Search

This paper discusses and reports based on the experimental investigation of the flexural ductility of singly reinforced normal strength and high strength concrete beams. Compressive concrete strength of 40 and 95 MPa were employed to create singly reinforced normal strength and high strength concrete beams, respectively. Fourteen samples made of normal and high strength concrete were engaged to observe the flexural ductility behaviour of beams on the basis of four point bend testing. Analysis on the basis of the flexural cracking, ultimate failure and curvature ductility were carried out to derive the comparison of singly reinforced normal strength and high strength beams. The beams using high strength concrete revealed a higher ductility ratio than that of normal strength concrete, i.e. 4.50 for high strength concrete and 2.60 for normal strength concrete.

Avalanche capability is one of the most significant ruggedness concerns. In this paper, avalanche capability of 1200V 80mΩ CREE SiC MOSFET characterizing planar gate structure is assessed under unclamped inductive switching test with various loads (3.6mH, 1.1mH, 0.3mH). Through similar maximum withstanding avalanche energy for the three loads and failure behavior, the heat induced failure can be determined, even though very different maximum avalanche peak currents Iav,pk and avalanche time tav. The increasing avalanche energy generates heat to rise device temperature until the maximum temperature approaches the metal system on the surface of SiC material. The maximum safe operation temperature for planar SiC MOSFET is determined by the metal melting point. The avalanche ruggedness of the SiC MOSFET provides related information to application design. The results can also help understand ultimate failure cause of avalanche shock and improve the ruggedness of device.

Shear links play an important role as vital members of eccentrically braced frames in achieving required inelastic rotation under severe earthquakes. According to the controversial behavior of these members under Christchurch earthquakes and experimental tests, the ultimate failure mode of the links revealed as web fracture which was different from dominant web buckling mode observed previously. First, the finite element model was verified by results of nine experimental studies conducted by other researchers. Then, to reassess shear link design criteria, 135 finite element specimens were evaluated. The experimental results were utilized for calibration of ductile fracture criteria under low and high triaxiality ratio to resolve finite element incapability of fracture prediction. The experimental links data base (43 links), which mostly meet design criteria, and parametric finite element models were used to reassess the accuracy of the shear links design criteria suggested by AISC. However, most of the shear links over-strength demonstrates a slight moment-shear interaction, but this is not a rational reason to neglect its effect on web fracture strain (domain). The main results show that while design criteria are conservative for most low and intermediate-depth links, they might not be as accurate as in the case of high-depth ones. Finally, the cumulative plastic strain distributions of the parametric studies were utilized to develop the schematic patterns when different boundary conditions exist.

This paper presents a finite element analysis based study of web crippling failures in cold-formed steel unlipped channel sections with their flanges fastened to supports under one-flange load cases (EOF and IOF). Currently no design equations are available in the current cold-formed steel specifications to determine the web crippling capacities of unlipped channel sections with restrained flanges under one flange load cases. Hence the web crippling behaviour of unlipped channel sections was first investigated experimentally using 28 tests and suitable coefficients were proposed for the current web crippling design equation. However, the applicability of the proposed coefficients was limited to the tested channel sections. In this study advanced finite element models were developed in ABAQUS/CAE and validated in terms of ultimate failure loads, load versus deflection curves and failure modes. The developed models were analysed using nonlinear static and quasi-static analysis based on implicit and explicit integration schemes. This study addressed the effects of mesh size, element type, mechanical property model and inertia of support and loading plates. Also, the effects of two enhancement techniques of explicit analysis such as mass scaling and artificial loading rates with different thicknesses were investigated and the results are presented. A detailed parametric study was then conducted using the validated finite element models. New and improved design equations were proposed to determine the web crippling capacities of unipped channel sections using the results from both finite element analysis based parametric study and experiments.

Deformation and fracture of brittle materials, especially crack propagation, have drawn wide attention in recent years. But dynamic crack propagation under impact loading was not well understood. In this paper, we experimentally tested Brazilian disk (BD) fine sandstone specimens containing pre-cracks under cyclic impact loading by theΦ74 mm diameter split Hopkinson pressure bar (SHPB) test device. The pre-cracked specimens were named central straight through crack flattened Brazilian disk (CSCFBD). By using the low air-pressure loading conditions (0.1 MPa, equal to the impact velocity of 3.76 m/s), a series of dynamic impact tests were detected successfully, and the effects of pre-cracks on dynamic properties were analyzed. Experimental results show that the multiple cracks mostly initiate at/or near the pre-crack tips and then propagate in different paths and directions varying by inclination angles, leading to the ultimate failure. Compared to static or quasi-static loading, dynamic crack propagation and fracture behavior are obviously different. Furthermore, we characterized the crack propagation paths, directions, and fracture patterns and discussed the influences of the pre-cracks during the breakage process. We concluded that the results obtained are significant in investigating the failure mechanism and mechanical properties of brittle materials under impact loading.

This paper discusses the physical parameters, damage performance, and compressive properties of nylon fiber-reinforced concrete (NFRC) and recycled nylon fiber fabric-reinforced concrete (NFFRC) for 30 MPa design strength in 14 days. The slump, failure mode, compressive behavior, and energy absorption capability of NFRC and NFFRC were measured, and the results were compared with those of plain concrete (PC). The slump of NFFRC was 9.30% lower than that of PC and 1.54% higher than that of NFRC. The densities of NFFRC and NFRC were almost identical but 0.61% lower than that of PC. The compressive strength and energy absorption capability of NFFRC were 5.37% and 10.74%, and 12.39% and 19.05% higher than those of PC and NFRC, respectively. After ultimate failure, the inner and external structures of the NFFRC specimens consistently broke down, but they maintained their integrity. NFFRC presents many advantages over PC and NFRC. Overall, waste NFF may replace NF in some engineering applications.

Coalescence among fractures would have influence on the stability of rock masses. Deep understanding of mechanical behavior of fractured rock masses is an important mean to identify failure mechanism of geological disaster. In this study, crack propagation processing was studied through loading pre-fractured specimens of concrete block, termed as rock-like material, in uniaxial compression tests. New non-parallel double-crack geometry was introduced to observe crack coalescence. The flaw combinations are different from the normally used flaw configurations. In addition, ultrasonic detection tests were performed on the test blocks. The stress and strain data of these tests and characteristic parameters of sound wave were recorded. The stress-strain curves of each test block under the uniaxial compression test were drawn, relations among deformation characteristics and crack angle of the crack specimens, and their overall strength were analyzed. It is found that strength of the specimen decreases as crack inclination increases under two crack inclinations. The highest uniaxial compressive strength is found in the specimen with the cracks at the same angle in different directions. Based on description of the crack initiation location, crack surface and the ultimate failure patterns, failure modes of eight subtype for test blocks are divided into three categories. It is expected that the study results could be beneficial for engineering application of jointed rock masses.

Background Patellar tendon rupture is a potentially devastating injury. Surgical repair is the primary treatment recommended for the patients with patellar tendon ruptures. Given the tendon properties, the suture technique is critical for proper tissue repair. Providing adequate loading during early mobilization is essential to prevent tendon suture repair failure. Therefore, the current study evaluated the mechanical characteristics of various applied loadings on patellar tendon repair using Krackow suture via a porcine model. Methods Twelve fresh porcine hindlimbs with patellar tendon rupture were repaired by Krackow method using synthetic and non-absorbable No. 5 Ethibond sutures. Loadings of 100 and 200 N were applied during the cyclic loading test. A three-dimensional optical motion capture system was used to record the gap formation at the initial, 50th, 100th, 150th, 200th, 250th, 500th, 750th, and 1000th cycle. After cyclic loading, the specimen was loaded to failure under displacement control at a rate of 1 mm/s. Results Suture breakage was the primary failure mode in both loading conditions. After 1000 cyclic loadings of 100 N, the ultimate failure strength was 243.6 ± 25.8 N. However, the specimens tested under 200 N of loading failed before reaching 200 cycles. Under the 100 N loading, the largest gap deformation (1.89 ± 0.23 mm) and residual deformation (0.213 ± 0.183 mm) were found in the initial cycle. The average cumulative displacement was 5.13 mm from the initial cycle to the 100th cycle and 4.5 mm from the 250th to the 1000th cycle. Conclusions Our findings can serve as reference values for further comparisons with various repair techniques or materials. This study suggests that the initially applied load after patellar tendon repair is an important risk factor of re-rupture.

The mechanical response of rock joints with multiscale triangular-shaped asperities, including primary and subordinate asperities, when subjected to prepeak cyclic shear loads and static constant normal loads (CNL), is investigated in the laboratory. Three direct shear tests on jointed rock specimens with different initial primary asperity angles, i.e., 15°, 30° and 45°, and the same initial subordinate asperity angle of 45° were first conducted. Three different types of shear failure modes, i.e., climbing failure, mixed climbing-gnawing failure and gnawing failure, were observed. Subsequently, cyclic shear tests on jointed rock specimens were conducted using two consecutive horizontal loading steps: load-controlled and displacement-controlled horizontal shear loading. The cyclic load-controlled horizontal shear loads with amplitudes of 50% and 80% of the maximum direct shear strength were applied to jointed rock specimens for different numbers of cycles. To reach the ultimate failure of the jointed rock specimens, the shear displacement was increased at a constant rate of 0.5 mm/min. In addition, the effects of initial asperity angle, shear cyclic number, shear cyclic amplitude and shear cyclic loading rates on the mechanical response are studied and discussed. It can be found from the experimental results that abrasion failure occurs at the subordinate asperities within a low number of cycles, while fatigue cracks initiate and propagate within a high number of cycles.

The failure mechanism and limit support pressure are essential factors for the stability assessment of tunnel face during shield tunneling. Previous studies were mostly based on the assumption that soil fails when the plastic limit is reached. The static liquefaction of saturated sand at pre-failure state often largely reduces shear strength; a stable tunnel face could be destabilized and even collapses abruptly. This paper aims to explore the static liquefaction failure of tunnel face in saturated sands by 3D discrete element simulation. The particle shape is considered by using clump composed of two identical spheres, and the micro-material parameters are calibrated by fitting against triaxial tests. The tunnel face is initially supported by the earth pressure at rest, and then the pressure is reduced by applying a displacement on the free surface until soil body completely collapses. The second-order work during the unloading process is calculated, and a negative value denotes the initiation of static liquefaction. The distribution of negative second-order work point shows the initiation and propagation of static liquefaction. The ultimate failure mode is shown to be composed of a sliding wedge and an overlying chimney, and the chimney is confined to a local area for soil arching. The experienced stress path of tunnel face verifies the existence of static liquefaction instability, indicating the stability analysis should consider static liquefaction rather than simply using the conventional plastic limit state analysis.

Crystal plasticity finite element analyses are carried out in three dimensions to investigate void evolution in hexagonal close packed single crystals. Two crystallographic orientations are considered favoring either slip or twinning, which are both accounted for in the formulation. The effect of stress state is analyzed by varying some nominal measure of overall triaxiality. The orientation and stress state dependence of the effective response, including void evolution, are characterized in some detail, as driven by the micromechanics of plastic deformation. Particular emphasis is laid on crystallographic aspects, such as the emergence of deformation sectors, the influence of the polar character of twinning, and directional void growth. In addition, all analyses were conducted up to strain localization so as to uncover orientation and crystallographic aspects of void coalescence. The potential implications of slip and twinning mechanisms on ultimate failure in hexagonal close packed materials are discussed.

This paper presents an investigation into the performance of pultruded glass fibre reinforced polymer (GFRP) square hollow columns subjected to both compression and bending. Eccentric compression experiments were performed on slender GFRP column specimens at different eccentricities. Bolted sleeve joint was employed to connect the GFRP column specimens and loading end plates. The relationship between the load-bearing capacities of GFRP columns and the eccentricities was received and discussed. The interaction curve between compression load and bending moment due to eccentricity (P-M curve) was obtained from experiments and compared with finite element (FE) and design approaches. Results revealed that the compression performance of GFRP columns was significantly affected by the eccentricity and the moment capacity of bolted sleeve joint. Splitting failure developed from the initiative longitudinal cracks in the bolted sleeve joint region at the end of the columns was found as the ultimate failure, after the large lateral deformation. FE analysis presented satisfactory agreements with experimental results; furthermore, the stress analysis in the critical bolted sleeve joint region indicated that the in-plane shear stress was the dominant component leading to the splitting failure.

This paper presents a numerical model describing a corrosion-defect-containing pipeline subjected to internal pressure, including the FRP layer, the filler layer and the adhesive layer and considering the ultimate failure state of the pipe steel, epoxy resin and FRP. The main goal was to accurately estimate the ultimate failure pressure of corroded pipelines reinforced with composite repair systems, focusing on the influence of the thickness of the FRP layer and the properties of the epoxy resin on the performance of the composite repair systems. A nonlinear numerical analysis of different repair conditions is carried out. According to the results from the numerical analysis, for the same defect condition and different repair conditions, composite repair systems can effectively inhibit the radial expansion of the defect region after the steel material yield, and different repair conditions cause different failure modes that lead to different ultimate failures from internal pressure.

This paper discusses the computational design and digital fabrication process for a novel deployable timber structural system. Termed a 'mass timber stressed arch', the proposed system transforms a modularised geometry from a flat state to an interlocked curved structure, with rotational assembly occurring from a post-tensioning actuation mechanism. Two techniques are developed for design of the structure: a subdivision scheme for lowwaste manufacturing of component arch modules and a hybrid integral joint system for resolution of the required kinematic freedoms and fixities between adjacent modules. The deployment mechanism and digital design-tofabrication process are validated through construction and repeated installation of a full-scale timber arch pavilion. Full-scale experimental testing of the system showed the system to possess a high load carrying capacity, with ultimate failure occurring by shearing of the pin connection between adjacent modules.

Summary Background There are numerous techniques for MPFL reconstruction, however, one single technique has not been proven to be superior to another. Suture anchor reconstruction has been shown to provide stable fixation while decreasing the risk of patellar fracture. Purpose The aim of the study was to compare the stiffness and clinical load to failure of two common MPFL reconstruction techniques. Our hypothesis was that there would be no significant difference in the stiffness and the clinical load to failure between the suture anchor and interference screw reconstructions. Methods Eight pairs of fresh frozen cadaveric knees were randomized into two groups undergoing MPFL reconstruction using either a suture anchor technique (n = 8) or an interference screw technique (n = 8). Testing was performed at 0, 30, 60, and 90 degrees of flexion for the native knee, transected medial structures, and reconstructed MPFL. Next, the reconstructed MPFL specimens were tested until failure in 0 degrees of flexion. t-Test, One-Way ANOVA, and repeated measures of ANOVA were used for statistical analysis, p values less than 0.05 were considered significant. Results The average stiffness for the suture anchor and interference screw reconstructions was 12.02 ± 3.96 N/mm and 14.21 ± 4.20 N/mm, respectively (t-test, p = 0.27), while average clinical load to failure was 256.57 ± 54.1 N and 237.81 ± 23.82 N, respectively (t-test, p = 0.38). There was no significant difference in stiffness between the suture anchor and interference screw techniques at 0, 30, and 60 degrees of flexion. Conclusions The suture anchor and interference screw reconstruction techniques produce comparable stiffness for sub-failure testing at 0 and 30 degrees of flexion. For testing to failure, the initial stiffness for both reconstruction techniques have been shown to be concordant with previously published values for the native MPFL. Both reconstruction techniques provide greater ultimate failure loads than those reported for the native MPFL in previous studies. Suture anchor reconstruction described in our study provides another reliable option for the reconstruction of the medial patellofemoral ligament. Clinical relevance Our study provides biomechanical data that the suture anchor technique described in this study provides comparable fixation compared to interference screw fixation and has the potential of reducing fracture to patella particularly in the pediatric population with small patellae.

The deterioration and premature failure of an orthotropic steel deck pavement during its service period is a pressing issue. Strain hardening cementitious composites (SHCC) possess an extreme tensile ductility, in the range of 3%–5% (about 300–500 times that of concrete). Using SHCC as a steel deck pavement can enhance the overall stiffness of a deck system. In this paper, an SHCC-grooved steel composite structure is the research object, and the tooth spacing, tooth width, and tooth height are the parameters. The shear behavior of an SHCC-grooved steel composite structure was studied using a compression shear test and the digital image correlation method. The response surface method was used to analyze the significant influence of the test parameters on the shear capacity, and the response model of the shear capacity was established. The calculation formula of the shear capacity of an SHCC-grooved steel composite structure was established based on the theory of the diagonal compression strut. The experimental results show that the cracking of a shear diagonal SHCC leads to the ultimate failure of an SHCC-grooved steel composite structure. The angle between the main crack and the shear load direction ranges from 30 to 45°. The failure process of the composite structure can be divided into 4 stages: linear elasticity, elastic-plastic, slip hardening, and instability failure. The order of the influence of the test parameters on the shear capacity is the tooth spacing > tooth height > tooth width. The response surface model can optimize and predict the shear capacity of the composite structure under different parameters within a certain range. The calculated values of the shear capacity model based on the theory of the diagonal compression strut agree well with the experimental values, and the calculated values are favorable for safety. This research can provide a reference for the shear design of an SHCC-grooved steel composite structure.

This paper presents the results of an experimental study on the seismic behavior of high-strength circular concrete-filled thin-walled steel tubular (HCFTST) columns with ultra-large diameter-to-thickness (D/t) ratios exceeding the limitations of the current construction standards. Sixteen HCFTST columns with different combinations of D/t ratio, concrete cylinder compressive strength ( f c ), and axial compression ratio (n) were tested under constant axial compression combined with cyclic lateral loading. The ultimate failure state was achieved when the steel tubes ruptured severely and core concrete crushing occurred. The results from hysteretic curves indicated that the HCFTST columns with ultra-large D/t ratios displayed flexural failure and shear failure modes. Subsequently, the skeleton curve, ductility, energy dissipation capacity, and stiffness degradation were discussed in detail. Moreover, the effects of D/t ratio, concrete cylinder compressive strength and axial compression ratio on performance were investigated so that this work could serve as a basic reference to future studies, and a strength model was proposed to predict the moment-resisting capacity. The experimental investigation indicated that (i) using high-strength Q690 steel could significantly contribute to a larger elastoplastic deformation capacity and delay the onset of post-peak behavior, even though a lower ductility capacity was provided; (ii) the proposed strength model could satisfactorily predict the moment-resisting capacity; (iii) the out-of-code HCFTST columns with reasonable design could demonstrate favorable seismic behavior and could be accepted as aseismatic components in earthquake-prone regions.

Hydrogen (H) embrittlement of metals is a common phenomenon but the exact atomic mechanisms responsible for H-induced plasticity process and ultimate failure are not clarified. In this work, the impacts of H on tensile deformation behaviour of different types of twist grain boundaries (TGBs) have been systematically studied by molecular dynamics (MD) simulations. Different deformation mechanisms are reported, depending on grain boundary types and bulk H concentrations, including easier dislocation nucleation due to the presence of H, H-enhanced dislocation dissociation, and H-induced slip planarity. The simulations indicate that the interactions between H-enhanced dislocation plasticity and TGBs play a crucial role in the ultimate fracture path. The decohesion of the TGBs is considerably promoted by the presence of H under conditions where dislocation accommodation and emission process on the TGBs causes the changes of grain boundary structures and local stress state. Our results advance a mechanistic understanding for experimentally-observed H embrittlement and provide a viable path to engineering microstructure with high resistance to H embrittlement in new materials.

Geomechanical model test is an important way to analyze the safety of high arch dams. The traditional monitored displacements and stresses are difficult to interpret the internal failure process of dams and foundations. Acoustic emission(AE) technique was used in the geomechanical model test of arch dam to analyze its internal failure. AE 2D planar locating technology for arch dams and signal parameter analysis method were studied and applied to an arch dam geomechanical model test. The failure process of the dam body and foundation was revealed. The left dam heel of the arch dam model cracked first, continuing to expand to higher elevation along the left abutment with the increase of overload times, and the horizontal crack penetration leaded to the ultimate failure of the dam body. Safety factors for initial crack, nonlinear deformation and ultimate bearing capacity of the arch dam model had been clearly obtained based on AE technique. The results of AE analysis coincided well with the actual failure condition. So it is confirmed that AE technique is effective for geomechanical model test, and it has a bright prospect to be used in situ test of arch dam.

Purpose Roller compacted concrete (RCC) pavement is used in areas subjected to heavy impact loads; therefore, higher impact resistance is a desirable property of consideration. This study aims to investigate the effect of partial replacement of fine aggregate with crumb rubber (CR) and the addition of nanosilica (NS) by weight of cementitious materials on the impact resistance of roller compacted rubbercrete (RCR). Design/methodology/approach Four replacement levels of CR (0, 10, 20 and 30 per cent) and four addition levels of NS (0, 1, 2 and 3 per cent) were considered. The impact resistance test was carried out using the drop weight test recommended by ACI 544. Findings The results showed that the impact resistance of RCR increases with an increase in both CR and NS addition, though for CR above 20 per cent, sudden drop in impact resistance was observed. However, NS reduces the ductility of RCR by decreasing the post-cracking impact resistance. Response surface methodology was used to develop models for predicting the impact resistance of RCR, and the developed models showed a high degree of correlation. As a result of wide variations in the impact drop test data, two-parameter Weibull distribution function was used for the data analysis, and it was found that the probabilistic distributions of the first crack and ultimate failure impact resistance follow the two-parameter Weibull distribution function. Originality/value In this work, the effect of partial replacement of fine aggregate with CR and the addition of NS by weight of cementitious materials on the impact resistance of RCC pavement has been investigated. CR has been used to increase the impact resistance of RCC Pavement.

The shear-deficient structural elements affect the designed serviceability of structures. The early decay in serviceability reduces the functionality of the structures and leads to global failure of the structure. The retrofitting offers a greater flexibility to restore the serviceability by restrengthening the distressed structural elements. The concrete, ferrocement and fiber-reinforced polymers (FRPs) jacketing are some of the retrofitting techniques tried in the past. But all these techniques have their associated advantages and disadvantages; for example, one of the disadvantages of FRP jacketing is a brittle failure due to debonding of FRP. These failures restrained the serviceability of retrofitted structure elements. In the current study, the newly developed material, i.e., ultra-high-performance fiber-reinforced concrete (UHP-FRC), is being used to retrofit the shear-deficient reinforced concrete beam. The high compressive strength (above 110 MPa), high tensile strength due to the addition of fibers, high flexural strength, very low permeability and high workability of UHP-FRC are expected to improve the performance of retrofitted RC members. Hence, the performance of UHP-FRC as a retrofit material for beams deficient in shear is explored in the present experimental study. The beams designed deficient in shear are initially stressed to 60% of the ultimate failure load and then retrofitted by UHP-FRC. The U-type retrofitting and external side face jacketing are used to retrofit the initially stressed beams. The results show that the behavior of retrofitted RC beams improved in terms of ultimate load carrying capacity, ductility and energy absorption. Further, it is observed that the U-type retrofitting is better than side face jacketing retrofitting.

Cold formed steel sections are normally produced by cold work manufacturing processes. The amount of cold work to form the sections may induce residual stresses in the section, especially in the area of bending. Studies by previous researchers of the effects of local buckling on the failure mechanics of thin-walled compression members have shown that ultimate failure will occur when the yielding has reached most of the middle surface in the corner region of the sections. Hence, these cold work processes may have significant effects on the section behaviour and load-bearing capacity. Most of the studies have investigated the effect of residual stresses raised from roll-forming operation and its influence on steel section behaviour. However, press-braking has not received much attention. Therefore, a 3D finite element simulation has been employed to simulate this forming process. This study investigated the magnitude and distribution of residual stresses along the length of the corner region and through thickness residual stress variations induced by the press-braking forming process. The study concluded that residual stresses are not linear longitudinally (along the corner region). Maximum residual stresses exist near the middle surface of the plate. The neutral surface contains a combination of compressive and tensile residual stresses. The neutral axis is shifted from mid-surface by 7.5% of the plate thickness due to bending. The comparison of the 3D-FE results with the existence of 2D-FE results illustrates that the 3D-FE results show a variation in the transverse and longitudinal residual stresses along the plate length.

Acoustic emission, electrical resistance, and surface optical techniques were used to monitor matrix cracking and fiber-breakage during fatigue in tension for [0/90]2s SiC-based laminate composite single-notch specimens. Acoustic emission sensors were positioned in several locations including on the edge of the specimen which enabled location of events through the width and the location of internal tunnel-type cracks. Surface optical techniques, including digital image correlation, enabled the extent of surface crack growth. From these two sets of data a simple circuit could be constructed of the different damaged and undamaged regions in the region of the notch that was in good agreement with the change in electrical resistance, thus establishing a correlation with change in ER and damage development. The unique placement of AE sensors on the edge of the specimen also enabled the capture and location of what are believed to be fiber failure events prior to ultimate failure.

For offshore bridges, the most prominent problem in the whole life cycle is that it is in an earthquake prone zone and an offshore corrosion environment at the same time. A nonlinear dynamic analysis model is set up for an offshore multispan and continuous rigid frame bridge based on the OpenSEES platform. The fragility surface of the bridge pier, bearing, bridge platform, and system are established by selecting a reasonable damage constitutive model of the material durability and a damage index analysis that studies the damage of the bridge durability to time-varying seismic fragility of bridge components and the system of the whole life cycle in offshore environment. The results show that the durability damage will lead to a constant decline in seismic capacity of the pier and an increase of the seismic demand under earthquake action as well as the probability to reach the ultimate failure state; compared to high piers, a low pier is more vulnerable to the offshore corrosion environment; the seismic fragility of bridge platform is higher than that of simply bearing; and the influence of offshore corrosion on environment is relatively large. With the prolongation of service period, the effect of durability damage on the seismic fragility of bridge system cannot be ignored in the coastal environment and it is necessary to make a reasonable evaluation on the seismic fragility of bridge structure during the whole life period.

Fiber metal laminate (FML) is an advanced composite material, which consists of metal layers and polymer matrix composites. Due to the combination of the advantages of traditional metal and composite materials, FML has been widely used in the aircraft industry. Due to advantages in inspection and reliability, the mechanically fastened (riveted or bolted) joints are essential for a complex structure. The present study investigated the effects of geometry parameters and ply stacking sequences on the mechanical properties of pin-loaded FML joints. A three-dimensional progressive failure model had been created to investigate the failure response of FML joints. A comparison between simulation and experimental results showed a good agreement on the strength and internal damage pattern (fiber damage, matrix damage, and cohesive layer delamination between 0° fiber and outer aluminum) for the pin-loaded FML joints. It was found that ultimate failure strength increased with the increase of width-to-diameter ratio (W/D) or edge distance-to-diameter ratio (E/D). The failure modes of pin-loaded FML joints were dissimilar by varying the ratios of W/D and E/D. The dominant failure mode of studied joints was bearing failure mode. Numerical simulation results showed that ply stacking sequence has obvious effects on the mechanical properties of FML joints.

In this study, tensile deformation behaviour and material properties has been investigated at different temperatures and strain rates. The isothermal uniaxial tensile tests were conducted from room temperature to 700°C at an interval of 100°C at different quasi-static strain rates (0.01, 0.001, 0.0001 s-1). The flow stress is significantly influenced by temperature and strain rate change. Various important material properties namely: yield strength (σy), ultimate tensile strength (σut), % elongation and strain hardening exponent (n) are determined at different temperatures and strain rates. In order to understand the fracture behaviour of a DP steel, microstructural characteristics were studied using Scanning Electron Microscope (SEM). Predominately ductile failure has been reported at higher temperatures. The individual phases (ferrite + martensite) play an important role in defining the ultimate failure mode in tensile testing.

To investigate the strength and fracture mechanism of flawed rock, a series of uniaxial compression tests on sandstone specimens containing elliptical holes and fissures were carried out using acoustic emission (AE) monitoring and digital image correlation (DIC) system. Based on the experimental results, the stress-strain curve, mechanical parameters, AE counts and strain field evolution were analysed, and they indicated that the ligament angle is a significant factor influencing the strength and deformation of pre-flawed sandstone specimens. As the ligament angle increases, the peak strength, peak strain and elastic modulus first decrease and subsequently increase. Observations show that a stress fluctuation corresponds to an inflexion point in the accumulated AE count curve and AE counts reach the maximum value at or after peak strength. Additionally, the highlighted strain localization zones are indications of crack initiation, and crack propagation behaviour is a progressive evolution of the highlighted strain localization zones. Based on an analysis of the ultimate failure patterns, four types of rock bridge coalescence modes are identified, i.e., no coalescence, shear coalescence, double-shear coalescence and double-tensile coalescence.

In this study, two sets of manhole cover slabs were cast; one set with conventional concrete and the other set with coconut shell aggregate concrete. In both the cases, in one set 10 mm steel reinforcements were used and in the other sets 12 mm steel reinforcements were used. These manhole covers were produced and tested as per IS 12592: 2002. In both the concrete, along with conventional materials and coconut shell, steel fibers and micro silica were used to reach the specification required for the manhole cover slab. As per IS 12592:2002, a size of 600 × 600 × 100 mm and light duty grade of manhole cover slab were selected and studied. Test parameters such as workability of mixes, density of mixes, settlement limits at test load, crack formation, ultimate load and settlements at ultimate load results were discussed and presented. It is observed that the settlement at the time of test load on both conventional and coconut shell aggregate concrete manhole cover slabs were well within the limit specified by IS 12592: 2002. In both the cases, there was no formation of cracks at the time of sustaining test load as per IS 12592:2002. Load factors against ultimate failure were more than 4 in all the cases and hence, coconut shell aggregate concrete can be used for the production of manhole cover slabs. Test results and performance of coconut shell aggregate concrete manhole cover slabs encourage the use of coconut shell as an aggregate as the replacement of conventional aggregate in the production of manhole covers.

OBJECTIVE To determine the influence of suture patterns on resistance to gap formation after tendon plating STUDY DESIGN: Ex vivo study SAMPLE POPULATION: Suspensory ligament and superficial and deep digital flexor tendons harvested from 16 neonatal cadaver foal limbs. METHODS Each tendon/ligament from a given limb was randomly assigned to one of three treatment groups consisting of a 7-hole veterinary cuttable plate fixed with alternating simple interrupted, figure-8, or hybrid suture patterns. The constructs were distracted at a rate of 1.0 mm/s to failure, as determined by the formation of a 1 mm gap for initial failure and a 3 mm gap for ultimate failure. The mode of failure was also recorded. RESULTS Constructs prepared with hybrid and figure-8 patterns sustained over 2× higher (p

A common method of failure in electronic packages is the failure of solder joints. Solder joints subjected to thermal cyclic loading usually fail due to fatigue failure. This is brought about by the shear forces introduced by the different Thermal Expansion Coefficients (CTE) of the package components. Previous researches have shown that recrystallization assisted cracking plays a significant role in the fatigue failure of these solder joints. In this paper, the authors seek to observe the changes in the microstructure of SAC305 solder joints subjected to mechanical cyclic loading under various conditions. The test specimens were 3x3 BGA array of SAC305 joints sandwiched in between two FR-4 PCBs (Printed Circuit Boards). The specimens were held in epoxy preforms and polished to expose the solder joints. The samples were then extracted and some of these were aged at 125 °C for 10 days. Both the aged and non-aged specimens were then isothermally mechanically cycled at either room temperature or at 100 °C. The authors then proceed to observe the differences in the microstructure due to mechanical cycling of the joint under different conditions, namely, aging, or high temperature mechanical cycling, or a combination of both. The micrographs before and after the cycling were captured by an optical microscope. The other objective of this study was to also observe if recrystallization played a part in the ultimate failure of the joints when subjected to shear mechanical cycling for each of the conditions.

Purpose To investigate the metal screw-in anchor failure mode and load to failure for 2 different eyelet alignments after anchor insertion in ovine humeri. Methods Sixteen ovine humeri were dissected, and a 5-mm metal anchor with 2 nonabsorbable polyblend polyethylene sutures was inserted into them in the proximal position of the greater tuberosity. The alignment of the anchors after insertion was adjusted to make 2 test groups, each with 8 specimens: In group 1, the anchor eyelets were malpositioned, whereas in group 2, the anchor eyelets were aligned according to the manufacturer's instructions. After insertion, cyclic tests from 10 N to 180 N were performed with a frequency of 1 Hz for 200 cycles; specimens were then loaded to failure to evaluate the maximum load of the system and observe the associated failure mode. Results The mean ultimate failure load in group 2 was not significantly different from that in group 1 (P = .472). Conclusions For metallic screw-in suture anchors, the alignment of the eyelet does not change the failure mode and the load to failure after cyclic loading of the bone-anchor-suture system in ovine humeri. Clinical Relevance Our results indicate that on the basis of this anchor model, the position of the eyelet in the greater tuberosity does not interfere directly with the biomechanical performance of the system.

Material properties at the vicinity of the cut-outs in composites are not entirely defect-free. The nteraction of multiple cutouts like rivet holes, the repercussion of their configuration on crack propagation, and ultimate strength were predicted using Peridynamic method and the results are reported in this article. The effect of microscale defects at the vicinity of the cutouts on macroscale damage propagation were shown to have quantifiable manifestation. This study focused on two to four holes in unidirectional composite plates with 0°, 45°, and 90° fiber directions, while the vicinity of a hole was considered degraded. Numerical results were validated using quantitative ultrasonic image correlation (QUIC) and the tensile test. Both the experimental and numerical results confirmed that the strength of the horizontal configuration is higher than the vertical in the plates with two holes. Furthermore, the square configuration was found to be stronger than the diamond configuration with four holes. When the effect of microscale defects was considered, the prediction of ultimate strength was better compared to the experimental results. The predictive model could be reliably used for progressive damage analysis.

BACKGROUND Numerous transosseous fixation techniques for flexor tendon injuries in Zone 1 of the hand have been described in the literature. While relatively high maximal loads to failure are documented in different biomechanical experiments, several tests revealed a low 2 mm gapping resistance of the tendon-to-bone repairs. We therefore aimed to investigate the effect on gap formation adding a peripheral suture to an established transosseous fixation technique. In addition, we analyzed the influence of different suture materials (braided vs. non-braided) on the stability of the core suture. METHOD A total of 30 porcine flexor digitorum profundus tendons were divided into 3 groups (n = 10 each) and repaired using the transverse intraosseous loop technique (TILT). In group 1 and group 2 the repairs were performed using PDS 3-0 or Ethibond 3-0, respectively. In group 3, a peripheral suture was added to the core suture (PDS 3-0) consisting of two figure-of-eight stitches with PDS 5-0. The biomechanical performance of the repaired tendons was analyzed using a standardized protocol. RESULTS The suture material and peripheral suture showed no effect on the ultimate failure load in our testing. However, the addition of a peripheral suture led to a statistically significantly higher 2 mm gap force when compared with the repair with a core suture only. CONCLUSION In conclusion, addition of a palmar epitendinous suture to the transosseous core suture significantly increases the load to 2 mm gap formation in Zone 1 flexor tendon repairs and thus allows an immediate controlled mobilization.

The fissure flawed red-sandstone under dynamic rainfall infiltration is one of the key factors determining the safety and reliability of red-sandstone embankment and slope. However, there is still a lack of investigations considering the combined influence of rainfall infiltration and flaw geometry on the mechanical behavior of fissure flawed red-sandstone. Therefore, the effects of rainfall intensity, rainfall duration, as well as prefabricated fissure inclination angle on the uniaxial compressive mechanical behavior of red-sandstone containing a prefabricated fissure were investigated by rainfall infiltration and uniaxial compression tests. The results show that fissure inclination angle, rainfall intensity, and duration have significant influences on the axial stress-strain characteristics of the red-sandstone specimen under uniaxial compression. The quantitative expression of the unconfined compressive strength, peak strain, modulus with fissure inclination angle, rainfall intensity, and duration are obtained. The unconfined compressive strength, deformation modulus, and elastic modulus of the red-sandstone specimen present negative relationships with rainfall intensity and duration, while a positive trend is observed for its peak strain. The unconfined compressive strength, deformation modulus, and elastic modulus of the red-sandstone specimen attain the minimums when the prefabricated fissure inclination angle is 45°, while its peak strain reaches the maximum at this time. The ultimate failure modes, crack characteristics, and types of the red-sandstone specimen under uniaxial compression after rainfall infiltration are discussed according to the photographic monitoring in uniaxial compression tests. The meso-level failure mechanism of the red-sandstone specimen under uniaxial compression after rainfall infiltration is evaluated on the basis of the meso-morphology of the specimen’s fractured surface. The influences of prefabricated fissure inclination, rainfall intensity, and duration on the variations of the red-sandstone specimen’s crack growth angle under axial compression are also analyzed.

This study investigates the bond strength behaviour of plain surface wave type configuration (PSWC) rebars in comparison to mild steel (MS) and high yield strength deformed (HYSD) rebars of varied rib configuration as per BIS and ASTM standards. The variables in the rebar include plain surface, curved surface, parallel rib, diamond rib and Nano modified cement polymer anticorrosive coating (CPAC). Total of 30 pull-out specimens and 12 beam-end specimens were put to a pull-out test following BIS and ASTM standard respectively. The load corresponding to 0.025mm free end (FE) slip and 0.25mm loaded end (LE) slip were carefully observed. The load-deflection behaviour, appearance of the first crack in the specimens and ultimate failure load was recorded. The experimental results showed that as compared to MS rebars, HYSD rebars offer an approximately threefold increase in ultimate bond strength and 1.5 times increase in usable bond strength irrespective of varied rib configuration. PSWC rebars with 4mm offset and 80mm pitch offered 2.4 times increase in ultimate strength and 76.2% increase in usable bond strength as compared to MS rebars. The ultimate pull-out load of PSWC rebars was around 25% and the usable bond strength was only 8.6% lesser than HYSD rebars with parallel ribs. The adopted coating enhanced the corrosion resistance and the reduction in bond strength with any surface configuration was less than the permissible maximum reduction of 20% as specified in IS 13620-1993. Hence it can be concluded that PSWC rebars offered promising bond strength results and upon further optimization and study in other aspects, PSWC rebars can be a way to replace HYSD rebars in future for enhancing concrete durability at zero added cost.

Pile foundations are used for jacket-type offshore structures, which are subjected to large magnitudes of lateral loads due to waves and winds. The ultimate failure of a pile-soil system is catastrophic and excessive lateral deflection of the pile creates operational difficulties. In view of this, the bending moment in the pile is required to be predicted in a rational manner. The p-y concept developed by Reese and Matlock (1956) is popularly being used to estimate pile top deflection and bending moments.

Application of rubberised concrete in earthquake prone areas is of paramount significance. Although investigations have been conducted to research on the ductility of rubberised concrete, the behaviour of rubberised concrete with Burnt Clay Brick Powder (BCBP) is not well understood. This study was focused at capturing the ductility behaviour of rubberised concrete containing BCBP. In this study, 3 beams were investigated in flexure while the other 3 beams were made to fail in shear and flexure. For the beams that failed in flexure, ductility of concrete beams containing 5% BCBP and 10% Waste Tire Rubber (WTR) improved by 23.47% compared to control beam. This increase in ductility was evidenced with only 15.31% reduction in flexural load. Moreover, the beam containing 5% BCBP and 10% WTR failing in shear and flexure exhibited 14.60% ductility improvement with 16.33% load reduction in comparison to the control beam. Eventually, the study concluded that it is possible to achieve improved ductility without substantial loss in ultimate failure load by using 5% BCBP and 10% WTR. Such properties established this rubberised concrete with 5% BCBP as potential candidate in seismic applications.

The present paper proposes some enhanced models, with different levels of accuracy, for the design of monolithic CLT shear wall based on the definition of reliable N-V interaction domain. The basic assumptions and the novelty aspects of the proposed models are presented. In particular, the adoption of an elastic-perfectly-plastic constitutive law for the timber instead of an elasto-brittle one and the accounting for the coupled axial-shear behavior of the connection elements to derive N-V interaction domains are critically discussed. Moreover, two different methods are adopted for the linearization procedure of the connection load-displacement response. Four of the proposed models are design oriented, two representing a lower bound (more suitable for practitioners), and two representing an upper bound. One more model is developed, which is research oriented and based on hybrid force-displacement approach. The reliability of the different models is investigated by means of numerical analyses exploiting the ultimate failure condition of the materials both in terms of strength and displacement capacity. Finally, the N-V domains for some CLT shear walls are presented and the impact of the different basic assumptions on the results are discussed in comparison with both experimental and numerical literature results.

Rock bolting is a ground reinforcement technique broadly used not only in mining but also in civil engineering applications. A rock bolt consists of a bar inserted in a borehole that is drilled into the surrounding soil or rock mass and secured to it generally with a binder, which can be cementitious or resin based. Cementitious grouts require several hours to harden and resin cartridges might lead to shortcoming such as poor mixing, collapsed boreholes prior to insertion, and insufficient resin volume for full encapsulation due to enlarged boreholes. A novel pumpable thixotropic resin based on polyurea silicate has been developed in order to overcome the issues of conventional resin cartridges, to ensure a quick curing time within seconds and to be able to install bolts on the roof. Several mechanical pull-out tests on hollow and solid rock bolts according to DIN 21521 have been performed in order to assess the ultimate failure for the novel pumpable thixotropic resin. Results are very useful to contractors and designers to understand the mechanical response of a novel thixotropic resin.

Concrete is a brittle material that is weak in tension and is prone to internal microcracking. With the constant demand for improvement in concrete’s durability and mechanical proprieties, the use of fiber reinforcements has shown promising results. The findings of this paper are based on test results on hybrid fiber reinforced concrete (HFRC) samples of simply supported two-way slabs, produced with a selected volumetric proportion of steel fiber (SF) and polypropylene fibers (PPF). A total of twenty-one specimens were fabricated. Concrete slab specimens were tested under flexural loading and their response in terms of strain, deflection, first crack, and ultimate failure loading was determined. The dosage of SF in concrete ranged from 0.7 to 1.0%, whereas 0.1–0.9% PPF was used by volume of concrete. It was found that a combination of 0.9% SF and 0.1% PPF gave favorable results for loading capacity, ductility, and cracks. A Finite Element Analysis (FEA) of the proposed HFRC two-way slabs was also performed via ABAQUS. The outputs from numerical modeling showed a close agreement with the experimental results. Using the selected FEA model, an extensive parametric study was also done to examine the effect of various parameters including longitudinal reinforcement ratio, compressive strength of concrete, and the concrete cover of specimens. The proposed FEA model presented a close agreement with the experimental outcomes.

In this study, the response of different thin concrete panels of size 600 mm × 600 mm × 40 mm with and without reinforcements subjected to low-velocity impact under drop weight impact is carried out. For the purpose of comparison, concrete panels of different configurations such as simple cement concrete (PCC) free of any kind of reinforcements, textile reinforced concrete (TRC), and reinforced cement concrete (RCC) in addition to panels made with self-compacting concrete (SCC) were casted. The drop hammer impact test consists of a ball (weighing 1.8 kgs) with a drop height 600 mm is considered. The following parameters of the drop weight impact loading test such as number of blows for first crack, ultimate failure, and energy absorption characteristics were examined to arrive at the best configurations among the selected categories. It is observed that the panel made with self-compacting concrete has performed superiorly over all other cases considered in this study.

In this work, the impact of high stress gradients, found in bending of thin unidirectional fiber reinforced shells (~0.1 to 1 mm), on compressive micro-buckling failure, was analyzed. Such thin shells show increased resistance to compressive failure under high curvatures, which may even allow tensile fiber damage to drive ultimate failure for very low thickness (e.g., Composites Science and Technology, 216, ISSN:0266-3538, ISSN:1879-1050

The use of laminated bamboo in structural applications is increasing, but the failure mechanisms of the material need further investigation. This study investigated the failure of laminated bamboo under compressive loading using digital image correlation (DIC). Notably, the unique speckled appearance of a bamboo transverse section, resulting from the spatial distribution of vascular fibre bundles in the parenchyma matrix, was directly used for DIC; no sample preparation was necessary. A 45° degree shear face originated from the joint between several strips and led to the ultimate failure of the samples. However, when the strain exceeded ~ 30% the analysis broke down due to sections of the specimen shearing off the sample. Our methodology demonstrates the potential of directly imaging laminated bamboo during mechanical testing to reveal complex full-field in-plane strain distribution, and the development and on-set of failure in the material.

A mathematical model based on the first-order shear deformation theory and the von Karman’s nonlinear kinematics for buckling, postbuckling and failure analysis of elastic–plastic Functionally Graded Material (FGM) plate under thermomechanical is presented. The FGM plate with continuously varying properties along thickness is modeled as a laminate composed of multiple perfectly-bonded layers made of isotropic and homogeneous material having layer-wise constant composition. The thermoelastic properties of FGM are calculated using rule of mixtures and Tamura-Tomota-Ozawa model (TTO model). Whereas, the elastic–plastic material properties are evaluated in accordance with the TTO model, assuming the ceramic phase of FGM to be elastic and the metal phase to be elastic–plastic. Further, the elastic–plastic analysis of FGM is assumed to follow J2-plasticity with isotropic hardening. Parametric studies are conducted to investigate the effects of plasticity, material inhomogeneity, and thermomechanical loading conditions on the elastic–plastic buckling, postbuckling behavior, and the ultimate load capacity of FGM plate. The postbuckling response of FGM plate is found to be greatly affected by the plasticity consideration. FGM plate with elastic material properties exhibited a continuous increase in the postbuckling strength; whereas, the postbuckling strength of an elastic–plastic FGM plate decreases initially and finally, ultimate failure of the plate occurs.

Ultrabright x-rays capture the sequence of material damage accumulation during high strain rate catastrophic failure., Understanding high-velocity impact, and the subsequent high strain rate material deformation and potential catastrophic failure, is of critical importance across a range of scientific and engineering disciplines that include astrophysics, materials science, and aerospace engineering. The deformation and failure mechanisms are not thoroughly understood, given the challenges of experimentally quantifying material evolution at extremely short time scales. Here, copper foils are rapidly strained via picosecond laser ablation and probed in situ with femtosecond x-ray free electron (XFEL) pulses. Small-angle x-ray scattering (SAXS) monitors the void distribution evolution, while wide-angle scattering (WAXS) simultaneously determines the strain evolution. The ability to quantifiably characterize the nanoscale during high strain rate failure with ultrafast SAXS, complementing WAXS, represents a broadening in the range of science that can be performed with XFEL. It is shown that ultimate failure occurs via void nucleation, growth, and coalescence, and the data agree well with molecular dynamics simulations.

The phase field fracture method has emerged as a promising computational tool for modelling a variety of problems including, since recently, hydrogen embrittlement and stress corrosion cracking. In this work, we demonstrate the potential of phase field-based multi-physics models in transforming the engineering assessment and design of structural components in hydrogen-containing environments. First, we present a theoretical and numerical framework coupling deformation, diffusion and fracture, which accounts for inertia effects. Several constitutive choices are considered for the crack density function, including choices with and without an elastic phase in the damage response. The material toughness is defined as a function of the hydrogen content using an atomistically-informed hydrogen degradation law. The model is numerically implemented in 2D and 3D using the finite element method. The resulting computational framework is used to address a number of case studies of particular engineering interest. These are intended to showcase the model capabilities in: (i) capturing complex fracture phenomena, such as dynamic crack branching or void-crack interactions, (ii) simulating standardised tests for critical components, such as bolts, and (iii) enabling simulation-based paradigms such as Virtual Testing or Digital Twins by coupling model predictions with inspection data of large-scale engineering components. The evolution of defects under in-service conditions can be predicted, up to the ultimate failure. By reproducing the precise geometry of the defects, as opposed to re-characterising them as sharp cracks, phase field modelling enables more realistic and effective structural integrity assessments.

Reinforced concrete shear walls are generally used as predominant in-plane lateral force-resisting members in tall buildings. National Building Code of India has clauses guiding their design process as well as there are numerous research papers detailing empirical formulations that can be used for complicated designs. Many structural design related software packages come with comprehensive shear wall modelling, analysis and designing modules. But in performance-based design philosophy it is necessary to consider not only the strength and the stiffness aspects of a shear wall but also its performance and its ultimate failure mode when subjected to strong dynamic loads. Especially RC shear walls present more challenges when it comes to accurate modelling and design because of the heterogeneous nature of concrete, variable concrete-aggregate and concrete-rebar bonding, strength degradation or pinched hysteretic behaviour, etc. This paper presents a summary of literature available of performance-based design methodologies and their applicability to the design of reinforced concrete shear walls.

A beam which has openings in its web portion is called castellated beam. For the preparation of castellated beams, fabrication of I section is done by cutting web portion and subsequently re-joining it one above the other. The popularity of castellated beams measures its advantageous structural applications. It expands the lives of millions every day combined with our pioneering business facilities. The objective of this research paper is to investigate new angle of web opening of the diamond shape in comparison with hexagonal and rectangular web opening to determine the ultimate load-carrying capacity and to avoid shear stress concentration at the corner of the rectangular and hexagonal opening which is responsible for failure of castellated beam. This paper studies the deflection performance and ultimate load-carrying capacity of castellated beams with a diamond, hexagonal and rectangular opening. To identify experimental results of this research, 24 beams were fabricated, tested and results are validated using ANSYS software. The variable considered in this research is the angle of opening 30°, 45° and 60° for diamond. The length of the opening for diamond and rectangle of castellated beams is equal. It is concluded that the ultimate load-carrying capacity of diamond web opening with 30° angle of opening is 47.86% more and has 47.5% less deflection compared to the hexagonal opening. The average load-carrying capacity of diamond web opening is 44.21% more and deflection 44.00% less than rectangular web opening.