Bidirectional Lateral Loading Research Articles

Performance evaluation of steel hollow box piers under bidirectional lateral cyclic loading to enhance the existing seismic verification framework

This study comprehensively evaluates the lateral performance and behaviour of stiffened steel hollow box piers under axial and lateral cyclic bidirectional loading using Finite Element (FE) analysis to develop a reliable performance-based seismic verification framework. In the first phase of the analysis, various bidirectional lateral loading patterns are examined to identify the pier's worst inelastic behaviour regarding strength, ductility, energy absorption, and failure patterns. Among these loading patterns, it was found that the circular-shaped bidirectional lateral cyclic loading (BICI) yielded the worst inelastic behaviour of the pier. Then, in phase two, an extensive comparative parametric study was conducted between the BICI and unidirectional loading pattern to evaluate the significance of important design parameters on lateral performance. Results revealed that the width-to-thickness ratio Rf, slenderness ratio λ¯ and axial load P showed significant influence under both the load patterns, whereas the modified stiffener's slenderness ratio λs′, and aspect ratio α showed more significant influence only under the BICI load pattern. Subsequently, the existing formulae proposed by authors for predicting strength and ductility under unidirectional lateral loading were reviewed and modified to incorporate the bidirectional effect. Moreover, a novel set of formulae was proposed for the BICI load pattern. Finally, an enhanced performance-based seismic verification method was developed by examining the relationship between the ductility factors of steel hollow piers under both BICI and unidirectional loading patterns. This method integrates the bidirectional effect into the existing unidirectional framework, enabling a comprehensive assessment of the piers' performance and enhancing seismic resilience.

Seismic behavior of RC-SMF and IMF corner beam–column connections subjected to unidirectional and bidirectional lateral loads

Failure of beam–column connections can lead to partial and complete building collapse during severe earthquakes. Corner beam–column connections may be more vulnerable during earthquakes because they must withstand bidirectional loading transferred from nearby beams and columns. Furthermore, horizontal torsion exacerbates the damage to corner beam–column connections compared with other components. The objective of this study is to explore the seismic performance of corner beam–column connections in reinforced concrete intermediate moment frames (IMFs) and special moment frames (SMFs). Four full-scale beam–column connection specimens are fabricated and tested under two different loading types (unidirectional and bidirectional loading). It is observed that the strength and deformation capacity of the specimens were strongly affected by the type of loading (unidirectional and bidirectional lateral loading) and the reinforcement details (SMF, IMF). All corner connection specimens failed by joint shear failure irrespective of loading type and reinforcement detail.

Multi-axial cyclic loading tests for RC shear walls of nuclear power plant structures

Reinforced concrete (RC) walls have been widely studied through experimental testing. A great number of these existing studies considered only the in-plane loading cases, ignoring the out-of-plane loading effect on the in-plane structural response, although earthquake ground motions have multi-axis loading components. Some recent studies addressed the bidirectional loading effect on RC walls, and reported that the out-of-plane loading lowers the displacement capacity of RC walls. However, these studies are for flexural response of RC walls, and little experimental data for shear response of RC walls under bidirectional lateral loading is available. In this study, a series of cyclic loading tests were conducted to investigate the effect of multi-axial loading on the in-plane shear response of RC walls. A prototype nuclear power plant structure was selected, and a part of the prototype RC wall was manufactured as a test specimen, which was designed to have shear failure. Out of the five wall specimens manufactured for this study, two specimens were subjected to the same unidirectional lateral loading with different axial forces to investigate the effect of axial force on the wall response. Remaining three specimens were subjected to bidirectional lateral loading with different loading protocols. It was found that both out-of-plane loading and axial force can substantially impact on the in-plane shear strength and displacement capacity of RC walls.

Predictive model for bidirectional shear strength of reinforced concrete columns subjected to biaxial cyclic loading

Corner columns are subjected to bidirectional lateral loading in three-dimensional framed structures during seismic events, which can deteriorate their shear strength. The majority of the design codes do not consider the effect of biaxial lateral loading in the calculation of the column shear strength, and hence an accurate formulation that can predict the bidirectional shear strength is still lacking. Gene Expression Programming (GEP) was used in this research to predict the bidirectional shear strength of columns subjected to biaxial cyclic loads based on a database collected from different experimental studies found in the literature. Based on the previous experimental studies, it is found that the biaxial shear strength of RC columns are predominantly controlled by the column axial load, cross-sectional area of the columns, column shear reinforcement area, concrete compressive strength, and the height of the column. These parameters were used to develop the GEP models in this research. The models were statistically evaluated in order to ensure their applicability, and then they were compared to the ACI-318 formulation of the uniaxial shear strength. The R2 value obtained using the ACI-318 formulations is low compared to that obtained using the GEP models, where the R2 value obtained using the ACI formulation is 0.35, and that obtained using the first and second GEP models are 0.87 and 0.73, respectively. This confirms that the GEP models are more fitting to the experimental results compared to the ACI-318 formulation.

Axial Load Variation of Columns in Symmetrical RC Buildings Subject to Bidirectional Lateral Actions in Regions of Low to Moderate Seismicity

ABSTRACT Columns in building frame systems are subjected to the combined action of bidirectional horizontal loading and axial load variation during an earthquake. Whilst the behaviour of RC columns under unidirectional and bidirectional lateral loading with constant axial load is understood well, the behaviour under bidirectional lateral loading with axial load variation is rarely studied, especially for limited ductile RC columns prevalent in regions of low to moderate seismicity. This paper begins with a numerical study that aims to obtain the generalised patterns and range of axial load variation in RC building columns. To this end, a case study building is subjected to a suite of 15 ground motions, representative of low to moderate seismic regions, in OpenSees. This is followed by an experimental study in which limited ductile high-strength RC columns are tested under bidirectional lateral loading and two different axial load variation protocols, namely synchronous and nonsynchronous variable axial loading protocols. The results of the numerical study demonstrated that axial load variation of the columns in an RC building is primarily dependent on the response spectral acceleration corresponding to the fundamental period of the structure in the two orthogonal horizontal directions and/or the vertical direction. The results of the experimental testing showed that nonsynchronous axial loading (compared to constant and synchronous axial loading) results in the lowest collapse drift capacity and energy dissipation of the RC columns.

Bidirectional Lateral Loading of RC Columns with Short Lap Splices

Bidirectional Lateral Loading of RC Columns with Short Lap Splices

Steel Columns under Multi-Axis Seismic Loading: Experimental Findings and Design Recommendations

This paper summarizes the findings of two test programs that investigated the hysteretic behavior of wide-flange columns in steel moment-resisting frames. Both deep and shallow steel columns were examined. The members were subjected to unidirectional and bidirectional lateral loading histories coupled with constant and varying axial load demands. The experimental findings highlight the dependence of the steel column response on the member end boundary conditions, the biaxial bending, the loading history, as well as the test-scaling. Steel columns subjected to high axial load demands do not behave as force-controlled elements as suggested by current nonlinear modeling recommendations in North America. Accordingly, an updated axial force limit is proposed in this case. Moreover, in light of the test findings, seismic design recommendations are proposed to limit column damage during strong earthquake shaking.

Earthquake resistance of reinforced concrete corner beam-column joints with different column axial loads under bi-directional lateral loading

The seismic performance of a corner beam-column joint in reinforced concrete frames was studied by testing two three-dimensional corner beam-column subassemblage specimens without slabs under constant column axial load and bi-directional lateral cyclic load reversals. The column-to-beam flexural strength ratio was varied from 1.4 to 2.3 by changing the magnitude of column axial load. Although a sufficient margin to prevent shear failure was provided to a corner beam-column joint in the test, the subassemblage specimens failed in joint hinging after beam and column longitudinal bars and joint hoops yielded. The ultimate joint hinging capacity of a corner joint under bi-directional lateral loading was enhanced by an increase in column compressive axial load, and can be estimated based on the new mechanism proposed by Kusuhara and Shiohara.

Simulation of Seismic Behavior for RC Columns under Bidirectional Compression-Bending

To investigate the seismic behavior of RC columns under bidirectional lateral loading, numerical analysis for tests of RC columns under biaxial loading were performed using fiber model. The simulation results agreed well with test results. The effect of axial compression ratio on the seismic behavior of RC columns under biaxial lateral load was analyzed. The analytical results showed that biaxial lateral loading had little effect on critical axial compression ratio, and the value of critical axial compression ratio was between 0.4~0.5. Bevel carrying capacity under bidirectional lateral loading was a little greater than that under principal axial loading when axial compression ratio was less than 0.1. There had been about 10 percent decrease in bevel carrying capacity at critical axial compression ratio but principal axial bearing capacity declined about 35 percent. Moreover, ultimate displacement angle and accumulative hysteretic dissipation energy decreased observably with increase of axial compression ratio. The adverse influence of special effect on principal axis should be considered in the actual design.

이축반복하중을 받는 2주형 철근콘크리트 교각의 실험거동

Response of reinforced concrete (RC) column-bent piers subjected to bidirectional seismic loadings was experimentally investigated. RC column-bent piers represent one of the most popular shapes of piers used in Korea highway bridges. Four column-bent piers were constructed in 400 mm diameter and 2,000 mm height. Each pier has two circular supporting columns. These piers were tested under bidirectional lateral load reversals with an axial load of . The test parameters included : different transverse reinforcement contents and lap-spliced longitudinal reinforcing steels. Test results indicate that the lap splice of longitudinal reinforcing steels have significantly influenced on hysteretic response of column-bent piers similar to previous test results for single columns with corresponding test parameters. Column capacity was changed with the level of transverse confinement. From the comparison of test result for single column under unidirectional loading, the damage of single column was concentrated on lower plastic hinge region but the damage of column-bent piers was scattered to upper and lower plastic hinge region.

이축방향 유사정적 실험에 의한 이주형 철근콘크리트 원형 교각의 내진 성능평가

A RC column-bent pier represents one of the most popular piers used in highway bridges. Seismic performance of reinforced concrete (RC) column-bent piers under bidirectional seismic loadings was experimentally investigated. Six column bent-piers were constructed with two circular supporting columns which were made in 400 mm diameter and 2,000 mm height. One single column specimen was additionally made to comparatively evaluate the seismic response of RC column-bent piers. Test parameters are different transverse reinforcement and loading pattern. These piers were tested under lateral load reversals with the axial load of . Three specimens were subjected to bidirectional lateral load cycles which consisted of two main longitudinal loads and two sub transverse loads in one load cycle. Other three specimens were loaded in the opposite way. Test results indicated that lateral strength and ductility of the latter three specimens were generally bigger than those of the former three specimens. Plastic hinges were formed with the spall of cover concrete and the fracture of the longitudinal reinforcing steels in the bottom plastic hinge of two supporting columns for the former three specimens. Similar behavior was observed in the top and bottom parts of two supporting columns for the latter three specimens.

Multi-spring model for 3-dimensional analysis of RC members

A practical multi-spring model is proposed for a nonlinear analysis of reinforced concrete members, especially columns, taking into account the interaction of axial load and bi-directional bending moment. The parameters of the model are determined on the basis of material properties and section geometry. The axial force-moment interaction curve of reinforced concrete sections predicted by the model was shown to agree well with those obtained by the flexural analysis utilizing realistic stress-strain relations of materials. The reliability of the model was also examined with respect to the test of reinforced concrete columns subjected to varying axial load and bi-directional lateral load reversals. The analytical results agreed well with the experiment.