Horizontal Loads Research Articles

Low-cycle fatigue behaviour of concrete-filled double skin steel tubular (CFDST) members for wind turbine towers

Wind energy has the advantages of being clean and renewable. Wind turbine towers endure horizontal cyclic loads that could influence the performance of entire structure. To clarify the low-cycle fatigue behaviour of concrete-filled double skin steel tubular (CFDST) members, a total of 16 specimens were experimented. The hollow, slenderness, and axial compression ratios are specifically designed to clarify the effects on performance under constant amplitude loading and hysteretic loading conditions. The typical failure modes under both loading conditions and the relationship between loop strain, loop bearing capacity, loop energy dissipation, cycle number, and various degradation indices were analysed. Studies indicate that the failure mode under low-cycle fatigue loading is mainly local deformation, which includes transverse fracture occurring at the region between the steel tube and ribbed stiffener, the crushing concrete. Fatigue specimens with different amplitudes exhibit varying shapes of hysteresis responses. Higher amplitudes could enhance damage and significantly reduce fatigue life. Increasing the hollow and axial compression ratios boosts the energy dissipation capacity, and decreasing the slenderness ratio enhances the lateral resistance. A 2 % constant amplitude preload intensifies the degradation of bearing capacity and energy dissipation under subsequent constant amplitude loading.

The Influence of Pile Shaft Distributed Grouting on the Horizontal Load Response of Rectangular Piles

The Influence of Pile Shaft Distributed Grouting on the Horizontal Load Response of Rectangular Piles

Advantages of using DIC for capturing mechanical shear sliding behaviour of the FRCM strengthened masonry

This paper aims to analyse the advantages of using Digital Image Correlation (DIC) method to capture the effects of the FRCM on masonry wall shear failure. In the scientific literature, most of the experimental programs is focused on strengthening against flexural failure by means of bending tests and against shear, diagonal cracking, by means of diagonal compression tests. The shear failures are one of the main failure modes for the in-plane behaviour of masonry walls in case of horizontal loads. This study primarily focuses on experimentally determining the capacity of clay brick masonry under sliding shear loads for different normal stress levels with a standard test method. The assessment of shear capacity is based on a Mohr-Coulomb failure criterion depending on the external axial load, the internal friction angle and the cohesion values for unreinforced masonry. The experimental tests have been carried out on both unreinforced and strengthened specimens. The results of the tests demonstrate that FRCM, despite the reduced anchorage length in the tests, can significantly enhance the structural performance of masonry structures for sliding shear failure mode. In addition, DIC method is used to analyse, in greater detail, the cracks and the strain evolution in order to analyse the failure of specimens.

Seismic performance of precast UHPC pipe pile with two pile-cap beam connection types: An experimental and numerical study

To develop an effective pile foundation scheme for earthquake-prone regions, this study introduces a novel pile structure that integrates ultra-high-performance concrete (UHPC) with traditional prestressed high-strength concrete (PHC) pipe piles. The research focuses on assessing the impact of various connection forms between the pile and cap beam on the seismic performance of bridge substructures. Two 1/3-scale specimens were meticulously designed and tested: one featuring a cast-in-place (CIP) connection and the other incorporating precast assembly (PA) connection between the pipe pile and cap beam. Cyclic loading tests were conducted to evaluate the failure mode, lateral capacity, ductility, energy dissipation ability, residual displacement, rebar strain, curvature distribution and rotation of UHPC pipe piles with the two connection forms. The results indicate that the specimen with a CIP connection exhibits a higher horizontal load capacity and stronger energy dissipation ability, while the specimen with the PA connection displays superior self-centering ability, increased ductility, and causes less damage to the cap beam. Finally, finite element models were developed to analyze the effects of design parameters on the seismic performance of the pile connected by the two methods. This research may provide valuable design guidance for incorporating UHPC in pile foundations. To facilitate its practical implementation in engineering projects, further theoretical and experimental research is recommended in this paper.

Assessing the effects of horizontal loads on the ultimate vertical bearing capacity of energy piles: A comparative numerical and analytical study

Previous studies have not extensively explored the collective impact of lateral, axial, and thermal loading on the ultimate vertical bearing capacity of energy piles, qu. This study investigates qu values for energy piles in dry sandy and clayey soils under varying lateral loads and temperature conditions using numerical and analytical solutions, considering temperature-dependent variables. The numerical results were validated against experimental data. The analytical solution aligns well with numerical analyses, though it yields slightly higher qu values in sandy soil. Both numerical and analytical solutions show that cooling and heating can respectively increase and decrease qu under corresponding conditions. Numerical simulations indicate that in clay, lateral load enhances qu, with increases ranging from 8 % to 20 % across different thermomechanical conditions. In sand, the effect of lateral load depends on thermal conditions, increasing by 2 %–5 % during cooling and decreasing by 3 %–5 % during heating. The analytical solution showed that increasing lateral load would increase qu in sand by 0.5 %–2 % and in clay by 1 %–5 %, with a more significant increase in clay. Analytical and numerical parametric studies also revealed the higher influence of soil cohesion and pile diameter on qu values under different thermomechanical conditions.

Effect of soil spatial variability on the stability of pipelines under horizontal loading

Submarine pipeline has been utilized more and more widely in offshore oil and gas transportation engineering. Given that these pipelines frequently subject horizontal loading during operation, thus precise predicting their horizontal bearing capacity is essential. However, most previous studies employ deterministic analysis without considering soil spatialvariability. This article introduces a two-dimensional (2D) random finite element analysis to study the horizontal pullout behaviour and failure mechanisms of a pipeline in a spatial variability soil. It is observed that the effect of soil spatial variability on the horizontal bearing capacity factor and failure mechanisms is remarkably substantial, with the distribution of the former showing a close approximation to a log-normal distribution. Furthermore, the average horizontal bearing capacity typically falls below the corresponding deterministic value. Consequently, the deterministic estimation of the horizontal bearing capacity tends to be inflated. Eventually, a reliability-based approach is formulated, where a factor of safety is incorporated to account for the uncertainties arising from spatial variability and ensure a sufficient safety margin. This methodology enables engineers to determine appropriate factor of safety tailored to the specific requirements of each project.

A Wave Drift Force Model for Semi-Submersible Types of Floating Wind Turbines in Large Waves and Current

The correct prediction of slowly varying wave drift loads is important for the mooring analysis of floating wind turbines (FWTs). However, present design analysis tools fail to correctly predict these loads in conditions with current and moderate and large waves. This paper presents a semi-empirical method to correct zero-current potential-flow quadratic transfer functions (QTFs) of horizontal wave drift loads in conditions with current and moderate and large waves. The method is applicable to column-stabilized types of substructures or semi-submersibles. In the first step, the potential-flow QTF is corrected for potential-flow wave–current effects by applying a heuristic method. Second, the generalized Exwave formula corrects for viscous drift effects. Viscous drift effects become important for moderate and large waves. Conditions with current in the same direction as the waves increase the viscous drift contribution further. The method is validated by comparing QTF predictions with empirical QTFs identified from model test data for the INO Windmoor semi. While potential-flow QTFs agree well with the empirical data for small seastates without current, they underestimate the wave drift loads for moderate and large seastates. Conditions with current increase the underestimation. The semi-empirical correction method significantly improves predictions.

Research of coordinated deformation characteristics for diesel engine main bearing based on bearing clearance margin

A method for characterizing coordinated deformation of diesel engine main bearing is proposed to address the problem that traditional evaluation indexes are difficult to accurately characterize the coordinated deformations of the main bearing shell and the crankshaft. The margin between the main bearing clearance and the assembly clearance is employed to judge whether motion interference occurs between the main bearing shell and the crankshaft journal after deformation. The numerical calculation method for the main bearing clearance is proposed. Experiments are designed and conducted to verify the feasibility and accuracy of the evaluation index. The influencing mechanisms of sensitive parameters on the coordinated deformation characteristics of the main bearing are explored based on the orthogonal test. The results show that it is feasible to take the main bearing clearance as the evaluation index of the coordinated deformation. The relative errors between the calculation results and the measurement data of the centripetal radial deformation of the main bearing shell in the preload condition and the main bearing loading condition are less than 7% and 9.7%, respectively, indicating the accuracy of the computational method. The main bearing clearances tend to decrease with the increase of horizontal and vertical bolt loads until they remain basically constant. The main bearing clearance decreases with the increase of the interference followed by a slight increase, while it is positively correlated with the side clearance. This study provides theoretical basis for main bearing stiffness reliable design of HPD diesel engine.

Thermo‒mechanical behavior of energy pile group in dry sand subjected to a horizontal load

The energy pile is an innovative structure element designed to utilize geothermal energy while simultaneously supporting building loads by means of integrating heat exchange tubes into the pile foundation. Despite the intricate thermodynamic characteristics of energy pile groups, research on them remains limited. This study investigated the horizontal load transfer mechanism of an energy pile group in dry sand by conducting a model test on a 2 × 2 energy pile group subjected to horizontal loads. Specifically, the impact of heating or cooling a single pile within the energy pile group was examined. The results showed that the bending moment was significantly larger on a single pile subjected to a thermal load than that of the other piles, with the majority of this variation occurring in its upper part. Additionally, the horizontal load had a strong influence on the rotational angle and horizontal displacement of the energy pile group. The rotational angle and horizontal displacement decreased with increasing depth. With rising temperature, the interaction between the pile and the soil intensified, and the soil pressure on the upper part of the pile increased while that in the lower part decreased.

Investigation of plastic hinge length in high-ductility reinforced concrete shear walls

In this study, the plastic hinge lengths of reinforced concrete (R/C) cantilever shear walls were analytically determined considering various design parameters. Nonlinear static (Pushover) analyses were conducted on R/C shear wall models and their nonlinear behavior was examined using ABAQUS software. In the study, 72 shear wall models with different parameters were analyzed under the influence of vertical and horizontal loads. Parameters whose effects on plastic hinge length were investigated height/length ratio (Hw/Lw), axial load ratio (N/No), and horizontal web reinforcement ratio (ρsh). The load-displacement graphs of the modelled shear walls were obtained. The plastic hinge height of shear walls was determined according to the heights of the deformations in the concrete and longitudinal steel reinforcement in the section when the shear walls lateral load decreased by 15%. The analytical plastic hinge lengths (Lpz) were determined with respect to the location of the yield occurred at the longitudinal steel reinforcement of the shear wall. The observed plastic hinge lengths (Lp) were determined based on the height of observed the crush as of the foundation top level in the concrete shear wall model. The relationship between the findings of this study and empirical formulas in the literature was determined. It was determined that there is greater closeness between the values obtained from empirical formulas in the literature and the observed plastic hinge length values. It was observed that the plastic hinge length generally increases as the shear span increases. It was observed that the change in ρsh was not a very effective parameter in plastic hinge formation. As the N/No decreases, the plastic hinge length values ​​ generally increase. The Lp/Lpz ratio varied within the range of 0.15-0.50. In addition to ductility (μ) values were determined by using the displacements determined according to both the crushing occurred in the shear wall concrete and the yield observed in the steel reinforcement. The observed that the ductility value depends more on Hw/Lw ratio as N/No ratio decreases.

Forced vibration of liquid-filled composite laminated shell container considering fluid–structure interaction by the scaled boundary finite element method

In this paper, the scaled boundary finite element method (SBFEM) is first applied to the forced vibration analysis of partially liquid-filled composite laminated shell structure considering fluid–structure interaction. In comparison with the finite element method, the SBFEM only requires discretization of the boundary of the solution domain, which can reduce the spatial dimension of the problem by one and provide the radial analytical expressions for the variables within the solution domain. The structure consists of a multi-layered fiber-reinforced composite laminated shell and incompressible, inviscid, and irrotational liquid. After separately describing the basic expressions for the fluid and composite laminated shell, which includes the transformation of three coordinate systems and the establishment of the constitutive equations for the shell, the governing equations for the fluid and shell structure using the scaled boundary finite element method and modified SBFEM based on scaling surface transformation are formulated, respectively. Meanwhile, the Newmark method and synchronous solution algorithm are employed for the fluid–structure interaction analysis. Subsequently, two validation cases are conducted to assess the accuracy and convergence of the model. Finally, two numerical examples are employed to perform a parameter analysis on the model, involving the response of the system to ground horizontal harmonic excitation and seismic load. The results indicate that the SBFEM, as a semi-analytical high-precision numerical method, can be effectively used to simulate fluid–structure interaction problem of partially liquid-filled laminated composite shell structures.

On the contact of an absolutely rigid stamp with a half-plane taking into account static friction

Abstract The plane deformable state of an elastic half-plane into which an absolutely rigid stamp is pressed with friction is considered. It is assumed that the tangential stresses acting in the contact zone are related to normal pressure by the law of dry friction, the coefficient of which is a linear function of the coordinate of the contacting points of the contacting bodies. A determining singular integral equation for the stated problem is obtained, the solution of which is constructed in closed form. Numerical analysis is conducted, and regularities in the variation of contact stresses are determined depending on the ratios of horizontal and normal loads applied to the stamp.

ANALISA PEMBEBANAN DAN DAYA DUKUNG TANAH DENGAN PONDASI TIANG PANCANG BERDASARKAN DATA N-SPT PADA PEMBANGUNAN GEDUNG IAIN PADANGSIDEMPUAN

Foundations are a type of construction that forms the basis of a building in direct contact with the ground and functions as a support for the building above it, aiming to transfer vertical and horizontal loads gradually and evenly to the soil layers. The IAIN Padangsidempuan North Sumatra Building project will begin construction from January 6 2022 to October 30, 2022. This building is intended for lecture halls with a capacity of 5 floors. Using a pile foundation with a depth of 18 meters with a diameter of 0.5 meters. From the calculation results, it is found that the carrying capacity of 1 pile for PC4D50 = 154.92 tons and the bearing capacity of the foundation in the group is Qg PC4D50 = 406,509 tons and PC3D50 = 154.92 tons, and in 1 group PC3D50 = 349,963 tons, which is different from the initial plan for 1 pole. for PC4D50 it is = 157.84 tons and for 1 group = 414.17 tons and for PC3D50 for 1 pole = 157.84 tons and for 1 group = 356,561 tons. For PC4D50 the results are as follows: For Direction D19 – 150, for PC3D50 obtained as follows: For Direction Initial planning Y direction D19 – 150.

Efficiency of FRPU strengthening of a damaged masonry infill wall under in-plane cyclic shear loading and elevated temperatures

This paper presents results of in-plane shear tests carried out at the ZAG laboratory in Ljubljana (Slovenia) on a RC frame with masonry infill made of clay blocks (KEBE OrthoBlock). The frame was loaded with constant vertical loads at the top of the columns and then by gradually increasing horizontal cyclic loads at the top beam level. Acquired forces and measured displacements allowed capturing hysteretic behavior for determination of dissipation energy. In addition, two Digital Image Correlation (DIC) systems, Aramis and the CivEng Vision, were used to visualize the behavior of the tested specimens, with an emphasis on computing locally required information about the behavior of highly deformable interfaces. Three types of specimens were tested in-plane: the reference specimen in form of plain RC frame, the reference specimen with constructed masonry infill without any strengthening and the specimen, previously damaged and then strengthened on both sides using glass mesh bonded to the infill and the RC frame using flexible adhesive made of polyurethane matrix (Glass Fiber Reinforced PolyUrethane - GFRPU system). The strengthening process, allowed the specimen to withstand additional cyclic loads, reaching a maximum drift of 3.6 % without serious damage disqualifying the structure from further exploitation. The GFRPU strengthening system was found to be highly effective in preventing infill collapse of damaged masonry infill wall during in-plane loading. Additionally, the results of extended thermal analysis of PU are presented as polymers are, in general, a material, poorly resistant to heat. However, the analyzed PU manifested stable properties up to 200 degrees Celsius, which makes this material promising in civil engineering applications at elevated temperatures.

Enhancement of mechanical characteristics and novel damage assessment for timber post and beam structures with K-braces

Glued-laminated Timber Post and Beam Structural System (GTPBSS) gains widely application in timber engineering because of direct force transmission and simple construction. The present work investigates the influence of introducing K-bracing on the lateral performance of the GTPBSS. To this end, four full-scale GTPBSS specimens with and without braces under horizontal loading conditions were carried out. The obtained test results highlight that the GTPBSS without braces exhibited large deformation. The failure modes predominantly centered on the occurrence of wood cracking at both the column-base joint and beam-column joint. In contrast, the GTPBSS specimens equipped with K-bracing elements exhibited failure modes marked by the instability of the brace components. The inclusion of brace system within the GTPBSS structures yielded positive results, effectively reducing lateral deformations while concurrently augmenting both the elastic stiffness and the later maximum load-carrying capacity. However, it is essential to exercise caution with regard to potential out-of-plane instability. A dual-parameter damage assessment model was developed to evaluate structural damage, incorporating factors related to energy dissipation and deformation. The evaluation results derived from this model were consistent with the test results, affirming the rationality and validity of the proposed approach. This model is expected to provide a scientific foundation for formulating strategies for repair and maintenance.

Punching and lateral cyclic behavior of concrete slab-column connections reinforced with steel sheets

During an earthquake, slab-column structures with high gravity-shear ratios often experience increased local shear stress and deformation in the connection area, leading to reduced unbalanced moment capacity and drift capacity of the connections. This study aims to create a new and more efficient method of enhancing the unbalanced moment capacity and deformation capacity of reinforced concrete slab-column structures through using steel sheets as punching reinforcement. Tests were conducted to evaluate the effects of the thickness, extension length, and layout of this new type of punching reinforcement on the unbalanced moment capacity and deformation capacity of the connections when subjected to vertical and horizontal cyclic loads. The results indicated that as the steel sheet thickness increased, the unbalanced moment capacity of SC-2 and SC-3 rose by 24 % and 48 % respectively, while the drift capacity improved by 20 % and 40 % compared to SC-1. Furthermore, the failure mode shifted from stress-induced punching to drift-induced punching. Compared to SC-1, a cruciform layout with an additional diagonal arrangement of sheets increased the unbalanced moment capacity and drift capacity by approximately 17 % and 20 %, respectively. The extension length of the sheets reduced from 600 to 420 had negligible effect on the unbalanced moment capacity and deformation capacity. Utilizing experimental data, this study compared the relationship between the drift capacity and gravity shear ratio of connections reinforced with different shear reinforcements. The underlying causes for the observed lower drift capacity of the specimens are analyzed, and design recommendations for optimizing the steel sheets are subsequently proffered. After thoroughly analyzing the experimental results, a simplified calculation methodology for assessing the shear strength of steel sheets was developed, taking inspiration from the shear strength calculation approach outlined in ACI 318–19. The efficacy of this simplified approach was subsequently validated by comparing the experimental results with those predicted by current design codes. Furthermore, by comparing the experimental results with the predicted values, the relationship between the punching failure mode of connections and their punching strength was discussed.

Dynamic responses of transversely isotropic and layered elastic media with imperfect interfaces under moving loads

Flexible pavement is widely used in engineering practice but is often subjected to the moving traffic loads, with imperfect contact behavior at the interfaces between adjacent layers. This study investigates transversely isotropic and layered elastic media with imperfect interfaces under moving vertical and horizontal loads using a semi-analytical method. The governing equation for moving loads is established within a Cartesian coordinate system and by virtue of the Galilean transformation, which is further decoupled into two ordinary differential equations in terms of the powerful Cartesian system of vector functions. General solutions for any layer are obtained, and the dual-variable position method is applied to derive the semi-analytical solutions for the layered pavement in the vector function domain. The lately introduced refined conversion algorithm, originally from the discrete convolution-fast Fourier transform (DC-FFT) algorithm, is applied to obtain the solution in the physical domain, which can efficiently remove the Gibbs effect near the source. The solutions are validated by comparison with existing solutions and numerical examples are presented to study the effect of interface modulus, moving load velocity, Young’s modulus of asphalt concrete and horizontal/vertical loading ratio on the surface dynamic response of the flexible pavement. Finally, the fatigue and rutting life of the pavement structures corresponding to different imperfect interface moduli are analyzed. The present solution provides practical guidance for the design of flexible pavement.

Finite element analysis of a rubber bearing base isolator under vertical and horizontal loads using a nonlinear hyper-viscoelastic material model

This research is devoted to developing a finite element model using Abaqus code for the computer simulation of an in-house developed and manufactured rubber bearing subjected to static vertical and cyclic horizontal loads. A high-damping rubber compound was designed. The material behavior of the rubber was assumed to be described by the hyper-viscoelastic model. Both linear (Prony series) and nonlinear (strain hardening power law) viscoelastic relationships were used in conjunction with the Ogden-Roxburgh equation to take the addition of the stress softening phenomenon or Mullins effect into consideration. The parameters of the material model were determined using MCalibration code in which an optimization technique was used, and data obtained in experiments carried out on test specimens were fitted into the selected model. The results of the simulations were compared with their corresponding experimental data carried out on the rubber bearing. The force-displacement behavior, stress and strain fields, and computed energy were presented and discussed. It is shown that the nonlinear viscoelastic model accompanied by the Mullins effect gives the best results. Moreover, the model could accurately predict the energy variations during the earthquake loading.

Non-linear response of confined concrete beam-column structures under horizontal loading

In this study, a behavior law for confined concrete is considered with the introduction of transverse reinforcement to increase the compressive strength of concrete, using the model of Mander et al. This model integrates the confinement effects provided by transverse reinforcement, enhancing the load-bearing capacity of concrete under compressive stress. A pushover analysis is carried out on a full-scale, four- levels structure, using the N2 method. This advanced technique combines non-linear static analysis with inelastic response spectra. Using this approach, the structure's seismic performance can be estimated, accounting for its ductility and the non-linear effects at each loading stage. The inelastic response spectra are adjusted using reduction factors based on the structure's capacity to dissipate seismic energy through inelastic deformations. By varying the confinement rate of the concrete sections, different performance points of the structure can be obtained. The confinement ratio is a crucial parameter influencing the ductility and strength of confined concrete. Closer spacing of transverse reinforcement increases the confinement ratio, which improves the concrete's deformation capacity and ultimate strength. The results show the effect of the behavior law used to consider concrete confinement on the performance points of the structure. In particular, it is observed that increasing the confinement leads to significant gains in the strength and ductility of the structure. These results highlight the importance of optimally using transverse reinforcement to design structures that ensure their performance and safety under seismic loads.

Seismic performance of frame with middle partially encased composite brace and steel-hollow core partially encased composite spliced frame beam

Steel-hollow core partially encased composite spliced frame beam (SHSFB) and middle partially encased composite brace (MPECB) demonstrate the potential to economize on steel consumption while exhibiting superior performance. To investigate the seismic performance of frames with SHSFBs and MPECBs, horizontal low-cyclic loading tests were conducted on four frame specimens, involving two two-story frames with no brace and two multi-story X-braced frames. Numerical simulations were performed using the “Open System for Earthquake Engineering Simulation” (OpenSees). The results indicate that the novel composite frames exhibit commendable seismic performance and energy dissipation capacity. The unbraced frame with SHSFBs has deformation capacity and mechanical properties comparable to bare steel frame. In contrast to the frame specimen equipped with bare steel braces featuring a 6 mm flange thickness, the specimen utilizing MPECBs with 4 mm flange thickness exhibits only a slight reduction of 3.60 % in maximum bearing capacity and 2.68 % in initial lateral stiffness. Significantly, each SHSFB and MPECB component reduces steel consumption by 16.71 % and 24.79 %, respectively, compared to bare steel components. Therefore, while ensuring adequate mechanical properties, frame structures equipped with SHSFBs and MPECBs will require less steel. Based on both experimental and simulation results, the formulas for predicting the ultimate bearing capacity and initial lateral stiffness of the novel composite frame were proposed, and the structural design for the multi-story X-braced frame was analyzed, offering valuable insights for practical engineering applications.