HLR Section 6.1
Analysis Options
| CONTENTS
6.1.1 | Structure-Specific DF Options
6.1.2 | Direction of Travel
6.1.3 | Limit State & Working Stress Factors
6.1.4 | Add Roads at Beginning & End of Route
6.1.5 | Analysis of Ad-hoc Structures at End of Route
6.1.6 | Reduced Axle Loads
6.1.7 | Vehicle Reduction Factor
6.1.8 | Other Options
6.1.9 | Saving Application to Database
| Other Links: | Main Index | Route Data | Vehicle Data | Job ID Data | Analysis Methodology |
6.1 Analysis Options
| Prior to beginning the solution the program allows a number of analysis options to be specified. This can be done via the Analysis Options form shown below:
| 6.1.1 Structure-Specific DF Options For structures having their own unique Distribution Factors table HLR requires two HL vehicle-related parameters in order to be able to extract the correct DFs from it during analysis viz: An axle width for the HL vehicle - this may or may not be equal to the overal width of the vehicle or the maximum axle width as specified on the vehicle data tab. By default HLR will set it to the largest axle width found in the vehicle data table. The maximum number of tyres in the axle - The default value is set to 4. Structure-specific distribution tables allow multiple rows of DFs to be specified for a structure, the values being based on axle widths and number of tyres in each axle. Refer to Section 5.3(6) for details. 6.1.2 Direction of Travel The heavy load vehicle can be moved over the designated route in one of three ways: in the current (forward or outbound) direction; the reverse (return) direction; or in both directions. The forward direction is defined by the first node of the first link in the route if it is a "standard" route, or by the first node of the first section if the route is composed of more than one standard routes. For an arbitrary list of selected structures it is defined by the first structure number in the list. For travel in both directions, results of the analysis will be included in all reports. To distinguish between structures in each of the two separate directions, the top-hat symbol (^) will be appended to structure numbers analysed in the reverse direction. This convention is used in the Review Analysis form as well as the Restricted Bridges Only and All Bridges on Route reports. The Minute (Summary Report) will show results for both the outward and return trips separately. Although the same structure may appear twice in the report the text can easily be edited to suit your requirements (since it's a WORD document). 6.1.3 Limit State & Working Stress Factors Ultimate Load Factor As each structure along the route is analysed in turn, HLR will first check if ultimate moment capacities are available for that structure. If they are, a limit state check will be performed using the ultimate load factor specified here-in. Since the ultimate strength factor is prescribed at this point, scope therefore exists to use a reduced factor for non-load carrying vehicles, (eg. cranes), where the possibility of overloading is reduced. Similarly, reduced ultimate strength load factors can be used when the field-weighing of load platforms accurately confirms axle loads. Note, however, that although the factor specified for the analysis is generally your responsibility, the actual value used will still need to be based on the guidelines given in Section 7 of the current Austroads Bridge Design Code. Note also that the default Limit State Factor will only appear here if changes made in the Options/Default Settings form are saved to the Defaults File. If only the OK button is clicked on that tab the default will not supplant the parameter already in this field (refer to Section 8.1 for further information regarding the Options/Default Settings form). Working Overload Factor This field shows the current default Working Overload Factor. HLR assumes that the working Overload moments entered into the structure capacity tables are based on this value. If a structure has no ultimate moment capacities, or if the Check working stress flag is switched on for a given structure, a working stress check will be performed. Note that the check is done using the Overload moment capacities for the structure and not the Working capacities. The Working Overload Factor (Fw) shown on this form is only explicitly used in one of two situations: - When an overload moment other than that for the 140% limit must be calculated but the Default Working Overload Factor specified in the Default Options tab remains at 140% (see Section 6.2.1); or - When calculating and comparing moment ratios. In this case the calculated ratios R1, R2 and R3 are compared to the ratio Fw/100 (refer to Section 6.3.1 for details). Note that it is possible to specify a structure-specific value for Fw, in which case the Default Working Overload Factor specified in the Default Options tab will not be used. To alter the factor click the button labelled Change Factor. The modified value will only apply to the current run and will revert back to the default value when a new assessment is begun. If the Default Working Overload Factor specified in the Default Options tab is changed from the preset value of 140% this button will not appear on the form. 6.1.4 Add Extra Roads at Beginning & End of Route This option allows additional road information to be appended to the beginning and end of the "official" route taken by the heavy vehicle. In some situations the heavy load commences or ends its journey on local (council) roads that may not be the responsiblity of your organisation. The inclusion of these "council" roads is therefore for documentation purposes only. Structures lying on these roads will not be checked by HLR (they may not even exist in your database). To add extra roads to the route click the button labelled Add extra roads. A sample image of the dialog box is shown below. Information added on this form will be echoed in the field adjacent to the Add extra roads button on the Analysis Options tab. Refer also to Section 6.2 for a detailed description of the analysis process.
| 6.1.5 Analysis of Ad-Hoc Structures at End of Route To analyse additional (ad-hoc) structures at the end of the HL route click the button labelled Add extra structures. A dialog box will be displayed that will allow you to enter an arbitrary list of structure numbers. Any number of structure numbers can be entered and each number must be separated by a comma. Spaces between numbers are allowed (e.g. 3883, 75164, 65030 etc...). On exit from this dialog box the additional structures will be echoed into the field next to the Add extra structures button . They will also be inserted into a "dummy" link called "ADDITIONAL STRUCTURES AT THE END OF THE HL ROUTE". This link will be added to the end of your route. The link is designated with dummy start and end node numbers XXX and YYY respectively and will be automatically saved by HLR to the link database (as link number XXXYYY). The link name will appear in all output reports. Structures for which a restriction has been flagged will be included in the Summary Report. Because it becomes part of the total route, the dummy link will be analysed and treated as such. It will be saved with your application and can be manipulated, reported and printed in the same way as any other link in the route. It can also be manually edited at any time using the options from the main menu bar. 6.1.6 Width-Modified (Reduced) Axle Loads If this option is ticked HLR will use the Width-Modified (reduced) heavy vehicle axle loads when performing the assessment (if appropiate). If any of the axle widths in the heavy load vehicle exceed the limits specified on the Vehicles tab (and in the Options/ Defaults Settings form), HLR will multiply each axle load by the relevant factor (refer to the document "Width-Modified Axle Loads.pdf" for further details). Refer also to Section 4.2 (Vehicle Data) and Section 6.2 (Assessment Methodology) for details. 6.1.7 Vehicle Reduction Factor This option allows the heavy load moments, shears and reactions at the unrestricted travel speed to be optionally multiplied by a user defined vehicle reduction factor (VRF). It allows a check to be performed to determine if a legal vehicle of width 2.5m can concurrently occupy the bridge with the HL vehicle. In essence, it represents the previous Austroads Bridge Code Multiple Lane Modification Factor. If this option is ticked HLR will apply the VRF factor only to structures satisfying the set of criteria described in the next paragraph. If the entered value lies outside the range 0.8 - 1.0 a warning will be given by HLR, but the user specified value will still be applied even if this warning is ignored. Criteria for application of the factor: For every structure along the route the relationship Kerb-kerb width >= W+3.7 (in metres) must be satisfied, where W represents the overall width of the vehicle. If the structure width does not exist or is zero, or the VRF exclusion flag has been set (refer to Section 5.2.8 for a definition of this flag), the factor will not be applied. If the HL vehicle width (W) is entered as zero or is overlooked by the user the program will use a width equal to the maximum axle width. The factor is only applied to M1 where structure capacities are known, or only to the ratio R1 if not (i.e. the factor is not applied to M2, M3, R2 or R3). The factor is also applied to V1 (shear) and Reaction-1 if these capacities have been specified. Section 6.2.1(9) describes more fully how and where in the analysis process this factor is applied. The default value for VRF is 0.9, but this can be varied in the Options / Default Settings form (refer to Section 8.1 for a description of how this can be done). 6.1.8 Other Options Use default distribution factors only If this option is ticked HLR will use the default distribution/girder factors in the analysis, irrespective of whether a structure has its own unique DF table. Stop at restricted bridges If this option is ticked HLR will stop processing when it encounters a restriction and will give you the opportunity of either continuing the analysis or aborting it. 6.1.9 Saving Application to Database Click this button to save the Application to the database. If the Application has previously been saved with the same HL number the system will issue a warning and allow you to either enter a new number or to continue saving over the top of the old data. Application data is saved as a number of relational text files using a format similar to the main database files. They are stored in the ..\HLR4\Database\Application folder.