- مبلغ: ۸۶,۰۰۰ تومان
- مبلغ: ۹۱,۰۰۰ تومان
Negligible research has been conducted to date on how to analyse weakened columns, thus safety risks are still involved when structures are weakened prior to demolition. There are various methods available for demolishing steel structures. One of the most efective methods that has been developed involves pre-cutting steel columns at a certain height, so that the least efort can be used to collapse the structure by means of pulling out some of the columns. This paper presents (a) an experimental setup developed to test the capacity of axially loaded weakened columns, which is used to (b) validate a fnite element (FE) model. The two pre-cuts that are presented in this paper are (1) the double window cut and (2) the triangular window cut, which are both commonly used in industry. A column weakened with a double window cut or triangular window cut reduces the axial load capacity by up to 50 and 40%, respectively. The FE models developed predict the axial failure load of weakened columns for a double window cut and triangular window cut are generally within an accuracy of less than 8 and 10%, respectively. It is shown at higher slendernesses the infuence of column cuts is less than would be intuitively expected because global buckling becomes dominant.
To date, the capacity of columns weakened to facilitate the demolition of buildings has typically been determined only by experience obtained from previous projects, and has generally not been focused on strict theoretical principles. This has great implications for safety, such as buildings collapsing during the weakening process. This paper provides a detailed set of experimental results which show the behaviour of columns weakened using a triangular window or double window cut. This has been done to improve understanding regarding such structural behaviour and to provide data for developing analysis models, thereby improving safety and efciency during the demolition process. A fnite element model was developed based on the results obtained. This model could be used to predict failure loads prior to demolition teams working on structures, such that safety can be ensured.
The efect of an initial geometric imperfection on the axial load capacity is important to consider. A sensitivity study highlighted that the load capacity is dependent on the imperfection factor and its magnitude. Signifcantly larger imperfection factors than the value of Length/1000 should be used for FE models when predicting failure loads in real structures, although the aforementioned value was used in this based paper based on experimental measurements and tolerances.