ABSTRACT

Experimental study on the mechanical property of steel reinforced
concrete short columns of t-shaped cross-section

Li Zhe¹　 Zhang Xiaofeng²　 Guo Zengyu¹　 Xu Kai³
(1．Xi’an University of Technology，Xi’an　710048，China; 2．Zhangjiagang Architectural Design & Research Institute Co., Ltd., Zhangjiagang　215600, China; 3．Tianjin Institute of Landscape Pianning ＆ Design, Tianjin 300042, China)

Abstract: This study on the mechanical performance of Steel Reinforced Concrete Short Columns of T-Shaped Cross-section has been carried out through fourteen tests. The focus is the effects of axial pressure ratio(nt), stirrup ratio(ρv), shear span ratio(λ) and steel ratio(ρss) on the shear strength and the anti-seismic performance of SRCTSSC. It can be concluded that the shear strength of SRCTSSC increases with the increases of nt and ρss , and that the shear strength of SRCTSSC decreases with increase of λ. The shear resistance formula for T-shaped columns is derived, and the calculated results are consistent with those of the tests. The hysteretic loops of the SRCTSSC are full, the hysteretic behavior is improved, and the displacement ductility increases with increases of ρv and ρss, decreases with the increase of nt, with the degree of variation in high axial pressure ratio being larger than in low axial pressure ratio. If steel bars are added, the shear strength and displacement ductility of SRCTSSC increases significantly, and the capacity of energy dissipation is also enhanced.
Keywords: steel reinforced concrete; T-shaped short column; displacement ductility; shear bearing capacity

E-mail: lizhe009@163.com

Evaluation of influences of various moment magnifying coefficients at
column ends of RC frames on seismic performance

Cai Jian　 Zhou Jing　 Fang Xiaodan
(South China University of Technology, Guangzhou 510640, China)

Abstract: Enlarging the flexural strength at columns ends is one of the key measures in the seismic perfomence-based design, which could induce the“column hinge mechanism”in the RC frames to dissipate energy during earthquake. The present study is to evaluate the seismic performance of RC frames with various moment magnifying factors of columns (from 0.8 to 2.4). At first, the failure probability of“strong column-weak beam”design for a RC frame with single beam-column joint is analyzed. And then the randomnesses of peak ground accelerations and major design parameters influencing flexural strength ratios between columns and beams are considered in 3- and 6-storey RC frames. The Monte Carlo simulation is performed to evaluate the probabilities of aseismic demands exceeding the column side-sway capacity for both storeies and buildings during forming“column hinge mechanism”. The results indicate that the　 acceptable probability of forming“column hinge mechanism”can be achieved if the moment magnifying factors of columns are no less than 2.0. An incremental dynamic analysis is conducted for a 6-storey frame, and seismic fragility curves for evaluating the moment magnifying factors of columns are produced.
Keywords: moment augment factor of column; reliability; strong column weak beam; column side-sway mechanism; fragility curve

E-mail: cvjcai@scut.edu.cn

An innovative external prestressing method
with carbon fiber sheet anchored to structures

Zhuo Jing^1,2　Li Tangning¹　Xing Shijian¹　Zhou Mi¹
（1.ChongQing University，Chongqing 400045, China;
2. ChongQing Transportation Research and Design Institute, Chongqing 400045, China )

Abstract: An innovative external prestressing method was designed by anchoring carbon fiber sheet (CFS) to the structure. Several WSGG anchors were be used. The WSGG anchors were fixed first at both ends of CFS, and then other WSGG anchors were tightened. When the WSGG anchors in the middle of CFS were being tightened, the CFS was tensioned. To validate the present innovative prestressing method, nine aging beams were collected from the Cheng-Yu highway and three of them were strengthened by present method. It is conformed that the present method is simple and convenient, the technic is feasible, and the strengthening effect is visible.
Keywords: pr-stress;　CFS;　 strengthening;　WSGG anchor

E-mail: yakzj@163.com

Test and analysis of the seismic performance of SRC columns of irregular sections

Cao Wanlin¹　Fan Tai¹　Zhang Weibin²　Yang Xingmin¹
(1. Beijing University of Technology，Beijing 100022，China;
2. IPPR Engineering International, Beijing 100089,China)

Abstract: SRC columns of irregularly-shaped sections, something like table tennis racket, are employed in the Beijing Fortune Plaza. Previous research on this type of SRC column has not been known. In order to understand the seismic behavior of this type of SRC column, three irregularly-shaped and one circular SRC columns of 1/4 scale were designed and tested with low cyclic loading. The load-carrying capacity, stiffness and its attenuation, ductility, hysteretic property and failure mechanism of the irregularly shaped columns were studied and compared with those of the column of a circular section. The load-carrying capacity of the test specimens was calculated with the strip method, and the calculation results agree well with the experimental results. The test and study indicate that this type of SRC column has good seismic behavior and meets the demand if rationally designed.
Keywords: steel reinforced concrete; column with irregularly-shaped section; seismic performance; axial compression ratio; the steel ratio

E-mail: wlcao@bjut.edu.cn

Numerical simulation of creep-damage failure process of
concrete under sustained tensile loading

Xu Tao^1,2　 Lin Gao¹　Tang Chun-an¹　　Hu Zhiqiang¹　 Zhu Wancheng³
(1.Dalian University of Technology, Dalian 116024, China; 2.Dalian University, Dalian 116622, China;3. Northeastern University, Shenyang 110004, China)

Abstract: The rheological model of concrete in the process of failure is coupled in series with the time-dependent constitutive relationship of concrete damage and deformation in the Material Failure Process Analysis (MFPA2D) code, which is then employed to simulate the progressive creep failure of concrete specimens under sustained tensile loading and the typical time-dependent deformations, including the transient creep, the steady-state creep and the accelerating creep. The numerical results indicate that the macroscopic creep failure is induced by clusters of microfracturing on a meso scale. The fact that the simulations are in good agreement with the laboratory observations indicates that the rheological model is appropriate for investigating the nonlinear creep failure of concrete structures.
Keywords: concrete; creep; damage; failure process; sustained loading; numerical simulation

E-mail: neuxutao@126.com

Conceptual design of important buildings to mitigate terrorist explosion attacks

Tian Zhimin¹　　Zhang Xiangbai¹　　Du Xiuli²
(1.The Forth Engineer Scientific Research Institute of the Headquarters of the General Staff, Beijing 100850, China；2. Beijing University of Technology, Beijing 100022, China)

Abstract: The hazards on buildings due to terrorist explosion attacks in recent decades are investigated and the conceptual design of important buildings (e.g. government office, commercial complex, large residential building) to mitigate the terrorist explosion attack damage is proposed.　It is emphasized that the conceptual design should begin with the site selection and the architectural planning, and all measures to mitigate terrorist explosion attack damage should be considered in the design. These measures include techniques such as physical space planning to minimize the hazards of explosion on people and property by deliberate planning of building locations, organization of space, and other nonstructural features. Planning engineer, architectural engineer, structural engineer, blast specialist and security consultant should collaborate closely in the conceptual design.
Keywords: important building; mitigation of terrorist explosion attack; architectural planning; conceptual design

E-mail: zhimintian@163.com

Semi-active control on seismic responses of vibration-insulated urban elevated bridges

Li Zhongxian　 Yue Fuqing　 Zhou Li
(Tianjin University, Tianjin 300072, China)

Abstract: Semi-active control via magnet rheologic (MR) dampers for control of the relative displacement between adjacent segments of a seismic isolated continuous girder bridge is investigated, and fuzzy logic control (FLC) is performed by combing offline optimization and online self-tuning. Taking the relative displacement between adjacent segments as the objective function to be minimized, the membership function, the quantification factor and the scaling factor of basic FLC are offline optimized by using a genetic algorithm (GA). The quantification and scaling factors of the optimized FLC are self-tuned online. The semi-active control for a simplified four degrees of freedom system of an isolated multi-span continuous girder bridge is numerically simulated, and the control effects for different control strategies are compared. The results indicate that the control effect of installing MR dampers between superstructure and piers on the relative displacement between adjacent segments of bridge is superior to that of installing MR dampers between adjacent segments. Relative displacement and bearing deformation may be effectively decreased by employing the semi-active control strategy. Comparing with the conventional FLC and the FLC optimized by GA only, the FLC with online self-tuning performance has better control effect and robustness.
Keywords: urban elevated bridge; seismic response; seismic isolation; semi-active control; magnetorheological (MR) damper; fuzzy logic control (FLC); genetic algorithm; self-tuning

E-mail: zxli@tju.edu.cn

Model test on the cable anchorage of the main girder of the Hangzhou Bay Bridge

Zhu Jinsong¹　 Xiao Rucheng²　 Cao Yishan²
(1.Tianjin University, Tianjin 300072, China; 2.Tongji University, Shanghai 200092, China)

Abstract: A 1∶3 model of the cable anchorage of the Hangzhou Bay Bridge is tested. The bridge is a steel box girder type. The stress distribution, force transfer and safety of the ear plate and steel box girder, the internal force distribution and rotation performance of the pin-hinge, with the cable force ranging from 1.0 to 1.7 times of the design force, are investigated. The safety and rationality of the anchorage are validated by the model test and the finite element analysis. The results indicate that the cable anchorage of the main girder of the Hangzhou Bay Bridge is a reasonably well-designed anchorage structure.
Keywords: cable-stayed bridge; anchorage; pin-hinge connection; model test; stress state

E-mail: zhu.jinsong@163.com

First application of CFRP cables for a cable-stayed bridge in China

Lü Zhitao¹　　Mei Kuihua^1,2
(1. Southeast University, Nanjing 210096, China; 2. Chang’an University, Xi’an 710064, China)

Abstract: In order to promote the development of CFRP cable-stayed bridges in China, a study is carried out on the design and application of the first cable-stayed bridge with CFRP cables in China. In the study, the design essentials of the main components of the bridge are elaborated and their integral performances are analyzed by using the finite element method. Combined with the construction of the bridge, the performances of various types of adhesive anchorages are analyzed, a new type of adhesive anchorage is developed, and five sets of experimental CFRP cables are tested. The manufacture and installation techniques of CFRP cables are elaborated. Based on the results of construction simulation, a scheme to apply the full tension in one single operation is proposed, and the measurement data during tensioning of the cables are analyzed.　
Keywords: cable-stayed bridge; CFRP cable; experimental study; anchor; fabrication technology of cables

E-mail: luzhitao@seu.edu.cn

Limit analysis of the critical depth of circular step-sloped foundation pits

Cui Xinzhuang^1,2　　Jin Qing¹　　Zhu Weishen¹　　Yao Zhanyong¹
( 1. Shandong University, Jinan 250061, China;
2. China Institute of Water Resources and Hydropower Research，Beijing 100044，China)

Abstract: Circular foundation pits often appear in civil engineering design. In order to determine the critical depth of a circular step-sloped foundation pit, an upper-bound method in the theory of plasticity was usually employed. In the analysis, a slip surface was assumed to be the rotational log-spiral surface. Then, a kinematically admissible velocity field was obtained according to the associated flow rule for Coulomb materials, and the energy dissipation rate of the deforming region was calculated with the bulk strain rate. Finally, an optimized model of the critical depth was established. Using this model, the variations of the critical depth with a slope-angle, the ratio of depth to radius of pit and the internal friction angle of the soil were studied. It was found that the arching effect makes the critical depth of the circular foundation pit larger than the critical height of plane-slopes. However, when the ratio of depth to radius of pit is very small, the upper-bound solution of the former will largely approach that of the latter. If the ratio of depth to diameter of pit is less than 10, the arching effect may be ignored and the circular foundation pit can be analyzed as plane slopes with the method of slices. Comparison between the upper-bound solution and the solution from the limit equilibrium method indicates that the former is more accurate than the latter.
Keywords: circular foundation pit; slope; critical depth; limit analysis; upper-bound method

E-mail: cuixz@sdu.edu.cn

Determination of the anchorage depth of rigid anti-slide
piles based on strength reduction method

Hu Xiaojun　 Wang Jianguo
（Hefei University of Technology， Hefei 230009，China）

Abstract: The problems of determining the anchorage depth in slope consolidation engineering are analyzed. The allowable lateral stress of soil layers, not the difference between the passive and the active earth pressure, should conform to the Mohr-Coulomb strength criterion. The classification of a slope project should be considered in selecting the anchorage depth. Anchorage depth is determined usually through mechanical check calculations. The calculation procedure is not only complicated but also difficult in obtaining any rational results. Based on strength reduction, a calculation formula for determining the anchorage depth of rigid anti-slide piles is rigorously derived, with the consideration of the influential factors related to the cantilever-pile method. For different classifications of slopes, corresponding strength reduction coefficients may be selected. Examples show that the calculation results are rational and useful for engineering applications.
Keywords: slope consolidation；strength reduction；rigid anti-slide pile；anchorage depth

E-mail: ahsdxyhxj@163.com

Determination of landslide boundary by fluid inclusions

Xu Jinming　 Sun Kunlun
(Shanghai University, Shanghai 200072, China)

Abstract: Rock landslides result from rock deformations exceeding certain extent. Parameters of fluid inclusions in the rock mass are important microscopic indices of reflecting the change of states. These indices and changes may be employed to determine the boundary of landslide. The Baiheling slope, located near Huzhou City, Zejiang Province, P. R. China, was considered in using clustering and correlation analyses to reveal the relationships among 16 samples, 7 indices and the landslide boundary. The indices include the characteristic parameters (such as aperture, roughness coefficient, distribution density) of fluid inclusion planes and the thermodynamic parameters (such as homogenization temperatures, densities of aqueous and CO2-H2O solutions) of the inclusions. A clustering criterion and method were proposed.　It was shown that these samples may be classified into three groups corresponding to, respectively, the stable area, the boundary and the landslide area. A new technique for determining landslide boundary with fluid inclusions was proposed, which may be employed for analyzing and forecasting rock landslides.
Keywords: fluid inclusion; landslide boundary; characteristic parameter; thermodynamic parameters; clustering analysis; correspondence analysis

E-mail: xjming@163.com

A Vehicle tracking algorithm based on spatial-temporal
Markov random field model

Shi Yi Lu Xiaobo Huang Wei Liu Tao
(Southeast University, Nanjing 210096, China)

Abstract: Robust vehicle tracking algorithm is an important precondition for realizing traffic event detection, but occlusion is a key influence factor for vehicle tracking. An adaptive vehicle tracking algorithm is designed to deal with the problem. In addition, according to the spatial and temporal characteristics of traffic image sequences，using basic Markov theory and Bayesian method, and combining texture information of color image sequences, a spatial-temporal Markov random field model of image sequence is built. After object maps are optimized with the Metropolis stochastic algorithm, the occlusion problem in vehicle tracking is solved. Preliminary experimental result, the tracking success ratio when vehicles are not occluded with each other is 95%, and when being occluded the tracking success ratio is 83%. The experimental results indicate that this tracking algorithm is accurate when being not occluded and acceptable when being occluded.
Keywords: vehicle tracking; occlusion；spatial-temporal Markov random field model；stochastic relaxation algorithm

E-mail: syzy2001@gmail.com

Travel reliability evaluation of emergency vehicles
based on multilevel fuzzy synthesis judgment method

Yang Xiaoguang　 Peng Chunlu
（Tongji University, Shanghai 200092, China）

Abstract: Emergency vehicles have to hurry to the scene whenever accidents occur, though the vehicles may encounter traffic jams and delay the rescue process. The impact of traffic flow on emergency vehicles is analyzed by using the reliability method. According to the travel characteristics and high efficiency requirement of emergency vehicles, the travel states of emergency vehicles are classified into five levels, then the concept of unblocked reliability of emergency vehicles is presented, and a multilevel fuzzy synthesis judgment model is selected for evaluating the unblocked reliability of emergency vehicles. According to this model, the road network is classified into three levels: cells, routes and road network. This is the first time for attention of study being given to the influence of road network traffic demand and supply variation on emergency vehicles, and the results may assist the management departments to evaluate and plan emergency management systems more scientifically.
Keywords: rescue; unblocked reliability; multilevel fuzzy synthesis judgment

E-mail: yxgits@vip.sina.com

Establishing insurance system of housing quality assurance in China

Zhang Shilian　　Ma Ting　　Wang Feng
(Chongqing University, Chongqing 400045, China)

Abstract: There is no doubt that housing quality is significant to the development of real estate industry, and the quality of commercial housing is currently a focus of the whole society in China. How to establish a completed housing quality assurance system is the key to solve housing quality problems and to standardize the construction market. As a popular pattern in international construction market, insurance system for housing quality assurance is an effective method. The status of housing quality and traditional housing quality assurance system in China are presented, and the disadvantages and primary causes of problems in traditional housing quality assurance system are analyzed. Based on economic and legislative measures to solve housing quality problems and the principles for economic development of real estate market, an insurance system is established for housing quality assurance in China, a series of analyses are analyzed for the definition of housing quality insurance responsibilities, the main insurance party’s responsibilities, correlations and effects between parties, and measurements , and proposals are provided for establishing trust and law systems, organizations to set standards and check housing quality are , in order to assure the normal operation of housing quality.
Keywords: housing quality insurance; trust; system

E-mail: cquzsl@126.com

A study on interpolation techniques in the Digital Land Price Model
——the case of Shanghai inner belt-way district

Shi Jiangang　　Li Junming
(Tongji University, Shanghai 200092, China)

Abstract: Two spatial interpolation methods, IDW and Kriging, are studied and their differences　are compared in terms of the process of setting up the Digital Land Price Model. A corroborative analysis was carried out using the sampling data in the area of the Shanghai inner belt expressway. The two methods are applied using a Surfer8.0 software system, based on the land price sampling data of the aforementioned area. The results are then used to obtain the digital land price grid subject charts with the help of the GIS software, MapInfo7.5. The stochastic validation points are selected to compare and analyze the results, which prove that the IDW interpolation method is better than Kriging and correlate closer to the practical land price distribution. Furthermore, the IDW interpolation method is a deterministic method and easy to use in practice, and the interpolation result at swatch point is close to the practical price, making the process of setting up the Digital Land Price Model more credible and feasible.
Keywords: Digital Land Price Model(DLPM)；IDW interpolation；Kriging interpolation

E-mail: shidai@online.sh.cn

Application of DEA in evaluation and optimization of projects

Wang　Yaowu¹　　Wang　Feng¹　　Zhang Yuesong²
(1.Harbin Institute of Technology, Harbin 150001, China;
2.Renmin University of China, Beijing 100872, China)

Abstract: The evaluation of construction projects is of great importance in feasibility studies, since it is related to the investment performance. In order to overcome the disadvantages of single index or inadequate indices in the feasibility study, the method of Data Envelopment Analysis is applied to the multi-objective comprehensive evaluation of different projects during the feasibility study in order to select the optimal projects. The DEA model can be employed to evaluate the relative efficiency of different projects, to decide the optimal orders of construction projects, and to offer more intimate information of the projects concerned that decision-makers would want to know about.　 Besides, it is convenient for decision-makers to get more satisfied projects by adjusting the index system of input and output. Thus DEA model provides a scientific reference for decision-makers.
Keywords: construction project; multi-objective evaluation; Data Envelopment Analysis; relative efficiency

E-mail：ywwang@hit.edu.cn

Study and validation of the relationship between international
roughness index and power spectral density

Zhou Xiaoqing¹　　Yan Li²　　Sun Lijun³
(1. Shanghai Highway Administration Department, Shanghai 200063, China;
2. Shaghai Lander Consulting Engineers Ltd., Shanghai 200070, China;
3. Tongji University ,Shanghai 200092, China)

Abstract: The relationship between International Roughness Index（IRI）and Power Spectral Density(PSD) is studied. Pavement roughness is assumed as random stationary variable and used as the exciting force of theoretical analyses of the quarter car model of IRI. From the frequency response function of the quarter car, the response function of the displacement difference between above-spring and beneath-spring mass is obtained by means of the random process theory. Then the relationship between IRI and mean square value of above-spring mass PSD is established from the statistical characteristics of the response function. Using the longitudinal road profiles of typical roads in Shanghai and the data from the Long-Term Pavement Performance (LTPP) in the US, the IRI and mean square value of above-spring mass PSD of these profiles are calculated by using MATLAB to validate the proposed model.
Keywords：pavement roughness; international roughness index; power spectral density; random process theory

E-mail: zhouxiaoqing3001@163.com