Abstract: The fatigue life of crane steel structure will inevitably decrease in the course of work, which directly affects the work of crane. So the correct fatigue life evaluation is necessary. Based on crack propagation theory, a framework of assessing remaining fatigue life of crane metal structures is built in this paper. Moreover, in order to descript the analysis process, an example about fatigue life estimation of a shipbuilding gantry crane whose maximum hoist 100 ton was shown. During assessment of remaining fatigue life of aged crane structure, some important indexes were inspected such as corrosion，strength and defection in focused weld joints, besides of finite element simulation of structure. The results can also be used to evaluate the whole metal structure of this crane.
Abstract: The article presents the method of research, introduces the relative theory, researches the force statement of prestressed concrete cable-beam structure system by the method of model test. The results of test and theory is consistent. Prestressed concrete cable-beam structure systems has lots of advantages than ordinary reinforced concrete, such as high bearing capability, less cost, less weight, the longer span and shorter construction period. It is easy to put into practice and has significant prospect.
Abstract: Mid-story isolation structure is developing from base isolation structures. As a complex structural system, the work mechanism of base isolation structure is not entirely appropriate for mid-story isolation structure, and the prolonging of structural natural period may not be able to decrease the seismic response of substructure and superstructure simultaneously. In this paper, for a four-story steel frame model, whose prototype first natural period is about 1s without seismic isolation design, the seismic responses and isolation effectiveness of mid-story isolation system with linear natural rubber bearing and viscous damper are studied experimentally by changing the location of isolation layer. Respectively, the locations of isolation layer are set at bottom of the first story, top of the first story, top of the second story and top of the third story. The results show that mid-story isolation can reduce seismic response in general, and substructure acceleration may be amplified.
Abstract: With the continuous development of dam construction technology, the RCC dam becomes one of the most popular types of dam in the world with its unique advantages. Temperature control measures research is one of the key issues of design and construction of mass concrete structures. How to choose the proper temperature control measures to prevent concrete cracks becomes the important problem of dam construction technology. In a RCC gravity dam, the climate environment is so severe that a single temperature control measure can’t meet the requirements of temperature control and crack prevention. In this paper, 3D FEM simulation analysis is used to calculate temperature field and thermal creep stress field during the whole construction process. According to the simulation results, the temperature control measures design of the dam has been comprehensively evaluated and the temperature control measures of this project have been put forward.
Abstract: As a smart material, the study of shape memory alloy in civil engineering mainly in the self-monitoring and self-repairing of concrete beams, earthquake resistance and reinforcement of concrete columns, seismic damping of concrete structures, etc. The development of shape memory alloy and its main features are outlined; research progress of the shape memory effect and superelasticity of shape memory alloys in smart concrete application are introduced; the factors which affect the development of smart concrete structure and the development direction are pointed out.
Abstract: Downbursts are recognized as a significant threat to safety of transmission towers. The difference between downburst and boundary layer wind profiles will lead to different failure modes and regions of damage of a transmission tower. To account for differences of wind profiles and failure modes, the different design wind loads are proposed, and a novel analytical framework is formulated for checking the section wind-resistance capability. The framework is useful for checking strength of transmission towers under downbursts. It has been found that the peak values of section moments exceed the ultimate section moment capability at about a third of the tower height under downbursts, while failure occurs in the bottom panel of tower under boundary layer winds. The results are consistent with the fact that regions of damage for most collapsed high-rise transmission towers under downbursts were indeed in lower-middle height of tower.
Abstract: In the system of preventing progressive collapse, the joints always play a key role in catenary action and alternate load path while the joints are usually under the combination of bending moment and tensional force. In this combination, high rotation capacity and good resistance of joints are demanded. In this paper, a new type of semi-rigid joint used in the structures with concrete-filled square steel tube (CFST) columns is proposed and developed by ABAQUS. The new type joint is suitable for the classification for semi-rigid connection; The bending moment resistance of the joint decreases linearly with the increase of tensional force; reducing pretension force reasonably is beneficial for the tensional force to develop “catenary action”; the width of short leg of angle would influence the moment resistance of the joint evidently; the initial rotation stiffness is not affected by width of leg dramatically.
Abstract: In order to study the evolved characteristic of sandy coast in Hebei Province, the paper analyzed costal information by Remote Sensing technology from landform maps and remote sensing images from 1956 to 2007. It studied the evolvement characteristics and the reasons of sandy coast deeply. And it also analyzed the evolvement infections to the nearby coast of the sandy engineering. The results showed that the characteristic was erosion condition in sandy coast. There were several different evolved processing in different area from 1959 to 2007. In the region between Daihe River and Tazigou, the highest erosion speed was 3.45 m/a by the coastal current and wave between Daihe River and Yanghe River. The section was deposited into the ocean with the speed of 1.29 m/a by the cultivation ponds building in Bohai Sea farmland between the Yanghe River and Dapuhe River. In the region between Tazigou and Langwokou River, the beach had been eroded about 373 m with the speed of 13.32 m/a by 2007. And the section was eroded offshore more serious with the distance of 610 m and the speed of 21.79 m/a from the north of Luanhe River.In the region between Langwokou River and Daqinghe River, the average erosion distance was about 370 m with the speed of 13.21 m/a in Shegang sandbar. And it was eroded back to mainland about 164 m with the speed of 8.20 m/a. And it was about 504m with the speed of 18.00 m/a.
Abstract: The differences of empirical formulas of China, the United States, Japan, and Europe for estimating the fundamental periods of frame structures are investigated. Summing up paradigms of the empirical formulas from the above representation countries, the paradigm formulas expressed as single-variable exponential type, single-variable linear type, and multi-variable non-linear type. Using statistical data of 36 groups of the measured fundamental period for least-squares regression analysis, and the effect of fitting regression formula is judged by the norm of relative error ‖δ‖2, the norm of root mean square error ‖RMSE‖2, the norm of residual mass‖CRM‖2. The results show that: the single-variable exponential type has wide application and gets closer with measured fundamental period; the single-variable linear type is brief, and the single-variable based on structural height has a smaller error with measured fundamental period, the single-variable based on the stories of structures has a larger error with measured fundamental period; the multi-variable non-linear type is very complex and larger error compared with the measured fundamental period. Considering the formula in the form of simple, practical and consistent with the codes, this paper gives single-variable exponential type as recommended empirical formula for estimating the fundamental periods of frame structures .The proposed empirical formula can serve as a reference for revision of the seismic design code, frame structure seismic design and related studies.
Abstract: Based on the three-dimensional finite element method (3D FEM), an electro-mechanical impedance (EMI) model is established for a cracked portal frame. In this analysis, the effect of the interfacial properties between the piezoelectric patches and the host structure on the EMI signatures is considered and thus a coupled structural system consisting of PZT patches, bonding layer and host structure is then investigated. Comparison with numerical results by other methods is made to validate the effectivity and accuracy of the proposed EMI model. The effects of various parameters including the material properties of the adhesive, the crack depth and the crack position etc. on the EMI signatures are highlighted. Numerical results indicate that the present model can be employed for structural damage detection.