Recycled Concrete Columns Research Articles

Seismic performance of structures composed of T-shaped and L-shaped recycled concrete columns and lightweight infill walls

ABSTRACT In this paper, a structure composed of a T- or L-shaped recycled concrete column frame (RCCF) and lightweight infill wall (LIW) with a herringbone brace has been proposed to investigate its seismic behavior. Two T-shaped and two L-shaped full-size experimental models of the structure have been built and tested under low-cyclic loading conditions. Consequently, bearing capacity, stiffness, ductility, hysteretic behavior, energy dissipation, and failure characteristics of each test specimen have been analyzed, identifying structure parts prone to damage and failure, understanding their yield mechanisms, and lastly providing constructive recommendations for the structural design. Studies show that the bearing capacity, ductility, and comprehensive seismic behavior of T- or L-shaped lattice-reinforced RCCF-LIW structures with a herringbone brace have been significantly improved. For the engineering practice, it is necessary to strengthen the performance of the herringbone brace-frame beam joint.

Research on Axial Compression Performance of Waste Fiber Recycled Concrete Column

In order to investigate the compressive performance of waste fiber recycled concrete(WFRC) columns under axial compression, this paper used ABAQUS finite element software(FEM) to establish 8 models of WFRC columns, taking the length of waste fibers, volume of waste fibers and replacement rate of recycled aggregate as variables. The lateral deformation in midspan and stiffness of specimens under axial compression were analyzed and compared with experimental data. The results showed that the strain curves of WFRC specimens analyzed by ABAQUS software were very consistent with those obtained by experiments, and the results were basically the same. The ductility was changed by the incorporation of waste fibers, and when the length of waste fibers was 19 mm and the volume of fibers was 0.12%, the ductility of WFRC column was the best.

Cyclic loading tests and shear strength of composite joints with steel-reinforced recycled concrete columns and steel beams

Cyclic loading tests were conducted for eight composite joints (five interior joints and three exterior joints) with steel-reinforced recycled concrete (SRRC) columns and steel beams under cyclic loading. The axial compression ratio and recycled coarse aggregate (RCA) replacement percentage were considered as the main design parameters for the above composite joints. The failure process, failure modes, hysteresis loops, skeleton curves, stiffness degradation, storey drift ratio, bearing capacity, ductility and energy dissipation capacity of the joints were presented and analysed in detail. The influence of the design parameters on the mechanical performance of the composite joints under cyclic loading was also investigated. Results showed that the cracking loads of the joints increased with the increase of axial compression ratio. Typical shear failure was the failure mode. The spindle-shaped hysteresis loops of the joints, the ductility coefficients, the elastic-plastic storey drift ratios and the equivalent viscous damping coefficients indicated a relatively good seismic performance. The bearing capacity and stiffness of the joints decreased gradually, while the ductility and energy dissipation capacity of the joints decreased slightly with an increase in the RCA replacement percentage. Additionally, the stiffness degradation of the composite joints accelerated and the energy dissipation capacity and ductility reduced evidently with an increase in the axial compression ratio. Finally, a comparative analysis of each shear strength formula was conducted. The result showed that the formulas of ASCE, AIJ and JGJ138-2001 could predict the shear strength of the joints accurately. This validation indicated that the existing methods are applicable to this group of composite joints.

Performance of fly ash incorporated recycled aggregates concrete column under axial compression: Experimental and numerical study

The reinforcing steel properties and concrete constituents such as binder materials as well as type and geometry of coarse aggregates influence performance of a reinforced concrete column under uniaxial compression. This paper investigates full-scale reinforced concrete (RC) column specimens comprising 100% recycled coarse aggregates and fly ash as partial replacement of cement. Two cement replacement ratios such as 20% (FA20RAC) and 30% (FA30RAC) are considered. Particle packing method is used for proportioning of concrete. This mix design method leads to dense packing with minimized voids in fly ash incorporated recycled aggregate concrete (FARAC) mix requiring less fresh binder content. As compared to natural aggregate concrete (NAC), the load carrying capacity of FA20RAC and FA30RAC column specimens are higher by about 4% and 9% respectively. Prediction of full-scale column behaviour from the standard cylinder test highlights size effect that affects the peak load less in FARAC as compared to NAC. Two-dimensional numerical analysis of a transverse tie confined concrete is carried out using fibre element method. The effect of core concrete on the development of confining pressure is examined for RC columns with similar arrangement and properties of lateral ties.

Experimental Study of Post-heated Steel Reinforced Recycled Concrete Columns Repaired with CFRP

The mechanical and thermal properties of steel reinforced concrete columns with CFRP reinforcement were examined after exposure to a high temperature of 500 oC. The concrete made with normal and recycled coarse aggregate (RCA) was fabricated and three different RCA replacement ratios (0, 50%, and 100%) were investigated. The fatigue properties of steel reinforced concrete with RCA and CFRP reinforcement were tested for two million cycles at a frequency of 2.5 Hz. The test results show that the failure of strengthened specimens is mainly caused by rupture of CFRP jacket and buckling of inner section steel reinforcement. However, for the unstrengthened specimen, both of inner steel buckling and core concrete cracking are the main contributors to the damage. The load-bearing capacity, deformation and energy dissipation of the specimens during the fatigue test could be strengthened greatly by CFRP reinforcement. However, the CFRP reinforcement has little influence on the improvement of the stiffness of the specimens, which may be caused by a plastic damage accumulation during the early cycles of fatigue tests. Finally, a static test was conducted on the post-fatigue specimens, the results showed that a large decrease in stiffness was observed for the specimens subjected to high temperature and fatigue, and the fatigue loading had a higher influence on the specimens than the high temperature.

钢纤维再生混凝土柱大偏心受压承载力研究

钢纤维再生混凝土柱大偏心受压承载力研究

Structural behavior of recycled aggregates concrete filled steel tubular columns

This paper presents an experimental and numerical investigation to determine the behavior of steel tubular columns filled with recycled aggregates concrete up to failure under constant axial compression loads. The experimental program included two steel tube columns, four recycled concrete columns and eight composite columns filled with different types of recycled coarse aggregates (granite and ceramic). Different percentages of recycled coarse aggregates: 0, 25 and 50 of the percentage of the coarse aggregates (dolomite) were used. The results of the numerical model that was employed by the finite element program, ANSYS, were compared with the experimental results. The results of the experimental study and the finite element analysis were compared with the design equations using different national building codes: AISC1999, AISC2005 and EC4. The results indicated that the recycled aggregates concrete infill columns have slightly lower but comparable ultimate capacities compared with the specimens filled with normal concrete.

Axial compression behavior of reinforced geopolymer concrete columns with demolished concrete lumps

Abstract This paper presents results of an experimental study on the axial compression behavior of reinforced geopolymer concrete columns with demolished concrete lumps (DCLs). A total of 22 reinforced concrete short columns were tested under axial compression. The test variables include the type of fresh concrete (ordinary Portland cement concrete (CC) and geopolymer concrete (GC)), strength level of fresh concrete (FC) and demolished concrete, and replacement ratio of FC by DCLs. The test results were used to evaluate the effect of strength difference between fresh and demolished concrete, and replacement ratio of FC by DCLs on bearing capacity and deformation ductility of geopolymer concrete columns with DCLs. Data from these tests showed that the axial compression behaviors of short columns made of geopolymer concrete and ordinary concrete with DCLs were similar. The ultimate bearing capacity and stiffness of recycled concrete columns with DCLs decrease with an increase in replacement ratio. Nevertheless, the maximum reduction in bearing capacity of geopolymer recycled concrete columns is only 10%, when the replacement ratio of FC by DCLs is 24%. The strength difference between fresh concrete and DCLs has a significant influence on mechanical properties of recycled concrete columns, especially for geopolymer recycled concrete columns. Compared to ordinary recycled concrete columns with DCLs, geopolymer recycled concrete columns with DCLS exhibit a slight lower bearing capacity, but a higher ductility.

Finite Element Analysis of Uniaxial Compression of Glazed Hollow Bead of Recycled Concrete Short Columns

For traditional ordinary concrete wall column prone to thermal bridges, posted outside the insulation board short life than the life of the building，in the glazed hollow bead of recycled concrete foundation with good thermal conductivity test and compressive strength of the proposed ,use glazed hollow bead of recycled concrete exterior wall column instead of the traditional ordinary concrete wall column ,and using the finite element software ANSYS simulation analysis the uniaxial compression of glazed hollow bead of recycled concrete short columns and ordinary concrete short columns. Comparative analysis showed the same intensity level glazed hollow bead of recycled concrete ultimate compressive bearing capacity of an analog value the same as ordinary concrete short columns. To validate the ANSYS simulation of concrete short columns under uniaxial compression condition .

Experimental Study on Seismic Performance of Steel Reinforced Recycled Concrete Column

The pseudo-static tests were carried out on seven steel reinforced recycled concrete columns. The main parameters of specimens were recycled aggregate replacement ratio, axial compression ratio and volumetric stirrup ratio. The results indicate that the incorporation of recycled aggregate doesnt reduce the horizontal bearing capacity, ductility and the energy dissipation capacity of specimens and has little effect on seismic performance. The seismic performance of steel reinforced recycled concrete column decreases significantly in the high axial compression ratio. The ductility, horizontal bearing capacity and the energy dissipation capacity of the steel reinforced recycled concrete column increase with a rise in the volumetric stirrup ratio. This study provides a reference on the application of the steel reinforced recycled concrete column.

Seismic performance of steel-reinforced recycled concrete columns under low cyclic loads

This paper describes an experimental study of the seismic performance of steel-reinforced recycled concrete (SRRC) columns. Based on low cyclic loading tests of seven 1:2.5-scaled column specimens, the failure modes, hysteresis loops, skeleton curves, ductility, energy dissipation capacity, and stiffness degradation of SRRC columns were analyzed. The influence of recycled coarse aggregate (RCA) replacement percentages, axial compression ratios, and stirrup ratios on the seismic performance of SRRC columns was investigated in detail. The test results show that the seismic performance of SRRC columns decreases slightly as the RCA replacement percentage increases. The results also indicate that appropriate design of the axial compression ratio and stirrup ratio can improve the seismic performance of SRRC columns. The average values of the ductility factor and the equivalent viscous damping coefficient with respect to the loop of ultimate load of the columns were 3.47 and 0.217, respectively, which reflect the SRRC columns’ good performance in terms of earthquake resistance.

An Experimental Study on the Seismic Behavior of Recycled Concrete Short Columns with Different Stirrup Ratio

A comparative study is conducted on the seismic behaviors of five 1/2 scale recycled concrete short columns with 1.75 shear span ratios. The stirrup ratio in the specimens was changed from 0.4%, 0.9%, to 1.29% while the ratio of their longitudinal reinforcement was the same. Crossed reinforcing bars were set in two of the specimens. Cyclic loading test was carried out for the specimens under axial compression ratio 0.4. The stiffness and its degradation, load-carrying capacity, ductility, hysteretic behavior, energy dissipation and failure phenomena of each short column were analyzed. Results show that, with the increase of the stirrup ratio in the specimens, the shear failure of the specimens is getting lighter and lighter. And the load-carrying capacity, ductility, energy dissipation capacity are improved greatly, but the rate of the increase is tending to slow. Moreover, crossed reinforcing bars in the short columns are able to improve the seismic behavior. Recycled concrete can be used for structural columns with low axial compression ratio in earthquake area.

Experimental Study on Axial Compressive Behaviors of Steel Recycled Concrete Composite Columns

In order to reveal the performance of steel recycled concrete composite columns, 6 specimens were designed for axial compression loading experiment. And two factors which are recycled coarse aggregate replacement percentage and slenderness ratio of column are taken into consideration. The bearing capacity and load-displacement curves of composite columns are obtained. Based on the test, the failure patterns and the influence of recycled coarse aggregate replacement percentage and slenderness ratio to axial compression load-bearing capacity are analyzed. In the end, the calculation formula for axial compression load of steel recycled concrete composite columns is presented.

Experimental Study of Recycled Concrete Columns with Corroded Rebars under Axial Force

Corrosion is one of the major factors affecting the durability of recycled concrete structures. Through experimental test of seven recycled concrete columns with corroded rebars, issues were discussed concerning the failure patterns, the effects of the degree of rebar corrosion on the ultimate load and axial deformation of recycled concrete columns. The test results show that the ultimate load decreases and the axial deformation increases as the degree of rebar corrosion increases.