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Chen Z.Y.,Tongji University | Chen Z.Y.,Shanghai Key Laboratory of Engineering Structure Safety | Chen W.,Tongji University | Zhang W.,Shanghai JiaoTong University | Lou M.L.,State Key Laboratory of Disaster Reduction in Civil Engineering
International Journal of Computational Methods | Year: 2016

High axial force in central columns induced by strong vertical earthquake component is one of the most important factors in failure of subway stations. In this paper, the pushover method is adopted to simulate nonlinear behaviors of a multi-story subway station in Shanghai with different axial compression ratios through the general purpose finite element code ABAQUS. To simulate concrete material degradation during an earthquake accurately, the concrete damaged plasticity model was selected to trace damage characteristics of central columns. The softening index was used to describe the damage of the overall structure. Numerical results showed that in the structure level, the increase of axial compression ratio leads to the remarkable decrease of the structure ductility. The value of the softening index become less, which implies that the range and magnitude of damage to the structure become less either. However it should be noted that damages may be concentrated on certain members of the structure, such as central columns which are commonly considered to be the weakest but most critical part of an underground structure. In the member level, numerical results also showed that the increase of axial compression ratio led to small eccentric compression failure of central columns and accelerated the development of their compression damage. © 2016 World Scientific Publishing Company.


Han C.,Nanjing Southeast University | Xu Z.,Nanjing Southeast University | Xu Q.,Shanghai Key Laboratory of Engineering Structure Safety | Xu Q.,Shanghai Research Institute of Building Sciences | And 4 more authors.
Jianzhu Jiegou Xuebao/Journal of Building Structures | Year: 2016

To investigate the mechanical properties and failure mode of fire-damaged RC continuous T-beams with high-strength rebars strengthened with glued steel plates and screwed steel plate, 6 specimens were experimentally studied by static load tests. The test results show that the flexural capacity of strengthened specimens glued with steel plates has a 39.1%~58.2% increase, the ultimate displacement has a 17.8%~53.2% decrease, the flexural capacity of strengthened specimen screwed with steel plate has a 36.7% increase and the ultimate displacement only has a 4.4% decrease. The initial flexural stiffness of the screwed strengthened specimen is as the same as the unexposed control specimens, and the glued strengthened specimen has an obvious increase. The amplitude and gradient of the strain of steel plate are bigger near the mid-span. The deformation ductility factor of strengthened specimens with one layer of steel plate has a 53.4%~62.0% increase, while the energy ductility factor has a 62.6%~72.6% increase. With the strengthening steel plate both on the bottom and on the top, the deformation ductility factor has an 8.2% decrease, while the energy ductility factor has a 7.2% decrease. Based on the reduction of cross-section method, the calculated flexural capacity of strengthened specimens only has a 0.2%~13.2% error compared to the test results, which can completely satisfy the engineering precision requirement. © 2016, Science Press. All right reserved.


Han C.,Nanjing Southeast University | Xu Q.,Shanghai Key Laboratory of Engineering Structure Safety | Xu Q.,Shanghai Research Institute of Building Sciences | Liu Q.,China Railway Siyuan Survey and Design Group Co. | And 2 more authors.
Jianzhu Jiegou Xuebao/Journal of Building Structures | Year: 2015

To investigate the fire endurance and resistance of RC continuous T-beams under ISO 834, four specimens at different load levels were experimentally studied and analyzed using FEM. It shows that the control specimen and the exposed specimens all collapsed with the flexural failure mode, but the sequence of plastic hinge development are opposite. The fire endurances of specimens were 160, 99 and 58 min respectively when the load levels were 30%, 50% and 70% of the ultimate load. It is found that the fire endurance of RC continuous T-beams exposed to fire decreases gradually when the load level is increased. The residual mid-span displacement of RC continuous T-beams after fire increases when the load level is increased. Test results show that the distribution of temperature field of the flange plate is similar to the one-side exposed RC slab, and the distribution of temperature field of the web is similar to three-side exposed RC rectangular beams. It is the main cause of the redistribution of internal force that the stiffness of the cross-section of RC continuous T-beam is decreased in the process of the fire. FEA was also conducted and its predictions of the fire endurance, the temperature field and the failure process are all in good agreement with the test results. ©, 2015, Science Press. All right reserved.


Li B.,Beijing Jiaotong University | Li B.,Beijings Key Laboratory of Structural Wind Engineering and Urban Wind Environment | Tian Y.-J.,Beijing Jiaotong University | Tian Y.-J.,Shanghai Key Laboratory of Engineering Structure Safety | And 2 more authors.
Zhendong Gongcheng Xuebao/Journal of Vibration Engineering | Year: 2016

The transformation between non-Gaussian process and Gaussian process is established by Hermite moment models. The mean upcrossing rate of non-Gaussian process can be obtained from the mean upcrossing rate of Gaussian process since the transformation is monotonic and since both non-Gaussian and Gaussian processes upcross their threshold levels respectively at the same instances. This transformation models provide a method to formulate the non-Gaussian peak factor and the extreme value of wind pressure. The Hermite models of softening, hardening and skewed processes are introduced in this paper while the monotonic limits are clarified in terms of the skewness and kurtosis. This facilitates the choosing of Hermite model and transformation order. The probability distribution of non-Gaussian peak factor is formulated and the one-to-one match is established between Gaussian and non-Gaussian peak factor. The proposed method is applied to the determination of non-Gaussian peak factor and extreme wind pressure on a flat roof. It is indicated that the mean values of calculated peak factor and extreme wind pressure match well the measured values and that the extreme values of wind pressure match better. © 2016, Nanjing Univ. of Aeronautics an Astronautics. All right reserved.


Xie Q.-F.,Xi'an University of Architecture and Technology | Xie Q.-F.,Shanghai Key Laboratory of Engineering Structure Safety | Du B.,Xi'an University of Architecture and Technology | Qian C.-Y.,China Jikan Research Institute of Engineering Investigations and Design Co. | And 3 more authors.
Gongcheng Lixue/Engineering Mechanics | Year: 2016

The existing analysis model for a common joint is not suitable for a dovetail mortise-tenon joint due to its unique construction features. The force mechanism of a dovetail mortise-tenon joint was investigated and the moment-rotation relationship was deduced according to the mechanical equilibrium and deformation coordination. A two-linear model defined with a yield point and an ultimate point was proposed based on the results of a low-cyclic reversed loading test, and the calculated method for the characteristic points are recommended. The results obtained by the calculated model agree well with the experimental results. They are usable for the protection and maintenance of ancient timber buildings. © 2016, Engineering Mechanics Press. All right reserved.


Xie Q.-F.,Xi'an University of Architecture and Technology | Du B.,Xi'an University of Architecture and Technology | Zhang F.-L.,Shaanxi Institute of Architecture Science | Zheng P.-J.,Xi'an University of Architecture and Technology | Xu Q.-F.,Shanghai Key Laboratory of Engineering Structure Safety
Gongcheng Lixue/Engineering Mechanics | Year: 2014

Based on the analysis on the force mechanism of dovetail joints, their rotational moment was analyzed and a moment-rotation calculation formula was deduced. The existed test approved that the formula is accurate and the calculated result agrees well with the test result. According to the moment-rotation calculation formula, the factors affecting the rotational stiffness of dovetail joints were analyzed. The results show that: the rotational moment and initial rotational stiffness are increased as the increase of friction coefficients; the increase amplitude of initial rotational stiffness is reduced when the friction coefficient is more than 0.5; the rotational moment and initial rotational stiffness are improved with the increase of the length and angle of a tenon; the rofational moment is improved with the increase of the height of a tenon, but the initial rotational stiffness very little. The conclusions could provide a theoretical basis for the mechanics analysis of ancient timber structure buildings. ©, 2014, Tsinghua University. All right reserved.


Shi Y.,Tianjin University | Xiong W.,Tianjin University | Li Z.-X.,Tianjin University | Xu Q.,Shanghai Key Laboratory of Engineering Structure Safety
International Journal of Impact Engineering | Year: 2016

Most casualties and injuries resulting from a terrorist attack are caused by the fragments discharging from the failure structural components or building envelope systems. Unreinforced masonry wall, which is widely constructed as structural components or building envelope worldwide, tends to break into sharp fragments under terrorist explosions, especially when explosions are in the close range. Therefore, it is of great significance to study the local damage and fragments of unreinforced masonry walls under close-in explosions. In this paper, two unreinforced masonry walls were tested under blast loads generated by 1kg and 6kg of TNT charge separately to investigate their failure mechanism and fragment characteristics. The local damage such as spalling or punching damage of the masonry wall with fragments in different sizes and splash distances were observed, and the splashed fragments were categorized and weighted. The fragment size distribution was also analyzed and it was found that the size distribution of the fine portion of the fragments followed a Weibull distribution. © 2015 Elsevier Ltd. All rights reserved.


Xie Q.,Xi'an University of Architecture and Technology | Xie Q.,Shanghai Key Laboratory of Engineering Structure Safety | Du B.,Xi'an University of Architecture and Technology | Xiang W.,Xi'an University of Architecture and Technology | And 3 more authors.
Jianzhu Jiegou Xuebao/Journal of Building Structures | Year: 2015

In order to investigate the seismic performance of the mortise-tenon joints, considering the influences of vertical load, Pubofang, sparrowbrace and size effect, the low-cycle reversed loading tests were carried out. Seven mortise-tenon joints were made as the fabrications methods of Song Dynasty. The seismic behavior and their change laws, such as failure patterns, hysteretic behavior, bearing capacity, degeneration of stiffness and energy dissipation, were compared and analyzed. The results show that the failure patterns are mainly partial evulsion of tenon and extrusion deformation of mortise and tenon, and the beams and columns are intact. The tenon slips longitudinally along the length of the column without vertical load; under the influence of Pubofang, the evulsion of the tenon is smaller and shear deformation occurs on the edge of the connection between Pubofang and Mantou mortise. As the rotation rises, the sparrow brace separates from the beam gradually. The hysteretic loops are Z type, and have obvious gathering effect. The hysteretic loops become fuller when the vertical load increases. The hysteretic loops of the joint with Pubofang is smoother and the symmetry is better, while the loops with sparrow brace shows evident asymmetry. With the increase of the vertical load, the opposite bearing capacity is higher, but the forward bearing capacity is lower. Pubofang increases the bearing capacity dramatically in both directions, while the sparrow brace only works in the forward. The rigidity of the joint with Pubofang improves greatly, but the energy dissipating capacity becomes weaker. The sparrow brace improves the energy dissipating capacity just in the primary stage. The bearing capacity and rigidity of the joints are all against the similarity relationship, and the theory basis could be provided according to the fitted formulas. ©, 2015, Science Press. All right reserved.


Huang Y.,Tongji University | Huang Y.,Shanghai Key Laboratory of Engineering Structure Safety | Xiong M.,Tongji University | Zhou H.,Shanghai Key Laboratory of Engineering Structure Safety | Zhou H.,Shanghai Jianke Engineering Consulting Co.
Engineering Geology | Year: 2015

Based on an overview of pertinent literature, the work presented in this paper focuses on the simulation of non-stationary ground motion processes and the stochastic seismic response analysis of site-specific soils. Using the random process orthogonal expansion method and the concept of random functions, initial earthquake ground motion is expressed as a random process based on only one random variable. Then, by discretizing the random acceleration process, we obtained 628 non-stationary earthquake acceleration time history samples with assigned probabilities. By comparing second-order statistical quantities of the random acceleration process between the sampled ensembles and an initial random targeting process, we demonstrate the advantages and effectiveness of this hybrid approach. The first part of this process also laid a foundation for subsequent stochastic seismic response analysis. Then, during the next part of the procedure, the calculation accuracy of the probability density evolution method (PDEM) was verified for a single-degree-of-freedom system with random excitation. The site-specific stochastic seismic response of the ground was then analyzed using the PDEM with the previously mentioned 628 acceleration time history samples. Abundant information was obtained on the probability of the ground seismic response, and the amplification effect on the target soil was verified from a random viewpoint. According to the performance-based method and PDEM, the reliability of the Shanghai soft engineering site was determined to be 0.7959. Furthermore, this new research introduces the use of PDEM techniques for modern geotechnical engineering problems. © 2015 Elsevier B.V.


Liao X.,Tongji University | Liao X.,China Construction Eighth Engineering Division Co. | Hu X.,Tongji University | Hu X.,Shanghai Key Laboratory of Engineering Structure Safety | And 3 more authors.
Jianzhu Jiegou Xuebao/Journal of Building Structures | Year: 2016

Monolithic precast prestressed concrete frame interior connection is composed of precast column, prestressed T-shaped composite beam, and cast-in-place (CIP) joint core region, where in the prestressed T-shaped composite beam is connected with fully or partially bonded post-tensioned tendons through the joint core region. An experimental study on reversed cyclic loading responses of three full-scale specimens under high axial compression ratio 0.68 in the column is presented, including two monolithic precast prestressed concrete frame interior connections with partially or fully bonded tendons, and one CIP control interior connection with partially bonded tendons. The results revealed that the damage mainly concentrated on beam end at the column face owing to flexural action, while longitudinal bars in the column and stirrups in the core region remained elastic; specimens exhibited stable and full hysteretic loops, good energy dissipation capacity and consistent stiffness degradation rule; the residual deformation of specimens was small, and specimens exhibited excellent deformation restoring capacity; compared with the CIP control specimen and the monolithic precast specimen with fully bonded tendons, the load-carrying capacity of monolithic precast specimen with partially bonded tendons was 6% and 1.5% higher, and the ductility coefficient was 11.8% and 17.6% higher, respectively. © 2016, Editorial Office of Journal of Building Structures. All right reserved.

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