Abstract:Based on an actual project, the ABAQUS material subroutine considering damage cumulative effect and member buckling was adopted to analyze the collapse process of steel trussed arch structure. The failure mechanism and the failure mode of such structure under severe earthquake conditions were studied. The results indicated that, under the action of severe earthquakes, the cumulative damage increased and structural stiffness declined, which leading to the structure failure. The damage cumulative effect caused the decrease of the member stress and the increase of nodal displacement and member strain. Subjected to seismic waves, the webs at the columns of the middle main truss failed at first; then the failure region extended along the out-of-plane direction of the main truss and extended from the column foot to the top of structure. After the earthquake, the webs at the one-quarter point of the main truss and the webs at columns with large slenderness ratio buckled. It will lead to early failure of part members if member buckling is considered. However, it has little effect on the failure mode of structure.

Abstract:There are obvious geometric nonlinear mechanical characteristics in new type arch bridge with diagonal web cables. Meanwhile, the convergence of the existing arch axis iterative optimization method is not good. In order to solve new type arch bridge axis iteration convergence problem considering geometric nonlinear mechanical analysis, an arch axis iteration optimization method was proposed based on the iteration basis finite element model with two hinge arch model in main arch ring. A 600m span arch bridge with diagonal web cables was selected as an example to test the convergence performance and applicability of proposed method. The results showed that the bending moment of proposed method had better distribution along arch span, and it is about 35% smaller in maximum bending moment, 17% smaller in minimum bending moment and 23% smaller in bending strain energy compared to the results of linear iteration optimization method. Convergence analysis results demonstrated that proposed method had better iteration performance than the existing method. Meanwhile, different initial arch axis can converge to stable results.

Abstract:The probabilistic model of resistance in the current unified standard for reliability design is imprecise for RC members subjected to eccentric compression. The reason is that it lacks full considerations of influences of varying eccentricities. An improved probabilistic model of resistance with different eccentricities and reinforcement ratios is obtained by using the Monte Carlo sampling method and the current probabilistic models of all resistant factors. The results indicate that it is accurate to fit the probabilistic distribution of resistance with normal distribution. Given that, the applicability of the improved model is analyzed for reliability analysis of RC members subjected to eccentric compression with random eccentricities. It shows that when the design value of eccentricity is close to or larger than the eccentricity producing balanced failure, there would be large errors in reliability analysis if the probabilistic model of resistance given in the current reliability unified standard is used. However, it is accurate when using the proposed probabilistic model. The results also show that the design of RC members subjected to large eccentric compression is unsafe based on the current reliability unified standard because it lacks full considerations of effects that the resistance decreases as eccentricity increases.

Abstract:In order to analyze the failure and optimize the ductility of concrete-filled square steel tubular stub column with inner CFRP tube (CFSST-CFRP) under axial compressive load, the mechanical behaviors of specimens in related tests were analyzed by a finite element software ABAQUS. And failure analysis was made. A reasonable expression on ductility optimization and improvement is drawed through nonliner regression. The results indicate that CFRP fracture is a principal reason of CFSST-CFRP stub column failure under axial compressive load. Meanwhile, its ductility can be improved by increasing the value of ξf/ξs. Concrete-filled square steel tubular (CFST) stub column crack more seriously than CFSST-CFRP, and CFSST-CFRP stub column is not functioning adequately, without available CFRP bonded.

Abstract:In order to investigate the influence of three main performance parameters of isolator, i.e. equivalent horizontal stiffness Kf, pre-yield stiffness K1 and yield force Qd, on the bilateral seismic response of base-isolated structures with different site condition, eighteen base-isolated structures different between Kf、K1 or Qd were designed. Based on SAP2000, the bilateral seismic responses of each isolated structure excited by four seismic waves of different site types are analyzed respectively. It is found that, the acceleration response and the base shear response of base isolated buildings under bilateral seismic excitation are influenced remarkably by the aforementioned isolator parameters, and the effect of the parameters on the isolation layer’s displacement response varies from different site conditions. Under the condition of Ⅰ、Ⅱ、Ⅲ site classified in Chinese seismic code, both the top floor’s maximum acceleration and the maximum base shear of base isolated structure show an obvious increase trend with the increasing of Kf,K1 and Qd, However, the isolation layer’s maximum deformation does not change evidently. Under the condition of Ⅳ sites, the effect of isolator parameters on the isolation layer’s maximum deformation is significant and represents obvious regularity. As Kf,K1 and Qd increases, the peak deformation value of isolation layer decreases sharply with the biggest decline of above 80%.

Abstract:In order to accurately evaluate the aseismic behavior of the seismic damaged masonry pagodas destroyed by Wenchuan earthquake and strengthened after the earthquake, a test was conducted to acquire related parameters on seismic performance from the specimens made by masonry and retrofitted with grouting and steel hoops. Taking a seismic damaged ancient masonry pagoda in Sichuan as a case study, four kinds of primitive specimens are fabricated by simulating the conformation of the masonry pagoda. Then the primitive specimens are destroyed under cycle loads and the damaged specimens are repaired by grouting and steel hoops. Cycle controlling tests are conducted with the specimens and relevant data are acquired. Experimental results showed that grouting combined with steel hoops could improve the ductility and energy dissipation capacity of a seismic damage of brick masonry structure, but it do a little to improve the stiffness of a seismic damage structure. And the cracking load of the repaired masonry is much lower than the original undamaged structure.

Abstract:Based on the three-dimensional homogenization theory, the Characteristic 3D elementary pattern in the masonry was established. The homogenized masonry wall was considered as a vertical plate with four supports. The plate theory was used to research the out-of-plane mechanical properties of masonry panels. Homogenization models with theory of thin plates and theory of medium and heavy plates were given and the calculation formula of deflection of homogenization masonry wall were deduced as well. The mid span deflections of 120 mm, 180 mm, 240 mm and 370 mm masonry walls with both fixed and variable ratio of height to width were analyzed. The applicability of two kinds of plate theories on homogenization masonry walls of different sizes was obtained. This methodology was practical and the masonry theory was improved.

Abstract:In order to realize the predictive function of BIM technology, the reliability theory and theoretical probability method are utilized to judge the uncertainty which exists in the process of construction. Meanwhile, the complicated relationship between construction schedule and prediction model is analyze, the random prediction model for construction schedule is established as well. Particularly, the influencing condition about a single factor in the process of construction is taken into consideration. Determinate model and random model for construction time as well as reliability analysis method for the construction time prediction which is based on a single influencing factor are studied .At the same time, The integrated management method of reliability prediction about construction schedule which is on basis of BIM management platform is discussed. The case study shows that the proposed method has delivered dramatic results to the control of construction schedule.

Abstract:The digital image displacement measurement technology and finite element data smooth were applied in the soil slope shaking table test. The displacement field and strain field were obtained from the whole vibration process. And the seismic failure mode and failure mechanism were discussed as well. The results show the deformation of soil slope increases gradually; there is shear failure from slope middle to toe and tension-shear failure at the top of slope; there forms deep arc-shaped slip surface when the slope model fails. The generalized curvature of displacement time-hisrory curve is used to judge whether the slope seismic failure is feasible.

Abstract:Numerical models based on FLAC 3D are difficult to build. A new kind of method modeling and meshing in the CATIA software, named the CATIA-FLAC 3D coupled modeling method, was proposed. This method utilizes the powerful geological modeling capabilities of CATIA for three-dimensional geological body modeling and meshing. And then, the interface program of CATIA-FLAC 3D is adopted to export the information into FLAC 3D, which is coded by visual basic language based on the variance of nodes and elements between the two software. The new proposed method was used in a bias tunnel through a mountain, and the results verified the feasibility and effectiveness of the proposed method.

Abstract:Based on the marble conventional triaxial test data, the crack initiation stress and rupture energy under different confining pressures are analyzed. Results showed that the crack initiation position is gradually close to the peak strength point with the increase of the confining pressure. The location of the crack initiation occurs in 50% ~70% peak strength. The rupture energy and confining pressure are in positive linear relationship as well as the rupture energy and peak axial stress. And sudden increase of AE energy count corresponds with the crack initiation stress. AE energy count and cumulative energy increase quickly after the crack initiation position, which increase significantly in the crack initiation point. The crack initiation point of theoretical calculation is in good agreement with acoustic emission monitoring. Mogi-Coulomb criterion is in keeping with experimental results.

Abstract:Based on the single compression experiments in laboratory, the structural change characteristic of loess with different initial structural in single compression stress conditions was studied. The conclusions are: compared to the single axial compression strength between intact loess and remold loess in the same moisture conditions, strength of intact loess was way bigger than remold loess; when the water content was low, all of a sudden, the destruction model of loess samples was mainly brittle tensile failure; when the water content was low, there was relative little effect on metastable of structural and was relative little loss of initial structural strength, and relative more variability; and then, there was way higher initial structural strength. The structural index decreased sharply with the moisture increase of intact loess, and the effect of water content on initial structural is obvious; when the water content reached a certain value, moisture effect on initial structural of intact loess become more and more unobvious, and structural index of loess was relative small. In other words, the initial structural has been fully released by remolding and saturating; the reasonability of structural index which was quantitative described the initial structural of loess was verified.

Abstract:In order to study the mechanical properties and structural properties of soft dredger fill under lateral deformation. Based on true triaxial and WF stress path apparatus, lateral unloading undrained tests were carried out. The results derived from true triaxial test, WF stress path test and routine triaxial shear test were analyzed. The contrastive conclusions are as follows: The stress-strain curve of true triaxial unloading test shows a softening behavior, which is different from the hardening behavior for that of conventional triaxial shear test. With the increase of initial confined pressure, the dilatancy of soil transfers from shrinkage to expansion. The structural yield stress of the unloading soil with true triaxial test method is dramatically larger than that with the latter two tests due to the effect of intermediate principal, which exhibits a nonlinear growth as the coefficient of intermediate principal bd stress jumps. The shear strength indexes of unloading soil with true triaxial test is larger than that with WF stress path test. Compared with the results of routine triaxial test, the internal friction angle of true triaxial test is bigger while the cohesion is smaller.

Abstract:Municipal solid waste incineration fly ash (MSWI) was successfully used as raw material in sintering and preparing a calcium sulphoaluminate (CSA) cement clinker in laboratory. The effects of different types and different addition percentages of cement additives on compressive strength and hydration properties were investigated. The results showed that lime (LI) powder / slag (SL) powder was compatible in CSA cement system while the activities of fly ash(FA)/ MSWI was low. Adding these four types of cement additives in CSA cement system respectively, there were negative effects on compressive strengths of hardened cement at early age while LI/SL improved the compressive strength at later age. The performance of combined additives was better, especially, the specimens with 10%LI+10%SL, 10%LI+10%MSWI, and 5%LI+15%SL.

Abstract:The effect of the carbonation on the properties of the steelmaking slag-slaked lime (SmS-SL) mortar and its mechanism were mainly investigated. Furthermore, the environmental benefits of the SmS-SL mortar were discussed as well. Results indicated that carbonation could strengthen the SmS-SL mortar, reduce its drying shrinkage and improve its soundness. With the increase in the steel slag content, the strengthening effect of carbonation on the SmS-SL mortar is enhanced, but its dry shrinkage reduction effect is weakened. The SmS-SL mortar using steel slag exhibits significant environmental benefits. Its CO2 sequestration-efficiency and steel slag-recycle efficiency respectively reaches 6.4% and 27.8%.

Abstract:In order to achieve the comprehensive utilization of iron slag and steel slag, foamed concrete were prepared by adding small amount of gypsum, lime and clinker in steel slag-iron slag system and using aluminum powder as foaming agent,. The three-day, seven-day and twenty-eight-day bulk density and compressive strength of foamed concrete with the different ratio of the main raw materials were researched. Furthermore, in order to research the hydration mechanism and microstructure of foamed concrete, the XRD and SEM images of the three productions of foamed concrete were analyzed. The results showed that the coordination of the dosage of steel slag and iron slag was better when the former was 30% and the latter was 45%, Meanwhile, the compressive strength was 5.1 MPa, the bulk density was 625 kg/m 3; Ettringite and C-S-H gel synergies generated in steel slag-iron slag system. Besides, hydration activity of steel slag was obviously lower than that of iron slag.

Abstract:The P(AM-DAC-BA), one kind of hydrophobically associating cationic polyacrylamide(HACPAM), was synthesized with acrylamide (AM), acryloyloxyethyltrimethyl ammonium chloride (DAC) and butylacrylate (BA) by the micellar free radical copolymerization technique. The reaction was carried out under the irradiation of UV light. The effects of main factors, i.e. monomers concentration, mass ratio of AM and DAC、BA ratio、CTAB ratio、photoinitiator concentration and irradiation time on the molecular weight were investigated. The results showed that HACPAM with the molecular weight of 849×10 4 can be synthetized when the monomer concentration was 30%, the mass ratio of AM and DAC was 70:30, the BA ratio was 2%, the CTAB ratio was 2%, the initiator concentration was 3‰ and the irradiation time was 100 min. The chemical structure and performance were characterized by FT-IR, SEM, DTA-TGA. The results showed that the polymerization reaction between monomer happened, the HACPAM was synthesized. In addition, the polymerizate heat stability was fine.

Abstract:To solve the problem of poor nitrogen removal capacity in winter, the hydrolysis-denitrification process combining hydrolytic acidification and denitrification process within single reactor was induced to treat municipal wastewater. The pilot test showed that the average removal rates of ammonia nitrogen of hydrolysis-denitrification process were 98.3% and 98.4% in winter and summer, respectively. And the average removal rates of total nitrogen were 65.2% and 68.0%, respectively. According to the nitrogen removal of pilot test, the activated sludge in hydrolysis-denitrification process and AAO process were studied to investigate the effect of temperature on specific denitrification rate and carbon source consumption rate. It is found that the temperature on activated sludge in hydrolysis-denitrification process had smaller effects than that in AAO process. In the two cases, namely the temperature are 25 ℃, 30 ℃, respectively, both denitrification rates of them was similar. However, when the temperature were 8℃、15℃ and 20℃, the specific denitrification rate of hydrolysis-denitrification sludge was 1.7、1.3 and 1.4 times the anoxic-denitrification sludge, respectively. In addition, the carbon source consumption rate of hydrolysis-denitrification sludge was 51.2%~81.7% of the anoxic-denitrification sludge.

Abstract:The composite photocatalysts were made by using solid dispersion method with nano-TiO2 loaded on hydrophobic or hydrophilic zeolite and zeolite with different pore diameters. The removal and mineralization efficiency of oxytetracycline (OTC) in aqueous solution were investigated under the irradiation of 32 W UV lamps by composite photocatalysts loaded with different ratios of nano-TiO2. The results showed that UV/10%TZ2 (hydrophilic zeolite) achieved a better removal efficiency of OTC than UV/40%TZ1 (hydrophobic zeolite) while UV/15%T5A (hydrophilic zeolite with a pore diameter of 0.5 nm) achieved a better removal efficiency of OTC than UV/10%T13X (hydrophilic zeolite with a pore diameter of 1 nm). That is to certify that the hydrophilic zeolite and zeolite with small pore diameters loaded with nano-TiO2 could achieve better removal effects for OTC in aqueous solution. The OTC that adsorbed on the inside surface of 13X cannot be degraded due to the out range of hydroxyl radicals attack.

Abstract:Batch experiments were carried out in order to investigate the adsorption behavior of As (Ⅲ) and As (Ⅴ) affected by activated aluminum. The results show that the adsorption characteristics of As (Ⅲ) and As (Ⅴ) are consistent: 24-hour is enough to obtain equilibrium; The kinetic data correlates well with the pseudo-first-order model; the film diffusion is the rate-limiting step approved by Boyd kinetic model; Compared with the Freundlich model, Langmuir isotherm model offers a better explanation for the adsorption of arsenic onto activated aluminum, indicating the adsorption is mainly monolayer; The obtained mean adsorption energy values calculated from Dubinin-Radushkevich model are lower than 8 kJomol -1, suggesting the adsorption process is physical; The thermodynamic parameters point out that the adsorption is a spontaneous, endothermic process, and the randomness increase at the solid-liquid interface after adsorption.