Mechanical Performance Of Specimens Research Articles

Performance of box-shaped column connection achieved with local grouting and bolts

To prevent the traditional box-shaped column flange connection from affecting the facade of the overall structure, this study proposed a box-shaped column connection achieved by local grouting and bolts. One integral box-shaped column specimen and two box-shaped column connection specimens were designed. The seismic performance of the connection and the influence of local grouting on the mechanical performance of the connection were studied. The failure phenomenon of the specimen was observed, and the mechanical performance of specimens, such as hysteretic behavior, bearing capacity, stiffness degradation, ductility, and energy dissipation capacity were examined. Results are as follows: the failure mode of the integral box-shaped column specimen and the specimen connected by local grouting and bolts is plastic hinge failure; the effect of local grouting can improve the integrity of the connection and obtain good energy dissipation capacity; the effect of local grouting can increase the bearing capacity of specimen by 24.84% and reduce the bolt tensile force by 34.37%; the steel connector at the column–column joint prevented the buckling deformation of the box-shaped column; the ductility is increased by 22.06%; no slip occurred between the upper and lower steel connector. Therefore, the new joint is safe and reliable. Through numerical simulation analysis, the research results show that the joint can be equivalent to rigid connection. The peak bearing capacity of the box–column joint is checked according to the Code for Seismic Design of Buildings: GB50011–2010. The calculation results are consistent with the experiment results.

Experimental Study on SSRC under Eccentric Compression

The use of stainless steel bars can improve the durability and sustainability of building materials. Through the static performance test, this research analyzes the failure pattern and bearing performance of bias stainless steel reinforced concrete (SSRC) column. The influence of reinforcement ratio of longitudinal bars and eccentricity on the mechanical performance of specimens was studied. Different constitutive models of stainless steel bars were used to calculate the ultimate bearing capacity of the section of the column under eccentric compression column. Based on the experimental results, a method to modify the expression of the design specification is proposed. And, the results were compared with the test results. The results showed that the damage patterns and failure modes of SSRC columns are essentially the same as those of traditional reinforced concrete columns. The bearing capacity of SSRC columns rises with the increase in the longitudinal reinforcement ratio, and the ductility of the specimens is enhanced. The ultimate load of the specimen decreases with the rise in eccentricity but the deflection increases gradually. The strain distribution of the mid-span section of the SSRC column conforms to the plane section assumption. The bearing capacity of the specimen can be analyzed by referring to the calculation method of the specification, and some parameters in the calculation formula of the specification are modified to adapt to the design and calculation of the SSRC column.

Axial compressive performance of RAC-encased RACFST composite columns

A new type of composite column, recycled aggregate concrete (RAC)-encased recycled aggregate concrete-filled steel tube (RACFST) composite columns, promotes the RAC extensive utilization considering synergistic effect between the RAC and the steel tube, which is an attempt to develop environmentally sustainable concrete in high-rise buildings. In this paper, experimental research investigated the axial compressive behavior of RAC-encased RACFST composite columns. Twenty 1:3-scaled specimens were fabricated to test until failure under axial compressive loading. The main variable parameters affecting the behaviour of specimens were recycled coarse aggregate replacement ratio (range from 0% to 100% with 10% increase), stirrup spacing (s = 50 mm, 70 mm, 100 mm, 120 mm), diameter of steel tube (D = 89 mm, 114 mm), concrete strength grade (RC40, RC60) and longitudinal reinforcement ratio (4▪12, 8▪12). The failure modes, the whole load-deformation curves and the mechanical performance of specimens were also obtained based on static loading experiments and theoretical analysis. It was found that RAC-encased RACFST composite columns, which were subjected to identical axial loads, exhibited more favorable bearing capacity and deformation than those of a comparative reinforced recycled aggregate concrete columns (RACC). The replacement ratio of RCA had a slight effect on the mechanical performance of RAC-encased RACFST composite columns, the optimal substitution ratio of RCA was 50–60%. Based on the previous theory of superposition, the concrete cover is considered, and a calculation formula with double reduction coefficients of the axial load-bearing capacity of composite columns is proposed. Compared to the simplified superimposition method and the Chinese code Technical specification for steel tube-reinforced concrete column structure (CECS188:2005), the calculated results of axial compression bearing capacity by the proposed formula are in more agreement with the experimental values, with errors no greater than 15%.

Effect of build orientation on the surface quality, microstructure and mechanical properties of selective laser melting 316L stainless steel

PurposeThe purpose of this paper is to investigate the density, surface quality, microstructure and mechanical properties of the components of the selective laser melting (SLM) parts made at different building orientations. SLM is an additive manufacturing technique for three-dimensional parts. The process parameters are known to affect the properties of the eventual part. In this study, process parameters were investigated in the building of 316L structures at a variety of building orientations and for which the fracture toughness was measured.Design/methodology/approachHardness and tensile tests were carried out to evaluate the effect of consolidation on the mechanical performance of specimens. Optical and electron microscopy were used to characterise the microstructure of the SLM specimens and their effects on properties relating to fracture and the mechanics. It was found that the density of built samples is 96 per cent, and the hardness is similar in comparison to conventional material.FindingsThe highest fracture toughness value was found to be 176 MPa m^(1/2) in the oz. building direction, and the lowest value was 145 MPa m^(1/2) in the z building direction. This was due to pores and some cracks at the edge, which are slightly lower in comparison to a conventional product. The build direction does have an effect on the microstructure of parts, which subsequently has an effect upon their mechanical properties and surface quality. Dendritic grain structures were found in oz. samples due to the high temperature gradient, fast cooling rate and reduced porosity. The tensile properties of such parts were found to be better than those made from conventional material.Originality/valueThe relationship between the process parameters, microstructure, surface quality and toughness has not previously been reported.

Effect of enhancement of interface performance on mechanical properties of shape memory alloy hybrid composites

Effect of enhancement of interface performance on mechanical properties of shape memory alloy hybrid composites (SMAHCs) was investigated in this work. Composite laminates without Ni-Ti shape memory alloy (SMA) fibers, with Ni-Ti SMA fibers polished, corroded and modified by silane coupling agent KH550 were taken into comparison to investigate the effect of surface treatments. Surface morphology of Ni-Ti fibers under different treatments were observed with scanning electron microscope. The mechanical performance of specimens without Ni-Ti fibers and with Ni-Ti fibers under different treatments were investigated through tensile, three-point bending and low-velocity experiments. The morphology and micromorphology were observed to study the effect of different surface treatment methods. The conclusion shows that embedded Ni-Ti SMA fibers can enhance the mechanical performance of composite laminates. However, the performance of Ni-Ti SMA fibers was restrained by the poor interface performance. After surface treatments, SMAHCs illustrate better mechanical performance owing to the enhanced interface performance. Among all the surface treatment methods, modification with silane coupling agent KH550 shows the best effect.