FLAC、FLAC3D-英文讲义01-PPT.ppt

FLAC/FLAC3D Short Course Itasca Software Training Course Tongji University Shanghai, China October 27-31, 2008 Training ScheduleOctober 27, 2008 (afternoon) Finite Difference Formulation of FLAC FLAC3D Strengths Limitations Stability analysis of I-wall structure FLAC3D Structural ElementsJoining Structural Elements (SELs) and Pretensioning Cables FLAC3D Capabilities In addition to modeling a solid continuum with the main grid (zones and gridpoints), FLAC3D has the capability to model structures (cables, beams, piles, shells, geogrids, liners) SELs are true finite elements (elements and nodes) formulated to work in the finite difference framework of FLAC3D Structures can interact with the main grid and other structures Nomenclature Why Use SELs We could model everything with zones Zones are poor at modeling bending (a large number may be required across the thickness) Grid generation becomes problematic when modeling structures with zones (geometric problems as well as RAM shortage). If we are not interested in small scale local effects (e.g., detailed stress distribution across an oddly shaped beam section) then SELs are ideal SEL Links SEL nodes communicate with zones and other nodes via links (a logical connection) Two types of links node-zone and node-node Links have attachment conditions (e.g. springs) Links can attach anywhere to the main grid (SEL nodes do not need to coincide with gridpoints)! Default link attachment Node-Node Links SEL nodes will never automatically link to each other, even if the SEL nodes coincide when the SEL is created. You must manually create node-node links to allow different SELs (e.g., beam and cable) to interact with each other. Joining SELs NO!FLAC3D does not support chained rigid connections Yes! Example: Retaining wall with tieback Pretensioning Cables Remove a segment from the ungrouted portion Apply opposing forces to nodes on either side of the break and equilibriate Close the gap with