Assessment of the ACI-DAfStb Database of Shear Tests on Slender Reinforced Concrete Beams without Stirrups for Investigations on the Shear Capacity Scatter

Abstract

The shear transfer mechanism of RC slender members without stirrups still presents very high uncertainties and the question has generated many controversies and debates since the beginning of the last century. Regrettably, until now the real causes of this problem are not yet clear to the scientific community and the issue is still important to investigate, especially nowadays that the minimizing of natural resources is of uppermost global interest. Due to the increased laboratory costs, actual studies are more and more often devoted to numerical simulations based on previous experiments. Unfortunately, it is difficult to find test results suitable for investigations on the shear capacity scatter in the available specialized literature. Therefore, the objective of this paper is to provide different adequate sets of reported test results containing tests performed on almost identical beams. The ACI-DAfStb database of shear tests on slender reinforced concrete beams without stirrups is considered and analyzed through the use of both multivariate statistical methods and clustering data mining techniques. The database was firstly visually explored by scatterplots and investigated through both univariate and correlation statistical procedures, and then processed by clustering using the k-means algorithm. Similar sets of data were collected in groups of comparable experiments. Clusters containing less than six data sets were removed. The criteria to establish the rate of similarity between each set of data were chosen according to the JCSS Probabilistic Model Code. The study has led to the formation of 13 groups of comparable experiments each group containing a number of tests between 6 and 43, performed generally by different field workers. These groups of reported test results will be of great importance both for the continuation of the authors' research and for other researchers who investigate the causes of the shear failure scatter or develop improved shear design methods.

Scatter in the shear capacity of slender RC members without web reinforcement: an overview study

“…A total of 13 groups of shear tests on comparable slender RC beams without stirrups extracted from the ACI‐DAfStb evaluation database (the reader should refer to for details) and grouped by Sangiorgio et al were identified and considered for the subsequent analysis.…”

“…shows that, for each of the three models, predictions cover the range of observed shear strength in a satisfactory manner. In particular, the figure shows the comparison of the box plots of V test measured for groups 3, 5 and 12 of comparable experiments (notation according to ) and V R,c,θ evaluated with the three models A, B and C. A box plot is a statistical technique used to summarize and compare groups of data visually. In each box, the central mark is the median, the edges of the box are the 25th and 75th percentiles, the whiskers extend to the most extreme data points not considered outliers and outliers are plotted individually.…”

“…The 13 groups of comparable experiments mentioned were in turn filtered as previously done for the raw ACI‐DAfStb database . Barely three groups of comparable experiments remained from the original collection: groups 3, 5 and 12.…”

“…This group contains six tests performed by Chana and characterized by the following mean values of the parameters affecting the predictive models: b wm,group = 203 mm, h m,group = 406 mm, d m,group = 356 mm, A sm,group = 1256.6 mm 2 and f cm,group = 34 N/mm 2 . For more detail, the reader is referred to and . Based on those values and according to the guidelines given in , the probabilistic model was developed after the manner of Table .…”

“…These may result in inclined (diagonal tension) cracks. [17] for details) and grouped by Sangiorgio et al [18] were identified and considered for the subsequent analysis.…”