Shear Performance Of Reinforced High-strength Lightweight Aggregate Concrete Beams

Because LWAC has light-weight, high strength, good earthquake resistant performance, high durability and remarkable economic benefits characteristic, and HLWAC has more wide prospect of application on bridge engineering.So does Specified Density Concrete (SDC). Using HLWAC in the bridge upper structural can reduce the deadweight of bridge, increase the span and enhance aseismatic characteristic which bringing the huge economic benefit. So, HLWAC is one of the most desired concrete as a construction material in long-span bridge construction. But its mechanics performance studying about some problems imminently need to be solved, such as the lower elastic model, more brittle and so on. So it is necessary to study the shear capacity of reinforced high-strength lightweight concrete beams, which has the important theories and realistic meaning.In developed country, HLWAC (fcu≥60MPa) has been widely used in structural applications. But in China at present, investigations of the mechanic character of HLWAC are practically almost rare, only on low strength LWAC. The shear resistance of HLWAC is one of the problems.So, on the base of analysis of current bridge reinforcement, makes a relative system experiment research and theory analysis for the shear capacity of reinforced HLWAC beams. The objectives of this investigation are to study the shear behavior of beams, analyze the effect of different parameter on shear strength of all beams, and propose a simplified and reasonable formula to calculate the shear resistance of reinforced HLWAC beams, which provide some theory support for studying HLWAC and SDC. According to the chapter order of this thesis, this paper contains such research result as following:1. Describe LWAC advantages and its state on bridge engineering in the world, and analyze current situation of theory study on LWAC mechanical characteristic and list existing some problems of present LWAC study. On the basis of them, main emphasis and goal of this text are put forward.2. This paper introduces general situation of the test, including designing and casting the beams, material performances, previous work, testing program, loading and measuring etc.3. Through the tests of 16 specimens with and without web bars, the effect of concrete strength, stirrup ratio and shear span ratio on shear strength, shear resistance eigenvalue, and concrete shear resistance eigenvalue were researched.The experimental results indicated that the ultimate shear strength of LC and SC beams with and without stirrups increases with the increase of concrete strength and stirrup ratio. At the same shear-span ratio, the ultimate shear resistance of LC beams is lower than SC and NC beam.The ultimate shear strength of beams with and without stirrups increases with the increase of concrete strength. Correspondingly, the range of concrete strength increases, the shear strength eigenvalue decreases. When shear-span ratio is bigger, the contribution of concrete to shear capacity exhibits a post-peak behavior. This indicates that concrete continues to contribute after exhibiting the maximum shear capacity. Shear strength of concrete decreases with the increase of shear-span ratio, concrete strength and stirrup ratio.4. Analyze longitudinal reinforcement and the web reinforcement strain of different section of specimen beams, and analyze the web reinforcement strain of LC and SC beams comparatively. Research the effect of different parameter on LC and SC beams' deflection, and the diagonal crack propagation and failure mode. The experimental results indicated that the stirrups had no effect on the diagonal cracking load, but play an important role in the shear capacity of beams after cracking. Stirrup strains measured during testing were negligible up to the diagonal cracking load, moreover, the stirrups closed to the supports and load points were under compressive state. Stirrup strains were lager at mid section, but smaller at two sides. Deflection of all beams increases with the increase of shea-span ratio, but concrete strength and stirrup ratio do little to the deflection of beams. In the same situation, deflection of LC beams is larger than SC beams'. Reinforced HLWAC beam has the same failure mode as the normal-weight concrete beam. Shear failure is more abrupt and failure surfaces are smoother for high-strength LC beam.But, for SC beams, the cracks are flexuose with lots of rubble exiting between cracks.5. Based on present code JGJ12-99, recursivea analyse was conducted to the test data of this test and foreign scholar. Propose a simplified and reasonable formula is proposed to calculate the shear resistance of reinforced high-strength lightweightconcrete beams,Furthermore, the conditions of upper and lower limit for using the formula are given in this thesis.The results indicate that the test datas and calculationvalue is close perfectly.The study of the shear capacity of reinforced HLWAC and SDC beams is one comprehensive research field. There are more relevant disciplines involved, it is relatively great to study the degree of difficulty. But it is extensive that its project uses the prospect, social effects and economic effects are enormous. It is a new field that the study of the shear capacity of reinforced HLWAC and SDC beams, there are few studies at present. According the test of shear capacity of reinforced HLWAC and SDC beams with and without web reinforcement, this thesis provides a lot of contributing data and has made some achievements. A simplified and reasonable formula and the conditions of upper and lower limit for using it are proposed. The urgent need used with the deepening and project of the theoretical research, the research of this field will be deepened further.