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Circular hoops, rectilinear hoops with crossties, and spirals are widely used in reinforced concrete columns as transverse reinforcement to prevent shear failure and provide confinement. Besides transverse reinforcement, many researchers have used square or circular steel tubes to provide confinement to concrete. This paper compares experimentally the application of circular steel tubes and spirals in providing confinement to concrete. Five types of compressive test specimens were tested under axial compression, comprising one type of column confined by rectilinear hoops, one type of column confined by a circular steel tube, two types of columns confined by a combination of circular steel tube and rectilinear hoops, and one type of column confined by a combination of spirals and rectilinear hoops. The result showed that circular steel tubes confined the concrete core well and provided additional axial support. The compressive test specimens using circular steel tubes had 40.74% higher axial load-carrying capacity, exhibited more ductile behavior, and had less damage than compressive test specimens using spirals. It proved that circular steel tubes were more effective in providing confinement to concrete than spirals. Rectilinear hoops with a spacing of one-fourth and one-half of the column cross-section increased the maximum axial load by 57.78% and 20.89%, respectively. The effect of the arching action on the concrete between the rectilinear hoops and the circular steel tubes could be neglected so that there was no ineffectively confined area, and the outer concrete was assumed to be fully effectively confined by the rectilinear hoops. [ABSTRACT FROM AUTHOR]

This paper primarily presents an investigation into rectangular hollow section (RHS) cross- (or X-) connections with the branches fully laterally offset and loaded in axial tension. A set of 10 full-scale experimental specimens, carefully fabricated with noncritical welds, are tested in the laboratory, and the results are used to validate nonlinear finite-element models. To enhance the range of available data, the calibrated models are varied in an expanded parametric numerical study. A chord failure limit-state model based on a yield-line mechanism, which was identified in prior research on branch compression loading, is verified herein for branch tension loading. Furthermore, the limit state of branch failure is investigated by means of the combined experimental and numerical database produced. Design recommendations for laterally offset cross-connections loaded under branch tension, based on chord and branch failure modes, are presented. The application of current design recommendations for traditional cross-connections (with centered branches) to connections with full-width branches and laterally offset branches is also evaluated. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) concrete printing is increasingly becoming popular because it provides a powerful platform for the fabrication of structural components in freeform architectural shapes. Although manufacturing technology and material property improvement are advancing rapidly, the development of methods to predict the structural capacity of printed elements is lagging. This paper presents an experimental and numerical investigation to predict the axial load capacity of a printed concrete wall module. The module geometry contains two parallel thin wall sections connected by an internal sine wave. The thin wall section reduces the concrete consumption, and the internal sine wave provides lateral stability during printing and in the hardened state. It is a popular pattern printed by many researchers and in some real constructions. Two wall module specimens with the prescribed geometry were 3D-printed and tested under compression. The maximum loads of 2,890 and 2,924 kN were obtained for the first and second wall specimens, respectively. Additionally, samples were taken from different locations of a printed prototype to identify printed material characteristics. These experimental characteristics were then introduced to a finite-element numerical model for predicting the structural performance of the printed wall module under compression load. The results showed that the experimental maximum load and stiffness have 1% and 5% differences with numerical outputs, respectively. Based on such a validated model, the failure modes are discussed, and an analytical method is proposed for predicting the axial capacity for the prescribed geometry. [ABSTRACT FROM AUTHOR]

Premature shear failure in reinforced concrete (RC) beam–column joints (BCJs) or at the top of columns can significantly compromise a building's seismic response, leading to major damage or global collapse, as observed in the aftermath of recent seismic events. Local strengthening solutions based on the employment of fiber-reinforced polymers (FRPs) are effective at increasing shear strength and preventing the failure of BCJs, and are also quick and easy to apply. This has led to their increased use in recent postearthquake reconstruction processes. However, large-scale plans to mitigate seismic risk require strengthening solutions that produce a minimum level of disruption and do not prevent the use of buildings. This can be achieved only by conducting work from a structure's exterior. This paper, therefore, proposes a novel FRP strengthening layout for exterior RC BCJs that combines the use of quadriaxial fabric and mechanical FRP spike anchors. In order to validate the proposed solution and quantify the effects of the number of layers and anchors, four full-scale BCJs are tested under a constant axial load and reversed cyclic displacement. The results are presented and discussed in relation to: global subassembly and local joint-panel response, energy dissipation, and the strain demand on the FRP fibers. A comparison with current available design formulations for anchored-FRP fabrics is made to produce preliminary design criteria. [ABSTRACT FROM AUTHOR]

In recent years, square hollow section (SHS) joints with concrete-filled square hollow section (CFSHS) chords have increasingly been used in truss bridges where the fatigue life reliability is a critical issue. In this paper, a finite element analysis was performed to investigate the SCFs in SHS-CFSHS T-joints under in-plane bending in the brace, axial force in the chord and in-plane bending in the chord. The finite element models were developed and validated with experimental results. Then a parametric study was conducted with a reasonable range of three key non-dimensional parameters, i.e., β (width ratio between brace and chord), 2γ (width–to–wall thickness ratio of the chord) and τ (wall thickness ratio between brace and chord). Consequently, the stress concentration factor formulae for the fatigue design of SHS-CFSHS T-joints were proposed through multiple regression analysis. For in-plane bending in the brace, the maximum stress concentration factors were found at lines B and C for thick-walled chords (2γ = 25.0), while the stress concentration factors at all the lines need to be checked for thin-walled chords (2γ < 16.0). Under axial force in the chord and in-plane bending in the chord, only stress concentration factors at lines C and D needed to be considered. A comparison of stress concentration factors between SHS-SHS and SHS-CFSHS joints showed reductions of 10~26% and 14~31% in stress concentration factors in SHS-CFSHS joints under axial force in the brace and in-plane bending in the brace, respectively. In addition, it showed a general increase in stress concentration factors in SHS-CFSHS joints under axial force and in-plane bending in the chord. This reduction is attributed to the reduction in chord face deformation benefiting from the in-filled concrete. Meanwhile, the stress concentration factors caused by loads in the chord are much lower than those caused by loads in the brace. This work complements earlier studies on SHS-CFSHS T-joints under axial force. [ABSTRACT FROM AUTHOR]

Balanced fiber-reinforced rubber (FRR) pipes not only provide displacement compensation when transporting pressurized media but also prevent additional forces and displacements from being exerted on the connected pipeline system. Investigating the balanced performance of FRR pipes and the axial stiffness of balanced pipes is crucial for optimizing pipeline design and improving the reliability of pipeline systems. This paper develops a numerical model of FRR pipes that considers the nonlinearity of the rubber material and the interaction between the rubber matrix and fiber-reinforced layers. Using this model, the balanced performance of the pipe is calculated, and its axial stiffness under combined internal pressure and axial load is analyzed. Numerical results are compared with experimental data for validation. The results indicate that the pipe's balance is achieved through the combined effects of the elongation and rotation of the reinforcing fibers and the deformation of the rubber matrix, highlighting the significant impact of the rubber matrix on the mechanical performance of the FRR pipe. Furthermore, the pipe's balanced performance and axial stiffness are highly sensitive to the winding angle of reinforcing fibers. The proposed numerical model fills the gap in using numerical methods to evaluate the balanced performance of FRR pipes and provides valuable insights for their design and optimization. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study focused on evaluating the strain generated within short concrete columns reinforced with glass-fiber-reinforced polymer (GFRP) bars and spirals under concentric compressive axial loads. This research was motivated by the lack of sufficient data in the literature regarding strain in such columns. Five full-scale RC columns were cast and tested, comprising four strengthened with GFRP reinforcement and one reference column reinforced with steel bars and spirals. This study thoroughly examined the influence of various test parameters, such as the reinforcement type, longitudinal reinforcement ratio, and spacing of spiral reinforcement, on the strain in concrete, GFRP bars, and spirals. The experimental results showed that GFRP–RC columns exhibited similar strain behavior to steel–RC columns up to 85% of their peak loads. The study also highlighted that the bearing capacity of the columns increased by up to 25% with optimized reinforcement ratios and spiral spacing, while the failure mode transitioned from a ductile to a more brittle nature as the reinforcement ratio increased. Additionally, it is preferable to limit the compressive strain in GFRP bars to less than 20% of their ultimate tensile strain and the strain in GFRP spirals to less than 12% of their ultimate strain to ensure the safe and reliable use of these materials in RC columns. This research also considers the prediction of the axial load capacities using established design standards permitting the use of FRP bars in compressive members, namely ACI 440.11-22, CSA-S806-12, and JSCE-97, and underscores their limitations in accurately predicting GFRP–RC columns' failure capacities. This study proposes an equation to enhance the prediction accuracy for GFRP–RC columns, considering the contributions of concrete, spiral confinement, and the axial stiffness of longitudinal GFRP bars. This equation addresses the shortcomings of existing design standards and provides a more accurate assessment of the axial load capacities for GFRP–RC columns. The proposed equation outperformed numerous other equations suggested by various researchers when employed to estimate the strength of 42 columns gathered from the literature. [ABSTRACT FROM AUTHOR]

In this paper, a novel T-shaped steel–concrete composite shear wall (TSCCW) is proposed. Low-cycle reciprocating tests were carried out on the TSCCW to investigate its performance in terms of its damage characteristics, hysteretic properties, energy dissipation capacity, stiffness degradation and ductility. A numerical model was established on the basis of the tests, and the correctness of the numerical model was verified. Afterwards, parameters such as shear span ratio, axial load ratio, rebar diameter, steel thickness, concrete strength grade and axial compression position were analyzed. The results show that the shear span ratio has a great influence on the performance of the TSCCW. A reduction in the shear span ratio from 2.1 to 1 reduces its stiffness by 333%. An increase in the axial load ratio will increase the load carrying capacity and stiffness of the TSCCW, and the deformation capacity will first increase and then decrease; it is recommended that the axial load ratio should be taken as 0.4. Increasing the steel thickness will improve the load carrying capacity, stiffness, deformation capacity and energy dissipation capacity of the TSCCW to a certain extent. Increasing the reinforcement diameter has less effect on the seismic performance of the TSCCW. [ABSTRACT FROM AUTHOR]

Soft hang-off is an emergency operation for drilling risers to survive under harsh environments. Buckling of the suspended riser and overstroke of the tensioner piston rod would probably occur. Conventional analysis methods usually ignored the dynamic interaction of the riser and tension fluctuation. This paper is devoted to developing an improved coupled model for the axial dynamic analysis of the riser under soft hang-off mode. In the developed model, the mathematical model of the tensioner was established considering gas state variations, internal friction and pressure loss, the mechanical model of the riser considering axial hydrodynamic load was developed, and the two models were coupled through the kinematic variables. A case study is carried out to analyse the axial dynamic characteristics of the riser under soft hang-off mode, and the comparison showed that the conventional tensioner models will underestimate the axial dynamic response of the riser in soft hang-off mode. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of the seismic behavior of concrete columns reinforced with glass fiber-reinforced polymer (GFRP) bars. Seven full-scale square columns were tested under sustained compressive axial loading combined with monotonic or cyclic lateral loading. The test program included two types of reinforcement (GFRP and steel bars) and different axial load levels (0, 20, and 33% of the axial capacity). The experiments showed that GFRP reinforcement could be used in concrete columns subjected to lateral loads, provided that ties are capable of properly confining the concrete core up to failure, thereby contributing to improving their deformation and energy dissipation capacity. Tests also confirmed the influence of the axial load level on the loadbearing capacity, deformation, and energy dissipation capacity of GFRP-reinforced concrete columns. [ABSTRACT FROM AUTHOR]

The nonlinear buckling and postbuckling of functionally graded carbon nanotube reinforcement composite (FG-CNTRC) plates resting on the nonlinear effect of elastic foundation under combined load including external pressure and axial compression loads with uniformly distributed temperature rises are fully investigated in this paper. The FG-CNTRC plates are reinforced by FG-CNTRC stiffeners and the plate-foundation interaction is modeled using a nonlinear model. The higher-order shear deformation plate theory with the geometrical nonlinearities of von Kármán is applied to establish the basic formulations. Additionally, by using the anisotropic higher-order shear deformation beam theory, a new smeared stiffener technique is successfully developed for FG-CNTRC stiffeners. Galerkin's method is used to achieve the equilibrium equation system in the nonlinear algebraic forms, and the critical load and postbuckling load–deflection curve expression are explicitly determined. The numerical investigations discuss the influences of FG-CNTRC stiffeners, hardening/softening nonlinear elastic foundation, uniformly distributed temperature rises, geometrical and material features on nonlinear stability of stiffened FG-CNTRC plates. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tubular (CFST) columns have been widely used in multi-story and high-rise frame structures. During the service period, they may suffer vehicle impact due to traffic accidents or terrorist attacks. This paper numerically evaluates the performance of CFST columns under vehicle impact and investigates the effects of carbon FRP (CFRP) wrapping arrangements on performance improvement of the columns. Before that, a numerical model was developed to simulate the responses of CFST columns without and with FRP wrapping under vehicle impact and post-impact axial compression, and then calibrated by reported tests. Evaluation results show that the performance of CSFT columns under vehicle impact is divided into five levels, i.e., no repair required, rapid repair required, minor repair needed, major repair needed, and replacement needed. The performance level decreases with the increase in the vehicle weight or speed and increases with the increase in the column diameter or steel tube thickness. The column height has little effects on the performance level. A higher axial load ratio, e.g., 0.5, might reduce the performance level. Besides, a CFST column tends to fail in flexure mode when hit by F800 medium truck, while it may fail in flexure & shear mode when hit by C2500 pickup truck. Investigation results indicate that FRP wrapping with each layer orientation of 90° (i.e., in the longitudinal direction) and 0° (i.e., in the hoop direction) present the best performance improvement for a CFST column possibly undergoing flexure & shear and flexure failure, respectively. The increase of the number of FRP layers effectively improves the performance levels of CFST columns but the excessive demand may be not economical. It is not necessary to employ an FRP wrapping range of 100% for improving the vehicular impact performance level of a CFST column to the expected one. [ABSTRACT FROM AUTHOR]

Channel steel-reinforced brick column technology has gained significant popularity in rural China due to its convenience and cost effectiveness. However, current research on channel steel reinforcement is sparse, and engineering applications often rely solely on construction experience. This reliance leads to significant construction errors, inconsistent reinforcement effects, and, in some cases, tragedies such as the collapse of Changsha's "4.29" self-built houses. Therefore, in this paper, experimental and simulation studies on brick columns reinforced with external channel steel were conducted, and the results show that channel steel reinforcement can significantly enhance the axial load capacity of brick columns. However, increased initial stress levels and height-to-thickness ratios substantially reduce the reinforcement effect. Under axial pressure, the outer channel steel fails mainly through bending and buckling instability. Still, due to its good ductility, its failure occurs later than the brick column after being restrained by sufficient wall screws. Based on the experimental and simulation results, a method for calculating the axial compressive bearing capacity of the reinforced column is proposed, providing theoretical support and engineering guidance for applying this reinforcement method. [ABSTRACT FROM AUTHOR]

In this paper, a numerical modeling was developed to study (on the basis of the Paris law) the fatigue propagation paths of eccentric external (outer) cracks in circumferentially cracked round bars (CCRB) subjected to a cyclic type of loading in the form of either remote tensile loading or imposed axial displacement. Results show how the eccentricity (in relation to the wire axis) of the circular resistant ligament increases with the growth of outer circumferential cracks by subcritical fatigue mechanisms. This phenomenon is more pronounced when the solicitation consists of a remote tensile loading than when it is an axial displacement, when the initial eccentricity of the ligament increases (for a given initial diameter), and when the Paris exponent characteristic of the material rises. The paper also analyzes in depth the different situations regarding contact between crack faces during subcritical cyclic fatigue propagation, covering a wide range of cases including no contact, partial contact, and full contact depending on the ligament diameter (during the process of fatigue crack advance) and the relative eccentricity of the annular crack that loses its axial symmetry in relation to the round bar (cylinder) axis. In addition to the fatigue crack path study, closed-form stress intensity factor (SIF) solutions for the considered geometry (a cylinder with an outer annular crack) are provided in the form of third-degree polynomial expressions as a function of the ligament diameter and the crack eccentricity (both in dimensionless terms). [ABSTRACT FROM AUTHOR]

This paper presents an improved design approach based on the direct strength method (DSM) in American Iron and Steel Institute (AISI) design specification S100 for cold-formed steel (CFS) built-up closed cross-section columns subjected to local, global, and local–global interaction buckling modes. Initially, the failure mode and load data corresponding to various design parameters such as intermediate fastener connection spacing, boundary conditions, material properties, slenderness, and cross sections from various researchers are collected, including the authors' test results. The design predictions using the current DSM design provisions are compared with the collected test results. The results show that the current DSM approach requires improvisation to adequately predict the axial compression load. The data are then analyzed to understand the behavioral features of the built-up closed cross-section column such as limit for interaction buckling, erosion of strength due to arrant interaction buckling, and increase in strength due to flange or web overlapping effect. The interpretation methods used to improve the current design approach are presented. The original DSM design procedure is improved by failure mode classification and modified slenderness to account for increase and erosion in strength. Finally, the safety (accuracy and reliability) of the design predictions from the improved DSM-based approach is assessed using the large amount of data collected. Since the introduction of the direct strength method to the North American Specification for the Design of Cold-Formed Steel Structural Members (AISI S100) in 2001, it has gained traction among design engineers due to its simplicity, advantages over other design methods, and specific design curves for individual buckling modes. To implement the DSM for CFS built-up members, several researchers have proposed different design approaches, and research is still happening. This study is also aimed toward the same objective but is specific to the local–global interaction in built-up members. It is demonstrated why the DSM prediction is unsafe for CFS built-up members with larger intermediate fastener connection spacing and excessively safe for CFS built-up members with closer intermediate fastener connection spacing. An intermediate fastener connection spacing limit that separates the local–global interaction buckling and element overlapping effect is determined. A design proposal for limiting the interaction buckling mode and considering the overlapping effect of elements in the DSM design method is suggested. More specifically, the proposed design method is in line with the current AISI approach so the designer need not confuse how to use this new design approach in practice. Therefore, for further ease of understanding, two design examples for built-up closed cross-section columns—(1) subjected to local–global interaction buckling; and (2) subjected to element overlapping effect—are included in this paper. It is also recommended that future research may focus on further classifying the AISI main specification sections, E2 and F2 (simple classifications based on the global failure modes), based on the interaction buckling modes in built-up cross-section members. [ABSTRACT FROM AUTHOR]

Steel constructions made of circular hollow sections are commonly joined by welding or ring‐flange bolting. An additional, novel joining method is the so‐called hybrid grouted joint. The hybrid grouted joint is characterised by its multi‐layered composition. In contrast to state‐of‐the‐art grouted joints, hybrid grouted joints include thin adhesive layers, which are applied on the steel surfaces prior to grouting. Sand grains are embedded in the yet uncured adhesive. After the curing of the adhesive, the surface has a high degree of roughness. This allows a high‐performance interlock between fine grain grout and the adhesively bonded sand granules across the contact surfaces in the overlap area. The ability to transfer loads across a wide area with low stress concentrations makes the hybrid grouted joint a promising joint alternative especially regarding the fatigue performance. This paper summarises the main findings concerning fatigue behaviour of the hybrid grouted joint under axial loading. Wöhler diagrams were determined in numerous fatigue tests for two combinations of adhesive and grout. [ABSTRACT FROM AUTHOR]

An SHS-CFSHS X-joint is fabricated by welding two square hollow section (SHS) braces to a concrete-filled square hollow section (CFSHS) chord. In this paper, the stress concentration factors (SCFs) of SHS-CFSHS X-joints are investigated through experimental tests and finite element analysis (FEA), with the hot spot stress method serving as the analytical approach. Eight specimens are designed and manufactured, with FE models built in software ANSYS. These FE models are validated against the test results. The specimens are tested under brace axial tension to determine the SCFs of the X-joints. It shows that the concrete filled in the chord effectively reduces the SCFs of the X-joints. To further explore various load conditions and the influence of the parameters, FEA is carried out and a total of 64 FE models are built. Based on the FEA results, multiple regression analysis is used to obtain the SCF formulae of SHS-CFSHS X-joints under axial tension load and in-plane bending load in the brace, respectively. Comparison and analysis of the SCF results obtained from experimental tests, the proposed formulae, and FE simulations reveal that the formulae presented in this study are both conservative and suitable for predicting SCFs. [ABSTRACT FROM AUTHOR]

The paper presents a rigorous analytical approach to predicting the load–settlement behavior of axially loaded piles embedded in sandy soils, adopting the advanced SANISAND model. The problem of the soil state around the pile during loading is formulated as a system of first-order ordinary differential equations, which can be solved as an initial value problem. The derived load–settlement (t–z) curve is then implemented into the load-transfer method to determine the pile's load–settlement behavior in sands and the deformation mechanism of the soil around the pile during axial loading. To verify the proposed analytical approach, a FEM simulation is performed with a user-defined subroutine, demonstrating its capacity to capture the dilatancy behavior of sands as the pile moves downwards. Additionally, a parametric analysis is conducted to assess the influence of the initial void ratio on the stress–strain relationship of the sandy soil around the pile during the loading process. The proposed analytical approach is also compared with a well-established finite-element model and a centrifuge test. The results indicate that the present approach can well predict the elastoplastic load–settlement response of the pile and reflect important phenomena observed from pile tests. [ABSTRACT FROM AUTHOR]

This paper experimentally and analytically investigated the damage and seismic behavior of concrete walls reinforced by low-bond ultra-high-strength (LBUHS) bars. To this end, four half-scale rectangular concrete walls were fabricated and tested under reversed cyclic loading and constant axial compression. The test variables were the shear span ratio and the axial load ratio. Based on the test results, the propagation of cracks on the wall surface, the maximum strain capacity of concrete, the hysteresis loops and envelope curves, the residual drifts, and the strain distributions of LBUHS rebars were presented and discussed. The experimental results showed that all the test walls could exhibit drift-hardening capability until at least a 2.0% drift ratio if LBUHS rebars were anchored by nuts at their ends. The test results also indicated that the maximum strain capacity of concrete was above 0.86%, much larger than the currently recommended 0.4%. After unloading from the transient drift ratios of 2.0% and 2.5% for the walls with shear span ratios of 1.5 and 2.0, respectively, the measured residual drift ratios were controlled below 0.4%, which is less than the critical drift ratio (0.5%) having 98% repairable probability recommended in the FEMA document (P-58) for general concrete structures. Furthermore, a numerical method was presented to evaluate the cyclic response of the test walls, and a comparison between the experimental and the calculated results verified the reliability and accuracy of the proposed numerical method. [ABSTRACT FROM AUTHOR]

This paper focuses on the experimental investigation of the axial load capacity of CFT (concrete-filled steel tube) columns under actual construction conditions during building reconstruction. A total of four samples were loaded up to failure. The varied parameters were the column length and absence/presence of the concrete infill within the steel tube. Further, the analysis is extended to developing a numerical model in the finite element-based software ABAQUS version 6.9. This numerical model includes material and geometrical nonlinearities and was validated with the experimental results. The contribution of the concrete core to the column capacity and the concrete core confinement effect are discussed. Finally, the column capacity was calculated according to several design codes: the Eurocode 4 with and without considering the confinement effect, American specifications, Australian standards, the American Institute of Steel Construction, and the Architectural Institute of Japan. The Eurocode 4 considering the confinement effect provides the closest results to those obtained in the tests. [ABSTRACT FROM AUTHOR]

The compressor serves as a crucial component that influences the performance of the gas turbine engine. Researchers have been endeavoring to explore compressor types that possess a high loading level and high-efficiency characteristics concurrently. In this study, tandem blade technology was applied to a transonic ultra-highly loaded axial compressor, and the Baseline single-blade rotor was replaced by a tandem rotor to take into account the loading level and compressor performance. Detailed investigations were carried out to identify the effects on the aerodynamic performance of the ultra-highly loaded stage and the fundamental flow mechanism within the tandem-rotor stage. This paper presents original design maps for the tandem-rotor stage, and the selection criteria for tandem parameters in tandem-rotor stage are refined. The results indicate that the peak efficiency improved by 0.83%, the stall margin increased by 2.16%, and the choke flow rate rose by 0.30% for the optimal tandem-rotor configuration. The meridional division position of the rotor primarily affects the ratio of loading of the front and rear blades, while the circumferential relative position of the tandem rotor mainly influences the channel types formed by the front and rear blades. Larger values for the meridional division position parameter and smaller values for circumferential relative position parameter should be selected for the tandem rotor design to optimize both the isentropic efficiency and total pressure ratio. This investigation offers the theoretical foundation for the design of a transonic ultra-highly loaded tandem-rotor compressor. [ABSTRACT FROM AUTHOR]

In order to explore the influence of different working conditions on the mechanical properties of dovetail joints, in this paper, the "Qing Dynasty Engineering Rules" of the Ministry of Qing Dynasty and "Wood Construction Technology of Ancient Chinese Buildings" were used as the weighing standards, using the results of wood properties tests conducted by other scholars as a reference, the numerical simulation of pseudo-static load was carried out on the dovetail joints of Qing Dynasty based on the finite element software ABAQUS. The influence of different angles outside the plane of tenon, different materials, different axial loads, and different load positions on the mechanical properties of dovetail tenon joints was investigated. The results showed that: 1) The hysteretic curves of dovetail mortise and tenon are all inverted z-shape. 2) The maximum bending moments at dovetail joints were 0.896, 0.914 kN·m and 0.979 kN·m when the lateral angles of the Fangs were 0°, 1.41° and 2.82°, respectively. When the axial load at the top of the column increases from 0 to 50 kN, the two-way maximum bending moments of dovetail joints change from 0.896 kN·m and 0.523 kN·m to 2.680 kN·m and 5.129 kN·m respectively. The two-way yield moment changed from 0.823 kN·m and 0.473 kN·m to 2.366 kN·m and 4.172 kN·m respectively. When the axial load at the top of the column increases from 50 kN to 100 kN, the changes of the two-way maximum bending moment and yield bending moment do not exceed 1%. 3) The peak viscous damping coefficients of dovetail joints corresponding to horizontal displacements of 0, 25 mm, and 50 mm applied on the beam side are 22.05%, 28.50%, and 29.38%, respectively. [ABSTRACT FROM AUTHOR]

Elastomeric isolation bearings exhibit complex coupled horizontal-vertical behavior. Most existing macroscopic models simulate the quasistatic test results well but have deficiencies in simulating the dynamic behavior of bearings. In this paper, the experimental observations of previous dynamic bearing tests were investigated. The simulation capacity of existing macroscopic models was checked by comparison with the test data. The results show that the calculated axial load and hysteresis loops exhibit undesired oscillations under dynamic excitation. The intrinsic deficiency of existing models in simulating the dynamic response of a bearing was identified as the coupling or off-diagonal terms in the tangent stiffness matrix and the variation of vertical stiffness of the model. Motivated from this key observation, a new macroscopic model was developed to account for the dynamic behavior of bearings, followed by the suggestion of its numerical implementation. Through the introduction of a new axial load expression, the tangent stiffness matrix of the new model was semidecoupled, and the vertical stiffness of the new model remains unchanged, which reduced the interaction between the horizontal and vertical behavior. The simulation capacity of the new model was then validated by comparison with previous test data. The results show that the new model effectively captures the axial load variation and hysteresis loop of the bearings under dynamic excitations. Moreover, it was found that the consideration of the bearing height improved the simulation accuracy, and the size effect of the bearing is critical for isolated structures with large bearing-to-superstructure-height ratio, such as low- to medium-span bridges. [ABSTRACT FROM AUTHOR]

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Featured Application: Inelastic analysis of RC slender beam elements under cyclic loading. The proposed mathematical model, described in detail in Part I of the present paper, aims to solve the common numerical problems that currently characterize classic fiber models when used with a moderate fiber grid for reasons of computational cost. To confirm these objectives, comparisons were made between analytical predictions of the model with experimental results of RC specimens and of a 2D scaled frame for a wide range of parameters that mainly concern slender specimens without significant influence of the bond slip phenomenon, different types of cross section shapes, and various loading histories. The agreement between analytical to experimental results was found to range from very good to excellent in some cases. [ABSTRACT FROM AUTHOR]

As an effective measure to decrease the residual displacement under earthquakes, unbonded prestressed concrete (UBPRC) columns have been carefully investigated in previous research, while the influence of the complex characteristics of near-fault excitations on the residual displacement of UBPRC is less mentioned. This paper, therefore, focuses on the influence mechanism of the pulse effect and vertical effect of near-fault ground motions on the residual displacement of UBPRC columns. The residual displacement, at first, is formulated as a function of the coupled parameter T1-p (the ratio of the structural period to the pulse period). Then, the effect of near-fault vertical ground motion on the residual displacement is qualified based on the established mathematical model. Further, the model has been applied to investigate the effect of structural properties (dead load axial compression ratio, longitudinal reinforcement ratio, prestressing axial compression ratio, prestressing reinforcement ratio) on the residual displacement of UBPRC columns subjected to the joint action of horizontal and vertical ground motions. This research provides a quantitative methodology to quickly obtain the residual displacement spectra of the UBPRC columns under varying conditions combined with ground motion and structural parameters. [ABSTRACT FROM AUTHOR]

This paper presents experimental and theoretical assessments of the structural behavior of circular steel fiber-reinforced concrete (SFRC) columns reinforced with glass fiber-reinforced polymer (GFRP) bars subjected to a concentric axial compressive load. Laboratory experiments were planned to evaluate and compare the effect of different design parameters on the structural behavior of column specimens based on experiments and finite element (FE) analysis. The experimental variables were (i) concrete types, i.e., conventional concrete (CC) and fiber-reinforced concrete (FC), (ii) longitudinal reinforcement types, i.e., steel and GFRP bars, and (iii) transverse rebar configurations, i.e., tied and spiral with different pitches. Sixteen column specimens were fabricated and categorized into four groups with respect to rebar configurations and concrete types. The results showed that the failure modes and cracking patterns of those four column groups were comparable, particularly in the pre-peak branches of load-deflection curves. Even though the average ultimate load of the columns with longitudinal GFRP bars was 17.9% less than that with longitudinal steel bars, the ductility index (DI) was 10.2% greater than their counterpart on average. The addition of steel fibers (SF) to concrete increased the axial peak load by up to 3.1% and the DI by up to 6.6% compared to their counterpart CC columns without SFs. The DI of specimens was increased by higher volumetric ratios (up to 12%) and spiral types (up to 5.5%). The concrete damage plastic (CDP) model for FC columns was updated in the finite element software ABAQUS 6.14. Finally, a new simple equation was theoretically proposed to predict the axial capacity of specimens by considering the inclusion of longitudinal GFRP rebars, volumetric ratio, and steel spiral/hoop ties. Good agreement between the proposed model predictions and the experimental/numerical results was observed. [ABSTRACT FROM AUTHOR]

Coal seam water injection is a widely employed strategy to mitigate dust in coal mines, and the effectiveness of water injection is intricately linked to the internal pore and fracture structure of the coal. During the process of coal mining, the stress induced by mining activities has a significant impact on the pore and fracture structure of the coal mass surrounding the borehole, consequently altering its seepage characteristics. In order to investigate the seepage evolution patterns of coal seams, this study was based on in situ micro-computed tomography (CT) imaging tests to extract the interconnected fracture models of a coal sample under various axial force loading conditions. Subsequently, a numerical simulation was conducted to simulate water injection seepage and analyze the permeability evolution of coal. According to the obtained results, when the axial force was loaded from 431 N to 732 N, the interconnected fractures inside the coal increased, and the seepage velocity and mass flow rate increased slightly. When the axial force was loaded to 1,100 N, the interconnected fractures experienced a further increase in number, leading to the formation of a complicated interconnected fracture network. Therefore, the resistance of water in seepage increased, resulting in a slight decrease in seepage velocity, but a significant increase in mass flow rate. When the axial force reached 492 N after the peak load, a stable interconnected fracture network was formed in the coal, the fracture development became slow, and the seepage rate as well as the mass flow rate reached a relatively stable state. Under the influence of axial force loading, the fracture structure within coal exhibits significant development, leading to a notable enhancement in its seepage characteristics. The research findings presented in this paper hold significant practical implications for the utilization of mining-induced stress in guiding the design of parameters for coal seam water injection and its subsequent field application. [ABSTRACT FROM AUTHOR]

Unconventional oil and gas reservoirs, characterized by low porosity and permeability, often require multistage fracturing techniques for development. The high-pressure fracturing fluids with large volumes can easily cause alternating changes in both temperature and pressure within the casing. Using a theoretical model and field data from hydraulic fracturing operations, this paper calculated the alternating ranges of axial loads and temperatures in the reservoir section. Based on the calculation results, the temperature–load alternating coupling test of the P110 casing was carried out, and the tensile test was performed to analyze the yield strength variation law of the casing material. The results indicate that the yield strength, ultimate strength, and elastic modulus of casing materials are decreased under alternating thermal–mechanical coupling conditions. As the number of alternating cycles increases, there is an initial rapid decrease followed by a slower declining trend. Moreover, the tension–tension (T–T) cycles induce greater reductions in yield strength and ultimate strength than tension–compression (T–C) cycles. Meanwhile, under the same axial load condition, the higher the circulating temperature, the more significant the reduction in yield strength and ultimate strength. In essence, this is the result of the coupling effect of low-cycle fatigue and temperature aging. Finally, based on the experimental data, a yield strength prediction model of the P110 casing under the alternating thermal–mechanical coupling condition was established. The research results provide theoretical guidance for the safe design and material selection of a casing string under multistage volumetric fracturing conditions of shale gas exploration. [ABSTRACT FROM AUTHOR]

This paper presents a computational model for determining the axial responses of short circular steel–reinforced concrete-filled steel tubular (SRCFST) columns. A novel confinement model is formulated for the concrete core, which is effectively confined by the external circular steel tube and the embedded steel section. The modelling scheme of the confinement is programmed using a mathematical model that utilises fibre-element discretisation of column cross-sections. The numerical predictions are verified by experimental measurements and results obtained from finite-element analysis, demonstrating the accuracy of the modelling technology. In addition, existing concrete confinement models for concrete in circular concrete-filled steel tubular columns are assessed. The new confinement model is shown to be superior in replicating the responses of SRCFST columns. The influences of the design parameters on the column's performance are numerically investigated and ranked in order of importance through a sensitivity analysis. In this study, not only is the validity of current design standards in determining the axial load capacity of SRCFST columns examined but a new design formula is also proposed. The proposed confinement model can be employed in numerical procedures for the inelastic simulation of SRCFST columns; the design formula is suitable for use in practical design. [ABSTRACT FROM AUTHOR]

Axial, flexure, and shear loads are the most common loads that could impact any structure. For instance, wall panels and columns majorly carry axial loads from the beam and slabs; they are also susceptible to flexure and shear loads from the wind or earthquake loads. Insulated concrete form (ICF) is a portable component of interconnected expanded polystyrene (EPS) panels filled with concrete. EPS remains in place and becomes part of the wall to enhance thermal resistance and structural performance. This paper focuses on an experiment that investigated the performance of ICF wall panels under axial compression and flexure. EPS with a higher density of 20 and 40 kg/m3 and a higher thickness of 50 and 100 mm was selected to prepare ICF wall panels for this experimental investigation. In addition, the plain concrete panel was cast for reference. Axial, flexure, and shear load-carrying capacity, load displacement, load–deflection profiles, crack propagation patterns, failure nature, and strain energy are analyzed and reported in this paper. It was observed that ICF panels were superior to plain concrete panels in terms of axial, flexure, and shear load-carrying capacity, failure nature, and absorbed strain energy. [ABSTRACT FROM AUTHOR]

The new-type stainless steel–concrete–carbon steel double-skin tubular (SCCDST) members, characterized by their exceptional corrosion resistance and mechanical bearing capacity, have promising applications in ocean engineering, particularly in deep-water engineering. The external hydraulic pressure and interfacial action of various materials intensify the complexity of composite performance of SCCDST members. This paper describes an analytical investigation on the concentric compressive performance of SCCDST members under external hydraulic pressure. The full-range mechanism, including load–displacement response, bearing capacity contribution, and contact pressures, was investigated through the finite element (FE) model that was validated by the failure mode, bearing capacity, and response of axial load versus strain. Subsequently, influences of key geometric–physical parameters were analyzed, e.g., diameter-to-thickness ratios (Do/to, Di/ti), material strengths (fyo, fyi, and fc), hollow ratios (χ), and water depths (H). Typical results indicate that: the initial active confinement action derived from the hydraulic pressure can enhance the interfacial contact pressure and axial compression capacity of SCCDST members due to the tri-axial compression state; the enhancement of confinement effect is mainly from the interfacial interaction between outer stainless steel tube and concrete infill; influence of water depth on bearing capacity cannot be ignored, e.g., the bearing capacity of an SCCDST member with larger hollow ratio (χ = 0.849) is not enhanced under a higher hydraulic pressure (H = 900 m) because of the cross-sectional buckling failure risk. Finally, a modified method considering the effect of water depth was proposed and verified for SCCDST members under hydraulic pressure. [ABSTRACT FROM AUTHOR]

This paper presents a method for determining the axial and radial load distribution of the moment generated in a V-band clamp and is validated experimentally using finite element analysis (FEA). The method comprises a slotted flange, which is distinguished by having three different profiles for different levels of load symmetrically divided among eight sectors. Each sector is characterised and calibrated. The load cell is analysed using finite element Abaqus software to predict and corroborate the system. In the experimental test, the axial and radial loads are measured using strain gauges for each sector and the total axial load is validated by three button sensors. Tests on the V-band clamp were successfully carried out and indicated a non-uniform distribution of axial and radial loads, with three highlights relating to existing papers: improved results for axial loads, new results for radial loads and an analysis of the moment and its direction, which is consistent with finite element studies. [ABSTRACT FROM AUTHOR]

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In recent years, a lot of studies were performed on the mechanics of beams. One of the most important aspects of the computations regarding these problems are the stresses and deformations caused by combined mechanical and thermal loads. This paper deals with the determination of the deformation of homogeneous isotropic linearly elastic beams under the action of axial load and thermal loading. In our problem prismatic a beam is considered, which is subjected to combined thermal and mechanical loads, and our aim is to present the analytical solution to this problem when the temperature field is a specific linear function of the cross sectional coordinates. The applied mechanical load consists of an axial load and bending moment applied them at the end cross sections of the considered prismatic beam. The thermal loading is obtained from a temperature field which is a linear function of the cross–sectional coordinates. [ABSTRACT FROM AUTHOR]

This paper reports the results of three thin wythe precast sandwich panels tested under axial load. Panel reinforcements and shear connectors in the current state of precast sandwich panels in the civil construction context are evaluated. The authors measured displacement at two distinct panel heights as well as along the panel width to provide load–displacement behavior at the cross-section level and broaden the experimental data on the subject. The test results developed in this research showed good agreement with the results available in the literature. In addition, as concrete-wall panel strength equations have been linked to the compressive behavior of precast sandwich panels, a brief review of empirical formulae is also offered in this paper. Moreover, empirical data since 2005, on both concentrical and eccentrical load testing available in the literature, are also reported. [ABSTRACT FROM AUTHOR]

Quantification of seismic damage to reinforced concrete (RC) members in terms of damages states is important for condition assessment and performance-based seismic design. This paper presents a classification for axially-loaded flexural-dominant well-detailed RC members into clearly-differentiated damage states based on change in failure mode, principles of mechanics, and loss in lateral load capacity. The paper considers extreme fiber compressive strain as the Engineering Response Parameter (ERP) for classification of the damage states. The identification of member damage states based on compressive strain can be very useful for seismic assessment of the existing buildings and performance-based design of new buildings. Published experimentally observed cyclic force–displacement relationships of RC columns have been numerically simulated and are used to develop statistics of compressive strain. These are further used to develop semi-empirical expressions for extreme fiber compressive strain in terms of RC member properties, viz. axial load ratio, longitudinal reinforcement ratio, and confinement reinforcement ratio. It is shown that the proposed expressions accurately predict experimentally observed compressive strain at different damage states. The fragility functions of damage states, that provide the probability of occurrence of the strain limits, are also presented. It is seen that the proposed expressions for strain and their limits accurately identify the damage states on the monotonic stress–strain relationship of confined concrete and validate the use of strain as an ERP. The present study also provides strain limits for different damage states with consistent level of conservatism. [ABSTRACT FROM AUTHOR]

In the process of high flow rate fracture and high gas production, the sealing performance of the premium connection decreases due to the dynamic load and vibration of downhole tubing strings, which may cause accidents. Existing static analysis methods cannot effectively explain this phenomenon. The main objective of this paper is to propose a novel analytical method for evaluating the sealing performance of a premium connection. In this paper, a dynamic model of sealing surfaces of the premium connection is established based on the vibration equation of elastic rod, and the hysteresis characteristics and energy dissipation mechanism of sealing surfaces are analyzed. Considering the influence of spherical radius, internal pressure, axial cyclic load amplitude, and modal vibration, a spherical-conical premium connection finite element model is established to analyze the influence laws of the connection's energy dissipation and sealing performance. The results show that the sealing performance of the premium connection under dynamic load can be effectively analyzed by using energy dissipation theory compared with traditional static contact analysis. Compared with the vibration of the tubing string, the dynamic loads caused by the change of fluid pressure and flow rate in the tubing string have a significant influence on the connection's sealing performance. When the internal pressure and axial cyclic loads are 80 MPa, 400 kN, or 60 MPa and 500 kN respectively, serious plastic deformation occurs in the thread and sealing surfaces, and the energy dissipation of the sealing surfaces increases significantly, which could lead to sealing failure. [ABSTRACT FROM AUTHOR]

Over the past 20 years, as the depth and diameter of shaft lines increased in China, the cracking and water leakage of the inner walls of frozen shafts have become increasingly severe, resulting in significant safety threats and economic losses. Understanding the stress variation patterns of cast-in-place inner walls under the combined effects of temperature and constraint during construction is a prerequisite for evaluating the crack resistance performance of inner walls and preventing water leakage in frozen shafts. The temperature stress testing machine is an important instrument for studying the early-age crack resistance performance of concrete materials under the combined effects of temperature and constraint. However, existing testing machines have shortcomings in terms of applicable specimen cross-sectional shapes, temperature control methods for concrete structures, and axial loading capacity. In this paper, a novel temperature stress testing machine suitable for the inner wall structure shape, capable of simulating the hydration heat of the inner walls, was developed. Then, a reduced-scale model of the inner wall according to similarity criteria was manufactured indoors. Finally, preliminary investigations of the temperature, strain, and stress variations of the inner wall under 100% end constraint conditions were conducted by simulating the actual hydration heating and cooling process of the inner walls. Results show that the hydration heating and cooling process of the inner wall can be accurately simulated. After approximately 69 h of concrete casting, the accumulated relative displacement and strain of the end-constrained inner wall model were −244.2 mm and 187.8 με, respectively. The end constraint force of the model increased to a maximum value of 1.7 MPa and then rapidly unloaded, causing the model concrete to crack in tension. The temperature stress testing method presented in this paper provides a reference for scientifically formulating technical approaches to prevent cracking in cast-in-place concrete inner walls. [ABSTRACT FROM AUTHOR]

This paper discussed the effectiveness of the hybrid use of fiber-reinforced polymer (FRP) reinforcement for the seismic retrofitting of substandard reinforced concrete (RC) columns. Four columns, except for the reference, were retrofitted with externally embedded FRP (EE–FRP) bars in a longitudinal and external FRP jacket in the transverse directions. The test parameter was the configuration of the FRP bars that were used for retrofitting along the longitudinal direction (e.g., single or hybrid use of different types of FRP bars, such as aramid (AFRP), glass (GFRP), or carbon fiber–reinforced polymers (CFRP). The test results indicated that a significant enhancement in the lateral load capacity (≤198% in the unstrengthened column) could be achieved through the hybrid use of FRP bars under reversed cyclic lateral displacement and a constant axial load without a significant sacrifice in deformability. In addition, the test results yielded insights into the strain (ɛ) capacities of longitudinal FRP bars in tension and their contribution to compression resistance under reversed cyclic lateral loading conditions. In addition, an analytical study was conducted to predict the cyclic flexural behavior in substandard RC columns that were retrofitted through the single or hybrid use of EE–FRP bars that considered the debonding behavior of longitudinal CFRP bars with a smooth surface. [ABSTRACT FROM AUTHOR]

According to the previous earthquake reconnaissance, existing reinforced concrete buildings with intermediate short columns are vulnerable to shear failure. Thus, a simulation of the behavior of intermediate short columns has a significant influence on the seismic evaluation. This paper tests eight intermediate short columns in shear failure cases with different combinations of structural parameters, such as height-to-depth ratio, transverse reinforcement ratio, and axial load ratio. According to the test results, this paper proposes a lateral load-displacement curve for the intermediate short column failed in shear with a height-to-depth ratio of between 2 and 4. In addition to comparing the proposed curve with the test data in this paper, data from other literature are also used for verification. Test verification indicates that the proposed curve possesses a reasonable prediction, which is helpful for seismic evaluation of existing buildings. [ABSTRACT FROM AUTHOR]

The displacement of a loaded pile could be vertical (axial) or horizontal (lateral); these displacements are sensitive to groundwater presence within the soil mass. This paper presents a theoretical study to investigate vertical and horizontal displacement of piles embedded in a clayey soil for different levels of groundwater under the ground surface. The study was performed using the commercial finite element package PLAXIS-3D. Three diameters of the concrete piles were considered: 0.5, 0.75 and 1 m, and were subjected to 1,000 kN axial load. The effect of 0, 5, 10, 15 and 20 m groundwater along the 20 m pile in length from the ground surface on the vertical and horizontal displacements was investigated. The results indicated that the vertical and horizontal displacements increase when the ground water level increases towards the base of pile. Also, there is a significant increase in the horizontal displacement up to 15 m of groundwater level from ground surface and decreased at levels from 15 to 20 m. [ABSTRACT FROM AUTHOR]

BACKGROUND: Although the internal fixation technique for scoliosis is effective, there is a great risk of nail placement in actual operation. OBJECTIVE: To compare the effects of three different nail placement strategies on LenkeC patients with scoliosis under cyclic loading. METHODS: Firstly, the finite element model was established by using CT scanning images and X-ray images of patients with LenkeC scoliosis. Secondly, the validity of the model was verified. Finally, the harmonic response analysis and transient dynamic analysis were carried out. Results: The results showed that the maximum amplitude of each vertebral body appeared in the Z direction at the third natural frequency and the amplitudes of each corresponding vertebral body were very close under three kinds of nail placement. Under different nail placement methods, the uneven distribution of nails would make the model produce obvious stress concentration, but the principal stress of vertebral body and nail rod was far lower than its own yield strength. This showed that under the axial cyclic load, the vertebral bodies of scoliosis tended to have larger impact in Z direction. From the point of view of dynamics, it was feasible to reduce a certain number of nails in operation. CONCLUSION: This paper revealed that it was feasible to reduce a certain number of nails during surgery. [ABSTRACT FROM AUTHOR]

Legacy gas pipelines experience problems as they age. Pipe rehabilitation and replacement using internal pipes or liners is a trenchless renewal approach to address these issue-prone facilities. Here, a set of performance objectives is identified using data from both the field and the literature. First, observations of recorded pipeline incidents of cast/wrought iron gas distribution mains were analyzed to understand the causes of damage in host pipe systems. Natural force damage, including subsidence, frost-related deformation, and other earth movements, was identified as the leading cause of incidents in such systems. An internal-repair pipe would be expected to withstand such events. Secondly, a literature review of the mechanical behavior of rehabilitating internal pipes or liners was performed. Considerable work has been performed to understand how such systems behave under internal hydrostatic pressure, external pressure, surface loads, and external loads reflective of expected earth movements. Under internal pressure, stresses higher than that expected for an unconfined repair pipe or liner can develop at large holes in the host pipe. Studies to understand earth movements in rehabilitated pipelines often apply bending moments or axial loads to repaired specimens with joints or full-circumferential cracks. The literature demonstrated that the behavior of internal pipes or liners at discontinuities in the host pipe is critical for rehabilitated pipeline performance. Most available studies, however, have focused on nonstructural or semistructural repair systems, which may be unsuitable for full rehabilitation of deteriorating gas pipelines over an extended design life. The set of performance objectives described in this paper will help improve the understanding of structural pipe-in-pipe to enable effective design and implementation of trenchless repair systems for existing natural gas pipelines. Aging pipes can be repaired with internal rehabilitating pipes. This review provides insight into the causes of problems in gas distribution mains of cast/wrought iron, an important subset of legacy gas pipelines, by analyzing field observation records from between the years 1970 and 2020. Natural force damage was an important driver of damage; common subtypes of natural force damage are related to flexural deformation. Such deformation needs to be addressed by an internal repair pipe. Many researchers have studied the mechanical response of pipes repaired with internal pipes or liners. In these studies, the major loads are reflective of internal pressure, external pressure, surface loads, and soil movements. Interaction between the aging host pipe and internal rehabilitating pipe is an important factor. Performance objectives for internal rehabilitating pipes are outlined in this paper on the basis of field observations and existing work. The systematic identification of performance objectives most critical to these systems is intended to provide a pathway for future development and to qualify new pipe-in-pipe (PIP) system performance over a desired service life. [ABSTRACT FROM AUTHOR]

Natural fiber reinforced composite material has recently attracted interest due to its low density, low cost, acceptable specific characteristics, ease of separation, improved energy recovery, CO2 neutrality, biodegradability, and renewable nature. The goal of this paper is to design and construct a three-wheeled Bajaj door panel using composite materials reinforced with bamboo fiber. Design, manufacture of the component, and experimental techniques are used to meet the goals given. The bamboo plant is the raw material chosen for this thesis project. The matrix material (polyester resin) and hardener used in this investigation, as well as the woven bamboo fiber strip that has been used as reinforcement, were all obtained from local markets. Bamboo fiber that has been chemically treated with 5% NaOH and 95% purified water is used. Keeping in mind the needs of varied testing conditions and characterization standards, polyester resin and E-glass fibers were simply stirred together by hand for 15 minutes. The mixture was then put into the molds. In three distinct orientations (0°, 90°, and 0/90°), composite samples of bamboo fiber were created. In order for the part to respond to axial loads, shear loads, and side loads, it may need 0°, 45°, and 90° plies, respectively. The paper model's 0° orientation was chosen in accordance with the findings of the samples' analysis. Due to the direction of the applied load, it affects the strength design requirements. Based on the findings of the experimental data examination, it was determined that the respective values for tensile, compression, bending, and water absorption were 160 MPa (0°), 2709.2 MPa (90°), 110 N (0/90°), and 4%, respectively. The geometric model of the door panel on the three-wheel Bajaj vehicle's door was designed. Based on these findings, it is suggested that the new exterior structural car door panel of the three-wheel Bajaj Compact 205 model be made of composite materials made of bamboo fiber reinforced with polyester and having strength of 160 MPa. [ABSTRACT FROM AUTHOR]

Understanding the axial loading response of pile group located near the crest of the slope is of practical value to structural design. In this paper, a large-scale test setup (1.8 m x 0.90 m x 0.90 m) has been developed to investigate the response of pile group (2 x 2) located near the crest of the slope under axial loading. This paper presents a series of physical modelling tests performed to investigate the effects of slope angles, distance of the pile group from the slope crest, embedment length of the pile group and pile diameter on the axial loading response of pile groups. The results show that the response of pile group located near the crest of the slope approaches to the level ground condition with increasing edge distance from slope crest. In addition, the horizontal displacement of pile group towards the slope face increases with decreasing distance of pile group from the slope crest or embedded length of piles or with increasing slope angle. Furthermore, increasing pile diameter results in a low increase in the horizontal displacement for edge distances less than 3 dp (dp = pile diameter). However, the horizontal displacement is almost independent of pile diameter at edge distances greater than 3 dp. Higher embedded length results in the response of pile group approaches to the response of pile group located on the level ground at a shorter edge distance from the slope crest. [ABSTRACT FROM AUTHOR]

This paper introduces a novel type of buckling restrained braces (BRBs) called core-separated assembled BRBs (CSA-BRBs). These braces are comprised of two single BRBs that are confined by lightweight concrete-infilled tubes, which are longitudinally connected by two continuous webs. The CSA-BRBs utilize materials more efficiently by increasing the height of the webs to create a large inner cavity, leading to an economical design. This paper predicts the threshold of the restraint ratio of CSA-BRBs approximately. This is achieved by assuming that the maximum moment resulting from applied loads at mid-height is less than the moment-bearing resistance that is conducted according to the outermost fiber of the external restraining section reading yielding. Elastic-plastic numerical analysis is conducted using FEM with beam elements for CSA-BRBs that are subjected to both monotonic and cyclic axial loads. The load resistance, hysteretic performance, and failure mechanism of CSA-BRBs are investigated by varying their restraining ratios. It is recommended that the restraint ratio threshold of CSA-BRBs under monotonic axial compression is used as a bearing type and the restraint ratio threshold of CSA-BRBs under axially compressive-tensile cyclic loads as an energy-dissipation type. This method provides a complete design for CSA-BRBs. [ABSTRACT FROM AUTHOR]

In the context of tall building design, the tube concept represents one of the most performing systems. The diagrid is the widespread type of tube system and consists of a diagonal grid of beams that wraps the building, forming a diamond pattern. It performs as lateral bracing and is additionally able to sustain vertical loading through axial forces. Despite its efficiency, a growing interest is recently observed in alternative geometries to replace the diagrid pattern and improve the architectural impact conferred by the building skin aesthetics on the urban environment. The paper pursues the use of a Voronoi mesh, in which the geometry of the cells is steered to known schemes for the structural design of a cantilever tube structure. The objective is to mimic a macroscopic structural behavior through a topology and size modification of the Voronoi mesh that increases the density for creating resisting paths with higher stiffness. The paper proposes a novel method Vorogrid for designing a new class of tall buildings equipped with an organic‐looking and mechanically sound tube structure, which makes them a valuable alternative to competitors (diagrid, hexagrid, random Voronoi). Diagrids and hexagrids still remain more efficient in terms of forces and displacements but are characterized by a more usual appearance, instead Vorogrid offers more design control and better performances on average with respect to random Voronoi structures. This method is streamed into a pipeline that includes grid initialization strategies, geometric and structural optimization to mitigate the effects of the grid randomness, and structural sizing. [ABSTRACT FROM AUTHOR]