Advanced Materials Research Vols. 602-604

Abstract: Generally because of the economic advantage and stable behavior in seismic loading, shearwalls combined with coupling slabs are widely used in high-rise apartment buildings. When analyzing such structures for lateral loads, however, the question of the actual stiffness and strength of the coupling slabs arises. For more accurate analysis approach, an experimental investigation was conducted with half-scale representations of the reinforced concrete shearwalls with the opening and coupled with slabs were subjected to cyclic loads. The test results of opening installed specimen, severe decrease of strength was observed. The decrease of strength of the shear walls by installation of openings shows a great deal of difference compared to previous researches. This is because flexural capacity of the slabs is working as coupling elements for the shear walls. The critical section of coupling slabs that works as coupling elements for shear walls was a little different from the results of previous researches.

Abstract: The safety operation of tailings initial dam is the necessary conditions to ensure that the tailings dam is steady. In view of the poor construction quality and the appearing of jet shape seepage with the tailings leak in a tailings initial dam, the thesis analyzed the dam composite of tailings initial dam, the study of dam stability was carried out in the different working conditions and the disaster prevention measures was discussed. The research results indicated that the cementation was better and the strength of rock-soil body was higher in the upper dam body of tailings initial dam. However, the gravel cementation was weaker and strength of rock mass was relatively lower in the bottom dam body of that. Based on the poor quality of construction and penetrating seepage with the tailings initial dam, it should be feasible to adopt the grouting reinforcement way so as to reinforce the tailings initial dam. But the grouting pressure should be not more than 0.2 MPa. It will rely on increasing the dam self-respect and decreasing reservoir water level in the grouting process to reduce the risk of landslide. The research results can provide the theory basis on the disaster prevention and control of the tailings initial dam.

Abstract: In this research we investigate the possibility of enhancing the way brick walls can be retrofitted in an economical manner and become more resistant to blast impact. Retrofitting a method usually done on constructed walls; however, the same strengthening procedures can also be applied to a new construction project. In this research we investigate three methods of reinforcing brick walls against blast impact. First, reinforcing the brick layer using carbon fiber strips only without epoxy, with the fiber being placed on the bare bricks before it is plastered with mortar finishing, second, reinforcing the brick wall by placing CFRP onto the bare bricks and fixing with epoxy prior to finishing or being plastered over with mortar, and third, retrofitting the outer surface of a finished, or plastered, brick wall with CFRP and fixed with epoxy as is commonly done. The impact test was conducted using a drop weight released at a fixed height to simulate blast energy of an explosion. The effects of the test on all the samples were observed to identify failure patterns. Flexural testing was also conducted to observe how the samples perform under normal flexural loading. It was discovered that the second option, i.e. placing the CFRP on the bare bricks and fixing with epoxy before it is finished or plastered over with mortar, performs the best. This is due to the CFRP being firmly fixed before mortar finishing, causing the CFRP to be held steadily in place during the impact, thus, helping the wall to resist the impact load. With the third option, the CFRP was able to resist the impact but, as has been observed in other studies, the CFRP delaminates from the wall. The first option does not work very well since the mortar is unable to perform as well as the epoxy in holding the fiber to the wall to resist the impact force. Thus, for plastered brick walls, it is better suited for it to be reinforced by FRP under the finished mortar rather than on it, thus reducing the problem of delaminated FRP from the wall surface.

Abstract: This study investigates the influence of partial shear interaction and partial strength beam-to-column joints on the seismic performance of a multi-story composite frame. The moment-rotation relationship of the beam-to-column joints and the force-slip curve of the beam-to-slab connections have been calibrated on the basis of available experimental tests. The results of the numerical investigations show that the energy dissipation of the composite frame increases by reducing the shear connection degree. The shear connection degree has a significant effect on the total dissipated energy in case of rigid joints, whereas in case of partial strength joints the contribution of the joints to the dissipated energy is predominant. Low shear connection degrees can provide a source of dissipated hysteretic energy, above all in case of rigid joints, and can reduce the ductility demand on other parts of a composite frame, such as partial strength beam-to-column joints. However, the shear connection degree should be high enough in order to protect shear connectors from failure.

Abstract: This study deals with the seismic assessment and retrofitting of existing non-ductile R/C structures and the issue of selecting effective strengthening solutions is addressed. A displacement based procedure using nonlinear static pushover analyses is adopted in order to assess the main characteristics of the original structure and to select valuable retrofitting strategies. The procedure is applied to a four-storey R/C frame tested at the JRC ELSA Laboratory some years ago. The R/C frame was designed for gravity loads without specific earthquake-resistant provisions. Accurate numerical models are developed to reproduce the seismic response of the R/C frame in both the original and retrofitted configurations. The effectiveness of two strengthening techniques is examined. First, a retrofitting intervention is carried out by adding a concrete shear wall to the short bay of the frame. This solution is efficient in controlling global lateral drift and thus reducing damage in structural members. Then, a retrofitting solution involving the introduction of eccentric steel bracing is investigated in order to reduce the displacement demand and to increase the energy dissipation capacity of the frame. Nonlinear dynamic analyses are performed to assess and compare the seismic response of the frame in the original and retrofitted configurations.

Abstract: A new green sealing treatment, involving the use of bidirectional pulse power supply to the micro-arc oxidation ceramic coatings on Al substrate immersed in a solution of aluminum nitrate, has been developed. The best parameters of pulse sealing was obtained through single factor analysis and orthogonal experiment: frequency is 200Hz, the rations of positive and negative are both for 40%, sealing voltage is 80V, electrolyte concentration is 20g/L, sealing time is 30min. The polarization curve of sealing around the ceramic membrane in the mass fraction of 5% NaCl (PH=7) solution was tested. The results show that the ceramic membrane corrosion resistance after pulse sealing has been significantly improved.

Abstract: It is assumed that the physical parameters of functionally graded coating material accords with the variation of degree n polynomial, and based on this material model, the behavior of crack fracture on the interface of functionally graded coating is studied. The results show that when the functionally graded coating structure bears a tension load, stress intensity factors of mode I and mode II exist at the same time generally, and the intensity factor of mode I occupies a leading position all along. Besides, when the elastic modulus ratio of the base to the functionally graded coating top is 5 and the elastic modulus of functionally graded coating varies linearly, the stress intensity factor of interface crack is the smallest, and with the increasing of elastic modulus ratio, the optimal non-uniform parameter tends to be larger than 1.

Abstract: An experimental investigation was conducted to determine the effects of cutting conditions on surface roughness in finish hard turning of GCr15 steel with mixed ceramic inserts based on design of experiment. The influence of cutting speed, feed rate and nose radius on surface roughness was assessed using analysis of variance (ANOVA). The result indicated that the feed is the dominant factor on surface roughness followed by nose radius. Due to the complexity of machining process, artificial neural network (ANN) was employed to develop the predictive model of surface roughness. Simulations were done to describe the relationship between surface roughness and cutting parameters based on the proposed model.

Abstract: This study investigated the densification and purification properties of cold sprayed titanium coating layer by using annealing in different heat treatment environments. The annealing was conducted at 600°C/1h and three kinds of environments of vacuum, Ar gas, and 5%H2+Ar mixture gas were controlled. Cold sprayed Ti coating layer (as sprayed) represented 6.7% of porosity and 228 HV of hardness. Regardless of gas environments, all of those thermally heat treated coating layers consisted of pure α-Ti and minimal oxide. Vacuum environment during heat treatment represented superior densification properties (3.8% porosity, 156.7 HV) to those of Ar gas (5.3%, 144.5 HV) and 5%H2+Ar mixture gas (5.5%, 153.1 HV). From the results of phase analysis (XRD, EPMA, SEM, EDS), it was found that vacuum environment during heat treatment could be effective for reducing oxide contents (purification) in the Ti coating layer. The characteristic of microstructural evolution with heat treatment found to be different at three different gas environments.

Abstract: Shafts in boats and ships are important compnents, but they can fail and need to be repaired or replaced for their special working environment, and their repair accounts for about 15% to 20% of total boats and ships. According to main failure modes of shafts in boats and ships, there are thermal spraying and surfacing welding. The study of repair technology of shafts in boats and ships can promote economic development, and meet the goal of green manufacturing.