Initial Cracking Load Research Articles

Enhancing concrete beam performance with PVA fibers, coal ash, and graphene fabric: a comprehensive structural analysis

ABSTRACT This study evaluates the structural performance of Polyvinyl Alcohol Cementitious Composites (PVCC)-layered reinforced concrete beams with coal ash under static loading. Experimental investigations included first crack load, ultimate load, load-deflection behavior, ductility, stiffness, and energy absorption. Results highlight the influence of Polyvinyl Alcohol-(PVA) fiber dosage on structural behavior. The control specimen exhibited an initial crack load of 80kN, with subsequent specimens showing varied crack initiation loads influenced by PVA fiber content. Optimal performance was observed at 1.2% PVA fiber dosage, with higher dosages leading to earlier crack initiation. Ultimate load carrying capacity increased with PVA fiber addition, reaching a peak at 1.2% dosage before slight decreases occurred with higher dosages. Load-deflection behavior demonstrated the superior performance of PVCC layered beams, particularly specimen BP3, attributed to optimal fiber content. Ductility, stiffness, and energy absorption increased with PVA fiber reinforcement, with 1.2% dosage yielding optimal results. Excessive fiber content led to diminishing returns. Energy index analysis revealed superior energy dissipation in specimens with higher PVA fiber content, emphasizing the effectiveness of fiber reinforcement in enhancing structural performance. Overall, the study underscores the importance of optimizing PVA fiber dosage to maximize structural resilience and load-bearing capacity in PVCC-layered concrete beams with coal ash.

Effect of shear span-to-depth ratio on flexural and fracture behaviors of reinforced UHPMC beams based on four-point bending test and acoustic emission monitoring

Ultra-high performance manufactured sand concrete (UHPMC), using manufactured sand (MS) as aggregate, belongs to a brand-new ultra-high performance concrete (UHPC). Better understanding the failure behavior of UHPMC beams reinforced with steel reinforcement bars is crucial in structural design. This study investigates the effects of different shear span-to-depth ratios (λ = 1.2, 1.6 and 2.0) on the failure modes, mid-span deflection, concrete and rebar strain, flexural toughness, initial cracking load, ultimate load, energy dissipation capacity, and crack propagation patterns based on four-point bending tests for totally twelve reinforced UHPMC beams. Meanwhile, acoustic emission (AE) monitoring is used to evaluate corresponding fracture characteristics. Results reveal that an increase in shear span-to-depth ratio leads to a significant increase in mid-span strain and better ductility but lower equivalent stiffness. The maximum strain of specimen with λ = 1.2 is 24.8 % lower than that with λ = 2.0, and specimen with λ = 1.6 exhibits 22.3 % greater equivalent stiffness than that with λ = 2.0. Beams with larger shear span-to-depth ratios demonstrate superior ductility and energy absorption capacity, specimen with λ = 2.0 showing a ductility factor 2.85 times higher than that with λ = 1.2. The presence of MS significantly improves initial cracking load by 26.9 %, ultimate load by 4.5 %, and energy dissipation capacity by 37 %. MS also enhances toughness and delays crack propagation in the early stages. This effect can make the fracture transform into more rapid energy release in the later stages, indicating that MS could alter crack propagation patterns, forcing cracks to propagate along paths with greater resistance to crack propagation. These conclusions can offer insights for the safer and economical design and application of UHPMC beams, especially the balance among shear span-to-depth ratio, MS and mechanical performance in the environmentally friendly structures design and failure prevention process.

Fracture properties of mixed mode I-II cracks in concrete after sustained loading

To investigate the fracture properties of mixed mode I-II cracks in concrete after sustained loading, the basic creep tests were conducted on concrete beams with five initial mode mixity ratios under three-point bending (TPB) loading or four-point shearing (FPS) loading, two sustained load levels, 80 % of the initial cracking load and the initial cracking load, for a period of 90 days. After creep tests, the specimens were unloaded and immediately loaded up to failure under the quasi-static TPB/FPS loading. Meanwhile, the entire crack propagation process was monitored using the digital image correlation technique. The numerical simulations based on the Norton-Bailey creep model were conducted to capture the time-dependent mechanical response of concrete under sustained loading. The experimental and numerical results showed that the pre-crack did not initiate in the creep tests unless the applied sustained loading exceeded the initial cracking load observed under quasi-static loading. It can be attributed to the viscoelastic characteristics of the concrete, which caused a decrease in the average stress around the pre-crack tip. A load increment was necessary to compensate for the reduced stress, resulting in an increase in the initial cracking load and the crack resistance of the structures. Moreover, sustained loading showed no significant effect on the peak load, fracture angle, initial cracking angle and crack propagation path. It suggests that sustained loading primarily induced a viscoelastic response of the concrete around the pre-crack tip rather than promoting extensive crack growth. Therefore, it is reasonable to approximate crack propagation paths of the concrete after sustained loading by considering the paths observed under quasi-static loading.

Full-scale test on the mechanical behavior of longitudinal joints of NC-UHPC composite segments under compression-bending load

The performance of longitudinal joints in shield tunnel segments is crucial for ensuring structural stability and durability. This study presents an innovative segment structure combining normal concrete (NC) and ultra-high performance concrete (UHPC) (hereafter called NC-UHPC composite segment). Full-scale joint tests were conducted to analyze the mechanical response and failure characteristics of longitudinal joints in these segments. Compared to reinforced concrete (RC) segment joints, NC-UHPC composite segment joints exhibited a significant increase in initial cracking load by 197.93% under sagging moments and 435.3% under hogging moments. The ultimate load-bearing capacity increased by 55.71% and 67.10%, and the initial bending stiffness improved by 20.57% and 10.59% under sagging and hogging moments, respectively. Furthermore, NC-UHPC composite segment joints exhibited smaller crack distribution areas and fewer cracks, indicating superior crack resistance. No cracks or damage were observed at the NC-UHPC interface. Evaluation of joint toughness and ductility indices further highlighted the favorable performance of NC-UHPC composite segment joints. Finally, a refined numerical model was established to compare the deflection and bending stiffness of RC segment joints with NC-UHPC composite segment joints under varying axial forces. The findings suggest that NC-UHPC composite segments are more suitable for tunnel engineering with greater burial depth, higher water pressure, and larger axial forces.

Flexural behavior of RC beams strengthened with CFRP grid-reinforced engineering cementitious composite

Flexural strengthening of RC beams by replacing the tension part with carbon fiber reinforced polymer (CFRP) grid‐reinforced engineering cementitious composite (ECC) matrix has been proved to be a reliable way in the marine environments. However, few studies have been conducted on the arrangement of CFRP grids so far, which is supposed to be a possible way to deal with the premature fracture of CFRP grid and debonding of strengthening layer. In this paper, the flexural behavior of RC beams strengthened with CFRP grid‐reinforced ECC matrix is experimentally studied. The location of CFRP grid and the number of CFRP grid layers were specially discussed. Results from experiments indicated an improvement range of 66.67 %∼100 % in the peak load of strengthened RC beams, with a higher initial cracking load from 4.72 %∼20.47 % when compared to the reference beam. The generating of initial cracks was delayed with the CFRP grid close to the bottom, whereas the development of cracks was accelerated. The bearing capacity showed a nonlinear relationship with the distance from CFRP grid to the beam bottom, and a linear relationship with the number of CFRP grid layers. Finally, the formulas for the flexural capacity of strengthened beams were developed, considering the plasticity and cracking of concrete.

Evaluation method of tunnel cracking disease under biased pressure based on enhanced image fractal features

This paper focuses on the tunnel cracking disease under biased pressure. Through model tests on three lining conditions, the study investigates the expansion process of surface cracks on the lining under biased pressure. Proposing an improved method for calculating fractal characteristics of lining crack disease based on box counting dimension. Quantifying crack disease through digital image processing to obtain two parameters: total width and fractal dimension. Discussed the relationship between quantification parameters of surface crack disease in linings and the service performance of the lining. 29 groups of crack disease quantization parameters obtained by model test were selected to establish the disease sample space, and the spatial data were automatically learned and grouped based on clustering method. Finally, a new diagnostic Index of Tunnel Lining Defect Index-Crack & Dimension (TLDI-C&D) and its disease classification criteria for the whole lining ring are proposed. The results indicate that under the biased pressure, regardless of the presence of pre-existing defects, the biased pressure region is the most severely diseased area in terms of cracking. Compared to the intact lining, the initial cracking loads for arch crown defects and arch waist defects are advanced by 33.1 % and 73.0 %, respectively. After the apparent cracks in the lining are fully formed, pre-existing defects no longer affect the speed and distribution of crack propagation.The larger the fractal dimension, the more complex the morphology of the corresponding crack disease. Under the same image area, the ratio of crack quantity to width has a greater impact on the fractal dimension. There is a corresponding relationship between quantification parameters of crack disease and the bearing performance of the lining structure, making them indicators for measuring the load-bearing capacity of the lining. The most reasonable grading level for lining crack disease under the biased pressure is four levels. The diagnostic index for tunnel lining cracks, TLDI-C&D is 1.0～2.2 (level I), 2.2～3.2 (level II), 3.2～4.3 (level III), and 4.3～5.5 (level IV). On-site measurements have proven the accuracy of this crack disease diagnostic evaluation method.

Indirect Tensile Strength Test on Heterogeneous Rock Using Square Plate Sample with a Circular Hole

Abstract An indirect testing method for determining the tensile strength of rock-like heterogeneous materials is proposed. The realistic failure process analysis method, which can consider material inhomogeneity, is applied to model the failure process of the square plate containing a circular hole under uniaxial compression. The influence of plate thickness and applied loads on the maximum tensile stress is investigated, and the tensile strength equation is deduced. Meanwhile, the initial cracking loads are obtained by the corresponding physical tests, and the tensile strengths are determined by substituting the initial cracking loads into the developed tensile strength equation. The values predicted by the newly proposed method are almost identical to those of the direct tensile tests. Furthermore, the proposed method can give the relatively small tensile strength error with the direct tensile test in comparison to the other test methods, which indicates that the proposed method is effective and valid for determining the tensile strength of rock-like heterogeneous materials.

Shear behavior of circular concrete short columns reinforced with GFRP longitudinal bars and CFRP grid stirrups

Although fiber-reinforced polymer (FRP) reinforcements have become popular, the post-pultrusion bending leads to significant deficiency in bent portions of FRP hoops and spirals. This study adopts flexible carbon FRP (CFRP) grids as stirrups, and investigates the shear behavior of circular short columns reinforced with GFRP bars and CFRP grid stirrups. Six specimens with different shear reinforcement ratios, axial load ratios and types of stirrups (CFRP grids and steel hoops) were tested to shear failures. The failure modes, crack and strain developments, and shear load-horizontal displacement responses were presented for discussion. All specimens experienced shear-compression failures, and the critical diagonal crack widths increased approximately linearly with shear loads. The typical shear load-horizontal displacement curve consisted of three branches: a linear elastic branch, a cracking branch with progressive slope deteriorations, and an almost flat failure branch. Increasing CFRP grid stirrup ratio could not only enhance strength and ductility performance, but also alleviate the slope degradations, while increasing axial load ratios could enhance the initial cracking loads, restrain crack propagations, and reduce the lateral displacements. In terms of strength performance, steel hoops could be replaced by CFRP grid stirrups even with smaller stirrup ratio. Additionally, analytical investigations suggested that the effective stresses and strains of CFRP grid stirrups at failure may be lower than code limits.

The Effect of Load Steps and Initial Crack Length on Stress Distribution of Fiber Metal Laminates

Fiber Metal Laminates (FMLs) are advanced composite materials composed of alternating layers of fiber-reinforced composites and metal sheets, offering a unique blend of high strength, stiffness, and fatigue resistance. Understanding the behavior of FMLs under different loading conditions, particularly in the presence of initial cracks, is crucial for predicting their structural integrity and performance. This study investigates the effect of initial crack length and load steps on the stress distribution within FML structures through numerical simulation. A glass fiber-reinforced epoxy (GFRE) composite is constituted by glass fibers in off-axis directions of 0o/90o. The crack length of 3 mm, 6 mm, 9 mm, and 12 mm is initially defined on the side of fiber metal laminates. The tensile load was gradually applied to the laminates for five different ratios. The ratios are defined by dividing the tensile load with the area of the laminates which is then called stress ratio. The results show that the greater the initial crack length and load step ratio, the greater the stress around the crack tip. The stress distribution in each layer of the laminates shows different characteristics between tensile and compressive. This will affect the crack propagation behavior of the laminates. Moreover, the findings also provide valuable insights for optimizing FML design, improving damage tolerance, and extending service life in diverse engineering applications.

Failure characteristics and seismic behavior of steel basalt hybrid fiber reinforced concrete lining for the tunnel in strong earthquake areas

The effect of a high-intensity earthquake on a tunnel can be catastrophic. To minimize the damage of the earthquake to the tunnel, the mechanical properties of tunnel lining need to be improved in strong earthquake areas. Thereby, this paper proposes a steel basalt hybrid fiber reinforced concrete (SBHFRC) as an alternative construction material for the lining. Then, the failure characteristics and seismic performance of SBHFRC are studied and compared with that of plain concrete (PC) and steel fiber reinforced concrete (SFRC). The results show that the toughness of SFRC is better than that of SBHFRC. Furthermore, the initial crack load and failure load of SBHFRC lining are significantly higher than that of PC lining. The numbers of cracks observed in the SBHFRC lining and SFRC lining are more than that in the PC lining. But the distribution of cracks in SBHFRC lining is relatively uniform. The bearing capacity of SFRC lining and SBHFRC lining is basically the same, although significantly higher than that of PC lining. The seismic performance of different fiber concrete linings is further explored through numerical simulation. Under strong earthquakes, the damage areas of the lining are mainly concentrated at the tunnel vault bottom and vault near the fault, and the SBHFRC damage degree and range are the smallest. Compared with PC lining, the minimum safety factors of SFRC lining and SBHFRC lining are increased by 7.5 times and 11.2 times, respectively, which shows that SBHFRC lining has good seismic performance.

Numerical method for predicting first crack load on hollow-cored beams subjected to point load at Midspan

Predicting the initial crack load in concrete is important to detect early warning of a problem. In this study, a model for predicting the first crack load on a hollow-cored rectangular beam point loaded at mid-span was developed by combining a numerical method and an experimental approach. The modulus of rupture was introduced into the governing moment-curvature relationship. Experimentally, flexural testing with point loads at mid-span was performed on fifteen (15) beams made up of three (3) beam types at 1 kN intervals for a span of 750mm using the Universal Testing machine. The beams were simply supported by roller points. The dimensions of the beams were kept constant and later varied while investigating the following hollow diameters: 0, 30, 60, 75, and 105mm. Numerically, the beams were designed as a beam element point loaded at mid-span with a span of 700mm centers, and the support conditions were defined as pinned support. Governing equations relating failure load with the modulus of rupture, stiffness matrix, shape functions, and moment of inertia were developed. The equation for predicting the first crack load, incorporating the modulus of rupture, was derived. The moment of inertia was calculated by discretizing the hollow-cored beam section using an isoparametric geometric transformation. The experimental results were used to validate the numerical model. 90.55% agreement between experimental and numerical results was observed. The overall average percentage difference between the two methods recorded is 9.45%. This shows that at about 91% confidence level, both approaches are the same and can be applied with confidence in the prediction of the first crack load on hollow- cored reinforced concrete beams.

Prediction of crack initiation for notched concrete beam from FPZ at maximum load

The initial cracking load (Pi) of a notched concrete beam, difficult to measure, has been predicted from the maximum fracture load (Pmax) together with the notch-tip fracture process zone (FPZ) at Pmax. A simple analytical model is used to link Pi and Pmax together through the FPZ. The corresponding initiation and unstable fracture toughness, Ki and Kun, have also been determined. The model assumes that the lower limit of Pmax from a group of identical notched concrete beams corresponds to the lower limit of the FPZ length FPZL, so that the lowest limit Pmax = Pi is established for FPZL = 0. Detailed FPZ measurements before and at Pmax using a digital image correlation technique were analysed and used to predict the initial cracking load Pi. Six different specimens with various sizes (W = 40, 60 and 80 mm), initial notches (a0 = 12 to 48 mm) and FPZL (7 to 13 mm) at Pmax showed the average ratio of FPZL/(W – a0) was around 0.25, indicating the Pi/Pmax ratio was around 0.67 based on the analytical model. The crack growth resistance KR-curve between the crack initiation toughness Ki at Pi and the unstable fracture toughness Kun at Pmax was also established approximately by the simple model. Estimated intrinsic fracture toughness KIC was compared with Ki and Kun. The influence of average aggregate size dav on Pi and FPZL at Pmax was also discussed.

The effects of pre-loading on structural behavior of reinforced concrete beams under fire condition: a review

PurposeThis review paper seeks to enhance knowledge of how pre-loading affects reinforced concrete (RC) beams under fire. It investigates key factors like deflection and load capacity to understand pre-loading's role in replicating RC beams' actual responses to fire, aiming to improve fire testing protocols and structural fire engineering design.Design/methodology/approachThis review systematically aggregates data from existing literature on the fire response of RC beams, comparing scenarios with (WP) and without pre-loading (WOP). Through statistical tools like the two-tailed t-test and Mann–Whitney U-test, it assesses deflection extremes. The study further examines structural responses, including flexural and shear behavior, ultimate load capacity, post-yield behavior, stiffness degradation and failure modes. The approach concludes with a statistical forecast of ideal pre-load levels to elevate experimental precision and enhance fire safety standards.FindingsThe review concludes that pre-loading profoundly affects the fire response of RC beams, suggesting a 35%–65% structural capacity range for realistic simulations. The review also recommended the initial crack load as an alternative metric for determining the pre-loading impact. Crucially, it highlights that pre-loading not only influences the fire response but also significantly alters the overall structural behavior of the RC beams.Originality/valueThe review advances structural fire engineering with an in-depth analysis of pre-loading's impact on RC beams during fire exposure, establishing a validated pre-load range through thorough statistical analysis and examination of previous research. It refines experimental methodologies and structural design accuracy, ultimately bolstering fire safety protocols.

Effect of Textile Layers and Hydroxypropyl Methylcellulose on Flexural Behavior of TRLC Thin Plates

To examine the flexural toughness characteristics of textile-reinforced lightweight aggregate concrete (TRLC), a four-point bending test was conducted to assess the impact of varying numbers of textile layers and the inclusion of hydroxypropyl methylcellulose on the ultimate load-bearing capacity and deformation capacity of TRLC thin plates. Six groups of specimens were prepared for the experiment, and the bending capacity of the thin plates in each group was evaluated. The flexural toughness index was utilized to quantify the bending performance of TRLC thin plates. The findings revealed that increasing the number of textile layers improved the initial cracking load, initial cracking deflection, ultimate load, ductility, and flexural toughness of the thin plates. For the specimens without HPMC, the initial cracking load was increased by up to 36.1%, the ultimate load by up to 40.9%, and the flexural toughness index by up to 292% as the number of textile layers was increased. For specimens doped with HPMC, the initial cracking load was increased by up to 61.7%, the ultimate load by up to 246.7%, and the flexural toughness index by up to 65%. The TRLC thin plate containing hydroxypropyl methylcellulose exhibited a reduced initial cracking load yet displayed a stronger matrix consistency and good flexural toughness. Moreover, the enhancement in the ultimate load of TRLC thin plates with hydroxypropyl methylcellulose was more pronounced with an increased number of textile layers, resulting in a significantly higher number of cracks compared to TRLC without hydroxypropyl methylcellulose and an 11.40-fold increase in the flexural toughness index.

Influence of shear strengthening of reinforced normal concrete beams incorporating sustainable materials

AbstractThis research studies shear strengthening performance for Normal Concrete (NC) beams employing Engineered Cementitious Composite (ECC) reinforced with Galvanized Welded Wire Mesh (GWWM) in conjunction with/without a prestressing system. Six full‐scale Reinforced Concrete (RC) beams were experimented under static monotonic loading at critical shear span zone up to collapse. The investigated factors were: the type and technique of strengthening, materials used for strengthening, and size and configuration of shear reinforcement. Two techniques were introduced: ECC layer reinforced with GWWM and pretensioned steel bars recovered by ECC with one GWWM. GWWM with and without pretensioned steel bars were delivered as shear reinforcement for strengthening. Vertical and inclined steel bars were the two configurations selected for the prestressing technique for suppressing shear stress. The study was discussed through the experimented beams' crack load and pattern, collapse mode, elastic stiffness, absorbed energy, initial cracking load, and ultimate load, along with the corresponding defection. Experimental results showed that both exploited techniques could govern crack patterns, enhance the failure mode, and upgrade ultimate loading capacity up to 52%. Finite element models were built up, simulating those strengthened with an ECC covering layer augmented with GWWM extracting a model with an error of about 3%.

Experimental investigation of rubberized concrete slab-on-grade containing tire-recycled steel fibers

The current study investigates the role of recycled steel fiber (RSF) and crumb rubber (CR) in the fracture behavior of rubberized reinforced concrete (RRC) slab-on-grade in terms of load–deflection responses, crack patterns, failure loads, deflection values, and toughness. RRC slab-on-grade measuring 1000 m × 1000 mm with a thickness of 60 mm were tested experimentally, and the soil was simulated with a steel model. The main parameters were the incorporation of CR as fine aggregate (i.e., 0%, 10%, and 20%) in the presence of RSF (0 and 0.5% by vol). The findings showed that a significant increase in the initial crack load of RRC slabs as compared to the reference slab, as well as slabs incorporated with high volumes of CR, showed favorable findings in post-cracking capacity and toughness compared to the reference slab. The incorporation of CR with 05% RSF can enhance the failure cracking load of concrete slabs by 12.79% (10%) and 20.97% (20%) at the center of the slab. The reference slab-on-grade failure load reached 43.0 kN, while the failure loads for the slabs containing 10% and 20% CR were 43.0 kN and 38.70 kN, respectively, without the addition of RSF. It was noticed that the slab deflection increased by 12.28% and 20.13%, respectively, compared to the reference slab. Finally, the slabs incorporating 0.5% RSF and 20% CR achieved a maximum failure load of 52.03 kN, which was attained because of additional microcracks forming closer to the loaded region, which enhanced the ductility of the slab-on-grade. Hence, the RSF and CR can be used to produce sustainable slab-on-grade with enhanced ductility, leading to a reduced overall cost and saving natural resources.

Splitting Tensile Strength Analysis of High-Strength Concrete Using Ureolytic Bacteria from Local Landfill as Microbial Self-Healing

High-strength concrete is a brittle material due to its low tensile strength. Splitting tensile strength of concrete can be used to determine the concrete tensile capacity. High-strength concrete has high bearing capacity and good durability during its service life but excessive loads and extreme environmental influences can reduce its strength, thus, early maintenance is needed. Efforts that can be made are applying self-healing concrete using ureolytic bacteria obtained from local landfill Gampong Jawa, Banda Aceh, namely Bacillus sp. Splitting tensile strength test of concrete was carried out using cylindrical specimen with diameter 15 cm and height 30 cm. Bacillus sp. bacteria can produce calcium carbonate (CaCO3) as concrete crack-healing with the help of precursors, i.e., urea and Ca2+ ion along with nutrient broth as their nutrients. To ensure better bacterial viability, the bacteria along with their precursors and nutrients were encapsulated with diatomaceous earth and then coated with cement paste. Variations used are the concentration of bacteria along with their precursors and nutrients, i.e., 1.27%, 1.53%, and 1.79% from cement weight. To activate the CaCO3 formation by bacteria, the specimens were cracked first with a load of approximately 40% of its splitting tensile strength after being soaked in water for 7 days, then soaked again in water for 28 days for crack-healing before being tested. Splitting tensile strength analysis showed that the higher the concentration of Bacillus sp. bacteria, the greater the difference of splitting tensile strength between initial cracking load and after self-healing treatment, which indicates better crack-healing efficacy.

Determination of SIFs and application of a SIF-based fracture criterion for concrete-rock interface under sustained loading

This study proposes an effective method to determine the stress intensity factors (SIFs) of the interface crack considering the viscoelasticities of the bilateral materials and verifies the feasibility of the initial fracture toughness-based fracture criterion for the concrete-rock interface under sustained loading. Firstly, low-level sustained loading tests were conducted on the composite concrete-rock specimens with respect to two interface roughness degrees and two sustained load levels less than the initial cracking load. Then, an implicit creep equation was employed to characterise the viscoelasticities of bilateral materials and then calculate the mechanical responses of the concrete-rock interface in the low-level sustained loading test. The SIFs of the interface crack under sustained loading were determined by using the elastic strain energy density ahead of the crack tip. By averaging the SIFs over the radius of the core region of the crack tip, the representative SIFs under sustained loading were obtained. The test results indicated that the SIFs showed decreasing tendencies under sustained loading, and the initial fracture toughness can be considered as a material property of the concrete-rock interface. The initial fracture toughness-based fracture criterion was verified to be feasible to determine the initial cracking status of the concrete-rock interface under sustained loading. In addition, due to the reductions of the SIFs under sustained loading, additional loads were required to compensate the losses of the SIFs, leading to the enhancement of the initial cracking loads after experiencing the sustained loading.

Numerical Investigation on Crack Propagation of Three-Dimensional Pipeline Under Seismic Wave Loading

Cracks in transport pipelines significantly impact their structural safety, making pipeline fracture damage a major concern. While experimental tests can study crack growth, their setup and costs are substantial. To address this, our work involves parametric analyses to investigate the effects of initial crack length, load types and sizes, and pipe wall thickness on the crack tip stress field. The finite element model is established according to the actual operation, and the crack defects of the pipe are established by the extended finite element method (XFEM). The crack tip variation is studied by extracting the von Mises stress and strain at the crack tip. When the crack propagates, the stress field at the crack tip will fluctuate in a certain range. The relationship between stress field fluctuation and crack propagation was studied by changing the XFEM crack growth for comparative analysis. Utilizing 429 numerical results obtained from a parametric numerical model implemented with Python and Abaqus, we establish a back propagation (BP) neural network prediction model to forecast the stress field at the crack tip. The relative errors between the numerical results and the predictions by our model remain below 5%. In conclusion, our proposed approach for analyzing pipeline fracture under multiple loads proves valuable for pipeline safety assessment, and it offers useful insights for evaluating the suitability of transportation pipelines.

Performance of light weight ferrocement composite walls

The aim of this research is to examine the performance of reinforced lightweight ferrocement walls under vertical and horizontal loading. The walls were made up of two thin layers of ferrocement reinforced with one, two, three, or four layers of welded wire mesh or expanded steel mesh. The panels’ core was constructed of lightweight extruded foam. An experimental program of thirteen lightweight walls with total dimensions of 100x650x1250 mm was casted to achieve this goal and tested until failure. ABAQUS finite-element package was conducted. The parameters in this study were the kind of reinforcement; welded and expanded wire meshes, the steel bars, and. the number of layers of steel mesh. Ultimate load, mode of failure, initial cracking load, service load, energy absorption, and ductility ratio were calculated and observation to evaluate the findings. The findings displayed that the performance of the ferrocement walls reinforced with expanded wire meshes is better than that of the walls reinforced with welded wire meshes. The energy absorbed increased by 40 % for specimens reinforced with expanded wire meshes is more than that of the walls reinforced with welded wire a good agreement was observed among the theoretical and experimental observations. This paper highlights uses of employing light weight ferrocement units in building of economic housing, which is particularly valuable for both developed and developing nations, with significant frugal benefits.