Papers by Keyword: HSC

Abstract: This paper presents a study from an ongoing research project on the bond performance of flexural prisms strengthened using carbon-fiber-reinforced polymer (CFRP) laminates. The primary objective is to evaluate the effect of normal-strength concrete (NSC – 30MPa) and high-strength concrete (HSC - 50MPa) on the bond performance of plain concrete prisms notched at the mid-span and strengthened using CFRP laminates. Six of the twelve plain concrete prisms were strengthened using CFRP laminates, while the remaining prisms were unstrengthened to serve as control specimens. After achieving 28 days of curing in standard lab conditions, all prisms were tested under a four-point bending test. The ultimate mid-span deflection, maximum and ultimate strains at the mid-span, strain distribution at different positions along the length of the laminate, and bond/shear stress versus slip were analyzed to evaluate the bond performance of flexural prisms. The average ultimate load-carrying capacities and mid-span deflection of the NSC and HSC groups were 31.33 and 35.02 kN and 0.55 and 1.54 mm, respectively. The average CFRP strain values at the mid-span corresponding to the ultimate load were 5005 and 3544 με for the NSC and HSC groups, respectively. The maximum attained bond-stress values for NSC and HSC groups were 1.71 and 1.42 MPa, respectively. The corresponding values for slip at maximum bond stress are 0.27 and 0.24 mm for the two groups, respectively. It was concluded from the study that the concrete compressive strength has minimal effect on the flexural bond performance of concrete prisms externally bonded with CFRP laminates.

Abstract: The subject of the work focuses on hardened-precipitation type alloys Al-Mg-Si which constitute the primary component material used to build homogeneous electric wires, type AAAC (All Aluminium Alloy Conductor). The material in consideration is a well-known and well-studied alloy, particularly in terms of the possibilities for using it in thermal treatment processes. However, the subject literature does not present a comprehensive recognition of the effect of heat treatment parameters on the set of mechanical and electrical properties in wires grade 6101. In particular, the study presents the results of experiments that show the possibility of controlling the AlMgSi wire properties by means of selecting the heat treatment parameters for simultaneously obtaining a high tensile strength and high electrical conductivity. Hence, the research described in this paper focuses mostly on determining the impact of the Mg and Si content on the electrical and mechanical properties of wires of Al-Mg-Si wire alloys.

Abstract: HPC and UHPC concretes are finding their ways both to new structures and to retrofitting of existing structures. Herein specific material properties as well as structural examples are discussed. New Codes and Recommendations provide description of material properties and design rules for HPC/UHPC structures and structural elements.

Abstract: With the extensive use of HSC in the tall building and super high-rise building, the harm of HSC subjected to fire has also been increasing. For the concrete structure in the seismic region after fire, its seismic performance after repair directly relates to the structure safety under the action of possible earthquake in the future. Based on the experimental data in the preliminary research, seismic response analysis on the repaired HSC structure after fire was made according to the principle of uniform section. The results indicate that the seismic performance of HSC frame structure repaired by the principle of uniform section can be restored to the level before fire. But we should pay more attention to the interlaminar maximum displacement of fire storey, which should be partly strengthened when necessary.

Abstract: Moisture transport in high strength concrete is investigated in this paper. The experiment that involves the water suction is carried out in a long-term. The moisture profiles are measured by non-destructive capacitance method, the last profile is determined gravimetrically. The suction experiment is carried out in isothermal condition at the temperature of 22±1 °C and 25-30% relative humidity.

Abstract: In order to discuss the effect of different cooling methods, dosage and length of PP fiber on the splitting tensile strength of PPHSC after high temperatures, experiments were carried out on the splitting tensile strength of C60 HSC mixed with PP fibers with different dosage ( 1.0kg/m³, 1.5 kg/m³, 2.0kg/m³, 2.5 kg/m³) and length (8mm,19mm) before and after high temperatures. The test results indicated that the relative residual splitting tensile strength of PPHSC totally declined with the increase of temperature, meanwhile, the strength value of HSC cooled in air was higher than that cooled in water on the whole. The addition of PP fiber with the length of 8mm contributed to the enhancement of the relative residual splitting tensile strength of HSC after high temperatures, whereas, only the HSC mixed with 1.0 kg/m³ PP fibers had a greater strength than plain concrete when the length of fiber was 19mm. After exposure to high temperatures, the relative residual splitting tensile strength of HSC with PP fibers 8mm in length was completely higher than those with 19mm.

Abstract: The selection of mix proportion is the process of choosing suitable ingredients of concrete and determine their quantities with the object of producing as economically as possible concrete of notably strength. The current paper deals with the mix design of both an HSC and HSFRC constituted by volcanic aggregates from the quarries of Eastern Sicily in Italy. The mix design was carried out on eight different concrete mixtures by using the theoretical model developed by Feret – De Larrard’s and it is capable of simulating the experimental compressive strength. The HSFRC mixtures consider different volume fractions of fibers equal to 0% (HRC), 0.5% and 2% (HSFRC). Straight Polyvinylalcohol (PVA) and hooked-end steel fibers (ACC) were the two types of fibers employed in the study. Compression and tensile tests were carried out on specimens performed according to UNI codes in order to validate the mixture proportion method adopted. The HSFRC (0.5%) mixtures did not show great differences in mechanical performance by any variation of the fiber type (steel or PVA). The mechanical properties obtained by experimental tests give back a very good accordance with the theoretical prediction of the mix design procedure adopted, and with the data reported in the literature in terms of toughness.

Abstract: The paper analyzes the structural behavior of high strength concrete (HSC) beams reinforced with hybrid glass fiber reinforced polymer (GFRP) and steel reinforcements. The analysis refers to HSC beams reinforced with GFRP rebars and steel rebars placed in different layers. Results of the experimental and theoretical investigation are represented and discussed. Significant features of the structural behavior regarding flexural strength, deflection, are pointed out.

Abstract: Concrete with a compressive strength of 100MPa was produced with metakaolin(MK), and the effect of MK replacement levels on compressive strength of concrete with a water to binder ratio of 0.25 was studied in this paper. XRD, microhardness tests, SEM and MIP were used to investigate the influences of MK on the phase composition, microhardness of interfacial transition zone(ITZ), microstructural morphology and pore structure of the high-strength concrete (HSC). The results showed that the incorporation of MK promoted the hydration process and decreased the amount of Ca(OH)2 crystals. Furthermore, MK increased the ITZ microhardness of HSC, enhanced the hydrates and improved the bond performance of aggregate and paste. The weak zone between aggregate and paste became almost disappeared when 10% MK was blended. Meanwhile, refinement of the concrete pore structure was obtained in the presence of MK. The improvement of strength and microstructure became more obvious as the MK replacement level increased to 15%.

Abstract: Human Skin Color(HSC) features have been widely used in video moving human positioning. However, in complex background video sequences, due to illumination changes or other moving objects which have similar HSC regions, the effect of moving human positioning is not satisfactory. A new method of moving human positioning applied on complex background video sequences is presented in this paper. Firstly, brightness information of the video sequence images is detected and analyzed based on HSV color model. Secondly, adopt the multi frame subtraction method to extract the moving object regions from motionless background. Then, the regions with distinctive HSC features are separated from other moving objects using the data fusion model of HSC and brightness information. Finally, identify human object among regions with HSC features according to the prior knowledge of human. The experimental results show that the method provided in this paper is effective in moving human positioning of complex background video, and has the strong illumination change adaptability and anti-jamming ability.