Abstract:The three-dimensional finite element model of a 50-storey steel frame-concrete core wall structure was established. The along-wind induced vibration analysis of the structure with/without damping outrigger storeys under the simulating wind load was performed, and the influence of the number and location of the damping outrigger storey on wind resistance performance of the 50-storey steel frame-concrete core wall structure was discussed. The analysis results show that the rational number and optimal arrangement of the damping outrigger storey can effectively improve the comfort level and wind resistance performance of the tall steel frame-concrete core wall structure. If the maximum inter-storey displacement angle or the peak roof displacement is taken as control objectives, damping outrigger storeys should be installed near the central structure so as to obtain better vibration reduction effect. If the peak roof acceleration is taken as control objectives, damping outrigger storeys should be installed near the top of the structure so as to obtain better vibration reduction effect. Assuming that the total damping coefficients and other parameters of single viscous damper are unchanged, wind resistance performance of high-rise buildings with different damping layers are compared, and the results indicate that the total performance of the buildings with multiple damping layers is better．

Abstract:When structural seismic analysis is conducted on high-rise buildings, the impact of the infill wall stiffness on the structure response is usually considered by the fundamental period reduction factor in the PKRM software. In this paper, eight high-rise buildings in the Laibin High-Rise Testing Project were examined. These buildings were tested for ambient vibration and seismic analysis, which were also modeled and calibrated by the Finite Element (FE) Sap2000 software. First, eight FE models for the eight buildings were built in Sap2000. The same modeling for infilled wall using PKPM was also calculated, and the comparison of these two calculation results demonstrates the comparability of these two models. Next, shell model and diagonal strut model were adopted in the modeling of infill wall, and the models were calibrated by using the data from test. Thereafter, Sap2000 model was used for seismic response analysis instead of PKPM model. Finally, the seismic response spectrum analysis in linear elastic status was conducted under small earthquake. The comparison of the calculation results from PKPM software shows that, compared with the calculated value of calibrated model, the unreduced floor shear force calculated by PKPM is half of that by Sap2000, and the inter story displacement and inter story drift calculated by PKPM is three to four times of that by Sap2000. Moreover, the value of fundamental period reduction factor suggested by Technical Specification for Concrete Structures of Tall Building (JGJ3-2010) is 0.7~1.0, which is more conservative to the results obtained from the analysis.

Abstract:For the convenience of engineering design on T-shaped, L-shaped, and cross-shaped concrete filled steel tubular (CFST) columns, a unified algorithm for eccentric-loaded capacity of special-shaped CFST columns was developed through an analysis of calculation methods in the typical specifications. The N-M relationship curves of columns were calculated and analyzed by using a self-complied numerical analysis method. The validity of the algorithm was then verified by experimental results in other literatures for various cross-section forms of special-shaped CFST columns. The results show that the uniform algorithm has clear mechanical meaning and it is easy to operate. The mean ratio of the test result to prediction of load bearing capacity is 1.1~1.4, with a certain safety reservation, but the prediction accuracy depends on the engineering axis direction of loading cross-section. The proposed unified algorithm improves the computational theories for special-shaped CFST columns, which can promote its developments and applications in the practical engineering.

Abstract:In order to achieve the goal of green building, the idea of steel-jacket retrofitted RC columns with recycled aggregate concrete was proposed. Tests of 1 original column, 3 retrofitted columns under axial compressive loading and 8 retrofitted columns under eccentric loading were conducted. It is found that after retrofitted by steel-jacket and recycled aggregate concrete, the bearing capacity and deformation performance of the RC column are significantly improved, where the relative bearing capacity is increased by 1.12 times on the average. The effect of recycled coarse aggregate replacement ratio on eccentric bearing capacity is not obvious, while the mid-span strain of steel-jacket increases slightly when the replacement ratio grows under large eccentricity. The peak loads of the retrofitted column with preload appear earlier, which shows a negative effect on deformation performance. Besides, the influence of the eccentricity is similar to that of the concrete-filled steel tubular column: as the eccentricity increases, the bearing capacity decreases and the compression-side strain of steel-jacket increases, and this trend becomes stronger when the replacement ratio increases. Finally, according to the comparison of design codes and the researches, eccentric bearing capacity calculated by EC4 is most consistent with the test results for this kind of retrofitted columns.

Abstract:This paper proposed a new mix design method of ultra-high performance concrete (UHPC) based on the maximum particle packing density, and the modified Andreasen & Andersen particle packing model was used to calculate the quartz sand grading. Density test and single variable trial-mixing test were employed to design the remain parameters of the concrete mixture, and one group of mix proportion with better strength and fluidity was selected based on the test results. Then, the compressive and uniaxial tensile tests were performed to study the compressive strength and the influence of fiber volume content on the tensile characteristic of UHPC. The test results show that: the compressive strength of UHPC is between 116.64 MPa and 134.85 MPa, tensile strength is between 4.761 MPa and 8.504 MPa, and the tensile strength and toughness increase greatly with the increase of fiber volume content. Additionally, the brittleness failure mode transfers into ductile failure. The results of this paper provide a reference for the application of this kind of materials.

Abstract:Due to the problems of large amount of cementitious material and high cost of Ultra High Performance Concrete (UHPC), the UHPC system was mixed with coarse aggregate and river sand instead of quartz sand, and the preparation of UHPC with coarse aggregate is successful resulting in excellent mechanical properties. Meanwhile, the effects of the coarse aggregate content and geometric parameters of the steel fiber on the mechanical properties of the UHPC with coarse aggregate were studied. The results showed that, with the increase of coarse aggregate content (0~800 kg/m3), the compressive strength of UHPC increased firstly and then decreased, the elastic modulus increased almost linearly. When the content of coarse aggregate was in 0~400 kg/m3, the flexural strength and initial crack strength of UHPC changed little, while when the content of coarse aggregate was 400~800 kg/m3, the flexural strength and initial crack strength of UHPC decreased obviously. With the increase of the content of coarse aggregate (0~800 kg/m3), the flexural load-deflection curve of UHPC was obviously changed, and the flexural toughness decreased obviously, but a strain- hardening process was observed. With the increase of the length of steel fiber, the compressive strength, flexural strength and flexural toughness of UHPC increased, but the static compression modulus and initial crack strength of UHPC changed little.

Abstract:The radial stress-strain relationship of wood under monotonic and repeated compressive load was studied, according to the tests on the clear wood specimens under monotonic and repeated compressive load. The results show that the monotonic compressive stress-strain curve and the skeleton curve of repeated compressive stress-strain curve are well coincident when the strain is less than 0.16. When the strain is over 0.16, the difference between these two is gradually increased, but they can still be described by the same mathematical model. In the cyclical process, the reloading path and unloading path are expressed by linear and double fold line models, respectively. Based on the comprehensive consideration of the typical characteristics of unidirectional compression and repeated loading and unloading, the stress-strain model of wood under repeated compressive load was established. Based on the established model, a MATLAB program was then written into the MATLAB software. Good consistency was found between the predictions of the model and the test results.

Abstract:This paper verified the effectiveness of nonlinear finite element model according to the tested displacement of double loop line tower for UHV transmission line which was under the most unfavorable load combination. Then, the implicit nonlinear dynamic analysis was carried out on the strain section of transmission line system in the most unfavorable position. Through examining the dynamic effect of transmission tower when 1 to 4 wires were cut off, it can be confirmed that the breaking of all four wires and the breaking of the uppermost wire has the greatest influence on the dynamic effect of the transmission tower in the broken area. The influence of the lateral stiffness, span, line angle and elevation on the suspension points in broken area under the dynamic effect of the transmission tower was analyzed at the same time. The results show that the increase rate of the dynamic effect of the line tower in the broken area increases gradually with the decrease of K (the relative lateral stiffness) when the stiffness of the line tower in the unbroken area is smaller than that of the broken area (K<1). However, in the case of K>1, the increase rate of the dynamic effect of the line tower in the broken area decreases gradually with the increase of K. Further, the dynamic effect of the transmission line tower on the disconnected side increases significantly in a geometrical relationship when the span distance extends to the unbroken area, but the extension of the span distance is linearly and positively correlated with the dynamic effect of the break-line transmission tower. When the turn angle of line or the elevation angle of suspension points is ±5° or ±7°, the maximum dynamic displacement value and the maximum displacement value in the stability of the broke-line transmission tower both exceed 1.822 m.

Abstract:Taking the guyed portal tower of a 220 kV transmission line as the background, comparative studies on the response characteristics of the guyed portal tower under a downburst and the conventional terrain B wind field were carried out by the time history response analysis. 3-D finite element model of guyed portal tower-transmission line system was established, and the dynamic characteristics analysis was performed. The static force coefficients of the rigid guyed portal tower model and double-split conductor model were obtained by wind tunnel tests. Based on the numerically simulated fluctuating wind load induced by the downburst field and Chinese code defined terrain B wind field, the responses of the guyed portal tower under the fluctuating wind loads were analyzed through the Newmark-β method, which was compared with the results based on the codes defined equivalent static loads. The results show that the peak compressive stress of the tower elements and the maximum tensile stress of the guy wires induced by the downburst are 600 MPa and 1 300 MPa, which are 4.6 times and 2.5 times to the corresponding values induced by conventional terrain B wind field, respectively. In addition, low frequency response components induced by transmission lines play an important role in the whole displacement response of the tower. The wind loads on the transmission lines have great effect on displacement responses, but show little effect on the acceleration responses. Furthermore, comparative study indicates that Chinese code lack the items of the downburst induced wind loads, but the defined loads are appropriate to design the transmission tower under the conventional terrain B wind field, while the downburst loads defined by ASCE guideline may underestimate the destructive effect on the guyed portal tower.

Abstract:In order to investigate the bonding performance of Kevlar fabric layers and that between Kevlar fabric and steel plate, an MTS universal testing machine was used to test the mechanical properties of double-layer Kevlar 49 fabric and Kevlar 49 fabric/steel single-lap shear joints. The results show that the effective bond length of double-layer Kevlar 49 fabric single-lap shear joint specimens is 25 mm, and that of Kevlar 49 fabric/steel single-lap shear joint specimens is 50 mm. Within the effective bond length, bond forces of two types of single-lap shear joints increase with the increasing bond length, while the increasing amplitude decreases. The bond force reaches the maximum when the specimens have the effective bond length. However, the bond stresses reduce with increasing bond lengths. The experimental results obtained in this study will provide valid data for determining reasonable bond length of Kevlar fabric used for structural reinforcement in civil engineering.

Abstract:MHB rubblization technology is widely used in the reconstruction of the old cement concrete pavement (PCC) crushing, however, the impact of vibration on the adjacent buildings and residents during the impact crushing process needs to be urgently resolved. The attenuation law of physical parameters of the pavement panel under impact load were deduced and analyzed based on elastic theory and wave theory. Relying on the field vibration monitoring test on the old PCC pavement reconstruction project of Shandong provincial highway S245, and combing with ANSYS/LS-DYNA dynamic finite element numerical simulation, the three-dimensional dynamic response under different influence factors was studied. Then, the level safety distance of rubblization adjacent buildings and the comfortability critical distance of the residents were explored. The results show that MHB rubblization belongs to impact type vibration source, whose vibration is a negative exponential curve in the form of a sharp attenuation, and the results of calculation, measurement and numerical simulation are in agreement with the attenuation trend of the curve. With increasing stroke the peak time load continuously advances. The peak vibration velocity of 1cm/s can be used as a control index for judging the safety of adjacent building. When the hammer drop height is 0.8 m, 1.0 m, 1.2 m respectively, the level safety distance of adjacent building is 14 m, 18 m, 20 m respectively, and the comfortability critical distance of inhabitants is 24 m, 29 m, 31 m respectively.

Abstract:Diseases detection and maintenance of tunnel lining is an important link to ensure the safety of tunnel in operation. Based on the images captured by CCD linear array camera in Movable Tunnel Inspection System, a new method was proposed. It is inspired by cutting-edge computer science-deep learning and different from the traditional ones entirely. The main idea is as follows: a) extracting lining diseases and establishing feature map database; b) building deep learning framework; c) training samples with convolutional neural network; and d) establishing a classification system of gray scale feature maps of tunnel lining. Aiming at CNN model GoogLeNet, inception module and overall architecture were improved by using improved convolutional kernels. The best test-set accuracy is over 95%. At the same time, the influence of different deep learning frameworks (Caffe and Torch) and image contrast enhancement method (such as histogram equalization, HE) were tested with examples. The results show that the deep learning method is applicable to the tunnel lining diseases detection. The advantages are high accuracy, high speed, good extensibility and very robust in complex cases.

Abstract:To study the fatigue properties of HRB500 reinforcing bar in longitudinal connected slab track on bridge, fatigue tests under symmetric axial alternating tension-compression cyclic loads for standard specimens of HRB500 reinforcing bar were conducted, and then the fatigue life and its cumulative failure probability of standard HRB500 reinforcing bar at different stress levels were obtained. On this basis, the correlation coefficient p and Theil's inequality coefficient u were used as indexes of estimation accuracy to evaluate three methods which are widely used to estimate parameters of three-parameter Weibull distribution. And the grey prediction method, whose prediction accuracy is the highest among the three methods, was used to estimate the parameters of three-parameter Weibull distribution for the fatigue life of standard HRB500 reinforcing bar, and the distribution functions for the fatigue life of HRB500 reinforcing bar at different stress levels were obtained. Ultimately, the probabilistic S-N curve of HRB500 reinforcing bar in the longitudinal connected slab track on bridge with reliable index of 4.2 based on Kohout-Vêchet equation in the full stress range was established. The research can provide experimental basis for the establishment of fatigue life prediction model of HRB500 reinforcing bar in the longitudinal connected slab track on bridge under combined loads during service life.

Abstract:In order to study the influence factors on the pinned-pinned resonance of ballastless track rail, in this paper, based on the vibration calculation theory of periodically supported beam, the influence parameters of ballastless track on the pinned-pinned resonance of rail were analyzed by using the solid vibration analysis model established by FEM, and the sensitivity coefficients of those parameters were calculated through the single-dimensional sensitivity analysis method. The results show that the pinned-pinned resonance of rail is sensitive to the fastener span as the resonance frequencies vary remarkably with the increase of fastener span. Rail mass is a slightly sensitive parameter to the pinned-pinned frequency of rail, although its sensitivity coefficient is smaller than that of fastener span. The stiffness, damping of fastener and elastic modulus of track slab are all classified as insensitive parameters since they have little influence on the pinned-pinned frequency of rail. The constrained damper attached to the non-working surface of rail can reduce the vibration amplitude of the pinned-pinned resonance effectively, but hardly change the resonance frequencies. With the influence of fastener span, the pinned-pinned frequency of rail on ballastless track is lower than that on ballasted track.

Abstract:To determine the index weights of the condition assessment model for suspension bridges, group Analytic Hierarchy Process (AHP) approach was explored to determine the corresponding index weights. Firstly, the 10〖SX(〗0〖〗8.384〖SX)〗～10〖SX(〗8〖〗8.384〖SX)〗 scale method was adopted based on the Weber-Fechner law. Then, the genetic algorithm was used to optimize the consensus of judgment matrixes. The consensus of judgment matrixes was significantly improved after optimization. Moreover, the PSO-K-MEANS clustering algorithm was used to classify the experts' opinions, and the expert weights were calculated by the peer-to-peer consensus reaching model. In the end, the presented group-AHP method was applied to a suspension bridge assessment model to verify its feasibility and practicability. Compared with the index weights of the code, it was found that the index weights calculated in this paper were more reasonable than those of the code. The presented index weights of suspension bridges are the effective supplement to the current standard, which can provide reference to revise the current standard.

Abstract:An improved finite bar element method was developed to analyze the bridge double-piles in high and steep cross slopes based on the characteristics of their bearing capacity. Firstly, an analysis model of double-piles was derived after thoroughly analyzing their bearing mechanism and deformation characteristics. Secondly, the relationship between the residual sliding forces of back pile and front pile was obtained according to the relative position of slope and double-piles. Thirdly, a method was proposed to correct the element stiffness matrix on the basis of general finite element method and mechanics characteristic of piles in high and steep slopes, taking the influence of the “P-Δ” effect and the pile-soil interaction into account, and a corresponding computation program was compiled on the platform of MATLAB. Lastly, a laboratory model test was carried out to verify the validity of the method in this paper, and a design flow chart was proposed. The results show that the computed results are in good agreement with the measured results in model test, thus offering experience for similar engineering.

Abstract:Taking into account the load due to ground displacement and the detachment between a beam and ground, a mathematical model was presented for two kinds of elastic foundation beams under symmetric loads. A kind of beams has a length larger than the width of settlement trough, and another with less length than the width of the trough. Heaviside step function and impulse function were introduced, and their Fourier series expansions were given. According to the established model and making use of the step function and impulse function, an equation set for solving the coefficients of the series that represents the deflection of elastic ground beam was derived. An iteration process to find detachment interval, which is a redundant unknown in the equation set, was put forward. Lastly, verification was done to the proposed series solution by comprising with finite element method. The results show that Fourier series solution is of high accuracy of computation, and can be used as an analytical solution of the elastic foundation beams. To achieve the same accuracy, series solution needs much less amount of calculation. The computed value of detachment interval in the series solution doesn't change with the number of employed series items. In a whole, Fourier series solution offers high accuracy and convenience in dealing with different kinds of loads. It provides an analytical way to effectively solve the problems for an elastic foundation beam under complicated loads.

Abstract:Since the primary cause of the variation of soil deformation modulus lies in the change of soil volume under three-dimensional stress, firstly, a ground foundation soil was regarded as a two-phase medium composed of hole and soil grain skeleton. A unit of ground foundation soil was abstracted into a unit of hollow spherical shell. An analytical model on the relationship among deformation modulus of ground foundation soils and soil grain skeleton as well as soil porosity was deduced by the Walsh formula and the displacement formula of spherical shell under volume stress. On this basis, the nonlinear characteristics of deformation modulus change of ground foundation soils was considered and the thought of step-loading was introduced, and then an iteration relation model of deformation modulus of ground foundation soils under incremental volume stress was developed. Afterwards, the effect of three-dimensional stress was taken into account, and another thought of layer-wise summation combined with step-loading was adopted. A new ground foundation settlement analysis method was then proposed by using the above-mentioned iteration relationship model for deformation modulus variation of ground foundation soils. It can not only reflect the influences of three-dimensional stress and deformation modulus variation of ground foundation soils on the analysis of ground foundation settlement, but also avoid the use of the compression curve of ground foundation soils or the static load test curves of ground foundation. Finally, the computation and analysis of practical engineering examples as well as the comparisons between the measured and calculated settlement results by the other existing methods show that the model and method proposed are more reasonable and feasible.

Abstract:Field survey, systematic sampling and laboratory tests were conducted to study the thermal deterioration of superficial layer on the rammed earthen ruins, taking the Wuwei Ming Great Wall at Gansu in China as an example. X-ray diffraction and SEM observation indicate that the superficial layer is characterized by obvious weathering and smoother surface when compared with the host soil. Thermal deterioration simulation test shows that the thermal conductivity coefficient, thermal diffusion coefficient and specific heat of volume in the superficial layer are lower than those of the host soil. The conductivity coefficient and thermal diffusion coefficient keep relatively stable during the thermal deterioration simulation process. It is concluded that, under the effect of temperature variation, interface thermal stresses are generated due to the thermal-parameter difference between the superficial layer and host soil, and then the sustaining action of thermal-stress difference results in the fatigue failure and detachment of superficial layer.