Applied Mechanics and Materials Vols. 578-579

Abstract: Based on the time-history analysis principle of bidirectional equivalent tension rod of steel shear wall in this paper, the theory of Incremental Dynamic Analysis (IDA) is used to investigate the real seismic behavior of steel frame-steel plate shear wall (SPSW) system under a large number of natural earthquake waves and artificial simulated earthquake waves with the gradually increased scale of seismic intensity in order to achieve the base shear-roof displacement (V-Δ) curve under each earthquake wave action. Based on the principle of unidirectional equivalent tension rod, the pushover analysis is also used to obtain the curve of base shear and roof displacement under two different loading modes of uniform distribution and inverted triangular distribution. Through the above two different methods of seismic behavior evaluation, the achieved conclusions are as follows: The most V-Δ envelope curves obtained by IDA analysis are between V-Δ envelope curves obtained by pushover analysis under these two loading modes of inverted triangular and uniform distribution. With the increase of structural storey, the effect of high order mode on seismic behavior is more and more obvious and the deviation of calculation results derived from pushover is bigger and bigger. As a result, pushover analysis is only applied to evaluate seismic performance of structure at the middle or low storey. For the pushover, the structural bearing capacity and initial stiffness is underestimated, but the structural deformation capacity is overestimated under inverted triangular loading mode, Whereas, it is the opposite situation under the uniform distribution.

Abstract: Vertical bearing capacity experiments were conducted with circular double-layer stirrup confined concrete columns as study objects, data acquisition was carried out using acoustic emission (AE) equipment and the AE parameters and graphs acquired during the experiments were analyzed to obtain the damage evolution of steel reinforced concrete columns under compression. The correlation between fractal dimension of AE graphs and curve was studied using the fractal theory, and the results show that the AE parameter graphs have fractal characteristics and the box dimension of each AE parameter graph constantly increases with the increase in stress, with a positive correlation exhibited between the fractal dimension and stress level. The loss variable expressed with fractal dimension was defined to establish actual equivalent stresses and the equivalent stress curves and experimental curves were compared; the results show that the fractal dimension of acoustic emission parameter graph can characterize the damage laws of the concrete member.

Abstract: In order to carry on the progressive collapse analysis more properly, nonlinear-dynamic analysis method is used to analyze five-storey of steel frame structure. Four structure schemes have been established, namely frames, frames with horizontal braces, frames with vertical braces and frames with horizontal cross braces. According to analyzing with different position of failure column on the first floor, the curves of displacement-time of column failure point and axial force of failure column’s neighboring are obtained. The results indicate that horizontal braces can reduce the vertical displacement above damaged column and the axial force of the columns on the first floor evidently. The vertical displacement of horizontal cross braces is less than which of horizontal braces.

Abstract: The research involved experimental testing of simple steel connections and components (structural 8.8 bolts) at elevated temperatures. High temperature tests on structural bolts demonstrated two modes of failure at elevated temperatures: bolt breakage and thread stripping. In order to prevent the thread stripping in a connection,the manufacturing process of bolts and nuts has been investigated and the ‘over tapping’ of nut threads to accommodate the (zinc) coating layer for corrosion resistance has been indentified as a primary reason resulting in this premature failure between bolts and nuts. Experimental tests on endplate connections revealed the ductility of these connections to decrease at high temperatures, which might hinder the development of catenary actions in fire if plastic hinges are attempted to be formed within the connection zones. Component-based modelling and finite element simulation have been utilized for investigation of the performance of these connections.

Abstract: The Latticed Intersected Cylindrical Shell (LICS) is a new type of spatial structure. In order to investigate the mechanical properties of LICS, an octagonal structural model, valley style, was designed and constructed. The model experiment under full-span loading was carried out. By comparing the experimental results with theoretical analysis, the LICS is proved to exhibit well mechanical performance. Valley members get high stresses, especially the members near bearings. It is proved that internal forces transmit to the bearings through the valley members.

Abstract: The mechanical behavior of joints on lattice wind turbine tower of concrete-filled steel tubular(CFST) is very complex, the safety and reliability of joints is very important for the whole structure. To better understand the mechanical properties of the joints, we design a static loading test of 3 KT-type CFST joints. According to the test, we make analysis about the failure progress, equivalent stress of joint intersection and the relation of load-defomation. The results showed that due to the presence of concrete, the failure mode of CFST joints is web members failed. The failure characteristic of overlap joints is the instability of compression web member while the gap joints are the weld tear of tensile web member. With the increase of the overlap ratio, the distribution of the equivalent stress is more uniform. The high stress area is in the gap and the tower wall which between the crown point and saddle point in tensile side.

Abstract: A thorough analysis of slender columns under axial force and bending moment requires second order effects assessment. Concrete’s creep is one of the factors that increase lateral displacements of the bar in the long run. This phenomenon propitiates the instability and reduces its bearing capacity. This paper shows a procedure for assessing rheological effects based on Eurocode 2 method. This procedure will be added to structural analysis software which takes into consideration geometrical and mechanical non-linearity. As an example interaction diagrams for concrete-encased composite columns with different slenderness values are obtained. These diagrams will demonstrate that rheological effects have a greater influence as axial force eccentricity and slenderness values increase.

Abstract: Effect of loading rate on bond property between corroded concrete and steel bar are studied. Simulation test and finite element are used to study the pull-out test of corroded reinforcement concrete members in present literature. Considering the corrosion of steel bar and concrete and their rate dependent characteristics, the bond property of corroded reinforcement and concrete under the different loading rate (10^-4 s^-1-10^-2 s^-1) are studied. It concluded that the bond property was improved when the rating rate form 10^-4 s^-1 to the static load; the bond property would decreased when the loading rate reached the fixed value (10^-3s^-1-10^-2s^-1), the members was failed under the smaller load.

Abstract: A dynamic calculation model of the pile supporting structure with single prestressed anchor for the slope is proposed in this paper. The motion equation of the pile-prestressed anchor is established and the analytical solutions are obtained. In addition the proposed method is applied to a project case to carry out the seismic analysis and design of the pile supporting structure with single prestressed anchor. The calculation model provides a new approach for earthquake analysis and seismic design of slope supported by pile supporting structure with pre-stress anchor.

Abstract: An improved component-based model has been developed which includes nonductile(brittle) components (bolts and welds) into a connection model with a reasonable assumption of their failure displacements, based on experimental tests.This model was created for a flexible end-plate connection, using the ABAQUS finite element code, in order to investigate its resistance and ductility at ambient and elevated temperatures. In the subsequent analyses, steel beams and columns are going to be simulated as finite shell/beam elements and the connection behaviour is to be represented by the simplified models. This sub-frame model will also be used for parametric studies to investigate restrained beam behaviour under fire attacks with particular emphasis on the role of the connections.