Yi T.-H.,Dalian University of Technology |
Li H.-N.,Dalian University of Technology |
Zhao X.-Y.,Shanghai Municipal Engineering Design Institute group Co.
Sensors (Switzerland) | Year: 2012
In structural vibration tests, one of the main factors which disturb the reliability and accuracy of the results are the noise signals encountered. To overcome this deficiency, this paper presents a discrete wavelet transform (DWT) approach to denoise the measured signals. The denoising performance of DWT is discussed by several processing parameters, including the type of wavelet, decomposition level, thresholding method, and threshold selection rules. To overcome the disadvantages of the traditional hard- and soft-thresholding methods, an improved thresholding technique called the sigmoid function-based thresholding scheme is presented. The procedure is validated by using four benchmarks signals with three degrees of degradation as well as a real measured signal obtained from a three-story reinforced concrete scale model shaking table experiment. The performance of the proposed method is evaluated by computing the signal-to-noise ratio (SNR) and the root-mean-square error (RMSE) after denoising. Results reveal that the proposed method offers superior performance than the traditional methods no matter whether the signals have heavy or light noises embedded. © 2012 by the authors; licensee MDPI, Basel, Switzerland.
Chen L.,Tongji University |
Chen L.,Shanghai Municipal Engineering Design Institute Group Co. |
Shao C.-Y.,Shanghai Municipal Engineering Design Institute Group Co.
Bridge Construction | Year: 2015
To study the mechanism and time-dependant chrematistics of influences of the concrete shrinkage and creep on the composite girder cable-stayed bridge, the Second Zhangshu Ganjiang River Bridge (a semi-floating system composite girder cable-stayed bridge with double pylons, double cable planes and with a main span of 400 m) was taken as an example and was analyzed. The bridge professional software RM2006 was used to build up the finite element model for the whole bridge of the bridge, the time-dependant influential mechanism of the bridge, time-dependant influential factors of the different components of the bridge in operation period and the time-dependant responses of the different structural systems were studied. The results of the study show that the for the composite girder cable-stayed bridge, the initial axial strain in the cross section of the main girder caused by the concrete shrinkage and creep of the deck slabs is the main cause leading to the midspan deflection of the central span of the main girder and to the relaxation of the stay cables at the side spans. The initial flexural strain in the cross section of the main girder caused by the shrinkage and creep is the main cause leading to the negative moment occurrence in the main girder. The concrete shrinkage of the deck slabs and the concrete creep of the slabs under dead load are the main factors causing the relaxation of the stay cables at the side spans and the midspan deflection of the central span. The concrete shrinkage and creep of the pylons cause the relaxation of the stay cables nearby the pylons and cause the main girder to produce the local negative moment peak values. The arrangement of the vertical bearings at the pylons and the arrangement of the auxiliary piers may cause certain adverse influence to the time-dependant effect of the composite girder bridge. As judged from the above-mentioned, it is considered that the full floating system is more reasonable than other systems. ©, 2015, Wuhan Bridge Research Institute. All right reserved.
Li G.,Tongji University |
Zhang C.,Tongji University |
Niu C.,Shanghai Municipal Engineering Design Institute Group Co.
Journal of Bridge Engineering | Year: 2013
Abstract External prestressing technology has achieved wide application in bridges. Although previous tests have made great progress in shear behavior of externally prestressed concrete beams, the research mainly focused on simply supported beams. To study the effects of joints and large negative moments on the shear behavior of segmental externally prestressed concrete continuous beams, a series of cantilever beam specimens were designed to simulate the negative moment regions in continuous beams. Then, the crack developing behavior, failure mode behavior, and mechanical behavior of specimens with different shear span to effective depth ratios, joint types, joint locations, and ratios of internal to external tendons were investigated in this experimental study. The test results show that failure cracks of segmental specimens are web shear cracks, whose locations and inclination angles are independent of joints. Eventually, both sides of the specimens move relatively along failure cracks and the specimens fail suddenly. The results also reveal that the deflections of segmental specimens after cracking develop very quickly, and the stress increments of prestressing tendons reach 20-24% of the tensile strength, which are larger than those of monolithic specimens. In addition, the shear strength provided by the concrete effects in regions near the interior supports of continuous beams is lower than that in regions near the supports of simply supported beams, and the contributions of the stirrup and prestressing tendon to the shear strength are 14-21 and 8-18%, respectively, in which the contribution of stirrup is greater than that of simply supported beams. © 2013 American Society of Civil Engineers.
Huang M.,Shanghai Municipal Engineering Design Institute Group Co. |
Huang M.,Tongji University |
Huang W.,Tongji University
Construction and Building Materials | Year: 2016
Modified asphalt concretes have been used in pavement widely now. Their fatigue life, which can be increased by healing effect, is one of the most important factors in mixture design, however, it is considered less in mixture design. The test in the study involves fatigue tests of 9 modified asphalt mixtures, together with two base asphalt mixtures. Fatigue performances were compared (or graded) through several four-point bending beam fatigue tests, under the same asphalt content (5%), volume design target, and high-temperature performance grading, which are the most common occurrence 3 situations in mixture design process, the results can be a guidance for selection of asphalt in engineering application. Results also demonstrates that crumb rubber and styrene-butadiene-styrene modified asphalt mixtures performed good healing effects. And a partition scatterplot based on the test results was plotted, which provides a modified asphalt mixture design guide. © 2016 Elsevier Ltd. All rights reserved.
Li F.-D.,Shanghai Municipal Engineering Design Institute Group Co.
Bridge Construction | Year: 2016
To study the characteristics of the separated and obliquely set steel anchor boxes in pylon of cable-stayed bridge, the structural characteristics of the anchor boxes and the force conditions of the anchorage zone in the pylon were analyzed. Because the anchor boxes were separated and obliquely set, the transverse horizontal component force could not be self-balanced and in comparison to the rigidity of the anchor boxes, the rigidity of the concrete pylon columns increased and at the same time, the pylon columns bore the whole of the transverse horizontal force and much of the longitudinal horizontal force. By way of example of the diamond-shape pylon of a single-pylon cable-stayed bridge, the software ANSYS was used to establish the spatial finite element model for the anchor boxes in the pylon, the influences of the obliquely setting of the anchor boxes on the stress distribution of the anchor boxes and pylon walls as well as the ratios of the horizontal force distribution of the stay cables between the anchor boxes and pylon walls were analyzed. The results of the analysis show that as compared to the integral steel anchor box, the ratios of the horizontal force distribution of the stay cables of the separated and obliquely set steel anchor boxes decrease and the pylon columns bear much of the horizontal component force. The force conditions of the components and shear studs of the anchor boxes are not symmetric, the stress levels are low and are not uniform. © 2016, Wuhan Bridge Research Institute. All right reserved.
Wang H.,Shanghai Municipal Engineering Design Institute Group Co.
Yantu Lixue/Rock and Soil Mechanics | Year: 2012
Using numerical simulation by PFC 2D (particle flow code in two dimensions), the group piles effect of pile tip resistance of under-reamed piles on uplift loading is studied. The increase of tip resistance with uplift displacement and the variations of soil displacement around pile tip are observed in the simulation. The differences between single pile (pier) and group piles (piers) in uplift loading are shown and the development of tip resistance with uplift displacement for group piers in different spaces is compared. It is shown that the uplift characteristics are similar for single pile (pier) and group piles (piers) when the normalized uplift displacement s/D is smaller than 0.1. With the development of uplift displacement, the tip resistance of single pile (pier) is larger than that in group piles (piers) and the interaction of soil particles around tip emerges. When the normalized uplift displacement s/D is smaller than 0.5, the tip resistance of central pile (pier) is larger than that of side pile (pier) in the group piles (piers). When the normalized uplift displacement s/D is larger than 0.5, the tip resistance of side pile is larger than that of center pile in the group piles and that is reverse in the group piers, which embodied the effects of side restriction of pile shaft on the mobilization of tip resistance. The characteristics of group piers had obvious difference with single pier only in larger displacement with the increase of pier distance.
Bai J.,Shanghai Municipal Engineering Design Institute Group Co.
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2015
Besides the static loading of the workshop and crane beams, the cyclic loading brought about by the crane operation was applied to the pile foundation of a heavy lifting workshop. The cyclic loading has two characteristics. One is the high proportion of the cyclic loading to the total, and the other is its rather high frequency. In this study, the operation of the crane in a lifting workshop of a shipbuilding base in Shanghai was recorded and analyzed through artificial records. A statistical method suitable for analysing the crane operation rules of the shipbuilding base was established. Besides, the triangular wave was assured to be suitable for fitting the cyclic loading waveform for the crane. Furthermore, a simplified analytical method was established based on the normative crane working system level. The calculation results validate the reliability of the measured data. ©, 2015, Chinese Vibration Engineering Society. All right reserved.
Li Y.,Shanghai Municipal Engineering Design Institute Group Co.
Zhongguo Gonglu Xuebao/China Journal of Highway and Transport | Year: 2015
In order to further analyze the proper design parameters for cable clips of suspension bridges with carbon fiber reinforced polymer (CFRP) cables, the Tsai-Hill failure criterion of composite material was firstly introduced, and the formulas for cable moment at the clips was derived through analysis method, based on which calculation method for the clip design of CFRP suspension bridges was proposed. Then, parametric analysis on the mechanical indexes of clips on the CFRP cable was conducted, where the influences of diameter of cable wire, interval between clips, length of clips, tension of bolts, interval between bolts, friction factor between CFRP and steel, and friction factor of CFRP on force performance of cable clip were investigated. The results show that the mechanics behavior of clips can be improved significantly by reducing the cable wire diameter, increasing the clip length, increasing the tension of bolts, reducing the interval between bolts, and enhancing the friction factor between CFRP and steel. The interval between clips should be chosen within a reasonable range, otherwise negative effects could be brought about. ©, 2015, Xi'an Highway University. All right reserved.
Li Y.,Shanghai Municipal Engineering Design Institute Group Co.
Chongqing Daxue Xuebao/Journal of Chongqing University | Year: 2012
This paper proposes an analysis method for the static mechanics of suspension bridges based on segmental catenary and FEM software. A comparative research on mechanics of suspension bridge with a span of 2000~5000 m is conducted according to the proposed method, and CFRP suspension bridges are proved advantageous and practicable. A parametric study for the deflection performance of 2000 m CFRP suspension bridge is executed in order to enhance its stiffness, where the span arrangement, rise to span ratio, side to main span ratio, inertia of girder and tower, and the central buckle are considered, respectively. A serials of design suggestions for improving the structural stiffness are proposed.
Lin F.,Shanghai Municipal Engineering Design Institute Group Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2014
The increase of embedded depth of retaining wall, reinforcement of foundation soil and set-up of partition wall between foundation pits and buildings are widely-used techniques to protect the surrounding facilities. The problems of budget and construction period can be possibly reduced by optimization design. Currently, the optimization design of the foundation pits focuses mainly on types of retaining wall and structural members and not on the whole retaining system. Based on a deep foundation pit close to a metro station in operation and a large-diameter water pipe, a 3D finite element model is proposed. The behaviors of soils are assumed to conform to Drucker-Prager model, and three different construction sequences are simulated. Considering the distinct stress states of soils during construction, loading and unloading modulis of each soil type are adopted. The results show that the implementation of the temporary partition wall can be canceled, and the basement floor No.1 and No.2 can be excavated downward simultaneously. The design of retaining system is optimized, and the settlement-sensitive municipal facilities are safe.