Feng Fan

Direct Estimation of Critical Load for Single-Layer Reticulated Domes with Semi-Rigid Joints

Numerical model of a bolt-ball joint system is established using software ANSYS and verified through experiments. Based on the bendingrotation curves of the bolt-ball joints obtained through numerical simulation, a finite element model of single-layer reticulated domes with bolt-ball joint system is established using nonlinear beam element with end spring elements in software ANSYS. The analyses of the domes are carried out with different parameters including bending stiffness, ratio of rise to span, rotation-stiffness, ball size, asymmetric load distribution, tube section, support condition and initial imperfection. Several key parameters having influence on the load carrying capacity of a semi-rigidly jointed single-layer reticulated dome are thus identified. Finally, formulas are established for direct estimation of critical loads of semi-rigidly jointed single-layer reticulated domes under symmetric and asymmetric loading conditions.

Test on the Suspended Dome Structure and Joints of Dalian Gymnasium

The roof of Dalian Gymnasium, of span 145.4 m ∞ 116 m, rise span ratio 1/10, truss height 2.4 m and strut height 10.0 m, is the largest suspended dome structure in Asia. Different tension schemes have an important effect on the performance of a structure. It is necessary to investigate the characteristics and feasibility of different tension schemes. In addition, to check the accuracy of the numerical model and its calculated results and to investigate the mechanical performance when subjected to construction and design loads, as well as safety considerations during construction and when in service, a scale model of the suspended dome with scaling factor 1:10 was constructed and models of some key joints at full scale. The results show that the theoretical strut internal forces and displacements of joints, are in good agreement with test results. Therefore, tension steps in the cable can be controlled by internal forces in the struts. The lifting of struts is a continuous process of adjustment. The size of the cable needed to be accurate during the test, which indicates that the controllability of this method is relatively difficult. However, when tensioning diagonal cables, the diagonal cable force can be an effective control because these is a sufficient number of controllable tension points and a relatively small cable force. More importantly, because the geometrical dome forming accuracy of this method is higher, the latter method is suggested for use during construction. The displacements of the joints in the upper reticulated shell of the suspended dome, the axial forces in the struts and the stresses in the members present, vary linearly with test load which indicates that the vertical stiffness of the overall structure is well maintained when conducting static tests on the model. The test CHS (circular hollow section) joints which were not internally strengthened, failed with a large amount of plastic deformation. However, the ultimate bearing capacity of CHS joints strengthened by inside gusset plates was obviously improved. Some key CHS joints are suggested for strengthening with inside gusset plates, during the construction process. The work of this paper provides a reference for similar structures.

Vulnerability and Risk Assessment of Single-Layer Reticulated Domes Subjected to Earthquakes

AbstractIn order to provide a good understanding of the damage states of single-layer reticulated domes under earthquake loading, a number of increment dynamic analyses are carried out on domes with different spans, rise-span ratios, roof weights, and other parameters. A model is proposed for the quantitative evaluation of damage. The damage states for single-layer reticulated domes are defined based on their structural dynamic performance and corresponding damage factors. The vulnerability of single-layer reticulated domes is shown using fragility curves with different damage states. A model of probability distribution for seismic hazard, structural damage probability, and various losses, including direct and indirect economic loss and maimed and fatality loss, is discussed for assessing risk. The risk assessment of a single-layer reticulated dome is performed for different seismic intensities for its loss or fatality acceptability.

Study of the Dynamic Strength of Reticulated Domes under Severe Earthquake Loading

The behaviour of selected steel domes subject to severe earthquake loading has been investigated and reported. Particular attention has been given to assess the development and spread of plasticity throughout these structures. Several dome configurations have been considered, both perfect and imperfect, together with a range of varying rise to span ratios. Finite element analysis of these structures has been undertaken to determine the rate of spread of plasticity and the rate of increase in node displacement under seismic loading. The dynamic strength failure acceleration (DSFA) has been defined as the acceleration at which the rate of spread of plasticity and node displacement reaches a runaway level and the structure becomes dynamically unstable. For the dome structures under consideration DSFA occurred at an acceleration of approximately 8 m/s2. In addition, the DSFA decreased by 15%–50% for the imperfect structures when compared with the perfect domes and was lower for the multi-directional seismic input. Also, the DSFA decreased gradually with a corresponding increase in the rise to span ratio.

Size Effect and Material Property Effect of the Impactor on the Damage Modes of the Single-Layer Kiewitt-8 Reticulated Dome

The dynamic response of large space structures under accidental impact has been the subject of intense research since the occurrence of the 9/11 incident. In the present paper, using the 3D ANSYS/LS-DYNA, size effect and material property effect of the impactor on the damage modes of the single-layer Kiewitt-8 reticulated dome were investigated, respectively, where the impactor was the cylinder and the impact direction was vertical. Firstly, analytical results with the rigid impactor indicated that the impactor size can change the damage mode of the reticulated dome. It was found that the probability happening to the global collapse has an obvious rise with the size increase of the impactor. Furthermore, the deformable impactor was considered to figure out the difference with the rigid impactor; the comparisons indicated that the deformable impactor, which has the same mass and the same striking velocity with the rigid impactor, can contribute to the occurrence of the global collapse at a certain initial striking condition.

Dynamic Constitutive Relation and Fracture Model of Q235A Steel

Strength and ductility data for Q235A steel from 20 oC to 950 oC was obtained from a series of experimental tests. The stress rate sensitivity was studied by conducting Split-Hopkinson Tension Bar (SHTB) test and uniaxial tension test on smooth cylindrical specimens while the influence of stress triaxiality on ductility was revealed by conducting upsetting tests, tension tests on pre-notched cylinder specimens and torsion tests on SASs. Slightly modified versions of the two Johnson–Cook (J–C) models describing flow stress and fracture strain are presented to characterize the properties of Q235A steel as function of strain rate, temperature and stress triaxiality. Corresponding model parameters were calibrated based on the test data and with the help of finite element calculation. It was found that the modified Johnson–Cook (MJC) models give more close predictive results compared with the original J–C models.

Local–Global Interaction Buckling of Stainless Steel I-Beams. II: Numerical Study and Design

AbstractThe paper presents a detailed finite-element model used to study the local–global interaction buckling of stainless steel I-section beams. The model was constructed with the commercial software package ABAQUS v.6.11 and was verified against the experimental data presented in a companion paper, yielding accurate predictions of interaction buckling behavior and ultimate capacity. Parametric studies were conducted by using the calibrated models to extend the experimental database. The accuracy of the Australia/New Zealand, American, and European standards for stainless steel structures was evaluated by using the available data. It was found that the codes were incapable of capturing the interaction buckling effect, thus affording overly optimistic strength predictions for beams of high section slenderness. Existing direct strength method formulas, as proposed for carbon steel beams and stainless steel columns, were also evaluated to assess their applicability to the stainless steel beams.

Prediction of confined blast loading in single-layer lattice shells

Single-layer lattice shells (also known as gridshells) are widely used for architecturally innovative structures. When an explosion occurs inside such a structure, confined blast loading on the structural components will be seriously affected by different factors, such as charge locations and weight, structural types and forms. Moreover, slight changes of blast loading perhaps result in various responses for such a complicated structure. In this paper, blast loads on single-layer lattice shell are calculated by AUTODYN software package. The effect of scaled distance, ratio of rise to span and ratio of height to span are investigated. Simplification of blast loading is studied, and the principles of equivalent loading process are validated with a 40 meters single-layer Kiewitt-8 reticulated dome. In order to predict the blast loading, a precise and simple model is derived from numerical results, which is suitable for a wide scope of single-layer lattice shells. Two applications with different charge weight, structural spans and forms are worked out by using the blast prediction model. Good agreements of comparisons are achieved between prediction model and numerical results.

Numerical Investigation on the Reticulated Domes Subjected to the Multi-Point Impact

In the present paper, FE model of the single-layer Kiewitt-8 reticulated domes with a span of 60m was built with using of ANSYS/AUTODYN. The dynamic response of the reticulated domes against the multi-point impact was investigated, where a special impactor was involved. Based on the simulation results, four damage modes were concluded，which are local damage, global collapse, local damage with punching plug, punching plug respectively. It was indicated that the initial kinetic energy of the impactor have a close correlation with the damage mode. Furthermore, the characteristics of dynamic response for each damage mode were shown.

Investigation of Construction Vertical Deformation and Pre-Deformation Control for Three Super High-Rise Buildings

The cumulative problem of vertical deformation for super high-rise buildings during construction becomes more significant as the height of structure continue to increase nowadays, for which the investigation of the characteristics of the vertical deformation is worth conducting. First, the technique of simulation of the construction process for super high-rise buildings was developed systematically, with which simulation of construction of the three typical high-rise buildings was conducted. The effect of concrete creep, shrinkage and leveling during construction were investigated and the characteristics of the vertical deformation revealed. Furthermore, a method of pre-deformation for super high-rise buildings was presented with deformation compensation stepwise. The total vertical displacement and the relative deformation between the inner core tube and the outer steel frame were chosen as the control targets in the method, which can be used to address the cumulative problem of vertical deformation and to provide technical support for deformation control in construction of super high-rise buildings.