Computational assessment of seismic resistance of RC framed buildings with masonry infill

[摘要] ENGLISH ABSTRACT:Reinforced concrete (RC) frames with unreinforced masonry infill form the structural systemof many buildings and this is also true for South Africa. It is common practice to consider themasonry infill as a non-structural component and therefore it does not contribute to theperformance of the Re frame buildings under lateral loading such as earthquake loading.This is done by leaving a sufficient gap between the Re frame and the infill. This ensuresthat there is no contact between the frame and the infill during an earthquake event.However, it has been suggested that masonry infill can play a significant role in theperformance of a Re frame building under lateral loading.The first part of the study focuses on the South African situation. The relevance of shearwalls in these Re frame buildings as well as the size of the gap (between frame and infill) leftin practice, are investigated. This is done by finite element analysis.The second part of the study focuses on the effects that the infill can have on the globalperformance of the structure when there is full contact between the Re frames and infill. Theeffect of openings in the infill to the response of the frame is also investigated. Finite elementmodels of single span Re frames with infill is built and analyzed in order to investigatepossible damage to the infill, frame infill interaction and to obtain the non linear stiffness ofthe frame with infill as a whole. This obtained non linear stiffness can be modelled in Dianaas a non linear spring that will be used in the development of a simplified analysis method.The simplified method developed consists of a frame and two such non linear springs, placeddiagonally, and which have the same force versus displacement behaviour as the originalframe with infill. These single span frames can be added together to model a whole frame. Ina first step to generalise the simplified method, various geometries of infills are considered,varying span and height, as well as opening percentage, representing windows and doors ofvarying total area and positioning. However, in this study a single masonry type, namely solidbaked clay bricks set in a general mortar, is considered. To generalise the approach further,other masonry types can be considered in the same way. The use of these springs in asimplified model saves computational time and this means that larger structures can bemodelled in Diana to investigate response of'Rf' frame buildings with infill. The work reported in this thesis considers only in-plane action. Out-of-plane-action of themasonry infill has been reported in the literature to be considerable, under the condition that itis sufficiently tied to the frame to prevent mere toppling over, causing life risking hazards inearthquake events. This matter should be studied in continuation of the current research togeneralise the simple approach to three dimensions.

[发布机构] Stellenbosch University