A commonly overlooked area when seeking to reduce fabrication costs, the quantity of bolts used throughout a structure can present ample opportunity to eliminate expenses and associated labor.
Typically governed by one of three criteria — the load, either engineer-provided or system-generated; AISC’s recommended plate length rule as it applies to stabilizing a beam; or an engineer-provided minimum number of bolts schedule — connections are often over designed, leading to excessive and unnecessary bolts.
Working within AISC’s schedule of minimums for shear connections, connection optimization eliminates redundant bolts, holes and welds; SDS/2’s automated intelligence ensures that the connection still meets or exceeds design loads and related requirements.
The nuts and bolts of connection optimization
SDS/2’s intelligent automation now allows detailers and fabricators to perform automatic connection optimization that results in overall lower material and labor costs.
Using connection optimization on a project does not affect the steel structure itself — the steel beams, columns and braces remain the same size and in the same location. Instead, connection properties within SDS/2 are modified by enabling expanded bolt spacing enhancements and by reducing the minimum number of bolt rows required by a member’s nominal depth.
SDS/2 then identifies the connections that can be optimized while adhering to AISC requirements and redesigns them automatically.
Methodology
Originally detailed and fabricated by SDS/2 customers, the as-constructed projects were priced out using average material and labor costs provided by fabricators located throughout the Midwest.
Next, connection optimization was applied.
By enabling expanded bolt spacing enhancements and reducing the minimum number of required bolt rows in the software, SDS/2 automatically applied those new design parameters to connections throughout the model.
The projects were then priced out using the new material and labor numbers generated using optimization.
It is important to note that this optimization can be applied at the beginning of the project, during the project, or at any time before fabrication has begun.
Based on the results of the case studies detailed here, SDS/2 users can expect to realize a savings between $40 and $75 per ton per project.
Project 1: Central Indiana
The test case involved the connection optimization of a 100,000-square foot ER, immediate care center and medical office building in central Indiana. Without optimization, this project totaled $426,370 in steel costs such as beams, columns and connection material, as well as $84,580 for bolts, $49,422 for holes and $38,178 for welds. The final material and labor costs for the project were $598,550, with 546 reported tons.
Connection optimization resulted in substantial cost savings for the project. The bulk of the savings were realized in reduced bolt quantities and the labor required to install them. Bolt costs shrank to $62,311 — a reduction of $22,269 (26.3%). Associated costs for holes and welds were reduced to $36,090 and $34,656 respectively, a savings of $13,332 (26.9%) and $3,522 (9.2%).
Overall, connection optimization would have provided a savings of $41,151 for the project, a reduction of total reported tons by 2.6, and a cost savings per ton of $75.28.
| Material and Labor Costs | ||||
|---|---|---|---|---|
| Bolts | Holes | Welds | Total | |
| Pre-Optimized | $84,580 | $49,422 | $38,178 | $598,551 |
| Optimized | $62,311 | $36,090 | $34,656 | $557,399 |
| Cost Savings | $22,269 | $13,332 | $3,522 | $41,152 |
| % Savings | 26.3% | 27% | 9.2% | 6.9% |
Project 2: Nebraska
The test case involved the connection optimization of a six-story office complex located in downtown Lincoln, Nebraska. Without optimization, this project totaled $776,682 in steel costs such as beams, columns and connection material, as well as $92,188 for bolts, $37,285 for holes and $93,323 for welds. The final material and labor costs for the project were $999,481, with 995.75 reported tons.
Connection optimization resulted in substantial cost savings for the project. After applying SDS/2’s intelligent automation, the material costs on the project were lowered to $775,162. The bulk of the savings were realized in reduced bolt quantities and the labor required to install them.
Bolt costs shrank to $70,597 — a reduction of $21,591 (23.4%). Associated costs for holes and welds were reduced to $27,635 and $86,840 respectively, a savings of $9,650 (25.8%) and $6,483 (6.9%). Overall, connection optimization would have provided a savings of $39,244 for the project, a reduction of total reported tons by 1.95, and a cost savings per ton of $39.41.
| Material and Labor Costs | ||||
|---|---|---|---|---|
| Bolts | Holes | Welds | Total | |
| Pre-Optimized | $92,188 | $37,285 | $93,323 | $999,479 |
| Optimized | $70,597 | $27,635 | $86,840 | $960,235 |
| Cost Savings | $21,591 | $9,650 | $6,483 | $39,244 |
| % Savings | 23.4% | 25.8% | 6.9% | 3.9% |
