Effect Of Axial Compression Ratio Research Articles

Effects of axial compression ratio on seismic behavior of shallow‐buried rectangular stations: Hybrid simulation and quasi‐static test

AbstractIn the absence of experimental investigations on column members of underground structures, full‐scale column specimens were tested to explore the seismic behavior of shallow‐buried subway stations at various depths. The axial compression ratios of internal column specimens were set as 0.16, 0.33, and 0.40. Both hybrid simulations and quasi‐static tests were performed on the station columns. The hybrid simulations illustrated the drift demands of internal columns, while the load‐carrying capacity and deformation capacity were obtained from the quasi‐static tests. Hybrid simulations at low, moderate, and high‐intensity levels were conducted to study the seismic responses of shallow‐buried rectangular stations. The hybrid simulations suggest that the most severe damage occurred in the station when the axial compression ratio of the tested column reached 0.40. Central columns suffered severe stiffness deterioration under high‐level earthquake excitation, especially in stations at greater depths. Meanwhile, the quasi‐static test results indicate that the ultimate load of the central columns increases with increasing axial compression, but this leads to a significant decrease in the ductility of columns. Besides, the sectional analysis results show that the central columns are prone to tension‐controlled failure, and the safety margin for flexural response deteriorates with an increasing axial compression ratio. The test results indicate that shallow‐buried rectangular stations are susceptible to flexure‐controlled structural failure when their central columns possess a relatively low axial compression ratio and a high shear span‐to‐depth ratio. The failure mechanism of station columns is revealed by both the hybrid simulations and quasi‐static tests, and the findings from the full‐scale tests are beneficial for the practical design of shallow‐buried rectangular stations.

Experimental and simulation study on seismic performance of steel‐PVA hybrid fiber cementitious composites‐encased CFST

AbstractSix hybrid steel and PVA fiber cementitious composite (S&PFCC)‐encased concrete‐filled steel tube (CFST) columns were designed and fabricated, and the effects of axial compression ratio, core concrete strength grade and steel tube thickness on the seismic performance of composite columns were studied. The test results show that the increase of core concrete strength can obviously improve the bearing capacity and energy dissipation capacity of composite column and can restrain the strain growth rate of steel tube after yielding. Low axial compression ratio and thicker steel tube thickness can improve the overall seismic performance of composite columns. Three calculation methods are modified, and the modified An method can predict the lateral bearing capacity of composite column well. Finally, based on the OpenSees finite element software, the seismic performance of the CFST column wrapped in S&PFCC is simulated to verify the test, and the numerical study shows that the seismic performance of the composite column can be optimized by increasing the steel fiber content, while PVA fiber has a weak effect in the elastic stage, and can effectively improve the ductility of the composite column in the plastic stage.

Experimental study on seismic performance of internal cruciform joints of grouting sleeve connection for modular integrated construction

Modular integrated construction (MiC) adopts room units that integrate maintenance structure, decoration and equipment pipelines in the factory-made modules, resulting in a lack of operating space for connecting modules at the construction site. In the previous research, the joints between modules are usually hinged or semi-rigid connections and partial strength joints. In this paper, a new type of joint with the grouting sleeve connection is proposed to connect modules horizontally and vertically, which is more convenient for construction and does not conflict with interior decoration. Six full-scale cruciform joints were tested to study the effect of axial compression ratio and different structural details. The test results presented the failure mode, stiffness, ductility, and energy dissipation of the specimens. The ultimate inter-story drift ratio is between 4.78 % rad and 5.96 % rad, which is larger than the requirement of 4 % rad in the special moment frame (SMF) system. The horizontal connection plate between modules can cooperate the deformation of left and right beams and columns, and significantly improve the lateral resistance of the joint. The vertical connection between modules did not slip or open and the grouting material is not broken. The inner and outer reinforced plates in the beam-to-column connection can transfer the tensile force of the beam flange well so the outer sleeve does not tear, and the wedge-shaped stiffener can inhibit the cracking of the beam-to-column connection. EC3 Part 1–8 was adopted to evaluate the stiffness characteristic of the proposed connection, indicating that the proposed joint can be classified as rigid joint for the non-sway frame. Finally, the theoretical ultimate resistance of the joint under the ideal failure mode is obtained, which is lower than the test results, indicating that the plastic development of the joint is sufficient and can be classified as full-strength joint.

Study on Joint Connection Performance of an Innovative Tooth Groove Connection and Vertical Reinforcement Lapping in Reserved Hole

In order to explore the horizontal joint connection performance of the innovative tooth groove connection and vertical reinforcement lapping in the reserved hole, five horizontal joint specimens were designed and constructed in this paper. Through the combination of monotonic horizontal load tests and finite element simulation analysis, the effects of axial compression ratio, vertical reinforcement connection degree, reserved hole type, mortar strength, and tooth groove depth on the horizontal joint connection performance of innovative tooth groove connections and vertical reinforcement lapping in reserved holes were comprehensively analyzed and discussed. The results indicated that the specimens were subjected to penetration failure at the tooth groove joint, but the vertical reinforcements and UHPC in reserved holes can effectively transfer the stress, ensuring satisfactory connection performance. With the increase in axial compression ratio and vertical reinforcement connection degree, the joint connection performance enhanced gradually, while the reserved hole type had little effect on the joint connection performance. In addition, it was found that increasing the mortar strength and the tooth groove depth can significantly improve the peak bearing capacity through finite element analysis. Finally, the optimization design suggestions for this innovative tooth groove connection and vertical reinforcement lapping in the reserved hole were given considering factors such as joint connection performance and construction assembly.

Experimental and numerical study on seismic performance of L-shaped multi-cellular CFST frames

Steel-concrete composite frames have been widely used in high-rise buildings. To improve the utilization efficiency of the indoor area, irregular-shaped concrete-filled steel tubular (CFST) columns were proposed for an alternative of the traditional rectangular CFST columns. In this paper, the L-shaped multi-cellular CFST (LM-CFST) frame was proposed, consisting of LM-CFST columns and H-shaped steel beams. Firstly, four LM-CFST frames were tested under combined axial compression and cyclic lateral loads. The local buckling was observed at both the top and bottom ends of the column, and fracture of steel occurred when the drift ratio was large. The hysteresis curves were spindle-shaped with the ductility indexes of 2.61–3.24. Then, a refined finite element model was established and validated against the test results. A parametric analysis was conducted to study the effect of axial compression ratio, web cell length, concrete strength and steel tube thickness on the seismic performance of LM-CFST frames. It was found that the axial compression ratio could affect the seismic performance of LM-CFST frames significantly, while the concrete strength had little effect. Finally, the compression-bending capacities obtained from the sectional analysis method specified in EC4 were compared with those obtained from tests. It was found that this method could predict the compression-bending capacity of the LM-CFST frame under combined axial compression and cyclic lateral loads with reasonable discrepancies.

Research on seismic performance of ITRAC-filled double steel plate composite shear wall

The iron tailings and recycled aggregate concrete(ITRAC)-filled double steel plate composite shear wall (ITRAC-CSW) is a new lateral force-resistant member that applies an optimized cross-sectional form. The ITRAC is recycled concrete produced from 100% solid waste aggregates. Three full-scale ITRAC-CSW specimens were fabricated to investigate the effects of axial compression ratio and shear span ratio on seismic performance by conducting the tests subjected to quasi-static load. The failure mode and the hysteretic performance of the specimens are analyzed. The ITRAC-CSW exhibits good bearing capacity, stiffness, and energy dissipation capacity. This indicates that ITRAC has the potential to replace concrete applications. The numerical simulations and parametric analyses were carried out through the finite element model to reveal the failure mechanism and parameter effects of specimens. Finally, the calculation method for the bearing capacity of ITRAC-CSW was proposed based on the confined strength of the ITRAC. The ratio of the calculated bearing capacity to the test results is between 0.901 and 1.097 and the calculation accuracy is within 10%. This calculation method can be a reference for the performance design of ITRAC-CSW.

Research on the resilience model of a new prefabricated shear wall structure

Based on high-strength bolts, steel plates and other components to achieve the advantages of prefabricated shear wall assembly connection “dry connection” operation advantages, a new type of assembled shear wall with friction energy consumption function was proposed. Using a combination of model tests and numerical simulations, three shear wall specimens with a scaling ratio of 1:1.54 were designed and the corresponding seismic performance tests were carried out. The effects of axial compression ratio and longitudinal reinforcement rate of edge members on the damage mode, hysteresis performance, load carrying capacity, deformation performance, stiffness degradation and energy dissipation capacity of specimens are systematically analyzed. The test results showed that the final failure modes of the three specimens were similar, which was the bending-shear failure from the development of the oblique cracks in the wall to the concrete spalling in the compression zone; The reduction of the axial compression ratio or the reinforcement rate of the longitudinal reinforcement of the edge members will lead to the reduction of the bearing capacity of the shear wall and the increase of the ultimate displacement has a negative impact on the seismic performance of the new assembled shear wall, which is manifested by the weakening of the hysteresis performance and the reduction of the ultimate bearing capacity. Combined with the finite element simulation results, the five-fold skeleton model and restoring force model of the new assembled shear wall were established, and then the calculation formulae of unloading stiffness and loading stiffness of the hysteresis curve were obtained by regression fitting. The restoring force model proposed in this paper is in good agreement with the test results, which can provide a reference for the elastic–plastic seismic response analysis of the new fabricated shear wall structure.

Numerical Analysis on Dynamic Response of CFRP-Wrapped RC Columns under Lateral Impact Loading

This paper presents a numerical study examining the dynamic response and resistance mechanism of reinforced concrete (RC) columns strengthened with or without carbon-fiber-reinforced polymer (CFRP) wraps under lateral impact loading by using the software LS-DYNA. First, the information of eight column models was briefly introduced as part of the laboratory experimental program from the literature. Secondly, finite element (FE) models were established in terms of the geometries of impact tests. Then, a detailed comparison between numerical results and experimental results was made, and FE models showed a relatively high simulation accuracy. Subsequently, a series of parametric analyses were carried out with a focus on the effects of axial compression ratio, the boundary condition at the column top, the layer number of CFRP wraps, and the impact velocity and impact height on the dynamic responses of plain and strengthened columns. The results demonstrated that the CFRP retrofit mechanism was not activated during the initial Stage-I when the impact force rapidly increased to the first peak and then decreased to zero. CFRP strengthening came into play in the second stage, Stage-II, and affected the response of the shear force and moment along the column height, as well as had a great influence on the control of shear damage. The dynamic response of RC columns was more sensitive to the impact velocity than to other parameters, regardless of whether CFRP wrapping was applied. The axial compression ratio would have a different influence on the column failure mode if the impact velocity was varied. The variation in impact height and boundary condition at the column top had little influence on the damage mode of strengthened columns.

Seismic behaviour and modelling of reinforced concrete-filled galvanized corrugated steel tubes

Reinforced concrete-filled galvanized corrugated steel tube, named reinforced CFCST, is an innovative composite member commonly used in seismically active regions and corrosive environments. The seismic behaviour of reinforced CFCST under quasi-static tests had been performed in the past. However, a robust numerical model to simulate the seismic behaviour of reinforced CFCST has not been conducted. This paper proposes a finite element (FE) model capable of simulating the seismic behaviour of reinforced CFCST. The responses of the FE model, in terms of failure modes, hysteretic curves, and local strain distributions, are compared with the corresponding experimental results. Based on the validated FE model, detailed parametric studies have been conducted to investigate the effects of axial compression ratio, length-to-diameter ratio, diameter-to-thickness ratio, steel bar ratio, and material strengths. Finally, simplified design equations capable of predicting the nominal hoop stresses of the corrugated steel tube (CST) and the compression-bending strength of reinforced CFCST are proposed.

Seismic performance of thin-walled steel and concrete composite column-corrugated steel shear wall structure

This paper presents a new structure called cold-formed thin-walled channel steel and concrete composite column-corrugated steel shear wall (referred to as CSC-CSW), which can significantly improve the lateral resistance of SPSW. Three groups of full-length walls were tested under low-cycle reciprocating loading in order to investigate the effects of axial compression ratio and aspect ratio of steel plates. The experiment discovered that the failure of specimens was mainly caused by the tear of corrugated steel plate and the bearing failure of bolt hole. The results show that with the increase of the axial compression ratio, the average peak bearing capacity, ductility and ultimate displacement are decreased. With the decrease of the aspect ratio of the steel plate, the shear capacity and initial stiffness of the specimen are decreased, but the ductility and energy dissipation capacity are improved. On the basis of the test, 19 refined FEA models were established to carry out the multi-parameter analysis. The influence rule of the parameters is revealed and the reasonable value range is given, namely. The thickness of channel steel ranges from 1.5 mm to 2.5 mm, the thickness of corrugated steel plate ranges from 1.5 mm to 2.5 mm and the aspect ratio goes from 0.8 to 1.2, and the axial compression ratio of frame column should not exceed 0.3. Finally, the shear-carrying calculation formula is proposed, and the reliability of the formula is verified by comparing formula calculation results with FEA results, whose maximum error is within 15%.

Numerical study and seismic design of corroded circular RC columns strengthened by C-FRCM

This study aims to numerically investigate the behaviour of corroded circular reinforced concrete (RC) columns strengthened by carbon-fabric-reinforced cementitious matrix (C-FRCM) composites. Three-dimensional finite element (FE) models of the corroded circular RC columns with and without strengthening were set up and validated against previous experimental results. Based on the validated FE models, the parametric studies were carried out to investigate the effects of axial compression ratio, degree of corrosion and layer of carbon fabrics on the behaviour of corroded RC columns under cyclic loading. It shows that the lateral load resistance increased when the axial compression ratio ranged from 0.3 to 0.4, but decreased when the axial compression ratio ranged from 0.4 to 0.6; also the ductility of the corroded RC columns reduced with increasing axial compression ratio. The ultimate capacity of corroded RC columns decreased gradually with the increasing degree of corrosion. Based on the results of parametric studies, equations were developed to estimate the ultimate capacity and displacement of the corroded RC columns repaired by the C-FRCM. The proposed equations can well estimate the ultimate lateral load resisting capacity and ultimate displacement of the corroded circular RC columns strengthened by C-FRCM.

Analysis on Experimental Performance of Hysteretic Behavior of Concrete-Filled Circular CFRP Steel Tubular Beam-Column

In order to study the test performance of the concrete-filled CFRP steel tubular (CF-CFRP-ST) beam-column under hysteretic load, 12 specimens were designed. During the test loading, the effects of axial compression ratio and longitudinal CFRP reinforcement coefficient on hysteric load were studied. Based on experimental research, a finite element method for establishing CF-CFRP-ST beam-column is proposed by FE simulation, and the influence of main parameters on performance is studied by this method. The test results show that CFRP and the steel tube can work together well, and the local buckling of specimens is delayed. In addition, the simulation results are in good agreement with the experimental results. Based on the experiment and finite element method, the influence of main parameters on the hysteretic behavior of specimens is studied.

Effect of Axial Compression Ratio on Seismic and Self‐Centering Performance of Unbonded Prestressed Concrete Columns

To explore the influence of the applied axial compression ratio and preloaded axial compression ratio on the seismic performance of unbonded prestressed concrete columns, pseudo‐static tests were carried out on four prestressed columns and one ordinary column in this study. The seismic performance indexes of test columns were studied and analyzed, including failure modes, hysteresis curves, skeleton curves, stiffness, ductility, and energy dissipation. The test results show that compared with concrete columns with ordinary reinforcement, the hysteresis curve of reinforced concrete columns with prestressed tendons has a pinch phenomenon to a certain extent, and the energy dissipation performance becomes worse. For the prestressed columns, the greater the applied axial compression ratio, the worse the fullness of hysteresis curves and the energy dissipation performance, the greater the residual displacement, the faster the strength attenuation, and the worse the self‐centering performance. For the posttensioned unbonded prestressed concrete columns, the greater the preloaded axial compression ratio, the worse the energy dissipation performance of the test column, the slower the strength attenuation, and the better the self‐centering performance.

Seismic performance of grid tubular-double steel plate concrete composite shear wall

Experimental study and numerical analysis on the seismic performance of grid tubular-double steel plate (GDSP) concrete composite shear wall subjected to low reversed cyclic loading were carried out in this paper. The effects of axial compression ratio, shear-span ratio, ending-configuration, strength of steel and concrete, length-to-width ratio and aspect ratio of cavity on the seismic performance of GDSP concrete composite shear wall, in terms of hysteresis curve, skeleton curve and failure mode, were investigated. The results show that the GDSP concrete composite shear wall exhibits excellent seismic performance with plump hysteresis curve, high bearing capacity and ductility. With the increase of axial compression ratio, the peak load of GDSP concrete composite shear wall increases, but the ductility decreases gradually. The numerical analysis results are consistent with the results tested. The infilled-concrete is confined by steel plates in three directions, and concrete compressive strength and ductility are significantly enhanced. The concrete sustains the compression together with steel plate, which prevents the outer double steel plate from buckling failure under compression. The length-width ratio of cavity affects the three-dimensional confine effect of the infilled-concrete. It is recommended that the length-width ratio of the end cavity take between 1.0–1.5 and the length to width ratio of the middle cavity set as 1.5–2.0. The single channel steel set at the side of the wall can significantly enhance the bearing capacity and deformation capacity.

Experimental investigation on fire resistance of sandwich composite walls with truss connectors

The sandwich composite wall with truss connectors is a new type of double-steel-plate composite wall, which consists of two external steel plates, square steel tubes at both ends, and in-fill concrete. The external steel plates are constrained by the steel trusses, thereby possessing superior mechanical performance. In order to study the fire resistance of the sandwich composite wall, 4 full-scaled walls were tested under one-side ISO-834 standard fire, aiming to investigate the effects of axial compression ratio, truss spacing to thickness ratio, and steel plate thickness on the fire resistance of the walls. The temperature, axial displacement and transverse displacement of key parts of the walls were measured. Experimental results indicate that, the walls could maintain sufficient load-bearing capacity as specified by the Class I fire resistance rating of Chinese Code. The fire endurance of the wall was controlled by its thermal insulation. The deformation pattern of the walls under the fire was overall deflection toward the unexposed surface, and the steel plate exposed to the fire experienced obvious local buckling. The axial compression ratio and the truss spacing to thickness ratio had great effects on the deformation behavior of the walls. When the axial compression ratio was reduced from 0.5 to 0.3, the axial deformation of the wall was changed from compression-predominant to expansion-predominant deformation. A larger truss spacing to thickness ratio led to more obvious buckling of the steel plate exposed to the fire. It is recommended to restrict the truss spacing to thickness ratio of the wall in engineering design.

Shear mechanism and capacity calculation on SRC special-shaped joints

In this paper, 15 specimens of steel reinforced concrete (SRC) joints were tested under horizontal cyclic loading. The failure modes of different types of SRC special-shaped joints, and the shear mechanism and capacity of the joint were analyzed. The effects of axial compression ratio, dislocation height of the beam, the sectional height difference of beams, the sectional height difference of columns, the inclination angle of leaning beams and other factors on the shear bearing capacity of joints were studied. Furthermore, based on the experimental study, the finite element analysis (FEA) method was used to verify the experiment, and 14 finite element models (FEMs) were established for parameter analysis. The results indicate that the shear capacity of the joints was mainly borne by webs, stirrups and concrete inclined-compression-struts. Ultimately, the shear mechanism analysis model of SRC special-shaped joints was proposed, and the shear capacity calculation formulas of SRC special-shaped interior joints, variable-column exterior joints and leaning beam-column exterior joints were established. The proposed shear capacity calculation formulas can be adopted to assess the shear capacity of SRC special-shaped joints.

Seismic behavior of PVC-CFRP confined reinforced concrete columns: An experimental study

This paper presents an experimental study on the seismic behavior of PVC-CFRP confined reinforced concrete columns subjected to combined axial compression load and horizontal reversed cyclic loading. A total of six one-fourth scale PVC-CFRP confined reinforced concrete columns (PVC-CFRP) and two one-fourth scale PVC confined reinforced concrete columns (PVC) are fabricated. The flexural failure mode, which is characterized by the crushing of concrete and the yielding of longitudinal reinforcement, is found for all PVC-CFRP and PVC specimens. The effects of axial compression ratio and CFRP strip spacing on the secant stiffness, energy dissipation, etc. are investigated. The results show the secant stiffness decreases rapidly as the axial compression ratio increases, and the confining effect of the CFRP strip spacing on the secant stiffness evolution is more obvious for the specimen with higher axial compression ratio. The specimen with smaller CFRP strip spacing exhibits better energy dissipation capacity, and the strengthening effect of CFRP strips is more significant for the specimen with higher axial compression ratio. The effective CFRP strip spacing for the PVC-CFRP is suggested.

Experimental study on seismic performance of precast hollow shear walls

SummaryThis paper puts forward a new type of the precast hollow shear wall. Focusing on seismic performance, the low‐frequency cyclic loading tests of five precast specimens and two cast‐in‐situ specimens in full size are conducted for comparison. The yielding and failure mechanism of specimens are analyzed and compared. The reliability of the vertical connection of precast hollow shear wall structure under the seismic effect is studied. The effects of axial compression ratio, single reinforcement connection in the central part, and confined stirrup for lapped reinforcements in boundary elements are also tested through experiments. The result shows that the failure mechanism of the precast specimen is basically same as the cast‐in‐situ specimen. The hysteretic curve of the precast specimen is plumper. And the energy dissipation capacity of precast specimen is superior to that of cast‐in‐situ specimen. In addition, the experimental data show that the buckled stirrup encryption for lapped steel in boundary elements will not increase the seismic performance of the proposed precast specimen. On the whole, the seismic performance of the proposed precast hollow shear wall can meet the safety requirements. Hence, it can be used in actual engineering project replacing cast‐in‐situ shear wall.

Study on the seismic performance of high-performance polypropylene fiber-reinforced lightweight aggregate concrete columns

Seven specimens of high-performance polypropylene fiber-reinforced lightweight aggregate concrete (HPPLWC) columns and three specimens of lightweight aggregate concrete (LWAC) columns were tested under low cycle reciprocating loading to study the seismic behavior of HPPLWC columns. The effects of axial compression ratio, stirrup ratio and high-performance polypropylene fiber (HPPF) content on the seismic behavior of LWC columns were studied. The effectiveness of HPPFs to supersede stirrups under earthquake was also discussed. Through the study of the failure phenomenon, hysteretic curve, ductility, energy dissipation, stiffness degradation, shear capacity, and other test results, it was found that: The additional HPPF could effectively inhibit the development of cracks and ameliorate the failure mode of specimens. The enhancement effect of HPPF on ductility and energy dissipation of specimens was much higher than that of increasing stirrup ratio. The calculated value of shear capacity formula given by NZS3101 in New Zealand was in good agreement with the experimental results, providing a reference for the supplement and perfection of the LWAC code formula. The low stirrup ratio HPPLWC specimens and the high stirrup ratio LWAC specimens were similar to the seismic performance. Therefore, HPPFs could effectively supersede some stirrups in the seismic application of complex structures.

Experimental investigation of full-scale concrete columns confined by high-strength transverse reinforcement subjected to lateral cyclic loading

The use of high-strength longitudinal and transverse reinforcements in confined concrete columns can improve bearing capacity and deformability. Besides, experiments on confined concrete columns with side length of 400 mm can better reflect the behaviour of confined concrete columns in engineering project. Thus, the purpose of this study is to investigate the seismic behaviour of full-scale confined concrete columns with high-strength longitudinal and transverse reinforcements. Based on 15 confined concrete columns subjected to lateral cyclic loading, the effects of axial compression ratio, shear span ratio and volumetric ratio on the seismic behaviour of confined concrete columns were studied. The results showed that the ultimate drift ratios of the 15 confined concrete columns ranged from 1/43 to 1/20, i.e. 1.2–2.5 times as much as the specified limit (1/50) of rate earthquake, indicating excellent ductility. Additionally, the high-strength transverse reinforcements could not yield at peak load but could yield at the ultimate displacement. The high-strength transverse reinforcement stresses at the peak lateral load were 430–690 MPa, approximately 56–91% of the transverse reinforcement yield strength. Finally, an empirical formula was proposed to predict the ductility factor that was then evaluated by comparing the predicted values with the experimental results of 37 confined concrete columns.