Single-layer Spherical Lattice Shell Research Articles

Shaking table tests on seismic behaviors of a single-layer spherical lattice shell with shape memory alloy-controlled friction pendulum bearings

An innovative seismic isolation device incorporating a friction pendulum bearing (FPB) and vertically aligned shape memory alloy (SMA) strands is proposed for the seismic control of spherical lattice shells located in strong-earthquake regions. To validate the effectiveness of the proposed SMA-FPBs experimentally, a 1/10-scale single-layer spherical lattice shell test structure and a set of isolators were designed and fabricated. A shaking table was used to apply various three-dimensional seismic excitations to test structures equipped with and without different isolation bearings (SMA-FPBs or bare FPBs). Significant seismic behavior enhancements were observed when such isolation systems were used. However, bare FPBs cannot accommodate excessive displacements induced by high seismic intensities owing to their lack of adaptive control. In contrast, SMA-FPBs exhibited satisfactory control performance in terms of the peak and residual bearing displacements under fortification and rare seismic actions, and the adaptive properties of the SMA-FPBs protected the isolators from disassembly owing to excessive sliding displacements under extremely rare earthquakes, even though their re-centering abilities decreased slightly because of the failure of several SMA wires. Finally, the larger number of SMA wires in an SMA-FPB enhanced its restraining capacity against peak bearing displacement rather than improving the seismic responses of structural nodes and members.

Seismic protection of a single-layer spherical lattice shell structure using a separated three-dimensional isolation system

Vertical and three-dimensional (3D) isolation systems are emerging control technologies for spatial grid structures in high seismic intensity regions. Recently, multistage vertical isolation bearings (MVIBs) based on prepressed spring devices (PSDs) have been proposed to support the lattice shell and prevent the transfer of vertical ground motion components to the structure. Seismic dampers can be further combined with an MVIB to develop a hybrid bearing with a damping capacity. In this study, the vertical load-carrying and isolation mechanisms underlying the MVIB configuration were investigated in detail. A series of proof-of-concept tests were conducted on a prototype MVIB comprising four identical PSDs to study its actual mechanical behavior. The test results indicated that the MVIB specimen exhibited multilinear elastic behavior with enhanced load resistance. The key parameters of the tested bearing, such as the transition force and isolation stiffness, increased linearly with the number of PSDs. The MVIB model was subsequently refined using ABAQUS to comprehensively understand the mechanical performance of the spring isolator. Following a device-level study, a single-layer spherical lattice shell was used as the research target. The damped MVIBs and friction pendulum bearings were arranged at the roof supports and column bases, respectively, and the stiffness and energy dissipation properties of these isolators were designed. A system-level seismic analysis was conducted using OpenSees to compare the triaxial dynamic responses of the target structure before and after isolation. The results indicated that the separated 3D isolation system achieved its intended design goals and effectively protected the lattice shell structure from tridirectional seismic shaking.

Feasibility evaluation of pre-pressed spring devices for vertical isolation of single-layer spherical lattice shell structures

Single-layer spherical lattice shells are typical spatial structures for large-scale landmarks and public buildings. If such buildings are located in strong-earthquake zones, their seismic resilience must be considered. Long-span spatial structures are highly sensitive to multi-component ground motions, and vertical ground shakings lead to strong structural vibrations. Although a few vertical isolators with invariant stiffness have been developed, they are generally too stiff to effectively isolate vertical seismic shakings. In this paper, a nonlinear vertical isolator using pre-pressed and restrained helical springs called pre-pressed spring device (PSD) is proposed. The main advantages of the PSD are that it not only provides a high first stiffness and large bearing force to support the weight of the isolated object but also possesses sufficiently low stiffness to isolate vertical ground motions. In a vertical isolation system, PSDs are employed as basic load-carrying elements, and viscous dampers can be introduced into the system to function as additional energy dissipation devices. The configuration, working principle, and mechanical model of the newly developed PSD are described and explained in detail. Cyclic loading experiments were performed on a prototype PSD to investigate its actual force–displacement relationship. The experimental results showed that the PSD specimen exhibited multilinear elastic behaviors with clear first and isolation stiffness properties. A novel numerical model of the PSD was constructed, and the accuracy of the model was validated by comparing the simulation and experimental results. Subsequently, PSD-damper assemblies and friction pendulum bearings (FPBs) were used to form three-dimensional (3D) isolation bearings for a single-layer spherical lattice shell with surrounding columns. The seismic responses of the controlled structure were evaluated using nonlinear time-history analysis. The numerical results revealed that the PSDs achieved effective static-load support and vertical isolation, and that the entire 3D isolation bearings significantly improved the seismic behavior of the lattice shell structures in all three directions.

Seismic Performance Assessment of a Single-Layer Spherical Lattice Shell Structure with Multifunctional Friction Pendulum Bearings

The dynamic responses of spatial lattice shell structures with friction pendulum bearings (FPBs) under multidimensional seismic excitations are complex. In addition, FPBs may experience uplift and separation of the bearing components owing to excessive displacements. In this study, a novel multifunctional FPB (MFPB) with a multi-defense system was developed, and its effectiveness in reducing and controlling the seismic responses of spherical lattice shell structures was evaluated. The proposed MFPB comprises an FPB, superelastic shape-memory alloy cables, and sleeve restrainers. A mechanical model of the MFPB was established, and its isolation and control behaviors were investigated through numerical simulations. Furthermore, the main characteristics and advantages of the isolation system were analyzed. Subsequently, the MFPB system was applied to a single-layer spherical lattice shell structure with surrounding columns. A computational model of the controlled structure was developed using the OpenSees software. Finally, nonlinear time history analyzes were conducted to analyze the seismic performance of controlled and uncontrolled lattice shells. The results demonstrate that the MFPB isolation system can effectively control the structural responses of isolated spatial lattice shell structures under horizontal and vertical seismic excitations and improve their seismic resilience.

Study of the Similarities in Scale Models of a Single-Layer Spherical Lattice Shell Structure under the Effect of Internal Explosion

The similarity of each scale model is verified based on the theory of similarity, deriving the similarity law of internal explosions in a single-layer spherical lattice shell structure via dimensional theory, calculated based on models with scaling coefficients of 1, 0.8, 0.6, 0.4, 0.2, and 0.1. The results show that the shock wave propagation characteristics, the distribution of the overpressure on the inner surface, the maximum dynamic response position, and the position at which the earliest explosion venting occurs are all similar to those of the original model. With the decrease of scaling coefficients, the overpressure peak value of the shock waves of each scale model, and the specific action time of the positive pressure zone, as well as specific impulse are increasingly deviated from the original model values; when the scaling coefficient is 0.1, the maximum relative error between the overpressure peak value at the measurement point and the specific action time of the positive pressure zone as well as the specific impulse and the original model value is 4.9%. Thus, it is feasible to forecast the internal explosion effect of the original structure size model by using the experiment results of the scale model with scaling coefficient λ≥0.1.

Overpressure peak formula of surface shock waves in single layer spherical lattice shell under the effect of internal explosion

This paper uses the LS-DYNA analysis software to make numerical simulation and analysis on the blast effect of single layer spherical lattice shell structure under the action of internal explosion, summarized overpressure peak distribution characteristics of surface shock waves in lattice shell under internal explosion: shock waves overpressure peak of lattice shell top is mainly secondary wave overpressure peak, while at rest locations, it is mainly first wave overpressure peak; shock waves overpressure peak distribution in lattice shell and side wall is big at both ends and small in the middle. Finally, according to distribution law of shock waves overpressure peak, we proposed simplified calculation formula for surface shock waves overpressure peak in singer layer spherical lattice shell, to provide reference for antiknock and explosion-proof of engineering structures.

Application and design of 3D seismic isolation bearing in lattice shell structure

ABSTRACTA three-dimensional seismic isolation bearing (3DSIB) was introduced. The 3DSIB was designed and applied in a single-layer spherical lattice shell structure with 40 m span by using a SAP2000 software. The original record of the Taft seismic wave was input into the shell structure in X, Y and Z directions, respectively in the model. The effectiveness of the 3DSIB was examined by time history analysis to the shell structural model in the SAP2000. It was shown that the isolated structure with 3DSIBs had better performance compared with the un-isolated structure in terms of the nodal absolute acceleration response as well as member axial force. It was found that the 3DSIB had good isolation function in both horizontal and vertical directions for shell structure under seismic conditions. Furthermore, the influence of horizontal and vertical stiffness of 3DSIB on the structural period, structural member peak axial force and nodal absolute acceleration were analysed. The variation of the structural respo...

Propagation law of shock waves in single layer spherical lattice shell under internal explosion

Using software of finite element analysis LS-DYNA, in this paper we performed numerical simulation on the propagation law of shock waves in single layer spherical lattice shell under the effect of internal explosion, obtained the laws of propagation, reflection, convergence and peak appeared of shock waves, concluded that the damage of enclosed structure is closely related to, initial overpressure peak, and partial secondary overpressure peak, analyzed the influences of explosive quantity, explosion center height, and explosive eccentric position on the propagation law of shock waves. Based on the results of numerical simulation, we concluded joint area between lattice shell top and wall shell is the key location for explosion venting and pointed out the calculation formula of overpressure peak on structure surface of higher fitting precision is feasible.

Performance of Seismic Restrainer with SMA Springs for Sliding Isolation of Single-Layer Spherical Lattice Shells

The seismic response of a single-layer spherical lattice shell controlled by restorable sliding isolator is studied under different seismic excitations. The isolation system consists of flat steel-Teflon sliding isolators and superelastic SMA spring restrainers. The NiTi-SMA is used to fabricate helical spring for recentering control of the isolation system. In the first step of this investigation, the configuration scheme and functioning mechanism of a novel SMA spring restrainer are introduced briefly. Then, realistic mechanical behavior of large-scale superelastic NiTi helical spring is studied through a set of cyclic experimental tests. According to the obtained hysteresis loops, a mechanical model combining multilinear model and hysteresis model is developed to simulate the overall response of the SMA-based seismic restrainer. Besides, the sliding isolator is evaluated using a bilinear force-displacement hysteresis model. Finally, a 60 m span single-layer spherical lattice shell with substructure is modeled with finite element program. Nonlinear time history analyses of the controlled and uncontrolled lattice shell are performed considering multidimensional seismic inputs. The study shows that the seismic response of the controlled lattice shell can be effectively reduced by using isolation and control devices. Furthermore, the seismic response of the isolation system such as peak displacement and residual displacement can be effectively controlled by using the developed SMA spring restrainers.

The Failure Criterion of Single-Layer Spherical Lattice Shell Based on Kinetic Energy

The dynamic failure criterion of single-layer spherical lattice shells has been an important research subject. The paper examines dynamic failures of single-layer spherical lattice shells and proposes the structure dynamic failure criterion based on the kinetic energy. The failure criterion was demonstrated through the dynamic failure test on a single-layer spherical lattice shell. Then, simulation analysis was carried out through two cases with material damage taken into account. The proposed failure criterion can accurately identify failure moments caused either by strength fracture or by stability fracture.

Vertical and Horizontal Seismic Response Analyses of Long-Span and Single-Layer Spherical Lattice Shell Structure

The dynamic characteristics of 80 m single-layer spherical lattice shell structure are analyzed to control its vibration under seismic load. Through the response spectrum curve of current design specification, the analyses for the vertical and horizontal seismic responses of the single-layer spherical lattice shell structure are made by CQC, and the displacement response of the nodes and internal force of the rods unit are calculated respectively. The calculation results show that the vertical and horizontal seismic responses of the long-span lattice shell structure are in great difference, and should be performed in vibration control at the same time, which could provide certain references for the seismic design and vibration control of single-layer spherical lattice shell structure.

Dynamic damage criterion and damage mode for single layer lattice shell

When member buckling and joint fractures are considered in the numerical analyses of single layer lattice shells, the relationship curve between peak ground acceleration of the earthquake and the maximum nodal displacement, and the time–history curve of maximum nodal displacement, are erratic and unpredictable. Therefore, with such considerations, the current approach to determine dynamic damage of single layer lattice shells by comparing peak ground acceleration of the earthquake with critical ground acceleration derived from incremental dynamic analysis is inappropriate. An improved structure dynamic damage criterion is proposed for single layer lattice shells in this paper, which reviews the balance status of structure dynamic resistance against the earthquake action, and the structure damage time can be predicted by the occurrence of non-convergent solution to the structural nonlinear dynamic equilibrium equations in the iterative process from the mathematical point of view. Numerical examples are presented to illustrate the simplicity and practicality of the proposed criterion. This criterion serves clear physical meaning and is of considerable potential applicability in analyzing single layer lattice shell structures. Results of parametric analyses of single layer lattice shells under severe earthquake actions indicate that the structure dynamic damage is not determined by material strength failure. For single layer spherical lattice shell, it is determined by structural instability resulted from member buckling; and for single layer cylindrical lattice shell, it is determined by the combined effect of structural instability and the change of structural topology that resulted from member buckling and joint fractures respectively.

The Stability Analysis on the Different Types of Single Layer Latticed Shell

This single-layer spherical reticulated shell has the advantages of reasonable stress,beautiful appearance ,fast construction,is widely applied in practical engineering. Through the static stability analysis of three kinds of single-layer spherical lattice shell structure using ansys, we get them in the uniform deformation under static load, the modal, buckling load. The results show that: The Kiewitt latticed shells displacement is small, structure is stable, better than SchwedLer and lianfang.

Dynamic Stability and Ultimate Capacity of Suspended Dome under Earthquakes

Suspended dome is a reasonable and novel type of long-span hybrid spatial structures based upon single-layer spherical lattice shell and tensegrity system. Based upon the structural force-bearing characteristics, the combined finite element model of beam elements, truss elements and cable elements is set up. A method taking the maximum displacement on nodes under earthquake acceleration of each level as dynamic response representative parameter is proposed to study the dynamic stable ultimate capacity of suspended dome by application of the incremental dynamic analysis in combination with B-R kinetic criterion. Furthermore, considering suspended dome has the clear advantage over Single-Layer Spherical Lattice Shell for a structure with a long span and a small ratio of rise to span, the influences of factors such as structural parameters, geometric parameters, and different earthquake input are investigated on dynamic stability for a kiewitt-type suspended dome with a long span and a small ratio of rise to span. Finally of suspended dome some conclusions are obtained such as the initial defects can clearly reduce dynamic stable ultimate capacity, and since the rise-span ratio, pre-stressing level and cross section area are not monotonous as variety to the structural dynamic stability, they should be optimized to enhance or improve the structural dynamic stability, which can be rules for engineering design.

Experimental Research on the Stability of Spatial Lattice Shell

In the interest of an understanding to the imperfection stability behavior, a model of single layer spherical lattice shell was designed. The size and the pattern of initial imperfections were entirely measured. Automatic harmony loading control system and data acquisition system was used. The experiment plan, method and results have provided reference significance for the study on the stability of spatial lattice shell. The experimental results and the results of measured imperfections method were compared and analysed in detail. It is verified that measured imperfections method can accurately take into account of the effect of initial imperfections and it can be used for the supplementary checking computations of some important finished structures.

Study on Stability of a New Prestressed SINGLE-Layar Spherical Lattice Shell

Prestressing of lattice shell is realized by cable, and author put forward a new kind of layout: The prestressing has been brought to bear by hoop and radial element of single-layer lattice shell, which avoid cable's effect on architectural purpose. The element has been made to sleeve, and the magnitude of prestressing is dominated by bolt. Article shows an example of K6, K8 single-layer spherical lattice shell, and the prestressing have been exert on partial ribs and hoops. The prestressing has been calculated by element axial force under normal loading. Stability of shells have been studied, and show the deformation satisfy the criteria under normal loading; The ultimate capacity has been improved obviously, loads transfer is rational. The new layout of prestressing is a promising technique.