International Concrete Abstracts Portal

Four interior reinforced concrete flat slabs are analyzed deterministically using the finite element analysis (FEA) program ABAQUS. Using this verified FEA model, probabilistic FEA is performed considering uncertain material properties. Probabilistic FEA is executed using a new variance based method, namely, multiplicative dimensional reduction method (M-DRM). M-DRM is selected because it overcomes the computational cost limitation, which can be a barrier for these types of analyses; it provides the probability distribution of any structural response, e.g., distribution of punching shear strength; it conducts sensitivity analysis without requiring any further execution of the FEA code. M-DRM is automated in ABAQUS using python programing. First, this study examines how material uncertainty impacts the structural response of interior flat slabs, in terms of ultimate load and ultimate displacement. Then, sensitivity analysis is performed in order to prioritize the most influential input random variables with respect to these structural responses. Finally, probability distribution of the punching shear resistance is also derived, using the design equations from the American code (ACI 318) and Eurocode 2 (EC2), in order to examine the degree of conservatism associated with the current design practices.

Most methods for the design and analysis of reinforced concrete slabs for punching are based on experiments on slab-column connections, reflecting the situation in building slabs. Slab-column connections with unbalanced moments have also been studied in the past. Experiments indicate that the accuracy of models for asymmetrically loaded slabs is lower than for symmetrically loaded slabs. In this paper, the difference in accuracy between test predictions for symmetrically and asymmetrically loaded slabs is tackled. A plastic model, the Extended Strip Model, is proposed. The results of maximum loads according to this model are compared to experimental results of symmetrically and asymmetrically loaded slabs. The comparison between the proposed Extended Strip Model and the experimental results shows that the model has a consistent performance for both symmetrically and asymmetrically loaded slabs. Moreover, the model has as an advantage that it combines the failure modes of flexure, shear and punching. The proposed model can be used for the analysis of slabs. In particular, it can be used for the assessment of existing slab bridges subjected to concentrated live loads.

Over the last 20 years the Institute of Structural Concrete at RWTH Aachen University has conducted numerous punching tests on interior slab-column connections with different types of punching shear reinforcement. Within the tests, different types and arrangements of stirrups, lattice girders, and double-headed studs were used as punching shear reinforcement. In this paper, the efficiency of the various types of punching shear reinforcement is studied and discussed based on the experimental results of 39 tests on interior slab-column connections. By comparing the failure loads with the punching shear capacities without shear reinforcement according to ACI 318-14 and Eurocode 2 along with the German Annex, respectively, the increase in punching shear resistance with each shear reinforcement system is investigated.

The paper reports tests to investigate shear and punching behavior of voided slabs, part of a research aimed at studying the structural response of such systems. The voids are shaped like a truncated pyramid. The program included a series of twelve slabs, divided into four groups according to the transverse steel arrangement. The slabs were loaded by one or two forces and supported on two sides. This loading scheme was chosen to investigate the load transfer and resistant mechanism in the slab with voids, with the aim of studying the shear transfer at a column. Failures under point loads close to the support correspond to those typical in thick slabs. A combination of two failure modes occurred, with punching and diagonal shear tension. The capacity must be predicted using the concrete cross section reduced by the voids.

Three-dimensional (3-D) finite element analysis (FEA) is considered to examine previously tested and analyzed under static loading reinforced concrete slabs using the FEA software ABAQUS. Four interior reinforced concrete slab-column connections are presented; one slab is without shear reinforcement (SB1) and the other slabs are with shear bolts (SB2, SB3 and SB4) which differ in the amount of the shear bolts. The coupled plasticity damaged model previously calibrated is considered for modeling the concrete. In this research, parametric studies are presented considering different amount and placement of the shear bolts. The adopted FEA model is used to analyze and investigate the failure modes and loads and the crack patterns of the shear reinforced slab-column connections. Finally, the numerical results obtained from the parametric studies are compared to the current design code predictions.