In-plane Behavior Research Articles

Flexural behaviour of Q1100 ultra high strength steel welded I-sections

An experimental and numerical program investigating the in-plane flexural behaviour of Q1100 ultra high strength steel (UHSS) welded I-sections is presented in the current paper. The testing program comprised of material coupon tests, measurements of residual stresses, and in-plane 3-point bending tests. Subsequently, a numerical program was executed, involving the development of finite element (FE) models. The FE models validated against the experiments were subsequently employed for parametric studies, aiming at assessing the flexural behaviour of Q1100 welded I-sections across a broader spectrum of section geometries. The data obtained from the experiments and numerical simulations were used to assess the applicability of prevailing design provisions outlined in the European, Chinese and Australian codes for high-strength steel structures. These design provisions encompass classification limits for cross-sections and predicted methods for cross-sectional resistance in bending. Via reliability analyses, adjustments were made to the cross-section classification limits. Finally, a modified direct strength method was proposed to predict the in-plane bending resistance for Q1100 welded I-sections.

In-Plane Cyclic Behaviour Comparison of Adobe Wall Retrofitted by Mortar Enhanced by Physical and Chemical Methods

ABSTRACT A mortar overlay on damaged adobe masonry is employed for its load carrying capacity improvement and low skill requirement. Nevertheless, delamination between the adobe wall and mortar has been commonly observed due to bonding failure. Physical enhancement (groove, shear dowel, and wire mesh) and chemical enhancement (a novel biological and traditional Chinese binder, sticky rice pulp, SRP) are carried out to enhance the bonding between mortar and adobe. The high-moisture adsorption mortar is also utilized to alleviate water accumulation resulting from the application of mortar on earthen buildings. Four adobe walls with different retrofitting methods are subjected to in-plane lateral cyclic loading tests to analyse the failure mode, hysteretic load-displacement response, skeleton curve, ductility behaviour, energy dissipation and stiffness degradation. It indicates that the retrofitting effectiveness of adobe walls coated only with mortars is limited, as their peak load increases are comparatively modest compared to other retrofit wall systems. However, employing additional bonding enhancement methods significantly enhances the peak load capacity. Specifically, a combination of physical and chemical enhancements results in a remarkable 114% increase on the positive side and an astonishing 500.1% increase on the negative side.

Advantages of using DIC for capturing mechanical shear sliding behaviour of the FRCM strengthened masonry

This paper aims to analyse the advantages of using Digital Image Correlation (DIC) method to capture the effects of the FRCM on masonry wall shear failure. In the scientific literature, most of the experimental programs is focused on strengthening against flexural failure by means of bending tests and against shear, diagonal cracking, by means of diagonal compression tests. The shear failures are one of the main failure modes for the in-plane behaviour of masonry walls in case of horizontal loads. This study primarily focuses on experimentally determining the capacity of clay brick masonry under sliding shear loads for different normal stress levels with a standard test method. The assessment of shear capacity is based on a Mohr-Coulomb failure criterion depending on the external axial load, the internal friction angle and the cohesion values for unreinforced masonry. The experimental tests have been carried out on both unreinforced and strengthened specimens. The results of the tests demonstrate that FRCM, despite the reduced anchorage length in the tests, can significantly enhance the structural performance of masonry structures for sliding shear failure mode. In addition, DIC method is used to analyse, in greater detail, the cracks and the strain evolution in order to analyse the failure of specimens.

Characterization and Modeling of Out-of-Plane Behavior of Fiber-Based Materials: Numerical Illustration of Wrinkle in Deep Drawing.

The characterization and modeling of the out-of-plane behavior of fiber-based materials is essential for understanding their mechanical properties and improving their performance in various applications, especially in the forming process. Despite this, research on paper and paperboard has mainly focused on its in-plane behavior rather than its out-of-plane behavior. However, for accurate material characterization and modeling, it is critical to consider the out-of-plane behavior. In particular, delamination occurs during forming processes such as creasing, folding, and deep drawing. In this study, three material models for paperboard are presented: a single all-material continuum model and two composite models using different cohesion methods. The two composite models decouple in-plane and out-of-plane behavior and consist of continuum models describing the behavior of individual layers and cohesive interface models connecting the layers. Material characterization experiments are performed to derive the model parameters and verify the models. The models are validated using three-point bending and bulge tests and show good agreement. A case study is also conducted on the application of the three models in the simulation of a deep drawing process with respect to wrinkle formation. By comparing the simulation results of wrinkle formation in the deep drawing process, the composite models, especially the cohesive interface composite model, show greater accuracy in replicating the experimental results, indicating that a single continuum model can also be used to represent wrinkles.

Experimental and numerical investigation on the in-plane performance of nail-laminated timber floor

Existing research has shown that the nail-laminated timber (NLT) floor has the potential to achieve considerable out-of-plane flexural performance at a relatively lower cost. However, though the in-plane performance of structural floors greatly impacts the seismic resistance of the overall structure, research on the in-plane behavior of NLT floors is still insufficient. In this paper, an in-plane shear test was carried out on twelve NLT floor specimens of four subgroups. A finite element model (FEM) method was established and verified using the experimental results. A parametric analysis was performed based on the FEM method to quantify the influence of sheathing nails on the in-plane performance of the NLT floor in both planar directions. Experimental results indicate that sheathing nail spacing and loading direction showed significant influence on the in-plane performance of NLT, while the orientation of sheathing did not. Main failure modes include dislocation of adjacent sheathings, sheathing nail failure, and lamina nail failure. Verification of the proposed FEM method showed good agreement with the experimental results, both on performance characteristics and deformation patterns. Parametric result indicates that the elastic stiffness and shear strength were linearly correlated to the quantity of sheathing nails.

In-plane biaxial low-cycle dwell fatigue behavior of CP-Ti based on DIC method

This study investigates the biaxial dwell fatigue behavior of commercial pure titanium (CP-Ti) under different load ratios and dwell times. The evolution of mean strain, ratcheting strain, and creep strain was systematically analyzed. The findings reveal that with the decrease of load ratio or the increase of dwell time, both ratcheting and creep strain exhibit an upward trend. The interaction between ratcheting strain and creep strain promotes crack initiation and propagation. The statistical analysis of crack paths by the digital image correlation (DIC) method indicates that crack initiation occurs between 0.7Nf and 0.8Nf, and fatigue failure is governed by the maximum principal strain. Moreover, the electron backscatter diffraction (EBSD) analysis results indicate that as the load ratio increases, the activity of prismatic slip systems decreases, while the activities of other slip systems and twinning modes increases. To enhance predictive accuracy, a modified SWT model by incorporating time-dependent creep damage and anisotropy is proposed for life prediction under biaxial dwell fatigue conditions.

In-plane flexural behavior of eccentric rectangular hollow section (ERHS) X-joints: Experimental, numerical and analytical study

This paper investigates the in-plane flexural behavior of an eccentric rectangular hollow section (ERHS) X-joint, where the two braces are continuous at one side and the inner face is aligned with a chord sidewall. The presented X-joints are full lateral offset RHS joints. In this study, laboratory static testing is implemented on two ERHS X-joint specimens and one traditional RHS X-joint specimen under in-plane bending moment (IPBM), and the corresponding numerical simulation is conducted. The results show that the ultimate flexural strength and initial stiffness of the ERHS X-joints with a medium brace-to-chord width ratio (β) are larger than those of the RHS X-joints. The initial stiffness and strength of ERHS X-joints increase with the growth of β. Based on the load transferring mechanism, two analytical models and the relevant formulae are proposed to predict the strength of the ERHS X-joints with β ≤ 0.925 and β = 1.0, and the strength of joints with 0.925 <β < 1.0 can be determined by linear interpolation. The proposed analytical models are validated against experimental data and finite element results.

In-plane compressive behavior of cross-laminated bamboo and timber with variable heights

This paper investigates the in-plane compressive behavior of 5-layer cross-laminated bamboo and timber (CLBT) wall elements with variable heights. Five different heights of CLBT specimens, ranging 400 mm – 3800 mm, were designed for the experiment, with conventional 5-layer cross-laminated timber (CLT) specimens used as controls. Theoretical calculations based on timber structure design codes were employed to analyze the ultimate bearing capacity in compression, complemented by finite element simulations based on Abaqus that also explored the failure characteristics. The results indicated that CLBT wall panels had significantly better compressive performance compared to those of CLT wall panels. For wall panels of around 3.0 m and 6.0 m in height, the compressive strength of the CLBT was approximately 65 % and 40 % higher than that of the CLT, respectively. For specimens showing buckling instability, CLBT demonstrated more concentrated failure in the end regions, contrasting with CLT, which failed primarily in the central region. The outcomes of this study clearly delineate the superiority of CLBT over CLT when used as wall panels, providing valuable references for their potential engineering applications.

Bending behaviors of carbon fiber composite honeycomb cores with various in-plane stiffness

Designing curved surfaces with a traditional straight-walled honeycomb is challenging due to its excessive in-plane stiffness, making it prone to fracturing during bending. The research motivation is overcoming the flexibility limitation of conventional straight-wall honeycombs with the new curved-wall design. Moreover, the three-dimensional failure mechanism map based on the theoretical models is expected to contribute to the design of a carbon fiber composite curved-wall honeycomb. This paper outlines the fabrication process using a modified co-curing method. It also includes theoretical models developed to examine the effect of the center angle of curved walls on the honeycomb’s in-plane stiffness and bending behavior. In-plane tensile and three-point bending tests were conducted to verify the theoretical modes. Finite element model was created to study the stress distribution and damage degree. The study is also aimed at examining the load-bearing capacity of sandwich beams with curved-wall honeycomb cores. A three-dimensional failure mechanism map shows how the failure modes of sandwich structures are affected by the center angle of the curved walls. The study offers a new approach to designing carbon fiber composite honeycombs with flexible bending deformation and high load-bearing capacity. These honeycombs could potentially be used in lightweight launch-vehicle shell structures.

Constitutive description of distortional hardening in a TWIP steel: Addressing differential hardening under nonlinear strain paths

The present study aims to describe the in-plane differential hardening behaviour of the twinning induced plasticity sheet metal TWIP980 under various stress states, including uniaxial tension, plane strain tension, and pure shear, particularly focusing on non-proportional loading conditions. The true stress–strain curves for each stress states were inversely obtained from their corresponding load–displacement curves and modeled using a differential hardening model that can accommodate all three stress states simultaneously on plastic work (density) contours. For non-proportional loading tests, oversize specimens were initially stretched under uniaxial tension up to a 10% pre-strain along the rolling, diagonal, and transverse directions, respectively. Subsequently, the three stress states were applied to subsize specimens cut from the deformed oversize specimens along the rolling direction. To describe the hardening behaviours during non-proportional loading, a homogeneous anisotropic hardening model was adopted and calibrated using two-step uniaxial tension tests. Subsequently, the differential hardening model was successfully incorporated into the homogeneous anisotropic hardening model to describe both the differential hardening and the strain path change-induced hardening behaviours under the two-step loadings, i.e., uniaxial tension to pure shear and uniaxial tension to plane strain tension. Both experimental and simulation results underscore the necessity to consider differential hardening under non-proportional loading conditions.

Effective properties of masonry structures and macro-model analysis with experimental verification

Masonry structures are the most prevalent type of buildings worldwide, and a significant portion are situated in seismic-prone areas. Thus, detailed information regarding their seismic strength and vulnerability is needed. The complexity of studying masonry structures lies in defining accurate and efficient models for representing masonry walls. In this context, there is a need for simplified methods that allow the modeling of masonry walls within a 3D structure. This work presents a methodology to define effective masonry properties from numerical analyses on representative volumes, using a damage model informed by experimental tests on units and mortar. These effective material properties serve as input parameters to model masonry walls within a macro-model approach, aiming to accurately capture the in-plane behavior and damage mechanisms with limited computational cost. The methodology is verified with experimental results and applied to real case studies in Cuenca, Ecuador.

In-plane deformation behavior and energy absorption characteristics of a straight-arc coupled auxetic metamaterial inspired by arch bridges

The microstructure and material properties of auxetic honeycomb metamaterials significantly influence their deformation behavior and energy absorption. Inspired by the arch bridge, new types of straight-arc coupled structure (SACS) and the reverse SACS (R-SACS) auxetic metamaterials are designed to enhance the energy absorption capacity (EAC). The quasi-static compression and dynamic impact responses of honeycomb metamaterials are studied numerically under large deformation. A theoretical model is further developed to estimate the average platform stress (σp) of the R-SACS honeycomb, which is verified by the numerical results. For R-SACS--3 with Nylon 12 and Al-alloy, the relative errors of the finite element model compared with the theoretical model are − 5.56 % and − 3.21 %, respectively. Two kinds of basic materials, Nylon 12 and Al-alloy, are employed to analyze the deformation mode of the SACS and R-SACS honeycomb with the same geometric parameters under quasi-static load and impact load. The influence of basic material is discussed, and the structure with Al-alloy exhibits more stability owing to segmented deformation. The creation of additional plastic angles shows an improved σp and specific energy absorption (SEA) compared to the re-entrant structure (RES). σp and SEA of SACS are both 1.3 times as much as those of RES. The peak stress of the R-SACS cellular metamaterial is always smaller than the SACS under impact load, and the maximum reduction is 63 %, which has better a buffering effect.

Study on the Shear Behaviors and Capacity of Double-Sided Concrete-Encased Composite Steel Plate Shear Walls by Experiment and Finite Element Analysis

Concrete-encased composite plate shear walls (C-PSW/CEs) can realize the in-plane shear yielding of infill steel plate with the buckling restrained from the concrete panel. Concrete panels also additionally resist portions of lateral loading in C-PSW/CEs, whereby the shear stiffness and strength of the C-PSW/CE are improved. However, research on the in-plane behaviors of concrete panels and the interactions between structural elements is limited. In this paper, the mechanical characteristics and the interactions and the shear resistances of C-PSW/CEs with double-sided concrete encasements were studied. First, the effects of concrete thickness on the damage process, steel plate buckling, and shear resistances of C-PSW/CEs under lateral loading were tested. Then, finite element analyses of the internal forces of the horizontal and inclined cross-sections and the shear force–drift ratio responses of C-PSW/CEs were undertaken with the extended finite element method (XFEM) to simulate the cracking behaviors of concrete panels. A shear force–drift ratio model based on mechanics was developed by considering the lateral load resistances of concrete panels and their effects on steel plates in C-PSW/CEs.

Influence of Confining Element Stiffness on the In-Plane Seismic Performance of Confined Masonry Walls.

Confined masonry (CM) construction is being increasingly adopted for its cost-effectiveness and simplicity, particularly in seismic zones. Despite its known benefits, limited research exists on how the stiffness of confining elements influences the in-plane behavior of CM. This study conducted a comprehensive parametric analysis using experimentally validated numerical models of single-wythe, squat CM wall panels under quasi-static reverse cyclic loading. Various cross-sections and reinforcement ratios were examined to assess the impact of the confining element stiffness on the deformation response, the cracking mechanism, and the hysteretic behavior. The key findings included the observation of symmetrical hysteresis in experimental CM panels under cyclic loading, with a peak lateral strength of 114.3 kN and 108.5 kN in push-and-pull load cycles against 1.7% and 1.3% drift indexes, respectively. A finite element (FE) model was developed based on a simplified micro-modeling approach, demonstrating a maximum discrepancy of 2.6% in the peak lateral load strength and 5.4% in the initial stiffness compared to the experimental results. The parametric study revealed significant improvements in the initial stiffness and seismic strength with increased depth and reinforcement in the confining elements. For instance, a 35% increase in the lateral strength was observed when the depth of the confining columns was augmented from 150 mm to 300 mm. Similarly, increasing the steel reinforcement percentage from 0.17% to 0.78% resulted in a 16.5% enhancement in the seismic strength. These findings highlight the critical role of the stiffness of confining elements in enhancing the seismic performance of CM walls. This study provides valuable design insights for optimizing CM construction in seismic-prone areas, particularly regarding the effects of confining element dimensions and reinforcement ratios on the structural resilience.

Determination of the In-Plane Behavior of Masonry Walls Using the Truss Model

ABSTRACT The diverse characteristics of masonry structures make it difficult to determine their behavior. The development of numerical methodologies using various approaches and assumptions reflects the need for adaptable methods to accommodate these diverse structures. This study focuses on a novel simplified approach for analyzing masonry walls. The proposed method uses truss elements with a well-known theoretical background to elucidate the load-bearing capacity, damage formation and its causative factors, and failure mechanics of masonry piers within a plane. Five masonry wall samples from three different studies were used to validate the accuracy of the proposed approach. Pushover analyses were performed using software with nonlinear analysis capabilities, which was developed in the Python programming language. Consequently, the obtained results were compared with the literature data. This method provides initial expectations such as simplification and consistency, making it a potential alternative for the preliminary assessment of masonry structures.

A 3D pilot simulation of masonry walls retrofitted with steel strips using a novel meso-scale damage-plasticity interface model

A novel interface model is introduced to faithfully and effectively simulate masonry walls retrofitted with steel strips (MWSS) under monotonic/cyclic lateral loads at the meso-scale level, where bricks and mortar joints are explicitly represented by 3D continuum elements and interface elements, respectively. The interface model’s formulation, rooted in a damage-plasticity framework, is presented herein, which allows for an accurate depiction of the complex nonlinear behaviors of masonry joints under tension, shear and compression. Subsequently, the model is calibrated and verified against existing experimental data from large-scale masonry specimens subjected to monotonic/cyclic lateral loading. The resulting push-over/hysteretic curves, along with the failure modes of the specimens, show relatively good agreement with their experimental counterparts. Leveraging this validated modelling approach, an extensive parametric study is undertaken to assess the impact of various factors on the in-plane behavior of MWSS. It turns out that the boundary conditions dictate the overall response of MWSS, whereas the material properties of the masonry have relatively minor effects. Given these insights, an improved truss-based analytical model is suggested to predict the lateral strength of MWSS, addressing the limitations of existing design procedures, particularly in scenarios where MWSS’s top edge is confined by high pre-compression.

In-plane shear failure behavior and mechanical properties of SiC/SiC Composites

Fiber-reinforced ceramic matrix composites, especially SiC/SiC composites, have the characteristics of lightweight, high strength, high-temperature resistance, etc., which are ideal structural candidates for aerospace vehicle components, in-plane shear performance is one of the important indicators to characterize the mechanical properties of materials and component assessment, this paper designs and processes the in-plane shear test pieces and test devices and methods to study the shear mechanical behavior under the mechanical properties and failure behavior of SiC/SiC ceramic-based fiber bundle composites are studied under shear mechanical behavior. The results show that matrix cracking and fiber fracture are the main failure modes, and there are two obvious phases in the specimen shear force-displacement curves, and fiber fracture is the main cause of strain in the specimen.

A macroscale damage model for the tensile and bending failure of C/C-SiC structural laminates

This work presents a Finite Element approach to model the in-plane mechanical behavior of C/C-SiC fabrics at the lamina level, including the non-linear response of diverse lay-ups and the bending-to-tensile strength ratio at failure. The material model employs a decomposition into two idealized phases, which can be exploited to capture matrix- and fiber-dominated responses at a high level of abstraction. The constitutive law of the matrix phase adopts a Continuum Damage approach driven by two Tsai-Wu surfaces, while a quasi-brittle behavior is attributed to the fibers phase. This decomposition effectively represents the influence of matrix degradation on the response and failure of the laminates. Moreover, simulations reveal that a statistical distribution of the strength is required to represent some of the experimental outcomes. The correlation with experimental data that was achieved points out that the technique is a promising tool for supporting the early design phase of CMC structures.

Temperature- and rate-dependent tensile behaviour of unidirectional carbon/polyamide-6 composite under off-axis loading with oblique tabs

Unidirectional carbon/polyamide-6 (CPA6) is a thermoplastic composite with attractive properties for many industrial applications. However, shortage of experimental data may hinder the development of reliable material models. This paper is the first to provide a complete dataset for the tensile behaviour of unidirectional CPA6, including the longitudinal, transverse, in-plane shear, and off-axis response, at different temperatures and (quasi-static) strain rates. The oblique end tab design, already proven in the literature for off-axis testing of composites at room temperature, was successfully extended to the elevated temperature of 120 °C. The use of cardboard tabs and fast-curing adhesive greatly simplified the tab manufacturing and application for all the combinations of fibre angles, temperatures and strain rates. Digital image correlation (DIC) was performed through the window of the temperature chamber to verify the homogeneous strain field produced by the oblique tabs. The in-plane shear behaviour was extracted from the off-axis tests, allowing to estimate the shear modulus and shear strength. Finally, the robustness of the experimental results generated in this study was demonstrated with well-established analytical models that could excellently predict the elastic modulus, Poisson's ratio, and failure stress at different fibre angles.

In-plane testing and hysteretic modeling of steel-spline cross-laminated timber diaphragm connection with self-tapping screws

ABSTRACT This study examines experimentally and numerically the in-plane behavior of a steel-spline Cross-Laminated Timber (CLT) connection with self-tapping screws. Although this connection is a strong, rapid, and cost-effective alternative suitable for CLT diaphragms of tall timber-concrete buildings, no previous cyclic/monotonic testing has been documented. Two specimens were tested under axial and in-plane shear loads, where a ductile failure mode was observed due to bending and withdrawal of screws, and deformation and buckling of the strap. Mechanic properties, such as strength capacity, stiffness, ductility, energy dissipation, equivalent viscous damping, stiffness/strength degradation, and damage index characterize the joint. Furthermore, the yield point and ductility were calculated with the EEEP, CEN, and Yasumura–Kawai methods, the last approach most accurate, with a mean ductility of 7.25 and 5.50 for the axial and in-plane shear tests, respectively. Overstrength factors of about 2.6 and 1.9 were also estimated for respective tests by comparing analytical expressions from timber codes and literature. Finally, three numerical models (SAWS, DowelType, and ASPID) were assessed to measure their epistemic uncertainty, showing an adequate force and dissipated energy history simulation, with a normalized root mean square less than 8.8% and 4.5%, and R 2 over 87% and 97%, respectively.