High Axial Load Research Articles

Smearing in full complement roller bearings: Parameter study and damage analysis

This paper discusses the adhesive wear type “smearing” in small radial cylindrical roller bearings with combined axial and radial load. A reference test with high radial and axial static load leads to reproducible smearings. The impact of speed, starting oil temperature, axial and radial load as well as running-in is investigated with a seperate parameter variation. The measurement of the roller and roller set slip together with the damage analysis enables the distinction between roller-roller and roller-ring smearing.

Seismic behavior of an innovative equivalent monolithic precast shear wall under low and high axial load ratios

To meet the demands for the axial load and shear capacity of prefabricated reinforced concrete shear walls located at lower floors in high-rise buildings in high seismic intensity area, an innovative equivalent monolithic precast shear wall (labeled as EMPSW) was proposed by introducing X-shaped steel plate bracings and high ductility hidden column in this research. And seismic behavior of two EMPSWs under low and high axial load ratios (ALRs) were evaluated by quasi-static loading tests. The experimental phenomenon showed that EMPSWs under low and high ALRs presented similar fully developed and wide distributed cracks, whilst the ultimate draft ratios and ductility coefficients of specimens all met the specification requirements, exhibiting good lateral resistance through ductile damage for EMPSWs under different ALRs. Also, the increase of ALRs could improve the load carrying capacity and initial stiffness, but had no benefit on the energy dissipation and deformation capacity of EMPSW. Then, a reasonable strut-and-tie model (STM) was applied and verified to be well suitable for predicting the mechanical behavior of EMPSW. Besides, further investigations regarding the influence of critical parameters were implemented by finite element analysis (FEA). The FEA results illustrated that a higher ALR was beneficial for load-bearing capacity but had a significant negative impact on deformation capacity, thus the test ALR for EMPSW should be controlled within 0.5 in engineering practice. The volumetric ratio of X-shaped steel plate bracings and longitudinal reinforcement ratio in hidden column had a positive effect on capacity, but their contributions decreased as ALR increased.

A comparative study between glulam and concrete columns in view of design, economy and environment

In this paper, it is attempted to study possible sustainability solutions for building structures. In this context, comparisons are made between two load-bearing columns with different building materials – glued laminated timber and concrete – with regard to structural design, economic consequences and the emission of greenhouse gases. In terms of structural design, the results show that with small axial forces, glulam columns will result in smaller cross-sectional areas compared to concrete columns. However, at larger axial forces, concrete columns will result in smaller cross-sectional areas than glulam columns. An increased column length also means larger dimensions for glulam columns, but this does not always apply to concrete columns. With respect to environmental impact, it is shown that using glulam columns is the more environmentally friendly option. From an economic point of view, the cost estimates for glulam and concrete columns may vary depending on the country and the abundance of the construction material. In Sweden, a forest-rich country, it is shown that the costs for both column types are quite similar considering small axial loads. At higher axial loading, concrete is generally the cheaper alternative.

Experimental Investigation of Cage Dynamics and Ball-Cage Contact Forces in an Angular Contact Ball Bearing

The objectives of this investigation were to experimentally examine the cage motion and ball-cage contact forces for an angular contact ball bearing (ACBB) operating under various load and speed combinations. In order to achieve the objectives, a Counter Rotating Angular Contact Ball Bearing Test Rig (CRACTR) was designed and developed such that both the races of an ACBB can be rotated simultaneously in opposite directions, providing valuable insights into the ball-cage interaction. Five proximity probes were used concurrently to measure the in-plane (radial) and out-of-plane (axial) motion for three commercially available cage designs. Two load cells were used to measure the contact forces between the balls and cage pocket. The experimental results demonstrate that high inner race speeds and high axial loads develop the smallest and most circular cage whirl motions. Additionally, cage radius, cage pocket clearance, cage pocket area and cage inertia were the prominent factors affecting the magnitude of cage whirl. Experimental results also indicate that contact forces between the ball and cage pocket increase linearly with the increased race speeds. Ball-cage contact force was shown to be different for the three cages and was primarily governed by the cage pocket area and the cage radius. Results from this investigation can be utilized to predict the correlation between the ball-cage contact forces and the race speeds, and identify the key parameters governing the stable cage motion during bearing operation.

Behavior of light-gauge steel short columns filled with normal and lightweight aggregate concrete under concentric axial loading

This study aims to investigate experimentally and numerically the behavior of light-gauge steel tubes filled with normal and lightweight concrete under axial loading. A total of thirty-five specimens, including thirty-two composite columns, two bare steel columns, and one normal-weight plain concrete column, were considered. The main variables in the tests were the concrete infill type (normal-weight and lightweight), the column's length (1, 1.25, 1.5, 1.75-m), the steel tube thickness (2 and 2.4-mm), and the cross-section (100×100 and 150×150-mm). In addition, theoretical capacities were computed according to Eurocode 4, and a finite element analysis was conducted using ABAQUS software. The results showed that the behavior of lightweight filled steel tubes was similar to the normal weight filled tubes during the test; however, their capacities were lower compared to the normal weight filled tubes by a range of (1%-20%). Yet, lightweight filled steel tubes can achieve high axial loads. In addition, the axial capacity of all composite columns decreased with the increase of the column's height and increased with the increase of both the cross-section and the steel thickness. Current code specifications of EC4 and the numerical results obtained from ABAQUS overestimated the capacities of the composite concrete-filled tubes by 3% and 14%, respectively; however, the EC4 was found to present close estimations to the experimental results.

NUMERICAL ANALYSIS FOR COMPRESSED CERAMIC HOLLOW BRICK MASONRY COLUMNS STRENGTHENED WITH GFRP MESHES

This article presents the analysis of obtained experimental results for the study of masonry columns which have been strengthened by GFRP confinement after high-level axial compression loading. Ceramic hollow-brick middle-scale models were investigated regarding assumed testing program. The basics of experimental studies were briefly described in the paper. Theoretical study was performed to compare experimental and theoretical values. Such numerical analysis helps to evaluate the possibility to use the existing standard`s approaches for calculating bearing capacity of strengthened by GFRP jacketing ceramic brick columns which were subjected to the high axial loading. Theoretical results areratheraligned with experimental data. Some conclusions were provided in terms of usability the analytical model provided standards and other scientists. Addressing to the further investigation and research problems were performed.

Seismic behavior of square spiral-confined high-strength concrete-filled steel tube columns under high axial load ratio

Adding internal spiral reinforcement is an effective and practical approach to enhancing the ductility of square concrete-filled steel tube (CFST) columns with high-strength concrete (HSC). To investigate the seismic behavior of CFST and spiral-confined concrete-filled steel tube (SCCFST) columns with HSC under high axial load ratio, four CFST columns and four SCCFST columns with concrete strengths not less than 110 MPa were tested under combined axial and lateral loading. The test variables included the concrete compressive strength, the axial load ratio, and the lateral-loading protocol. The test results demonstrated that adding spiral reinforcement can offset the reduction of ductility caused by the increase of the axial load ratio. The ultimate drift ratios of the columns under an axial load ratio of 0.5 increased from approximately 2.0% to 3.5% after adding spiral reinforcement with a volumetric ratio of 3.13%. Increasing the concrete strength from 110 to 140 MPa essentially did not affect the deformation capacity of the columns. Due to the cyclic degradation effect, the deformation capacity of the specimen under cyclic loading was much smaller than that of the corresponding specimen under monotonic loading. The column axial shortening accumulated during cyclic lateral loading and increased exponentially when significant strength degradation started. The rotation at the column base contributed a significant portion to the total lateral displacement, indicating the necessity of considering the flexibility of the column base in structural analysis.

Experimental study on hysteretic behavior for corroded circular RC columns retrofitted by ICCP-SS

An experimental study on nine circular reinforced concrete (RC) columns is presented in this paper, wherein one column specimen was adopted as the reference group, the other eight specimens were subjected to accelerated corrosion. After the accelerated corrosion for 180 days, two of the corroded columns were protected by impressed current cathodic protection (ICCP), while the other six corroded columns were further repaired by structural strengthening (SS). A combination of ICCP and SS, namely ICCP-SS, is adopted in this study, which adopts the carbon-fabric reinforced cementitious matrix (C-FRCM) as anode and strengthening material. Finally, specimens were cyclically loaded in a horizontal direction under different axial loads. The results indicated load-carrying and energy dissipation capacities of specimens were deteriorated due to corrosion. This phenomenon is severer under higher axial load. The dual function of ICCP-SS technique does not only improve load-carrying and energy dissipation capacities of RC columns, but also reduce the on-going corrosion of steel re-bars. These benefits can be attributed to the confinement effect to the column base provided by the C-FRCM composites and the ICCP effect using carbon fabric mesh in the C-FRCM composites as anode.

Hybrid screw fixation for femoral neck fractures: Does it prevent mechanical failure?

IntroductionTraditionally, femoral neck fracture fixation has been performed using three partially threaded cancellous screws. However, fracture collapse with femoral neck shortening, and varus deformation frequently occurs due to posterior medial comminution and lack of calcar support. We hypothesize replacing the inferior neck/calcar screw with a fully threaded, length stable, screw will provide improved biomechanical stability, decrease femoral neck shortening and varus collapse. MethodsTen matched cadaveric pairs (20 femurs) were randomly assigned to two screw fixation groups. Group 1 (Hybrid) utilized one fully threaded calcar screw & two partially threaded superior screws. Group 2 (PT) utilized all partially threaded screws. Specimens underwent standardized femoral neck osteotomies, 45° from the horizontal, with 5 mm posteromedial wedge removed to simulate posteromedial comminution. Screws were placed using fluoroscopic guidance. Specimens were biomechanically tested using two loading sequences: 1) Axial load applied up to 700 N, followed by cyclic loading at 2 Hz with loads of 700 to 1,400 N for 10,000 cycles. 2) All surviving constructs were cyclically loaded to failure in stepwise incremental manner with max load of 4,000 N. Paired t-tests used to compare stiffness, cycles to failure, and max load to failure (defined as 15 mm load actuator displacement). ResultsConstruct stiffness was 2848 ± 344 N/mm in PT vs. 2767 ± 665 for Hybrid (P = 0.628). Load to failure demonstrated, hybrid superiority with max cycles to failure (3797 ± 400 cycles) vs. (2981 ± 856 cycles in PT) (p = 0.010), and max load prior to failure (3290 ± 196 N) vs. (2891 ± 421 N in PT) (p = 0.010). No significant difference in bone mineral density was noted in any of the specimens. ConclusionsOur study is the first to assess the biomechanical effects of hybrid fixation for femoral neck fractures. Hybrid screw configuration resulted in significantly stronger constructs, with higher axial load and increased cycles prior to failure. The advantageous mechanical properties demonstrated using a fully threaded inferior calcar screw provides a length stable construct which may prevent the common complication of excessive femoral neck shortening, varus collapse and poor functional outcome.

Seismic performance of a novel partial precast RC shear wall with reserved cast-in-place base and wall edges

Precast reinforced concrete (RC) shear walls have attracted significant research efforts due to advantages over the conventional construction methods such as better quality control, shorter construction time and less environmental impact. Research efforts have been dedicated to exploring alternative methods for the connections of precast shear walls. In this paper, a novel partial precast shear wall is proposed, which is made of a precast shear wall with double-legs at the base, and reserved cast-in-place base zone and wall edges. To begin, the design concept of the proposed precast shear wall is described. A comprehensive experiment program is then presented, in which two groups of identical full-scale shear walls were designed, constructed and tested in a cyclic pseudo-static manner in order to investigate the seismic performance of the proposed wall. Each group consisted of three specimens, one cast-in-place and two proposed walls. These two groups of specimens were tested under a high axial load index of 0.3 and 0.4, respectively. The test results indicate that the failure modes of the proposed partial precast walls were similar with those constructed with cast-in-place method. For both axial load indices, the precast walls had comparable seismic performance with the cast-in-place walls in terms of lateral load capacity, stiffness degradation, steel strain behavior, energy dissipation, and residual displacement but better deformability and ductility. In addition, higher axial load indices resulted in decrease in ductility and increase in residual displacements. Moreover, the same precast walls in the same group had similar performance, providing confidence in the repeatability of the test results and stable performance of the proposed walls. It can come to the conclusion that the proposed partial precast shear walls can have comparable and stable seismic performance with the conventional cast-in-place method and hence can be taken as an alternative in practice.

Cyclic Behavior of High-Strength Fiber-Reinforced Concrete Columns under High Axial Loading Level

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A built-up type horizontally corrugated steel plate shear wall with a special shape

A built-up type specially shaped corrugated steel shear wall (BS-CSSW) that can be concealed within enclosure walls was proposed for applications in residential buildings. Quasi-static tests were performed on two specially shaped corrugated steel shear wall specimens (S-CSSW and BS-CSSW) and refined finite element simulations were conducted. With the verified modeling method, a parametric study was performed on BS-CSSWs with different wall configurations and interior column positions. The results indicated that the corrugated shear plates in the S-CSSW underwent premature elastic buckling, thus leading to a sudden drop in strength upon buckling and low strength levels after buckling. Shear panels in the BS-CSSW successfully entered the shear yielding mode and remained in a stable in-plane shearing state until reaching 2% drift. The BS-CSSW had higher elastic and plastic strength levels, better ductility, slower stiffness reduction, lower out-of-plane plate deformation and a wider hysteretic relationship than those of the S-CSSW. The position of the interior columns primarily influenced the slenderness of the side and interior corrugated panels and affected the strength development modes. The BS-CSSWs had separate bearing modes between lateral loads and axial loads and could withstand high axial load conditions with little influence on shear strengths.

Seismic behavior of high-strength concrete-filled square steel tube columns reinforced with ultrahigh-strength reinforcing bars

This paper investigated the seismic behavior of high-strength concrete-filled square steel tube columns reinforced with ultrahigh-strength reinforcing bars. Three full-scale specimens with different amounts of ultrahigh-strength longitudinal reinforcing bars under a high axial load ratio and cyclic lateral load were tested. The test results demonstrate that the existence of ultrahigh-strength longitudinal reinforcing bars had a significant influence on the seismic behavior of high-strength concrete-filled steel tube columns. Compared with conventional concrete-filled steel tube (CFT) columns, the deformation capacity, bearing capacity and cumulative energy dissipation of these innovative CFT columns are greatly improved, and the cumulative damage and plastic deformation of the specimens decreased with the introduction of steel bars. A calculation model based on AISC360-16 using the superposition method was proposed and verified to evaluate the compressive-flexural strength of the specimen.

Seismic performance of steel-reinforced concrete composite columns in existing and modern construction

The seismic performance of steel-reinforced-concrete (SRC) composite columns with non-seismic details in older buildings is not sufficiently characterized due to lack of cyclic test data. Formal recommendations for cyclic backbone curves of these columns for performance-based seismic assessment are not currently available. In addition, the effect of axial loads on the deformation capacity of SRC columns is uncertain. Furthermore, SRC composite columns with modern seismic details lack formal recommendations for nonlinear modeling parameters or acceptance criteria. This study aims to fill some of these knowledge gaps via experimental and analytical means. The cyclic behavior of five SRC composite columns with non-seismic and seismic details failing in flexural-tension or flexural-compression modes has been experimentally investigated. Test results show that tension-controlled SRC columns with non-seismic details can sustain up to 6% drift ratio with minor strength degradation, satisfying modern seismic assessment criteria and suggesting no need to be retrofitted. However, high axial loads were found to jeopardize drift capacity of compression-controlled SRC columns with non-seismic details (2% peak-load drift capacity), leading to premature axial failure. Test results suggest the possibility of relaxing the ACI 318–19 confinement requirements for tension-controlled SRC columns with seismic details. A database of past cyclic tests of SRC composite columns with seismic and non-seismic details has been developed. Database response parameter trends have been analyzed and compared. Based on the current test results and the database trends, new drift and ductility capacity expressions for SRC columns with non-seismic details in older buildings are proposed. Furthermore, based on current test results and the database trends, new ASCE 41-17-style lower bound nonlinear modeling parameters for flexural-controlled SRC composite columns with non-seismic details are proposed for performance-based seismic assessment.

Acetabular Fractures with Central Hip Dislocation: A Retrospective Consecutive 50 Case Series Study Based on AO/OTA 2018 Classification in Midterm Follow-Up.

Introduction Management of acetabular fractures is challenging, especially when a medial acetabular fracture is complicated by central hip dislocation. We retrospectively investigated the clinical outcome and risk factors of secondary hip osteoarthritis requiring total hip arthroplasty after the surgical treatment of acetabular fractures with central hip dislocation. Materials and Methods The medical records of all patients who had acetabular medial wall fractures with central hip dislocation treated with open reduction and internal fixation by a single surgeon between January 2015 and June 2017 were reviewed. Surgical reduction was performed with the modified Stoppa with/without the Kocher-Langenbeck (KL) approach. Patients were followed for a minimum of three years, and the Majeed scoring system was used for functional evaluation. Multivariate logistic regression analysis was used to assess the association of patients' characteristics with the likelihood of advanced posttraumatic arthritis developing with conversion to total hip arthroplasty. Results Fifty patients were included in this study, with disease classified as AO/OTA 2018 62B/62C. Thirty-five patients (70%) had good or excellent Majeed pelvic scores. Eleven patients (22%) eventually received total hip arthroplasty because of end-stage posttraumatic arthritis. Three risk factors identified for total hip arthroplasty were male sex, initial marginal impaction, and sciatic nerve injury. Kaplan-Meier survivorship analysis estimated that the cumulative probability of free-from-end-stage arthritis was 78% (95% confidence interval, 73%–90%) at the 5-year follow-up. Conclusion Surgical fixation with the modified Stoppa and the KL approach for acetabular medial wall fractures with central hip dislocation is an effective approach with a satisfactory functional outcome. A prodromal factor was marginal impaction concomitant with articular damage. The trauma of high axial loading and the occupational distribution (males performing heavy manual labor and heavy lifting) with preoperative sciatic nerve injury increased the odds of developing end-stage arthritis.

Behaviour of rectangular concrete filled tubular flange girders under combined loading

AbstractSteel‐concrete composite construction can provide an efficient structural solution by utilizing the two component materials to create a single effective composite section. The high tensile strength and ductility of steel combined with the excellent compressive strength and robustness of concrete results in an effective composite cross‐section which can be used in a wide variety of applications. There are a number of different shapes of composite beam, and this paper is focussed on a relatively new structural solution called concrete filled tubular flange girders (CFTFGs). These comprise a steel beam in which the top flange plate is replaced with a concrete‐filled hollow section. The compression flange can be any shape (e.g. circular, rectangular, and pentagonal) and the focus in the current paper is on simply supported girders with a rectangular section for the compression flange (i.e. RCFTFGs). These members have very high lateral torsional buckling resistance compared with conventional steel I‐girders of similar depth, width and steel weight and are therefore capable of carrying very heavy loads over long spans. However, they are complex to analyse and their behaviour is governed by several inter‐related parameters which are investigated and discussed herein. Given the most common applications of these girders, such as in bridges and carparks for example, they are frequently exposed to a simultaneous combination of high axial loads and bending moments. Although current design codes offer rules for the design of composite columns under combined loading, the design of RCFTFGs, which are asymmetric in nature under the combined effects of tension and bending, are not explicitly included. This work aims to investigate the ultimate strength of RCFTFGs with stiffened webs under the combined effects of various levels of axial tension and positive (sagging) bending moment. Nonlinear three‐dimensional finite element analyses using the ABAQUS computer software package have been developed to facilitate the study. The model is validated using available experimental data and then employed to conduct an extensive parametric study. It is shown that the moment capacity of RCFTFGs is reduced in most situations under the presence of an axial tensile force in the steel beam. In addition, the tensile capacity of the RCFTFGs is limited by the axial capacity of the steel beam alone, with little contribution from the concrete infill. Several influential parameters are examined and conclusions are discussed. Based on the finite element analysis, the moment–axial force interaction relationship is presented and discussed.

SEISMIC PERFORMANCE OF GFRP-RC RECTANGULAR COLUMNS: NUMERICAL STUDY

Composite materials like glass fiber-reinforced polymer (GFRP) is becoming widely acceptable to be used as a reinforcing material due to its high ultimate tensile strength-to-weight ratio and excellent resistance to corrosion. However, the seismic behavior of GFRP-reinforced concrete columns has not been fully investigated yet. This paper presents the results of a numerical analysis of full-size GFRP-RC rectangular columns under cyclic loading. The simulated column depicts the lower part of a building column between the foundation and the point of contra-flexure at the mid-height of the column. GFRP reinforcement properties and concrete modeling based on fracture energy have been incorporated in the numerical model. Experimental validation has been used to examine the accuracy of the constructed finite element models (FEMs) using a commercially available software. The validated FEM was used to perform a parametric study, considering several concrete strength values and axial load levels, to study its influence on the performance of the GFRP-reinforced concrete columns under cyclic loading. It was concluded that the hysteretic dissipation capacity deteriorates under high axial load level due to severe softening of the concrete. The FE results showed a substantial improvement of the lateral load-carrying capacities by increasing concrete compressive strength.

Effect of Axial Load-Dependent Deformation Rate on the Grain Size Distribution and Mechanical Properties of Friction Stir Processed Copper

Abstract During friction stir processing (FSP), the combination of rotation and movement of the tool leads to frictional heat generation and plastic deformation at the tool-material contact surface, leading to a microstructurally refined formation region. The deformation rate in the material can be altered by varying the axial load by increasing or decreasing the tool’s plunging depth. In the present study, FSP was carried out on a pure copper plate of 3-mm thickness by varying the plunge depth from 2.3 to 2.6 mm for a tool pin length of 2.4 mm. The microstructure of the processed samples was studied by optical microscopy, and the grain size was measured by the linear intercept method. Tensile testing was carried out perpendicular to the processing direction. The grain size distribution was narrower at low axial loads and wider at the higher axial loads, measured between 1 and 120 µm. At higher axial loads, microstructure consisted of bands indicative of the heterogeneity in the deformation. The formation of bands at higher axial loads leads to improved mechanical properties. The ductility of the processed materials at higher axial loads was 16%, which was four times the increase observed at lower axial loads (4%). The formation of a bi-modal microstructure (alternating layers of fine and coarse grains) at high axial load enhanced the processed materials’ strength and ductility.

Study on management of extra articular distal tibial metaphyseal fractures by intramedullary interlocking nailing

<p><strong>Background:</strong> Fractures of the tibia remain a controversial subject despite advances in both non-operative and operative care. The goal in expert care is to realign the fracture, realign limb length, and early functional recovery. To analyze the short-term results of intramedullary interlocking nailing in the management of extra-articular distal tibial metaphyseal fractures done.</p><p><strong>Methods</strong>: This is a prospective comparative on-randomized study of 28 patients with distal tibial metaphyseal fractures in govt. dist. headquarters hospital Nagapattinam with a follow-up ranging from September 2018 to january 2019 4 months. Injury With more than 3 weeks, nonunion, and patient with multiple injuries or a history of previous knee or ankle pathology were not included as were patients who sustained high energy axial load injury-causing disruption or impaction of the ankle plafond.</p><p><strong>Results: </strong>The average distance between the distal tip of the nail and the articular surface of the plafond was 12 mm (range, 4 to 15 mm). Fibular plating was done in 10 patients. Two distal locking bolts were used in 26 patients; 2 patients had three distal locking bolts.</p><p><strong>Conclusions:</strong> Intramedullary nailing is a safe and effective technique for the treatment of extra-articular distal metaphyseal tibial fractures if careful preoperative planning is allied with the meticulous surgical technique.</p>

Seismic performance of full-scale UHPC-jacket-strengthened RC columns under high axial loads

Ultra-high-performance concrete (UHPC) is a class of concrete materials that have high strength and ductility capacities. This study developed two UHPC jacketing methods to improve the seismic performance of shear-deficient RC columns in mid- to high-rise buildings without enlarging the cross-section of the columns. In the first method, the original concrete cover was replaced with a cast-in-place UHPC jacket that was reinforced by steel bar mesh. To simplify the on-site construction process, the second method utilized prefabricated UHPC panels incorporating steel bar mesh. The performance of the proposed strengthening methods was evaluated using cyclic loading tests on three full-scale RC columns with a high axial load demand. The test results showed that the developed UHPC jacketing methods improved the lateral strength and drift capacity of the shear-deficient column by at least 40% and 30%, respectively. They also reduced the residual displacement of the column by 65%-80%. Compared to the cast-in-place jacketing, the discontinuity in the prefabricated UHPC jackets inhibited full composite action of the jacketing, thus reducing the retrofitting efficiency. In addition to the experimental study, evaluation methods were proposed to evaluate the strength and behavior of the retrofitted columns.