Failure Modes Of Specimens Research Articles

Experimental study on the seismic performance of prestressed concrete beams under low-cycle reciprocating load and simulated acid rain corrosion environment

The corrosive environment of acid rain affects the durability of prestressed concrete structures as well as their performance under seismic loading. Therefore, prestressed concrete beams subjected to simulated acid rain corrosion were tested under the low-cyclic loading tests. Many parameters were examined including failure mode, hysteretic behavior, backbone curve, ductility, stiffness degradation, and energy dissipation capacity of specimens at different corrosion degrees, jacking control stress, and concrete strength. Experimental results indicated that prestressed concrete beams all had a similar failure pattern, but the oblique cracks appeared earlier as the corrosion degree increased. The effect of corrosion degree, jacking control stress, and concrete strength on the prestressed concrete beams was minimal during the initial stage of loading, but became increasingly clear after entering the yield stage. It should be noted that the damage degree caused by corrosion time is the most obvious. The shape of the hysteresis loop of the prestressed concrete changed slowly from a shuttle shape to a “Z” shape as the corrosion time increased, and the energy dissipation capacity decreased continuously.

Research on flexural performance of new pipe-roof pre-construction structures

In order to study on the flexural performance of new pipe-roof pre-construction (PRP) structures, an experiment was conducted by taking the setting of connectors and longitudinal reinforcement as parameters in this paper. The crack development and failure mode of specimens were observed, and the load, deflection as well as strain of the specimens were measured. Based on the test results, the stress mechanism of PRP structures was studied, and the influence of connectors and longitudinal reinforcement on the flexural performance of PRP structural members was analyzed. The results show that the failure process and stress mechanism of flexural members in the PRP structure are quite different from that of double steel plate concrete members with constant section height. The failure of flexural members in PRP structures generally occurs at the intersection of steel pipe curtains and steel plates, which is mainly due to the stress concentration caused by the sudden changes of section height. The yield order of the components in the specimen is longitudinal reinforcement, connectors, and steel pipe curtains. Comparing with studs connectors, the bi-steels connectors can more effectively improve the mechanical properties of flexural members in PRP structure. For the specimens with longitudinal reinforcement, the load bearing capacity improved by setting bi-steel connectors is larger than that for specimens without longitudinal reinforcement.

External precast concrete nib beam-to-column connection under elevated temperatures: Experimental and finite element analysis

The precast concrete nib is one of the most widely used beam-to-column connections to address the architectural drawback of the ordinary precast concrete corbel. However, precast concrete nib beam-to-column connections are not classified as fully rigid or pin but exhibit semirigid properties. Semirigid connections are at risk of deflection at lower loads and cracking during early fire events. In this study, full-scale fire tests were carried out to determine the thermal and structural behaviour of the external monolithic and precast concrete nib beam-to-column connections subjected to 120 min standard cellulose fires. A finite element simulation using ANSYS validated the experimental results based on the internal temperature distributions, load–deflection curves, and stress visualization. Results show that the tension reinforcement of the concrete nib specimen at high temperature was below the critical temperature of 300 °C during the 120 min of heating, compared to the monolithic specimen, which reached the critical temperature of 300 °C at 105 min. The crack patterns and failure modes of monolithic and precast concrete nib specimens at high temperatures were more visible than at ambient temperature. Based on the ductility factor and Monforton’s fixity factor, the concrete nib specimen at high temperatures was categorized as structures with limited ductility and classified in Zone I (pin connection), respectively. This study concluded that external precast concrete nib beam-to-column connections were more vulnerable at high temperatures than monolithic connections.

Laboratory investigation into the crack propagation mechanism of geosynthetic reinforced asphalt concrete using digital image correlation technique

ABSTRACT Geosynthetic reinforcement has proven effective in mitigating reflective cracking in new pavement overlays. This study aimed to compare the ability of five different geosynthetic reinforcement products to alleviate cracking in overlays. Each product was sandwiched within a two-layered asphalt concrete (AC) beam specimen and subjected to a four-point notched beam fatigue test. The study monitored crack propagation, understood crack propagation mechanisms, and quantified crack lengths in different geosynthetic-reinforced AC beam specimens during a notched beam fatigue test using the digital image correlation (DIC) technique. The DIC analysis generated full-field displacement and strain contours, depicting the damage mechanisms of geosynthetic reinforcement products in AC overlays under fatigue loading. The quantitative analysis measured the cracked areas caused by each product. The interfacial damage observed in various geosynthetic-reinforced beam specimens under different test conditions suggested that the failure modes of AC beam specimens reinforced with different products varied, and choosing the right product for a project depended on the pavement conditions, geosynthetic product properties, and tack coat properties. Finally, the predictive algorithms presented in this paper allow for predicting the failure mode generated by different geosynthetic products for different overlay conditions in the field, providing valuable insight for pavement engineers.

Experimental and simulation study on compressive failure evolution of multidirectional laminates with different dimensions

The composite strength refers to the ultimate local value rather than the average value of local strength, thus the effect of size effect needs to be considered. In this study, experimental and numerical approaches are used to evaluate the influence of size effect on the compressive characteristics and failure process of multidirectional carbon fiber reinforced composites. The representative failure modes of specimens with different thicknesses are described. The reasons for the difference in failure modes are analyzed by microstructure analysis, and the crack propagation process of specimens with different gauge lengths is identified. The simulation results and microscopic mechanism analysis reveal that with the increase of specimen thickness, the final failure mode develops from longitudinal cracking to multidirectional delamination, and finally evolves into shear failure through the thickness. Influenced by the free edge effect, the specimen thickness significantly affects the final failure mechanism by influencing the location of the initial cracking, and the size of the gauge section affects the site of matrix compression failure leading to a change in the final failure mode. These findings provide some helpful guidance for the design and fabrication of thick composite structures.

Experimental and numerical investigation on failure characteristics and mechanism of coal with different water contents

Water injection, as a widely used technique to prevent coal burst, can restrain the fractured coal seam and released the energy storage. In this study, laboratory tests were firstly carried out on standard coal specimens with five different water contents (i.e., 0%, 0.6%, 1.08%, 1.5%, 2.0%, and 2.3%). The failure mode, fragment size, and energy distribution characteristics of coal specimens were investigated. Experimental results show that strength, elastic strain energy, dissipated energy, brittleness index, as well as impact energy index decrease with increasing water content. Besides, the failure mode transitions gradually from splitting ejection to tensile-shear mixed failure mode as water content increases, and average fragment size shows positively related to water content. Moreover, scanning electron microscope tests results indicate that water in coal sample mainly causes the mineral softening and defects increase. Furthermore, a numerical model containing roadway excavation was established considering the water on coal burst prevention. Modelling results revealed that water injection can reduce degree of coal burst and ejection velocity of coal blocks, while it will raise up the depth of crack zone and surface displacement of roadway. Combined with laboratory tests and numerical results, the micro mechanism, energy mechanism, and engineering significance of water injection on coal burst prevention were finally analyzed.

Effect of the Slit on the Mechanical Tearing Behavior of High-Density Polyethylene and Polyester Geocell Strips

Geocells are widely applied in numerous infrastructure constructions, like heavy-haul railways and ports. The mechanical tearing behavior of a geocell strip is crucial to the stability of the geocell-reinforced soil structures. At present, extensive studies have been conducted on the tensile characteristics of geocell strips, while limited research has been performed to investigate the post-damage mechanical tearing behavior of geocell strips. Meanwhile, there is also a lack of research on the comparison of performance of strips before and after damage. In this paper, a series of trapezoidal tearing tests were performed on high-density polyethylene (HDPE) and polyester (PET) geocell strips. The tearing test results and failure mode of trapezoidal specimens with a slit were investigated, and the effect of the slit on the strength and deformation characteristics of the specimen were discussed by introducing the “damage ratio of tearing force (RTF)” and “damage ratio of tearing displacement (RTD)”. In addition, the mechanical tearing behavior of HDPE and PET trapezoidal specimens was also compared. The test results indicated that the failure mode of HDPE and PET specimens subjected to tearing force was ductile and brittle failure. The strength and deformation characteristics of post-damage HDPE and PET trapezoidal specimens decreased. The slit had a significant impact on the tearing displacement of HDPE and PET specimens, especially the post-peak tearing displacement. The post-peak tearing displacement of HDPE was 10.99 times that of PET. The peak tearing force of the HDPE specimen without the slit was about 1.61 times that of specimen with the slit. Before local tearing, the peak tearing force of the PET specimen without the slit was about 3.27 times that of the specimen with the slit. The strength damage to the HDPE and PET geocell strips caused by the slit was 38.0%, and 69.46%. The impact of the slit on the tearing force of the PET specimen was greater than that of the HDPE, and was 1.82 times for the HDPE. This study can enhance our understanding of the mechanical tearing behavior of the geocell strip after damage and develop effective mitigation measures.

Experimental Study of Shear Performance of High-Strength Concrete Deep Beams with Longitudinal Reinforcement with Anchor Plate.

As a transfer member at the discontinuous place of vertical load, the deep beam has a complex stress mechanism and many influencing factors, such as compressive strength of concrete, shear span ratio, and reinforcement ratio. At the same time, the stress analysis principle of traditional shallow beams is no longer applicable to the design and calculation of deep-beam structure. The main purpose of this paper was to use the strut-and-tie model to analyze its stress mechanism, and to verify the applicability of the model. Nine high-strength concrete deep-beam specimens with longitudinal reinforcement with an anchor plate of the same size were tested by two-point concentrated loading method. The effects of shear span ratio (0.3, 0.6, and 0.9), longitudinal reinforcement ratio (0.67%, 1.05%, and 1.25%), horizontal reinforcement ratio (0.33%, 0.45%, and 0.50%), and stirrup reinforcement ratio (0.25%, 0.33%, and 0.50%) on the failure mode, deflection curve, characteristic load, crack width, steel bar, and concrete strain of the specimens were analyzed. The results showed that the failure mode of deep-beam specimens was diagonal compression failure. The normal section cracking load was about 15 to 20% of the ultimate load, and the inclined section cracking load was about 30~40% of the ultimate load. The shear span ratio increased from 0.3 to 0.9, and the bearing capacity decreased by 32.9%. When the longitudinal reinforcement ratio increased from 0.67% to 1.25%, the ultimate load increased by 42.6%. The shear span ratio and longitudinal reinforcement ratio have a significant effect on the bearing capacity of the high-strength concrete deep beams with longitudinal reinforcement with an anchor plate. The shear capacity of nine high-strength concrete deep-beam specimens with longitudinal reinforcement with an anchor plate was calculated by national standards, and the results were compared with the calculation results of the Tan-Tang model, the Tan-Cheng model, SSTM, and SSSTM. The analysis showed that the softened strut-and-tie model takes into account the softening effect of compressive concrete, and is a more accurate mechanical model, which can be applied to predict the shear capacity of high-strength concrete deep-beam members with longitudinal reinforcement with an anchor plate.

Experimental study of the cyclic behavior of steel tube in concrete‐filled steel tube members

AbstractA concrete‐filled steel tube (CFST) specimen was tested under uniaxial loading to acquire the nonlinear monotonic and cyclic response of the steel tube in CFST members including inelastic cyclic local buckling. The failure mode, hysteretic response, envelope curves, strength, and stiffness degradation of the CFST specimen were comprehensively studied. The observed failure modes of the CFST specimen were local buckling and ductile fracture of the steel tube due to ultra‐low‐cycle fatigue. The effective stress‐strain curve of the steel tube exhibited negative stiffness due to local buckling. The compressive resistance of the CFST specimen decreased significantly when local buckling progressed at the steel tube. The tensile unloading stiffness slightly decreased relative to the elastic stiffness of the CFST specimen; conversely the compressive unloading stiffness experienced severe deterioration upon increased cyclic loading. The tensile stiffness decreased gradually during the whole loading process, while the post‐capping stiffness remained stable.

Quasi-Static tensile loading performance of Bonded, Bolted, and hybrid Bonded-Bolted Carbon-to-Carbon composite Joints: Effect of recycled polystyrene nanofiber interleaving

Although hybrid bolted/bonded (HBB) joints possess each joint technique's benefits, the adhesive layer performance significantly affects the load-carrying capacity of hybrid joints. Nanofiber interleaving has become an efficient solution to improve the adhesion performance of bonded and HBB joints. This paper reveals the effectiveness of polystyrene (PS) nanofibers interleaving on the mechanical properties of adhesively bonded and HBB single lap joints (SLJs). For this purpose, PS nanofibers are produced via electrospinning from wasted polymers as a nature-friendly implementation. The PS nanofiber mats were interleaved between adherends as a reinforcement layer, and specimens were tested under quasi-static tensile loading. A significant improvement was seen in the peak load value of 10% for the HBB joint, and the fracture energy of the bonded joint increased by 15% with PS nanofiber modification. The failure modes of PS-reinforced specimens developed as more gradually progressive compared to neat specimens thanks to the compatibility of the recycled PS nanofiber with the epoxy and improved adhesive layer performance with PS modification. Furthermore, the morphological analyses of post-fracture specimens were monitored to realize the damage and nano-toughness mechanisms.

Experimental study on the tensile performance of a large-diameter UHPC grouted sleeve with thread

An ultra-high-performance concrete (UHPC)-grouted sleeve with a large-diameter seamless steel pipe with threads and bolts was designed. To study the mechanical properties of this grouted sleeve, various factors, such as the grouts type, rebar, thread, and bolts, were considered to conduct a uniaxial tensile test on the grouted sleeve specimens. The bonding performance of the grouted sleeve under a combination of various factors was studied, and its working mechanism was discussed. The results showed that the failure modes of the test sleeve specimens included rebar fracture, rebar slip and grouts slip. The G1 (UHPC without basalt fibre) grouted sleeve showed the best bonding performance and bearing capacity. Bolts and inner wall threads of the sleeve improved the grouts–sleeve bond strength. However, the level of improvement was related to the bolt location, thread spacing and depth. The closer the bolt position was to the elastic section of the sleeve port, the more significant the bond performance improved. The thread could provide mechanical bite force. The greater the thread depth were, the greater the mechanical bite force; nevertheless, there was a threshold. Based on the thick-walled cylinder theory, the calculation model for stress on the sleeve surface was obtained; these calculations were used to analyse the stress–strain law on the sleeve surface.

Experimental and numerical study on structural behavior of reactive powder concrete corbels without stirrups

This paper presents a study that explores the application of reactive powder concrete (RPC), a modern construction material, to corbels without stirrups. The focus of the research is to investigate the shear behaviors of RPC corbels under vertical loading through experimental and numerical methods. Three RPC corbels with different shear span-to-effective depth ratios (av/d) of 0.6, 1.1, and 1.6 were tested. A commercial finite element method (FEM) code was utilized for the numerical analysis, and its accuracy was verified against the experimental results. A parametric study was conducted to evaluate the influence of various factors, including RPC compressive strength, RPC tensile strength, amount of main reinforcement, yield strength of main reinforcement, and stress-strain model of main reinforcement. Additionally, the shear strengths obtained from the tests were compared with the predicted values based on design codes, including ACI 318–14 and NF P18–710. The findings reveal that the av/d ratio significantly affected the load-deflection behaviors and failure modes of the RPC corbel specimens. The numerical model demonstrates good agreement with the experimental results. The RPC compressive strength emerges as the primary factor influencing the peak load of RPC corbels. Comparing various predictions, the Strut-and-Tie models recommended by the NF code exhibit the highest accuracy and safety in estimating the shear strengths of the RPC corbels.

Experimental and numerical studies on shear behavior of prefabricated bridge deck slabs with compact UHPC wet joint

Ultra-high performance concrete (UHPC) as a joint material for precast bridge decks might reduce the width of the joint and improve its connection performance and durability. This study proposes a type of compact UHPC wet joint based on the mechanical properties of UHPC and the force characteristics of transverse joints in prefabricated bridge decks. The shear behavior of the novel joint was investigated through experimental study and numerical simulation. In addition, the shear properties of compact UHPC wet joints were compared with epoxy joints. The results indicated that the shear resistances of compact UHPC joints are comparable to those of epoxy joints. The failure process of the precast bridge deck with new joint might be divided into three stages: elastic stage, working stage with cracks, and yield stage. No interface cracks or reinforcement slippage was observed throughout the loading process, indicating that the UHPC joint and the epoxy joint exhibited adequate shear resistance. The ultimate load capacity and corresponding mid-span deflection of UHPC joint specimens were respectively increased by 8.6 % and 75.0 %, when compared with the epoxy joint specimens. Finite element analysis reveals that the transverse shear transfer range of the compact UHPC joints is within 57.1 %. Bending failure due to the yielding of the transverse reinforcement at the bottom of the precast bridge deck is the primary failure mode for both specimens. Moreover, the stresses applied to the deck system have good continuity at the joint.

Study on failure mechanism of tight sandstone based on moment tensor inversion

Understanding deep rocks' mechanical properties and failure evolution is crucial for efficient resource development. This study investigates the mechanical properties of tight sandstone and analyzes its acoustic emission (AE) characteristics using a combined discrete element model and moment tensor inversion. The AE activity during loading is categorized into three stages: crack initiation, stable crack propagation, and unstable crack propagation. Confining pressure loading suppresses AE activity during the crack initiation stage due to damage healing phenomenon. Moment tensor inversion reveals that tensile failure is the primary AE failure source, despite samples exhibiting splitting and shear failure modes. The proportion of AE failure types varies with stress levels and depends on the mechanical environment. Microcracks initiate at the ends of the sample and propagate inward along the loading direction, resulting in a blank area of AE events in the middle. This blank area can be utilized to predict specimen failure mode. The b value, representing the ratio of small to large magnitude events, decreases with increase of the confining pressure, indicating higher energy release during specimen failure under high confining pressure. The research results can provide a reference for predicting the failure of tight sandstone.

Modelling and design of cold-formed S960 steel brace-rotated tubular T- and X-joints

This paper presents detailed numerical investigation and design of cold-formed S960 steel grade brace-rotated (BR) tubular T- and X-joints. The BR tubular joint is one of the novel bird-beak tubular joint configurations, where the rotation of brace member(s) enhances joint resistance and aesthetic appearance. The numerical investigation was performed through finite element (FE) analysis. The tests carried out by the authors were used to develop accurate FE models of BR T- and X-joints, which in turn precisely replicated the joint resistances, load vs deformation curves and failure modes of test specimens. With an aim to broaden the data size, a comprehensive FE parametric study was performed using the verified FE models. The nominal resistances predicted from the literature and European code were compared to the joint failure resistances of 211 BR T- and X-joints specimens, including 192 FE specimens investigated in this study. The BR T- and X-joint specimens were failed by two failure modes, namely chord face failure (F) mode and a combination of chord face and chord side wall failure mode, i.e. combined failure (F + S) mode. It has been shown that the existing design provisions are unsuitable for the design of cold-formed S960 steel grade BR T- and X-joints investigated in this study. Hence, using three design approaches, accurate, less dispersed, reliable and user-friendly design equations are proposed in this study to estimate the joint failure resistances of cold-formed S960 steel grade BR T- and X-joints.

Dynamic Mechanical Behavior of Rock Specimens with Varying Joint Roughness and Inclination under Impact Load

The influence of joint roughness and inclination on the dynamic mechanical properties of rocks is a prominent research area. In order to investigate the effects of joint roughness and inclination on the dynamic mechanical properties of jointed rocks, impact tests were conducted using a spilt Hopkinson pressure bar (SHPB) apparatus for prefabricated serrated joint cement mortar specimens with varying joint roughness and inclination. The failure mode, stress wave propagation characteristics, peak stress, and stress wave energy transfer law under impact load were analyzed. The results indicate that both joint inclinations and joint roughness coefficients (JRC) have a strong influence on the failure mode, peak stress, and stress wave energy transfer of jointed specimens. The jointed specimens exhibit three distinct failure modes under impact load, namely splitting tensile failure, shear slip failure, and compound failure of splitting tensile and shear. The peak stress initially decreases then increases with the increase in joint inclination angle, namely a V-shape variation, while it gradually increases with JRC increasing from 0 to 20. Jointed specimens exhibit the lowest peak stress at an inclination angle of 45° and JRC of 0. The variation of transmitted energy coefficient is similar to the peak stress, while the variation of reflected energy coefficient is opposite to the peak stress. At joint inclination angles of 0° or 90°, the reflected energy coefficient increases with the increase of JRC from 0 to 20, while the transmitted energy decreases. However, when the joint inclination angle is in the range of 30° to 60°, the reflected energy coefficient gradually decreases with JRC increasing, while the transmitted energy coefficient gradually increases.

Study of the Tensile and Bonding Properties between Cement-Based Grout Materials and High-Strength Bolts

This study investigated the tensile and bonding properties between cement-based grouting materials (CBGM) and high-strength bolts. The associated failure mechanism, load-slip curve, ultimate pull-out load and bond stress were also studied. The effects of anchorage length and square steel tube restraint on the bonding properties were explored on the basis of 24 specimens used in central pull-out testing, and a bond stress–slip constitutive relationship model between high-strength bolts and CBGM was proposed. The results indicate that with the increase in the anchorage length of high-strength bolts, the failure modes of specimens can be divided into three types: the fracture failure of high-strength bolt that occurred when the anchorage lengths ranged from 18 d to 31 d, the specimens that experienced splitting failure with the constraint of square steel tube when the anchorage length was less than 15 d and the high-strength bolt that experienced pull-out failure without the constraint of square steel tubes. When the high-strength bolt experiences tensile failure, the ultimate pull-out load remains constant and the bond stress decreases as the anchorage length of high-strength bolts increases. Due to the lateral constrained effect of the square steel tube, the CBGM embodies a three-dimensional stress state, which can delay the generation and development of internal cracks and enhance the bond strength. A calculation formula was proposed to determine the bond strength between high-strength bolt and CBGM, and a constitutive model of the bond stress–slip constitutive relationship was modeled.

Ultrafine lamellar microstructures for enhancing strength-ductility synergy in high-entropy alloys via severe cold rolling process

In the present study, the effect of severe cold rolling (SCR) on the microstructure and mechanical characteristics of X0.25FeCoNiMnV (X: Al, Ti) high-entropy alloys (HEAs) specimens was investigated. It was observed that the as-cast and homogenized specimens exhibited a two-phase microstructure consisting of face-centered cubic (FCC) and a minor body-centered cubic (BCC) structure. Electron backscattered diffraction (EBSD) analysis indicated that SCR could effectively induce a strong rolling texture with stretched grains along the rolling direction and lamellar deformation bands as the major microstructural features for all the HEAs specimens. Moreover, a large number of nano-scale grains are formed within the coarse-stretched microstructure of Al0.25FeCoNiMnV and Ti0.25FeCoNiMnV HEAs specimens due to local fragmentation, resulting in a bimodal grain structure. After 85 % cold rolling, the fraction of high angle grain boundaries and mean misorientation angle of the boundaries are 54 % and 22.15° in the FeCoNiMnV specimen, while they are 61 % and 26.42° for Al0.25FeCoNiMnV, and 57 % and 28.53° for Ti0.25FeCoNiMnV. Ti0.25FeCoNiMnV specimen exhibited the best combination of strength-ductility (tensile strength of 1225 MPa and elongation of 26 %) compared to FeCoNiMnV (720 MPa and 15 %) and Al0.25FeCoNiMnV (970 MPa and 18 %). Observations revealed that the failure mode of HEAs specimens was a ductile type fracture with a combination of deep and shallow dimples. The findings revealed that SCR can effectively improve the strength and microhardness of HEAs, while it highly retains their elongation owing to the formation of a bimodal structure consisting of new grain boundaries and dislocation substructures.

Experimental investigation on the anisotropy of mode-I fracture and tensile failure of layered shale

Mode-I fracture toughness (KIC) and tensile strength (σt) are significant parameters in hydraulic fracturing. Owing to the unique mineral composition and sedimentary environment of shale, the mechanical properties of shale exhibit anisotropy. In this study, the notched semi-circular bend (NSCB) and Brazilian disc (BD) tests were combined with acoustic emission (AE) and digital image correlation (DIC) technology to investigate the anisotropic fracture and tensile behaviors of layered shale. The critical plane approach (CPA) criterion is extended and validated, and the universality of the extended CPA criterion is confirmed for both KIC and σt prediction. In addition, the variation of KIC and σt versus loading angle, the relationship between KIC and σt, the typical failure modes of both NSCB and BD specimens, and the fracture initiation angle of layered shales are discussed comprehensively. The following conclusions were drawn: (1) KIC and σt increased with increasing in the loading angle (β), which indicated significant anisotropy of layered shale, and the AE responses for different loading angles also differed significantly. (2) The variation of anisotropic KIC and σt of different shales could be predicted by adjusting the spatial distribution parameter (Ω0), so that the extended CPA criterion could predict KIC and σt of different shales accurately, which confirmed the universality of the extended CPA criterion for both KIC and σt prediction. (3) There exists an approximately linear or power relationship between KIC and σt, and the power relationship can match both experimental and theoretical results much better. (4) The data from DIC and failure modes confirmed that when β was low, the failure modes were primarily affected by the bedding plane. In contrast, when β was great, the failure modes were primarily affected by the matrix. The NSCB specimens exhibited tensile failure, whereas the BD specimens exhibited more complex failure modes, which were a combination of tensile and shear failure. The results of this study can be used for guiding the design and construction of hydraulic fracturing and rock engineering.

Flexural behavior and design methodology for bamboo scrimber-aluminum plate composite beams

This paper presents a study on the flexural behavior of twelve bamboo scrimber-aluminum plate composite beam specimens. The research investigates the effects of aluminum plate thickness and shape on specimen failure mode, flexural moment–curvature relations, and flexural capacity. Finite element (FE) analysis is used to benchmark test results. The study also includes parametric studies that explore the impact of various factors such as aluminum yield strength, plate thickness, adhesive shear strength, shear span ratio, and depth to width ratio on the flexural capacity of the specimens. The results indicate that while increasing the yield strength of aluminum plate has little effect on flexural stiffness and capacity, increasing plate thickness significantly improves these characteristics in the service limit state. Additionally, increasing the depth-width ratio and shear span ratio correspondingly improves flexural stiffness and capacity. The shear strength of adhesive has a significant impact on flexural capacity, but only a minor effect on flexural stiffness during the elastic stage. Based on the parametric study, modified calculation formulae are proposed to predict the flexural capacity of composite beams with and without inter-layer slip.