Papers by Keyword: Reinforced Concrete (RC)

Abstract: Based on double-K fracture model, adopt three-point bending beam which has been recommended by RILEM, the fracture properties of three groups reinforced concrete beams were studied. Refer to the relevant literature, fracture parameters of reinforced concrete three-point bending beams are examined. Through the analysis of whole process of crack propagation of reinforced concrete three-point bending beams, the results show that the reinforcement ratios can't preventing the cracking effectively, but can increase the maximum loads, thus improving the relative toughness; the precritical crack propagation length relative values show a linearly increasing trend with the increase of reinforcement ratios; the initial fracture toughness is not affected by the reinforcement ratios, but the unstable toughness has little effects by the reinforcement ratios.

Abstract: In order to reveal the damage characteristics of internal explosion, the internal explosion of closed RC structure under incremental charges manner until structural damage are simulated by LS-DYNA code. The weight changes of charge influence on structure damage and distribution law of characteristic parameter of shockwave on the typical position are also discussed in this paper. The results show that, the distribution of shockwave overpressure on the walls under different weight of charge obey three kinds of linear laws as following: affected by one wall, two walls and three walls, respectively. The distributions of impulse on the walls under different weight of charge obey their distribution curve respectively when the structure is undestroyed, but the impulse will deviate from the distribution curve when the structure is destroyed. And the damage situation of RC structure under internal explosion is graded。

Abstract: Coupling beam, the first line resisting earthquake, is directly related to the overall performance of the shear wall structure. Using the large general finite element analysis software ANSYS, the coupling beam span-depth ratio is 2~3 different reinforcement scheme in finite element analysis. Analysis on the ductility performance of reinforced concrete coupling beams in shear wall structure in three fields: the concrete strength grade, the longitudinal reinforcement ratio and the stirrup ratio, provides a basis for the design of the structure and to provide a reference for similar studies.

Abstract: Along with our country economy fast development, the building and renovation is becoming more and more widely, layer for steel structure system, relying on its obvious advantages, has gradually become one of hot topics in the study of engineering. Combining with engineering example, through the integrity research, bearing capacity calculation, field exploration, the analysis of the concrete strength testing, etc., has carried on the appraisal on the safety of building structure, and analyses the feasibility of after add layer. In layer for steel structure design, at the same time puts forward the design and construction of some key points, provide a reference for similar projects.

Abstract: The safety and load-bearing capacity of an in-service urban reinforced concrete slant leg rigid frame bridge over railway is assessed by field testing and finite element analysis. The bridge is located in Qitaihe city, the northeastern of China. The two heavy trucks and three different loading test configurations are used in experiment. The three load figuration is set up and performed based on the result of technical condition investigation and finite element numerical analysis. The vertical displacement and key section strain response are recorded during experiment. Loading-bearing capacity and safety performance of the bridge is analyzed and evaluated according to measured data combining with numerical analysis. The testing result shows that structural stiffness and strength of the bridge do not satisfy the requirements of the original design. Based on the assessment result, some proposals are proposed to the management office. A moderate maintenance and reinforcement treatment should be carried out for this bridge to improve the bearing capacity and ensure safety operation. Before that completed some traffic control measures should be taken to avoid aggravating diseases and damages of the bridge due to passing heavy vehicle.

Abstract: Corrosion of reinforcement steel is a major factor affecting the deterioration of reinforced concrete structures. During corrosion, steel undergoes several phases of chemical reactions with consequent variation in steel section geometry and mechanical properties. At ultimate corrosion stage, the effective cross section area of steel is reduced with equivalent decrease in load carrying capacity leading to unsafe structures. During initial phase of corrosion, chemical reactions generate new products which irregularly increase steel bar diameters. The resulted products induce additional stresses on the structural member, causing cracking and spalling of the concrete cover, and subsequently faster deteriorate the member strength. This paper presents the effect of the induced stresses of corrosion products on concrete cracking experimentally and numerically. Experimentally several pull-out specimens were tested to identify the effect of corrosion at different stages, and, numerically, a two dimensional finite element model was developed to study the crack initiation and propagation in concrete using nonlinear analysis and specific properties for both steel and concrete elements.

Abstract: The subject of this paper is option analysis of the use of geopolymers as matrixes to repair mortars designated for rehabilitation of reinforced concrete structures. Due to their specific properties, geopolymers show a high potential mainly for special applications. Rehabilitation of reinforced concrete structures exposed to extreme conditions is a field in which it is possible to effectively take advantage of geopolymers ́ exceptional properties. In this particular case, we focus on comparing the behaviour of polymer-cement materials commonly used in the rehabilitation of reinforced concrete structures and the one of geopolymer-based mortars.

Abstract: Reliable assessment procedures of existing RC buildings are currently available, and have been introduced in the Italian and European codes reporting new rules for seismic analysis. However, further studies are required in order to further improve such procedures and, specifically, obtain more accurate data on the behavior of beam-column joints, whose role on the global behavior of framed RC buildings can be crucial. Until now studies on this issue have been mainly devoted to joint specimens with stiff beams, however frame structures having wide (also called flexible or flat) beams are widely used in the European residential building stock. To this purpose, given the lack of knowledge, an experimental investigation on full scale beam-column joints with wide beam has been planned and is currently in progress. In the present paper the main results of three tests are reported and discussed. The role of different earthquake resistant design levels on joint performances is pointed out.

Abstract: Reinforced Concrete (RC) Hollow Slab Girder is widely used in Highway Engineering, and fatigue load is an essential aspect of causing damage. In order to accurately calculate the distribution and development laws of RC hollow slab girder fatigue strain, experiment on Amplitude fatigue with five experimental beams were done in the laboratory. The beams obviously presented a rule of three stages: the damage development is fast in fore period and later period; but the hazard from fatigue in the midterm developed steadily relatively. The destruction of fatigue damage is the steel brittle fracture. Fatigue failure could be divided into three periods: rapid development stage, stable stage and destruction stage. In last stage one or two main cracks continues to expand, the rest stop growing and gradually closed, it fatigue fractured at the main crack. With the increase of the number of cycles of fatigue loading, the growth rate slowed down into a relatively stable stage, when approaching destruction there is relatively substantially growth.

Abstract: This paper investigates the mechanical properties and the fire resistance of steel-polypropylene hybrid fiber-reinforced concrete. The type of the polypropylene fibers are polypropylene monofilament fiber, polypropylene fibrillated fiber, and macro polypropylene fiber, and the type of the steel fibers is hooked steel fiber. The experimental results show that the compressive strength, splitting tensile strength and flexural properties of steel-macro polypropylene hybrid fiber reinforced concrete are better than any others. And the fire resistance of steel-monofilament polypropylene hybrid fiber reinforced concrete is the best.