Behavior Study of High Impact Resistant Reinforced Concrete Frames Using Crack Conduction Method
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In this study, the influence of crack conduction method on behavior of reinforced concrete (RC) frame under iterative high impact loading were experimented. To investigate the structural behavior through large deformations and progressive damage and to identify the failure modes, the falling weight and falling height were set more than the structural strength in elastic state. A comprehensive scheme which indicated influence of location of initial cracks on behavior and failure mode of structure was developed. Falling weight impact test was conducted on twenty-one laboratory scaled RC frames which were categorized in four series regard to considered scheme. Concrete volume and compressive strength, number of longitudinal and transverse rebar were constant factors in all specimens. Deformed shape and crack patterns, developed on the side surface of the RC frames, were sketched and total deflections vs. cumulative input energy of the RC girder were plotted. The results revealed the influence of crack conduction on improving the structural behavior and extending the endurance of RC frames against iterative high impact loading.Keywords:
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Recently, rebar anchor plate has been widely used in the project, which solve the rebar anchor problem and improve the construction quality. This paper introduced the rebar mechanical anchorage technology background, research content and progress, and rebar anchor plate application, which would offer the guidance and reference for the designers and constructors.
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在它被嵌进水泥和钝化以前，钢 rebar 通常形成氧化物或生锈的皮肤这皮肤的性质将被温度重重地影响。到在不同表面下面的钢 rebar 的钝化性质上的温度的效果调节的学习，我们进行了扫描电子显微镜学(SEM ) 观察和电气化学的大小，例如免费腐蚀的大小，潜力和极化 HPB235 钢 rebar 弯。这些大小识别了三种表面：擦亮，氧化物皮肤，和生锈的皮肤。我们的结果证明所有表面类型的钝化性质随温度的增加减少。温度在擦亮的钢 rebar 上在生锈皮的 rebar 和最少的效果上有最大的效果，因为钢 rebar 鈥檚 表面上的工厂规模上的裂缝和缝隙。因为缝隙腐蚀能加速钢 rebar 的腐蚀，生锈皮的 rebar 展出最高的腐蚀率，特别地在高温度。结果也显示为氧化物皮 rebar 和生锈皮的 rebar 的钝化的阀值温度分别地是 37 掳 C 和 20 掳 C。
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Headed rebar is an assembly composed by steel plate and rebar.Based on ANSYS software,the force mechanism for headed rebar was researched.The development length for headed rebar in relevant codes of China and America was compared and analyze,recommended value for development length was given.Relying on a nuclear power project,the amount of tie bar for Auxiliary Building and Shield Building was counted.And the economic performance and feasibility of substituting rebar with hook by headed rebar was researched.The results show that: substituting rebar with hook by headed rebar in engineering structures is feasible with good safety and economic performances.It can be popularized in various kinds of projects.
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The rebar detailing is an important work influencing the final performance and quality of RC structures. But it is one of the most irrational and illogical activity in construction site. Many groups of workers, including main contractors, structural engineers, shop drawers, rebar fabricators, and etc., participate in this activity. A loosely-organized process for this activity is apt to produce a big amount of rebar loss or even degraded structures. A 3-dimensional rebar auto-placing system, called as Rebar Hub, has been designed and implemented in this research. Rebar Hub provides a totally integrated service from 3D structural modeling of buildings to rebar auto-placing considering anchorage, splice, and the length of ordered rebar. In addition, Rebar Hub can recognize the 2D drawing CAD files and then build 3D structural models which are used for the start point of 3D rebar auto-placing. After rebar auto-placing, each members of the 3D structural model have rebar information belonging to them. It means that the rebar information can be used for the afterward works such as quantity-survey, manufacturing and fabrication of rebars. Rebar Hub is showing outstanding performance while applying to practical projects. It has almost five times productivity and reduces the rebar loss up to 3～8% of the initially-surveyed amount of rebar.
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Electrochemical experiments were used to study the passivation behavior of the steel rebars with polished surface,oxide skin and rusty skin in simulated concrete pore solution.The results indicated that after the corrosion potential became stable,the steel rebar with nude surface had the highest potential while the steel rebar with rusty skin had the lowest potential.With the decrease of solutions' pH value,the passivation of the three kinds of rebar decreased.The passivation of nude surface steel rebar and oxide skin rebar was apparently better than that of rusty skin rebar.The threshold pH values for polished steel rebar,oxide skin rebar and rusty skin rebar were 11.2,11.0and 12.4,respectively.With the increase of chloride ion concentration,the passivation property of the three kinds of rebar decreased.The passivation of rusty rebar was apparently worse than that of nude surface rebar and oxide skin rebar.The threshold of chloride ion concentration for polished steel rebar,oxide skin rebar and rusty skin rebar were0.03mol/L,0.03mol/L and 0.01mol/L,respectively.
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Бұл зерттеужұмысындaКaно моделітурaлы жәнеоғaн қaтыстытолықмәліметберілгенжәнеуниверситетстуденттерінебaғыттaлғaн қолдaнбaлы (кейстік)зерттеужүргізілген.АхметЯссaуи университетініңстуденттеріүшін Кaно моделіқолдaнылғaн, олaрдың жоғaры білімберусaпaсынa қоятынмaңыздытaлaптaры, яғнисaпaлық қaжеттіліктері,олaрдың мaңыздылығытурaлы жәнесaпaлық қaжеттіліктерінеқaтыстыөз университетінқaлaй бaғaлaйтындығытурaлы сұрaқтaр қойылғaн. Осы зерттеудіңмaқсaты АхметЯсaуи университетіндетуризмменеджментіжәнеқaржы бaкaлaвриaт бaғдaрлaмaлaрыныңсaпaсынa қaтыстыстуденттердіңқaжеттіліктерінaнықтaу, студенттердіңқaнaғaттaну, қaнaғaттaнбaу дәрежелерінбелгілеу,білімберусaпaсын aнықтaу мен жетілдіружолдaрын тaлдaу болыптaбылaды. Осы мaқсaтқaжетуүшін, ең aлдыменКaно сaуaлнaмaсы түзіліп,116 студенткеқолдaнылдыжәнебілімберугежәнеоның сaпaсынa қaтыстыстуденттердіңтaлaптaры мен қaжеттіліктерітоптықжұмыстaрaрқылыaнықтaлды. Екіншіден,бұл aнықтaлғaн тaлaптaр мен қaжеттіліктерКaно бaғaлaу кестесіменжіктелді.Осылaйшa, сaпa тaлaптaры төрт сaнaтқa бөлінді:болуытиіс, бір өлшемді,тaртымдыжәнебейтaрaп.Соңындa,қaнaғaттaну мен қaнaғaттaнбaудың мәндеріесептелдіжәнестуденттердіңқaнaғaттaну мен қaнaғaттaнбaу деңгейлерінжоғaрылaту мен төмендетудеосытaлaптaр мен қaжеттіліктердіңрөліaйқын aнықтaлды.Түйінсөздер:сaпa, сaпaлық қaжеттіліктер,білімберусaпaсы, Кaно моделі.
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Abstract This study investigated the effectiveness of several types of adhesives used in post-installed rebar connections as a bonding agent between steel reinforcement bars and old concrete under pull out test. The experimental samples were; cylindrical samples of (150 mm dia. × 300 mm high) with anchors rebar of varying diameter (12 and 16 mm), different embedded length (100 and 150) mm with different holes’ diameters. The strategy of control were cast-in-place rebar concrete specimens while other samples are post-installed rebar concrete specimens of varied chemical adhesives as bonding agents, namely KUT EPOXY ANCHOR ‘NS’ and SIKAFLOOR169. The output showed that the different adhesives yielded closed pull-out load values. It is found that the pull-out capacity (bond strength) is increased by increasing the embedded length, the diameter of the rebar and slightly with the diameter of the hole. In addition, the failure mode of post-installed rebar concrete was governed by the embedded length and the area of contact with the adhesives. On the other hand, the larger diameter of rebar favors splitting or failure of concrete due to higher strength in binder-rebar interface compare to the binder-concrete interface. The results showed that the pull-out load was increased by (26 % and 32 %) as the rebar diameter increased from 12 mm to 16 mm for KUT “NS” and SIKAFLOOR respectively. The hole diameter had slightly effect of the pull out load where the average of increment was only 6 %. Finally, the bonding strength is considerably depended on the embedded length and less affected by the type of epoxy.
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Aimed at difficulties arising in obtaining the stress at a certain point in bonded rebar system,this paper introduces the use of the finite element software ANSYS to establish the finite element model for bonded rebar,by which the mechanical behavior of bonded rebar of different anchorage depth is analyzed under the same load level and the different load level respectively.The analysis shows that whether the load is of the same level,both the von mises stress distribution of the concrete and the rebar tend to increase gradually from bottom to top in the bonded rebar system,and the maximum of the von mises occures at the bonded rebar orifice;the maximum of the von mises in concrete tends to decrease,with the increase of the anchorage depth.The destruction form of the bonded rebar was influenced not only by the anchorage depth,but also by the yield strength of the rebar and the extent of concrete was constrained.This study provides the reference for design and construction of the bonded rebar.
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