Bidirectional Loading Research Articles

Seismic response of rocking bridge systems under three-dimensional ground motions

Compared to theoretical models, finite element methods provide greater versatility for dynamic response analyses of rocking bridges, especially when considering the influences of various nonlinear boundary conditions. A finite element modeling method based on fiber section elements for three-dimensional seismic analyses of rocking bridges is developed in this paper. This method solves the problem of energy dissipation and stiffness determination of the rocking interface. Based on the proposed modeling method, considering nonlinear boundary conditions (such as abutment-soil interaction, impact effect, and pile-soil interaction), the seismic responses of rocking bridges, including free rocking, prestressed rocking and prestressed rocking with dampers, under the excitation of three-dimensional ground motions are analyzed. The results show that: after reasonable design, the prestressed rocking bridge with dampers exhibits similar seismic responses to the cast-in-place bridge, and maintains a good self-centering ability. The responses of all the rocking bridges under bi-directional loading are greater than those under unidirectional loading. In contrast, vertical ground motion's influence on the response of the rocking bridges is minimal. Ignoring the pile-soil interaction significantly underestimates the seismic demand of the evaluated bridges, especially the free rocking bridge and rocking bridge with prestressed tendons only.

Study on anti-reflection of deep soft and high gas coal seam floor by deep hole controlled blasting

Addressing the practical challenges of difficult drilling for blasting-induced permeability enhancement in deep, soft, and high-gas coal seams, where fractures remain underdeveloped and prone to re-compaction, this study proposes blasting operations within the floor strata. This approach aims to enhance the permeability of soft coal seams, thereby extending the duration of effective gas extraction. A bidirectional loading gas–solid coupling blasting simulation system was established in the laboratory, enabling multi-faceted analysis of experimental models through macroscopic crack patterns, internal damage mechanisms, and strain data of coal and rock masses. Comparative experiments were conducted, contrasting various control hole spacings with conventional blasting techniques. The findings reveal that as the blasting stress wave traverses the control hole walls, tensile stress waves are reflected, facilitating crack propagation. The guiding effect of the control holes and the spatial compensation they provide significantly increase the extension distance of explosion-induced cracks, resulting in directional failure of the test specimens and heightened damage in the far field of the blast. After the blasting process, the arrangement of control holes can result in an increase of up to 133% in damage to the coal seam and a reduction of up to 167% in damage to the floorboard compared to the model without control holes. Notably, when the control holes are proximal to the coal-rock interface, the near-end coal body experiences the most pronounced effects, with peak damage and tensile strain in the d = 20 mm model being 1.93 and 1.79 times higher, respectively, than those in models without control holes. Conversely, for control holes located further from the interface, the distal coal body experiences the greatest influence, exhibiting 1.53 and 1.55 times higher peak damage and tensile strain, respectively, in the d = 80 mm model compared to uncontrolled counterparts. Field observations at the C13 coal seam of a mine within the Huainan mining area corroborate these findings, where the volume of gas extraction and its concentration experienced a rapid increase following blasting and penetration enhancement. Optimum permeability enhancement occurs when the blasting hole is situated 4 m from the extraction point, resulting in a 131% increase in gas extraction purity from 0.15 × 10–3 m3/min to 1.97 × 10–3 m3/min. Furthermore, gas concentration soars by 373%, from 5.86% to 21.86%. These research outcomes offer valuable insights and hold considerable reference significance for blasting-induced permeability enhancement in deep, soft, and high gas coal seams.

Bidirectional Cyclic Loading Performance of a Prefabricated Self-Centering Metallic-Damped Steel Column Base

Bidirectional Cyclic Loading Performance of a Prefabricated Self-Centering Metallic-Damped Steel Column Base

Dynamic behavior of kaolin clay under bidirectional cyclic loading for suction bucket foundation

The stability of offshore wind turbine (OWT) foundations is largely influenced by the dynamic characteristics of marine clay. In offshore engineering, marine clays may exposed to bidirectional cyclic stresses. To empirically examine the influence of different cyclic stress magnitudes on the dynamic characteristics of marine clay at different depth, a sequence of dynamic triaxial tests is conducted on marine kaolin clay, encompassing diverse values of the cyclic stress ratio (CSR) and effective confining pressure (p'0). Some valuable inferences have been drawn: At low cyclic stress ratios (CSR≤0.3), the axial strain (εa), stiffness (k), and excess pore water pressure (EPWP) of the specimen exhibit logarithmic increase, logarithmic decrease, and logarithmic accumulation, respectively. Under high cyclic stress ratio conditions (CSR＞0.3), the axial strain increases linearly, the stiffness deteriorates linearly, and the logarithmic excess pore water pressure accumulates. After analyzing the dynamic characteristics data of kaolin clay, the correlation between excess pore water pressure and axial strain was established. By analyzing the vertical cyclic mechanism of suction bucket foundation, a prediction model for suction bucket foundation under vertical cyclic loading was established based on the dynamic characteristics of marine clay and the model was validated. The comparison between the validation outcomes and the experimental outcomes shows good agreement. This study provides certain guidance for the design of suction bucket foundations for OWTs.

Study on interior beam–column joint sub-assemblage under bi-directional loading using finite element analysis

Purpose The purpose of this paper is to study the shearing performance under bi-directional loading of an interior beam–column joint (BCJ) sub-assemblage using the finite element analysis (FEA) tool (midas fea), validated in this research. Design/methodology/approach The BCJ can be defined as an essential part of the column that transfers the forces at the ends of the members connected to it. The members of the rigid jointed plane frame resist external forces by developing twisting moment, bending moment, axial force and shear force in the frame members. On the type of joints, the response to the action of lateral loads depends on reinforced concrete (RC) framed structures. The joint is considered rigid if the angle between the members remains unchanged during the structural deformation. This work examined the shear deformation, load displacement and strength of a non-seismically detailed internal concentric RC joint using non-linear FEA. The bi-directional loading imposes the oblique compression zone on one joint corner. This joint core’s oblique compression strut mechanism differs significantly from that under unidirectional loading. The numerical results are compared with experimental results in this study, with the data published in the literature. Findings Numerical analysis results show that, in the comparative study of numerical and experimental values, the FEA tool predicts the behaviour of the RC BCJ well. The discrepancy between the experimental and numerical results amounts to 6 to 12% end displacement of the beam, 7% resultant joint shear force, 4.23% column bar strain and 0.70% hoop strain. Originality/value The current code of practice describes the joint sub-assemblage behaviour along the single axis individually. In the non-orthogonal system, the superposition of the two axes for joint space results in overlapping the stresses and, hence, the formation of the oblique strut. This may result in a reduction in the joint capacity under bi-directional loading. The behaviour must be explored in depth, and an attempt is made for further exploration.

On the local scour around a jacket foundation under bidirectional flow loading

Jacket structure is a new type of offshore wind turbine foundations with advantages for its lightweight construction, high stability, and suitability for various water depths. However, jacket foundations are often subjected to scouring caused by tidal flows, which can significantly affect the stability of offshore wind energy systems. Limited research has been conducted on the scour characteristics around the jacket foundation under bidirectional flow actions due to the structural complexity. To address this gap, this study performs physical model tests to investigate the effects of flow properties and foundation position on the scour around the jacket foundation. This study assesses the impact of a complex upper truss structure and finite pile height on scouring, in contrast to monopile and regularly arranged pile group foundations. It also analyzes the differences in scour characteristics between a monopile foundation and a jacket foundation subjected to identical bidirectional flow conditions. The impact of flow direction on the scour evolution is evaluated by comparing the scour characteristics under unidirectional and bidirectional flow actions with the same hydrodynamic conditions. The results indicate that the equilibrium scour depth increases with the flow strength and water depth, and reaching its maximum at a foundation angle of 30°. Findings are of great significance for predicting the scour extent around the jacket foundation.

Effect of Drained Multi-Directional Loads on Liquefaction Resistance of Granular Material

ABSTRACT It is well recognized that the liquefaction resistance is closely related to the consolidation stress in soils. However, previous studies investigated the effects of unidirectional consolidation loads rather than multi-directional consolidation loads on liquefaction resistance. In this study, two types of granular materials, spherical glass beads and irregularly-shaped sands, are tested under undrained conditions with the uni- and bi-directional loads to investigate the liquefaction resistance. The effects of consolidation loads on liquefaction resistance can be explained in terms of material anisotropy. In simple shear tests, the stress- and strain-controlled loading paths are adopted for the consolidation and the undrained shear process, respectively. The results indicate that the liquefaction resistances of both materials consolidated under the multi-directional consolidation loads are higher than those consolidated under the linear loads. More consolidation loading cycles induce a better liquefaction resistance of the specimens at a given relative density. In addition, the influence of consolidation stress on liquefaction resistance is demonstrated by the anisotropy of specimens. Cyclic vertical stress, unidirectional shear stress, and bidirectional shear stress applied during consolidation produce greater isotropy and improve the liquefaction resistance of the specimen compared with the monotonic vertical stress, and their effects align with an increasing order.

Bidirectional pendulum-type tuned mass damper inerter for synchronously controlling the alongwind and crosswind responses of super-tall buildings

In the context of slender super-tall buildings, which have a high height-to-width ratio and low damping, significant bidirectional vibrations can occur under strong winds. Traditional TMDI device is mainly focused on controlling unidirectional wind-induced vibration responses. To address this issue, the present study introduces a bidirectional pendulum-type tuned mass damper inerter (BPTMDI) designed to synchronously mitigate alongwind and crosswind responses. The study derives nonlinear equations of motion for a multiple degrees of freedom (MDOF) structure integrated with the BPTMDI, using the Euler-Lagrange method. These equations capture the three-dimensional motion characteristics of the BPTMDI. Additionally, linear equations of motion are derived for a simplified planar model. The time-domain responses of the MDOF structure coupled with the BPTMDI are calculated by dividing the system into linear and nonlinear subsystems and applying the state space method and Runge-Kutta method, respectively. The effectiveness of the BPTMDI is evaluated through time history response analysis of a 400 m tall case-study building subjected to bidirectional wind loadings. Results show that the BPTMDI can significantly reduce both alongwind and crosswind responses, with reductions of at least 29.75 % in displacement and 48.64 % in acceleration, regardless of wind direction. Furthermore, the BPTMDI demonstrates improved control efficacy compared to BPTMD systems. Lastly, the simplified planar model of the BPTMDI shows basic similarity to the nonlinear planar-spherical model.

Bearing characteristics of mono-column composite bucket foundations for offshore wind turbines in layered soil

The mono-column composite bucket foundation (MCCBF) is a new offshore wind turbine foundation suitable for shallow overburden geology. There are few studies on the bearing capacity and deformation of the new subdivided structure's all-steel MCCBF in layered soil under cyclic loading. This article conducts cyclic bearing characteristics tests on MCCBF in layered soil and shallow overburden layers and studies the ultimate bearing capacity, cumulative rotation angle development rules, and stiffness evolution mechanism. Combined with the finite element analysis results, a calculation method for the ultimate bearing capacity under layered soil is established. The results show that under bidirectional and multidirectional cyclic loading, the ultimate bearing capacity of pure sand changes little, but the strength of clay is reduced, and the ultimate bearing performance decreases. In the clay overlying sand, under high-amplitude cyclic loading, the strength of the sand at the bottom increases, which increases the cumulative angle stiffness and ultimate bearing capacity of the MCCBF. After cyclic loading, the shallow overburden layer will prevent the load from transferring to the deeper soil layer. The foundation will drive the soil in the compartment to slide on the surface of the shallow overburden layer, resulting in a decrease in the load-bearing performance. The initial stiffness of the foundation is increased so that the stiffness change during the cycle is not apparent. Finally, the accuracy of the calculation formula for the ultimate bearing capacity of MCCBF under layered soil is proposed and verified.

Analytical and experimental analysis of guided waves in an aluminum plate under bending load

Although guided waves offer great potential for monitoring various structures, interpreting signals from piezoelectric sensors remains a challenging task. One main reason is the significant influence of environmental conditions on the wave propagation. A lot of research has already been done on the influence of temperature effects and recently more attention has been shifted towards loads. While previous publications have mainly focused on uni- or bi-directional loads, this publication expands the developed models to include bending loads.After reviewing the analytical basis of acoustoelasticity, the derived equations are expanded to nonhomogeneous elastic bending loads using the partial wave method. The analysis is completed using recent results developed by C. Hakoda and C. J. Lissenden (2018) [1], that gave more physical insight in the propagation of guided waves in various frequency-bands.The focus of the experimental analysis is around the fundamental S0- and A0-Modes of Lamb waves. To validate the analytical results an aluminum plate is instrumented using piezoelectric transducers and loaded with varying bending loads. The experimental results are in good agreement with the analytical theory and demonstrate the influence of bending prestress on guided wave propagation. Based on these results an innovative measurement method for bending loads is developed, that is robust to small temperature changes.

Estimating structural response to bidirectional seismic excitation using spectrum compatible motions: Performance of a pair of companion spectra

AbstractBidirectional analyses covering a range of incidence angles for several records are essential yet challenging for routine design. Recent studies have shown that the response to bidirectional shaking may be estimated per straightforward unidirectional analysis in the most preferred orientation in conjunction with the orthogonal combination rules, and this can also remove the need for various incidence angles. Further, it is well known that the mean response can be estimated with reduced dispersion using fewer spectrum‐compatible records. Combining the advantages of both, a pair of companion spectra independent of period and orientation has recently been developed. While the basis of the companion spectra is established therein from a sound mathematical perspective, the applicability of the proposed spectra to real structures may be revisited, especially to structures sensitive to bidirectional interaction, before recommending the companion spectra for practical design. To achieve this end, following a brief scrutiny of the companion spectra, the performance of the same is critically examined for idealized SDoF analogues and real structures such as bridge piers representative of SDoF systems and buildings with asymmetry using single storey and multistorey models (MDoF systems). The results show that the response of the real structures to bidirectional seismic loading can be reasonably estimated with reduced dispersion using fewer records compatible with the pair of the companion spectra. As such, the critical response parameters may be computed by actual bidirectional analyses or by combining responses to unidirectional analyses under fewer spectrum compatible records. Hence, the pair of companion spectra that can be used as “target” to independently match two components of a chosen record is useful for practical design.

A comparative study on the multidirectional piezo-resistive scenario of conventional and auxetic silicone-based sensors coated with graphite powder

The (comparative) study on the multidirectional piezo-resistive scenario of conventional and auxetic sensors is presented using silicone RTV2 as a base material coated with graphite powder as a sensing element. The key parameter of this comparison is the added area that appeared by applying the strain. The larger this parameter is, the larger the area for the sensing elements separation, and subsequently, the greater the sensitivity. To do the sensing performance test in a three-directional mode, a low-cost idea is to use a chuck lathe and an electric motor to open and close the chuck lath cyclically. The available commercial software ABAQUS2021 is used for numerical study. The sensitivity test on conventional and auxetic sensors in different loading modes shows that the performance of the auxetic sensor in unidirectional and bidirectional loading modes is 272% and 130% better than the conventional sensor, respectively. It means that if the added area for the two sensors is closer to each other, the sensory performance of the two sensors will be more similar. Although the sensing performance of the two sensors in the three-directional loading mode is almost equal, the consumed strain energy required to deform the conventional sensor is 30 times more than that of the auxetic one.

Cyclic response of innovative modular joints for modular buildings under bidirectional loading

Based on their dual functions of loading-bearing and energy-dissipating, modular loading-bearing and energy-dissipating joints (MVJ) was used to vertically connect modules, particularly high-rise modular building applications. Fully bolted MVJs can be assembly and disassembly rapidly, and the modules can be recycled after disassembly. Quasi-static tests were conducted on two full-scale space specimens to evaluate seismic resistance properties of the MVJs. Owing to the critical function of MVJs in the buildings, the constant axial loading on the modular column and the vertical displacement on both double beams were implemented simultaneously to simulate the worst loading condition. Owing to the characteristics of double beams under vertical forces, and the requirements of simulation of boundary conditions, a double-beam hinged loading device was proposed. The experimental results demonstrate that the proposed MVJs exhibited great moment capacity. Accordingly, the ratios of the tested average ultimate moment capacity Mu to the designed ultimate moment capacity of double beams MP,beam were 0.828 for S1 and 0.995 for S2. Diagonal cracks occurred on the ends of MVC web for both S1 and S2, indicating that the proposed MVJs were crucial in both loading-bearing and energy-dissipating; the MVC web was used to dissipate energy. Because of the insufficient weld strength between the column and the ceiling beam, as well as the bidirectional cyclic displacement observed at both ends of double beams, the error in the average ultimate moment capacity between the tested and the predicted result is 17.08 %. Analysis conducted on the ductility factor and inter-storey drift ratio demonstrated the feasibility of implementing MVJs in seismic regions.

Static Behavior of UHPC Corner Beam–Column Joint Under Constant Axial and Increasing Bi-Directional Bending Loads

Static Behavior of UHPC Corner Beam–Column Joint Under Constant Axial and Increasing Bi-Directional Bending Loads

Cyclic behavior of carbon steel and austenitic stainless steel hollow laminated viscoelastomer-filled steel tube damper under unidirectional and bidirectional loadings

The hollow laminated viscoelastomer-filled steel tube damper (HLVSTD) is a metallic damper with stable working performance and excellent energy dissipation capability. It can exhibit equal mechanical performance in any single horizontal direction based on the geometric features of the circular shape. However, the impact of carbon steel tube material, stainless steel tube material and bidirectional loading on the mechanical behavior of HLVSTD remains unclear. The objective of this study is to analyze the mechanical performance of HLVSTD under bidirectional loading conditions using carbon steel tubes and austenitic stainless steel tubes, which are commonly utilized in China. Experimental tests were conducted using both unidirectional loading and bidirectional loading to comprehensively assess the performance. The results indicate that, under unidirectional and bidirectional loading, HLVSTDs made from both carbon steel and austenitic stainless steel tubes exhibit stable hysteresis curves. In comparison to the carbon steel tube HLVSTD, the counterpart with an austenitic stainless steel tube demonstrates higher equivalent stiffness, ultimate force, energy dissipation and low-cycle fatigue performance. Moreover, HLVSTDs under bidirectional loading exhibit a similar trend in mechanical performance compared to those under unidirectional loading. Regardless of whether the tube material is carbon steel or austenitic stainless steel, the cumulative displacement and cumulative energy under bidirectional loading were found to be twice as much as those observed under unidirectional loading, which demonstrates the excellent mechanical performance of HLVSTD under bidirectional loading.

Functional failure criterion based on biaxial tensile testing of steel liners and its application to fragility analysis of nuclear containment under overpressure conditions

To investigate the mechanical behavior of the steel liner under bi-directional tensile loading, 39 cruciform tensile specimens made of P265GH steel liner are examined by biaxial tensile tests with different loading ratios. Based on the strength theory of materials and test results, an anisotropic tearing criterion for the steel liner is established. Subsequently, the proposed tearing criterion is applied to the fragility analysis of the containment under overpressure conditions. Finally, the differences between the proposed and existing tearing criteria are discussed. The results show that the strength of the steel liner under biaxial tensile loading is improved, while the deformation capacity is significantly decreased. The proposed tearing criterion is more consistent with the actual behavior of steel liners under bi-directional tensile loading. When evaluating the probabilistic performance of the containment, it is more practical and safer to predict the functional failure of the containment by using the proposed tearing criterion.

Mechanisms and experimental study of directional thermal shock fracture of granite under bidirectional horizontal loading

The study of the mechanism of thermal shock directional fracture of rocks under bidirectional horizontal stress is important for the application of directional thermal shock fracture technology. With the engineering background of the thick igneous roof overlying the coal seam, we conducted high temperature thermal shock directional fracture tests on granite under different horizontal loads to investigate the fracture mechanism. The results show that during the directional thermal shock of granite, the heating rate of borehole surrounding rock experienced three stages of rapid increase, rapid decrease and slowly decrease. AE tests were used to characterize the typical features of rocks during thermal shock fracture: the appearance of macrocracks in the specimen was accompanied by sharp increases in the cumulative AE count and the sudden drops in b-value. The experimental results show that thermal shock can create macroscopic directional fractures within the rock. Within a certain range of horizontal stress difference, the expansion direction of thermal shock cracks could be released locally from geological stress control, i.e. expanding along the direction of the minimum horizontal dominant stress. This provides completely new thinking for the cutting of hard roof and the directional fracturing of rock. In addition, directional thermal shock caused modifications in the distribution of stress in borehole surrounding rocks. We have established a model for stress distribution around the borehole rock and given the calculation formula for the initiation stress of the rock. The studies provide significant theoretical guidance for the industrial application of directional thermal shock fracturing technology.

Life-cycle seismic performance of Q690 steel columns with H-section under various bi-directional cyclic loading paths

The ageing effect in the life-cycle assessment should be considered for the high-strength steel structures constructed in corrosive environments and high-seismicity zones. Additionally, the structures can suffer multi-dimensional seismic excitations because of the spatial effect of ground motions. Therefore, this study aims to investigate the impact of different loading protocols on the mechanical properties of Q690 steel columns with H-section during the whole life-cycle. Firstly, numerical methods considering time-varying corrosion process are used to simulate the ageing steel columns. After that, the nonlinear hysteretic behaviors of the ageing steel columns under different loading protocols are investigated. The factor of resistance degradation (the degree of degradation of ultimate resistance) is employed to quantify the effect of loading protocols on ageing steel columns. Finally, the biaxial ultimate interaction curve considering the ageing effect and a practical design process are proposed. The findings demonstrate that the steel columns exhibit different mechanical properties under various loading protocols, and the coupling direction of bi-directional displacement loads influences the degree of degradation of ultimate resistance. As service time increases, the factor of resistance degradation of steel columns gradually reduces by up to 40%. The proposed biaxial ultimate interaction curve has acceptable accuracy. These findings emphasize the importance of employing the unfavorable loading protocols in conducting the seismic design of the steel columns in different life-cycle stages.

Experimental investigation of physical, mechanical, and thermal behaviour of Bi-directional date palm fiber reinforced epoxy composite

The present study attempts to fabricate lightweight polymer composites with superior physical, mechanical, and insulating properties by vacuum-assisted resin transfer molding (VARTM) technique. This produces bidirectional woven palm fiber epoxy composites with four different fiber loading i.e. 27, 28, 29, and 30 Wt%. The epoxy composite processed with VARTM technique has been characterized by physical, mechanical, and thermal properties along with increasing fiber loading. The test results signified that the mechanical properties including tensile, interlaminar shear, hardness, and impact strength improve with fiber loading. The maximum tensile strength and tensile modulus were observed at a fiber loading of 30 wt%, resulting in values of 64.852 MPa and 3.74 GPa, respectively. The recorded ILSS values for the epoxy composites loaded with 30 wt% were found to be 7.28 MPa. The observed improvements in the mechanical characteristics of the composite produced by the VARTM technology can be attributed to the enhanced interfacial bonding between the matrix and discontinuous prepreg fiber (DPF). The identification of a superior composite, known as DPF-4, was achieved through the incorporation of 30 wt% of bi-directional palm fiber loading. This resulted in notable improvements in the mechanical properties of the composite, as a significant enhancement of 311% and 173% in tensile and impact strength, respectively. These mechanically strengthened epoxy composites could be used as low-grade housing, structural, and automobile component applications.

Cyclic behavior of UHPC corner beam-column joints under bi-directional bending

Design codes contain special provisions for anchorage lengths of flexural reinforcement and amount of transverse reinforcement in beam-column joints, to safeguard against joint failure and possible structural collapse. However, those stipulations could lead to congested joints with construction problems such as segregation. This study leverages experimental testing of eight corner beam-column joints under constant axial and cyclic bi-directional bending loads. In addition to being one of few on corner joints under a complex and practical loading, the study’s main aim is to evaluate the effectiveness of ultra-high-performance concrete (UHPC) as a joint fill in lieu of normal strength concrete (NSC). Brittle failure, either by pure shear or shear combined with yielding of beam reinforcement occurred in all NSC joints and varied in shape and intensity depending on the column depth-to-beam longitudinal bar diameter (hc ⁄db) ratio and spacing of transverse beam/column reinforcement. Ductile failure characterized by the yielding of beam reinforcement and plastic hinge at the beam-joint interface occurred in all UHPC joints and was independent of the two aforementioned variables. The application of UHPC in the joint region resulted in increasing the joint ultimate strength by 27.6–54.8%, energy dissipation by 24–163%, and stiffness by 20 to 50%, compared to NSC joints. Such results were obtained when no transverse reinforcement is used in the joint, and only half transverse reinforcement is used in the beam/column members, and with hc ⁄db relaxed to 38% of the code recommended ratio, highlighting the advantages of UHPC joints. Predictions of ACI-ASCE 352R code were found to be overly unconservative and in need of future improvement.