Load Deflection Research Articles

Joint Performance in Bonded Concrete Overlays of Asphalt

Bonded concrete overlays of asphalt pavements (BCOA), also known as whitetopping, consist of a thin concrete overlay on distressed asphalt or composite pavements. They typically have smaller panel sizes than traditional jointed plain concrete pavements (JPCP) in order to reduce stress levels. Faulting at the transverse joints is a distress in BCOA that is not currently addressed in current design procedures. The pumping mechanism that leads to this distress is the focus of this paper. Pumping in BCOA can develop at either the bottom of the overlay slab within the asphalt layer or at the bottom of the asphalt in the granular layer. It is essential to identify where the faulting initiates for each pavement structure, if accurate faulting models are to be developed for these pavement structures. An examination was conducted of 21 BCOAs located at the Minnesota Road Research Facility (MnROAD) to investigate how faulting initiates in BCOA and the rate at which it develops. To do this, the relationship between deflection load transfer efficiency (LTE) from falling weight deflectometer (FWD) testing and transverse joint faulting was examined. It was found that these parameters can be used in successfully defining when faulting initiates at the top of the asphalt and when it initiates at the top of the granular layer below the asphalt. Finally, the rate of the development of faulting in BCOAs resulting from pumping at the concrete/asphalt interface as well as pumping below the asphalt layer was compared to faulting predictions using current models. A good agreement between the observed and predicted faulting was not achieved.

ANALYSIS OF FULL-DEPTH PCC PATCHES FOR JOINTED CONCRETE PAVEMENTS

This study investigates the effectiveness of full-depth Portland Cement Concrete (PCC) patches for rehabilitating jointed concrete pavements, focusing on load transfer efficiency, stress distribution, and deflection characteristics under heavy axle loads. The deterioration of jointed PCC pavements, primarily at transverse contraction joints due to heavy traffic and environmental conditions, necessitates maintenance strategies like Concrete Pavement Restoration (CPR) which includes full-depth patching among other techniques. The research emphasizes the importance of dowel bar size, spacing, and concrete thickness in the design of full-depth patches to ensure effective load transfer and minimize pavement deflections and stresses. Key findings reveal that deflections along transverse joints increase with fewer dowel bars, while joint efficiency improves with thicker slabs and more dowel bars. Tensile stresses were found to be less influenced by the number and size of dowel bars, not exceeding rupture limits, indicating stresses alone are insufficient for patch design. The study highlighted that bearing stresses are critical, with six and seven dowel bars configurations exceeding allowable stresses, suggesting that a minimum of eight dowel bars of at least 1 1/4-inch diameter is necessary for effective design. The optimum design proposed involves a 10-inch thick patch with eight dowel bars positioned strategically across the transverse joint for improved load transfer and reduced bearing stress, thus enhancing pavement longevity and performance. (Abstract generated by AI tool ChatGPT 4)

Structural Performance of Reinforced Concrete Beams with Steel Fibres as Secondary Reinforcement: Experimental and Pre-peak Numerical Modelling

This research consists of an experimental and a numerical investigation into improving the structural performance of reinforced concrete (RC) beams by incorporating hooked-end steel fibres. Experimentally, steel fibres were added to the concrete matrix of 80 mm × 180 mm × 1500 mm RC beams with fibre contents of 0%, 0.5%, and 1%, without replacing traditional reinforcement bars. Each beam underwent a four-point flexural test using a hydraulic press under static loading to evaluate the influence of fibres on flexural behaviour. The numerical analysis aimed to model the macro-scale flexural behaviour of RC beams using a 3D finite element approach in ABAQUS. Challenges in modelling steel fibres include their discrete nature and computational demands due to intricate meshing and convergence issues. The Simplified Concrete Damaged Plasticity Model was used to characterize the compressive and tensile behaviours of plain and steel fibre reinforced concretes. Nonlinear finite element analysis was performed to predict pre-peak load versus mid-span deflection and crack propagation. The model, which does not explicitly simulate steel fibres, was validated against experimental data, showing strong agreement and confirming its effectiveness in capturing the flexural behaviour of steel fibre reinforced concrete beams. Experiments Results showed that steel fibres enhance the flexural performance. Beams with steel fibres exhibited higher first crack loads, ultimate loads, flexural strengths, and toughness. Additionally, the fibres increased crack numbers, reduced crack spacing and length, and improved post-cracking behaviour. The simulation results were subsequently validated against experimental data. The results of the numerical finite element analysis were in good agreement with those of the experiments.

Comparative Analysis of Small Deflection Behavior in Cantilever Beams Using Structural Steel and Aluminum Alloy

This research investigates the deflection change of cantilever beams made of structural steel (S355) and aluminium alloy (6061) under small deflection conditions. The main objective is to compare their performance in several aspects of load carrying capacity, deflection and safety systems through theoretical calculations and Finite Element Analysis (FEA). The research highlights that S355 exhibits higher stiffness and lower deflection compared to 6061 under the same load. However, 6061 demonstrates a higher safety factor, making it more suitable for applications where lightweight and safety margins are prioritized. The results provide insights into material selection for structural and mechanical applications, particularly where trade-offs between deflection and safety must be considered.

Experimental and Numerical Analysis of Shear Performance of 16 m Full-Scale Prestressed Hollow Core Slabs

To investigate the shear performance of 16 m span prestressed hollow core slabs, shear tests were conducted on three pre-tensioned prestressed hollow core slabs with the same shear-to-span ratio. A systematic analysis was performed on the failure modes, crack development patterns, load–deflection relationships, and load–strain relationships of the prestressed hollow slabs. The test results indicate that all specimens experienced shear-compression failure under the same shear-to-span ratio (2.71). The main diagonal shear cracks were distributed within a range of 1.35 m to 1.95 m from the beam ends, with crack angles approximately between 45° and 55°. Finite element software ABAQUS was used for detailed numerical simulation of the tests. By comparing the failure modes and load–displacement curves, the reliability and applicability of the finite element model were verified.

Flexural and Shear Strengthening of High-Strength Concrete Beams Using near Surface Basalt Fiber Bars

Strengthening of reinforced concrete (RC) structures has become a primary challenge in civil engineering. Different materials and procedures have been used in order to repair or strengthen RC structures. In this research, the NSM-Basalt Bar (NSM-BFRP) technique was used to strengthen high-strength reinforced concrete beams in flexure and shear. Twelve beams were designed, constructed, and tested under four-point loads. Six of them were designed to have insufficient longitudinal steel reinforcement to make sure that the failure would be a flexural failure in the control beam. Whereas, the other six specimens were designed to have insufficient transverse steel reinforcement to make sure that the failure will be a shear failure in the control beam. All RC beams were strengthened using NSM-BFRP with different configurations except control specimens. The load deflection curve, the cracking pattern and the failure mode were evaluated. The experimental results reveal that NSM-BFRP bars significantly enhance the ultimate load capacity of high-strength concrete beams, with flexural capacity improvements of up to 33.33% and shear capacity enhancements of up to 63.5%. However, the use of BFRP bars also led to a shift in failure modes from flexural to shear, particularly in specimens with increased flexural reinforcement. The findings suggest that while NSM-BFRP bars are highly effective in strengthening concrete beams, careful consideration of the reinforcement configuration is necessary to avoid premature shear failure and ensure balanced structural performance.

An experimental and numerical evaluation of the structural performance of bamboo-reinforced concrete beams

The global shift toward sustainable construction calls for eco-friendly alternatives to traditional materials. While steel reinforcement in concrete offers high strength and durability, it has significant environmental and economic drawbacks. Bamboo, a fast-growing and renewable material, is a low-cost, eco-friendly option, but concerns about its structural performance have hindered its widespread use. This study examines the structural performance of concrete beams reinforced with steel (SRC), bamboo (BRC), and hybrid steel-bamboo combinations (HYB-1 and HYB-2). It assesses ultimate failure load, load–deflection curves, failure modes, and crack patterns to explore their viability as sustainable alternatives. Beams measuring 150 × 150 × 750 mm were tested experimentally and simulated using ABAQUS software under three-point bending. SRC beams had the highest ultimate failure load (104.67 kN) and deflection (8.6 mm). BRC beams had the lowest failure load (17.97 kN), a decrease of 82.9% compared to SRC beams. HYB-1 and HYB-2 showed intermediate loads of 87.25 kN and 24.99 kN with a decrease of 16.6% and 76.1% respectively compared to SRC reference samples. Deflection in BRC beams was the least (3.0 mm), while HYB-1 and HYB-2 showed deflections of 7.4 mm and 5.6 mm. The average flexural strength for BRC beams was 82.8% lower than SRC beams, while HYB-1 and HYB-2 showed reductions of 16.9% and 76.1%. The energy absorption capacity of HYB-1 beams was close to SRC beams, with only a 29.1% reduction, while BRC and HYB-2 beams showed a reduction of 92.8% and 87.1% respectively compared to SRC beams. These findings suggest that hybrid configurations, particularly HYB-1, balance structural strength and sustainability Finite element analysis (FEA) closely matched experimental results, with an average difference of 7.44%, validating the accuracy of the modeling.

Analysis on Flexural Performance of Prestressed Steel-Reinforced UHPC Beams

The flexural performance of prestressed steel-reinforced ultra-high-performance concrete (UHPC) beams was investigated through finite element (FE) modeling and nonlinear numerical analysis. Two FE models were established for prestressed steel-reinforced concrete beams and prestressed UHPC beams, respectively, and the accuracy was validated by comparing with the experimental results. On this basis, a comprehensive analysis of load–deflection behavior, load–strain relationships, and failure modes was conducted under varying parameters, including reinforcement ratio, prestress level, steel web thickness, and steel flange thickness. The results indicate that an increase in reinforcement ratio from 1.17% to 1.90% enhanced the ultimate load by 12.05%, while increasing the prestress level from 0.61 to 0.76 improved the cracking load by 114.88% and the ultimate load by 53.73%. Moreover, the beams exhibited superior ductility and cracking resistance compared to conventional concrete structures. A formula for predicting the flexural capacity of prestressed steel-reinforced UHPC beams was derived, showing an average error of less than 3% when compared with FE simulations. This formula provides a reliable basis for the structural design and optimization of high-performance composite beams in engineering practice.

Enhancing Mechanical Properties of Alkali-Activated Slag SIFCON for Sustainable Construction Using Recycled Glass and Tire-Derived Waste Steel Fibers

This paper presents the outcomes of a study in which continuous steel fibers, recovered from scrap tires of vehicles, were used to prepare alkali-activated slag-based slurry infiltrated fibrous concrete (SIFCON). In this experimental study, the steel fibers used were 250 mm long, with varying fiber contents of 0%, 1%, 2%, 3%, 4%, and 5%. The alkali-activated SIFCONs were produced by activating ground granulated blast furnace slag (GGBS) with a mixture of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) solutions. Mixtures with ordinary Portland cement (OPC) were also cast for comparison purposes. The feasibility of utilizing finely ground waste glass as a silicate source for chemical activator solution in alkali-activated SIFCONs was also investigated. In this context, two different molar concentrations of NaOH, namely 8 M and 14 M, were employed during production. As activators, one series of mixtures utilized sodium hydroxide and sodium silicate solutions, while the other series replaced sodium silicate with finely ground waste glass. As a result, three different waste materials were utilized in concrete. 30 different mixtures were cast and examined in the experimental study. Load–deflection curves were obtained in three-point bending test and mechanical properties of the mixtures such as compressive, splitting and flexural strengths, fracture energy, and toughness were determined. The flexural strength and toughness increased with the use of waste steel fibers. The continuous waste fibers derived from discarded tires yielded results comparable to commercially available fibers, demonstrating their effectiveness in enhancing mechanical properties. Depending on mix design, the alkali-activated SIFCON attained flexural strength exceeding 75 MPa and compressive strength surpassing 100 MPa. These results suggest that concretes incorporating a variety of waste materials can be effectively combined. This innovative approach bridges an existing gap in the literature by combining alkali activation, waste glass, and waste steel fibers, ultimately yielding a sustainable composite that outperforms normal concretes in terms of mechanical properties while promoting environmental sustainability. Test results demonstrate that it is possible to obtain concrete with comparable mechanical properties while primarily composed of by-products and waste materials. This approach marks a substantial step in achieving high-performance concrete that relies solely on waste or by-products.Graphical

Response of the beam-base system to a sudden change in the modulus of elasticity of the beam material

A mathematical model of the dynamic process excited in a statically loaded beam-base system by a sudden change in the beam's bending rigidity is constructed. It is assumed that either the beam material's elastic modulus or the beam's cross-sectional axial moment of inertia changes when it is rotated by 90 degrees relative to the beam's longitudinal axis while maintaining the load direction. Forced vibrations are investigated by decomposing the load and static deflection of the initial beam into rows according to the beam's natural vibration modes with changed parameters. Natural frequencies and corresponding displacement and bending moment modes are determined by the initial parameter method using a vector-matrix representation of the states of arbitrary beam sections. Numerical results are provided to demonstrate the capabilities of the approach.

Recycled coarse aggregate concrete and its application in CFRP reinforced concrete beam

This paper deals with performance of concrete by using recycled coarse aggregate (RCA) to replace 30%, 50%, and 70% of natural coarse aggregate. Three concrete types were studied: Group A using RCA with 10% of silica fume (SF) addition by weight of cement, Group B using RCA with 30% of fly ash (FA) substitution by weight of cement, and the control concrete without RCA, SF, FA. Group A demonstrated a considerable improvement in compressive strength whereas group B exhibited a noticeable reduction, in comparison to the control concrete. Secondly, three reinforced concrete beams, representing three concrete types, strengthened with carbon fiber reinforced polymer (CFRP) sheet were tested under a three-point bending fixture. All the flexural parameters of the tested beam, including load bearing capacity, deflection capacity, stiffness, ductility, and crack patterns were evaluated and discussed. Finally, an analytical model was suggested to estimate moment and shear resistance of the beams.

Biomechanical Analysis of Camellia oleifera Branches for Optimized Vibratory Harvesting

To investigate the biomechanical properties of Camellia oleifera branches under two loading speeds within a specific diameter range, three-point bending tests were conducted using a universal material–testing machine. The tests were performed at loading speeds of 10 mm/min and 20 mm/min on branches with diameters ranging from 5 mm to 40 mm. This study aims to provide insights into the design of a manipulator gripper used in a vibrating harvester for Camellia oleifera fruit. Four main varieties of Camellia oleifera were tested to determine their elastic modulus. The nonlinear least squares method, based on the hyperbolic tangent function, was employed to fit the bending load–deflection curves of the branches. This process constructed multi-parameter transcendental equations involving elastic modulus, diameter, and loading speed. Results indicated that the branches of four Camellia oleifera varieties exhibited significant differences in their biomechanical properties, with their modulus of elasticity ranging from 459.01 MPa to 983.33 MPa. This suggests variability in the bending performance among different varieties. For instance, Huaxin branches demonstrated the highest rigidity, while Huashuo branches were softer in general. For the proposed empirical fitting equations, when the fitting parameter k is 168 ± 20 and the parameter c is 3.102 ± 0.421, the bending load–deflection relationship of the branches can be predicted more accurately. This study provides a theoretical basis for enhancing the efficiency of mechanized vibratory picking of Camellia oleifera and optimising the design of the gripper.

Mechanical Behavior Research on IHB-CFRP Anchorage Scheme to Reinforce the Flexural Performance of Concrete Beams

This article investigates the use of Carbon Fiber Reinforced Polymer (CFRP) plates with additional anchors to enhance reinforced concrete slab beam structure. A test proposes an improved additional anchorage measure to solve the debonding problem during anchoring. Three point bending load test are carried out to analyze the influence of different anchoring positions on the reinforcement effect. An optimized Improved Hybrid Bonding CFRP (IHB-CFRP) additional anchoring measure is given. The shear friction model proposed in the IHB-CFRP anchoring scheme can simulate the additional adhesion resistance well. The article investigates the concrete crack extension, load–deflection relation, the strain distribution of CFRP plate, CFRP and concrete interface shear stress. It can be seen that the IHB-CFRP anchoring scheme improves the interface bonding ability and bearing capacity of the reinforced specimen.

Reinforcement of RC Two-Way Slabs with CFRP Laminates: Plastic Limit Method for Carbon Emissions and Deformation Control

Carbon-fiber-reinforced polymer (CFRP) laminates have gained attention for their potential to reduce carbon emissions in construction. The impact of carbon-fiber-reinforced polymer (CFRP Laminate) on carbon emissions and the influence of elasto-plastic analysis on this technique were studied in this research. This study focuses on how CFRP can affect the environmental footprint of reinforced concrete structures and how elasto-plastic analysis contributes to optimizing this strengthening method. Four flat RC slabs were created to evaluate this technique in strengthening. One slab was used as a reference without strengthening, while the other three were externally strengthened with CFRP. The slabs, which were identical in terms of their overall (length, width, and thickness) as well as their flexural steel reinforcement, were subjected to concentrated patch load until they failed. The strength of two-way RC slabs was analyzed using a concrete plastic damage constitutive model (CDP). Additionally, CFRP strips were applied to the tension surface of existing RC slabs to improve their strength. The load–deflection curves obtained from the simulations closely match the experimental data, demonstrating the validity and accuracy of the model. Strengthening concrete slabs with CFRP sheets reduced central deflection by 17.68% and crack width by 40%, while increasing the cracking load by 97.73% and the ultimate load capacity by 134.02%. However, it also led to a 15.47% increase in CO2 emissions. Also, the numerical results show that increasing the strengthening ratio significantly impacts shear strength and damage percentage.

Design and load deflection analysis of large capacity load ball screws

Design and load deflection analysis of large capacity load ball screws

A flexibility approach for geometric nonlinear static analysis of guyed masts

The present study proposes a novel flexibility-based approach for the large displacement analysis of guyed masts. The guyed mast is modeled as an equivalent beam–column supported by catenary cables, and the exact force–displacement relations of sagging cables and slender beam–column are accounted for with sufficient rigor. The proposed method starts with formulating two mutually exclusive sets of second-order force–displacement equations, one for the mast and the other for the cables. Flexibility matrices are derived in an incremental form for an Euler–Bernoulli beam–column using the well-known Variational Iteration Method (VIM). Since an exact Lagrangian multiplier is used in the correction functional, the displacements obtained from this numerical method are also exact. The cable behavior is studied using Irvine’s model, which is the most accurate and realistic one since it represents the equilibrium configuration of the cable using a catenary curve. But, the model is non-algebraic and is unsuitable for complex structures. Hence, Irvine’s equations are recast into an incremental form to obtain exact incremental flexibility matrices. Then, displacement compatibility is re-established between the mast and the cables at their interfaces. This method can effectively address the eccentric compression on the mast shaft from the supporting guy cables, stay slackening, postbuckling of the mast, and trace the mast’s nonlinear response for large displacements. A multi-level guyed mast is analyzed to demonstrate the practical application of the proposed method. Classic examples of single-level guyed towers are used to illustrate the behavior in the postbuckling and post-slackening region. The sensitivity of a guyed mast to cable prestress levels, as well as mast shaft imperfections, are also discussed. The solved examples are also analyzed using commercial finite element software packages, and comparisons are drawn regarding their accuracy in capturing the load–deflection response under large displacements.

Application of an Instability‐Based Fracture Model for Prediction of Crack Initiation in Modified 9Cr–1Mo Steel

ABSTRACTDuctile fracture of modified 9Cr–1Mo steel was investigated using smooth and notched bar tension tests. Round and flat notched specimens with varying notch acuity ratio were used to investigate the influence of stress state on the fracture strain. Simulations of the experiments were performed using the extended finite element method, together with an instability‐based crack initiation criterion based on the micromechanics of void coalescence. The parameters in the plasticity model were determined using smooth bar tension tests, whereas the void nucleation parameters were calibrated from experiments on a shallow‐notched specimen. Subsequently, the load–deflection responses and strain to crack initiation have been predicted for round and flat notched specimens with various notch acuities, and central notched specimens with notches oriented at various angles to the loading axis. Using a single set of parameters, the model was able to quantitatively predict fracture in different specimen geometries encompassing a range of stress states.

Bending Test of Rectangular High-Strength Steel Fiber-Reinforced Concrete-Filled Steel Tubular Beams with Stiffeners

To better understand the bending performance of rectangular high-strength steel fiber-reinforced concrete (HSFRC)-filled steel tubular (HSFRCFST) beams with internal stiffeners, ten beams were subjected to a four-point bending test. The primary considerations were the strength grade of the HSFRC, the steel fiber content, the internal stiffener type, and the circular hole spacing of the perfobond stiffener. The moment–curvature and flexural load–deflection curves were calculated. The mode of failure and the distribution of cracks of the infill HSFRC were observed. The presence of steel fibers greatly improved the bending stiffness and moment capacity of HSFRCFST beams, with the optimal effect happening at a steel fiber content of 1.2% by volume, according to the experimental findings. The type of stiffener influenced the failure modes of the exterior rectangular steel tube, which were unaffected by the compressive strength of the infill HSFRC. On the tension surface of HSFRCFST beams, the crack spacing of the infill HSFRC was virtually identical to the circular hole spacing of perfobond stiffeners. When the circular hole spacing was between two and three times the diameter, the perfobond stiffener worked best with the infill HSFRC. The test beams’ ductility index was greater than 1.16, indicating good ductility. The test beams’ rotational capacities ranged from 6.26 to 13.20, which were greater than 3.0 and met the requirements of the specification. The experimental results demonstrate that a reasonable design of the steel fiber content and the spacing between circular holes of perfobond stiffeners can significantly improve the bending resistance of rectangular HSFRCFST beams. This provides relevant parameter design suggestions for improving the ductility and bearing capacity of steel fiber-reinforced concrete beams in practical construction. Finally, a design formula for the moment capacity of rectangular HSFRCFST beams with stiffeners is presented, which corresponds well with the experimental findings.

Hybrid Reinforced Concrete Frames with Engineering Cementitious Composites: Experimental and Numerical Investigations

Reinforced concrete (RC) structures are vulnerable to damage under dynamic loads such as earthquakes, necessitating innovative solutions that enhance both performance and sustainability. This study investigates the integration of Engineered Cementitious Composites (ECC) in RC frames to improve ductility, durability, and energy dissipation while considering cost-effectiveness. To achieve this, the partial replacement of concrete with ECC at key structural locations, such as beam–column joints, was explored through experimental testing and numerical simulations. Small-scale beams with varying ECC replacements were tested for failure modes, load–deflection responses, and crack propagation patterns. Additionally, nonlinear quasi-static cyclic and modal analyses were performed on full RC frames, ECC-reinforced frames, and hybrid frames with ECC at the joints. The results demonstrate that ECC reduces the need for shear reinforcement due to its crack-bridging ability, enhances ductility by up to 25% in cyclic loading scenarios, and lowers the formation of plastic hinges, thereby contributing to improved structural resilience. These findings suggest that ECC is a viable, sustainable solution for achieving resilient infrastructure in seismic regions, with an optimal balance between performance and cost.

Structural and Sustainability Enhancement of Composite Sandwich Slab Panels Using Novel Fibre-Reinforced Geopolymer Concrete

One of the important findings of the recent decades in the construction industry is composite sandwich panels (CSPs), which have benefits of being lightweight, providing thermal insulation, and aiding the economy; they are transforming continuously through many add-ons as needed by the industry. With the demand for sustainability in the field, CSPs need structural and sustainable enhancement. In the present study, an approach for the same has been attempted with geopolymer concrete (GPC) and novel nylon fibre to improve the sustainability and structural benefits, respectively. With various material combinations including GPC reinforced with fibres, six CSPs were cast and studied. The inherent limitations of GPC have been addressed by the nylon fibre reinforcement instead of using steel fibres, which have a similar strength, considering the aim of maintaining the density of the wythe material. A comparison of the flexural behaviour of the CSPs through the parameters of load–deflection, ductility, and toughness was made using the four-point loading test. The results of the test specify that the fibres enhance the performance of the CSPs under flexural loading.