INFLUENCE OF SOIL BEARING STRATA ON STRUCTURAL AND ARCHITECTURAL FOUNDATION DRAWINGS FOR REINFORCED CONCRETE PAD FOOTING

S.P. Wasiu, T.S. Olanrewaju, A.A. Ala

Abstract


This study investigates the influence of varying soil bearing capacities on the structural and architectural design requirements of reinforced concrete pad footings. Five common Nigerian soil types—clayey, silty, sandy, lateritic, and gravelly soils—were analyzed using standard geotechnical parameters. The simulation was conducted using ORION software, and outputs were analyzed using Microsoft Excel and SPSS 28.0. Bearing capacities were assigned as follows: 150?kN/m² (clayey), 175?kN/m² (silty), 200?kN/m² (sandy), 230?kN/m² (lateritic), and 250?kN/m² (gravelly). The results revealed that soils with lower bearing capacities demanded significantly larger pad areas, higher reinforcement volumes, deeper foundation depths, and greater total structural loads, leading to increased construction costs and material inputs. For instance, the required pad area decreased progressively from 2.00?m² for clayey soil to 1.25?m² for gravelly soil, while pad side dimensions reduced from 1.41?m to 1.12?m. Correspondingly, the total foundation weights ranged from 35.40?kg in PF1 (clayey) to 25.13?kg in PF5 (gravelly), with densities decreasing from 1111?kg/m³ to 1047?kg/m³. These variations affected the structural layout and reinforcement detailing in the foundation drawings, with conservative reinforcement schedules necessary in low-strength soils. Cost analysis confirmed that clayey soil footing (PF1) incurred the highest cost (?29,333.63), while gravelly soil footing (PF5) was the most economical (?20,653.90), showing a strong inverse relationship between soil bearing strength and construction expenditure. The study concludes that soil type plays a pivotal role in optimizing footing design, material economy, and overall construction efficiency. It underscores the necessity of incorporating accurate geotechnical investigations early in architectural and structural planning stages.

 

Keywords: Soil bearing capacity, pad footing, foundation design, construction cost, structural optimization


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