Advanced Materials Research Vols. 255-260

Abstract: How to evaluate building sustainable performance is a hot issue in the world, the paper combine the “natural energy”, “energy recycling” and “ energy consumption” with 12 indicators into a evaluation system, and then use the set pair analysis(SPA) methods to evaluate the building sustainable performance. Through the empirical analysis with 3 cases, the results show that increase the natural energy utilization and enhance the energy recycling can reduce energy consumption and improve the building sustainable performance. In addition, the SPA also can quantitative the evaluation results.

Abstract: This paper presents research on 13 beams with nonprestressed and prestressed helical rib steel wire bonded in sawed grooves in the concrete cover under monotonous loads based on the lack of old strengthening methods. The prestressing, stressing process, first-crack load, steel-yielding load, ultimate load at failure and deformation are systematically studied. The results from the tests show that this new strengthening technique using helical rib steel wire bonding in the concrete cover is an efficient method, which can overcome the problems with peeling of the strengthening material when the surface bonded FRP laminates, also overcome the shortages of nonprestressed beams. The prestressed beams exhibited higher first-crack load, higher steel-yielding load, as well as a larger deformation capacity as compared to nonprestressed strengthened beams, which is important for a construction^'s lifetime; the fatigue behavior will improve and as a consequence the crack widths will be smaller, which can result in increased durability, which should indicate a more advantageous behavior in the service limit state (SLS). However, the ultimate load at failure is as high as nonprestressed beams, but in relation not as large as for the cracking and yielding. The ultimate load at failure is also higher as compared to non strengthened beams. The results provide a reference for engineering application.

Abstract: Three-bending experiments were performed on RC beams strengthened with prestressed CFRP under static and cycle loading. Prestressed CFRP obviously increases the load-carrying capacity and fatigue life of strengthened RC beam. And it greatly increases the flexural stiffness of strengthened beam. The failure modes of the beams go through concrete cracking, CFRP debonding from concrete and beam fractured. The vertical flexibility history at midspan is decomposed into three stages. And then fatigue damage is defined by flexural stiffness and its evolvement shows three stages of nucleation, growth and mutation.

Abstract: The effect of thickness of externally bonded carbon fiber laminate (CFRP) on load-carrying capacity and failure modes was analyzed for the strengthened reinforced concrete (RC) beams under bending load. According to the balance equations of applied force and moment, the relation was obtained between ultimate loading of strengthened beam and thickness of CFRP, and the failure modes were predicted for the CFRP strengthened beams. The load-carrying capacity of strengthened RC beam is higher with thicker externally bonded CFRP until it reaches the ultimate loading. The mechanical analysis is in good agreement with the three-point bending experiments performed on CFRP strengthened RC beams.

Abstract: The mechanical characteristics of jointed rocks are mainly controlled by geometrical features of intermittent joints. The failure mechanism and shear behavior of discontinuous joints are simulated by series of direct shear tests using the particle flow code (PFC2D). The effects of joint persistence, separation and azimuth angle on the failure strength of jointed rock are studied in detail. The results shows that peak shear strength can be considered as a function of the geometrical parameters, which is in a reasonable accordance with other experimental results. Meanwhile, as for failure mechanism, joint separation and azimuth angle are especially discussed, and specific damage patterns are presented as well.

Abstract: This paper presents an experimental investigation of the mechanic behavior of 9 concrete-filled square steel tube columns (CFSST) subjected to eccentric loading. The primary parameters of the specimens are eccentricity ratios, slenderness ratios and concrete strength. The results showed that the eccentricity ratios and slenderness ratios are the primary factors to influence the load-bearing capacity of CFSST columns, with the increase of eccentricity ratios and slenderness ratios, the limit load-bearing capacity reduced gradually. The influence of concrete strength to load-bearing capacity decreased gradually with the increase of eccentricity ratios and slenderness ratios.

Abstract: Based on the fuzzy manthematics theory,two-grade fuzzy comprehensive judgement used in reinforced concrete structure reliability appraisal is studied, the fuzzy comprehensive appraising model of structure reliability is founded. The paper supplies a fuzzy evaluation model for reinforced concrete fuzzy comprehensive judgment from qualitative analyze to quantificational analyze.

Abstract: In the experiment of the behaviour of the connection between steel beam and concrete wall, surface FBG sensor and resistance strain gauge were located at the same measuring point of the flange girth of the steel beam. Measuring results show that the measuring effectiveness of both methods is uniform. And the surface FBG sensor has the merits of using conveniently and non-vitiating. So using surface FBG sensor to measure the surface strains of structural members in structure experiment is feasible.

Abstract: Forged Ti-6Al-4V welded structure by electronic beam welding (EBW) as integrally bladed disk (blisk) structure in advanced aero-engine has been widely applied. It is necessary to analyze microstructure and mechanical properties of Ti-6Al-4V welded joints by EBW for failure analysis and structure design of blisk. Firstly the microstructure and mechanical properties of forged Ti-6Al-4V welded joints was focused on. Grains in the weld zone become coarse and large gradient organization structure appears in the heat affected zone (HAZ), which presents significant local heterogeneity. Microhardness of the weld zone is about 20% higher than that of the base metal. The size of different region of the welded joints was estimated. Then static tensile test of three different specimens were carried on. Experiment results show that the tensile and yield strength of welded joints are not less than that of the base metal. Finally the empirical relationship between strength and hardness of Ti-6Al-4V alloy is established. Tensile strength of the weld zone and the base metal were estimated. Compared to experiment data, the deviation is 3.56%, 0.097% respectively.

Abstract: Due to the volume expansion of corroded rebar products, the cracking of the concrete cover would occur, and has a serious impact on the durability of the concrete structure. In this paper, a numerical model was established for the simulation of the corrosion of rebar in concrete structures with the aid of finite element analysis software. The distribution of stress in concrete around rebar, that due to the expansion of these corroded rebar products, was obtained. The theory of elasticity method is used to validate the distribution of stress in concrete around rebar. The location of cracks would be predicted by the distribution of stress in concrete around the rebar.