to significant reduction in deflection and rotation values especially after beam cracking. RPC reduces compressive concrete strain and values of strains in longitudinal and transverse reinforcement especially in advanced loading stages.

Enhancing shear strength of RC beams through externally bonded reinforcement with stainless-steel strips and FRCM jacket to mitigate the failure risk

This study aims to assess the efficacy of innovative and sustainable methods in improving the shear performance of Reinforced Concrete (RC) beams lacking shear stirrups. Eleven specimens, including two control specimens and nine strengthened ones, underwent monotonic loading through three-point testing. Various strengthening configurations were investigated, involving the application of Stainless-Steel Strips (SSSs) affixed to the beam surface in the defective zone, along with a Fiber-Reinforced Cementitious Matrix (FRCM) jacket. In the first set of beams, SSSs were vertically applied, while the second set featured beams with SSSs inclined at 60°, and the third set had SSSs inclined at 45°. Each set comprised three beams, allowing for the examination of the impact of SSS thicknesses, set at 1 mm, 1.25 mm, and 1.50 mm. After the installation of SSSs, all strengthened beams received an FRCM jacket, including a 5 mm Engineered Cementitious Composites (ECC) layer with embedded Glass Fiber Reinforced Polymer (GFRP) textile. The study concludes that incorporating SSS strips with an FRCM jacket delays the initiation of the first crack in defective beams. Increasing SSSs thickness contributes to a more favorable crack distribution. The 60° inclined SSSs proves to be the most effective, rectifying the deficiency from the absence of shear stirrups and surpassing the original beam's performance. Additionally, finite element analysis was conducted, and the results supported the accurateness of the developed model in simulating responses and crack patterns throughout all loading stages.

Estimation of load-carrying capacity of cracked RC beams using 3D digital twin model integrated with point clouds and images

Digital twin (DT) is capable of managing, simulating, and future performance prediction of existing infrastructures by integrating three-dimensional (3D) geometric model and finite element (FE) model. This study aims to automatically generate geometric DT of existing RC members using point clouds and incorporate damages detected from images into FE models. An edge-based modeling method was proposed to extract sharp features for geometry reconstruction with incomplete point clouds, and an automated procedure was established for registering images to point clouds, mapping cracks detected in images to FE models, and assigning reduced material properties. Four RC beams were tested in a laboratory to validate the proposed method. Existing cracks were found to have a significant effect on structural capacity and failure mode. The results also showed that the developed FE model produced a good agreement between experimental and predicted failure loads while providing a more efficient and time-saving assessment protocol.

The effect of inhomogeneous microstructures on strength and stress corrosion cracking of 7085 aluminum alloy thick plate

Inhomogeneous microstructures and alloy chemistry along the thickness direction can greatly affect the mechanical and corrosion properties of new generation 7xxx aluminum alloy thick plates. The inhomogeneous microstructure, stress corrosion cracking (SCC) resistance and strength of AA7085 thick plate (160 mm) at T/2, T/4, and surface position using mechanical tests, double cantilever beam (DCB) crack extension tests and electron microscopy experiments. The results show that the ultimate tensile strength, yield strength and elongation of the T/2 position are slightly lower than those of the surface position, but the SCC resistance of the T/2 position is significantly higher than that of the surface position. The reason is that larger discontinuously quench-induced grain boundary precipitates (Q-GBPs), and lower Zn and Mg elemental content of GBPs (including Q-GBPs and age-induced GBPs (A-GBPs)) and grain boundaries (GBs). Furthermore, it is newly found that the mechanical effects of larger-sized low aspect ratio unrecrystallized grains contribute significantly to the excellent SCC resistance of the T/2 position. The large size grain structure makes short-range SCC cracks along the large-angle GB more tortuous at T/2, improving the stress intensity required for sustained crack extension. In addition, the high GB triple junction deflection angle resulting from a low aspect ratio grain structure at T/2 improves the average driving force required for crack extension and drive force reduction after localized crack growth.

The behaviour of Reinforced Concrete Beams by Using Expanded Polystyrene Beads and Palm Oil Fuel Ash as Replacement Materials

The Reinforced Concrete (RC) beams containing Expanded Polystyrene Beads (EPS) and Palm Oil Fuel Ash (POFA) as sand and cement replacement with a percentage between 10% and 30% were studied in terms of load-deflection behaviour. RC beam’s size was 1000×150×150 mm and simply supported at spaced 750 mm apart. The 10% of POFA without EPS shows a slight increase which is 0.26% higher than normal concrete in compressive strength. The ultimate load and flexural performance of RC beams with EPS and POFA exhibited a decreasing trend. All beams’ ultimate load exceeds the design value. The cracks of the RC beam may be classified as vertical flexural cracks, and some of the cracks can be classified as shear cracks based on the crack angle. As the percentage of EPS and POFA increases above 20% for all specimens, cracking starts to change to shear cracking.

Time-varying reliability models for parallel systems consisting of beam structures with crack flaws

Abstract. Time-varying reliability assessment of parallel systems of beam structures with crack defects is of great importance for structural safety evaluation. In this paper, time-varying reliability models for parallel systems with cracked beams are proposed. In the modeling process, the statistical correlation between crack depth, random working load, random strength degradation, and random stress response as well as the complex failure correlation jointly caused by these factors are considered. Based on the finite element analysis of the cracked beams, the reliability models are constructed by combining the neural network and the response surface agent model. The validity of the model is verified by the Monte Carlo simulation method. The results show that crack depth and working load dispersion have important effects on reliability and failure correlation.

Free Vibration of Axially Loaded Functionally Graded Porous Cracked Beams

This study employed a method of analysis to examine the free oscillation behavior of functionally graded (FG) porous-cracked beams under axial loads and varied boundary conditions. The cracked beam system was composed of interconnecting beam segments kept together by massless rotating springs. Based on the Timoshenko beam theory (TBT) or Euler–Bernoulli theories (EBT), each segment was sectionally flexible. Using a power-law function, mechanical features were expected to gradually change along with the height of the beam. Two different pore distributions, even and uneven, were also explored. Subsequently, Hamilton’s theory was used to derive the equations of kinematic motion for FG-cracked porous beams, and the transfer matrix (TMM) approach was used to get the determinantal equation. A parametric analysis was performed to evaluate how cracks, porosity distribution, slenderness ratio, volume fraction index, boundary conditions, and axial load affect the dynamic characteristics of FG beams. The results revealed that the suggested analytical approach provided several findings that were similar to the existing analytical outcomes in the literature. Moreover, the computer analysis demonstrated that porosity, especially when there were cracks, significantly affected the eigenfrequencies of FG beams. Hence, this study opened the door for possible applications in a variety of engineering settings by offering some crucial insights into the complex dynamics of FG porous-cracked beams.

Generalized method for distributed detection and quantification of cracks in bridges

The development of a generalized machine learning approach based on distributed detection and quantification of cracks by optical fibers is described in this article. A Brillouin scattering optical fiber sensor system was employed to develop, test, and verify the method. The main components of the approach described herein consist of an unsupervised crack identification module based on the iForest algorithm and a crack quantification component by the one-dimensional convolutional neural network method. The main attribute of this model is the versatility for application in various types of structures. The proposed method does not require further application-dependent training or calibration as long as the structural applications employ the same optical fiber type and installation adhesives. The effectiveness of the proposed method was verified by two experiments involving a 15-m steel beam in the laboratory and monitoring a twin set of 332-m-long, five-span continuous box girder concrete bridges. Regarding crack detection capabilities, it was possible to detect 107 out of 112 cracks in the laboratory beam and 20 out of the 21 in the bridges. The resolution of crack opening displacements for the steel beam and concrete bridges were 20.6 and 21.7 µm, respectively. The verification experiments further indicated the generality of the approach in applications to various types of structures and materials.