ABSTRACT

A morphosis technique for curved-surface structures of arbitrary geometries
——Height adjusting method and its engineering applications

Cui Changyu¹　Yan Hui²
(1. Sasaki Structural Consultants, Nagoya4680021, Japan；
2. Zhejiang University, Hangzhou310027,China)

Abstract: The structural behavior of curved-surface structures, typically of shells, generally depends on the surface shapes. In engineering, conventional simple curved surfaces would be difficult to coincide with structural rationality. Based on the relationship between the height parameters of structural surface and the total structural strain energy, a morphosis method is developed to construct the arbitrary geometry of curved-surface structures with less thickness but better stiffness. The finite element approach is employed to calculate the differential of total structural strain energy corresponding to surface height parameters. The surface height is adjusted iteratively according to its sensitivity to total structural strain energy. A rational structural surface can thus be found when the total structural strain energy reaches minimum. With this method, different structural surfaces can be obtained by adjusting design parameters such as constraint or space conditions, for designer’s reference. This method can be also applied to modify the architectural original form to solve for an approximately reasonable structural geometry. A design application reveals that the arbitrary surface constructed by using this method can not only keep the structure in a general membrane-stress state but with sufficient rigidity.
Keywords: shape optimization；structural optimization；nonlinear programming；shell

E-mail: ccy@topaz.ocn.ne.jp；yanhuihang@zju.edu.cn

Wind-induced response analysis of a single-layer latticed dome

Li Fanghui¹　Ni Zhenhua²　Shen Shizhao³
(1. Heilongjiang University, Harbin 150086,China; 2. Shantou University, Shantou 515063,China;
3. Harbin Institute of Technology, Harbin 150090, China)

Abstract: This paper discusses the application of the Complete Quadratic Combination (CQC) method and the Mode-Acceleration method to estimate the wind-induce responses of single-layer latticed domes. Wind tunnel tests of a single-layer latticed dome of a rise-span ratio of 0.1 were conducted using the synchronous multi-pressure scanning technique. Based on the spectra of generalized forces obtained from fluctuating wind loads and structural modes, the wind-induced response of the dome were calculated by using the CQC and the Square Root Sum of Square(SRSS), respectively. The effects of different mode-numbers on response accuracy and the correlation among modal response components were examined. It was found that the SRSS is inadequate for this type of structures, and the correlations between modal responses have to be taken into consideration. The spectra of displacement response indicate that the resonant component of the response is significant, and even more so than the background component for some nodes. In contrast to the traditional Mode-Superposition method, in the Mode-Acceleration method the contribution of the truncated high-order modes to response may be compensated approximately by the pseudo-static response of the residual flexibility.
Keywords: single-layer latticed dome; wind induced response; mode-acceleration method; static compensation; wind tunnel test

E-mail: zhni@stu.edu.cn

Time-domain analysis on wind-induced dynamic response of long span
power transmission line systems

Guo Yong^1,2　Sun Bingnan²　Ye Yin³
(1. Zhejiang Tongji College of Science and Technology, Hangzhou 311231, China;
2. Zhejiang University,Hangzhou 310027, China;
3. Zhejiang Electric Power Design Institute, Hangzhou 310014, China)

Abstract: The tallest transmission tower in the world, a part of the Zhoushan long span transmission line system, is studied and a spatial finite element model of the tower-line coupled system is established. The wind-induced dynamic response in time-domain is analyzed, also the wind tunnel experiment on an aeroelastic model is conducted. Based on both the theoretical analysis and experimental study, the system response can be divided into background response and resonant response, and the influence of the transmission line is considered in the analysis. A simplified method for calculating the dynamic response is proposed according to the different features of the two types of responses; the background response can be calculated with the covariance analysis based on the quasi-static assumption, and the resonant response can be calculated more easily after simplifying the transmission line system into a suspended mass pendulum system. Superposition of the two types of responses is the actual wind-induced dynamic response of the tower-line system.
Keywords: long span transmission line system; wind-induced dynamic response; covariance analysis；suspended mass pendulum system; time-domain analysis

E-mail: gy_guoyong@126.com

Analysis of time-variant stiffness excitation effects of elastoplastic dynamic structural systems

Huang Qingfeng　　Wang Quanfeng
(Huaqiao University, Quanzhou 362011, China)

Abstract: The mechanism of yield-unloading excitation for elastoplastic dynamic structure systems is analyzed, and a method is presented to calculate the excitation effects. A study on the moving modal space indicates that there exists a Coriolis acceleration division in the motion of an elastoplastic dynamics structural system that correlates to the time-variant stiffness excitation leading to the yield unloading effect. Based on a time-dependent integral analysis in which the dynamic system stiffness is stationary in time, a supplementary energy equation is established to describe the changes in energy distribution caused by the changes of the secant stiffness vector. In the paper, a computational procedure for the time-variant stiffness excitation effect is proposed.
Keywords: time-variant stiffness; movement modal space; Coriolis acceleration; yield unload; supplementary energy equation

E-mail: kfsdbt@yahoo.com.cn

MDOF substructure pseudo-dynamic testing for complex tall buildings

Huang Liang　 Shi Chuxian　 Liu Guiqiu　 Xiong Hui
(Hunan University，Changsha 410082,China)

Abstract: A substructure pseudo-dynamic testing method, in which both the PSD tested part and the numerically operated part are of MDOF, is studied. Seismic testing has been carried out for a new structure-a frame-supported reinforced masonry shear wall, to illustrate that the substructure pseudo-dynamic testing method can not only obtain the dynamic performance of the structure, but also characterize the structural displacement and force distributions under earthquake. In addition, the testing method can also obtain the drift-shear relationships of different stories. Therefore, the substructure pseudo-dynamic testing method is shown to be an effective tool for investigating the seismic behavior of complex tall buildings.
Keywords: substructure pseudo-dynamic testing；MDOF；PSD tested part；numerically operated part；complex tall building

E-mail: huangliang2003@yahoo.com.cn

Performance of perforated wood-frame shear walls with transverse walls and vertical load

Cheng Haijiang¹ Ni Chun² Lü Xilin¹
（1. Tongji University, Shanghai 200092，China；
2. Forintek Canada Corp., Vancouver, B.C., Canada V6T1W5）

Abstract: Light wood-frame structures are currently being developed in China. The purposes of the wood-frame shear wall tests are to promote the application of light wood-frame structures in China and to provide technical supports for the revision of China’s wood design codes. In this connection, six shear walls were tested under monotonic and cyclic loads, respectively, and the effects of the opening size, vertical load and flange wall on the strength, stiffness, ultimate displacement, stud lift and energy dissipation of the shear walls were studied. Test results indicate that the structural performance of the shear walls can be significantly improved due to the vertical load on the top of the shear walls, while the improvement due to the vertical load on the flange walls is slight. Different opening sizes have a direct impact on the ultimate displacement of the shear walls. Failure of the shear walls are mainly in the mode of nail connection failure and uplift of end studs.
Keywords: wood structure；light wood-frame structure；wood-frame shear wall；cyclic test；nail connection

E-mail: Chenghj@gmail.com

A study on the compressive performance of rectangular concrete
columns confined with CFRP sheets

Liu Tao^1,2 Feng Wei² Zhang Zhimei^1,2 Wei Gaofeng³
（1. Shanghai University, Shanghai 200072 ,China；
2. Shanghai Institute of Applied Mathematics and Mechanics, Shanghai 200072, China；
3. Shandong Institute of Light Industry, Jinan 250100 , China）

Abstract: Cross sections of concrete columns varying gradually from square to circular, wrapped with carbon fiber reinforced polymer(CFRP)sheets, were experimentally studied. The relationships between the axial compressive stress, axial and lateral strains of the concrete columns were analyzed, an efficiency factor of CFRP strain is proposed and the lateral confinement mechanism of FRP materials for rectangular columns is explored. New formulae for effective confinement area and lateral confinement pressure are proposed. Models for predicting compressive strength and its corresponding strain are developed on the basis of existing results. A bilinear stress-strain model is suggested for predicting the entire stress-strain curve of adequately CFRP-confined columns. The theoretical curves agree well with the experimental data.
Keywords: carbon fiber reinforced polymer(CFRP)sheet; rectangular concrete column; lateral confinement; efficiency factor of strain; bilinear model
E-mail: liutao27@staff.shu.edu.cn

Numerical simulation of the mechanical behaviors of RC
columns of specially-shaped cross section subjected to high temperature

Wu Bo　Xu Yuye
(South China University of Technology, Guangzhou 510640, China)

Abstract: Based on the nonlinear incremental finite element method for reinforced concrete (RC) sections under the combined action of force and temperature and the simplified fire resistance analysis method for RC columns, an analytic code, RCSSCF, is developed for RC columns of specially-shaped (e.g., +, T and L-shaped) cross sections subjected to high temperature. The second-order effect of axial force is considered and the reliability of the code is validated by using the test results provided by other researchers. A method of“Temperature-Flow Mapping”is presented for the concrete when the stress is on the unloading straight line, and a method is provided for computing the strain tangent modulus, the temperature tangent modulus and the time tangent modulus. The performances of columns of different shaped cross sections exposed to fire are analyzed and compared, including the area percentage of the seriously damaged zone where the temperature exceeds 500℃ to the whole cross section and the fire resistance of columns with different axial load ratios. The studies indicate that:(a)the performance of special-shaped cross section columns performs worse under fire than a square cross section column;(b)the axial load ratio has a significant effect on the fire resistance of the columns of special-shaped cross sections; and(c)the fire resistance of the column of+shaped cross section is better than that of the column with T-shaped cross section, and the fire resistance of the column of T-shaped cross section is better than that of the column of L-shaped cross section.
Keywords: reinforced concrete; column with special-shaped cross section; high temperature; mechanical behavior; fire resistance; numerical simulation

E-mail: bowu@scut.edu.cn

Experimental study on semi-connected edge joint with core steel tube in CFST

Wang Yihong¹　Jiang Jianfei²　Zhou Xuhong¹　Fu Min¹　Guo Zenghui¹
(1.Chang’an University, Xi’an 710061, China;
2.Guangzhou Kinghi Design Firm, Guangzhou 510300, China )

Abstract: A new type of semi-connected edge joint with core steel tube which connects concrete filled steel tubular(CFST)column with RC beams was proposed. The joint has several attributes in construction, including that a reduced strength of the joint when the outer steel tube is broken-off in three directions connected with the beams and it is compensated by setting the core steel tube, the outer steel tube is kept connecting in other side without the beam, the longitudinal bars in the beams pass through the joint, and the concrete is monolithically cast in the region of joint. From the tests, a number of the joint behaviors were investigated, such as the failure process and failure formation, load-strain relationship of the specimens, the effect on joint by beams and its local connection with outer steel tube. The results of the model tests are in good agreement with that of finite-element analysis. It is also shown that the joint has good strength and rigidity, and the load-carrying capacity of the joint is greater than that of beams and columns. When the specimen failed, the core steel tube of the joint still shows its load-bearing capacity. The local connecting outer steel tube of the joint can take protective effect on the concrete of the joint and be beneficial for the butt connection of the column in construction.
Keywords: concrete filled steel tube(CFST); joint; core steel tube; experimental study; finite-element analysis

E-mail: Wangyh@chd.edu.cn

Mechanical performance of steel-concrete composite box beams with external tendons

Zhang Nan¹　Hong Yingwei²
(1. Nanjing University of Technology, Nanjing 210009, China;
2. Communication Design Institute of J.X. Province, Nanchang 330002, China)

Abstract: A new type of steel-concrete composite box beam with external tendons is proposed, and experimentally compared with common steel-concrete composite box beams, to determine the difference in the mechanical performance of steel-concrete composite box beams with and without external tendons, such as strain distribution, interface slip, stiffness and ultimate strength, etc. The experiment results prove that the stiffness and the ultimate strength of the steel-concrete composite box beam are increased by 54.15 % and 27.72 %, respectively, through using external tendons. As a result of the external tendons, the degree of brittle failure of the steel-concrete composite box beam is reduced, the structural strength and stiffness is improved, and the distribution and increment of strains in the sections are more rational, indicating a better mechanical performance. The study demonstrates that the section strain along the width is nonlinearly distributed and that the effect of the shear lag is not constant and changes with the increment of the load. It is also found that there is a close relationship between the stress in external tendon and the maximum compressive strain of the concrete flange slab. Based on the experiment results, a nonlinear analysis model and the calculation equations of the ultimate strength of steel-concrete composite box beams with external tendons are established. There is good agreement between the calculated and experimentally measured ultimate strength.
Keywords: external tendon; steel-concrete composite box beam; mechanical performance
E-mail: jiaodazhang@126.com

Non-linear parametric vibration of cables in cable-arch composite structures

Zhao Yueyu　　Lü Jiangen
(Hunan University, Changsha 410082, China)

Abstract: Cable-arch composite structures are important temporary structures during the erection of the long-span arch bridges. A nonlinear mechanical model is presented for the parametric vibration of cable-arch composite structures. The nonlinear equations of motion of cable-arch composite structures are derived, the static sag of the cable as well as the geometric nonlinearity is considered, and a simple connection condition and boundary condition of the cable-arch composite structures are applied. Using the multi-scale perturbation method, the parametric and sub-harmonic resonances of cables are analyzed. These results indicate that small scale vibration of the arches may stimulate the cables to undergo large scale movements when the local vibration frequency of the arches is within certain limits, it affects the cable-arch structure and the stability and security in the process of long-span arch bridge constructions. For a system with the damping and the frequency ratio given, sufficiently low excitation amplitudes may avoid system parametric resonance.
Keywords: cable-arch composite structure；cable；parametric resonance；subharmonic resonance

E-mail: lvjiangen77@yahoo.com.cn

Experimental study on concrete-filled steel tube tied-arch bridge with CFRP hangers

Cao Guohui^1,2　 Fang Zhi¹　 Zhou Xianyan³
(1.Hunan University,Changsha 410082,China；2.Hunan City University,Yiyang 413000,China；
3.Central South University of Forestry and Technology, Changsha 410004,China)

Abstract: Carbon fiber reinforced polymer(CFRP)tendons have excellent physical and mechanical properties, it can be used as hangers on concrete-filled steel tube tie-arch bridges. A kind of resin bond type anchors has also been developed; it can adjust tension of CFRP hangers and may be applied in concrete-filled steel tube tied-arch bridges. In the present paper some tests on steel tube arch bridge model and concrete-filled steel tube arch bridge model are introduced respectively, their mechanical and geometrical behaviors were tested and compared. During tied-beam prestressing the tension forces of CFRP hangers, vertical deflection and stresses of tied-beam and steel tube arch were measured. Comparing with steel tube arch bridges, the tension forces of hangers, vertical deflections of tied-beam, compressive stresses of steel tube, cracking widths of tied-beam of concrete-filled steel tube arch bridges under similar load are all smaller. It shows that mechanical and geometrical behaviors of concrete-filled steel tube arch bridges are better than those of steel tube arch bridges. The tests also provide a series of experimental data for the application of CFRP hangers in concrete-filled steel tube tied-arch bridges.
Keywords: carbon fiber reinforced polymer(CFRP); hangers; concrete-filled steel tube; tied-arch bridge

E-mail: cgfcivil@163.com

Wind stability of long-span suspension bridges using carbon fiber reinforced polymer cables

Zhang Xinjun　Ying Leidong
(Zhejiang University of Technology, Hangzhou 310014, China)

Abstract: To understand the applicability of carbon fiber reinforced polymer(CFRP) cables for long-span suspension bridges, the aerostatic and aerodynamic stability of a suspension bridge having a main-span of 1490m using CFRP cables is studied by using 3-D nonlinear analyses. The cross-sectional area of the cables is determined by the principle of equivalent axial stiffness. In comparison with a bridge using steel cables, the effects of different cable materials on wind stability of the bridge are discussed. The results indicate that with CFRP cables, the structural deformation of long-span suspension bridges is increased under static wind action. However, the aerostatic stability of the bridge is basically the same as that of the bridge using steel cables. On the other hand, due to the remarkable increase in torsional frequency, the aerodynamic stability of the bridge is superior to that of the bridge using steel cables. Therefore as far as wind stability is concerned, the use of CFRP cables in long-span suspension bridges is feasible, and the cross-sectional area of the cables should be determined by using the principle of equivalent axial stiffness.
Keywords: long-span suspension bridge; carbon fiber reinforced polymer cable; aerostatic stability; aerodynamic stability

E-mail: xjzhang@zjut.edu.cn

Identification of moving loads on bridges using a grillage model

Li Zhongxian　　Chen Feng
(Tianjin University, Tianjin 300072, China)

Abstract: For girders generally used in highway bridges and urban overpasses, a novel method based on a grillage model is proposed to identify moving loads on bridges. The equations of motion of a bridge model under the action of moving loads are derived, and the discrete modes and modal parameters of the bridge are obtained by using the subspace-iteration algorithm. The simulated responses of the bridge are obtained by employing the Newmark-β step-by-step integration method, subsequently stable solutions for the moving loads are obtained by combining the spline function approximation method with a truncated singular value decomposition regularization method. Identification for the time-variant force on a simply supported composite girder and the contact force on a three-cell continuous concrete girder is numerically simulated, considering such factors as noise, load eccentricity and road roughness. The simulated results indicate that the grillage model can indeed simulate the vehicle-bridge interaction of girder bridges via a rational mesh and the principle of equivalence. The proposed moving load identification method based on the grillage model is reliable, efficient and applicable to a wide range of brdiges.
Keywords: bridge; moving load identification; grillage model; spline function approximation; truncated singular value decomposition; regularization
E-mail: zxli@tju.edu.cn

Probability analysis of the curvature limit state and ductility of circular RC bridge piers

Wang Jianmin　　Zhu Xi
(Beijing Jiaotong University，Beijing 100044，China)

Abstract: The curvature limit state and curvature ductility factor of circular reinforced concrete bridge piers are investigated in terms of the uncertainty in deformation capacity. Material and geometric parameters are modeled as random variables, and using the LHS simulation, the probabilistic parameters of the limit states of dimensionless yielding, serviceability and damage control curvature are calculated for different axial load ratios, longitudinal reinforcement ratios and transverse reinforcement ratios. The results indicate that the dimensionless curvature limit state generally follows a normal distribution, that the axial load ratio is the main factor affecting the mean value of the dimensionless yielding and serviceability curvature limit states, and that the axial load ratio and transverse reinforcement ratio are the crucial factors associated with the dimensionless damage control curvature limit state. Furthermore, the characteristic values of the curvature ductility factors for the serviceability and the damage control limit states are obtained, and two equations for estimating the characteristic values of the curvature ductility factors are developed through regression analysis.
Keywords: bridge column; curvature; ductility; limit state; probabilistic analysis; Latin hypercube sampling simulation

E-mail: wangwujianmin@163.com

A model test study on displacement of piles under inclined and eccentric loads in layered soils

Zhao Minghua¹　Li Weizhe^1,2　Yang Minghui¹　Shan Yuanming¹
(1. Hunan University, Changsha 410082, China；
2. Communications Design Institute of J.X. Province, Nanchang 330002, China)

Abstract: Model tests of 6 timber piles in two groups, with clay simulating upper soft soil and sand simulating bearing stratum, were conducted through a self-designed self-balancing apparatus for inclined and eccentric loading. The purpose of this study is to investigate the effects of free pile length above ground, pile stiffness and eccentricity on the displacement of piles. Analysis of the test results illustrates that the displacement of piles under inclined and eccentric loads is obviously nonlinear. A semi-empirical formula is presented for calculating the displacement of piles under both eccentric and inclined loads, with a relative error being under 15%.
Keywords: model test; model pile; layered soils; slight inclination; eccentric and inclined load; non-linear; P-Δ effect

E-mail: mhzhaohd@21cn.com

On geotechnical-geomechanics model test system and its application

Zhang Qiangyong¹　Li Shucai¹　You Chun’an²
(1. Shandong University, Jinan 250061, China;
2. Shandong Science and Technology University, Qingdao 266400, China)

Abstract: A new type of geomechanics model test system is developed. The system includes box-type rack installation, load-change plate with flat jacks, and hydraulic pressure control test-bed. The box-type rack installation is for holding test model and providing reaction-force, the load-change plate with flat jacks for exerting non-uniform pressure to the model, and the hydraulic pressure control test-bed for exerting pressure and automatically stabilizing pressure. The system possesses several outstanding advantages, such as large-scale loading, good stability, variable specimen sizes, synchronous non-uniform loading, and fast time-dependent loading. The system has been applied to a 3-D geomechanics model test of a large-scale project involving bifurcated tunnels. Design and construction of the project has been effectively guided and optimized by use of the test results.
Keywords: geomechanics model test system; box-type rack installation; load-change plate; hydraulic pressure control test-bed; 3-D test model of bifurcation tunnel

E-mail: qiangyongz@sdu.edu.cn

Research study on prediction of pressure waves in tunnels

Wang Lei¹　Wan Xiaoyan²　Yu Nanyang¹　Wu Jian²
(1. Southwest Jiaotong University, Chengdu610031, China；
2.Southwest Research Institute of china Railway Engineering, Chengdu 610031,China)

Abstract: The method of numerical simulation has become more and more important, because it can calculate the pressure wave at different operation conditions and can result in considerable cost-saving than the field experiment and model test method. However, some arguments do exist about the reliability of the approach in china because of the scarcity in filed experimental data. In order to verify the reliability of the numerical simulation program for predicting the pressure waves in tunnel proposed by the authoer, tunnel pressure waves caused by different train through Jingzhuling and Songlinbao tunnels at different speeds were calculated and the simulated results were compared with experimental data of Sui-Yu high-speed railway. The results showed that the maximum and minimum errors between the measurements and the computations are less than 5%, which can meet the allowance for engineering application. This proved that the numerical simulation program of the tunnel pressure waves was accurate and reliable. At last, the author analyzed the origin of error, which pointed out the direction to improve and perfect the numerical simulation program.
Keywords: air pressure wave; tunnel; applied software; method of characteristics
E-mail: wangleihello@163.com

A study on the capacity of exclusive right-turn lanes of at-grade intersections

Ma Zedan　　Yang Xinmiao
(Tsinghua University, Beijing 100084, China)

Abstract: Although vehicles are allowed to make right turn at a signalized intersection, the interfused pedestrian and cyclist has seriously interrupted the right turn movement. Based on field investigations at several typical intersections in Beijing, the right-turn vehicle behavior, including the conflict between bike and cars, delay and lane capacity, is analyzed. A spatial-temporal partition method is proposed, to estimate the capacity reduction and delay of the right-turn lane. Using the case studies on several typical intersections in Beijing, a comparison between the proposed model and the HCM method indicates that the spatial-temporal partition method is closer to reality.
Keywords: right turn lane; mixed traffic; capacity

E-mail: mzd@mails.thu.edu.cn

Empirical analysis on the critical factors of construction projects with different results

Huang Dingxuan^1,2　You Jianxin¹　Du Bo²
(1. TongJi University, Shanghai 200092, China;
2. Qingdao Construction Group, Qingdao 266071, China)

Abstract: Based on a structural equation model (SEM), an academic model is proposed for the critical factors of construction projects with different results. This method overcomes the shortcoming of quantitative analysis on the critical factors of construction projects. The SEM software is employed to test the construction project samples with different results from different places in China. The results indicate that different factors, such as harmonic cooperation in project, innovative project course management, project preparing, risk sharing, mutual understanding, promise and stimulation, communication, all have distinct effects on the construction projects, among which, harmonic cooperation is the most important critical factor in the successful construction projects, by contrast, promise and stimulation are the most important influential factors in the unsuccessful construction projects. The quantitative analyses are in good agreement with the construction project samples from different places in China.
Keywords: construction project; critical factor; structural equation model; different result

E-mail: huangdingxuan@126.com

On risk register for construction of 2008 Olympic venues

Zhu Difei¹　Fang Dongping¹　Wang Shouqing¹　Dai Mengdong²　Lü Xiaoquan²
(1. Tsinghua University, Beijing 100084, China;
2.Beijing Organizing Committee for the 29th Olympic Games, Beijing 100083, China)

Abstract: The 2008 Olympic venues construction risk management system consists of two portions: risk management tools (risk register and project risk assessment system) and risk management framework(work procedure and organization structure). This paper focuses on the development of the risk register. The objectives of 2008 Olympic venues construction program were established and 242 risks were identified. After the risk evaluation and significance ranking, 112 critical risks were extracted from the identified risks, which were then structured to develop a risk breakdown structure. Mitigation measures for and the owners of each direct risk were proposed. The developed risk register has been used to assist the management of risks for the Olympic venues construction program.
Keywords: Olympic venues construction; risk management; risk register

E-mail: zdfei00@mails.tsinghua.edu.cn