Ahmad J. Durrani

GRAVITY LOAD EFFECT ON SEISMIC BEHAVIOR OF INTERIOR SLAB-COLUMN CONNECTIONS

The effect of superimposed slab loading on the behavior of exterior slab-column connections was studied by testing 2-bay slab-column subassemblies. Each subassembly consisted of an interior and two exterior connections. Three identical slab-column subassemblies were subjected to the same cyclic lateral-displacement history while each supported a different superimposed slab load. The tests show that increased slab load substantially reduces the lateral drift capacity of the connections. A limiting shear stress is suggested to insure adequate drift capacity for exterior slab-connectiions. A rational method to calculate the moment capacity of exterior connections is developed. The test results are compared with present ACI 318-83 Building Code provisions and ACI Committee 352s recommendations for design of slab-column connections.

SEISMIC RESPONSE OF CONNECTIONS IN TWO-BAY REINFORCED CONCRETE FRAME SUBASSEMBLIES WITH A FLOOR SLAB

The effect of the presence of a floor slab on the behavior of beam-column connections was studied by testing two-bay frame subassemblies. Each subassembly consisted of two exterior connections and an interior connection. Individual interior and exterior connections were also tested to study the effect of continuity on the response of connections. The tests have shown that a larger slab width contributed to the flexural capacity of beams in continuous subassemblies compared to that observed in tests on sigle connections. Both the continuity of the test subassembly, as well as the presence of the floor slab, resulted in increased shear in the joints. The energy-dissipation capacity in continuous subassemblies was not affected by the presence of the slab; however, the lateral-load resistance increased by as much as 30 % lateral drift, and the degradation of stiffness was considerably delayed. Based on the results of this study, suggestions are made to include the effect of a floor slab in the procedure for designing beam-column connections.

SEISMIC RESPONSE OF INTERIOR SLAB COLUMN CONNECTIONS WITH SHEAR CAPITALS

Four interior slab-column connection subassemblies were tested under earthquake-type loads. The details of the study are described. The effect of the size of shear capital on the strength stiffness, and failure mechanisms of a slab-column connection was studied. Both punching shear failures and bending failure were observed. The current ACI Building Code (ACI 318-89) recognizes that there are two possible locations of the critical seciton of a slab, which vary in depth. Based on the test results, the critical section of a slab with shear capitals subjected to seismic loads may be at a location not recognized by the code. A shear capital must have a sufficient length with respect to the depth of the slab and be appropriately reinforced to effectively increase the shear capacity of the connection.

Seismic Response Modeling of Multi-Story Buildings Using Neural Networks

A neural network based approach to model the seismic response of multi-story frame buildings is presented. The seismic response of frames is emulated using multi-layer feedforward neural networks with a backpropagation learning algorithm. Actual earthquake accelerograms and corresponding structural response obtained from analytical models of buildings are used in training the neural networks. The application of the neural network model is demonstrated by studying one to six story high building frames subjected to seismic base excitation. Furthermore, the learning ability of the network is examined for the case of multiple inputs where lateral forces at floor levels are included simultaneously with the base excitation. The effects of the network parameters on learn ing and accuracy of predictions are discussed. Based on this study, it is found that appropriately con figured neural network models can successfully learn and simulate the linear elastic dynamic be havior of multi-story buildings.