SNAP is a program specialized for Elasto-plastic dynamic response analysis, incremental analysis, stress analysis on the structural member of the building structure in arbitrary shape. With its superb operability and high level analytical function, it is capable of having speedy data input to outputting analysis result. There are no limitations to the building structure’s size or the data, it can process speedy calculation of complicated structures. This program have variety of functions that can support designing the high-rise structure, vibration control structure, seismically isolated structure and all types of structures.
SNAP is a nonlinear 3D structural analysis program with many features and functions. The advanced analytical technology allows for non-linear dynamic analysis, non-linear pushover analysis and non-linear static analysis. SNAP not only analyzes regular elements such as beams, columns, shear walls, trusses in the plastic region, but also estimates various devices used for seismic isolated structures with energy dissipation devices. Devices include springs, viscous dampers, hysteretic dampers and base isolators (Fig1).
Intuitive interface allows you to create variety of models from a simple model to a large and complex model without long learning.
By the step-by-step integration of Newmark-βmethod, nonlinear earthquake response analysis can be used for space frame structures by considering each member nonlinear behavior, also is used for multi-degree-of-freedom lumped mass system (MDOF). For the frame 3D models, maximum three directions acceleration wave data (two horizontal directions and up-down direction) can be input simultaneously. In the dynamic analysis, P-delta effect can be estimated for Frame 3D, 2D models and MDOF models.
As the result of earthquake response analysis, various useful and effective diagrams such as mode diagram, diagram of plastic hinge of structure, maximum response diagrams of story shear force, overturning moment, story drift angle, floor displacement, velocity and acceleration are found. With these diagrams, it is possible to evaluate the plastic deformation capacity of the structure (Fig 2).
By using the time history response result of nodes and the damage information of elements, SNAP-GP (Graphic Presentation: an option program) is useful tool to animate two models simultaneously in a window to examine the behavior of different models, such as traditional structure to seismic isolated structure or structures with energy dissipation devices and generate an AVI document (Fig 3).
Nonlinear static pushover analysis is a static procedure in which the magnitude of the structure loading is incrementally increased in accordance with a certain predefined pattern. Pushover analysis is used to the buildings with rigid floors to evaluate strength of the structure and find the week members and failure modes of the structure (Fig 4).
Through pushover analysis, the relationship between story shear force and deformation are found and the equivalent bi-linear/tri-linear skeletons curves are obtained (Fig 5,6).
Maximum 100 types of analysis cases with different loads, constraints etc can be assigned and analyzed. In nonlinear analysis, elasto-plastic springs are useful elements. For example. when a building foundation goes upwards by overturning motion, it can be modeled by using this spring.
In nonlinear analysis, when the elements are over their capacities, the program automatically corrects the element stiffness and keeps the unbalance force within the limit by iteration process.
The structures to be analyzed are frame 3D, frame 2D, truss 3D, truss 2D and grid-beam with no limitation for the number of nodes, elements, loads etc, the multi-degree-of-freedom lumped mass system, seismic isolated structure and structure with energy dissipation devices. The material s are reinforced concrete (RC), steel (S), steel encased reinforced concrete (SRC), etc.
For the beam, column, shear wall and truss, 24 types of hysteretic models can be used to define the nonlinear behavior of flexural, axial, shear and torsion stress-deformation relationship. These models include Takeda model, Ramberg-Osgood model, slip mode, etc, with bi-linear/tri-linear skeleton (Fig 7).
For the flexural and axial deformation of columns or shear walls, MS (Multi-Spring)/Fiber models are useful and effective to estimate the interaction between the bending moment and axial force. In MS/Fiber model, the section of the element is divided into many components (Fig 9) with the nonlinear stress-strain relations (Fig 8). It is possible to estimate both flexural and axial nonlinear deformation behavior simultaneously on the assumption of Navier’s hypothesis. Seven types of the nonlinear stress-strain relations are provided for concrete, steel and reinforcing bars.