Abstract:In order to create a reinforced concrete shear wall structure with good energy dissipation and resilience，a kind of ultra-high performance concrete RPC （Reactive Powder Concrete） shear wall structure composed of ordinary reinforcement and CFRP （Carbon Fiber Reinforced Polymers） was presented. A nonlinear finite element model using nonlinear finite element software DIANA was established to analyze the seismic performance of reinforced concrete shear walls. The applicability of the model was verified by the test results in this paper and other references. Based on the constructed model，the seismic behavior of normal concrete and RPC shear walls with different reinforcement types was analyzed. The results showed that，in terms of the analyzed situation，the ductility coefficient of reinforced RPC shear wall was increased by 42% when compared with that of reinforced concrete shear wall due to the better ductility of RPC material. Compared with reinforced concrete shear wall，the energy dissipation capacity of RPC shear wall reinforced with CFRP bars for wall and ordinary reinforcement for side columns was increased by 51%，the ductility coefficient was increased by 30%，and the self-resetting capacity coefficient was increased by 25%. It is verified that the proposed hybrid reinforced RPC shear wall structure system has good comprehensive seismic performance. The reinforcement ratio of CFRP longitudinal reinforcement in shear walls with mixed reinforcement should be between 0.5 and 1.0 of ordinary longitudinal reinforcement in side columns.

Abstract:In order to study the influence of residual mud during construction process and steel pipe with different radius-thickness ratio on the flexural behavior of concrete filled steel tube, six steel tubular composite pile specimens were prepared by simulating underwater pouring of concrete for bending experiment and cross-section measurement. Through the test, M-um，M-Φ curves，flexural resistance and stiffness of these specimens were obtained. The test results show that the existence of mud weakens the stiffness and flexural resistance of concrete-filled steel tube by approximately 5%~25% and 5%~10%, respectively. The smaller the radius-thickness ratio is, the more obvious the influence of mud is. The steel tube and concrete no longer meet the section assumption under the influence of the mud. The flexural capacity calculated by the unified theory agrees well with the test value, but with the increase of mud thickness, it gradually becomes larger than the test values, which leads to the reduction of the reserve for safety in design. The coefficient of the stiffness formula is about 0.1~0.4.

Abstract:To improve the construction convenience of precast component reinforcement connectors and connection efficiency, grouted sleeve lapping connector of two bars was put forward, and 12 type II specimens with varied lap length and 63 type III specimens with varied lap length and bar diameter were tested under tensile load. The failure modes, ultimate bearing capabilities, load-displacement curves, and strains of bars and sleeves were discussed. The formulas of the average bonding stress were proposed. Like type I joint with single reinforcement, bar fracture and bar-grout bond-slip are two typical failure modes of the specimens. The tensile strain in the ring direction at the end of the sleeve is greater than that in the middle of the sleeve. In the middle of the sleeve, the tensile strain in the ring direction near bars is greater than that away from bars. For specimens with the same diameter that failed due to bar fracture, transverse confinement provided by the sleeve decreases as the lap length increases. The restraint force of elliptical sleeve of type III joint on grouting material is less than that of circular sleeve of type I joint, so there is not obvious yield steps on rebar outside of sleeve connector type III at late loading. This is also the reason why the tensile strain in the ring direction, at far away bars in the middle of the sleeve, does not show the increasing trend with the increase of diameter, but connector type I shows. Besides, the lap length of type III joints is more larger.

Abstract:In order to avoid failure of the half grout sleeve splice of rebars in prefabricated concrete structures after fire and serious consequences，27 14 mm-half grout sleeve splicing specimens of rebars were manufactured to study their mechanical properties by unidirectional static tensile test after high temperature. The test results showed two failure modes of the specimens after high temperatures including fracture and pull-out of rebars, in which the latter one was more likely to occur when the specimens were cooled by water. During the tensile process, the relative slip can occur between the sleeve and the rebar connected at the grouting side, and the slip increased nonlinearly with the increase of the temperature. Based on the test results after 600 ℃ high temperature and the existing bond strength formulas，suggestions were given to avoid the pull-out failure of rebars after high temperature. According to approximate analysis of steel slip in elastic stage，the quadratic function curve between the slip and temperature under natural cooling after high temperature was obtained.

Abstract:In order to improve the calculation accuracy of core steel strain, a formula for the core strain of buckling-restrained braces（BRBS） addressing the stiffness of BRB-gust plate was proposed so as to ensure BRBS yielded as designed. The stiffness of the welded joint plate is firstly derived, and the core strain formula considering the stiffness of the gust plate is subsequently established by using the geometric relationship between the frame and BRB. The pseudo-static test of the full-scale buckling-restrained brace frame and finite element analysis were conducted to verify the accuracy of the formula. The results from the formula，experiments, and finite element analysis are all in good agreement, and 60% of accuracy improvement can be achieved when calculating the story drift at the time of BRBS yielding, which demonstrates that the proposed strain formula is applicable to the optimization design for the core steel of BRBS.

Abstract:Through the axial compression test of eight fiber reinforced polymer（carbon，glass and basalt）confined stub concrete filled square steel tubes（CCFT），this paper reveals the mechanism and the failure model of this kind of composite column. The test results indicate that carbon fiber reinforced CCFT has the highest axial load and best ductility. And the axial load capacity and the ductility increase with the FRP confinement strength. Under the same FRP confinement level, the basalt fiber CCFT has a better ductility than the glass fiber CCFT. A formula for the calculation of bearing capacity of the square CCFT columns is also proposed. The analytically calculated results are shown to be generally in good agreement with the experimental results from this study and other research.

Abstract:In order to explore the failure rule and protection technology of masonry walls under the combined effects of blast and fragment loading, the finite element program ANSYS/LS-DYNA was used to establish the model of masonry walls, fragments and explosives. The effects of the scaled distance, fragments size and initiation points on the displacement response of masonry walls were obtained. Both the ultimate load produced by explosive that the masonry walls can resist and the economical protective method of masonry walls under the protection of polyurea elastomer and steel mesh were obtained. The results show that the research method was reliable according to the comparison between the test results and simulation results. The scaled distance cannot be used to judge the damage severity of masonry walls under the blast and fragments loading. Decreasing the size of fragments can increase the damage of masonry walls in the same condition of fragments quality. The effect of different initiation points on the damage level of masonry walls was weak. The protection of polyurea elastomer and steel mesh can improve the blast resistance of masonry walls. When the distance from explosion was 1.2 m, the masonry wall protected by 5 mm polyurea elastomer and steel mesh can carry the load produced by the quality of equivalent TNT explosive between 8.296 kg and 11.376 kg. When the distance from explosion was 1.2 m and the equivalent TNT explosive quality was 2.4568 kg, 3 mm polyurea elastomer and steel mesh were the economical protective measure. The results can provide references for masonry walls anti-explosion theory and protection technology.

Abstract:To evaluate the seismic performance of single-layer spherical reticulated shell, the randomness and non-stationarity of seismic excitations need to be sufficiently taken into account. In conjunction with the probability density evolution method (PDEM), the probabilistic information of dynamic response and reliability can be readily obtained. First, the random function based spectral representation method is employed to model the fully non-stationary seismic ground motions, which meets the requirements of different fortifications. Moreover, the average response spectrum accords well with the target response spectrum. Then, the instantaneous probability density evolution process of the shell’s maximum displacement is investigated from the perspective of PDEM. Further, two indices, which characterize the failure of the shell structure, are selected from macro and micro levels, respectively. By introducing the idea of equivalent extreme-value event, one can obtain the extreme value distribution of response for seismic reliability analysis. Finally, through carrying out the parametric analyses, the effect of different parameters on the seismic reliability of the shell can be evaluated. Compared with the traditional methods, the proposed method can evaluate the seismic performance of single-layer spherical reticulated shells from the perspective of randomness, which is much more reasonable. Besides, the tradeoff of efficiency and accuracy can be also ensured.

Abstract:In order to evaluate the size effect on the mechanical properties of mortar and to improve the size effect theory of mortar, size effect behaviours of mortar were investigated by using test method and theoretical analysis method. Based on the uniaxial compression test on 12 groups of mortar cube specimen and 12 groups of motar plate specimen, the size effect behaviour of mortar specimen and the relationship between mortar strength grade and size effect of compressive strength were investigated. The results indicate that the mortar compressive strength decreases with the increase of the specimen size, while the degree of size effect is enhanced with the increase of mortar strength grade. The energy release based size effect law was introduced to study the size effect of mortar geometrically similar specimen. The size effect of the mortar specimen of non-geometric similarity was also analyzed by correcting the Bazant size effect law with adding intensity term. Finally, the mortar size effect laws which can predict the size effect behavior of geometrically similar specimen, as well as the non-geometrically similar specimen，are derived，respectively. The predicted results of the proposed size effect law match well with test data. The research results provide an important basis for the establishment of the fine microscopic model of masonry, and also provide guidance for the engineering application of mortar.

Abstract:A new method combined with using single-point settlement gauges and strain gauges was developed to monitor the compression deformation of pile foundation，the compressions of pile shafts and soil layers beneath the pile bottom. The measurement depth of the new-developed method can reach more than 100 m below the ground surface，which effectively replenished the settlement monitoring technology of super-long pile foundations in the deep soft soil. The compression deformation behaviors were then systematically analyzed by field experimental and numerical methods. The main conclusions show that the vertical compression deformation of the pile foundation increaseds in a ladder shape during the construction of the bridge，and the post-construction settlement is approximate to 5.0 mm，which is less than the normative limit （20 mm） of a related design code； small deformation of the pile foundation cap may lead to differences in the settlements and axial forces of piles at different positions； then，the total compression deformations as well as the unit compression of the subsoil layers within 20~30 m below the pile bottom are quite small，hence it can be preliminarily determined that the influencing thickness of the compressible layers below the bottom of super-long pile foundations of high-speed railways in this tested area is approximate to 20 m； moreover，the accuracy of pile compression measured by settlement gauges is generally higher than that measured from strain gauges，and the pile compression can take a proportion as large as 30%~40% of the total pile settlement for a super-long pile foundation，hence it should be considered in calculating the pile foundation settlement； in addition，negative friction resistance appearis in the shallow depth，and there is a neutral plane at 11 m below the top of the pile； furthermore，the position of the neutral plane gradually moves up with the increase of the pile foundation loads.

Abstract:Based on the basic equations of linear elastodynamics, combined with the coordinate transformation and Buchwald potential function, the dynamic governing equations for a transversely isotropic multilayered pavement under moving loads are developed. The stiffness matrix for a single layer with a finite thickness and a half-plane are derived by using Fourier transform and its differential properties. Considering the interlayer conditions between layers, the global matrix are assembled with the analytical layer element of each layer. The solutions in the integral transform domain are obtained by combining with the boundary conditions. Then, the corresponding solution in the frequency domain is further recovered by applying inverse Fourier transform. The theoretical derivation of this paper is verified by comparing with the results of the existing literature. The change of interlayer conditions between layers is then simulated by changing parameters. The influence of the interlayer conditions between the surface layer and base layer on the dynamic response of the pavement structure can be calculated and analyzed. The calculation results show that the poor interlayer condition between the adjacent structure layers can cause the poor overall performance and durability of the pavement structure.

Abstract:Based on 3D modeling and PFC 5.0 platform FISH language，a method for constructing aggregate 3D discrete element model was developed. The aggregate particle geometry was constructed based on three-dimensional modeling and the aggregate geometry was imported into the PFC 5.0 platform to construct a clump template that can characterize the aggregate geometry. Then，clump template was called to generate clump in a certain space for aggregate discrete element simulation. In order to evaluate the effectiveness and accuracy of the method，the degree of filling was used to evaluate the effect of clump on the geometry of the aggregate and the number of unit spheres was used to quantify the impact of virtual aggregates on computational efficiency. The relationship between geometric shape accuracy and the efficiency of the filling algorithm was analyzed. In addition，the effect of fill algorithm parameters on fill level and number of unit spheres was explored. The results show that the number of geometrical feature points of aggregates is 1 000 ~ 2 000，which can take advantage of the filling algorithm. The clump block generated by the recommended parameters of the filling algorithm can better balance the filling precision and calculation efficiency. The method can realize the low-cost and high-efficiency generating three-dimensional discrete element model of aggregate，and provide powerful technical support for further digital test piece simulation.

Abstract:In order to optimize the location and quantity of viscous dampers on the large-span truss structure, the maximum value is obtained by summing the percentage of modal strain energy of replacement bars, and thus taken as the objective function. The peak values of node displacement, acceleration and element stress are regarded as the optimization control index. In addition, Matlab is adopted to verify an adaptive genetic algorithm optimization program. Based on the optimization result, the seismic control effect of the optimized truss structure under the frequent and rare seismic is compared through ANSYS analysis. The results show that the optimized scheme of damper has superior damping effect, which can obviously improve the stress situation of structure. Therefore, the best optimization scheme is obtained and the rules for optimal location of viscous dampers in large-span truss structures are summarized through taking safety and economy into account, which is of reference significance for the actual engineering damping design.

Abstract:There are divergent items in the free vibration solution of complex damping vibration equation. The structural free vibration responses cannot be calculated based on complex damping model, and the structural time domain calculation results are not stably convergent. On the basis of the complex damping model, the improved time domain motion equation can be obtained by time and frequency domain transformation. In the time step, it is assumed that the relationship of earthquake acceleration is linear. By the characteristics of the improved motion equation, the improved time domain calculation method under earthquake action is put forward. The cases show that， compared with the time domain motion equation of complex damping model, the improved time domain motion equation can be applied to the time domain calculation of structural free vibration responses. The structural time domain calculation results are stably convergent under earthquake action. Compared with the Fourier series method, the calculation amount of the proposed method is less and the computational efficiency of the proposed method is higher. With the increase of damping ratio, the difference between the improved time domain calculation method of complex damping model and the time domain calculation method of viscous damping model is increasing gradually. When the damping ratio is 0.5, the biggest relative error of structural acceleration peak values which are calculated by the two methods is over 20% under some seismic wave.

Abstract:In order to explore the correlation of the evaluation index between the conventional and rheological performance of bio-asphalt modified asphalt, rock asphalt modifier asphalt and its composite modified asphalt binder, the conventional and rheological properties of three kinds of modified asphalts were tested. The correlation analysis was conducted from the aspects of high temperature property, low temperature property, service temperature range and temperature susceptibility. The test results and analyses indicate that the correlation between the softening point and the equivalent softening point of the three kinds of modified asphalt is conspicuous, and the equivalent softening point has a significant linear correlation with the high continuous grading temperature. The linear correlativity between the bio-asphalt modified asphalt's equivalent breaking point and low continuous grading temperature of bio-asphalt modified asphalt is prominent, while the other two kinds of modified asphalts show complex parabola relation. It is necessary to evaluate the low temperature performance of asphalt comprehensively by combining these two indexes. The difference between the equivalent softening point and equivalent breaking point has a significant linear correlation with that between high continuous grading temperature minus and low continuous grading temperature, and the evaluation of service temperature range of asphalt is consistent. The correlation between penetration index and complex modulus index of three kinds of modified asphalts is noteworthy, and the evaluation of temperature susceptibility performance is consistent. The rheological performance can be estimated reasonably through the conventional performance index.

Abstract:Long-term stability assessment of slope characterized by the presence of red clays depends essentially on the creep model of red clay adopted. A specially designed device was used to conduct the tri-axial creep tests on red clay specimens. Deviatoric stresses were imposed on the specimens by stepwise loading，which were consolidated under varying confining stresses. The full-process creep curve of axial strains with increasing deviatoric stress was transformed equivalently to a cluster of creep curves under each stress levels by using "Chen's method". Furthermore，the ultimate deviatoric stress of red clay specimens before yielding in creep tests under varying confining stresses was determined using isochronal curve method，and used to establish the long-term shear strength criterion. A creep model of red clay in terms of axial strain accounting for the deviatoric stress and confining stress was established in the framework of ANFIS neural network. In this framework，a part of test data were used in training the creep model，while the remaining test data were used to examine its capability of predicting the creep response of red clay. A good agreement between the measurements and predictions validates the effectiveness and accuracy of this presented creep model.

Abstract:In order to figure out the effect of curing agent in sludge soil with the fly ash and lime as the main curing agent and TZ-01 as the additive, a series of experiments were conducted to study the strength characteristics of solidified soil and the influencing factors on the strength of solidified soil. Through experiments, the initial water content, organic matter content, main curing agent content, additive incorporation ratio, and age of solidified soil were analyzed. The results showed that the initial water content of the sludge soil hindered the growth of the solidified soil. The main curing agent and age growth can effectively enhance the strength of the solidified soil, and there was an optimum blending ratio of organic matter content and additive incorporation ratio. Based on the analysis of the stress-strain curve obtained from the unconstrained compression test of solidified soil, four stages of solidified soil under uniaxial compression were proposed. By processing and analyzing data, the water-cement ratio β was introduced, the effects of organic matter content, additive incorporation ratio and age were comprehensively considered, and the solidified soil strength prediction model was established.

Abstract:Large area of special high liquid limit clay was formed due to the depositing in the downstream of Yellow River at Shandong province. Without the use of such clay in those plain areas in lack of filling materials, great resource waste would be caused. This paper experimentally examined the soil strength and modulus in both construction and operation periods. The high liquid limit clay in Yellow River flood area consisted of higher rounded silt particle and clay particle, which presented low volume ratio of air and high saturation degree when compacted above the optimum moisture content. Based on the filter paper tests, it was indicated that high air intake value resulted in strong water retention capacity. Through the unventilated-undrained triaxial test, the relationships between the normalized static strength, shear strength and saturation degree/volume ration of air were obtained at different compaction states. It was found that the soil had an optimum saturation ratio at 79%（volume ratio of air=8%）. The soil resilient modulus was more sensitive to the moisture contents. Although the subgrade remained safe when moisture contents increased from 20% to 23%，the compression strain increased by almost 200% due to the sharp decrease in the resilient modulus. Considering the subgrade compaction standard specified in China and Japan, the high liquid limit clay in Yellow River flood area should be compacted lower than 23% moisture content and 8% volume ratio of air，i.e.，no less than 90% compaction degree，to ensure the long-term stability of soil strength and modulus.

Abstract:The surrounding electromagnetic fields will be changed greatly when the track of medium and low speed maglev is electrified. The generated effect of strong electromagnetic field has a great impact on the safety of the pushing and falling of the steel box girder over the maglev track.Therefore，taking the construction of Changsha Huanghua International Airport Avenue Project as a practical case，the impact of electromagnetic field on the pushing and falling of the steel box girder over the maglev track is studied.The large finite element analysis software ANSOFT is used to perform finite element analysis and numerical calculation on the strong electromagnetic field of the maglev track.It is assumed that the current of the maglev track remains constant during the advancement of the steel box girder. By changing the position of the steel box girder relative to the track，the impact of the strong electromagnetic field generated by the maglev track on the launching and falling of the steel box girder under the different working conditions is studied. After performing the static analysis and calculation for each working condition，the corresponding construction safety scope is obtained. The conclusion of the study provides references and suggestions for similar projects in the future.

Abstract:In order to satisfy the increasingly significant demand of the digital city for the detailed 3D model and solve the low efficiency problem of traditional modeling method, this paper summarizes a method of building the urban detailed model based on unmanned aerial vehicle (UAV) image sequences. Through the in-situ aerial photography test with 25 sorties, detailed models for 20 experiment area (300 m×300 m) and a library building were built. The accuracy of all detailed models were evaluated by field check points. The effect of 5 different flight heights and 4 different control points on the accuracy of the detailed models were discussed. The results show that the errors of the detailed models can be effectively decreased and the accuracy is improved by declining the flight height or increasing the number of control point. The highest accuracy of detailed models is ±3.4 cm in the plane and ±3.1 cm in the height, respectively. The accuracy of the detailed model for the library building is ±3.4 cm and ±1.5 cm, respectively. The method of building the urban detailed model using UAV image sequences can satisfy the accuracy requirement of the urban real scene model, which has great practical values in practical engineering.

Abstract:The traditional probability distribution selection method is based on the observation data and plotted on the probability paper of a hypothetical distribution, which cannot conduct the direct comparison analysis due to the limitation of the probability paper. In this paper, a new generalized unified probability plot (GUPP) method is proposed. Through the Rosenblatt transform, the hypothesis distribution is transformed into a unified probability paper for visual comparison, and an efficient test method and comparison parameters are proposed based on GUPP which can be used for quick fitting and testing of large data volumes and large-scale hypothetical probability distributions. In this research, the proposed method is also used to statistically analyze and fit the real-time wind speed data collected in Xiamen from 1953 to 2015. The results show that the Pearson-Ⅲ distribution is better for annual average maximum 10-minute wind speed in Xiamen and for determining the maximum wind speed for structural design in Xiamen from different regression periods.