Presented in this paper is an experimental program involving the testing offive 3/4 scale, interior slab-rectangular column connections subjected to combinedeffects of gravity and biaxial unbalanced moments. This experiment investigates theeffects of biaxial loading, and use of stud shear reinforcement, on the performance ofthe connections for rectangular columns with aspect ratio of 5. The main parametersstudied are the strength, drift capacity, ductility, and stiffness of the slab-columnconnections. It was found that biaxial unbalanced moments reduce considerably thestrength, ductility, drift capacity, and stiffness of the connection. It was also found thatslab-column connections with rectangular columns having column aspect ratio of fiveand loaded biaxially may not be able to sustain a drift ratio of 1.5% even if gravity shearratio Vg/Vo is kept less than 0.4.

This paper presents some code expressions for the punching shear strengthof slab-column connections. The influence of slab thickness (size effect), columnaspect ratio and concrete compressive strength are investigated by examiningexperimental results.

The paper presents an overview of different shear reinforcing methods forflat concrete slabs supported on columns. Typical reinforcing systems are described forboth new construction and for retrofitting existing slabs. These systems have beenstudied, tested and used in construction in the last several decades. The description ofthe reinforcement types, properties, methods of design, and construction issuesrelated to placement in slabs is included in this paper. The aim is to show theimportance of providing shear reinforcement in flat concrete slabs in the vicinity ofcolumns in terms of both strength and ductility. The theoretical background and themost important requirements for the effective shear reinforcement are emphasized anddiscussed. Selected experimental results are presented to illustrate the performanceof slabs with different types and placement configurations of shear reinforcements inslabs.

At the department of Structural Engineering, formerly the Department ofBuilding Statics and Structural Engineering and the Department of Bridge Structures,Royal Institute of Technology in Stockholm (KTH), now merged into the Department ofArchitectural and Civil Engineering, research on punching of concrete slabs and plateshas been conducted for many years. The first report published in English was thefamous “Punching of Concrete Slabs without Shear Reinforcement” Nylander &Kinnunen (1961). [22] Since then, a large number of punching tests have beenconducted, many of these are unpublished or only published in Swedish. This paper willsummarize some of the tests performed and also present new findings in this importantfield.

SP-232 The development of high-performance materials and advanced computational tools has allowed the building of relatively thin concrete slabs supported on columns. The simple appearance of such structural systems and ease of their construction make them economically attractive and popular. However, these structures develop complex three-dimensional stresses in the slab, at the columns, which can eventually lead to a potentially catastrophic brittle punching shear failure. Although structural failures are rare, in part due to high safety factors, understanding punching shear phenomenon is crucial for safe and rational design of flat reinforced concrete slabs supported on columns. As part of the activities of the ACI/ASCE Committee 445, Shear and Torsion, members of Subcommittee 445-C, Punching Shear, organized a symposium in conjunction with this special publication devoted to the state of the art on punching shear. The symposium will be held during the ACI Fall 2005 Convention under the sponsorship of ACI/ASCE Committee 445. The last significant and comprehensive overviews on this topic were completed several years ago by the fédération internationale du béton (fib) in their state-of-the-art report on punching shear (2001)1 and in the Proceedings of the International Workshop on Punching Shear Capacity of RC Slabs (2000)2 published by the Royal Institute of Technology in Sweden. Subcommittee 445-C has compiled a series of papers that present updated developments in the state of the art and research regarding behavior, rational design, and evaluation of code provisions related to punching shear. The papers are grouped into two parts. The first part contains a report, coauthored by members of Subcommittee 445-C, on issues related to design philosophy, code provisions, contributions of flexural and shear reinforcements, and seismic and blast loads. The second part includes papers on new developments obtained from different research centers from around the world. The aim is to present comprehensive and objective information on the topic of punching shear. It is hoped that this publication will be important for the engineering design community in its efforts to improve long-term strength and ductility of slab-column structural systems.