Advanced Materials Research Vols. 163-167

Abstract: Plate-cone reticulated shell is a new type of double-layer reticulated shell in which ventral members is replaced by cone elements. This paper carries out nonlinear stability bearing capacity analysis on plate-cone reticulated shell considering geometrical nonlinearity of cooperating work between plates and members. In this paper, stability bearing capacity of plate-cone reticulated shells with different kinds of structure form considering geometrical nonlinearity is analyzed by using the software ANSYS, tracking complete process balance path for load-displacement by using arc-length method, the several problems of plate-cone reticulated shell are studied, such as destruction mechanism, structural ductility, stability ultimate bearing capacity and strength reserve, some important conclusions are obtained. After analyzing the stability behavior of double-layer reticulated shell by ANSYS and comparing with plate-cone reticulated shell, it is proved that plate-cone reticulated shell is more advantageous than double-layer reticulated shell in the aspect of stability bearing capacity behavior.

Abstract: The theoretical model to compute long-term stress of steel-concrete composite beam was deduced. On this basis, the effects of factors such as concrete age to loading, longitudinal reinforcement ratio in concrete slab, concrete slab width, environmental yearly average relative humidity and concrete strength on long-term stress of composite beams are discussed. The results show that additional stress at the top of concrete slab is tensile stress and that at the bottom of steel beam is compressive stress. Concrete slab width, as well as longitudinal reinforcement ratio can not be ignored. Concrete strength and concrete age to loading have relatively bigger effect as well. But environmental yearly average relative humidity has less impact.

Abstract: Steel truss coupling beam is a new type of steel coupling beam structure. To investigate seismic behavior of this coupling beam, low cyclic loading tests for four full-scale specimens of steel truss coupling beam are presented. The specimens are designed considering three factors which are T-stub steel, angle steel and material strength. The experimental data show that steel truss coupling beam has good ductility, and can consume a great quantity of earthquake energy. By enlarging the sections of cross abdominal trusses and chord members, bearing capacity and stiffness of the whole coupling beam are greatly increased.

Abstract: Based on experiments on two beam specimens (one is a concrete beam with a formwork without demoulding, another is a normal concrete beam), the basic mechanical properties of the flexural beam with a formwork without demoulding, in the condition of monotonic loads were studied, including failure patterns, normal section bearing capacities, change rules of deflections, concrete strain of midspan, strain of strengthened reinforcing steer and so on. The comparison of bearing capacity is also made between a concrete beam with a formwork without demoulding and an ordinary concrete beam. The results indicate that by calculating bend-bearing capacity in current code, a beam with a formwork without demoulding is as safe as an ordinary concrete beam, a concrete beam with a formwork without demoulding meets the requirements of deflection limit value. Its bend-bearing capacity is approximate to an ordinary concrete beam.

Abstract: Axial compression experiments of eighteen concrete-filled GFRP tube (CFFT) and concrete-filled GFRP reinforced steel tube (CFFST) specimens in total have been carried out to study their mechanical behaviors. Experimental results show that, GFRP tubes with different filament-wound angles could enhance the strength and ductility of core concrete at different levels. Fibers with hoop directions provide the best confinement and enhance the ultimate strength up to 266% comparing with unconfined concrete columns. Fibers with ±45° winding angles have minor effects on bearing capacity, but greatly improve the ductility of concrete columns. Compared with CFST columns, GFRP reinforced CFST columns with hoop direction fibers increase the bearing capacity of 35.0%, and the fibers along 45° winding angles could enhance by 17.5%. The mechanical behavior and the failure modes of the six experimental group specimens are also discussed in this paper.

Abstract: For mechanical behaviors of composite frame and reinforced concrete core hybrid Structures in high-rise buildings, the three-dimension finite element models were established, modal analysis and elastic time-history analysis were finished, the cooperative work mechanism between frame and core was researched, the dynamic characteristics and seismic response of the hybrid structures under different connection type were studied. the results indicate that the stiffness characteristic of the hybrid structures should be taken between 1 to 2 so that two sub-structure can reasonably afford the internal force, the connection between frame and core bring differences in mode shape and natural vibration periods, the natural vibration periods of hinged model are greater than periods of rigid model, the mode shapes with mainly floor vibration are more likely to appear in hinged model, the connection would lead to significant changes in the deformation and distribution of inner force, the axial force of frame columns would significantly increase for the rigid connection, the shear and bending moment of frame columns would increase for the hinged connection, it was proposed that the hybrid structures should be separately analyzed with hinge model and rigid model for ensuring the frame columns have sufficient capacity of the shearing and bending both.

Abstract: Considering the confining mechanism in circular concrete-filled steel tubular (CFST) columns, a volume-based method for dividing the effectively and ineffectively confined area of concrete core and calculating the value of effectively confined coefficient is presented. The constitutive relationship of concrete core is developed by means of modifying the expressions of effective lateral pressure and the descending stage in Mander’s confined concrete model. Numerical simulation of several circular CFST columns under axial load is carried out in ABAQUS. The comparisons between calculated results and experimental results demonstrate that the suggested concrete constitutive relationship is appropriate for the nonlinear analysis of circular CFST columns.

Abstract: The cable-stayed suspension bridge is a novel composite structure with great overall stiffness and the capacity to span a long distance, which has been proposed for the design of some extra long-span bridges. To take further research on mechanical properties and behavior of this type of structure, the proposed preliminary design of a cable-stayed suspension bridge with a main span of 1800m is analyzed. The three-dimensional nonlinear analysis method is used to investigate systematically the influence of various principal structural parameters on the static and dynamic behavior of bridges. These parameters include the rise-span ratio, the suspension-to-span ratio, the constraint condition of the stiffened girder, the number of auxiliary piers at side spans, the layout of suspension cables, and the elastic modulus of suspension cables. Meanwhile, the selection of the rational values of these parameters is discussed.

Abstract: Mega steel braced frame-composite steel plate shear wall structure, consisting of mega steel braced frame as outer frame and composite steel plate shear walls as core wall, is a new type of hybrid structure that is proposed in this study. Seismic performance of this new structure was analyzed under frequent earthquake and severe earthquake. The analysis focused mainly on displacement response, seismic base shear distribution and failure mechanism. Comparing with traditional steel frame-RC core wall structure, this new type of hybrid structure presents better coorporative working performance since mega steel braced frame provides larger stiffness and composite steel plate shear wall provides a fairly ductile response. It can be observed from the failure mechanism that this structure has multiple seismic resistant systems with composite steel plate shear wall, mega braces and mega frame when subjected to severe earthquakes.

Abstract: This paper, combined the characteristics of steel structure and timber structure, conceives a new system of residential structures—staggered truss steel-timber combined structure, carries out structural arrangement and optimization design on a six-layer residence, and makes a study on its seismic performance under rare earthquake. The author uses commercial structural analysis softwareto establish a basic model, conducts pushover analysis, draws the load-displacement curve, then getsthe capacity spectrum of the model, next compares with the demand spectrum under 8 degrees (0.3g)rare earthquake, finally gets the performance point of the structure. The results show that the inter-story displacement angles can meet the limit of seismic code. Meanwhile auther analyzes the distribution and the appearance sequence of plastic hinges, plastic hinges mainly occur in the truss webs, the chords and the frame beams in succession, and the number of plastic hinges is more. Bottom columns finally appear plastic hinges. These phenomena meet the design requirement—strong column-weak beam.Finally this paper gets a conclusion that staggered truss steel-timber combined structure shows good seismic capacity.