PSI - Issue 47

Nurul Najiha Imam Robit et al. / Procedia Structural Integrity 47 (2023) 597–601 Author name / Structural Integrity Procedia 00 (2019) 000–000

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1.5. Numerical Method for Structural and Geotechnical Assessment The three-dimensional numerical study was conducted in PLAXIS 3D software to assess the ultimate bearing capacity of strip footing resting on ground surface of the silty sand soil layer. It was performed to connect the crack assessment of the building to the soil, underlying the footing structure which might fail in shear failure. The finite element soil model geometry adopted for the analysis was 15B x 10B, where B was the foundation width (Abdullah, 2021). The properties of soil and footing used in the analysis are listed in Table 1 correspondingly. 2. Results and Discussion Crack is visually detected on the building such as wall, the wall-column joint and the wall-beam joint. For point selected in the study, it was considered as severe damage crack with 15 to 25 mm crack width recorded. This crack line was a straight line, about 3 meter upwards. The pattern of cracks shows that it cannot be considered as non structural damage. The rebound number and compressive concrete strength were recorded 35 and 33 MPa respectively. The soil was classified as silty sand with particle size distribution of 51.47% sand, 44.12% silt and the remaining were clay. Total displacement increases as moisture content and degree of saturation increase, increasing pore pressure and decreasing soil strength, as shown in Figure 1. The soil underneath the footing experience expands and contracts in volume due to changes in moisture content under environmental conditions, leading to structural crack and soil movement. Soil becomes fully saturated when water content is high and loses its strength. In contrast, when moisture content is low, the soil is too dry and loses its cohesion. This is also due to the matric suction and saturation level changes that affect soil shear and elastic modulus (Hakro et al., 2022). The variation of moisture content effect in both conditions of soil lead to bearing capacity failure of soil. The main cause of structural cracks is the settling of the foundations due to the ground condition and structural loading (Raszczuk & Karolak, 2021), as environmental effect.

0 0,005 0,01 0,015 0,02 0,025 0,03 0,000 0,020 0,040 0,060 0,080 0,100 0,120 0,140 Total Displacement (m) Moisture Content (%) Sr = 100% Sr = 0% Sr = 50%

Fig. 1. Soil displacement beneath the footing under moisture content and degree of saturation effect

4. Conclusion This study aims to investigate effect of moisture content variation on ultimate bearing capacity failure of strip footing on silty sand soil, which cause to crack formation on structural building. The crack assessment was identified through visual inspection and non-destructive test. The cause of structural cracks is the settling of the foundations due to the ground condition, structural loading and environmental conditions were performed by numerical study. The settlement of the geotechnical structure underneath the structural loading is high when the soil is fully saturated and high moisture content. The crack formed was categorized as severe damage with crack width and length are 15 to 25 millimeters and 3 meters upwards respectively.