Siamak Epackachi

In-plane seismic behavior of rectangular steel-plate composite wall piers

AbstractAn experimental study investigated the behavior of large-scale steel-plate composite (SC) walls subjected to cyclic lateral loading. The testing program involved four rectangular SC wall specimens with an aspect ratio (height-to-length) of 1.0. The specimens were anchored to a concrete basemat with a pretensioned bolted connection that was designed to be stronger than the walls. The design parameters considered in the investigation were wall thickness, reinforcement ratio, stud spacing, and tie bar spacing. The pretest analyses, global force-displacement responses, contributions of the steel faceplates and infill concrete to the lateral resistance, load transfer between the faceplates and infill concrete, and damage to the face plates and infill, are documented. The four SC walls failed in a flexural mode characterized by tensile cracking of the concrete, tensile yielding of the steel plates, crushing of concrete at the toes of the wall, outward local buckling of the steel faceplates, and fracture...

Numerical and experimental investigation of the in-plane behavior of rectangular steel-plate composite walls

Steel-plate composite (SC) walls are composed of steel faceplates, infill concrete, shear studs bonding the faceplate to the infill, and tie rods linking the faceplates. In new build nuclear power plants, elastic response is sought of SC walls in design basis earthquake shaking and numerical and experimental studies on SC walls have focused primarily on response to design basis loadings. The inelastic response of SC walls for beyond design basis earthquake shaking has yet to be explored and characterized. The experimental and numerical response of four SC walls subjected to cyclic in-plane loading is summarized in this paper. The walls have an aspect ratio of 1.0 and are flexure-critical. A number of design parameters are investigated, including infill concrete thickness, reinforcement ratio, stud spacing, and tie bar spacing. Numerical models of these walls are constructed using the general-purpose finite element code LS-DYNA. The numerical analyses, and key experimental results are presented.

Rectangular SC Wall Piers: Summary of Seismic Behavior and Design

Steel plate composite (SC) wall piers are composed of two steel plates on both sides of a concrete infill. Composite action between the steel plates and concrete infill is achieved using shear connectors and tie bars. The tie bars also provide structural integrity by connecting the two steel plates together. SC wall piers do not have any flange walls, cross walls, or boundary elements. Their seismic response and lateral load capacity are governed by the in-plane flexural behavior and capacity of the SC wall cross-section at the base of the wall. The lateral load capacity is reached due to flexural failure in terms of: (i) concrete crushing of the concrete infill in compression, (ii) local buckling of the steel faceplates in compression, and (iii) rupture of the steel faceplates in tension. SC wall piers are composite alternatives to conventional reinforced concrete (RC) shear walls where the steel rebar curtains are replaced by steel faceplates on the exterior surfaces of the concrete walls. This approach expedites construction by eliminating the need for additional formwork and staging of concrete casting. This approach can also provide structural efficiency if the SC wall crosssection is detailed appropriately with adequate shear connectors and tie bars. These elements provide composite action and also restrain the steel faceplates from buckling prematurely (before yielding). Local buckling typically occurs between the base of the steel plates and the first row of shear connectors or ties, which makes this spacing important detailing criterion for SC wall piers. This paper will summarize the results from cyclic in-plane shear tests conducted on SC wall piers. Some of the cyclic lateral load-drift ratio responses are presented along with the typical hysteresis behavior and story drift capacity. Design equations for predicting the lateral load capacity of SC wall piers without boundary elements are compared with the test results.

Bayesian decision and mixture models for AE monitoring of steel–concrete composite shear walls

This paper presents an approach based on an acoustic emission technique for the health monitoring of steel–concrete (SC) composite shear walls. SC composite walls consist of plain (unreinforced) concrete sandwiched between steel faceplates. Although the use of SC system construction has been studied extensively for nearly 20 years, little-to-no attention has been devoted to the development of structural health monitoring techniques for the inspection of damage of the concrete behind the steel plates. In this work an unsupervised pattern recognition algorithm based on probability theory is proposed to assess the soundness of the concrete infill, and eventually provide a diagnosis of the SC walls health. The approach is validated through an experimental study on a large-scale SC shear wall subjected to a displacement controlled reversed cyclic loading.

Wind Flow Effects on a 56-Story Tall Building and Its Surrounding Environment

In recent years, new combinations of shape, height and configuration of buildings have induced intense near ground wind flows, which can cause unacceptable human discomfort. Therefore, the wind environment in public access ways and leisure areas has become a major design consideration in new and existing building complexes. Recently, Computational Fluid Dynamics (CFD) has become a powerful tool for the study of environmental problems, as this technique is more feasible and cheaper than other methods, namely the wind tunnel technique. This paper deals with one of the most common situations of urban planning, which lead to the amplification of the ground level wind speed around a 56-story tall building with especial architectural plan which consists of three wings with identical plan dimensions of nearly 48 meters by 22 meters which are placed at 120 degree from one another in the vicinity of three other 36-story tall buildings with rectangular architectural plan. A CFD program FLUENT, is used to illustrate the effectiveness of these building arrangement in increasing the wind speed and the correspondent discomfort level. Some design practices for the avoidance of severe induced wind speeds around buildings will be inferred from the present analysis, which can be useful for engineers, architects and urban planners.