Advanced Materials Research Vols. 243-249

Abstract: Hybrid FRP-concrete-steel double-skin tubular columns (DSTCs) are a new form of hybrid structural members. A hybrid DTSC consists of an inner steel tube, an outer FRP tube and a concrete infill between them. Hybrid DSTCs possess many important advantages over conventional structural members, including their excellent corrosion resistance as well as excellent ductility and seismic resistance. A large amount of research has been conducted on hybrid DSTCs, but the existing experimental studies have been limited to the testing of small-scale columns. This paper presents preliminary results from the first series of large-scale axial compression tests on hybrid DSTCs, which forms part of a larger experimental study currently under way at The Hong Kong Polytechnic University. These test results confirm the excellent axial compressive response of hybrid DSTCs as initially expected.

Abstract: Ultra High Performance Concrete (UHPC), which has very special properties that are remarkably different to the properties of normal and high performance concrete, is being increasingly used for the construction of structure. In this paper, an experimental program was formulated to investigate the characteristics of complete stress-strain curve of UHPC in uniaxial compression and flexural behaviors of prestressed UHPC beams. The particular focus was the influence of the partial prestress ratio and jacking stress on the flexural response of UHPC beams. The results show that UHPC is of good deformability, and a general form of the serpentine curve is proposed to represent the complete stress-strain relationship of UHPC in compression. The tests of beams demonstrated that the UHPC beams have an excellent behavior in load carrying capacity, crack distribution and deformability, their ultimate deflection can reach 1/34～1/70 of the span. Based on this investigation, theoretical correlations for the prediction structure response of UHPC beam are proposed.

Abstract: A carbonation model of reinforced concrete structures subjected to mechanical load based on experimental work is proposed in the paper. Correspondingly, a series of reliability analysis and service life prediction is carried out and reasonable results are acquired. Besides the effect of concrete cover, it indicates that mechanical load impacts the reliability and service life of the reinforced concrete structures significantly through example calculation. In the case of concrete cover of 40mm, the service life is shortened nearly half under a tensile load of 60% while the service life is lengthened 30% under a compressive load of 30%. In service life design or long term performance assessment, more work should be done with the consideration of the mechanical load effect.

Abstract: Based on the connection tests of the semi-rigid nodes in the beam-column T-typed member and end plate of steel frame, this paper analyzes the failure phenomena, stiffness, bearing capacity and flexibility of two types of attachments. And according to the tests results, it compares the two types of attachments each other and proposes that T-typed member is a better type of attachment on its bearing capacity and flexibility. Therefore, it provides the experimental basis for the ideal design and application of attachments among the semi-rigid nodes in steel structures.

Abstract: Nonlinear finite element (FE) analysis models of CFT composite frames with floor slab were established by Msc.Marc to investigate the seismic behavior of composite frames. A number of material nonlinearities and contact nonlinearities, as well as geometry nonlinearities, were taken into account, including elastoplastic properties of steel and concrete, concrete cracking and tension stiffening, steel fracture, interface slip between concrete slabs and steel beams, P-D effects etc. The elasto-plastic behavior, as well as fracture and post-fracture behavior, of the FE analysis models agreed well with those of the test specimens. The beam and panel zone deformation of the analysis models is also in good agreement with that of the test specimen. It is concluded that FE analysis is useful not only for monotonic load analysis but also for cyclic load analysis. It is a helpful tool to expand the information on seismic behavior of composite frame.

Abstract: In this paper, a 9-storey Benchmark frame model was used to analyze the response of joints due to sudden column loss. On the basis of the substructure model, the static and dynamic nonlinear analyses were conducted seriatim using the alternative path method. It is found that the removals of the ground columns bring high-level joint moments and mild increasing of axial forces. In particular, the removal of side column with pin-ended connection results in the largest vertical displacement of adjacent joint and increase the flexural demands to the next joint. For this model, the most critical case appears at the failure of hinged side column, the next is the rigid side column.

Abstract: This research investigated the influences of rubber content and water-cement ratio on the compressive strength of roller compacted rubberized concrete (RCR). The mix design of RCR was made by replacing same volume of sand with rubber chips based on the control concrete mix. Four rubber contents (50 kg/m³, 80 kg/m³, 100 kg/m³ and 120 kg/m³) and six water-cement ratios (0.30, 0.35, 0.40, 0.45, 0.50 and 0.55) were used. The specimen cubes were tested in compression at 28d with the load continuously and automatically measured until failure. Test results show that RCR exhibits low compressive strength but a ductile and plastic failure mode, the more the rubber used, the more the compressive strength reduced and the larger toughness obtained. Same as normal concrete, the compressive strength of RCR is also directly related to the water-cement ratio，the smaller the water-cement ratio, the higher the compressive strength. Based on the experimental results, a strength formula was developed to estimate the strength of RCR as a function of the cement strength, water-cement ratio and the rubber content.

Abstract: The design of the glass skylight of the courtyard in an office building is introduced in the paper. One-way stability of the cross bar in the cable system is analyzed. The support system designed by the new style, reasonable force, to meet the requirements of normal use, the surrounding concrete support structures of smaller, saving construction costs, so that the top economic and practical lighting. By Midas-based stress analysis software, the cross-bar system, a number of capacity factor and to strengthen measures were discussed, which can be a useful reference for similar projects.

Abstract: Long concrete structure is frequently used in modern buildings or structures. As the main measures of achieving seamless construction and crack control of long concrete structure, strengthening strip and after-irrigation-strip have been widely applied. However, compared with after-irrigation-strip, the clear advantage of strengthening strip is closure ahead. Therefore, this paper from aspects of theoretical analysis and engineering application replace the after-irrigation-strip with intermittent strengthening strip in one original design of a project. Since the completion of construction, there are no harmful cracks in the structure. This article also describes the project quality control measures and technical and economic analysis for the design and construction of similar projects.

Abstract: In order to enhance the pertinence of agriculture building design, the experiment and numerical simulation on cold-formed thin-walled steel members with “л” section under axial compressive force were conducted to investigate the effects of residual stress on bearing capacity of them. For the members, there are inevitably initial defects, such as initial bending, initial eccentricity and residual stress due to the manufacturing error. In the numerical simulation, initial bending and initial eccentricity of the members were considered. The results show that the residual stress affects instability forms of the members. And as the member slenderness ratio increases from 69 to 200, the bearing capacity of member with residual stress decreases from 12.8% to 84.9% of that without residual stress.