Abstract:According to the characteristics of a novel continuous UHPC box-girder bridge and the layout of its prestressing system, the anchor block for external tendons on the web was studied. Firstly, the effect of the plate thickness on the “local bending effect” in anchorage zone was evaluated through the analysis of stress in the isolated rectangular anchor block. A simplified plane linkage model was proposed through the topology optimization in order to study the force transfer mechanism in anchorage zone. Moreover, two kinds of methods were developed to strengthen the anchorage zone based on the simplified model. On the basis of the above research procedure, six different anchoring schemes of the anchor block for the external tendons were designed. After analyzing and comparing the performance of the different anchoring schemes, the effects of diaphragms, steering of prestressing tendons, and anchoring length of the anchor block on the mechanical behavior of the anchorage zone were evaluated. Finally, a type of reasonable anchor block of the external tendons was obtained.

Abstract:To reduce long-term and excessive mid-span deflections of long-span PC rigid frame bridges, a method of adding precast RPC (reactive powder concrete) columns into the bottom plate of the negative moment region and the mid-span roof of the rigid frame bridge to form RPC-NC (Normal Concrete) composite section was proposed. The RPC-NC composite column was analyzed to investigate the influence of RPC on reducing creep and shrinkage effects of the composite column and the stress redistribution between RPC and NC as well as the mechanical capability of shear bond. Based on the above research, design scheme of prefabricated RPC column used in actual bridge was put forward, and then the influence of the precast RPC column on the whole bridge stress and the mid-span deflection was analyzed by finite element method. The results demonstrate that the added precast RPC obviously reduces the rotation of the negative moment region and the compression stress of NC near RPC, which decreases the long-term mid-span deflection after the construction of the rigid frame bridge by 53.9%.

Abstract:Based on a generalized cable-girder model, it was found that the torsional stiffness degradation of the cable system was the essential reason leading to aerostatic torsional divergence of long-span suspension bridges. The effects of the deformations of the main cables and the bridge tower on the stiffness degradation of suspension bridges were investigated. Theoretical analysis indicates that vertical deformation of the main cable is critical to the torsional stiffness of the whole system. Provided that the vertical deformation of any cable reaches a critical value, the cable will loosen up to a non-stress state, which causes a sudden drop in torsional stiffness of the system. Therefore, it is stated that the sudden drop in stiffness due to the vertical deformation could be the key reason for the aerostatic torsional divergence of a long-span suspension bridge. Moreover, the study also shows that lateral deformation of the main cable and the horizontal relative deformation between the two tower-tops postpone the stiffness degradation, and hence enhance the critical vertical deflection. In addition, it is shown that the effect of turbulence on torsional divergence is non-negligible, and the turbulence significantly decreases the aerostatic torsional stability of bridge structures. Numerical results of the Xihoumen Suspension bridge performed by nonlinear finite element simulation could be explained tentatively by the theoretical viewpoints proposed in this paper.

Abstract:Building structures are randomly distributed along the hillside, thus the detailed distribution of the topographic factor along hillside is of great importance to the wind load prediction of building structures in hilly terrain. To investigate the detailed distribution of the topographic factor along the hillside, wind tunnel tests were conducted on two hill models with different slopes, both of which were scaled to 1∶300 with a cosine section. The detailed distribution of the topography factor along the upwind slope, downwind slope, and side slope was obtained. Numerical models, which were verified by the wind tunnel testing results, were built to investigate the detailed distribution of the topographic factor of the hills with different heights (H=90~500 m), slopes (tan α=0.13~0.5), and shapes (Cosine shape, Gaussian shape, Parabolic shape).Furthermore, it was employed to deduce the calculation formula of the topographic factor, which were also compared with several national codes. Research results show that, based on the topographic factor at the hill foot and the hill top, a particular topographic factor at optional position can be obtained more safely, reasonably and simply by using vertical linear interpolation depending on the height of the calculated point rather than the horizontal linear interpolation. It was found that the topographic factor of the side slope was the control one in the prediction of the topographic factors, where the topographic factor at the foot of the side slope was respectively 61.89% and 94.09% greater than that of the upwind slope and the downwind slope, respectively, and the value reached up to 1.2.

Abstract:In order to investigate the static wind forces on the multi-bundled conductors, based on the wind tunnel force balance tests for rigid sectional models of single and multi-bundled conductors, drag coefficients and the influence of Reynolds number effects and shielding effects were analyzed. The results illustrate that the drag coefficients obtained by the wind tunnel tests are much smaller than those specified in the Code. And because of the surface roughness of the conductors as well as the flow turbulence, the range of Reynolds numbers in the critical region was brought forward. Moreover, although the Reynolds numbers are within the subcritical range, the drag coefficients are still very sensitive to the variance of the Reynolds numbers. For the multi-bundled conductors, the interference caused by the upstream lines reduces the integrated drag coefficients. It is stated that the influences of the shielding effects should be considered. Finally, an empirical formula involving the Reynolds number effects and shielding effects was proposed to calculate the drag coefficients of the bundled conductors, which provides references for calculating the static wind loads of conductors.

Abstract:For the single-layer intersected inverted catenary cylindrical reticulated shell, the static properties and stability of the structures with different types of grid were studied and compared, and then the optimal grid form was obtained. The static properties and stability of the single layer intersected inverted catenary cylindrical reticulated shell were compared with those of the intersected circular cylindrical reticulated shell. Moreover, the stability of the former was studied comprehensively, including the buckling modes and the effect of various parameters such as the member sectional area, initial geometric imperfection, asymmetric load distribution, and support conditions on the ultimate load-carrying capacity. The results show that the structural performance of the single-layer intersected inverted catenary cylindrical reticulated shell with triangular grids is markedly superior to the circular one. Because, this kind of reticulated shell is sensitive to initial geometric imperfection, 1/300 of the structural span should be considered as the initial geometric imperfection value in the calculation of the ultimate load-carrying capacity. Additionally, the reticulated shell is also quite sensitive to the asymmetric load distribution, and the optimal value of rise-span ratio is 0.50 for shell stability.

Abstract:Since the long-span steel structure is prone to perform nonlinearity such as yielding rigid body motion under construction loading, construction process analysis was conducted by the Vector Form Intrinsic Finite Element method (VFIFE). Based on the basic theory of the VFIFE, the tensioning cable element was introduced to simulate the tensioning process by adjusting the length of the cable element. In addition, the jack element was used for the unloading analysis of the long-span steel structure. Moreover, the VFIFE based program was developed by the MATLAB, and compared with the conventional method by means of three FE models such as the assembly of cantilever beam, the tension forming of cable truss, and the tensioning construction of long-span truss string structure. To this end, the VFIFE theory and program were verified and validated. The result showed that the assembly, tension forming, and unloading of the long-span steel structures could be reasonably simulated by the VFIFE.

Abstract:In order to investigate the overall stability of I-shaped stainless steel member under axial compression load, the nonlinear finite element analysis of the stainless steel members subjected to axial compression load was performed by ANSYS software. By comparing the numerical results with the experimental results, the accuracy of the finite element model was verified. The effects of initial geometric imperfections, section residual stress, material mechanical properties, and section width-thickness ratio and slenderness ratio on the overall stability of the members were parametrically analyzed by means of the validated finite element analysis. According to the comparison, it can be seen that the material mechanical properties and slenderness ratio of the members are the key influential factors. Based on the parameter analysis, a new three-segment formula for calculating the overall stability coefficient was proposed by data fitting. The proposed three-segment formula can accurately predict the overall stability bearing capacity for I-shaped stainless steel member under axial compression load.

Abstract:Through deriving the amplification formula of effective inter-storey displacement for triangle form steel outriggers, the formula of additional modal damping ratio for the high-rise building with damped rigid outriggers were presented. Taking the frame-core-tube structure as an example, the frame-core-tube structures with damped rigid outriggers, diagonal-brace damping layers, and strengthened storeys, respectively, under the action of pulse-like earthquake waves and non pulse-like earthquake waves were analyzed and compared. The computing results show that the structure with damped rigid outriggers exhibits the best seismic performance in the above three frame-core-tube structures, and the pulse-like earthquake waves make a great enhance on seismic performance of the high-rise buildings. Meanwhile, seismic performance of the structure with damped rigid outriggers is in proportion to the distance of shear wall to outside frame column, but inversely proportional to storey height, and related to the angle of viscous damper.

Abstract:Although the size of specimens presents significant effect on the mechanical performance of CFRP confined concrete columns, the size effect is a blank area of study until now. Based on a series of tests on seven groups of Carbon Fibre Reinforced Plastics (CFRP) confined large-scale square concrete columns with different corner radius, the basic mechanical properties were obtained, such as the failure modes, compressive strengths, stress-strain relationships, and the ultimate strain distribution of CFRP jacket. Moreover, their comparison with the experimental results of the smaller-scale specimens has been investigated and published. It is demonstrated that the confined strength increases with the increase of the corner radius except for the specimens with sharp corner. All of the specimens fail due to CFRP rupture, and the fracture location occurs in the chamfer zone. Meanwhile, the phenomenon of the stress concentration is obvious. The confinement ratio, i.e., MCR, shows a certain correlation with the size of specimen on the compressive strength of CFRP confined specimens. The ultimate strains measured on the CFRP jackets are about 35% less than that tested by the coupon specimens, while it is more serious than that for the smaller-scale specimens. It is found that the discrepancies between the predicted results of the existing strength models of CFRP confined square column and the experimental results in this work are obvious. It suggests that the size effect on the FRP confined square columns cannot be ignored,which needs to be further researched.

Abstract:Steel plate-masonry composite(SPMC) construction is a new method for the renovation of existing masonry walled buildings. To understand the shear behavior of the SPMC beam, six composite specimens were tested. The tests took into account the influence of the bolt spacing and the thickness of the steel plate. The shear failure mechanism was also examined.The test results show that the steel-plate and masonry collaborated well, and the damage sequence of both was not obvious. The damage of the composite beams always initiated from the local buckling of the steel plate in the shear-span section. The increase of the thickness of the steel plate significantly improved the critical buckling stress of steel plate and the ductility of the composite beams. Moreover, rather than the bolt-spacing, position arrangement of the bolts in the shear-span section remarkably affected the bearing capacity. Eventually, a design equation was given to calculate the shear capacity of such composite beams.

Abstract:In this work, carbon fiber reinforced plastic(CFRP) were fabricated using vacuum assisted resin infusion (VARI). Specimens were tested under four strain rates (25, 50, 100 and 200 s-1) and six temperatures (-25, 0, 25, 50, 75 and 100 ℃) by means of a servo-hydraulic high rate testing system. The results show that tensile strength and toughness increase with the increasing strain rate under the same temperature (room temperature 25 ℃) except the toughness under 200 s-1. At the same strain rate of 25 s-1, on the other hand, the tensile strength and toughness at the room temperature are higher than those under other temperatures. The failure patterns of CFRPs were nearly similar under four investigated strain rates, but different under six temperatures. Moreover, Weibull analysis was carried out to quantify the change of tensile strength under different conditions.

Abstract:The impermeability experiments were conducted by adopting a HS-4 concrete permeability instrument and the permeability labeling method on the concrete block covered with composite mortar mixed without additives and with new additive respectively, with emphasis on the thickness of the added mortar and incorporation of additives. The obtained permeability grades of all specimens were then investigated. The results showed that the concrete impermeability was improved effectively by applying high performance composite mortar with 20 mm thickness and 18 % additive content on the concrete surface. Furthermore， the reinforced mesh thin layer of high performance composite mortar reinforced the concrete structure effectively.

Abstract:Based on high-precision nonlinear finite element analysis, the multi-factor combined effects on reinforced concrete were considered, including concrete carbonation, reinforcement corrosion, and bond-slip performance degradation. And a refined finite element model was established to investigate the influence of durability deterioration on the seismic performance of reinforced concrete members in common atmosphere environment from corrosion rate of reinforcement and carbonation rate of concrete. It is revealed that ,when the service life was less than 30 years, the seismic performance of reinforced concrete members was changed little, while after 30 years, it degraded significantly. On the other hand, when the service life reached 100 years, concrete bearing capacity decreased to 22.5 %, stiffness decreased to 33.5 %, ductility decreased to 36.7 % and energy dissipation decreased to 40.5 %. To this end, it suggests that the influence of the service life and durability deterioration on seismic performance of the reinforced concrete members in common atmosphere environment should be considered in seismic design to guarantee the earthquake-resisting capacity of the structures.

Abstract:To study the influence of the interfacial transverse slip between concrete and the steel plates of bolted side-plated (BSP) RC beams on the structural performance, a simplified piecewise linear model for estimating the transverse slip and transverse shear transfer was proposed in analogy of the transverse shear transfer with the Winkler's model of elastic foundation, combined with previous experimental numerical studies. Thus, the functional calculation method for transverse slip and transverse shear transfer was obtained from the flexural stiffness of the RC beam and steel plates, and the shear stiffness of the bolt connection. The simplified theoretical model was also validated by test results, and it can be used for strengthening design of BSP beams.

Abstract:To find out a more effective strengthening method for timber column with decay root, CFRP (Carbon Fibre Reinforced Plastic) sheet was employed to replace iron band in coating reinforcement technique. Six specimens were manufactured built, some of which had decay roots and strengthened by CFRP sheets using coating technique. Axial compression experiments were carried out to investigate the response of these six columns. The load-displacement relationships, load-strain relationships, ultimate compressive strength and ductility of the specimens were obtained to evaluate the strengthening effects. The influence of layer numbers of CFRP sheets was also discussed. The results showed that the ultimate compression strength and ductility of the strengthened columns were recovered to about 81.4% to 92.4% and 87.3% to 95.8% of those of the intact column, respectively. The peak compressive strain of the strengthened columns was also improved in both horizontal and vertical directions. The column strengthened by 3 layers of CFRP sheets exhibited better compressive performances than those of other strengthened columns, but still lower than that of the intact one.

Abstract:On the basis of previous researches and engineering practice，total 52 cubic and 33 prismatic phosphogypsum specimens were made by a water/cement ratio of 0.43, where nine mix proportions for phosphogypsum were involved according to the different mixture of phosphorous slag micro-powder, hydrated lime, cement, water reducer and retarder. Furthermore, total 8 one-second scale wall models using the 7th mix proportion were also made for axial compression tests.Experimental results combined with the earlier research show that the compressive strength of cast-in-situ phosphogypsum wall is about 0.68 times the prism compressive strength, while the latter is about 0.8 times cube compressive strength. Additionally, the recommended value of material weight is around 14.0 kN/m3 to 15.0 kN/m3. Based on the reliability analysis of engineering examples, the material partial coefficient of cast-in-situ phosphogypsum is recommended as 1.9, and the standard value and design value of phosphogypsum compressive strength are given according to the mix proportion examined in this paper.

Abstract:Based on the relationships of the differential settlement of piles and soil, soil arch effect and load distribution, an assumption that the volume of pile into the embankment is equal to the compression amount of the soil arch volume was firstly put forward. Combined with the mechanical analysis of pile-supported embankment and the deformation equilibrium of piles and soil, the formula between the pile-soil stress ratio and the soil arch height with differential settlement was derived. Finally, comparative model test and numerical analysis were performed to check the validity of this method. The proposed method was also used for a parametric study in order to investigate the effects of various parameters such as replacement ratio of pile and soli area, embankment height, and friction angle of the soil on the behavior of the pile-soil stress ratio and soil arch height. The result turned to be in good agreement with the measured values, which verifies the rationality of the proposed method.

Abstract:In order to further study the deformation and intensity characteristics of soil-rock aggregate mixture, a series of triaxial tests were conducted by using a YS30-3 large-scale triaxial test machine based on the orthogonal design. These tests took into account various factors such as water content, stone content, rock and soil property, etc. The test results indicate that the soil-rock aggregate mixture under the triaxial stress conditions does not exhibit obvious characteristics of strain softening. The cohesion of soil-rock aggregate mixture is generally low and the internal friction angle is relatively high, while the internal friction angle is more susceptible to the influencing factors. Moreover, it is found that the rock content significantly influences on the strength of soil-rock aggregate mixture. As the rock content increases from 25% to 70%, the internal friction angle increases linearly from 34.54° to 46.39°. The effects of rock content and confining pressure are the internal and external causes on the volumetric strain characteristics of the soil-rock aggregate mixture, respectively. That is to say, with the same water content as well as rock and soil property, the lower the rock content, the more obvious the shear contraction of soil-rock aggregate mixture under the higher confining pressure. Meanwhile, the higher the rock content， the more obvious the shear dilatation of soil-rock aggregate mixture under the low confining pressure.

Abstract:It is known that axial compressive deformation is usually generated in a stone column under vertical loads, and often accompanied by a radial expansion against the surrounding soil near the top portion of the column. With the consideration of this deformation characteristic of the stone column, a new technique to measure the lateral bulging of the stone column was proposed, where the lateral bulging of the column was determined by circumferential measurements. The variability and accuracy of the proposed measuring technique was fully verified by the comparison with the other measuring methods. Moreover, this measuring technique was employed to study the deformation behavior of stone columns in an indoor laboratory test. The measuring results show that the lateral bulging of the stone column increases with the increase of vertical loads. Furthermore, under a certain load, the column bulging increases along with the column length firstly, then decreases with the column length after the maximum bulging.

Abstract:Combined with the stress characteristics of the bridge deep-water pile foundation during the operation period, this paper studied the general principles of the mixed model for pile axial force in deep-water pile foundation. The mixed model was firstly presented during the operation period based on the monitoring data of pile group foundation considering the influence of multiple environment factors. The mixed model of Sutong bridge pile group foundation was built by using the finite element simulation and PSO-SVM statistical method. In order to facilitate comparison, the Radial Basis Function (RBF) artificial neural network model was built, whose results were compared with the prediction results of the mixed model. The results showed that the mixed model had higher prediction accuracy and more robust predictive ability for the three piles under different loading conditions, and it exhibited better generalization ability. The mixed model could be applied to the prediction of the axial force in the deep-water pile group foundation during the operation period.