Experimental Research On Seismic Behavior Of Reinforced N-block Masonry Shear Wall

N-block masonry wall is a kind of masonry wall with the feature of fully aligned web-shells. It is recognized that cracking, water seepage and other engineering problems have been effectively mitigated by this kind of masonry wall, which has broad prospect of application. However, experimental research on its mechanical behavior is still few. Based on construction technology research subjects of Hunan Province - Experimental Research on Seismic behaviors of Reinforced N-block Masonry Shear Wall, and previous research achievements on block masonry, the basic mechanical performance of N-block masonry prism and the seismic performance of reinforced N-block masonry reinforced shear wall has been researched and analyzed.Through tests of 18(6 ungrouted and 12 grouted) block masonry specimenson compressive behaviors, failure shape, cracking load, ultimate capacity and deformation capacity of concrete block masonry were analyzed. Test results showed that,comparing with common concrete block masonry, due to special sectional geometric shape of N-block, the web-shell of N-block masonry exhibited favorable aligned ratio, the compressive behavior of it was better improved, and no matter whether it is grouted, cracking load, compressive strength and elastic modulus of N-block masonry had been enhanced. Based on the compression mechanism of N-block masonry, a theoretical calculation formula and an experiential formula are both presented for ungrouted N-block masonry. A semi-empirical and theoretical formula of compressive strength is also presented for grouted N-block masonry. And results calculated by the formulas were in good agreement with the test results. According to the test data of stress and strain, the stress-strain curve and modulus had been fitted, and the corresponding numerical expressions were also presented. Via the experiments of 30(6 ungrouted and 24 grouted) shear specimens on shear performance, the shear failure characteristics of N-block masonry were studied.According to the phenomenon of the shear tests, its shear failure mechanism was analyzed, and beam-type shear resistance model of core column concrete was established. Under the comprehensive consideration of the favorable restriction effect of external block on the core columns, relevant shear resistant formula of grouted N-block masonry was established, and results calculated by the formulas compared well with the test results. Through experimental researches of two reinforced N-block masonry shear walls under the action of the lateral cyclic load, the ultimate strength, the initial stiffness, stiffness degradation curve, ductility and cracking angle and so on which all were indexes of seismic performance had been preliminarily investigated. Test results indicate that reinforced N-block masonry shear wall possesses higher ultimate bearing capacity comparing with ordinary concrete block masonry shear walls, and when axial compressive stress is lower, bending failure with good ductility is more inclined to happen. The magnitude of vertical compressive stress and the quantity of horizontal steel and the quantity of vertical steel were three main factors which affected the ultimate strength and failure mode of the reinforced N-block masonry shear wall. In the design of wall, the interrelation of the three factors should be simultaneously considered to satisfy the requirement of strong shear weak bending, in order to achieve bending failure of the wall with good ductility.According to requirements of scientific research and experiments, with the combination of the research subject of 985 project, this paper had also developed a electro-hydraulic servo actuators for cyclic loading which possess the maximum load capacity of 1500kN and displacement measurement capacity of 500mm (±250mm). The entire designing and producing process of the whole loading system was detailed in this paper, and an practical operational control procedure and the corresponding control steps were also given in this paper. Comparing to electro-hydraulic servo actuators-MTS, its accuracy had been validated through the experiments of reinforced N-block masonry shear wall. Practice demonstrated that this loading system was manipulated conveniently and exhibited good performance.