Study on Interaction of RC Pile-Soil with High Reinforcement Ratio of Integral Abutment Bridges under Quasi-Static Test

In order to improve the ability of the reinforcement concrete (RC) pile foundation of integral abutment to absorb the horizontal reciprocating deformation under the action of temperature or earthquake, a pseudo-static low cycle test on interaction of pile-soil with high reinforcement ratio was carried out. The failure location, hysteresis curve, skeleton curve and horizontal deformation of three piles with different reinforcement ratios were compared. The test results show that, with the increase of the reinforcement ratio, the crack of the RC pile develops along the pile body to the depth, and the pile body failure area and the position where the maximum bending moment moves down, the crack resistance of the pile body is improved, and the effective interaction pile length increases; The test results also show that the hysteresis curve of the model pile becomes fuller with the increase of the reinforcement ratio, compared with the RCP-1 specimen with the lowest reinforcement ratio, the equivalent viscous damping ratio of the RCP-3 specimen is increased by 31.6%, and the energy dissipation capacity is improved. In addition, with the increase of the reinforcement ratio, the bearing capacity and deformation capacity of model piles are greatly improved. Compared with RCP-1 specimen, the ultimate bearing capacity of RCP-3 specimen increased by 150%, and the corresponding ultimate displacement increased by 153%. Increasing reinforcement ratio can significantly improve the mechanical properties and deformation capacity of RC pile.

A Restoring Force Model for Prefabricated Concrete Shear Walls with Built-In Steel Sections

Prefabricated shear walls have been widely used in engineering structures. Vertical connection joints of the walls are the key to ensure the safety of the structures. Steel–concrete composite structures have been proved to have a good bearing capacity and ductility. In this paper, a new type of prefabricated structure is proposed, in which vertical wall members are connected together through built-in steel sections and cast-in-place concrete. This paper studies the seismic performance of the proposed prefabricated concrete shear wall structure. Hysteretic curves and skeleton curves of the shear wall are obtained based on experimental analyses. A dimensionless skeleton curve model is developed using the theory of material mechanics and the method of regression analysis. A stiffness calculation method for different loading stages is obtained and a restoring force model is proposed. The proposed innovative prefabricated shear wall structure provides good resistance to seismic performance and the related analysis provides a fundamental reference for studies of prefabricated shear wall structures.

Experimental and Finite Element Analysis of External ALC Panel Steel Frames with New Semi-Rigid Connector

In this paper, a new ALC panel connector was proposed. It has a good engineering economy and high fault tolerance. A quasistatic loading experiment was carried out to verify the feasibility of the external ALC panel steel frame under seismic loading. The test phenomena, hysteretic curve, skeleton curve, stiffness degradation, and energy dissipation of two sets of full-scale specimens were analyzed and discussed. Moreover, the simulation of pendulous Z-panel connectors with different thicknesses was carried out using ABAQUS software. The comparison reveals that the semi-rigid connection has a full hysteresis curve, good energy dissipation capacity, and a 15% increase in peak load capacity. Finally, similar results for different thicknesses in the use of pendulous Z-panel connectors reveal that using the 6 mm connector may be the most economical solution for engineering.

Experimental Study On Hysteretic Behavior of Concrete Filled Square CFRP Steel Tubular Beam-Column

In order to study the hysteretic behavior of concrete filled square CFRP steel tubular Beam-Column under different influence factors, 12 specimens were designed, and the failure mode, middle section lateral force-deflection(P-Δ) curve, middle section bending moment-curvature(M-φ) curve and middle section deflection-deformation(Δ−Δ') curve were studied. Axial compression ratio and longitudinal CFRP reinforcement coefficient as influencing factors, the effects of axial compression ratio and longitudinal CFRP reinforcement coefficient on P-Δ skeleton curve, M-φ skeleton curve, strength and stiffness degradation, ductility, cumulative energy consumption and other indexes were studied; the P-Δ curve and deformation mode of the specimens were simulated by ABAQUS, and the effects of axial compression ratio, slenderness ratio and other main parameters on the hysteretic performance of the members were studied. The test results show that CFRP has good lateral restraint and longitudinal reinforcement effect on CFST, and the local buckling of CFST is delayed. The P-Δ curve and M-φ curve of all specimens are full. In addition, the steel tube and CFRP have good synergy in both longitudinal and transverse directions. The change of axial compression ratio and longitudinal CFRP reinforcement coefficient has no significant effect on the strength degradation. The increase of axial compression ratio and longitudinal CFRP reinforcement coefficient can improve the flexural capacity and stiffness of the specimens, and slow down the stiffness degradation, but reduce the ductility and cumulative energy consumption of the specimens. The finite element software ABAQUS is used to simulate the P-Δ curve and deformation mode of specimens. It is found that the simulation results are in good agreement with the experimental results. Based on the model analysis of the main parameters, it is found that the increase of steel yield strength and CFRP layers can improve the bearing capacity of the specimens, and the axial compression ratio has the most significant effect on the specimens.

Restoring Force Model Research on Joint of Circular Tubed Steel-Reinforced Concrete Column

In this paper, two joints of circular tubed steel-reinforced concrete (CTSRC) column were designed. The load-displacement hysteretic curve and skeleton curve of this new type of joint are obtained by the pseudostatic test under low cycle cyclic load on the top of the column. The results show that this new type of joint has good seismic energy dissipation performance. On the basis of the test, a three-fold skeleton curve model considering three characteristic points of yield, limit, and failure is proposed, and the expression of skeleton curve model is given. The load and unload stiffness degradation law of specimens under reciprocating load is studied, and the expression of stiffness degradation law is given. The hysteresis law of the new type joint specimens is described in detail. The validity of the model is verified by comparing the experimental curve with the model curve. The model can be used in the elastic-plastic seismic time-history analysis on the joint of circular tubed steel-reinforced concrete (CTSRC) column.

Seismic Resistance Properties of Improved Dry-Type Beam-Column Joint: An Experimental Research

Dry-type joints are an advanced type of sustainable beam-column connection mode used in the prefabricated concrete frame structural system. This paper proposed an improvement scheme for high-strength bolt dry-type joints and designed a new type of common bolt dry-type joints. A pseudo test involving low-cycle repeated loading is conducted to assess the seismic resistance properties of new joints including damage mode, hysteretic curve, skeleton curve, and ductility factor. Numerical simulation is applied to validate the rationality of experimental results. It is found that when the bending capacity of the end block of the beam is consistent with that of the bolt, the deformation of the bolt will no longer increase greatly after a period of large deformation; at this period, the bolt does not fully enter the plastic stage, but at this time, the end block of the beam begins to appear large cracks and enter the plastic deformation and has good energy dissipation performance.

Research on seismic stability of reinforced concrete frame structure based on numerical simulation

BACKGROUND: The analysis of seismic stability of structure is important in the field of engineering. OBJECTIVE: This study aims to verify the reliability of numerical simulation in seismic stability of reinforced concrete (RC) frame structure. METHODS: Based on the numerical simulation, the material constitutive model of RC frame structure was introduced and then a finite element model was established through ABAQUS to analyze its seismic stability. RESULTS: The simulation results of ABAQUS were similar to the test values, the tangent slope of the skeleton curve of the structure decreased gradually, the interstorey displacement of storey 1 was the largest, the maximum error of the interstorey displacement angle was 0.005, and the ductility coefficient was 4. CONCLUSIONS: The experimental results verify the reliability of the numerical simulation method and provide some theoretical support for its better application in the study of seismic stability.

Experimental Investigation of the Mechanical Behaviour of Wall–Beam–Strut Joints for Prefabricated Underground Construction

Prefabricated construction is becoming increasingly prevalent, however, it is rarely applied in underground constructions, except for tunnel linings, due to the difficulties that arise in jointing various prefabricated components in underground conditions. To solve the vertical location problem of embedded mechanical couplers during the construction of wall–beam–strut joints for a prefabricated metro station, a new connection using welded steel plates is proposed. In this paper, four full-scale specimens of wall–beam–strut joints connected using welded steel plates and mechanical couplers were experimentally tested under monotonic and low-reversed cyclic loading conditions. The testing results were analysed in terms of the ultimate bearing capacity, failure mode, hysteresis, skeleton curve, stiffness degradation, energy dissipation and strain of the reinforcement bars. Notably, the two kinds of joints had similar ultimate bearing capacities and failure modes, but the crack distributions on the tops of the waler beams were different. For the specimens with the welded steel plate connection, tensile horizontal cracks first appeared on the top surface of the beam, where the welded steel plate was located, and then coalesced gradually; however, this cracking pattern was not observed during the experimental test of the specimens connected with the mechanical couplers. Furthermore, it was determined that the energy dissipation and ductility of the welded steel plate connection were better than those of the mechanical coupler connected joint, because the steel plate could redistribute the internal force in the joint and increase the stiffness. It was concluded that the proposed welded steel plate connection could be more favourable than the mechanical coupler connection in the construction of a prefabricated metro station in Guangzhou. Moreover, the results obtained from these experiments could provide guidelines for the corresponding connections employed in underground-prefabricated structures.

Hysteresis Properties of Corroded High Strength Steel

In order to study the effects of corrosion damage on the hysteresis properties of high strength steel (HSS), dry-wet cycle corrosion tests were conducted on Q690D steel to obtain 6 batches of corroded specimens, and cyclic loading tests were performed on them to analyse the degradation law of hysteresis curve, skeleton curve and hysteretic energy, and then establish the hysteresis constitutive model of corroded HSS steel. Results indicated that although the hysteresis curves of corroded specimens are still smooth and full, corrosion damage would result in the continuous decrease of peak stress, and lead to the linear reduction of hysteresis energy. Besides, the cyclic hardening coefficient K’ and cyclic hardening index n’ of HSS would also decrease linearly with corrosion degree. Based on these experimental results, a new hysteresis constitutive model for corroded HSS steel was proposed, and its validity was verified.