Abstract:

Abstract:In order to study the seismic concept of high-rise diagrid tube-core tube structures,CFST diagrid tube-concrete core tube structures were designed based on typical project.The elastic-plastic time history analysis method is adopted and the components yield order is summarized based on their plastic developing processes.The influences of wall thickness,inclined column cross section and coupling beam height on the components yield order are studied and the distribution of seismic fortification lines between tubes are presented.The main factors exerting influence on structure lateral stiffness are analyzed and the key components of structure lateral stiffness and plastic energy dissipation are achieved.The seismic concept of this structure is discussed considering the three level earthquake fortification criterion and components yield characteristics at last.

Abstract:For the convenience of industrialized production and site operation,specification design of PPCRP (precast prestressed concrete ribbed panels) is discussed. In order to obtain ultimate bearing capacity,bending rigidity and crack resistance,four PPCRP with two types of spans are studied,and the results show that PPCRP can satisfy the requirements of bearing capacity in construction phase and can serve as stay-in place formwork. To verify the mechanical property,shear behavior on contact interface of composite member and moment redistribution factor of continuous composite member,two single-span composite members and one two-span continuous composite member are studied. It is indicated that computational method for bearing capacity of composite member can be the same as cast-in-situ concrete slab. Besides,section strain analysis for composite member in two-loading is conducted,which suggests that thickness of bottom board can be used as calculated height with the consideration of two-loading.

Abstract:The buried box girders in the mountain city sewage pipeline system would be turned into simple-supported girders because of the removal of the foundation caused by landslide.This change of supporting would result in the failure risk of pipeline structure.The static properties of the buried box girders with small depth-to-span ratio in simple-supported condition are experimentally analyzed.The failure pattern,shear behavior and shear lag effect of the buried box girders in simple-supported condition are studied.The shortages in the present design codes for the calculation of shear capacities of the box girders are also discussed.It is shown that under the vertical uniformly distributed load,the crack distribution of the box girders is uniform,and no major critical diagonal crack is formed,and the box girders lose the bearing capacity in the form of concrete diagonal rod crushing.As the main shear-bearing components,the stirrups devote much to shear capacity of the box girder after concrete cracking.The strains of the longitudinal rebars are affected by those factors such as the redistribution of internal force and cracks,so only few areas of the box girders show the shear lag effect.The change of supporting form leads to the premature cracking of concrete and affects the serviceability of the sewage pipeline.

Abstract:The finite element model involving geometric large deformation,materials and contact nonlinearity is established.Specimens of cold-formed steel quadruple-C built-up section members are simulated and the finite element models are proved to be valid.Then,numerical analysis on the behavior of specimens with different slenderness ratio and flange flakiness ratio are carried out,and then the axial bearing capacities of specimens are obtained.Based on effective width method and direct strength method (DSM) in related codes,two design methods of cold-formed steel quadruple-C built-up section members under axial compression are proposed:effective length method and correction factor method.It is shown that:the final failure characteristics of all specimens are local buckling and distortional buckling.In the case of not considering the reduction of effective length,the results calculated by each code are slightly lower than those of test and FEM when the slenderness ratio is less than 50,while the results are too conservative when the slenderness ratio is more than 50.

Abstract:A 3-D finite element model is established by ABAQUS to simulate the behavior of the joints with concrete-filled steel tubular (CFST) column to steel beam using external stiffening ring.The load versus deformation curves of this type of joints are compared between theoretical and experimental results,and in good agreement.Parametric analysis is performed to study the flexural load-carrying capacity of the joint.The width of external stiffening ring,the steel ratio of CFST column,the ultimate strength of steel beam,the strength of steel tube and beam,the concrete strength,the axial load ratio,and the beam to column linear stiffness ratio are considered as parameters.The simplified practical design approach is proposed based on parameter analysis of the flexural load-carrying capacity of these joints.The practical calculated values are in good agreement with the FEM results.

Abstract:With the flexibility-based fiber model,the seismic behaviors of RC structures with specially shaped columns,designed according to the current code,are analyzed under unidirectional rare earthquakes using nonlinear dynamic analysis method.The beam strength is calculated with or without consideration of the diaphragm and its reinforcement.The results are compared and the conclusion has been drawn that the bending capacity of beams would be increased due to the effect of diaphragm and its reinforcement,and which would change the failure mechanism of RC frames under rare earthquake,especially in high intensity areas.Therefore the influence of the diaphragm should be considered during the seismic design of the type of structure.

Abstract:In order to investigate the effective seismic capacity design measures of shear wall and to realize expected failure modes under strong earthquake,the existing problems in current seismic capacity design measures are pointed out through theoretical analysis.The effectiveness of the measures of Chinese seismic design code is verified by fine finite element dynamic time-history analysis of examples.Improving measures are then put forward and are verified through example analysis.It is shown the bending ductile demand of bottom section of shear wall increases too much based on moment capacity design measures of Chinese seismic design code 2001 in the rigid foundation assumption under rare earthquake action,and its bearing capacity for vertical axis force loses;the shear capacity design measures of current seismic design code would lead to shear failure in the stores above the bottom ductility strengthening area.Some improved bending and shear seismic capacity design measures of shear wall are proposed and are verified to be effective.

Abstract:As the self weight of cable affects mechanical behavior obviously with the inerease of span length.FRP (fiber reinforced polymer) cable that has the lighter weight than the conventional cables has advantage for long span structures.The analysis of single cable is the fundamental theory for the design of cable structures.Based on different considerations of gravity loads.the solutions of the single cable on gravity loads have three sets of solutions: parabola solution.catenary solution and elastic catenary solution.And the equations for the three sets of solutions are derived by taking the end tension force of cable as the control parameter.The comparison between FRP cables and steel cables is conducted by elastic catenary solution.and the results show that the lager span structure can be realized by FRP cables.The precision for the parabola solution and catenary solution is compared for stay cables and horizontal cables.and the proper ranges of both approximate methods are proposed.Based on the above methods.the ultimate span length of FRP cable and steel cable are analyzed.It is concluded that the ultimate span of FRP cable is 4.4 times larger than that of steel cable.

Abstract:Based on the formal solutions of the buckling eigen equation,the probability density evolution equation for the random buckling eigenvalue is derived considering the random wind loading.Taking the averaged wind speed at 10m height and roughness length as the random factors,the random buckling bearing capacity for a super-high cooling tower is then analyzed.Furthermore,both the mean and the standard deviations of the capacity are calculated.It is indicated that there exhibits a general shape for the probability density function of the random buckling capacity.And the mean of the random buckling bearing capacity is close to that one computed by the averaged parameter.However,the variation of the random buckling bearing capacity is between the corresponding values of averaged wind speed at 10m height and roughness length.

Abstract:The calculation theory of stability capacity of steel tube and coupler scaffold is currently an urgent problem to be solved.Based on the analysis of the stability behavior of steel tube and coupler scaffold with X-bracing,a series of simplified model and calculation formulas are put forward.In order to verify the rationality of simplified calculation theory presented,two full-scale tests are carried out.Compared with results from tests,the results from simplified calculation theory is well consistent with it.Therefore,it is concluded that the simplified model and simple formula own a considerable accuracy to forecast the critical load of steel tube and coupler scaffold with X-bracing under uniform load,which offers the reference for relevant researchers and designers.

Abstract:The process of chloride diffusion in concrete is time-dependent.The boundary element method (BEM) with a time-dependent diffusion coefficient is presented for chloride diffusion in concrete based on the suitable transformation of variables.The fundamental solution of the partial differential equation for time-dependent chloride diffusion in concrete is developed,and the compensation length of the diffusion field is defined as well as the compensation coefficient.The scheme of BEM with a time-dependent diffusion coefficient is developed.Two examples are given to demonstrate the accuracy and efficiency of the presented method and the rationality and the importance of the compensation length for the method.

Abstract:Spiral case is the core structure of powerhouse,therefore,it is critical to obtain its accurate stress and strain.Simplified algorithm is adopted to analyze the mechanical characteristics of preloading water-filled spiral case of a large hydropower project.The numerical results show that the adoption of preloading water-filled spiral case structure is feasible.The maximum stress of surrounding concrete mainly lies in the top of spiral case structure at various sections.The suitable internal pressure is 1.9MPa.The stress of surrounding concrete of spiral case is mainly caused by water pressure,and the effect of upper loading is limited,which is only about 5% to 24%.

Abstract:The behavior of loose sand-structure interface under the high frequency cycle shearing is analyzed by using Particle Discrete Element Method (DEM).The changes of sand box porosities of DEM model and sand volume strains are examined in detail.The results show that sand volumetric shrinkage due to shearing is not obvious in spite of the larger loose sand particle friction coefficients and particle stiffness.The particle stiffness ratio has a little effect on the mechanical properties of sands.In addition,the decrease in volume of sand under shearing is more obvious with the increase of the confining pressures.Moreover,the decrease in volume of loose sand under shearing is greater with the increase of the high frequency cycle shear amplitude and the shear frequency.

Abstract:The hazard assessment of the highway landslide induced by the extreme rainfall is a complicated systemetic issue.By combining the modified analytic hierarchy process and the fuzzy comprehensive evaluation,all the factors that influence the highway landslide are analyzed.And the comprehensive evaluation index system as well as the danger rating is established.In the process of evaluation,different rainfall's dynamic weighting system is fixed,and then the membership of continuous and discrete index are calculated respectively by using the trapezoid membership function formula and expertise assignment,and finally case study is carried out.It is shown that this method is suitable and rational to evaluate the highway landslide induced by extreme rainfall.

Abstract:To calculate the earth pressure in saturated soil mass subjected to earthquake forces and groundwater seepage,two cases,in which the seepage states are steady but the shapes of the flow lines are different,are investigated.The two cases are Case 1,in which the flow line is vertical downward,and Case 2,in which the flow line is curve toward retaining wall.Based on the pseudo-static method and Coulombs theory,the formula to calculate the seismic active earth pressures in Cases 1 and 2 is proposed.The comparison of the results with the published work indicates that the suggested formula is reasonable.The influence of the soil effective internal friction angle on the seismic active earth pressure is also discussed.The results indicate that the total seismic active earth pressure is decreasing nonlinearly with the increase of the soil effective internal friction angle.And the decrement of the total seismic active earth pressure in Case 2 is larger than that in Case 1.

Abstract:By using near crack line analysis method and Mohr-Coulomb strength criterion,the elastic-plastic solution for near crack line of an eccentric cracks loaded by the pore water pressure under large scale yielding condition is analyzed.The elastic stress fields,the plastic stress field,the unit normal vector of the elastic-plastic boundary near the crack line,the elastic-plastic stress fields near crack line are identified.The change pattern of the length of the plastic zone and the pore water pressure is presented.Besides,the elastic-plastic analytical solution for an eccentric cracks loaded by the pore water pressure is obtained.

Abstract:A moisture migration test for unsaturated clayey loess along Shenyang-Haerbin Express Railway for Passenger Line was carried out to investigate the water movement of soil in an open system with constant temperature condition.It is shown that moisture transfer is mainly caused by matrix potential and gravitational potential energy.The water content by volume gradually decreases from the bottom to the top of specimen.Over time the capillary water height increases by the power function and eventually reaches a stable value.The water flux decreases with time by the logarithm function.Based on the model test,finite element method is adopted to simulate the moisture transfer process in soil under isothermal condition.It is found that the numerical results are in good agreement with the experimental data.The model is thereby used to simulate the rise of groundwater in the subgrade soil.During the whole process of moisture movement,pore water pressure gradually decreases from the bottom to the top of sample.The rapid change of pore water pressure in the early process contrasts with slow change in the late process.The pore water pressure has a linear change along the specimen when the seepage reaches steady state.

Abstract:By using a simple shear apparatus that is developed from RMT-150B,a series of simple shear tests of interface between saturated sand and structure under high normal stress were carried out to study constitutive law and shearing stiffness of interface to provide some theoretical evidences for design and calculation of projects concerned with mechanical problem of interface.In test,sand was consolidated in upper shearing box firstly,then,shear was started and testing data was recorded under high and constant normal stress.During the process,sand can deform relatively freely.It is shown that the relation curve between shear stress and shear displacement under high normal stress in simple shear tests is different from that in direct shear tests,and the complete shearing deformation process of interface under high stress can be described as a nonlinear elastic-perfect plastic form;Weibull distribution with three parameters can overcome the mathematical deficiencies of hyperbola in NEPP.The new model which is established by substituting Weibull distribution for the hyperbola of NEPP better agrees with the testing data.The regressive results of the initial shearing stiffness demonstrate that the linear function is slightly better than power function to express the relation between the initial shearing stiffness and normal stress.Based on the new interface model,the formula of tangential shearing stiffness is proposed,meantime,the change trend of tangential shearing stiffness of the new model is compared with that of NEPP.

Abstract:In order to establish “Evaluation Standard for indoor thermal environment of civil buildings”,acceptable temperature range of indoor environment without air conditioning and heating in hot summer and cold winter zone is indispensable.A two-year field measurement and questionnaire survey were carried on from 2007 to 2009 in Chongqing,which focused on office buildings and residential buildings.After the analysis of indoor and outdoor environment,occupants evaluation and thermal adaptability,a method to obtain the acceptable temperature range,was proposed.Regressing data by temperature range,and combined with human physiological and psychological experiments,the acceptable temperature range of environment without air conditioning and heating in Chongqing was determined according to outdoor air temperature changes in one year.A Comparation of methods to determine the acceptable temperature range in some international standards was discussed.

Abstract:Thermal adaptation after earthquake is analyzed under the special condition of destructed houses and fundamental facilities.Field investigation and questionnaire survey were carried out after Wenchuan earthquake.The thermal adaptation model is also used to study the capacity variation of thermal adaptation.Through the comparison with the thermal adaptation under the common condition,it shows the thermal adaptation under the special condition has improved.And the causes for the changes are analyzed.

Abstract:Experiment of aerated concrete evaporation under certain initial water content was carried out in the hot-humid climatic wind tunnel.By orthogonal experiment, the influencing factors of evaporative heat transfer are analyzed.Measured from the significant and persistent of impact, solar radiation is the greatest influencing factor, then followed by the sample thickness, air velocity is in the third order, and the last is ambient air temperature.Air relative humidity and the interaction with air temperature have no statistically significant influence.It is observed that the most dramatically significant level of infrared power, air velocity, air temperature and sample thickness on the evaporative heat transfer are 400 w/m2, 1.5 m/s, 30℃ and 100mm respectively.This is because the increase in infrared power and air temperature may have caused a rapid increase in the temperature at sample surface, resulting in excess water loss of surface layer to desiccation and thus in retarding the interior moisture migrating up to the surface for further evaporation.And over-high air velocity and over-thick material may also have negative influence on evaporation.

Abstract:The commonly used indicators are often too slow to reflect the operating status in time.Confronted with lacking reliable early-warning indices in the single-phase anaerobic digestion for kitchen waste which is easy to decay,lab-scale experiments of start-up and continuous operation process of anaerobic digestion for kitchen waste were carried out in the single-phase anaerobic reactor which is self-designed under mesophilic conditions.Those values which reflect the capacity of acidity-basicity resistance,including the ratio of bicarbonate alkalinity to total alkalinity (BA/TA),absolute testing value of volatile fatty acid (VFA) and the ratio of total concentration for volatile fatty acid to bicarbonate alkalinity (VFA/BA),are determinated to be the early-warning indices for acidification and imbalance of single-phase anaerobic digestion for kitchen waste.It is considered that,when VFA/BA＞0.8,BA/TA＜0.4 and VFA＞3000mg/L,buffering capacity of the system is very poor,and the system might be out of control.Therefore,an immediately steps must be taken.While,when BA/TA≥0.7~0.8 and VFA/BA＜0.4,the alkalinity of system is relatively better and the process can be operated with higher organic volumetric loading,which can raise the biogas-producing efficiency and get economic benefit.

Abstract:Pilot scale sewage sludge ecological stabilization system was conducted for sludge dewatering,mineralization and stabilization.The study was performed from 2005 to 2008 on a bed with a total area of 80 m 2.Influent total solid,volatile solid and water content were averaged 22.34 g/L,7.76 g/L and 97%.Sludge loading rate was averaged 0.691 kg(TS)/m 2·d.The first two years were sludge loading period and the other two years were natural stabilization period.The percolate COD removals ranged from 60%~80% in the first year,and from 40%~50% in the second year,with 100~200 mg/L of effluent COD concentration.During the first two years,the percolate did not filtrate downwards evenly.Part of percolate filtrated downwards along stems,roots and cracks existing in dried sludge which had lower flow resistance.During the natural stabilization periods,sludge water contents decreased to 34.3% and 30.5%,and organic matter contents decreased to 16.8% and 10.24% in the third and forth years,individually.Total nitrogen and total phosphorus contents of stabilized sludge were averaged to 0.98% and 0.27%.It was found that plant biomass and nutrient components in the system were higher than that of native ones.

Abstract:The removal of Phthalate Esters (PAEs) from water was measured by using enhanced coagulation technology.Cationic coagulant poly-diallyl-dimethyl-ammonium-chloride (PDMDAAC) and polyacrylamide (CPAM) were employed to remove the dimethyl phthalate (DMP),and the residual concentration of DMP is determined by the high performance liquid chromatography (HPLC).During the coagulation/flocculation process,parameters such as coagulant dosage,pH value,and sedimentation time are investigated.The results show the use of coagulant PDMDAAC/CPAM together has better coagulation effect than PDMDAAC.DMP removal rate is 99.87% when initial DMP concentration is 0.50 mg/L,the addition of a PDMDAAC dosage 50 mg/L,the addition of a CPAM dosage 2.5 mg/L,pH value 6.0 and sedimentation time 3 hours.Therefore,the removal of PAEs by coagulation is effective,and the application of coagulation by PDMDAAC/CPAM in water supply will enhance the removal of PAEs and at the same time reduce the water turbidity.

Abstract:In order to investigate the peak concentrations when NO -3-N and DO are regarded respectively as electron acceptors during phosphorus uptaken process,sequencing batch reactors (SBRs) are used to do parallel experiments. In an enhanced biological phosphorus removal (EBPR) system operated as anaerobic/ aerobic mode,phosphorus uptaken processes were investigated when NO -3-N concentration is 50 mg·L -1,75 mg·L -1,100 mg·L -1 and aeration rate is 16 L·h -1,28 L·h -1,40 L·h -1,respectively. The results show that,when internal carbon source is sufficient,the key factor to determine phosphorus uptaken rate is not the electron acceptor concentration,but whether sufficient electron acceptor can be supplied to the system timely. Compared with DO,NO -3-N is a less efficient electron acceptor. Meanwhile,the amount of NO -3-N denitrified and the amount of PO 3-4-P uptaken show a linear relationship,which means that the denitrification and phosphorus removal bacterias can exist in EBPR operated as anaerobic/ aerobic mode,and the calculation shows that its proportion can reach up to 17.70% in the total phosphorus accumulating organisms (PAOs). It is less practical to use pH variation curves as a strategy to control phosphorus uptaken process. The peak concentrations of NO -3-N and DO as electron acceptor during phosphorus uptaken process are 50.00 mg·L -1 and 0.4 mg·L -1,respectively.