Abstract:Applying the ANSYS FE, the paper analyzed the stability behavior of welded Q460 I-section columns with slender web under biaxial bending and proposed practical formulas for predicting the stability capacities of such members.Parameters considered in the analysis included web slenderness, member slenderness, flange slenderness and loading eccentricities. The results showed that the detrimental effect of web local buckling on the stability capacity of the member is more significant for axial load dominated members than for bending moment prevailed members. Comparison to the current code method showed that the later can not accurately predict stability capacities of such members. The proposed modified DSM method demonstrates rather good accuracy, meanwhile is safe.

Abstract:Experimental research on debonding failure of concert structure with high strength steel wire mesh was conducted to investigate the failure characteristics of interface debonding between concrete and reinforcing layer. The effects of different polymer mortar reinforcing methods were discussed on Shear bearing capacity and shear strength of reinforcing layer, such as single side strengthening、plant bar strengthening and U-shaped strengthening. The results show that shear-bearing capacity can be effectively improved by means of increasing bonding area of reinforcing layer, such as U-shaped strengthening or extension length of reinforcement layer. Shear strength of reinforcing layer would be weaken at the same time. Shear strength and shear-bearing capacity of polymer mortar reinforcing layer would be substantially improved by means of planting shear reinforcement. According to the test results, the suggestion value of minimum ratio of planting bar was prevised for the reference of the application in actual application.

Abstract:The effect of slip of the steel-concrete interface and shear deformation of the steel webs were considered to accurately analyze the shear lag effect of the double-cell composite box girder. The different shear lag warping displacement functions for the top and bottom plates are defined. Based on energy method, the control differential equation and the closed-form solution for the double-cell composite box girder are derived. As an example, the shear lag effect of a single box double-cell composite box girder is analyzed by using proposed method. The results show that the deflection of the composite box girder when considering the slip and the shear deformation is obviously larger than that obtained by the elementary beam solution, and which will decrease with the increase of interface slip stiffness. The slip value is approximately proportional to load heavy. The effect of shear lag on bottom steels lab of the box girder is more significant than that on top concrete slab.

Abstract:Nowadays all the existed prediction models around the world are only suitable for ordinary concrete with a strength lower than C40 or lightweight aggregate concrete with a strength under C30, however, there exists no prediction model for high strength concrete structures. Through the analysis and comparison of each creep prediction model, this paper concludes with reference to the proposed model of Japanese Concrete Codes. On the basis of creep test of high strength concrete, a creep prediction model for high strength concrete is proposed.Based on Abaqus Scriping Interface, new user's material properties that fitted Modified Model were created by Python. By comparing results of calculation and test data, a rule of creep's progress was obtained.

Abstract:In structural design of high-rise buildings, due to large upper loads or span, the beam section height is large, which usually affects the effective story height and the total height of building. To reduce the height of beam-slab structure and increase the clearance height of each floor effectively, a new connection method of composite beam-slab structure with steel-box beam embedded was proposed. As for the new connection method, monotonic loading tests were carried out on composite connection area of six steel-concrete slabs with steel-box beam embedded, to study the negative moment resistant. The difference in negative moment resistant capacity between the concrete composite floor with steel-box beam embedded and the concrete composite floor with traditional stud connection was analyzed. The finite element analysis was carried out by using ABAQUS. Experimental results and finite element analysis show that, as for the connection method of composite beam-slab with steel-box beam embedded, the negative moment resistant capacity of concrete slab has no significantly difference with the concrete slab with traditional stud connection.

Abstract:The effect of knot was analyzed on stability of glulam column under Axial Compressive Loading, using the column deflection curve method (CDC method). The initial bending, eccentricity, wood knots and elastic-plasticity of wood were considered for analysis. The member in the model was divided into three areas:knot area, knot influence area and no influence area, and three related constitutive relations were adopted in the process of analyzing. The locations of knots were randomly generated by designed program to simulate the randomly distributed knots in practical components. The stability coefficient φ was calculated considering knot at the rate of 2%, 6% and 9%, respectively. The results showed that the knots could reduce the stability capacity of the glulam column in axial compression in some degree. The numerical data was further compared with the test data and they were fit well each other.

Abstract:To study the stability capacity of long cold-formed thin-wall channel columns reinforced with CFRP, the axial compression loading test was carried out on them with CFRP around their webs and flanges. Seven columns, which are 1 400 mm long each, are consisted with one initial specimen and six strengthened with 50 mm width CFRP. The CFRP space is divided into three sorts, 50 mm, 100 mm and 150mm. And the CFRP layer has two kinds:one and two layers. The experimental results show that the global buckling happens to all the specimens. All the ultimate bearing capacity of the reinforced members is improved in different degrees. Meanwhile, the effect of the reinforced specimens wrapped with two layers CFRP is better than the others wrapped with one layer CFRP. Finally, based on the experiment, the numerical simulation is carried out, and the test and numerical results show in good agreement.

Abstract:The temperature of the structural components without fire protection increases rapidly in fire, and it will result in significant? decline in the strength of steel and concrete. In order to investigate the mechanical performance of circular tubed steel reinforced concrete columns in high temperature, the effect of temperature on material properties and the asymmetry of temperature are analyzed, then the calculation method of bearing capacity of axial loading columns in fire is proposed. This method is verified by ABAQUS and good agreement is achieved. The parameters affecting the ultimate bearing capacity of columns in high temperature are studied using the method. The results show that the cross-section dimension and the strength of concrete and steel have significant effects on the ultimate bearing capacity, whilst the wall thickness of steel tube has little effect. The influences of load ratio, dimensions of specimen, and thickness of steel tube on the fire resistance are investigated by ABAQUS. It is shown that the cross-sections dimensions have significant effects on the resistance. However, with increase of load ratio and wall thickness of steel tube, the fire resistance is decreased.

Abstract:During long action of temperature and precipitation, ancient brick masonries were weathered. The experiment employed an environmental chamber to simulate natural condition. seven unsaturated freeze-thaw cases were designed to treat various specimens which are brick units, mortar cube, triple masonry and prism masonry. We carried out saturation degree measurement, compressive test and shear test to the various specimens in laboratory. The resules show that the saturation degree is one key factor to effect on material freeze-thaw resistance. The strength of specimens increaseed firstly with saturation degree and decreases after a certain saturation degree. The best compressive resistance of brick, mortar, and prism masonry was when the saturation degree is about 53%. Based on the weathering coefficient and specimen mechanical behavior, we suggested the evaluation standard of weathering degree for ancient brick masonry structures.

Abstract:The ultimate strength formula of short columns under axial compression, which were given by the current code GB 50936-2014 and the current specification CECS 28:2012, were compared and analyzed to improve the theory of ultimate strength of long concrete-filled steel tubular columns under axial compression. The formula of the ultimate strength of short columns, basing on confinement coefficient which was given by GB 50936-2014, was rewritten as a unified form. A new stability coefficient was proposed for long concrete-filled steel tubular columns under axial compression. The accuracy of the proposed stability coefficient was validated by 36 specimens. The results show that the formula of short columns based on the confinement coefficient and the proposed stability coefficient can provide good prediction of ultimate strength for both short and long concrete-filled steel tubular columns under axial compression.

Abstract:Seven RC columns were tested under cyclic lateral load and constant axial load to study the seismic behavior of reinforced concrete column strengthened with high ductility polyester fiber. Three unreinforced columns were tested, and four other columns were tested after strengthened with high ductility polyester fiber sheets. The bearing capacity of three unreinforced columns was low. And the energy dissipation capacity and ductility were also relatively low. The cracks of reinforced specimen appeared relatively late and the cracks developed slowly. The strength, ductility and energy dissipating capacity of the retrofitted columns were improved at different degrees. And the ductility increase was more obvious. The efficiency of the use of fiber cloth can be improved through adopting the measures of improving the reinforcement ratio the plastic hinge region and adopting the measures of improving the length of longitudinal reinforcement, and the seismic behavior of RC column strengthened with high ductility polyester fiber increased.

Abstract:The global damage index of frame is defined as the loss of the strain energy dissipation capability during the pushover process, and the local damage index of plastic hinge is defined as the loss of hysteretic energy dissipation capability during the pushover process. Based on the force analogy method, the analytical expressions of the global local damage index are proposed. Besides, the correlation between global damage index and local damage indexes are discussed. The results show that improving hysteretic energy dissipation capability and constraint capacity to elastic portion of plastic hinges will effectively improve the strain energy dissipation capability of frame. There are three specific ways:reducing strength degradation, residual deformation and improving rotation capacity of plastic hinges. The global damage index is generally closed to weighted value of local damage indexes which taking the ratio of hysteretic energy dissipated by plastic hinge to total value dissipated by frame as weight. Therefore, the weighted value of local damage indexes could be used to estimate the global damage index of structure.

Abstract:With the Chinese power grid technology developed rapidly and the load applied on tower is going larger and larger, the tower base plate with eight anchor bolts has been used more commonly. Whilst the calculate theory is not comply with the actual condition. In order to make the calculate method more reasonable and reliable, The bearing capacity of Rigid tower base plate with eight anchor bolts is investigated through experiment and analytical parametric study was conducted to investigate the tower base plate by finite element method. Based on the result of experiment and finite element as well as classical mechanics theory, a new formula has been proposed which include the Equivalent calculating width and Equivalent calculating arm of force. This formula considered plate stiffness, post-buckling strength and subplate which influence the bearing capacity of tower base plate in this formula, thus the proposal formula is reasonable and effective, It is helpful in project design.

Abstract:Foundation pit corner of composite soil nailed wall has obvious spatial effect. Supporting structure near foundation pit corner is safer due to smaller stress and deformation, Whilst at present quantitative beneficial affected area of foundation pit corner to the supporting structure are not known and designs are the same in the middle and the corner of foundation pit. In order to reduce the material consumption and avoid overcautious design, the construction process of excavation and supporting of the composite soil nailed wall of soil nailing and cement-soil piles for deep foundation excavation was simulated through establishing a whole three-dimensional finite element model,which includes the corner of the foundation pit and can consider spatial effect of corner location and the interaction between soil nailing,cement-soil piles and soil through establishing interface elements. Beneficial affected area of foundation pit corner to stress and deformation of the supporting structure is analyzed and quantified. The calculation results show that beneficial affected area of foundation pit corner to the horizontal displacement of excavation face, the subsidence displacement of the ground beside the foundation pit,the bottom heave displacement and the axial forces of soil nails are about 1.3 times, 1 times, 1 times, 1.2 times of the excavation depth. Whole three-dimensional finite element calculation results are basically consistent with those of the field test data and are more reliable than two-dimensional or local three-dimensional. These conclusions can provide theory basis and research method for optimization design and safety construction of composite soil nailed wall.

Abstract:Following the technique proposed by Muki and Sternberg, the problem is decomposed into an extended soil mass and a fictitious pile characterized respectively by Young's modulus of the soil and that of the difference between the pile and soil. A Fredholm integral equation of the second kind is established which imposes the displacement compatibility condition. According to the generalized Hooke's law, the explicit solutions for the discontinuous point of the integral equation is derived, which improves the numerical accuracy and simplifies the calculation procedure. Based on the Mindlin's solution, the displacement influence function is derived which is simple. The results show that the pile-soil stiffness ratios have obvious influence on the position of the maximum bending moment for the pile under unit shear. With the increase of the pile stiffness, the position of the maximum bending moment of the pile is deeper.

Abstract:The pile-rock(soil) interface mechanical behavior was the basis of pile foundation bearing mechanics. Firstly, the mechanical property of the interface was investigated through the laboratory large direct shear test of red mudstone pile-rock interface. The results indicated that the shear stress-strain curve presented strain softening behavior. The shear stress was increasing with the shear strain initially, and when the shear stress came to a peak, the shear stress was decreasing with the shear strain and finally reached a steady. Subsequently, the constitutive equation was deduced based on the interface mechanical property, the ideal elastic-plastic contact element in FLAC^3D was further developed through fish language. Additionally, the direct shear test of red mudstone was simulated according to the interface constitutive model, and the relationship of shear stress and shear displacement between the pile and soil were analyzed which proved that the constitutive model showed good performance on simulating strain softening features of the interface.

Abstract:The stability of rock slopes is analyzed by considering the spatial variability of the rock materials based on theory of random fields. Both the cohesion and frictional coef cient along the main sliding surface are treated as Gaussian random elds, and the mean value, variance, covariance of the cohesion and frictional coef cient are determined. Spatial correlation lengths and the cross-correlation between cohesion and coef cient are obtained. Three-dimensional stability assessment of rock slopes is analyzed to obtain the factor of safety and probability of failure of rock slope. The numerical results show that the spatial variability of cohesion and coef cient of friction significantly affect the safety of rock slopes.

Abstract:Because of the special engineering characteristics of the gravel soil, it causes more and more attention. However, there are less research about the mechanical properties of the crushed stone soil with large particle size, silty clay and slightly dense state. According to the characteristics of this type of gravel soil and the results of statistical survey, two typical gradation of slightly dense gravel soil are determined. The shear strength of gravel soil specimen under different moisture content is measured by large direct shear apparatus, and the relationship diagram of the shear force and the horizontal displacement under different water cut rate is drawn. The shear strength indexes c,φ value are determined by univariate regression and the impact of moisture content and gradation on the shear strength is analyzed. The results show that with the increase of water content, the cohesive strength of the gravel soil is decreasing, but the change trend is significant and related to the content of cohesive soil. The change of water content has little influence on the friction angle of the gravel soil. Using the specification method to calculate the bearing capacity of foundation, and comparing with the experience value, the results show that the influence on the moisture content of foundation bearing capacity, and is associated with the silty clay content of gravel soil filling.

Abstract:The MICP(microbial induction of calcium carbonate precipitation)cemented sand samples are prepared by injecting twice bacteria solution with different concentrations of nutrient salt treatment. S. pasteurii is used to induce calcite precipitation, and all the specimens were prepared by injecting a single concentration or multi-concentration nutrient solutions. In this study, 0.5 and 1.0 mol/L urea-calcium chloride solutions are used for the former grouting treatment, while for the latter one, 0.5 mol/L urea-calcium chloride solution is firstly injected; and subsequently, 1.0 mol/L urea-calcium chloride solution is utilized. Based on the experiment, the strength, modulus of elasticity and calcite content of MICP specimens' different sections are analyzed. From the experimental results, it can be found that multi-concentration nutrient treatment has significant influence on the unconfined compressive strength of bio-cemented sand and calcite content. The multi-concentration nutrient treatment can ensure the high strength and elastic modulus of the sample under the condition of good uniformity. Finally, the basic factors that affect the strength and uniformity of samples were discussed based on the method of multi-concentration nutrient treatment.

Abstract:The mechanical properties of each soil layer in multiple-structure thick overburden pervious foundation diverge significantly and specific questions that draw attention are quite different from each other. Based on the principle of Biot consolidation theory,the study takes soil non-liner rheological and the change of porosity, permeability coefficient, elastic modulus and poisson ratio at the consolidation deformation process of soil into account. The coupling process of seepage and stress fields of Daga hydropower station dam foundation is simulated by fluid-structure interaction module of ADINA to analyze mechanical properties and interaction of each layer. The research shows that the looser permeable soil on surface is the main seepage channel, also the inlet and outlet area of seepage and settlement deformation reflects area. Measures should be taken to improve the compression modulus in upstream and install the anti-filter layer and drainage facilities in downstream area. Fine sand layer in dam foundation is the main reason for dam foundation settlement, which plays a very leading role in the dam foundation settlement. Meanwhile, attention should be payed to the liquefaction properties of adverse impact on the dam foundation. Artesian aquifer in dam foundation produces up-holding force on the downstream side of the upper structure, and the destruction is small if the location is deep. Deep soil layer have a less effect on the seepage failure of dam foundation, but the effect can not be dismissed on settlement and seepage flow. Since in the permeability coefficient of sand gravel stratum and fine sand layer exists a modest distinction, the soil layer does not generate the contact erosion. In addition, the pore water pressure is dissipated at a rapidly-declining phase, and the dam foundation shows a stabletendency at rapid consolidation stage. Vertical cutoff wall can effectively decrease seepage gradient and seepage discharge, and the settlement deformation of dam foundation is controlled in upstream region of cuttoff wall. But the deformation of upstream dam foundation produces a large horizontal thrust to the cutoff wall, so the size of cutoff wall should be increased or the auxiliary seepage control measures shall be adoptedcorrespondly.