Summary of Steel Joist Output

Transcription

1 COMPUTERS AND STRUCTURES, INC., BERKELEY, CALIFORNIA JANUARY 2002 STEEL JOIST DESIGN Technical Note This Technical Note describes the steel joist design output that can be printed to a printer or to a text file. It also documents the design check messages, for example, CHK#2, that indicate the program is unable to design a particular joist. All the output data documented in this Technical Note, except for the summary output data, also appears when the Details button in the Show Details area of the Interactive Steel Joist Design and Review form is clicked. See Technical Note Interactive Steel Joist Design for more information. The program provides the output data in a series of tables. The heading or title for each piece of output data and a description of the data are provided in the tables in this Technical Note. Summary of Steel Joist Output This output is printed when you click the File menu > Print Tables > Steel Joist Design command and check the Output Summary checkbox on the resulting form. Similar output also appears on screen if you click the Details button in the Show Details area of the Interactive Composite Beam Design and Review form. See Technical Note Interactive Steel Joist Design for more details on the interactive design. Table 1 Summary of Steel Joist Output Story Level Beam Label Design Section Story level associated with the joist. Label associated with the line object that represents the joist. A typical label beam would appear as "B23." Do not confuse this with the Design Section Label, which might be identified as "16K3." The joist section selected as a result of the design process, for example, 16K3. Summary of Steel Joist Output Technical Note - 1

2 Table 1 Summary of Steel Joist Output Maximum Ratio Ratio Type The maximum design ratio for the joist. See Technical Note Design Checks for Standard Design Steel Joist Design and Technical Note Design Checks for Envelope Design Steel Joist Design for a description of how the ratio is calculated. This is either flexure, shear or LL Deflection, indicating the design check that produced the Maximum Ratio. Steel Joist Detailed Output This output is printed when you click the File menu > Print Tables > Steel Joist Design command and check the Detailed Output checkbox on the resulting form. Similar output also appears on screen if you click the Details button in the Show Details area of the Interactive Steel Joist Design and Review form. See Technical Note Interactive Steel Joist Design for more details on the interactive design. Basic Beam Information Joist The joist section selected as a result of the design process, for example, 16K3. Beam Label Story Length Loc X Loc Y Label associated with the line object that represents the joist. A typical label beam would appear as "B23." Do not confuse this with the Design Section Label, which might be identified as "16K3." Story level associated with the joist. Length of the joist. Global X coordinate of the center of the joist. Global Y coordinate of the center of the joist. Steel Joist Detailed Output Technical Note - 2

3 Group Joist Overwrite Data LL Deflection Limit Ignore Similarity Name of the design group (if any) to which the beam has been assigned. The live load deflection limit specified for the joist. This item is Yes if story level similarity (to a master story level) is to be ignored when designing the joist. RLLF Joist Design Results - Standard Design Analysis section A reducible live load is multiplied by this factor to obtain the reduced live load. The joist section used in the last analysis of the structure. Design section Span used to select capacities Load type Controlling Ratio Uniform TL Combo Equivalent Uniform TL Uniform TL Capacity Uniform TL Ratio The joist section selected as a result of the design process. The joist span that the program used to select the joist Uniform TL Capacity and Uniform LL Capacity. This is either Uniform or Not Uniform, indicating the type of load assumed by the program. See Technical Note Design Checks for Standard Design Steel Joist Design for a description of how the program determines if a load is uniform. The controlling design ratio for the joist. It is the larger of the Uniform TL Ratio and the Uniform LL Ratio. The design load combination that produces the largest Uniform TL (total load) Ratio. The equivalent uniform total load acting on the joist. See Technical Note Design Checks for Standard Design Steel Joist Design for a description of equivalent uniform total load. The specified uniform total load capacity of the joist. The ratio obtained by dividing the Equivalent Uniform TL by the Uniform TL Capacity. Technical Note - 3

4 Uniform LL Combo Equivalent Uniform LL Uniform LL Capacity The design load combination that produces the largest Uniform LL (live load) Ratio. The equivalent uniform live load acting on the joist. The specified uniform live load capacity for an L/360 deflection of the joist. Uniform LL Ratio Joist Design Results - Envelope Design Analysis section The ratio obtained by dividing the Equivalent Uniform LL by the Uniform LL Capacity and then multiplying by a factor to account for the possibility that the specified live load deflection limit may be different from L/360. See Technical Note Design Checks for Standard Design Steel Joist Design for a description of how this ratio is calculated. The joist section used in the last analysis of the structure. Design section Load type Equivalent uniform total load Minimum joist length Maximum joist length Controlling Ratio Maximum Moment Combo The joist section selected as a result of the design process. This is either Uniform or Not Uniform indicating the type of load assumed by the program. See Technical Note Design Checks for Standard Design Steel Joist Design for a description of how the program determines if a load is uniform. The equivalent uniform total load acting on the joist. See Technical Note Design Checks for Envelope Design Steel Joist Design for a description of how this is calculated. The minimum span for which the joist design section will be designed by the program. The maximum span for which the joist design section will be designed by the program. The controlling design ratio for the joist. It is the larger of the Moment Ratio, Shear Ratio and the LL Deflection Ratio. The design load combination that produces the Maximum Moment. Technical Note - 4

5 Maximum Moment Moment Capacity Moment Ratio Maximum Shear Combo Maximum Shear Shear Capacity Shear Ratio LL Deflection Combo Maximum LL Deflection LL Deflection Limit LL Deflection Ratio The maximum moment acting on the joist. The specified moment capacity of the joist. The ratio obtained by dividing the Maximum Moment by the Moment Capacity. The design load combination that produces the Maximum Shear. The maximum shear acting on the joist. The specified shear capacity of the joist. The ratio obtained by dividing the Maximum Shear by the Shear Capacity. The design load combination that produces the Maximum LL Deflection. The maximum live load deflection for the joist. The specified live load deflection limit for the joist in Length units. The ratio obtained by dividing the Maximum LL Deflection by the LL Deflection Limit. Steel Joist Design Check Messages This output is displayed on the model and in the printed output when the program is unable to design a particular joist. The check messages, such as CHK#2, are a "shorthand" way of indicating the design problem. In the printed Steel Joist Detailed Output and the output obtained from the Interactive Steel Joist Design and Review form, descriptive messages are provided along with the shorthand messages. In the printed Summary of Steel Steel Joist Design Check Messages Technical Note - 5

6 Joist Output and for display on the model, only the shorthand messages are provided. Table 3 shows that descriptive messages that correspond to the shorthand check messages. Table 3 Steel Joist Design Check Messages CHK# 1 CHK# 2 CHK# 3 CHK# 4 CHK# 5 CHK# 6 CHK# 7 Error: No section in the auto select list is adequate for this joist. Error: The element is not designed because it is not a joist section. Error: This joist is not designed because there is negative moment. Error: This joist is not designed because the equivalent uniform load exceeds 550 plf. Error: This joist is not designed because a single concentrated load exceeds the shear capacity. Error: This joist is not designed because no load data exists for spans this short. Error: This joist is not designed because no load data exists for spans this long. Table 3 Steel Joist Design Check Messages Technical Note - 6