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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 24 Abstracts search results
Document:
22-107
Date:
March 1, 2023
Author(s):
Benjamin L. Worsfold and Jack P. Moehle
Publication:
Structural Journal
Volume:
120
Issue:
2
Abstract:
Steel and precast columns are commonly designed to transfer moments to foundations through cast-in-place headed anchors. The concrete breakout failure mode is not routinely checked, even though recent tests have shown it can limit the connection’s strength. This paper describes how physical test data are used to calibrate finite element models of column-foundation connections to investigate critical variables. When designing column-foundation connections with cast-in-place anchors, both beam-column joint shear strength and concrete breakout failure strength should be calculated, with the connection strength taken as the smaller of the two values. Results suggest that properly detailed distributed shear reinforcement in the foundation can increase connection strength and displacement capacity if the connection is controlled by the concrete breakout failure mode. This effect is ignored by current building codes.
DOI:
10.14359/51737146
22-060
January 1, 2023
Ghassan Almasabha and Shih-Ho Chao
1
Reinforced concrete squat structural walls (SSWs) are a popular seismic force-resisting system used in low-rise buildings due to their high strength and stiffness. However, extensive studies have shown that rectangular SSWs have limited shear strength and drift ductility, primarily because their deterioration initiates from brittle compression failure of the diagonal concrete struts across the wall’s web. This research investigated a new reinforcing detail for SSWs to achieve substantially improved ductility and strength. While the current ACI Code requires a mesh of steel reinforcing bars to reinforce the SSW web, the new detail presented in this paper fortifies the SSW by multiple steel cages which contain vertical reinforcing bars enclosed by transverse hoops. These steel cages can be easily prefabricated at a shop to minimize on-site assembly work and time. Each steel cage is similar to that in well-confined columns, which increases concrete’s strength and ductility, therefore allowing a higher amount of vertical reinforcement for greater shear strength. Five specimens with an aspect ratio of 0.5 and reinforced according to either the ACI requirements or by the proposed details, and one specimen with an aspect ratio of 0.33 using the proposed details were tested. Similar to prior research results, SSWs using conventional details exhibited a fast strength deterioration at low drift ratios due to severe damage of the diagonal concrete struts under cyclic loading. Conversely, the proposed SSWs provide an increase of approximately 100% in the drift and ductility ratios, as well as a very gradual strength degradation and concrete damage progression. The proposed design allows SSWs to develop a ductile seismic behavior which is essential to safety against collapse, post-earthquake functionality and repairability, and seismic response predictability of structures. The enhanced ductility warrants a higher shear strength reduction factor, ϕ, of greater than 0.6 for SSWs as well as the diaphragms and foundations connected to them. In addition, a seismic response modification coefficient, R, of greater than 6 can be justified, which translates into a smaller seismic design base shear. These adjustments can ultimately lead to a more economical design of structures with SSWs.
10.14359/51737144
96-S60
July 1, 1999
Amin Ghali and Sami Megally
96
4
Brittle punching failure of flat plates can occur due to the transfer of shearing forces and unbalanced moments between slabs and columns. Design of connections of columns to flat plates to insure safety against punching failure is presented. This paper covers the design procedure in most practical situations, including interior, edge, and corner columns; prestressed and nonprestressed slabs; slabs with openings; and slabs with shear reinforcement. The ACI 318-95 Building Code requirements are adhered to where applicable. Numerical examples are presented to demonstrate the design procedure. Seismic design considerations are not discussed in this paper.
10.14359/690
90-S17
March 1, 1993
Adrian S. Scarlat
90
involves the presence of a rigid soil in the design of multistory buildings. The paper investigates the effect of neglecting the soil deformability on several rigidity-related aspects of the structural analysis of multistory buildings subject to lateral forces; the rigidity of structural walls and frames; the magnitude and distribution of seismic forces; the magnitude of torsional forces; and the stresses due to temperature changes. The results show that the "fixed support analyses" lead to important distortions of the rigidities and stresses. We have either to perform analyses by taking into account the soil deformability, or to perform "fixed support analyses" in which we have to decrease the rigidities of the structural walls by multiplying them by coefficients to be determined for each type of structure.
10.14359/4121
85-S37
July 1, 1988
R. W. Carlson and T. J. Reading
85
Shrinkage cracking is a widespread problem in concrete building walls. The stresses and resulting cracking are a function of the shrinkage and degree of restraint, most commonly from the foundation. A technique was developed for determining shrinkage stresses using rubber models. The values were checked by observing crack patterns in mortar models. Remedial measures were tried, and some gave encouraging results. A new ring test for the crack resistance of concrete was tried and showed promise.
10.14359/2666
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