Abstract:According to some problems existed in current Chinese codes for design of seismic shear strength of concrete hollow block masonry, the curve of shear strength of concrete hollow block masonry under shear-compression loading, including descent segment, was presented by theory of failure region and test results of 58 concrete block masonry walls under shear-compression loading. And the design seismic shear strength formula of concrete hollow block masonry, which has reliability guarantee, was deduced. Compared with current Chinese codes, the design seismic shear strength formula of concrete hollow block masonry not only can perfectly simulate the shear-friction, shear-compression and diagonal compression failure modes, but also avoid unreasonable and unsafe calculation of seismic shear strength of concrete hollow block masonry, which can be applied to design of tall reinforced concrete masonry structures.

Abstract:In order to search for a tool to test whether the earthquakes is reasonable for the design, a method based on multidimensional scaling (MDS) and the dynamic time warping distance (DTW) was proposed, which represents the dissimilarities of earthquake in a low dimensional space in a visualized way and uncovers hidden structure of earthquake. The analysis of record from the seismic array shows that the proposed method can be a powerful tool in detecting the correlation structure of spatial ground motion as well as verifying whether the algorithm is producing properly correlated motions in space.

Abstract:The experiments were carried out to investigate the behavior and failure modes of Q420 double-angle combined cross-section members whose specification were L160×12, L160×14, L160×16. The results show that all the members fail with an elastoplastic bending buckling. Based on the improvement of the inverse calculation segment length method and some relevant procedures, the related curves of axial force and moment with different specifications, different slenderness ratios and residual stresses were calculated. The calculation method of in-plane stability and column curves were proposed. The nonlinear power function model is appropriate for such members' moment-rotation relations under equal bending moments.

Abstract:A nonlinear constraint-surface impact element (CIE) was developed for simulating the pounding in axial direction between 3D shell-element-mesh bridge girders based on the engineering background of ChaoShan airport. Then, a method, different from the previous literatures, for calculating the stiffness of impact element was proposed based on the flexibility method. The methods proposed were adopted and used to analyze the elevated bridge of ChaoShan airport in GuangZhou for the purpose of investigating comprehensively the earthquake-resistance capability. The bridge girders were modeled by shell elements and CIEs were assigned to the positions of the corresponding expansion joints. Isolating elements were used to simulate LRBs, and typical bilinear LRB hysteresis stiffness model obtained from experiment were adopted to describe the dynamic hysteresis behavior. Pounding forces, dissipation capability of LRBs, lateral displacements of LRBs, pier base shear forces and moments as well as the pounding effect on these cases were investigated, respectively. The proposed methods and analysis results aim at improving the earthquake resistance of the elevated bridge, which provides reference for the similar project.

Abstract:Through analysis of monitored ground settlements of Hangzhou Qing-chun Road cross-river tunnel, characteristics and influencing factors of ground settlements due to large-diameter slurry shield tunneling were summarized, and a modified hyperbolic model was proposed to predict the settlements. The results indicate that: 1.Peck equation is well used to predict ground settlements induced by slurry shield tunneling in Hangzhou district. The trough width parameter ranges from 0.25～0.32 while soil volume loss from 0.04%～0.33%. 2. Settlements before the shield tail leaving the monitoring sections are small, while soil closure at the shield tail and long-term consolidation settlements make most of the total settlements, with percentages of 57.27% and 41.08% respectively. 3. Increasing the pressure of slurry and synchronized grouting appropriately can counterbalance some ground loss, which can reduce the ground settlements. 4.Transverse ground settlements induced by ground loss represent the shape of Gaussian curve while heave movements behave irregularly. Ground heave movements due to large pressure of slurry and synchronized grouting often lead to the transverse ground settlements' deviation from Gaussian curve. 5. The modified hyperbolic model can be used to predict ground settlements due to slurry shielding in Hangzhou district with great accuracy.

Abstract:When steel plate-masonry composite structure used in the existing masonry structure with load bearing walls is removed for a large space, composite action should be considered between the beam and the supported masonry wall due to the arch effect formed in the supported wall. In order to investigate the working mechanism, failure mode, and load-carrying capacity, strain distribution in critical sections and mid-span defcection of this type of composite wall-beam, five steel plate-masonry wall-beams were tested under concentrated loads and analyzed, which considered variables of height-span-ratio of supported masonry wall, height-span-ratio of composite beam and thickness of steel plate. The results show that steel plate-masonry composite wall-beam starts failure from the masonry located at the line between loading point and supporting point; strain distribution of steel plate along section height meets the plane section assumption; the height-span-ratio of supported wall can directly influence the failure mode of masonry wall, buckling load corresponding to steel plate experiencing local buckling and ultimate load of tested specimens; the reasonable height of supported masonry wall is beneficial to the formation of composite action between supported masonry wall and composite beam, and the excessive high masonry wall will reduce the ultimate load of the tested specimen. Finally, the reasonable range for height-span-ratio of supported masonry wall was presented, and the proposed value representing the flexural stiffness of the steel plate-composite beam relative to the in-plane stiffness of the supported masonry wall was at least more than 79.

Abstract:For bridge with tall piers, the influence of higher modes on structural responses becomes more evident. Modified MPA method(MMPA) which is based on MPA theory and the concept of “equivalent mode height” is presented. To verify the effectiveness and the degree of accuracy of this method, several Pushover methods including MPA and MMPA methods were adopted to analyze tall piers for bridge, and then compares the results with that in dynamic time-history analysis. It is shown that MPA and MMPA methods can improve computational accuracy comparing with other normal Pushover methods when seismic intensity is lower, whereas the computational accuracy for MMPA methods is superior to that in MPA analysis with the seismic intensity becoming larger.

Abstract:The time-changing analysis model for concrete filled steel tubes was established based on the time-changing concrete model of CEB-FIP MC90, in which the interaction between steel tube and concrete core was considered by the restraint conditions of master and slave nodes. The numerical simulation method was developed for analyzing the whole construction process of high-rise CFST structures. A real structure was taken as numerical example, in which the influence of concrete creep and shrinkage as well as construction process was considered. The results of numerical simulation are compared with those obtained from on-site monitoring. It is shown that the concrete creep and shrinkage as well as construction process have big influence on high-rise CFST structures, which should be taken into account in designs and constructions.

Abstract:Rainfall is the main input for probabilistic analysis and prediction of rainfall-triggered landslide. The joint probabilistic structure of daily rainfall (DR) and cumulative rainfall (CR), which are dominant parameters of rainfall related on landslide in Chongqing region, was analyzed. Following the traditional technology, daily rainfall was translated into discrete variable by rainfall grade and cumulative rainfall became continuous variable if records with very small cumulative rainfall were ignored. Then joint probabilistic model of discrete variable and continuous one was derived, and transiting solution of conditional density function was put forward, together with its approximation via a family of Dirac δ sequences. Naturally, the proposed method was used to analyze conditional density function of cumulative rainfall in Chongqing region, and the numerical results were verified by comparison. However, most of the conditional density functions were irregular and not modeled by simple probability density function, thus the finite mixture distribution was introduced, which is of uncomplicated format and relatively high precision. At last, the joint probabilistic model of daily rainfall and cumulative rainfall was built up by combining frequency function of grade of daily rainfall with conditional density model of cumulative rainfall.

Abstract:To avoid equilibrium potential shifts in polarization curve test, based on anodic polarization current method, the critical polarization current density of steel corrosion was given as well as the corresponding empirical formula of corrosion current density. Reasonable explanation to equilibrium potential shifts was given by studying polarization curves characteristic of rebar in concrete before and after corrosion. The results show that anodic polarization current method can effectively distinguish steel corrosion, and the critical polarization current density is 0.2 μA/cm 2.

Abstract:In order to investigate the seismic behavior of partially-restrained steel plate shear wall (Steel Plate Shear Wall, SPSW), the effects of partially-restrained connection on the hysteretic behavior, lateral bearing capacity, stiffness, energy dissipation of SPSW with strong and weak steel frame were simulated under low cyclic loading via equivalent strip model that had been verified by experiment. The results show that hysteretic behavior of SPSW has dual characters. The hysteretic curves of SPSW with strong surrounding steel frame become fat, and the hysteretic curves of SPSW with weak surrounding steel frame become narrow. With the increase of the bending capacity of PR connection, the hysteretic curves of SPSW become fat gradually, and the capacity of energy dissipation and lateral bearing increase. However, the effect on lateral stiffness of PR connection of SPSW with strong steel frame is higher than the one with weak steel frame.

Abstract:To improve the understanding of the soil aching effect in the embankment fill, a series of model tests and finite element analysis were carried out. It is found that for low fill height relative to the net pile spacing, H/s－a≤1, the failure surface is vertical or slightly inclined which starts from the pile edge and goes through the whole fill height. For H/s－a≥1.5, the developed bulb shaped rupture surface is located near the pile head and can be approximated as a logarithmic spiral surface. By using the failure surface shape determined from the model test and FEM analyses, a three dimensional simplified method to evaluate the soil arching effect was proposed. The computed results were compared with FEM results and the experimental data collected from literatures, it is found that the present simplified method can predict reliable results.

Abstract:Taking Shenzhen universiade stadium as engineering background, the mechanical character of a new style ‘single-layer folded space grid structure’ was analyzed. Based on the matrix mechanical model and considering the time-dependent effects of geometry, constraint, and load in construction process, the state-nonlinear construction process analysis method was established. And the analysis program was formed by the APDL platform of finite element software ANSYS to analyze the single-layer folded space grid structure. It is shown that both the maximum displacement and stress wave in construction. The bracing forces wave strongly in the unloading process and the maximum amplitude approximates 2 times of the initial value. The stress state differs from the design state when construction process is finished, and the displacement distribution is not completely symmetrical. The analytical results can guide the temporary supports design and construction process control.

Abstract:Deformation measurement and analysis play an important role in geotechnical model tests. Using the concept of quadrilateral isoperimetric element, the strain filed was achieved from the calculation method based on displacement modes, and the verification results show that this measurement technique has a reliable precision. The soil deformation in model test of square shallow foundation was measured by using this technique, and the results show that the measurement system based on digital image correlation method can realize the whole process quantitative measurement of soil displacement field and shear strain filed. This deformation measurement technique provides a tool for the qualitative and quantitative analysis of soil micromechanics characteristics.

Abstract:The flexural performance of the beams reinforced with both non-prestressed bars and prestressed bonded FRP bars was theoretically analyzed. Both the CFRP bar and the AFRP bar were taken as the representatives in the study. Correlativity of two kinds of balanced relative depth of compressive area, respectively corresponding to the yield of steel bar and to the rupture of FRP bar, was investigated. Therefore the influence of performance parameters of FRP on the flexural failure modes was analyzed. The results indicate that failure modes and two kinds of balanced relative depth of compressive area are with direct correlation, and the latter is directly influenced by the performance of the FRP bars. Adopting the short-term performance parameters or the long-term performance parameters, which considers the environmental factor, creep fracture factor, relaxation factor and materials coefficiency, would have different results. Failure mode I is the ideal one, while the others should be avoided. Prestressed control stress of CFRP bars with low-ductility should not be too high, otherwise the rupture of CFRP bars will happen before the yield of steel bars.

Abstract:Seismic performance of SRC-RC transfer column was analyzed based on experiment of 12 specimens of transfer columns and 1 RC specimen under low cyclic reversed loading, which mainly focused on the extension length of shape steel. Analysis and comparison on skeleton curves of specimens was carried out. Analysis was completed for ductility, bearing capacity, energy dissipation capacity and degeneration ratio of strength. Displacement ductility changes with the increase of extension length of shape steel, enhancing at first, then reducing, and reaching peak value when extension length is close to three fifths of column height. Extension length of shape steel has little effect on bearing capacity. Energy dissipation capacity of transfer columns has relationship with many factors. Three fifths of column height is rational for extension length of shape steel, and specimens have not only advanced performance of energy dissipation but also good stability of stiffness and strength in this condition. The bond performance between concrete and shape steel decreases with the increment of extension length of shape steel, and hence stability of strength decreases.

Abstract:To study the freeze-thaw durability of Aught-Set(AS) firming agent modified soil, a series of triaxial tests were conducted. The mutual relationships between stress-strain relationship, static strength, dynamic modulus and critical dynamic stress of AS firming agent modified soil and curing time, freeze-thaw cycles, cooling temperature were deeply analyzed. The results show that the unconfined compressive strength of 7 d is 75% than that of 28 d. The stress-strain curves of AS firming-agent modified soil are strain-softening and in brittle failure shape. The static strength, critical dynamic stress and resilient modulus decrease in exponential form with the increase of freeze-thaw cycles, and after 6 cycles of freezing and thawing, the trend is stable. Under the same dynamic stress, the cumulative plastic strain of samples develop from stable state to failure because of freezing and thawing. After many times of freeze-thaw cycles, the lower the negative temperature, the little influence on the mechanic properties.

Abstract:With the isolation system based on pure rolling as the object of study, the computer program was develeped to calculate its seismic displacement based on its characteristics. And then, experiment method and theory analysis method were adopted to analyze the new computer program and the traditional calculation method’s rationality in contrast. It is shown that the computer program is reasonable, and its results are relatively accurate and conservative. The traditional calculation method based on the rigid-plastic relation of force and displacement is illogical, and its results are relatively small. When subjected to earthquakes, the structures maximum relative displacement would be larger than the earths maximum absolute displacement.

Abstract:In order to investigate the effect of quickly decrease temperature on activated sludge system, with the operation of sequence batch reactor (SBR) and mean DO value at 1.5 mg/L, the sludge volume index (SVI) and pollutants removal effect with quickly decreased and return normal temperature were analyzed. The results show that the SVI increases to activate sludge bulking, and activated sludge sedimentation property worsens when the system temperature quickly decreases from 25℃ to 14℃. The SVI slightly decreases, but it cannot return to normal range when system temperature returns to 25℃. The phosphorus and COD removal effects are slightly affected by quickly decreased temperature, whlle the activated sludge nitrification is severely affected by quickly decreased temperature. with the ammonia removal efficiency decreased to 20%. The activated sludge nitrification can return to normal level when system temperature returns to normal temperature.

Abstract:Taking a coconut shell powder activated carbon (PAC) as the carrier and butyl acetate titanate with ethanol as raw materials, TiO2/AC(activated carbon) photocatalyst was prepared through sol-gel and impregnation method, and batch experiments were carried out to investigate its performances of removing Carbamazepine from artificial water. The results indicate that TiO2/AC has a better removal of carbamazepine than powder TiO2 and PAC. In the same condition, the removal of carbamazepine in TiO2/AC system is 1.7 times than that in TiO2. When the initial concentration of Carbamazepine is 10 mg/L, and the dosage of TiO2/AC is 500 mg/L, in which the load capacity of TiO2 is 11.2%, the removal rate reaches at 91.5% while the PH is 1.0. The reaction of photocatalytic degradation process can be accorded with two-step dynamics kinetics with different concentrations. The constant of secondary reaction is inversely proportional to concentration. Using Langmuir-Hinshelwood (L-H) model, it concludes that the apparent adsorption equilibrium constant Ka is 9.215×10 3 L/mol, and the surface reaction rate constant Kr is 3.678×10 -6 mol/(L·min). Thus, microwave irradiation is the best way for catalyst regeneration.

Abstract:In order to investigate the influence factor of short cut nitrification and denitrification, the rapid startup and steady operation of the short cut nitrification and denitrification with real time control were studied. The results show that the short cut nitrification and denitrification can be rapidly setup by the control of DO and pH cooperated with low DO. The excessive aeration has negative effect on the accumulation of NO -2-N for primary short cut nitrification and denitrification sludge. With real time control and reasonable aeration time, the ammonia can be oxygenated completely and the nitrite can not be oxygenated when aeration stops and ammonia oxygenation just completes. Thus the real time control strategy not only realizes the short cut nitrification and denitrification, but also maintains such steady operation.

Abstract:Based on the principle of simultaneously nitrifying-denitrifying nitrogen removing, sewage treatment plant wastewater sludge was used as inoculum, and the continuous low temperature shaker was used to enrich the simultaneously nitrifying-denitrifying nitrogen removing bacteria (SNDB-5) at 15℃. Traditional and modern molecular biology methods were adopted to determine the taxonomic status of the isolated bacteria which was named SNDB-5. Water bath shaker was used to analyze the NO2 --N removal in the nitrifying bacteria culture medium. The results show that SNDB-5 has 99.0 % homology with Pseudomonas mendocina. Morphological, gram staining and biochemical characteristics are also similar to Pseudomonas mendocina. Incubating reaction conditions in shaker shows that SNDB-5 activity is inhibited when the concentration of NO2 --N increases to 150 mg/L.

Abstract:Nitrogen composition in urban stormwater runoff from five underlying surfaces was studied and discussed. It is shown that the highest EMCs of TN(Total Nitrogen) came from urban traffic road(i.e. 10.6 mg/L), and the lowest was from campus catchment areas(i.e. 2.4 mg/L). Meanwhile, EMCs of NH3-N from traffic road and commercial district (i.e. 3.4~4.6 mg/L) were much higher than that from concrete roofs and tile roofs(i.e. 1.2~1.6 mg/L). Although PEMC10 of TN was greater than EMCs, the proportion of nitrogen was still similar. Nitrogen in stormwater was predominantly dissolved (73%~82%), with DIN (Dissolved Inorganic Nitrogen) the abundant form (63%~82% of TN). The highest concentrations of nitrogen species form commercial district, concrete roofs, campus catchment and tile roofs were NO3-N, which made up of 39%, 39%, 44% and 52% of TN respectively. However, it was NH3-N that had greatest concentration in runoff from urban traffic road, and the ratio of NH3-N /TN was as high as 43%. The removal of TN could be enhanced through improvement of stormwater management measures. The key factor was that conditions to drive nitrification must be created, retention time of stormwater runoff in treatment systems should be increased and material with low nitrogen content should be selected as construction media.

Abstract:The changes of electrical resistivity with time of cement pastes with water to cement ratio of 0.23, 0.35 and 0.53 were in situ continuously monitored by using electrodeless resistivity apparatus. Isothermal conduction calorimeter was also used to measure the hydration degree. The quantitative relationship between electrical resistivity evolution of paste and development of pore structure was proposed during hydration process. The results show that four stages (dissolution, induction, acceleration and deceleration) are identified according to the characteristics of electrical resistivity and its differential resistivity curves. In addition, a lower water to cement ratio shows a smaller capillary porosity and constriction factor as well as a higher tortuosity factor, resulting in a higher electrical resistivity of bulk paste, and the reverse phenomenon is observed with the electrical resistivity of pore solution.

Abstract:There are some controversies on influences of stone powder on performances of concrete, and its content determination is one of the hot issues of manufactured fine aggregate (MFA) concrete. Slump and compressive strength of limestone MFA concrete were analyzed on contents of stone powder for middle-low strength and different flowability concrete. The experiment results show that there are different optimums percent of stone powder of MFA, such as 5, 10, and 20 for different types of concrete, but the water-powder ratio for them is 0.4. It is concluded that optimum percent of stone powder may be predicted by water-powder 0.4 for middle and low strength MFA concrete.