Advanced Materials Research Vols. 163-167

Abstract: The purpose of the present study is to assess the effect of solar radiation on the development of thermal stress in hardening and hardened concrete structures. A mathematical model for solar radiation is investigated. A finite element method program is developed for the temperature and thermal stress analysis including the heat of hydration, creep, shrinkage, and ambient temperature, especially the solar radiation. Meanwhile, the effect of solar radiation on the concrete wall during its service life is considered. The results obtained from the numerical models show that for the hardening concrete wall, solar radiation reduce the stress at the first 36 hours on surface and first 48 hours in the center of the wall, after that the stresses both on surface and in the center of the wall increases quickly; for the hardened concrete wall, solar radiation increase the stress in the center of the wall. This program is useful to estimate the stress development and the effect of the solar radiation on the hardening and hardened concrete structures.

Abstract: Based on experiment of two mixed frame with SRC columns and steel beam under low-reversed cyclic loading, hysteresis behavior, ductility, energy dissipation are studied. The test results show that the mixed frame with SRC columns has better seismic performance. The nonlinear finite element analysis on the seismic behavior of the frame specimen was conducted using Openness developed by the Pacific Earthquake Engineering Research (PEER) Center. The calculated results are much coincided with the tested results.

Abstract: The excessive long-term deflections of a long span continuous girder bridge may induce vehicles to move unsafely and hazard to the bridge operation, thus to limit the development of this bridge type. In this paper the main parameters influencing the long-term deflections of a continuous rigid-frame bridge, such as pre-stressed losses, mass distribution of the box girder and Young’s modules of concrete etc., were investigated. With the establishment of the finite element model of a real bridge and the premise of describing mechanism of each parameter, detailed parameter sensitivity analysis of long-term deflections were carried out with numerical simulation method. The results of this study may help to understand the main mechanism about the long-term deflection of continuous rigid-frame bridge and provide some reference for the wide use of this type of bridges.

Abstract: Based on the geological conditions of culvert of the South to North Water Transfer Project, lining temperature field of hydraulic tunnel for crack control is simulated by finite element software—ANSYS. According to numerical analysis results of lining temperature field, considering terrain condition, structural characteristics and climate, some engineering measures are taken during construction. Internal temperature of concrete is controlled effectively, concrete crack caused by temperature changes is solved successfully, and construction quality is assured. The difference of measuring data in-situ and calculating data is very small, which illustrate that calculated model is correct and parameters are reasonable. The results can act as reference for the design and construction of similar projects later.

Abstract: Detailed formation of precast floor slab connectors has significant effect on their shear capacity, but there is no such specific provision on it at present. The effects of detailed formations on the shear strength, stiffness and deformation capacity of hairpin connectors(HPC) were studied, through numerical simulation analysis under in-plane shear force. The imbedded depth (d), slug length (h), steel plate thickness (t) and its stickout(s) were taken as parameters. The analysis results show that: ⅰ) the increase of imbedded depth can improve the bearing capacity and stiffness of HPC, but decrease the deformation capacity; ⅱ) with the increase of slug length, the HPC strength, stiffness and deformation capacity raised a lot; ⅲ) the steel plates’ thickness has small effect on the stiffness, but has strong impact on the strength and deformation capacity of HPC. ⅳ) the stickout can affect the initial stiffness and yield strength of HPC slightly, but has a considerable impact on its ultimate strength and deformation capacity. On the basis of analysis, recommendations on formation details of HPC are proposed for design and construction.

Abstract: Aiming to Ronggui Bridge (RGB) on Guangzhou-Zhuhai Intercity Rapid Rail Transit (GZIRRT), long term deformation control of long-span pre-stressed concrete continuous rigid frame bridge with ballastless track was studied. Comparing with the non-controlled deformation, extend track laying six months later after bridge construction, reserve 48 post-tensioned cables in middle spans and tension 12 external tendons after tracking laying were all effective in decreasing the long term deformation of RGB with individual application. Taking bridge construction and railway service in consideration, applying the foregoing three measures in combination, deformation of RGB 20 years later after track laying was effectively controlled within 12.8mm in the side spans and 21.9mm in the middle spans, which is less than the deformation limitation of bridges with ballastless track. The combined measure has been adopted in the actual construction of RGB.

Abstract: This paper presents a three-dimensional finite element (FE) anaytical approach for the simulation of steel-concrete composite beams. To simulate key problem, the interfacial behavior between the steel girders and concrete slabs, an interface-slip model is applied in the analysis. Both simple-supported beam experiment and continuous composite beam experiment are simulated. The load-deflection relation and the slip between the steel girders and concrete slabs as well as the strain of the steel girder and reinforcing bar in concrete are obtained from the FE analyses, and found to match well with the corresponding experimental results. The proposed nonlinear FE analysis method is capable of simulating the mechanical behaviors of steel-concrete composite beam.

Abstract: In recent years, because of rising consciousness on environmental protection and the lacking of construction waste dumping yards, recycling of construction wastes has been promoted extensively. The purpose of this study is to ascertain the effect on properties of the fresh and harden concrete replacing coarse aggregates by construction wastes under ambient and enhanced temperatures exposure. This research mainly concentrates on high performance recycled concrete (HPRC); by adding different amount of superplasticizer into the HPRC and to test and compare its mechanical and thermal properties with general high performance concrete (HPC). Thereafter, tests are carried out determine its compressive strength, residual strength after high temperature and the loss on ignition of the HPRC mixed with two water-to-cement ratios and different replacement proportions of recycled aggregates. Similar tests, such as the slump test and slump flow test, are carried out both on the HPRC and HPC. When the water-to-cement ratio is 0.3 and the amount of superplasticizer added is 1.2%, HPRC has the best performance. The specimens with 100% recycled aggregates were 31% below the control concrete sample in compressive strength at age of 28 days. By the way of adding admixture, the recycled concrete could reach the demand strength of the HPC. The results show that it is feasible to allow a higher replacement percentage of construction wastes for producing concrete products.

Abstract: The objectives of this paper are to find the strength and ultrasonic pulse velocity (UPV) of concrete adding admixtures by glass fiber and nano-clay. Residual strength and residual UPV of concrete specimens subjected to elevated temperatures are investigated. Experiment results showed that adding glass fiber and nano-clay would be beneficial for the later-age compressive strength of concrete. Adding nano-clay could considerably increase the flexural and split strength and the toughness of concrete. It is revealed that adding nano-clay could significantly maintain residual compressive and split strength of specimens after high temperature exposure. Regression analysis results revealed that the residual strength and residual UPV of concrete specimens had a high relevance after elevated temperatures exposure.

Abstract: The cyclic loading test of three steel high performance concrete(SHPC) structural walls was conducted and the failure pattern of the structural walls under the combined effect of axial force, bending moment, and shear force was researched. Based on the experimental results, the displacement-based deformation capacity design method was proposed for SHPC structural walls. It is obtained for the interrelated relationships among the ultimate drift ratio, the axial load ratio, the characteristic value of stirrup content and the aspect ratio. It is concluded that the increasing the characteristic value of stirrup content and limiting the axial load ratio were effective means to improve ductility. The characteristic value of stirrup content of SHPC structural walls with different ultimate drift ratio and axial load ratio were proposed and the conclusion can be referred by the design of SHPC structural walls.