Trost, Burkhart
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Experimental Investigation of Sliding on Compact Sliding Specimens under Cyclic Loads
This experimental investigation addresses the sliding behaviour found to occur in reinforced concrete shear walls under earthquake loads. This investigation compromises a series of 13 compact specimens. The tests were conducted in a biaxial test setup. The test sequences were designed to mimic the load and displacement history of a portion of the squat wall under horizontal cyclic loading. The specimens were pre-cracked up to a defined crack width. Next, diagonal compression was applied. Through the variation of the reinforcement ratio, the initial crack width, the number of cycles and the amplitudes, the effects of aggregate interlock, dowel action and shear friction in the crack were quantified. In this paper we will present the observations and the results of the cyclic tests on the core specimen group and on the monotonically tested specimens.
Sliding Deformation Model for Reinforced Concrete Shear Walls under Seismic Loading
Accounting for all possible failure modes in seismic design and construction of reinforced concrete shear walls is important to ensure that the expected seismic performance of the building structures is attained. Sliding is a shear wall failure mode that can occur at flexural cracks or at cold joints. For example, significant sliding was observed at a four-story reinforced concrete building tested on the E-Defense shaking table. Whyte, Synge and Luna observed and examined sliding failure in their squat shear wall tests. In earthquake engineering, the sliding resistance on a crack in a reinforced concrete structural element is defined by simple equations in nearly all modern codes (EC8, ACI 318-1, fib-Model Code 2010). These equations have been developed for crack sizes occurring at serviceability performance levels and modified for use in seismic design. Large crack widths, which are common under earthquake loads, are not explicitly considered. This article presents a sliding resistance and deformation model for reinforced concrete shear walls. This model includes the interaction between the concrete and the reinforcement and complies with the equilibrium of forces and the compatibility of deformations at each point in the sliding process. At the core of the model is a plastic micro-model that characterises the interlocking process of the aggregate on an existing crack. Depending on the concrete strength, the compression stress, and the roughness of the crack surface, the force transferred across the crack is determined for any displacement and any crack width. The model is validated against a seriesof sliding tests on compact sliding specimens.
Sliding resistance at the joint between a structural wall and the basement ceiling: a mechanical model
This paper presents a mechanical model which is used to analyse the sliding resistance at the cold joint of nearly quadratic basement walls. The analysis is done on a building with a height of 40m and a basement wall size of 4m x 4m. In the parameter study the axial force and the reinforcement ratios, at the boundary and in the web, are varied. Analysed are the resistances of aggregate interlock, dowel action and the shear resistance of the reinforcement which is under compression. The study shows that for a quadratic wall in most cases, failure due to sliding occurs before the maximum flexural deformation is reached. Thus the flexural ductility, e.g. in pushover analysis, is overestimated when the anchorage lengths of the structural wall is short. Therefore it is recommended for squat walls to take a previous sliding failure into account in a performance-based earthquake analysis.