Non-destructive testing and finite element modelling of historical Masonry Wall

Abstract

The conservation of heritage structures is a critical field often overlooked worldwide, with developing countries severely lacking in the field. The lack of adequate and sustainable conservation has led to the degradation of many heritage structures. This research investigates the Non-Pareille manor house, an excellent example of Cape Dutch architecture. The manor house is classified as a Grade 1 heritage resource by SAHRA, the highest level of significance in South African heritage. The mechanical properties of the front gable wall of the Non-Pareille manor house have been determined through non-destructive testing and finite element analysis. The non-destructive testing methods used in this research are rebound hammer testing and ultrasonic pulse velocity testing. The surface level compressive strength has been determined through rebound hammer testing, following calibration through site sample crushing in a laboratory. Poisson’s ratio and Young’s Modulus for the masonry have been calculated from ultrasonic pulse velocity test results. From visual inspection, severe cracking above the door opening has been noted and remediation is recommended to avoid further crack opening. The compressive strength distribution indicates a higher strength at the centre wall panel, with a higher Young's modulus and a lower Poisson's ratio. Increased cracking has been noted on the right wall panel, corresponding with a lower compressive strength, Young's modulus and a higher Poisson ratio. The tested material properties have been incorporated into a finite element model of the wall for simulation. The finite element model has been developed as a simplified micro-model, with material properties obtained from non-destructive testing. A quasi-static analysis has been completed on the model for four loading scenarios: an unbraced gable wall with and without applied wind loading, and a braced gable wall with and without applied wind loading. This has described the wall in its current condition and a reconstructed condition. The reconstruction of the roof structure imposes an additional load on the gable wall and increases the Von Mises stress by approximately 15%. However, a decrease of approximately 30% in the total estimated deflection of the gable wall has been noted. This indicates the necessity of reconstructing the roof structure to reduce the risk of further damage to the structure. The study achieves results through the development of a testing methodology that is unique in the field of conservation of heritage structures in South Africa. The method can be further incorporated to other heritage structures in South Africa to sufficiently describe the mechanical properties and aid in the development of suitable conservation plans.