D3.D.1 Design Process
The design process is carried out in three stages.
Ultimate Limit States
The program is structured so that ultimate design is first carried out in accordance with recommendations given in BS8110. All active design load cases are considered in turn and a tabulated output is printed showing possible reinforcement arrangements. 12, 16, and 20 mm bars are considered with possible spacings from 100,125,150,175, and 200 mm. Within these spacings, the layout providing the closest area of steel is printed under each bar size. Longitudinal and transverse moments together with critical load cases for both hogging and sagging moments are also printed. Minimum reinforcement is in any case checked and provided in each direction. Wood & Armer moments may also be included in the design.
Serviceability Limit States
In the second stage, flexural crack widths under serviceability load cases are calculated. The first and every other occurring design load case is considered as a serviceability load case and crack widths are calculated based on bar sizes and spacings proposed at the ultimate limit state check.
Thermal crack widths
Crack widths due to longitudinal and transverse moments are calculated directly under bars, midway between and at corners. A tabulated output indicating critical serviceability load cases and moments for top and bottom of the slab is then produced.
Finally thermal, crack width calculations are carried out. Through available parameters, the user is able to provide information on the type of slab, temperature range and crack width limits.
Surface zone depths are determined based on the type of slab and critical areas of reinforcements are calculated and printed in a tabulated form.
Four bar sizes are considered and for each, max crack spacing, Smax and crack widths are calculated for the critical reinforcements and printed under each bar size.
Maximum bar spacing to limit crack widths to the user's limit is also printed under each bar size.