Current Issue : April - June Volume : 2020 Issue Number : 2 Articles : 5 Articles
A static loading test was carried out on a 1/3-scale concrete-filled square steel tubular column-steel beam frame (CFSTSBF)\nspecimen with 2 spans to study its progressive collapse behaviors under the middle column failure scenario using the alternate\nload path method and to examine the failure mode and load transfer and main resistance mechanisms of the residual structure.\nThen, theoretical models of the specimen, involving the whole collapse process, were developed, and the resistance and deformation\nrelationships of each model were calculated and validated with test results. The results indicated that the specimen\ncollapse process includes the elastoplastic stage, plastic stage, transfer stage, and catenary stage, the beam mechanism and catenary\nmechanism were the principal mechanisms for the structure against progressive collapse, and catenary action can significantly\nstrengthen structural resistance. The modified theoretical models with higher practical accuracy could be used to assess structural\nperformances against progressive collapse....
In the past, earthquakes have caused significant damage to traditional masonry filler wall frame structures. To solve this problem, a\nnew design scheme, the partition damping filler wall, is proposed in this paper to reduce the interaction between the filler wall and\nthe frame structure. Low cyclic loading tests are carried out on the traditional and the new masonry filler wall frames. Besides, one\nfull-scale-angled span layer frame without a filler wall is produced for comparison analysis. The mechanical performances of the\ndifferent frames are studied, including the characteristics of the deformation failure modes, hysteretic curves, skeleton curves,\nrigidity degeneration, energy dissipation capacity, and the lateral displacement of the frame columns. The research results show\nthat the partition damping filler wall can significantly decrease the diagonal bracing effect of the filler wall on the steel frame.\nMeanwhile, the setting of the low-strength mortar between the filler wall and steel frame and the arrangement of the damping layer\ncan improve the stress distribution and delay the crack development of the wall. Furthermore, the stiffness degradation rate of the\npartition damping filler wall is obviously slower than that of the traditional masonry filler wall frame structure. In this paper, the\npartition damped wall-filled frame structure shows outstanding ductility and deformation capacity....
We present a new feasible theory about how the ancient Egyptians moved and\nlifted heavy stones and how they built the Great Pyramid of Giza around 2500\nBC, from the viewpoint of energy management taking account of the vast\nquantity of the stones needed for the Pyramid. We give our solutions to the\nfollowing three mysteries of the Pyramid: 1) How they could overcome the\ndifficulty in making the four straight edges of the Pyramid meet in one point,\nhigh up in the sky? 2) Why all of chambers and passages (the Kingâ??s and the\nQueenâ??s chambers, the Grand Gallery and other passages), except the Subterranean\nchamber, are away from the central axis about seven meters eastwards?\n3) For what purpose they dug the Subterranean Chamber, thirty meters\ndeep?...
In recent years, lime mortars mixed with artificial or natural pozzolans are commonly\nused in restoration applications. The aim of this work is the assessment of carbonation, pozzolanic\nreaction, setting time, and mechanical properties of metakaolinâ??lime mortars mixed with crystalline\nnano-titania (nT) as additive. The studied mortars consist of hydrated lime and metakaolin in\n60/40 ratio (wt%) and fine aggregates of either carbonate or silicate sand. The concentration of the\nnano-titania is equal to 6 (wt%) of the binder. For comparison purposes, three types of mortars\nand pastes are designed: Without the addition of nano-titania, with nT activated or not under UV\nirradiation. The evaluation of the carbonation and pozzolanic reaction over a 1.5-year curing period\nis carried out through thermal analysis (DTA/TG), infrared spectroscopy (FTIR) and X-ray diffraction\nanalysis (XRD). The uniaxial compression and the three-point bending tests at 28 days, 3 months, and\n6 months were carried out to evaluate mechanical properties. The addition of activated nano-titania,\ndue to an increased photocatalytic activity, accelerated the setting of the mortars, improving at the\nsame time the mechanical properties. The plastic behavior of the limeâ??metakaolin mortars with\nactivated nT was attributed to the evolution of carbonation and pozzolanic reaction....
Retaining a waterproof coal pillar is the most effective water conservation method for coal seam mining close to a reservoir, and\ndetermining a reasonable width for the waterproof coal pillar has been a common problem among mining scholars for a\nconsiderably long time..................................
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