Applied Mechanics and Materials Vols. 174-177

Abstract: This paper focuses on the mechanical properties of carbon fiber cloth reinforced bamboos. Using the carbon fiber cloth to reinforce circularly the bamboo can protect dry bursting of the bamboos and improve its mechanical performances. A series of experiments were carried out to investigate the compressive strength, tensile strength and bending strength of bamboo reinforced with carbon fiber cloth. The mechanical performances of bamboos with and without reinforcing were compared and the efficient reinforcing method was suggested, with such method the compressive strength and bending strength of carbon fiber reinforced bamboos could be increased obviously compared with that of bamboos without reinforcing.

Abstract: 500 MPa level hot-rolled ribbed bars of fine grains (HRBF500) is a successfully developed new-type steel in Chain. The fatigue behavior of partially prestressed reinforced concrete (RC) beams with HRBF500 bars was investigated in fatigue tests of pre-tensioned T-beams. The beams are simply supported with the same overall dimensions, and the main parameter in the study is prestress degree and longitudinal steel ratio. Four beams were constructed and tested under constant-amplitude fatigue loading. All beams are initially cracked before the application of repeated loading. The stress evolution of HRBF500 bars and prestressed strands, the information about crack growth and the deflection developments of test beams were presented. The main factors that affect the fatigue properties of prestressed concrete test beams were fully discussed. Test results indicate that, the prestressed concrete beams reinforced with appropriate amount of HRBF500 bars and reasonable prestressing configurations can survive 2.5 millions cycles of constant-amplitude fatigue loading using an upper-bound fatigue load producing tensile stress of less than 150 MPa in HRBF500 bars. The results provide important guidance for the fatigue design of prestressed concrete beams with HRBF500 bars.

Abstract: Steel wire-continuous basalt fiber composite plate (SBFCP) is a new type of plate whose main constituents are steel wire and basalt fiber reinforced polymer (BFRP). To investigate the mechanical properties of SBFCP, both theoretical and experimental studies were conducted. A tri-linear model was proposed to predict the stress-strain relationship of SBFCP. Considering two parameters, the volume ratio of steel wires in SBFCP and the type of composite pattern, a monotonic tensile experiment was carried out. Test results show that SBFCP has excellent properties, including high modulus, high strength, and good ductility. Results also demonstrate that the volume ratio of steel wires affects the modulus of SBFCP significantly whereas the type of composite pattern shows little effect on properties of SBFCP.

Abstract: Cracks can reduce the service life of a concrete structure by allowing aggressive agents to penetrate through it in easy ways. Free shrinkage evaluation alone is not enough to determine if cracking can be expected in a structure since concrete creep behaviour, stiffness and toughness also influence the potential for cracking. Consequently, it is rather interesting to perform restrained shrinkage tests, such as the ring test according to ASTM C 1581–04. The testing procedure involves concrete ring specimens restrained by an inner steel ring on which strain gauges are placed to determine the age of cracking, since abrupt changes in the steel strain occur when concrete is cracked. Both the ring test and free shrinkage test should be carried out in the same exposure conditions, 21°C and 50% relative humidity. Moreover, compressive and tensile strengths of concrete were evaluated on cubic specimens at the time of its cracking and up to 28 days of curing. By means of analytical and numerical models of the ring specimen, some useful information on the stress induced in the material and on the tensile creep behaviour of concrete can be extrapolated thus allowing to better interpret the experimental results. This experimental procedure enables to study the influence of concrete mixture composition on the potential for early-age cracking of concrete. In particular, in this work the influence on early-age cracking of recycled-concrete aggregate partially replacing virgin sand was tested.

Abstract: In this work, the possibility of using environmentally-friendly mortars (with crushed bricks replacing sand) as bedding mortars for repair of historical building was studied. When bedding mortars are used for intervention on historical building a compatibility issue can emerge. Indeed, if masonry containing sulphate salts is restored by using mortars based on hydraulic binders the risk of failure is high. For this reason, as binders alternatively a blended cement and a hydraulic lime were used, both proving to be unsensitive to sulphates. Two crushed brick aggregates were alternatively added to the mortars by fully replacing virgin sand, they showed different grain size distributions and, consequently, a different content of very fine materials. All the environmentally-friendly mortars were characterized from a mechanical point of view. Then their physical behaviour was studied trough microstructure characterization, as well as through the evaluation of both their resistance to the vapor permeability and their capillary water absorption. Results obtained showed that the use of recycled bricks instead of virgin sand, particularly if roughly ground, could allow to achieve a good compromise between vapour permeability and capillary absorption of mortar.

Abstract: Based on a large number of experiments, two-parameter and three-parameter Weibull distribution probability models have been established to study the flexural fatigue with different kinds of glass fiber contents (0%,0.6%,0.8%,1%) and different stress levels(0.7,0.75,0.8)in this paper. It is the S-N Curve and P-S-N Curve that we have obtained. According to the comparison of two probability models, We can see that the fatigue life of glass fiber concrete beam can preferably obey two-parameter and three-parameter Weibull distribution, but the three-parameter Weibull distribution is so much the better. The fatigue life will augment with the increase of the volume fraction of glass fiber.

Abstract: There are no clear design standards for the reinforcements or concealed beams under partitions in reinforced concrete slabs which often appear in reinforced-concrete residential buildings. Designers, in most cases, have to rely on engineering experiences after a simple calculation to design such reinforcements or concealed beams. In this paper, we built a finite element model of such reinforced concrete slabs in SAP2000. The element for the plates was layered shell element. By changing the span , thickness and boundary constraints of the plate, the materials of the partition , the diameter of the reinforcements to analyze the force of the plate. Based on results analyzed, we discuss the internal forces of such plates, and offer suggestions for the selection of partitions and design of reinforcements.

Abstract: Because the difference between the autoclaved aerated concrete and ordinary masonry mortar with thermal conductivity is too large, also easy to cause the bricking-up appearance the cold bridge and even the phenomenon of condensation, the author have study special thermal-insulation masonry mortar for autoclaved aerated concrete, about solving between the aerated concrete and ordinary mortar problem filling cracks, it is more important to resolve the big difference between the thermal conductivity, improving the insulation properties of aerated concrete special mortar. The performance as per special masonry mortar and plaster mortar for autoclaved aerated concrete (China national standard JC890-2001), supporting thermal-insulation masonry mortar effectively improved the cold bridge phenomenon of energy loss occurs.

Abstract: This paper presents the results of laboratory and outdoor exposure site studies on belite-rich cement concrete with phosphorous slag powder and fly ash. The parameters studied included strength, hydration heat, ultimate elongation, Young’s modulus, and adiabatic in temperature. The experimental results showed that belite-rich cement resulted in a higher rate of strength development of mortar and concrete at later ages when compared with that of moderate-heat Portland cement. And the hydration heat of belite-rich cement is lower than that of reference. This is due to the different phase composition of the two cements. Belite-rich cement contains less C₃S but more C₂S than moderate-heat Portland cement. In addition, belite-rich cement concrete with phosphorous slag powder and fly ash exhibited better performances than those of moderate-heat Portland cement concrete.

Abstract: The addition of ceramsite aimed to improve the toughness of high strength PVA-FRCC and reduce its weight. The quasi-static and dynamic compressive tests were carried out to obtain the compressive strength and the dynamic response of PVA-FRCC with the addition of ceramsite, respectively. The ceramsite can weaken the compressive strength of PVA-FRCC, the quasi-static compressive strength decrease with the increase of ceramsite volume fraction. With the increase of strain rate, the dynamic peak stress and critical compressive strain increase with different ceramsite volume fraction. At the same strain rate level, the dynamic compressive strength decrease with the increase of ceramsite volume fraction. The critical compressive strain of PVA-FRCC with 3% ceramsite volume fraction have the highest critical compressive strain at different strain rate.