Reported test results of reinforced concrete beams made with coarse recycled concrete aggregate have been re-analysed using strut-and-tie models and the efficiency factors of the recycled concrete aggregate concrete bottle-shaped struts compared with those made of natural coarse aggregate. The objective was to ascertain whether strut-and-tie model provisions for efficiency factors of bottle-shaped struts in current design codes and the recent literature, originally meant for natural coarse aggregate concrete, can be conservatively applied to recycled concrete aggregate concrete, or not. The results of the re-analysis indicate that the efficiency factors of the natural coarse aggregate as well as the recycled concrete aggregate concrete bottle-shaped struts were comparable and conservative when benchmarked against the predictions of CSA A23.3-04 and an efficiency factor model proposed by the authors. However, both ACI 318-08 and Eurocode 2 gave unsafe efficiency factor predictions for the recycled concrete aggregate as well as the natural coarse aggregate concrete bottle-shaped struts under investigation. This is attributed to the insensitivity of these two codes to strut inclination with adjoining tie(s) and does not per se indicate any inherent inferiority as far as recycled concrete aggregate concrete is concerned. This investigation indicates that recycled concrete aggregate concrete bottle-shaped struts can be designed using the efficiency factors recommended for natural coarse aggregate concrete bottle-shaped struts in CSA A23.3-04.
The cohesion coefficient of structural concrete made with recycled concrete coarse aggregate (RCA) was evaluated independently for the first time, through push-off tests having no clamping force across the shear plane, and compared with the cohesion coefficient of structural concrete made with natural coarse aggregate (NCA). Both conventionally compacted and self-compacting concretes were made with RCA and NCA as coarse aggregates. To achieve the best structural quality, concretes made with RCA were proportioned based on the equivalent mortar volume (EMV) principle instead of percentage replacement of NCA with RCA commonly followed in most of the earlier studies. Twelve transversely unreinforced push-off specimens, three from each of the four varieties of concrete, were tested to failure. Cohesion coefficients determined from analytical and finite-element modelling of the push-off tests were found to be in close conformity with each other, and the experimentally found cohesion coefficients were reasonably close to, though not in exact conformity with, the theoretical values. Nevertheless, the experimental results clearly established that RCA concrete when proportioned by the EMV method is not inferior to NCA concrete in terms of cohesion contribution to shear strength.
Structural health monitoring (SHM) is an inevitable component of modern civil and aerospace structures. It essentially detects the damages in the system by evaluating the performance parameters by the integration of sensing and possibly also actuation devices into the structure. In this paper damage detection process in an aluminium cantilever plate using piezoelectric sensors and actuators is simulated. Possible root damage such as transverse crack and longitudinal crack are studied. The results are compared with undamaged case. The plate is actuated using PZT actuators and performance is evaluated using PVDF sensors. Modelling for PZT/PVDF and structural parts are carried out using coupled field finite element PLANE223 ofAnsys(TM) finite element package. Strain response at the root of the cantilever plate is captured as the voltage output of the PVDF sensor. Strain response is directly related to the voltage generated in the PVDF sensor. The percentage variation of the fundamental frequency is found to be less than 3% in the present study and hence it is not taken as an index of damage. The transient voltage response captured with the transient coupled field analysis shows variation up to 24% as a signature between damaged and undamaged systems. Therefore, the present study suggests transient response evaluation using PVDF sensor is a suitable evaluation technique for the cases under consideration.
ABSTRACT. In this paper, we study some properties of ultraconnected spaces and show that ultraconnected T spaces are maximal ultraconnected and minimal T We also introduce the notion 2 of F-connected spaces, topological spaces wich are bothNyperconnected and ultraconnected and characterize compact maximal F-connected topologies on a set.
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