Estimation of the Fatigue Resistance of Sealants to Movement at Intersections of Sealed Joints and Improvements in the Joint Design Method

Abstract

The paper investigates the fatigue resistance of sealants to movement at the intersections of sealed joints and proposes improvements to the method of joint design. As a first step, the fatigue resistance of sealed joint intersections to shear movement caused by the sliding motion of curtain wall panels was studied experimentally. Three types of building sealants were evaluated. Shear movement consistently deformed both the intersectional and linear sectional areas of joint specimens. Cracks formed within the intersectional area earlier than in the linear sections of the joints. As a second step, the fatigue resistance of sealed joint intersections to the rocking motion of curtain wall panels was studied experimentally. Two rocking motion types were evaluated. A rocking fatigue apparatus for the intersectional joint specimens was developed, and the number of cycles until crack formation was determined for given movements. We successfully obtained data on fatigue resistance of sealants using the new apparatus. Fatigue resistance of sealed joints is lower in the intersectional area than in the linear sections of the joints and is particularly lowest with simultaneous movements occurring in longitudinal and horizontal joints. Finally, the effect of curvature radii of curtain wall panel corners on fatigue resistance was studied at intersections of sealed joints. The fatigue test was carried out employing specimens with curvature radii varying from 0–8 mm. Shear movement consistently deformed the intersectional area of the joint specimens. A relation was found between curvature radius and the number of cycles to crack formation, i.e., the larger the curvature radius was, the higher the observed fatigue resistance was to joint movement.