Behavior of Steel-Concrete Composite Cantilever Box Beams under Negative Moment

Xianglin Gu,Tao Chen,Hua Li,Weiping Zhang,Hongliu Wang 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.4

Four steel-concrete composite cantilever beam specimens were tested to investigate their mechanical behavior under negative moment induced by concentrated loads at the ends of the beams. The failure modes, serviceability and ultimate bearing capacities of the composite beams with full shear connection were studied. The crack initiation and propagation were investigated with consideration of two types of shear connectors. Three kinds of longitudinal reinforcement ratios were also examined. The experimental results indicate that an increase in the reinforcement ratio is beneficial to the bearing capacity of the composite beams to some extent and that the shear stud connector is superior to the steel block connector with regards to the serviceability of the beams. Two numerical models, which were based on a concrete material model and an elasto-plastic material model, were employed to simulate the behavior of steel-concrete composite beams. The numerical calculation results show that the combination of the two models can be used to predict the longitudinal cracking load and ultimate bearing capacity of composite cantilever beams. Based on the experimental and numerical results, it was found that the ultimate bearing capacity of a steel-concrete composite beam under negative moment can be significantly affected by longitudinal cracks in the concrete slabs. An equation to predict the longitudinal cracking load of a composite cantilever beam under negative moment by concentrated load was proposed and found to have good accuracy.

Behavior of Steel-concrete Composite Cantilever Beams with Web Openings under Negative Moment

Tao Chen,Xianglin Gu,Hua Li 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.1

The effect of web openings on the mechanical behavior of composite beams under negative moment was studied through monotonically loading tests. Nonlinear finite element method based analysis was also conducted for cantilever composite beams. The test and the finite element analysis results indicated that the initial cracking loads of composite beams with web opening are lower than that without web opening. The first crack initiated from the concrete slab on the top of the opening. The beams with web opening failed due to shear failure of concrete slab upon the opening. It was also found that the load carrying capacity of beam decreases with the increase of the moment-to-shear ratio at the central line of the opening and the mechanical behavior of beam can be improved significantly by applying stiffening steel plates around the opening. To quantify the reduction of load carrying capacity, a method for calculating the load carrying capacity of beams with web openings under negative moment was derived with consideration of the interaction between moment and shear. Good consistency was obtained between the proposed method, the finite element method and the test results.

Structural analysis of high-rise reinforced concrete building structures during construction

Xiaobin Song,Xianglin Gu,Weiping Zhang,Tingshen Zhao,Xianyu Jin 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.4

This paper presents a three-dimensional finite element method based structural analysis model for structural analysis of reinforced concrete high-rise buildings during construction. The model considered the time-dependency of the structural configuration and material properties as well as the effect of the construction rate and shoring stiffness. Uniaxial compression tests of young concrete within 28 days of age were conducted to establish the time-dependent compressive stress-strain relationship of concrete,which was then used as input parameters to the structural analysis model. In-situ tests of a RC high-rise building were conducted, the results of which were used for model verification. Good agreement between the test results and model predictions was achieved. At the end, a parametric study was conducted using the verified model. The results indicated that the floor position and construction rate had significant effect on the shore load, whereas the influence of the shore removal timing and shore stiffness have much smaller. It was also found that the floors are more prone to cracking during construction than is ultimate bending failure.

Structural analysis of high-rise reinforced concrete building structures during construction

Song, Xiaobin,Gu, Xianglin,Zhang, Weiping,Zhao, Tingshen,Jin, Xianyu Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.4

This paper presents a three-dimensional finite element method based structural analysis model for structural analysis of reinforced concrete high-rise buildings during construction. The model considered the time-dependency of the structural configuration and material properties as well as the effect of the construction rate and shoring stiffness. Uniaxial compression tests of young concrete within 28 days of age were conducted to establish the time-dependent compressive stress-strain relationship of concrete, which was then used as input parameters to the structural analysis model. In-situ tests of a RC high-rise building were conducted, the results of which were used for model verification. Good agreement between the test results and model predictions was achieved. At the end, a parametric study was conducted using the verified model. The results indicated that the floor position and construction rate had significant effect on the shore load, whereas the influence of the shore removal timing and shore stiffness have much smaller. It was also found that the floors are more prone to cracking during construction than is ultimate bending failure.

Study on moisture transport in concrete in atmospheric environment

Weiping Zhang,Fei Tong,Xianglin Gu,Yunping Xi 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.16 No.5

Moisture transport in concrete in atmospheric environment was studied in this paper. Based on the simplified formula of the thickness of the adsorbed layer, the pore-size distribution function of cement paste was calculated utilizing the water adsorption isotherms. Taking into consideration of the hysteresis effect in cement paste, the moisture diffusivity of cement paste was obtained by the integration of the pore-size distribution. Concrete is regarded as a two-phase composite with cement paste and aggregate, neglecting the moisture diffusivity of aggregate, then moisture diffusivity of concrete was evaluated using the composite theory. Finally, numerical simulation of humidity response during both wetting and drying process was carried out by the finite difference method of partial differential equation for moisture transport, and the numerical results well capture the trend of the measured data.

Mesoscale model for cracking of concrete cover induced by reinforcement corrosion

Junyu Chen,Weiping Zhang,Xianglin Gu 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.22 No.1

Cracking of concrete cover induced by reinforcement corrosion is a critical issue for life-cycle design and maintenance of reinforced concrete structures. However, the critical degree of corrosion, based on when the concrete surface cracks, is usually hard to predict accurately due to the heterogeneity inherent in concrete. To investigate the influence of concrete heterogeneity, a modified rigid-body-spring model, which could generate concrete sections with randomly distributed coarse aggregates, has been developed to study the corrosion-induced cracking process of the concrete cover and the corresponding critical degree of corrosion. In this model, concrete is assumed to be a three-phase composite composed of coarse aggregate, mortar and an interfacial transition zone (ITZ), and the uniform corrosion of a steel bar is simulated by applying uniform radial displacement. Once the relationship between radial displacement and degree of corrosion is derived, the critical degree of corrosion can be obtained. The mesoscale model demonstrated its validity as it predicted the critical degree of corrosion and cracking patterns in good agreement with analytical solutions and experimental results. The model demonstrates how the random distribution of coarse aggregate results in a variation of critical degrees of corrosion, which follows a normal distribution. A parametric study was conducted, which indicates that both the mean and variation of critical degree of corrosion increased with the increase of concrete cover thickness, coarse aggregates volume fraction and decrease of coarse aggregate size. In addition, as tensile strength of concrete increased, the average critical degree of corrosion increased while its variation almost remained unchanged.