Abstract:The previous studies find that the hollow spherical joint stiffness has a certain influence on seismic response of single-layer cylindrical reticulated shell. In order to analyze the rule of this influence with PGA (peak ground acceleration) changing, two types of finite element models are built. The two types of models have the same size except the spherical joint. The first type is a fine model built by shell element and its spherical joints and tubes are built by considering the real size; the other type is the common model which is built by beam element, and the spherical joints are neglected. Comparing with the seismic response of the two types of models when PGA changes, the results show the difference between the two types of model in node displacement-time curves is increased as PGA increases; when the PGA is larger than the collapse acceleration of structure, the influence of increasing joint wall thickness on improving the structural capacity of anti-stability is decreased as PGA increases.

Abstract:The seismic resistant performance and failure mechanism of the steel bracing Bound-Column were analyzed with tests and the finite element method. Two-story steel bracing Bound-Column test specimen was selected. The braces adopt long leg back-back double angle. Tests were divided into three groups, including one monotonic loading test and two cyclic tests. Lateral load-bearing capacity, stiffness and hysteretic behavior of the steel bracing Bound-Column were obtained by the comparison of test results and the finite element method. Results show that the steel brace of Bound-Column contributes a lot to its load capacity and stiffness, while the external frame provides little lateral rigidity and capacity. Bound-Column failure occurs only in the steel braces, while the external frame is with no damage.

Abstract:Pseudo-dynamic tests and low cyclic reversed loading tests on two-floor coupled shear wall planar structures were conducted, and one is arranged with two steel truss coupling beams, the other is arranged with a steel coupling beam and a RC coupling beam. The shear walls’ seismic response under different earthquake intensity was deliberated, Their failure mechanism, bearing capacity, hysteretic ductility, energy dissipation mechanism, and stiffness and strength degradation mechanism were analyzed as well. The results show that the shear wall with two steel truss coupling beams has reasonable stiffness distribution. Its energy dissipation mechanism, stiffness and strength degradation mechanism can fulfill the demands of coupled shear wall’s seismic design: under rare earthquake, it can maintain good bearing capacity and stiffness, and keep restraining the walls. Its seismic performance is superior to RC coupling beams-coupled shear wall system.

Abstract:An improved splice method for mid-diameter steel bars (10-16mm) used in RC structures was developed, which can make the installation more easily and economic through the hybrid connection of welding and overlapping. In order to study the mechanical behavior of welding-overlap splices, a total of 138 steel bar splice tests were conducted, including both the steel-concrete interaction group and the lonely-steel group. Through the splice tensile experiment, the failure model and ultimate strength of the improved splice was summarized. Meanwhile, the failure mechanism was analyzed by the FEM analysis. The test results show that: hybrid connection of welding and overlapping is a simpler splice method which can realized the reliable splice in the RC structures, the ultimate load of the improved splice is sufficient for the application and the failure model is reasonable. Base on the test results, some suggestions for application were given. The economic analysis of a real application case is conducted, which shows a good prospect of proposed connection.

Abstract:The static tests on hybrid fiber (steel fiber and polypropylene fiber) reinforced high performance concrete deep beams according to the orthogonal experimental design were conducted. The shear capacity and calculation method of deep beams were discussed as well. The contributory factors such as the characteristic parameters of steel fiber (types, volume fraction, aspect ratio), the volume fraction of polypropylene fiber, the ratio of web horizontal reinforcement and the ratio of web vertical reinforcement were analyzed. Results show that the shear failure mode of deep beams is changed with adding a reasonable volume of hybrid fibers, and hybrid fiber can greatly increase the diagonal cracking strength and shear strength of HPC deep beams. The diagonal cracking strength is increased by 45.2% averagely while the shear strength is increased by 25.6% averagely. A satisfied result is obtained when the plasticity theory is used to analyze shear behavior of hybrid fiber reinforced HPC deep beams. The contribution of web horizontal reinforcement and web vertical reinforcement to shear strength of deep beams is not obvious but the former plays a major role. After analyzing the strengthening mechanism of hybrid fiber, a formula to calculate the shear capacity of hybrid fiber reinforced HPC deep beams is presented based on spatial strut-and-tie mode and splitting failure.

Abstract:In order to improve the deformation capacity and damage tolerance of the reinforced concrete columns, six reinforced concrete column specimens with fiber reinforced concrete (FRC) in the bottom region instead of ordinary concrete were tested under reversed cyclic lateral loading. The specimens’ shear span ratio is three and its configuration of stirrups are relatively few. The test results show that these columns exhibit shear failures after the longitudinal reinforcement yielding, and they have better deformation capacity and damage tolerance. The column with FRC in the bottom region can reduce the amount of constraint stirrup and shear stirrup. According to the test results, bending bearing capacity calculation method considering FRC tension action and shear capacity formula were established. The shear capacity calculated by the adopted formula are in good agreement with the test results.

Abstract:To analyze the applicability of the direct design method to the box-filler hollow floor, 224 specimens of cast-in-situ box-filler hollow floor and solid floor supported by columns were computed by ABAQUS. Both a hollow core floor and the corresponding solid floor were analyzed and the section moments were achieved. Then parametric analysis of the hollow floor was carried out. The column size ratio, hollow ratio, span ratio, beam relative flexural stiffness and beam relative torsional stiffness were all considered as analysis parameters. The first-round and second-round moment distribution coefficients in both interior and edge panel were obtained. The results show that: for the hollow floor and solid floor, the moment distribution in interior computational strip and edge computational strip are similar, the difference of moment distribution mainly lies in the positive moment. When the span ratio≤1.0 and the column size ratio≤0.2, the impact caused by support size can be ignored; There is still a relatively large gap between calculated value in moment distribution coefficient and codes in some part of the critical sections, some coefficient must be adjusted. From the analysis results, the first-round and second-round moment distribution coefficient tables were presented for research and engineering design.

Abstract:Under the equipotential premise gradient, anode follow-up technical was proposed in the electro-osmosis reinforcement of soft clay. Eight electro-osmosis contrast tests were conducted through the experimental test. Currently, shear strength, displacement, moisture content, pH, conductivity of the soil and other indicators were monitored in the electro-osmosis test. Different electro-osmotic reinforcement effects were analyzed. The results show that: when the anode follow-up is used, the first anode follow-up can get a most significant effect. When the current density is high, arranging the anode follow-up will lead some extent reduce of the effect of the electro-osmosis, while the effect will be promoted when the current density is low. By carrying out the anode follow-up on the cathode region soil, a significant reinforcement effect can be obtained. Anode follow-up can reduce the resistance of the circuit in the anode region and effectively promote the electro-osmosis reinforcement effect.

Abstract:By using servo control shear loading system, specimens with non-coplanar rock-like intermittent joints were tested by the way of forward and reverse direct shear, rupture mechanism and shearing law for rock bridge with non-coplanar intermittent joints were studied under direct shear. The experimental studies showed that five apparent stages are presented in the process of rock bridge rupture under direct shear, which are linear elastic stage, initiation and extension of crack, fracture and transfixion of rock bridge, climbing and occlusion of shear plane and residual friction. Rock bridge presented profile fracture plane under forward direct shear. While under reverse direct shear, band form fracture plane is showed which penetrated along with the direction of forward shear, and the shear strength of initiation and peak shear strength under reverse direct shear are bigger than that under forward shear. Crack angle, normal stress and lap proportion among adjacent joint are the main factors that influence the initiation strength and peak shear strength. The FLAC 3D simulation for the process of non-coplanar intermittent joints rock bridge rupture and formation of shear rupture surface under forward and reverse direct shear was conducted. The results of numerical simulation agreed well with those of experiment. The simulation results revealed tension crack failure of non-coplanar intermittent joints rock bridge and shear yielding mechanism of fracture plane.

Abstract:In order to get the wave loads on pile groups with slab merged in water, an engineering approach was proposed. Three coefficients in terms of slab effect were discussed and a time -domain analysis of wave forces acting on piles was conducted. Wave diffraction from a slab was obtained by the potential theory and eigenfunction expansion method, while wave loads on piles were evaluated by Morison formula. The wave force on pile obtained by the proposed method and the numerical simulation are in good agreement, which shows a good reliability of the proposed method. The result shows that, owing to the size of slabs, there exist some differences in the changing rule of slab effect varying with the submerged depth. The resultant force decreases with the rise of incident wave number, and the changing trend of its acting point appears an inflection point at some wave number. The minimum force acting on piles lies in the meeting-wave side of the slab, while the maximum one arises at the back side or in the scope of 30 degrees between the axis of slab, which is perpendicular to the incident wave, and the back side. The presence of slab causes the deflexion and phase difference of inline force. Meanwhile, the grouping piles coefficient can be taken as 0.7.

Abstract:In order to investigate the issue in the field of the application of CFG pile application of CFG pile composite foundation technology in deep embedded secret passage of such special structure ground treatment, the settlement deformation of CFG pile composite foundation according to deep are studied and detailed analysis are given in the field test and indoor model test of the gravel cushion with different thickness. Moreover it points out that the cushion compressive deformation must be taken into account, and that the settlement deformation calculation cannot simply consider the amendments of composite foundation. The amendments of cushion deformation must be considered. The effect of the different thickness of cushion on pile-soil stress ratio, total settlement of composite foundation, cushion compression and axial stress of pile body were analysed by using ABAQUS finite element method. Through the analysis of the field test, indoor model test and the numerical simulation of CFG piles-gravel cushion composite foundation of the deep embedded secret passage, a settlement deformation monitoring method has been described and the selection principle of the cushion has determined so as to provide the cushion design basis in the process of composite foundation design.

Abstract:With the purpose of the study on change rule of internal charge in soil specimens under differing circumstances, dredger fill, which was collected from Guangxi Beibu Gulf Economic Zone, was studied in various parameters, including the absence/presence of the applied DC electric field, different levels of field strength, soil water content, soil compactness, and degree of desalination. Moreover, through tentatively simulating the electrical response between thundercloud and earth mass, the triggered lightning mechanism of rock soil mass was explored. The results show that both additive electrical field and atmospheric electric field had influence over charge variation of soil, the impact of which would become more significant with the increasing field strength. Higher soil water content and lower degree of desalination could enhance the charge variation and conductivity of soil, whilst this action effect would remain stable when soil water content reached a certain degree. Although soil compactness make some effect for the charge distribution, its regularity is undefined so far.

Abstract:To analyse the effect of the soil content on dynamic modulus in filling sand subgrade, the portable falling weight deflectometer (PFWD) test and degree of compaction test in field were carried out at first. The relationship of the soil content and the dynamic modulus was analysed as well. Based on the test data, the regression models among the dynamic modulus, degree of compaction, consistency and the soil content were established. Then combining with the out-and-indoor test results, the controlling standard of soil content in filling sand embankment was presented. The results turn out that the soil content in the embankment is 3.0%~5.5%. The dynamic modulus increases with the soil decreasing, and there is a good power function regression between them. There is also a good regression among dynamic modulus, degree of compaction, consistency and soil content. When the soil content is within 10%, the dynamic modulus increases then turn to decrease with the soil content increasing. When soil content is smaller than 3% or larger than 8%, the dynamic modulus are significantly smaller than others. So the controlling standard of soil content in filling sand embankment is recommended at 3%~8%.

Abstract:Under reservoir water level fluctuation, soil bank slope water sucking, stress concentration and slip deformation in Three Gorges Reservoir area form slope cracks system at different periods and different spatial parts. In this study, laws of cracks spatial evolution in different deformation periods for soil bank slope were analyzed during a water cycle of impoundment and decline by model test. The test results indicated that, in the initial impoundment period, cracks appeared near the water line at the bank slope leading edge with high appearance frequency, and scale increased gradually and partial bank slope collapsed and damaged. In the middle impoundment period, cracks appeared in the front and trailing edges of bank slope, the frequency of occurrence and the scale of which decreased. And in the late impoundment period, the leading edge of the cracks development disappeared, the trailing edge of the cracks continued to develop and the bank slope crept along the sliding surface as a whole. Cracks expanded slowly in the pause impoundment as the water level raised. In the water level decline stage, tensile cracks mainly occurred in the back edges of bank slope. In the early water level decline, cracks appeared in low frequency and it grew slowly. In the late water level decline, cracks appeared in high frequency and large scale, and where the bank slope produced lower seat deformation and dislocated berm. Moreover, in water level decline stage, bank slope crept along the sliding surface as a whole.

Abstract:An analytical solution was presented for the stresses and displacements around horseshoe-shaped tunnel using Cauchy integral method and Optimization theory in an elastic half-plane. Since the depth of a tunnel was larger than the size of the tunnel, gravity loads were simplified as uniform normal loads along far-field boundary. Finite element model was used to verify the accuracy of analytical solutions. Comparison between the results of numerical analysis by finite element method and those from the closed solutions indicates that the closed solution is reliable and applicable for the stress and displacement field around horseshoe-shaped tunnel tunnels at great depth.

Abstract:Based on the theory of ultimate equilibrium, an improved General Limit Equilibrium method (IGLE) is studied, and it is implemented in Rslope software. IGLE can simulate various limit equilibrium methods and takes into account external factors(water、tensile crack、external load) and reinforcing measures(anchor、anchor-cable、geotextile、soil nail). Imbalance thrust force method is simulated in this study, and analysis on precisions of safety coefficient and residual pushing force under two conditions of imbalance thrust force which are strength reserve method and overload method respectively by using IGLE is conducted. The study also promotes an effective usage recommendation. Aiming at the problem that engineer is easy to confuse residual pushing force with inter-slice force, comparative analysis on horizontal components of inter-slice force and residual pushing force is conducted. The results show that there is no direct correlation between them. Then the results of calculation examples of Rslope are compared with other commercial soft wares, such as slide, SLOPE/W. Specifically，the comparison includes automatically searched safety factor of circular slip surface, safety factor of sliding surface and safety factor of reinforcement. The results have a good consistency. IGLE is of practical significance for real applications.

Abstract:Adiabatic temperature rise of mass concrete is effected by many factors. Among those factors, the analysis of cement fineness and components is lacking. Influences of cement fineness, alkali content, replacement of fly ash, and gypsum content on temperature rise of concrete were investigated. The test results show that, temperature rise and temperature rise rate are improved with the increment of specific surface area of cement. When alkali content is ranging from 0.4% to 1.2%, the maximum temperature is reduced with the increment of alkali content, and the temperature-time will be extended whether too high or too low alkali content in cement. The increment of replacement of fly ash and gypsum content is good for reducing temperature rise of concrete.

Abstract:The expansion rate of mortars, prepared with active sand and non-active sand, under alkali-silica reaction (ASR) was recorded. The effects of ASR on mechanical properties of cementitious materials were studied by triaxial compression test. The relation between the microstructure of cementitious materials and the mechanical properties was investigated as well. The results showed that there was a little blade crystals gel formed in a local region near the aggregate in materials prepared with non-active sand. For the quantity of formed gel is small, the expansion effects of ASR are limited. Whereas, thick blade crystals gel layers formed near the aggregate when the active sand prepared materials subjected to ASR. Moreover, the reactive products would lead to cracks and then significantly affects the mechanical properties of mortars. Additionally, the results showed that besides the expansion rate，the ultimate compressive strength and the strain are also effective indexes to estimate the influence of ASR.

Abstract:Triaxial compression tests of mortar specimens under various hydrochemical environments were carried out. The effects of the pH、concentration and composition of chemical solution on the corrosiveness and micro/meso structure of the mortar specimens were evaluated. The hydrochemical corrosion mechanisms of the mortar specimens were explored and the results revealed further influence of various hydrochemical actions on physical and mechanical parameters of the mortar specimens. A new damage parameter was proposed based on the mortar secondary porosity caused by chemical corrosion, which can quantify the evolution process of the physical & mechanical parameters of the mortar specimens during its hydrochemical damage.

Abstract:The effects of kaolinite clay on the microstructure (pore structure, internal structure) and mechanical properties (workability, early-age and long-term flexural strength, chloride diffusion property) of the cementitious composites were tested. It is shown that the addition of clay improves the micro-pore structure in the cement paste and limits the introduction of chloride ions. As a result, it is suggested that the kaolinite clay would act as both filler and accelerator of cement hydration. Compared with the control specimen, the flexural strength of cement paste with 1% kaolinite clay increased by 30.41%, 39.04%, 36.27% and 38.32% at 1, 3, 7 and 90 curing ages, respectively. The 28-day flexural strength increased slightly. It is observed that the clay modified cement mortar has lower chloride diffusion coefficient values compared to the plain mortar, and the 28-day DCl of cement mortar decreased by 53.03% with 5% clay. Compared with the controlled sample, the increase in compressive strength and the reduction in chloride diffusion coefficient of the concrete with 5% clay addition is 28.4% and 18.87% respectively. The chloride diffusion coefficient of concrete decreases with the amount of clay addition exponentially. The 28-day compressive strength increases linearly with the chloride diffusion coefficient of the concrete.

Abstract:Cement is a traditional tailings cementation material, which causing the high tailings backfill cost. However, the utilization rate of industrial waste residue, such as steel slag and fluorgypsum, is low. So the steel slag-blast furnace slag-fluorgypsum-based cementation materials preparation with industrial waste residue substitutes for cement. As a result, its cementation tailings performances must be studied. According to mortar fluidity and bleeding quantity of tailing cementation slurry at different time and compressive strength change trend at different hydration ages, the performance of steel slag-blast furnace slag-fluorgypsum-based cementation materials is significantly better than P·O42.5 grade cement and two kinds of commonly used cementation agents in China. After soaking for three days, the pH value of these tailings solidification bodies leaching liquid is less than 9.0, which is much lower than the pH values of three kinds of high alkaline tailings cementation materials mentioned before. Leaching liquid fluorine ion concentration is extremely low. With less impact on environment. SEM analysis also show that these tailings solidification bodies mixing with the steel slag-blast furnace slag-fluorgypsum-based cementation materials have relatively dense microstructure.