Applied Mechanics and Materials Vols. 438-439

Abstract: Frequency and mode are character parameters of structure, and mode is also self-contained coordinate basis vector of displacement, so mode can be used for concept design and mechanical design. Through depth-width ratio from one to seven, results indicate the whole deformation of structure varies from shear mode to bend mode gradually; except for vertical mode, general mode is not one deformation, it is coupled by several deformations and one deformation ratio is dominant. During three of depth-width ratio, structure deforms in shear mode, so masonry structure should be in that range. In order to exerting reinforced concrete and steel material property and energy consumption capacity, the depth-width ratio should be from three to seven. For depth-width ratio between five and seven, the first eight modes is the same, manifesting mode has convergence property.

Abstract: This paper studies cable-damper mitigation model due to indirect excitation caused by bridge deck vibration. In the new mitigation model, as a rule of thumb, we considered a parallel association of idealize damper with a spring to simulate the inherent stiffness of the damper. The result shows that the interaction between the stiffness of the viscous damper could deeply impact the damper effectiveness, and the external damping should be increased deeply to provide the same non-dimensional modal damping when the inclined angle of cable decreases. The optimum damping coefficient of the non-idealized damper decreases when the stiffness of the damper increases.

Abstract: t has previously been shown that human-structure dynamic system received much attention as a major topic in the serviceability performance and safety problems. In this study, the structure occupied by human are considered as a two degrees-of-freedom system. The dynamic characteristics of human-structure system are investigated by deriving the eigenvalue equation of the system. The response of structure to a person walking across it at various rates of walking is also researched. The results show that the pair natural frequencies of coupled system have a contrary trend when the crowd densities increase. It also demonstrates that the resonant situation occurs when structural fundamental frequency is equal to or an integer multiple of the pacing frequency.

Abstract: Deflection and stress of different cross section forms and its value are compared by finite element analysis of timberwork design model under the impact loading. The result indicates that decreasing the size of cross section or changing the section shape can effectively avoid the model too heavy and conservative design. In the case of horizontal loads applied on first floor, strengthening the column of first floor obviously reduces the deflection of model and improves the lateral stiffness. Keeping the column size of the first floor and choosing I-section significantly reduce the overall weight on condition of meeting the bearing capacity and stability, it also make the material higher utilization.

Abstract: Corrosion of steel bars has a serious influence on durability and safety of reinforced concrete structures, which should be effectively monitored for the maintenance of reinforced concrete structures. This paper reviews several main techniques firstly, and presents the ongoing work at Nanjing University of Aeronautics and Astronautics to develop sensors to monitor the corrosion of reinforcement in concrete. It is hoped that the paper will be helpful to the field engineers and laboratory researchers who are monitoring and studying the corrosion of reinforcement in concrete structures.

Abstract: Seven reinforced recycled-concrete beams were tested to study their flexural resistance considering the variations of the strength of recycled-concrete and the reinforcement ratio of longitudinal tensile rebar. The aggregates of recycled-concrete comprised the machine-made sand and the recycled coarse aggregate. The failure state of normal section and the flexural resistance of reinforced recycled-concrete beams affected by the strength of recycled-concrete and the reinforcement ratio were discussed. The results show that the failure states of reinforced recycled-concrete beams were similar with those of the ordinary reinforced concrete beams. The flexural resistance was controlled by the reinforcement ratio, and influenced increasingly by the strength of recycled-concrete with the increase of reinforcement ratio. The failure resistance of reinforced recycled-concrete beam can be calculated by the method for ordinary reinforced concrete beam specified in current design code GB50010-2010.

Abstract: On the basis of experimental results, this paper discusses the shear-crack behaviors such as shear-cracking force and shear-crack width of reinforced full-recycled aggregate concrete beams. The full-recycled aggregate concrete was developed for the sustainable development in civil engineering, in which the coarse aggregate was the recycled aggregate made of abandoned concrete, and the fine aggregate was the machine-made sand. Sixteen beams, six of them without stirrups, were tested with the shear-span ratio varying as 1.5, 2.0 and 3.0, and the ratio of stirrups varying from 0.19% to 0.35%. The results showed that the shear-cracking force of the beam was mainly affected by the shear-span ratio, the width of shear-cracks intersecting stirrups decreased with the increasing ratio of stirrups, but the maximum crack width almost exceeded the limit 0.3mm in the first class environmental condition specified in Chinese code GB50010-2010. Comparing the calculation results by substituting the test parameters of full-recycled aggregate concrete beams into the formula of ordinary reinforced concrete beams, the lower resistance of reinforced recycled concrete beam to shear-cracking, and the larger crack width intersecting stirrups should be noted in the structural design. Based on the test data, the formula for calculating the shear-cracking force and the shear-crack width of reinforced full-recycled aggregate concrete beams are suggested.

Abstract: To improve the flexural properties and lighten the weight of ordinary reinforced concrete beam (RCB), this paper develops a new type of superposed RCB in which the tensile zone was partially cast with the steel fiber reinforced full-lightweight concrete (SFRFLC). 10 beams with different height of SFRFLC were designed. Their flexural behaviors were measured including the concrete strain at mid-span cross section, the load vs deflection curve, the cracking load and the ultimate load. It may be concluded that the test beams damage in ductile, the concrete strains at mid-span cross section basically fit the assumption of plain cross section, the variations of load vs deflection curves are similar with obvious changes at the points of the cracking of concrete and the yield of tensile reinforcements, the cracking loads are almost equal, and the ultimate loads tends to decrease with the increasing height of SFRFLC. The SFRFLC and ordinary concrete work well together, the suitable height of SFRFLC is there should be further studied.

Abstract: The flexural behavior of concrete beams reinforced with CFRP-PCPs composite rebars was studied. Experimental results showed that the deflection of beams reinforced with highly prestressed prisms is at service loads coMParable to deflection of steel reinforced beam. Flexural cracks of CFRP-PCPs composite rebars reinforced beams are hairline before prism cracking, and widened after the prism cracking. When the concrete beam was reinforced with the prestressed concrete prisms, the crack width decreased as the prestress in the prism increased.

Abstract: The preexisting strains of structures have some influence on the efficiency of CFRP Laminate. Based on the analysis of the abundant existing research productions, the calculation formulas of CFRP Laminate are proposed based on the supposition of plane section and balance of forces considering the preexisting strain. And the formulas are easy to understand and master for designers. By discussing the relation between the preexisting strain and relative depth of compression area, the essentials of the impact on reinforcement effect of residual strain are confirmed. The results can offer reference bases for strengthening engineering design with CFRP.