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Tunnels in fractured rock masses are typically damaged by dynamic disturbances from various directions. To investigate the influence of blasting load directions on the stability of a tunnel with a pre-crack nearby, blasting tests were conducted on the physical models of an external crack around a tunnel (ECT) in this study. Failure modes of the tunnels were analysed based on stress wave theory. The Riedel–Hiermaier–Thoma (RHT) material model was employed to perform the numerical simulations on ECT models. Stress distribution around the tunnels and final failure patterns of the tunnels were characterised. The results show that, under blasting loads, the pre-crack propagates and then new cracks initiates on the incident side of the tunnel. These cracks extend towards each other and eventually coalesce. Blasting load directions significantly influence the ultimate failure mode of the tunnel in the fractured rock masses. The new cracks on the shadow side of the tunnel appear at different positions when the blasting stress waves come from various directions. The results are meaningful to the analysis of tunnel stability and optimisation of the tunnel support scheme.

The influence of nano-silica addition on the durability of concrete has been studied. Nano-silica particles (0 to 3 wt%) by cement were incorporated in the concrete and their effect on abrasion and impact resistance was analysed after 56 days. The test results showed that the abrasion loss of concrete reduces as the content of the nano-silica increases. In M 30 and M 40 grade concrete, with addition of 3 % nano-silica abrasion loss was decreased by 29.82 % and 52.21 % respectively when compared with concrete without nano-silica. The impact resistance of concrete also dramatically improved with the rise in nano-silica content. The number of blows required for ultimate failure was increased by 207.69 % and 304.16 % for M 30 and M 40 grade concrete mixes with 3 % nano-silica. The relationship between abrasion loss and compressive strength has been established, suggesting that the stronger the concrete, the more resistance it offers to wear. Nano-silica can be used to produce concrete that is both stronger and more durable.

Background The purpose of this study was to evaluate the ultimate failure load and stiffness of two patellar fixation techniques for medial patellofemoral ligament (MPFL) reconstruction: (1) quadriceps tendon fixation (QT), (2) single tunnel (STG) patella fixation with gracilis autograft. Methods A total of 16 fresh-frozen cadaveric knees (eight matched pairs) were randomized into two groups (QT vs. STG). The MPFL reconstructions were subjected to cyclic loading for 10 cycles to 30 N and then tested to failure at a constant displacement rate of 15 mm/min using a materials-testing machine (MTS 810 Universal Testing System). Failure mode, ultimate failure load and stiffness were recorded for each cadaveric specimen. Results There was no significant difference in mean ultimate failure load among groups (P = 0.35). The STG group failed at a mean ultimate load of 190.04 N [standard deviation (SD) 23.18] and the QT group failed at 206.24 N (SD 37.99). The STG group had a mean stiffness of 21.38 N/mm (SD 1.44). This was not significantly higher than the mean stiffness value achieved for the QT group at 20.36 N/mm (SD 1.3) (P = 0.19). In the QT group all reconstructions failed due to tendon rupture at the patella attachment. The reason for failure in the STG group was the graft–suture connection. Conclusions This cadaver study showed no statistically significant difference in biomechanical performance of the evaluated patella fixation techniques, in terms of maximum load to failure and stiffness. Both techniques are reliable in terms of biomechanical properties and could offer additional surgical solutions.

Reinforced concrete (RC) slabs of highway bridge decks are gradually deteriorated due to the traffic vehicle wheel-loading. Fatigue is one of a number of possible causes for the deterioration. Cantilever RC slabs of the bridge are also damaged by fatigue loading. To increase the fatigue durability of the bridge deck slab, the near-surface mounted (NSM) technique is used with carbon fiber reinforced polymer (CFRP) rods embedded in the RC slab as an effective strengthening method. This study presents the fatigue characteristics of cantilever RC slabs strengthened with CFRP rods with a high-modulus of elasticity. A cantilever RC slab specimen with embedded CFRP rods with high moduli was constructed on a moving-wheel load testing machine and tested for approximately 11 months. The slab had a minimum thickness of 160 mm (as stipulated by the Japanese design code), and the minimum number of steel reinforcements was embedded to ensure (negative) flexural failure of the RC slab where CFRP rods were not used. During the test, the CFRP strengthened slab specimen was subjected to a negative bending moment from repeated moving-wheel loads. Very limited experimental data are available for the evaluation of the structural behavior of cantilever bridge decks subjected to wheel loads. Therefore, the moving-wheel fatigue experiment of the cantilever RC slab with NSM CFRP rods would be useful information for strengthening. The moving-wheel loading test confirmed the increase in fatigue durability of the CFRP strengthened slab as the slab specimen endured approximately 3.56 million equivalent-cycles at an initial load of 60 kN, which was 32% higher than the designed service load. The experimental investigation revealed that the ultimate failure of the cantilever slab was punching shear failure attributed to the rupture of the CFRP rods.

In this research, the plate embedded parts and grooved embedded parts reinforced concrete structures were investigated. Two types of plate embedded parts and three types of grooved embedded parts experienced coating treatment to enable sustainable function. Later, the ultimate failure capacity by bending experiments was conducted and compared with the theoretically calculated results. Moreover, three grooved embedded parts were simulated by ABAQUS to compare the results with the experimental exploration results, which was in close agreement with the theoretically calculated results and finite element analysis results. The result indicated that the failure modes of the embedded specimens under the five working conditions are all concrete vertebral failure. The plate-type embedded components were proved to exhibit higher ultimate bearing capacity than the grooved embedded parts. Moreover, the flexural and shear capacity of these five types of embedded parts has not been fully developed. The ultimate flexural and shear capacity of these five types of embedded parts could be further explored by adjusting the higher concrete grade.

Interfacial adhesion between polymer matrix and reinforcing silica nanoparticles plays an important role in strengthening polypropylene (PP) composite. To improve the adhesion strength, the surface of silica nanoparticles can be modified by grafted functional molecules. Using atomistic simulations, we examined the effect of functionalization of silica nanoparticles by hexamethyldisilazane (HMDS) and octyltriethoxysilane (OTES) molecules on the deformation and failure of silica-reinforced PP composite. We found that the ultimate tensile strength (UTS) of PP composite functionalized by OTES (28 MPa) is higher than that of HMDS (25 MPa), which is in turn higher than that passivated only by hydrogen (22 MPa). To understand the underlying mechanistic origin, we calculated the adhesive energy and interfacial strength of the interphase region, and found that both the adhesive energy and interfacial strength are the highest for the silica nanoparticles functionalized by OTES molecules, while both are the lowest by hydrogen. The ultimate failure of the polymer composite is initiated by the cavitation in the interphase region with the lowest mass density, and this cavitation failure mode is common for all the examined PP composites, but the cavitation position is dependent on the tail length of the functional molecules. The present work provides interesting insights into the deformation and cavitation failure mechanisms of the silica-reinforced PP composites, and the findings can be used as useful guidelines in selecting chemical agents for surface treatment of silica nanoparticles.

This paper presents the results of an experimental study performed on concrete structural walls subjected to vertical and cyclic lateral loads. The purpose of the study is to experimentally investigate the seismic behavior and performance of composite steel–concrete coupled walls with regular openings and conventional reinforced coupling beams. The paper also addresses the manner in which the use of steel fibers reinforced concrete and various composite steel–concrete connections influence the hysteretic performance of the walls. Four of the total five experimental specimens had centrally aligned openings, while the fifth one was designed as a solid wall and served as reference. The experimental specimens present various cross-sectional arrangements, thus the testing matrix comprises of a total of three composite steel–concrete walls with central openings (CSRCW) with steel profiles partially embedded on the edges, one conventional reinforced concrete wall (RCW) with central openings and the solid specimen, which is also a composite steel–concrete wall. Based on the experimental results, it was observed that by embedding supplementary steel fibers in the concrete matrix, the ductility loss due to openings could be regained and significantly improved. The composite connection between structural steel and concrete web panel of the walls could successfully resist until the specimens reached the ultimate failure. The paper therefore concludes on the performance of various structural solutions and details by highlighting strengths and weaknesses of the systems.

In order to make the main cable saddle structure lighter and reduce the cost, it is necessary to conduct in-depth research on the force transmission path, failure mode and ultimate bearing capacity of the main cable saddle. A parametric geometric model was established based on Autodesk Inventor software and imported into the large-scale general-purpose finite element software ABAQUS for numerical simulation research under ideal elastoplastic state, and the mechanical properties and ultimate bearing capacity of the main saddle were systematically studied. A structural optimization method with safety factor as the goal was proposed, and the original design was optimized for structural size. Then, the ultimate bearing capacity state of the cable saddle considering the influence of the steel's post-buckling strength is analyzed, and the structural bearing capacity evaluation index is proposed. The analysis results show that the ultimate bearing capacity of the preliminary design cable saddle is 3.00 times the design load, and it has sufficient safety reserves; the ultimate failure state of the cable saddle is the formation of a plastic hinge at the junction of the transverse rib, saddle channel cast steel and the web; By quantitatively analyzing the development of the plastic zone of each component of the cable saddle, the force transmission path and failure process of the structure can be analyzed more clearly, which provides a basis for the structural optimization of the cable saddle; and obtain the steel consumption under different safety factor target values (2.5, 2.0, 1.85, 1.5, 1.25), for example, when the safety factor target is 1.85, 38.8% of steel can be saved; when considering deformation index control, it is recommended that the target safety factor of the ideal elastoplastic analysis control is not less than 1.82.

To investigate the crack evolution of Longmaxi shales with a single prefabricated fissure, a CCD (charge coupled device) camera and AE (acoustic emission) monitoring equipment were employed. On the basis of real-time CCD photographs and AE events, a real-time crack evolution process in fissured shale specimens under uniaxial compression was investigated. The crack initiation angle and extension angle were calculated, the relationship between the crack initiation stress, strength, and crack angle was compared, and the proportion of tensile and shear cracks at different stages of the whole compression process was briefly analyzed. The results demonstrate that, with the increase in fissure angle (α), the weakening ability of the prefabricated fissure to uniaxial compressive strength and crack initiation stress was reduced. The initial cracks and secondary cracks always appeared at the tip of the pre-existing fissure in the form of tensile cracks for α = 30–90°. The crack initiation angle and expansion angle increased first and then decreased rapidly with α increasing. Furthermore, the ultimate failure modes were mixed tensile and shear failure when α = 0–90°. The crack evolution of the fissured shale was progressive, but the final failure of the fissured specimen occurred rapidly. Furthermore, the appearance of the cracks, stress drops, and AE counts had good consistency in time.

Background:. Multiple techniques are commonly used for posterior cruciate ligament (PCL) reconstruction. However, the optimum method regarding the fixation of PCL reconstruction after PCL tears remains debatable. The purpose of this study was to compare the biomechanical properties among three different tibial fixation procedures for transtibial single-bundle PCL reconstruction. Methods:. Thirty-six porcine tibias and porcine extensor tendons were randomized into three fixation study groups: the interference screw fixation (IS) group, the transtibial tubercle fixation (TTF) group, and TTF + IS group (n = 12 in each group). The structural properties of the three fixation groups were tested under cyclic loading and load-to-failure. The slippage after the cyclic loading test and the stiffness and ultimate failure load after load-to-failure testing were recorded. Results:. After 1000 cycles of cyclic testing, no significant difference was observed in graft slippage among the three groups. For load-to-failure testing, the TTF + IS group showed a higher ultimate failure load than the TTF group and the IS group (876.34 ± 58.78 N vs. 660.92 ± 77.74 N [P

Rocks with layered structure (bedding or foliation) usually exhibit different levels of anisotropy in terms of mechanical properties. The structural anisotropy has pronounced influence on the failure process of anisotropic rock. However, relatively few studies have been carried out on the subject. In this paper, the failure processes of a foliated gneiss with different schistosity orientations under uniaxial compression were studied based on digital speckle correlation method. The results show that the evolution process of full-field strain of the gneiss is closely related to the schistosity orientation. More specifically, when β = 0°, the strain concentration zone mainly originates from the microstructure, and the potential failure plane cannot be observed before total failure. When β = 30° or 60°, there are several strain concentration strips before failure. The ultimate failure is due to the interaction among these strips under the action of local stress field. When β = 90°, the initiation and evolution of strain concentration strip is relatively stable. When tensile failure occurs along the schistosity, the crack opens abruptly during loading. In contrast, the crack presents a gently stable growth trend, when the shear failure occurs along the schistosity.

To compare the biomechanical properties of metallic anchor (MA) and all-suture anchor (ASA) constructs in the anatomic reattachment of the lateral ulnar collateral ligament complex to its humeral insertion.Twenty paired male human cadaveric elbows with a mean age of 46.3 years (range: 33-58 years) were used in this study. Each pair was randomly allocated across 2 groups of either MA or ASA. A single 3.5-mm MA or 2.6-mm ASA was then inserted flush into the lateral epicondyle. A dynamic tensile testing machine was used to perform cyclic loading followed by a load to failure test. During the cyclic loading phase, the anchors were sinusoidally tensioned from 10 N to 100 N for 1,000 cycles at a frequency of 0.5 Hz. In the load to failure test, the anchors were pulled at a rate of 3 mm/s. Load at 1-mm and 2-mm displacement, as well as load to ultimate failure were assessed. Clinical failure was defined as displacement of more than 2 mm. Normality of data was assessed with the Shapiro-Wilk test. Continuous data are presented as medians and compared with the Mann-Whitney U test and categorical data was compared with the χDisplacement was significantly greater for the ASA group during cyclic loading starting from the tenth cycle (P.05). Displacement of more than 5 mm within the first 100 cycles was observed in 2 anchors in the ASA group. No difference was observed in loads required to displace 1 mm (MA: 146 N [6-169] vs ASA: 144 N [2-153]; P = .53) and 2 mm (MA: 171 N [13-202] vs ASA: 161 N [9-191]; P = .97), but there was a statistically significant difference between ultimate loads in favor of ASA in the load to failure test (MA: 297 N [84-343] vs 463 N [176-620]; P.01).In the cyclic test, no difference in clinical failure defined as pull-out of more than 2 mm was observed between 3.5 mm MAs and 2.6 mm ASAs. In the ultimate load to failure analysis, no difference was observed between groups in force causing 1 and 2 mm of displacement, but there was a significant difference in favor of ASA in the pull to ultimate failure test.Potential benefits of all-suture anchors include preservation of bone stock, reduced radiographic artifacts, and easier revisions. Although their use has been investigated thoroughly in the shoulder, there remains a paucity of literature regarding displacement and pull-out strength in the elbow.

Purpose In this study we compare the biomechanical properties of a novel suture technique that we developed called the continuous double knots technique for repairing flexor tendon injuries with the standard 4-strand double-modified Kessler technique. Methods This was an experimental study. Eighty porcine flexor digitorum profundus tendons were harvested and divided randomly into two groups of 40. The first group (N = 40) was repaired using the 4-strand double modified Kessler technique and the second group (N = 40) was repaired using our new continuous double knots technique. The two groups were randomly divided and the ultimate failure load (n = 20) and cyclic testing to failure (n = 20) were compared. Results The mean ultimate failure load was 25.90 ± 7.11 (N) and cyclic testing to failure 88 ± 47.87 (cycles) for the 4-strand double modified Kessler technique and 34.56 ± 6.60 (N) and 189 ± 66.36 (cycles) for our new continuous double knots technique. The T-test revealed a significant difference between the 2 techniques (p Conclusions The continuous double knots technique suture technique had significantly higher maximum tensile strength and cyclic testing than the 4-strand double modified Kessler technique in an in vitro study, and in thus an optional technique for flexor tendon repair.

Based on the concept of environmental protection of solid waste utilization, material testing is conducted to achieve native improvement using coal gangue-based limestone-calcined clay cement (LC3). Finite element (FE) models of rural raw-soil architecture with a colored-steel roof (RACSR) were established. The effect of modified soil type and seismic character on the vulnerability of single-story raw-soil structures was investigated using probabilistic seismic demand (PSD) analysis. The seismic response characteristics of 80 representative sequences were comparatively investigated when subjected to northwest clay (raw soil) of China, fiber and stone-improved clay (modified soil), and coal gangue-based limestone-calcined clay cement (LC3 soil). The maximum interstory drift angle (ISDAmax) was lower in the LC3 soil model and the modified soil model compared to the raw-soil model. The use of LC3 soil improves structural resistance and reduces the damage probability of a structure, and the influence of different ultimate failure states on the vulnerability of the raw-soil structure was studied.

Background: The Pulvertaft weave was described more than 50 years ago and is still used in tendon transfers. The aim of this study was to evaluate the strength of a modified core suture Pulvertaft weave technique and compare it to the original Pulvertaft weave traditionally used in tendon transfer surgery. Methods: 12 extensor pollicis longus tendons and extensor indices proprius tendons were harvested from fresh frozen cadavers. Six Pulvertaft weaves were performed using FiberWire 4.0 and six core suture tendon weave were performed using FiberLoop 4.0. Biomechanical analysis was performed and stifness, first failure load and ultimate failure load were measured for both set of repairs. Results: The stiffness of the core suture tendon repair (9.5 N/mm) was greater than that of the Pulvertaft repair (2.5 N/mm) The first failure load of the core suture tendon repairs (68.9 N) was greater than the Pulvertaft repairs (19.2 N) and the ultimate failure load of the core suture tendon repairs (101.8 N) was greater than the Pulvertaft repairs (21.9 N). All of these differences were statistically significant. Conclusions: The core suture Pulvertaft weave is a modification to the Pulvertaft weave used in tendon transfers. The results of this cadaveric study suggest it is 5 times stronger than the traditional Pulvertaft repair, potentially allowing it to be used with early active motion protocols after tendon transfers.

In order to solve the complex load transfer and structural design of the joint structures including skin, longeron and frame in the composite fuselage, the adhesively bonded integrated composite joint was designed. Static tensile test was performed and the strain-load curves and damage modes were obtained. Then the numerical simulation model of integrated composite joint was built. The damage initiation, propagation and failure process of integrated composite joint under tensile load were simulated and analyzed. Results show that: the first load drop and the ultimate failure load of the joint are 120.82 kN and 168.11 kN respectively; the initial damage occurs at the corner bend region of the lower-left corner-shaped preform, and extends across the radius bend region among short flange, long flange and web, and leads to the interface debonding of the upper and lower corner-shaped preform and the delamination of corner-shaped preform and L-shaped preform. Compared with the experimental results, the errors of the first load drop and the ultimate failure load from numerical calculated results are 6.68% and 2.61% respectively, which agree with each other very well.

The main objectives of this study are: encouraging the production and use of self-compacting concrete, use of materials which are lightweight, easy to use, and highly efficient in the retrofitting of reinforced concrete buildings. Six deep beams specimens (L= length of 1400mm, h= height of 400mm, and b= width of 150mm) were cast using self-compacting concrete. The location of the openings is in the middle of assumed load path. Five patterns were adopted to arrange carbon fiber reinforced polymer (CFRP) strips. The cylinder compressive strength of the concrete was approximately equal for all beams and was about (44 MPa) at 28 days age. All the beams have the same steel reinforcement for shear and flexure. There have been many tests for fresh and hardened concrete. The reinforced concrete deep beams were tested up to (60%) of the ultimate load of control beams to simulate degree of damage, and then released the load. After that, the beams were retrofitted using (CFRP) strips, and then the beams were tested to failure. The study was focused on determining the vertical mid-span deflection, ultimate load, the load that causes first shear and flexural cracks, and mode of failure. The results showed that, the best increase in the ultimate failure load was (27.27%) and achieved using the inclined strips pattern and the pattern of vertical and horizontal strips together. Reduction in the deflection values for the retrofitted beams compared to the control beam by about (12-13%) due to restrictions imposed by CFRP strips and the...

The nonlinear behavior of reinforced fly ash concrete (RFAC) beams until the ultimate failure is highly a multifaceted phenomenon due to the contention of heterogeneous material properties and the cracking behavior of concrete. This paper represents an exploration of nonlinear finite element analysis of reinforced concrete beams with the inclusion of fly ash under flexural loading. Finite element modelling of RFAC beams is carried out using a distinct reinforcement modelling method. The capability of the model to capture the critical crack regions, loads and deflections for various loadings in RFAC beams has been evaluated. Comparison is made between experimental results and finite element modelling with respect to crack formation and the ultimate capacity for flexural loading and mid-span deflection. The achieved results in the present study indicate acceptable approximation with those in the previous investigations.

An experimental system, which consists of a digital camera and a loading system, is designed to investigate the failure mechanism of anti-dip rock slopes subjected to external loading. The modeling material is made by mixing sand, plaster, barite, glycerin, and water at a mass ratio of 44.4:30:22.5:2:32. Fine sand is evenly filled between the rock layers to simulate the joints of the anti-dip rock slopes. Anti-dip rock slope models with joint angles of 45°, 55°, 65°, and 75° are poured in the experiment. The complete load–displacement curves of the anti-dip rock slopes subjected to external loading are obtained to investigate the effects of the joint angle on the ultimate bearing capacities of the slopes. Based on the images captured by the digital camera under the high-speed shooting mode, the whole failure process of the anti-dip rock slopes is analyzed, including the crack evolution. Moreover, an image processing technique is proposed to capture the displacement vector diagrams of anti-dip rock slopes and the real-time deformation behavior of anti-dip rock slopes is investigated. The ultimate failure modes of the anti-dip rock slopes with different joint angles are discussed in detail. The sliding body is separated from the slope along the datum plane, which is always perpendicular to the slope joints. Failures occur at the top of the anti-dip rock slopes (near the external loading), while the bottom of the slopes remain intact. Based on the experimental results, the failure mechanism of the sliding blocks in the anti-dip rock slopes is revealed. The experimental results can be expected to assess the failure mode of anti-dip rock slopes subjected to external loading.

The seismic behavior of special-shaped concrete-filled steel tubular (CFST) column to H-shaped steel beam plane frame (SCFSTF) with vertical rib connections was investigated experimentally and numerically in this study. Double-bay two-story SCFSTFs with the scale ratio of 1/2 were tested under constant vertical compressive load and cyclic horizontal loads (or displacements), which is a pseudo static experiment considering the axial load ratio. Based on the experimental results, failure modes, bearing capacity, hysteretic curve, skeleton curve, energy dissipation, ductility, rigidity degradation and strength degradation of SCFSTFs were investigated. As a result, a typical strong column-weak beam failure mode was determined. The degradation in strength and rigidity were minimal and energy dissipation capacity and ductility of frames were adequate, demonstrating excellent seismic performance. Besides, energy dissipation capacity and horizontal resistance were improved with axial load ratio increasing within the parametric range of this test. After the test, a finite element method based on software ABAQUS was carried out to further investigate the seismic performance. The numerical results of skeleton curve, rigidity, yield load, peak load and stress distribution agreed well with the test results. The plastic hinge formation process and ultimate failure mode were further investigated using the finite element model.

Purpose To investigate the graft diameters and mechanical properties of hamstring tendons sutured using different materials and techniques. Methods This study used 30 fresh, frozen human cadaveric semitendinosus tendons; the free ends of 10 specimens each were sutured by 2 No. 3 braided polyester sutures with the Krackow technique (BP group), SutureTape with the Krackow technique (ST group), or SutureTape Loop with the locking SpeedWhip technique (SL group). First, the changes in graft diameter from before suturing to after suturing were investigated. Each graft was pre-tensioned to 100 N for 3 cycles and then cyclically loaded to 200 N for 200 cycles. Elongation after cyclic loading and displacement in the 200th cycle were calculated. Finally, each specimen was loaded to failure. The ultimate failure load and stiffness were analyzed. These mechanical properties were statistically analyzed using 1-way analysis of variance. The level of statistical significance was set at P Results In the BP group, the changes in graft diameter were significantly larger than those in the ST and SL groups (P = .001). The elongation values after 200 cycles in the BP and ST groups were 3.1 ± 2.0 mm and 5.9 ± 3.4 mm, respectively. In the SL group, elongation (7.7 ± 3.6 mm) was significantly larger compared with that in the BP group (P = .037). In contrast, displacement in the 200th cycle was significantly smaller in the ST and SL groups compared with the BP group (P = .017). No statistically significant difference was evident for the ultimate failure loads among the 3 groups (P = .543). Conclusions The results of this study suggest that SutureTape may be an appropriate option for preparing the hamstring graft in anatomic anterior cruciate ligament (ACL) reconstruction. Clinical Relevance This biomechanical study shows the effectiveness of SutureTape in ACL graft preparation. Clinically, SutureTape may be of benefit in single- or double-bundle ACL reconstruction.

In this paper, the structural behavior of masonry panels strengthened with a system made up of composite fiber grids embedded in a cementitious matrix (FRCM) is presented. The non-linear behavior of the unreinforced and reinforced panels is numerically simulated by means of a simplified micro-modelling approach. This approach concentrates all the non-linearities and failures in the joints and in potential crack surfaces within the bricks, placed vertically in the middle of each brick. The FRCM strengthening system is discretized by a continuous bi-directional fiber grid constituted by trusses embedded into a cementitious matrix. A calibrated bond-slip relationship is applied between the fibers and the mortar matrix assuming an idealized bilinear law. The typical experimental load–displacement curve for a FRCM strengthened panel shows three principal phases that correspond to different failure mechanisms: masonry cracking, mortar matrix cracking and ultimate failure of the panel. The non-linear numerical analyses show a good agreement with experimental results and the modeling approach is found to be adequate to reproduce the described experimental behavior. The results of a parametric study on both the material and the geometrical properties of the FRCM system are also presented.

In this study, a centrifuge modelling system has been developed, in which the loading process from design conditions to the ultimate failure conditions can be simulated on an embedded wall in soft rock at a constant centrifugal (50g) acceleration. Soft sand rock was artificially modelled by using a sand−cement−clay mixture. In-flight excavation and the lateral loading processes were simulated by means of draining water from the wall front and feeding water to the retained soil side, respectively. Two centrifuge model tests have been carried out to investigate the influence of embedment depth on the stability of large-stiffness cantilever walls having flexural rigidity equivalent to a 2·5 m steel tubular pile wall. The results observed reveal that the wall can stand in the design condition with relatively small embedment depth, and provides a reasonable safety margin against ultimate failure. The stiff cantilever walls move by rigid-body rotation about a pivot point under ultimate loads, and a small increment in the embedment depth – for example, 20% – can significantly increase the stability of the wall considered in this study. A compression failure of the embedded medium at the shallow wall front and a shear wedge failure at the wall back from the wall toe were observed.

The present work emphasizes the effects of hygrothermal aging on the bolted joints prepared from carbon/epoxy nanocomposites at different bolt preloads. The effect of multiwalled carbon nanotubes (MWCNT) was investigated by incorporating 0.1 to 0.5 wt.% of MWCNT in composite laminates with 0.3 wt.% of MWCNT giving the best mechanical properties. The water absorption studies at three hygrothermal conditions i.e., 25 °C, 45 °C, and 65 °C for 30 days, were conducted for neat and 0.3 wt.% of MWCNT added composite specimens, as per ASTM D5229. The bolted joints were designed using ASTM D5961 having a width to diameter ratio (W/D) and edge to diameter ratio (E/D) equal to 6 and 5, respectively. The bolt torque effect at different levels i.e., 0, 2, and 4 Nm were studied to estimate the ultimate failure loads in the nanocomposite joints. In all aspects, incorporating MWCNT shows better results than neat configured composites. The statistical investigations were performed using the central composite design on different control factors i.e. temperature, duration, bolt torque, and material.

PurposeThe prediction of accurate failure strength and a composite laminate failure load is of paramount importance for reliable design. The progressive failure analysis helps to predict the ultimate failure strength of the laminate, which is more than the first ply failure (FPF) strength. The presence of a hole in the laminate plate results in stress concentration, which affects the failure strength. The purpose of the current work is to analyze the stress variation and progressive failure of a symmetric laminated plate containing elliptical cutouts under in-plane tensile loading. The effect of various parameters on FPF and last ply failure (LPF) strength is studied.Design/methodology/approachThe ply-by-ply stresses around elliptical cutouts are obtained analytically using Muskhelishvili's complex variable formulation. To predict the progressive failure, Tsai–Hill (T-H) and Tsai–Wu (T-W) failure criteria are used, and depending on the mode of failure, lamina modulus is degraded.FindingsThe study has revealed that fiber orientation and stacking sequence for given loading have the most significant effect on the laminate's failure strength.Originality/valueComplex variable method and conformal mapping are simple and proficient for studying failure analysis of a laminated plate with elliptical cutout.

The grouted mortise-tenon joint, invented as the connection between the large prefabricated elements, is the most important component in the prefabricated underground structures. This paper conducts analysis of load-carrying capacity performance and failure mode with 1 : 1 prototype test in key working direction of different double mortise-tenon joint types for the prefabricated metro station. The resistance moment is developed and used to analyze the bending bearing characteristic curve, and the corresponding test results of each stage of the characteristic curve are described in detail. In addition, the bending bearing performance of different types of double-tenon joints under different load conditions is compared. The test results clarify the ultimate failure mode of double-tenon joint and the variable bearing capacity characteristics of the joint with the increase in axial load and explain the bearing performance of each stage. It is also found the auxiliary pretightening device is helpful to delay the appearance of cracks and improve the bearing capacity, especially when it is set on the tension side. The research results have important application value for the joint design of prefabricated metro station structures.

UHPC has high strength, high toughness, and excellent durability. For orthotropic steel bridge deck pavement, UHPC can significantly increase the bridge deck’s stiffness and then solve the problems of fatigue cracking and pavement damage of the bridge deck. However, if UHPC adopts cast-in-place construction, its self-shrinkage can easily cause shrinkage cracks, and it requires high maintenance conditions. Meanwhile, the traditional stud connection will bring a great deal of welding work and cause welding fatigue. In contrast, prefabricated UHPC pavement and orthotropic steel bridge deck can greatly reduce the amount of welding of studs on the bridge deck through epoxy bonding, thus speeding up the construction process and avoiding the risk of cracking caused by UHPC self-shrinkage. In order to consider the influence of the surface state of interface and ratio of shear span to depth on flexural behavior of epoxy adhesive prefabricated UHPC-steel composite bridge deck, positive bending moment loading test with different ratios of shear span to depth was carried out, and the failure mode, load-deflection curve, interface slip, and strain distribution of the specimens were obtained. Finally, based on the cohesive interface element, the prefabricated UHPC-steel epoxy bonding interface was successfully simulated. The test results show that each specimen’s loading stage can be divided into the elastic stage, crack initiation stage, interfacial crack propagation stage, interface failure stage, and yield stage. The specimen’s ultimate failure is that the interface failure is prior to the yield at the bottom of the steel plate. During the loading process, the bending performance shows that the ultimate load P B i and growth deflection Δ δ B i C i of CD-ERA-P-λ4.44 are higher than those of other specimens in terms of the load-deflection curve. The ultimate load of CD-ERA-P-λ3.33 is lower than that of CD-ERG-P-λ3.33, which decreases by 4.6%, but the increasing deflection increases by 75%. Simultaneously, the interface slip of the specimen is similar, which further shows that the specimen has the best bending performance when the surface of the steel plate is rough (R) and the surface of the prefabricated UHPC plate is grooved (A). No matter what kind of surface is used at the interface, the reduction of the ratio of shear span to depth will aggravate the ultimate failure of the interface and the cracking of the precast UHPC slab. Finally, the bending performance of epoxy adhesive prefabricated UHPC-steel composite bridge deck is successfully simulated based on the cohesive interface element, which is verified by the test results.

Cold-Formed Steel sections are commonly used in residential and commercial buildings as purlins, side girts, portal frames and moment resisting frames. The bolted moment connections can be used connect the different structural components of these buildings together. These connections allowing the transfer of the internal forces of the structures such as axial forces, shear forces, bending moments and torsion. The main objective of this paper is to study numerically the behavior of the apex bolted moment connection for cold formed sections. The deflection and the stress distribution at critical sections for unstiffened 2C (double back-to-back) CFS were investigated for two cases, in the first case connecting single gusset plate was used, while in the second case two connecting double gusset plates with cutting compression flange were used. A finite element modeling was developed by using the ANSYS workbench v19.2 finite element code to simulate the apex connection of cold-formed steel sections. The considered beams had span lengths of 4000 mm with nominal web depths of 150 mm. and wall thickness 2.0 mm. A validation for the numerical model with experimental results is executed. Parametric study concerning the connecting plate thickness, no of connecting bolts used and different bolts pretension forces are presented. Based on this analysis the deflections and ultimate failure load and failure modes of specimens were studied and presented.

Purpose: To investigate the biomechanical influence of differential loading of suture strands (torque) on the fixation strength of knotted and knotless all-suture anchors. Methods: The biomechanical strength of 48 all-suture anchors was evaluated for 4 conditions in polyurethane foam blocks: (1) 12 knotted all-suture anchors loaded proportionately, (2) 12 knotted all-suture anchors with 1 suture strand bearing 50% of total force (partial torque), (3) 12 knotted all-suture anchors with 1 strand fixated and the other loaded (full torque), and (4) 12 knotless all-suture anchors with the loop kept open via a fixed rod. Force for 1 mm and 2 mm of displacement and ultimate failure load were assessed. Results: For 1 mm of displacement, groups 2, 3, and 4 showed significantly lower forces than group 1 (all P < .001), with no statistically significant difference between groups 2 and 3 (P = .516); for 2 mm of displacement, all groups showed significantly lower forces than group 1 (P < .001), which positively correlated with applied torque. No differences in the mean ultimate loads observed between testing groups 1, 2, and 4 were noted, with 93.3 ± 3.8 N, 91.4 ± 4.7 N, and 92.6 ± 5.6 N, respectively; however, group 3 exhibited a significantly lower mean ultimate load (62.3 ± 1.7 N) than all other groups (P < .001). Conclusions: The ultimate failure load of knotted and knotless all-suture anchor fixation was partially affected by loading differentials between strands in this validated foam block model. Differential loading of knotted all-suture anchor fixation presented greater initial displacement when compared with symmetrically loaded knotted all-suture anchors. Despite an initial increase in displacement, knotless all-suture anchors showed similar ultimate failure loads to knotted all-suture anchors with strands loaded equally. Clinical Relevance: The role of suture strand loading imbalance on anchor fixation is variable and should be considered during placement and fixation of the repair constructs in a clinical setting.

Composite patch repairs are an alternative to weld repair methods to arrest crack growth in metal plates. While these repairs have been effective, it has been difficult to use basic linear elastic fracture mechanics (LEFM) theories and design methods based on LEFM to predict the efficacy of patch repairs because the repaired plate exhibits bending and significant crack tip plasticity. In this investigation, we have studied the effect that one-sided low modulus composite patch repairs have on the development of crack tip plasticity on the free surface and through the thickness using large strain area and volume, total axial stress balance, and the free surface J-integral. Digital Image Correlation (DIC) and three-dimensional finite element analysis with first order elements were used to understand the evolution of crack tip plasticity and strain energy release rate to develop a simplified prediction method identifying a characteristic crack opening displacement prior to crack tip behavior of a one-sided composite patch repaired Center-Cracked Tension (CCT) specimen transitioning from Small Scale Yielding (SSY) to Large Scale Yielding (LSY), and eventually the re-initiation of crack growth. This method was then validated by comparing the predicted characteristic transition load to observed ultimate patched CCT specimen load capacity. Results correlated well with predictions when the composite patch was perfectly bonded to the aluminum and predicted characteristic transition loads more than 90 $$\%$$ greater than LEFM based failure predictions and 25 $$\%$$ lower than observed ultimate failure loads, demonstrating the potential to use this method for patch repair optimization.

In the present work, the hygrothermal aging effect was studied on the performance of bolted joints prepared from electron beam (EB) cured carbon/epoxy nanocomposites under varying bolt torques. The multiwalled carbon nanotubes (MWCNTs) at different wt.% varying from 0 to 0.5 were added into the composite laminates with 0.3 wt.% giving the maximum tensile strength. The comparison of mechanical properties was done for thermally cured, EB cured (without post curing) and EB cured (post curing) composites. For hygrothermal aging of neat and 0.3 wt.% MWCNT configurations, water absorption studies were conducted at three different water temperatures i.e., 25 °C, 45 °C, and 65 °C for 30 days, as per ASTM D5229. The mechanical strength retention of aged composite specimens were analysed. Using ASTM D5961, the bolted joint specimens were prepared to investigate the bearing response and ultimate failure loads in the composite bolted joints. The damage occurred due to hygrothermal conditions has been interpreted in the light of their morphological structures.

The purpose of this study was to compare the maximum load to failure and stiffness of three medial patella-femoral ligament (MPFL) reconstruction techniques: (i) suture anchor fixation (SA), (ii) interference screw fixation (SF), and (iii) suture knot (SK) patellar fixation. The null hypothesis was that the comparison between these three different patella fixation techniques would show no difference in the ultimate failure load and stiffness. Reconstruction of the MPFL with gracilis tendon autograft was performed in 12 pairs of fresh-frozen cadaveric knees (24 knees total; mean age, 63.6 $$\pm $$ 8.0 years). The specimens were randomly distributed into 3 groups of 8 specimens; SA reconstruction was completed with two 3.0-mm metal suture anchors; (SF) fixation was accomplished by two 6-mm bio-composite interference screws; SK fixation at the lateral side of the patella was accomplished after drilling two semi-patellar tunnels with a diameter of 4.5 mm. The reconstructions were subjected to cyclic loading for 10 cycles to 30 N and tested to failure at a constant displacement rate of 15 mm/min using a materials-testing machine (MTS 810 Universal Testing System). The final load of failure (N), stiffness (N / mm) and failure mode was recorded in each specimen and followed by statistical analysis. There was no significant difference in mean ultimate failure load among the three groups. The SK group failed at a mean ( $$\pm $$ SD) ultimate load of 253.5 $$\pm $$ 38.2 N, the SA group failed at 243 $$\pm $$ 41.9 N and the SF group at 263.2 $$\pm $$ 9.06 N. The SF group had a mean stiffness of 37.8 $$\pm $$ 5.7 N/mm. This was significantly higher (p

Hand-laid, 18 layered, E-Glass/Epoxy resin (GFRP) composite specimens were exposed to distilled water immersion at 65 °C (hydrothermal conditioning), a moist ambience with 95% relative humidity at 60 °C (hygrothermal conditioning) and sea water immersion (at room temperature) for different lengths of time. The treated samples were then exposed to both up and down thermal shocks. The specimens were also exposed to gamma irradiations pertaining to both high and low intensity gamma doses. Three-point Bend test of the samples so treated, was carried out in a universal testing machine and the failure modes as revealed from the SEM fractographs of the fractured specimens surfaces subjected to SEM analysis were recorded and analyzed. The samples conditioned differently for different lengths of time exhibited different extents of structural damages and adopted different modes for the ultimate failure. Any one or any combination of failure modes such as matrix-cracking, fibre pull-out, fibre–matrix de-bonding etc. indicating the interfacial failure were seen to be the chief mode of failure/disintegration of the GFRP composite specimens.

Background/purpose: The aim of the present in vitro study was to evaluate fatigue resistance of dental fixtures in three different types of fixture/abutment finishing line. Materials and methods: Transmucosal dental implants, with or without ferrulized neck, underwent fatigue tests (static and dynamic load) using the following standard protocol: UNI EN ISO 14801:2016. Two types of loading devices (screw- or cement-retained restoration) were also tested, and fatigue cycle tests were run to failure. Data of static and dynamic load tests were analyzed by proper statistical methods. Results: Following standard protocol for fatigue testing, the ILC type (Implant Level with ferrulized neck and cement-retained crown) showed a non-significant but higher Ultimate Failure Load (UFL = 445.7 N) compared to AL type (Abutment Level without ferrule effect, 421.6 N) and ILS type (Implant Level with ferrulized neck and Screw-retained crown, 362.8 N). No fracture of the titanium-base was registered in the tested specimens during the static loadings. Permanent deformations of the materials were observed. Conclusion: The number of cycles to either fracture or deformation (higher than 4 mm) occurring during fatigue tests showed that the stress rupture curve of the materials in group ILS appeared to be significantly different from those of the ILC and AL groups (p-values

In the presented work, sustainable High-Performance Lightweight Aggregate Concretes (HPLWACs) containing crushed clay bricks from the demolition and construction wastes as coarse lightweight aggregates (LWA) reinforced with the mono fiber, double, and triple fibers in many aspect ratios (l/d), and types have been created. Six prepared HPLWAC mixes were studied. Generally, the fibers’ inclusions in HPLWAC greate enhancing the ultimate failure and first crack impact resistance compared to plain specimens for hybrid and mono fiber specimens. Impact energy is increased at the failure related to concrete specimens, reinforced with the mono steel fiber was 1283%, 1042 %t, 984, and 892%. In contrast, the increment in single plastic reinforced specimens was 917%, 908%, 766, and 753% at 7, 28, 60, and 90, compared to the plain specimen. The concrete specimens that are reinforced via double hybrid fibers show an insignificant decrease in first crack impact resistance and overall failure compared to the mono steel fiber specimen. Triple hybrid fiber reinforced concrete specimens show the largest number of blows at the ultimate failure and first crack. Concrete specimens reinforced with mono steel and plastic fibers have decreased in drying shrinkage relative to plain concrete specimens. Double-hybrid concrete specimens reinforced have a slight improvement. In comparison, concrete specimens reinforced triple hybrid fiber show a reduction in drying shrinkage than plain concrete specimens.

Fibre reinforced plastics-FRP have become an excellent alternate to upgrade and restore improving failure infrastructures. The failure progress may be due to change in inappropriate design and improper construction practices. Glass Fibre-reinforced plastics (GFRP) wraps/laminates have proved to be a better option for use in infrastructure applications. This study has been made on square conventional columns and GFRP wrapped nano concrete columns under axial loads. The experimental investigation was to consist of the effect of varying the grade of concrete strength to 20 MPa & 30 MPa. In this research work is to evaluate the enhances, the effectiveness of using externally confined single and double layer GFRP wrapped nano concrete columns. Square RC columns of dimensions 150 mm × 150 mm and 750 mm length were cast and tested. One column specimen was of conventional concrete to provide as a reference, while all the remaining Nano concrete columns (NCC) were strengthened with GFRP laminates. The column specimens were provided with Glass Fibre Reinforced Plastics (GFRP) laminates with two different thicknesses. The parameters selected are stiffness, ultimate failure load, interpretation strength at ultimate state, and service load conditions. Further, the loads versus axial behavior were also determined. The associated failure modes and crack patterns for the experimental test column specimens were also examined. The experimental work showed a great improvement in the more strength for single and double layer GFRP wrapped nano concrete columns when compared with reference conventional concrete columns.

Concrete structures have been widely used for many years to resist impact loads. Steel–concrete composite structures may be considered efficient structures in the emerging modern construction field. Hence, the main objective of this research was to study the impact behavior of steel concrete composite slabs with different shear connectors and compare them with conventional slabs. Seven specimens of dimensions 500 × 500 × 50 mm were cast, which included plain cement concrete slabs, two reinforced cement concrete slabs with steel mesh and steel rebars as reinforcement, and four steel-concrete composite slabs with four different shear connectors: stud, tee, angle, and channel connectors. The composite action was achieved using a steel decking sheet welded with connectors on which the concrete layer was poured at the top. The test setup was fabricated with slots provided for specimens with simply supported end conditions and a mild steel drop weight. The specimens were impacted at the center of the span by dropping a steel mass from a free fall height of 1 m. The number of blows corresponding to the initial cracking and ultimate failure stages was recorded. The parameters that were used to compare the specimens were the impact energy absorbed, crack pattern, crack width, and increase in impact energy from the first blow to the last blow. The experimental results were very close to the analytical results obtained using ANSYS. The experimental and analytical results showed that the composite slabs with channel connectors performed better than the others, and it was proven that the composite slabs performed better under impact loading than conventional slabs.