Advanced Materials Research Vols. 671-674

Abstract: A high-rise steel structure which has been used for 21 years and has horizontally single-span structure, hinged nodes of columns-beams and removed column bracings was added four stories directly and evaluated the aseismic performance. Analysis shows that as a complicated system engineering, reinforcement scheme selection should take feasibility, safety and economy into account. In the meanwhile, anti-seismic standards and later working life should be reasonably determined in order to achieve the goal which not only uses previous structure but also saves the cost. Improper use of existing building will increase irregular degree of structure which will increase the destructive effect of earthquake. In order to ensure the overall performance of reinforced structures, taking reasonable reinforcement scheme and feasible construction technique are necessary.

Abstract: The width-thickness ratio of high-frequency welded H-section steel beam overruns the limit of the current specification, which is bound to affect the overall stability of the structure. Based on the finite element analysis, in the working conditions of being under the pure bending and crosswise distribution load, the overall stability factors of high-frequency welded H-section steel beams were studied, and several factors with some different sections were listed, which could give some advices for the engineering designers. The results show that, the overall stability factors calculated by using the formula of code and the finite element method are very close, but the former is slightly higher than the latter. The overall stability factors could be directly calculated by using the formula of code which in the crosswise distribution load-condition, but the value should be timed reduction coefficient which is less than 1 in pure bending load-condition.

Abstract: The shear-lag effect of steel box-girder is qualitatively analyzed by using the finite element software ANSYS. Various methods to reduce the shear-lag effect are studied, and the most effective method is changing the web layout and increasing the number of box-room among them. The suggested value of effective width to thickness ratio b1/t1 of the flange without considering the shear-lag effect are obtained in this paper.

Abstract: This study case comes from a large-scale comprehensive gymnasium that is under construction. It is a frame structure, and the total height is 23.5m, and the main beam in 2nd and 4th floor are post-tensioned bonded pre-stressed concrete structure with a longs span to 27m. As the thickness and the ration of steel bars of the bottom slab could not bear the load caused by construction and besides, before the terminal tension, the bracing to support the template could not be demolished to turnover; so, the plan that needs to tense from the upper floor to lower floor recurrently has not been adopted. Another construction process that proposes to tense the beams in one floor as soon as they are casted .However, Due to construction time limit and cost, this plan was not carried out. At last, we combining the two plans. In our plan, pre-stress tension and building construction were carried out simultaneously. According to accurate analysis of construction propose and flow, with careful check on main components, security, economics and building functions are uniformed together optimally.

Abstract: The key to the making is the arrangement of prestressed reinforceds. According that a hyperbolic paraboloid is a ruled surface and the methods of spatial analytic geometry and vector algebra, obtain the distributed model of prestressed reinforceds in two situations: one is that the reinforceds are imagined as one-dimensional straight lines; the other is the reinforceds prestressed are cylindrical steel pipes whose diameters are needed to be considered. In the second case, by applying the feature that the central axis of the reinforceds have no intersections when they are arranged, establishing the center straight generatrix model based on the coordinate translation, the position of center straight generatrix for each reinforced is solved. Thus, the mathematical model provides a concise reasonable operational guidance for workers’ construction.

Abstract: In order to discuss the failure mechanism of concrete filled steel tube lattice wind generator tower joints. Based on the parameters of web member section form, and using nonlinear static numerical simulation, this dissertation research on the stressed complex joints. The results of the study show that the abdominal rod for circular steel tubes joint (JD1) is instability failure which is led to the local buckling of compressive bar; the abdominal rod for single angle steel (JD2) or double angle steel (JD3) joint is instability failure because of the local buckling of the joint board. Under the web members and joint boards all fitting their own capacity requirements, JD1 is very easy to make draw bar broken on both sides of the pillar tube wall region, JD2 and JD3 are apt to damage on the weak positions of joint board ends and pillar tube wall joint. In the three forms of web member joints, the best ultimate bearing capacity is JD1 , JD3 is the second and JD2 is minimum.

Abstract: The yield surface of section axial force and bending moment (AFBM) is formulated by section assemblage concept. Based on flexibility method , a novel planar beam- column element is proposed using yield surface of section AFBM. Dynamic elastoplastic analysis is carried out on a planar steel frame. The results show that the accuracy of proposed model is close to fiber model, and hence it can be used for dynamic elastoplastic analysis of frame structures.

Abstract: In frame structure, the Supports of secondary beam are frame beams or main beams, Support Beam rotation of the secondary beam to form certain constraints. General calculation method, for edge Supports, sometimes as fixed or hinged, the so-called “method of taking no account of torsion rigid”. In such cases, intermediate supports are usually as hinged, obviously not reasonable. We consider the torsional characteristics of all supports, according to torsional stiffness of the beam support. Therefore, we can become the continuous beam mode into the frame mode, so as to simplify the calculation, analyzed the influence of the torque, and should pay attention to the problem.

Abstract: Taking a transfer beam of high-rise building in the actual engineering as an example, nonlinear numerical analysis on transfer beam structure,which is several complex stress situation about eccentric and different sizes of eccentricity of the upper short limb shear wall , is carried by the finite element software ANSYS, its stress performance and deformation characteristics are studied. Analysis results show that: (1)impact of eccentricity of the upper short limb shear wall on stress performance of transfer beam is very big, which is more unfavorable than that of no eccentric. Eccentric made structure be under stress state of bending, shear, torsion. (2)The eccentricity increased more significant effect on the displacement of transfer beam, and bigger effect on reliability under normal conditions. (3)Both from view of the design point, or from view of the economic point, the wall eccentric action in transfer beam should be avoided as far as possible to meet the construction requirements.

Abstract: New high performance steel HSB800 have been developed in South Korea, the yield strength of which is equal to 690MPa. High strength steels typically show a lower ductility and a larger yield ratio than conventional steels. Since the inelastic design procedure of current AASHTO specifications is not permitted to the flanges and webs of nominal yield stress exceeding 485 MPa, this study is intended to present an assessment result of the compactness requirements for I-section girders by performing 3D nonlinear finite element analyses. On the hypothetical specimens designed to be compact-section girders, the numerical analysis was performed using the finite element code ABAQUS. From the analysis results, it is found that the compact section limits speculated in the 2007 AASHTO LRFD could be applicable to the design of HSB800 steel I-girders to reach the plastic moment. However, the inelastic design procedure does not surely confirm a sufficient flexural ductility. More extensive studies of HSB800 I-girders are still in need.