Ravi OzarkerBentley Technical Support Group
The purpose of this document is to help engineers analyze and design walls for dams using Bentley's STAAD.Pro V8i.
STAAD.Pro is the professional's choice for steel, concrete, timber, aluminum and cold-formed steel design of low and high-rise buildings, culverts, petrochemical plants, tunnels, bridges, piles and much more. It is a general purpose structural analysis and design tool. This general purpose nature of STAAD.Pro V8i allows engineers to model and analyze variety of structures but at the same time often leads to the question, How? The intent of this document is to answer how to model a wall of a dam in the STAAD interface.
Walls of dams are usually very thick speaking relatively to the other dimensions. These walls are modeled using solid elements in STAAD.Pro V8i.
Hoover Dam (Ref. U. S. Department of the Interior, The Bureau of Reclamation)
The advanced drawing generation tools included in STAAD.Pro can make the model generation task very easy. The wall geometry in STAAD.Pro can be constructed in many ways:
Figure 1 illustrates a wall geometry that was created using the STAAD.Pro interface. This type of wall geometry can be easily created using the solid element tool and the circular repeat command.
Figure 1: Wall FEM model created using STAAD.PRO V8i
STAAD.Pro V8i's automatic hydrostatic load generator will help generate pressure loads on the wall surface as illustrated in Figure 2. The user has the option of applying the pressure loads with respect to the local coordinate axis of the plates or the global coordinate axis of the model.
The following two load cases will be created in this example:
Table 1: Wall Loading
Figure 2: Water pressure acting on wall
STAAD.Pro V8i will calculate the element stresses at the center and at the joints of the solid element which can help engineers design the walls appropriately. The items that are printed are:
Figure 3: Deflected shape of structure along with SXX normal stress distribution diagram.
The integration of the graphical contour plots with the element stress tables help engineers easily find the stress values in any stress concentration area.
Figure 4: Wall opening SXX normal stresses
The wall of the dam may be resting on soil. STAAD.Pro V8i's automatic foundation support generator generates spring supports for plate elements based on the sub-grade modules provided by the engineer. These springs could be compression-only springs and as a result of this a true stability analysis can be performed on the structure. The base pressure diagrams presented in Figure 5 are generated due to the soil spring supports underneath the wall. The maximum base pressure can be compared to the soil bearing capacity.
Figure 5: Wall base pressure distribution diagram.
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