Structural Elements Structural Elements

In MOSES there are four types of structural elements: beams, generalized plates, part connectors, and structural post-processing elements. All of the properties of these elements are defined in terms of the "element local system". It is also the system in which loads and stresses will be reported. With respect to local system, the structural post-processing elements operate exactly the same as beams and generalized plates. The definition of the element system and the options that control it are considered in the next section. All of the structural elements have additional attributes that can be associated with them and which are defined with options. Most of these options can be used with any type of structural element and these are considered in a section below. Options which are specific to a given type of element are considered with the element definition.

While one can alter existing elements by issuing a new BEAM or PLATE command, this is often cumbersome since all of the data must be redefined. An alternative is offered by the command:


     ED_ELEMENT,  OBJECT, -OPTIONS

where OBJECT is the name of the object to which the options will apply. If OBJECT is two node names (they may include wild characters, but must begin with an *), the attributes will apply to all beams between those two nodes. If OBJECT is an attribute class name (begins with a ~), then the attributes will apply to all elements which belong to classes which match OBJECT. If OBJECT begins with neither an * nor a ~, then the attribute will be applied to all members whose names match OBJECT. Here, any option which is valid for the elements being edited can be specified. The ED_ELEMENT command works in the input channel through INMODEL, or under the MEDIT menu.

The string function which returns information about an element is:


     &ELEMENT(ACTION, DATA)

Where ACTION must be either EN_NODES, CLASS, CATEGORY, ELE_TYPE, STRW_USE, WEIGHT, BUOYANCY, DCOSINES, BLENGTH, LENGTH, SEG_LENG, RATIO, STRESS, CDR, NODES, RELEASES, E_COORDINATES, OFFSETS, CFB, CM, KFACT, LAMBDA, HAS_P-D and FLOODED, WIDTH, AREA, CENTROID, THICKNESS, SUBELEMENT, and DATA is normally an element name. The first one, however, is different. Here, DATA is a set of node names and the data returned will be a list of element names all ends of which are in the set of node names. If one specifies only one node, then it returns all elements connected to the specified node. The remainder of ACTIONs take an element name and return element information based on action. Most of these are obvious, for example the next four types of ACTION take an element name and the last computed unit check value, the last computed axial load, and the last computed cumulative damage ratio.

The next set of options are applicable to all types of elements. The first of these returns the class name, the next the category name, and the next the element type. "BEAM" is returned for beams, "PLATE" for plates, and "OTHER" for anything else. STRW_USE returns YES if the stiffener weight is included, NO otherwise. WEIGHT and BUOYANCY returns respectively, the weight and maximum buoyancy of the element. SN and SCF returns the SN curves used and the SCFs. Here, the order is from the first vertex to the interface between segments and finally the second vertex for a beam. For a generalized plate, there is only one value. DCOSINES returns the 3X3 direction cosine matrix which transforms vectors in the element system into the part system. The next three option return element length and element buckling length, and the length of each segment in feet or meters respectively. No value is returned for SEG_LENG when the element is a generalized plate.

The next three set of options are valid for beams and plates. The SN option returns N values of SN where N is the number of segments plus one for a beam and one for a plate. The SCF option returns the SCFs used for beam fatigue. There are three time the number of segments plus one for a beam and one number for plates. The J_SCF option returns the eight SCFs used for joint fatigue at each end of the beam if both ends are parts of tubular joints. If an end is not part of a tubular joint, the NOT_A_TUBULAR JOINT will be returned for that end. If the end is part of a tubular joint, but has the default values, then TUBULAR_JOINT_DEFAULTS will be returned.

The next set of options are again valid for all types of elements. The next four options NODES, RELEASES, E_COORDINATES, and OFFSETS, return the nodes, the releases (six values of YES or NO), the coordinates (three values in feet or meters), and the offsets (three values in inches or mm) at each vertex of the element.

The next set of the actions return values only for beam elements. CFB returns the compression flange bracing in inches or mm and CM returns the CM factor used in the AISC and API code checks. KFAC results the K factor used in the code checks and LAMBDA returns the strong and weak axis values of the slenderness parameter. HAS_P-D returns YES of the element includes p-delta loads, NO otherwise. FLOODED returns YES if the element is flooded, NO otherwise.

The last set of options return non empty values only for generalized plate elements. WIDTH, AREA, CENTROID, and THICKNESS Here, width and length are the maximum distance (feet or meters) across the Y and X element axis respectively. The area is returned in ft**2 or m**2 and the centroid in feet or meters. The thickness is returned in inches or mm. SUBELEMENT returns the subelement names for the specified element excluding the base element itself. In other words, this action will return a null value for a triangular plate.

The string function which returns information about a subelement is:


     &SUBELEMENT(ACTION, NAME)

Where ACTION must be either RATIO, STRESS, CDR, NODES, RELEASES, E_COORDINATES, or OFFSETS, and NAME is the name of the subelement. The options here return the same data as the same one for the &ELEMENT string function.