Composite Canopy Load Test, Analysis, and Retrofit

A full-scale, in situ load test was performed on a composite canopy structure. The canopy structure is characterized by 3-3/8-in. thick composite panels composed of stainless steel and aluminum sheeting with an aluminum honeycomb core, bonded with adhesive. Embedded aluminum tubes act to provide additional flexural capacity and stiffness, allowing the canopy to cantilever up to approximately 15 ft. from the building. Shortly after construction, excessive deflections were observed, and upon review of conditions, retrofits were specified by the engineer of record. A load test was recommended to verify that the canopy could support code-prescribed loads, subsequent to the installation of repairs. Our team was called upon to develop and implement the testing and instrumentation program. Following the load test, our team was tasked with designing additional structural retrofits to strengthen and stiffen the canopy. An analytical model of the canopy was developed using CSI SAP2000 software, and results of the load test were utilized to verify the relative accuracy of the modeled behavior. Upon consideration of several unique variables, including material nonlinearity, panel delaminations, and loose, missing, and sheared fasteners, the results of the analytical model were compared to the load test results under various loading increments and were deemed to be reasonably accurate. The validated analytical model was subsequently used to analyze the effectiveness of a series of proposed retrofits.