Abstract:The progressive collapse resistance of reinforced concrete plane frames removed post column was analyzed based on Pushdown method. The effect of the floor layers on the progressive collapse resistance capacity and the vierendeel action of the damage structure was investigated. At the same time，a method for calculating the system reliability of the reinforced concrete frame structure removed post column was proposed. By simulating static test of constrained beam，single-layer plane frame and multi-layer plane frame，the correctness of the finite element model based on OpenSees was verified. The 2，4，6 and 8-layer reinforced concrete frames were analyzed，and the Pushdown curve and the frame beam axis force curve were obtained. The bearing capacity enlargement coefficient was calculated by the Pushdown curve，and the correlation between the frame beams was set by the relative size of the strain of the frame beam. The results show that with the increase of storey，the average bearing capacity of single story decreases，and the probability of progressive collapse of structural system increases.

Abstract:It is important to guarantee strong bonding between UHPC and asphalt surface to prolong the service life and avoid the diseases of the bridge deck，such as slippage and delamination. Finite element analysis and laboratory tests were conducted to investigate the influences of kinds of binders and ambient temperatures on bonding performances. The test results showed that the ambient temperature had a great effect on the interface strength by shear and pull-off tests of composite specimens. Compared with normal temperature （20℃），the interface bonding performances had been decreased greatly at high temperature（60℃）. Epoxy binders named KD-HYP and 202 exhibited better bonding ability than epoxy asphalt，Shell HV and rubber asphalt. Although epoxy asphalt had higher bonding strength than Shell HV and rubber asphalt at high temperature，but there were no obvious differences among them at normal temperature. The finite element simulation of the second Dongting Lake Bridge showed that the maximum shear stress between UHPC-SMA was 0.696MPa and 0.422MPa respectively at 20℃（normal temperature） and 60℃（high temperature），and the maximum tensile stress was 0.167MPa and 0.152MPa respectively. The researches indicate that，under the most unfavorable load combinations consisting of overload，braking hardly and dynamic loads，KD-HYP and 202 can meet the requirements of interface bonding stresses，and are of sufficient safety at normal temperature and high temperature. But Shell HV，rubber asphalt and epoxy asphalt cannot do at high temperature.

Abstract:This paper presented a simple method to improve the connection degree of GFRP-concrete composite decks and further improved the ductility of the composite decks. The connection strength of GFRP-concrete interface was changed by using different gravel coverage. The bending stiffness was significantly changed due to the connection mechanism change after the GFRP-concrete interface failed, and the ductility was also further improved. Five full-size T-shape GFRP-concrete composite decks were tested to explore the difference of the mechanical properties of composite decks with different connection degree. In the experiment results, deformation, slip at the end of decks, strain distribution and failure modes were mainly examined. The experimental results show that although the GFRP-concrete interface of the specimen with unbonded interface is smooth, partial composite action between GFRP plate and concrete can be observed. A variable gravel coverage changed the failure mode, ultimate load, connection degree and ductility. A reasonable gravel coverage can provide an effective composite action before slip at the end of decks occurs, offer a large deformation after slip occurs, and not significantly reduce the ultimate load. At last, the consistency of theoretical results with experimental results demonstrates that the cracking load and shear capacity can be predicted by using the methods in the paper.

Abstract:To calculate the deflection of steel-concrete continuous composite girder accurately, the equilibrium differential equations and the corresponding boundary conditions for calculating the deflection of steel-concrete composite girder were derived by using the energy variational method. The influence of shear deformation of composite girder and the slip effect between steel girder and concrete slab were considered. By introducing the boundary conditions of two-span continuous steel-concrete composite girder under uniformly distributed load, the deflection calculation formula of the steel-concrete continuous composite girder was obtained. The correctness of the deflection calculation formula was also verified. A further analysis of the deflection of steel-concrete continuous composite beams shows that the slip effect reduces the stiffness of steel-concrete continuous composite girder, causes additional deflection, and increases the negative bending moment of the girder at the middle fulcrum, which adversely affects the stress of the concrete slabs. Slip displacement between layers decreases with the increase of shear stiffness of shear connectors. When the shear stiffness of shear connectors is less than 1200 MPa, the additional deflection caused by slip effect is larger, and the influence on the total deflection is greater. The influence of slip effect on the deflection of the composite girder should be considered. However, when the shear stiffness of shear connectors is greater than 1200 MPa, the additional deflection caused by slip effect is small and the influence on the total deflection is small. The influence of slip effect on the deflection of the composite girder can be ignored.

Abstract:The dynamic prediction of bridge extreme stress based on health monitoring stress data was studied. Considering the monitored stresses’ periodicity， randomness， dynamic characteristics and so forth，firstly，the Fourier Dynamic Nonlinear Model（FDNM） of bridge monitored extreme stress was built，and， with Taylor series expansion technology， FDNM was approximately transferred into the Fourier Dynamic Linear Model（FDLM）；secondly， with Bayes method， the Bayesian FDLM（BFDLM） was built based on the monitored extreme stress data，and the one-step forward prediction distribution parameters of monitored extreme stress and distribution parameters of posterior stress state were dynamically predicted； finally， the monitored extreme stress data of an actual bridge was provided to illustrate the application and feasibility of the proposed models and methods. The results show that the proposed BFDLM can reflect bridge extreme stresses' periodicity， randomness， dynamics and so forth，which can provide the theoretical foundation and application approach for bridge monitoring extreme stress prediction.

Abstract:Crack occurrence is a visual representation for brick masonry damage. In this paper, crack evolvement law of ancient brick masonry under uniaxial compressive loading after freeze-thaw cycles was investigated. The loading-deformation curve and crack data of ancient brick masonry were recorded. For each masonry sample, its initial cracking load was determined synthetically by three reference values based on loading-deformation curve, length of single crack, and crack development. After the crack length at every loading level was obtained, the normalization processing was performed. The trilinear model was used to simulate the relationship between the crack length and loading level. Crack of the ancient brick masonry occurred earlier and faster than that of modern brick masonry: the value range of initial cracking load was from 0.4 fm（compressive strength） to 0.6 fm，which averaged about 0.52 fm； when the stress reached 0.7 fm，critical crack was initiated; when the stress reached 0.93 fm，masonry entered into the ultimate state. The masonry damage was described by crack density, which was defined as the crack length per unit area. The development rule of crack density was proposed with a final value of 8.7 m/m2. Compared with the results of similar tests in references, it was found that crack density was a relatively stable indicator, which has good potential for further study and application.

Abstract:In order to study the effect of building envelope structures on the structural performance of traditional timber building in the Yangtze River region and to provide the calculation basis of the seismic performance and wind-resistant performance of this type of buildings, Jindai Building，a typical traditional timber building in the Yangtze River region，was taken as an example, and the model updating methods of this building were studied by the methods of finite element analysis and structural dynamical characteristic tests. First, by using finite element software SAP2000, the structural model without consideration of building envelope effects and the three structural models considering building envelope effects were established to analyze their dynamical characteristics. Then, the structural dynamical characteristic test was carried out on site. By comparing the results of the finite element methods and the dynamical characteristic test, some important results can be drawn as follows: in terms of natural vibration frequency, the results of these three updating models considering building envelope effects are obviously higher than that of the model without consideration of building envelope effects. The increment of the equivalent diagonal strut model is 220%～307%, the increment of the equivalent diagonal strut and shell element model is 228%～345%, and the increment of the integral simplified model is 230%～295%, but the first mode shape and second mode shape of this updating model are changed. The results of the equivalent diagonal strut model are very close to the results of the dynamical tests, and the error is smaller than 15%. Therefore, the equivalent diagonal strut model is the best updating model for this building. The results of the equivalent diagonal strut and shell element model are also close to the results of the dynamical tests, and the error is smaller than 20%. Thus, the equivalent diagonal strut and shell element model is the second-best updating model for this building. The results of the simplified model are obviously different from the results of the dynamical tests, so that the integral simplified model is not suitable for the model updating of this building. Finally, the equivalent diagonal strut model is recommended to study the structural performance of this type of traditional timber buildings whose envelopes have no cracks, for example, the condition of environment vibration, wind-induced vibration，and frequently occurred earthquake. The structural model without consideration of building envelope effects is recommended to study the structural performance of this type of traditional timber buildings whose envelopes are failed, for example, the condition of design earthquake or rarely occurred earthquake.

Abstract:Based on the identification data of damping ratios measured from seven large cooling towers in domestic and taking the high-level water cooling tower as an object， four kinds of damping ratios （0.5%， 1%， 2% and 3% respectively) were set up to calculate the wind-induced responses by complete transient analysis. The calculated results were compared with these calculated under standard damping ratio （5%). On this basis， the influence of the damping ratio values on average and pulse responses of wind vibration of high-level water cooling tower was refined， the wind-induced vibration coefficients were calculated based on six different responses of wind vibration and three kinds of equivalent target under damping ratios. The influence law of different damping ratios， response targets and position on coefficients of wind vibration were summed up， and the damping ratio and meridian height were taken as an objective function of the wind vibration coefficients and the fitting formula was proposed by using the nonlinear least-square method. The main conclusion can be provided as references for damping ratio parameters of the high-level water cooling tower.

Abstract:The effects of water cement ratio, sand binder ratio and dosage of water reducer content on the shrinkage of foamed concrete with dry density of 800 kg/m3 were studied by orthogonal test method to obtain the optimal mix proportion, which is beneficial to shrinkage performance of foamed concrete. According to this mix proportion, the effects of polypropylene fiber, glass fiber, plant fiber, expansive agent and shrinkage reducing admixtures on the shrinkage performance of foamed concrete were further studied. At the same time, the effects on the fludity and compressive strength were also examined. The best added component was analyzed by using the radar chart, and the mechanisms of the shrinkage reduction of fiber and admixture were explained by the macro pore structure and the microstructure under SEM electron microscope. The results show that，considering the 3 days autogenous shrinkage and 28 days drying shrinkage, the optimum mix proportion is 0.5 of water cement ratio, 1 of sand binder ratio, and 0.5% of the dosage of water reducer content. Fiber,expansive agent and shrinkage reducing admixtures can effectively reduce the autogenous shrinkage and drying shrinkage of foamed concrete, and the law of their shrinkage resistance is as follows:shrinkage reducing admixtures > expansive agent > fiber. The best addition component is 1% mass fraction of shrinkage reducing admixtures, which can reduce the 3 days autogenous shrinkage of the foamed concrete by 37% and the 56 days drying shrinkage by 57.5% on the premise of satisfying the fluidity and compressive strength of foamed concrete. Furthermore, the incorporation of fiber causes partial foam breakage, resulting in greater drying shrinkage of the matrix. However，its physical constraint on foamed concrete reduces the final drying shrinkage. The shrinkage mechanisms of expansive agent and shrinkage reducing admixtures lie in its own chemical action.

Abstract:The existing methods can hardly consider the actual state of geogrid ribs under loading，which can cause underestimating the settlement of the geogrid-encased stone column (GESC) composite foundation. The effective reinforced unit cell was employed as the analysis object, while GESC together with soil was assumed in constant strain distribution and as linear elastic materials. Stone column was constrained by geogrid and earth ring at the same time, while the earth ring can be considered as a ring with earth pressure at rest provided by soil outside and bulging pressure caused by the stone column installed inside. Hook's law was then introduced to gain the stress-strain formula of the unit cell. A different method of settlement calculation for GESC composite foundation was established. The rationality of the results of this method was verified by an engineering example and was compared with the existing method. The result demonstrates that the method agrees well with the engineering example. Compared with the existing method, the relative error between the calculated value and measured value is +5.70%, which demonstrates that the method presented in this paper is safer and more accurate as a result of combined top loading and lateral deformation of GESC together. The parametric study shows that the replacement ratio has a significant influence on controlling settlement of composite foundation, and increasing the replacement ratio can effectively reduce the pile - soil ratio and settlement of composite foundation when a certain level load is applied.

Abstract:The pile was supposed to be elastic and the plane-strain model was adopted to simulate the surrounding soil. By the means of Laplace transform and impedance function transfer method, the dynamic response of tapered pile was obtained. Then, by parametric method, the influence of pile and soil characteristics on the dynamic response of tapered pile was discussed. Meanwhile, the correctness of the theory was verified by model test. The results show that: 1）There is a critical pile diameter ratio at which the reflected signal from pile bottom is difficult to find, and the ratio increases as the pile grows； 2） Cone angle and pile length have a great influence on the dynamic response of tapered pile. However, in the case of small-diameter pile with a zero-diameter end, pile length doesn't have an obvious influence；3） Shear wave velocity of soil and vertical distribution of soil have a great influence on the dynamic response of tapered pile； 4） Good agreement is shown between experimental and theoretical results.

Abstract:By using the principle of stress release method, a numerical solution method of convergence-confinement characteristic curve was proposed for tunnels with various cross-sections based on the convergence-confinement analysis method. The validity of the proposed method was verified by comparison with the convergence-confinement analytical method, and compared with the usual numerical methods. Finally, the calculation error of the numerical solution method for convergence-confinement characteristic curve was analyzed. The results show that the numerical solution method of convergence-confinement characteristic curve is suitable for non-circular tunnel, and due to the stress release achieved by applying support reaction to nodes, the method is also suitable for the tunnel with complicated stress condition. Taking the Dianzhong diversion project as an example,the numerical solution method of convergence-confinement curve was compared with the calculation results of the convergence-confinement analytical method, and the validity of the numerical solution method of convergence-confinement curve was verified. Despite some error in the result of the numerical solution method of convergence-confinement curve, the overall relative error is less than 10%. The application of the numerical solution method for convergence-confinement characteristic curve is more extensive,which can provide reference for the optimization design of primary support and safety evaluation of tunnel engineering, and the numerical solution method has a certain value of engineering application.

Abstract:This study dealed with the applicability of Cohesive Zone Model (CZM) on the cold-mix foamed asphalt concrete by analyzing the results of both numerical simulation and laboratory tests comparatively and statistically. Based on CZM, 3D model specimens were built up for cold-mix foamed asphalt concrete by applying Matlab Convex Hull Algorithm and 3D ODEC Algorithm. Meanwhile, virtual splitting tests of the mixtures with different gradations were also carried out. The study indicates that the combination of Convex Hull and 3D ODEC Algorithm is able to simulate the coarse aggregates angularity. The simulated trend of strength-deformation curve obtained from the virtual splitting test is similar to the actual pattern, which suggests that the CZM-based 3D discrete element simulation can be applied to the design of cold-mix foamed asphalt concrete.

Abstract:This paper studied the performance of bio-asphalt and rock asphalt composite modified asphalt binder. To investigate the change of the properties of asphalt subjected to the composite modification of bio-asphalt and rock asphalt, tests on the penetration, softening point, ductility, viscosity and RTFO short-term aging of the bio-asphalt and rock asphalt composite modified asphalt binder with different content in the range of 60% were carried out. The test results and analysis indicate that when the 25 ℃ penetration of bio-asphalt and rock asphalt composite modified asphalt is consistent with the base asphalt binder, the ratio of rock asphalt to bio-asphalt are proportional to the content of composite modifier; The penetration index PI value of composite modified asphalt binder increases and the temperature sensitivity improves. The high temperature performance of composite modified asphalt decreases slightly first and then increases, and reaches its original level when the content of composite modifier is about 15%; The retained penetration of composite modified asphalt after RTFO decreases slightly first and then increases always, and finally reaches its original level when the content of composite modifier is about 20%, and the change of softening point increases obviously; However, the ductility of asphalt decreases significantly with the addition of the composite modifier. However, the bending test of asphalt mixture demonstrates that the addition of composite modifier does not decrease the low temperature performance of asphalt and improves it to some extent. In a whole, within the content from 20% to 30%, replacing some petroleum asphalt with compound modifier improves the performance of asphalt. Furthermore, the upper or lower content limit can be broadened appropriately when different performance requirements are to be met.

Abstract:This paper presented a new efficient cyclone separator, which can block the particles moving to the inner vortex. The new cyclone separator was obtained by setting a group of swirling blades with the same direction as the rotating direction of the air flow in the internal and external vortex interface of the traditional separator. The Reynolds model and discrete phase model were selected to simulate the gas-solid two-phase flow, and the discrete random walk model was used to study the turbulent dispersion of particles. The accuracy of the numerical simulation was verified by comparing with the experimental data. The performance between the traditional cyclone and new efficient cyclone was compared by numerical simulation. Moreover, the optimization of the swirling blades was performed. The results show that, compared with the traditional cyclone, adding the swirling blades effectively improves the separation efficiency, which can decrease the cut-off size by 60%~70% and increase the pressure drop by 19.3% only. Further, the effect of swirling blades on the separation efficiency of small particle size and low density particles was more significant.

Abstract:The optical and dynamic heat-transfer models of aerogel glazing system were developed and validated by experiments. The models of other five common glazing systems (including double, triple and 3 kinds of Low-E double glazing systems) were also built based on the existing methods. The index of efficient solar energy was introduced to evaluate glazing's annual suitability, while the index of accumulative hourly heat gain was used to evaluate the glazing systems' suitability in the heating or the cooling season alone. The simulation results show that employing aerogel glazing system in severe cold region (Harbin), cold region (Beijing), hot-summer cold-winter region (Changsha) and temperate region (Kunming) can achieve energy efficiency. The differences of the efficient solar energy between aerogel and double glazing systems in these cities are 266.3, 158.6, 114.3 and 40.5 kWh/m2, respectively. The order of suitable level for employing aerogel glazing system is as follow: Harbin> Beijing> Changsha> Kunming.

Abstract:Experiments of three cases, such as steady operation, unsteady operation with opened door, and unsteady operation with opened window, were carried out in a residential room having air carrying energy radiant air-conditioning system. Three Computational Fluid Dynamics (CFD) models were established based on the experimental results to study the indoor thermal environment and condensation risk of these three cases. The synergistic operation model described by the temperature synergistic formula, relative humidity synergistic formula, PMV synergistic formula, and energy consumption synergistic formula was proposed based on the thermodynamic analysis. The verified CFD model shows that the vertical temperature gradient between the human head and ankle height is less than 0.6 ℃ and the air velocity in the occupied zone is about 0.1 m/s. There is a boundary zone with low condensation risk under the radiant orifice plate of both steady and unsteady cases for about 12 cm and 6~8 cm, respectively. The synergistic influence analysis of air supply and opening degree on PMV and energy consumption was conducted based on the unsteady experimental results. The synergistic evaluation index of mixing ventilation was presented, offering optimal advice on air supplying settings for different opening degrees of outside door and window.