Showing papers in "Aci Structural Journal in 1990"
462 citations
232 citations
121 citations
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TL;DR: In this paper, the performance of four half-scale interior joints with respect to joint shear stress and beam bar anchorage lengths is described, and the tests indi cate that the current ASCE-ACI Committee 352 recommendations are adequate to provide ductility and energy dissipation capacity.
Abstract: The performance of four half-scale interior joints with respect to joint shear stress and beam bar anchorage lengths is described. The main variable in the tests was the column depth, which was changed to produce anchorage lengths of 16, 20, 24, and 28 bar diameters. The half-scale specimens were subjected to a large number of cycles in the elastic and inelastic range. Cycling in the elastic range indicated that severe bond deterioration can occur even at this level if the anchor age is short. Cycling in the inelastic range indicated an interaction between anchorage length and joint shear stress level. The tests indi cate that the current ASCE-ACI Committee 352 recommendations are adequate to provide ductility and energy dissipation capacity. The latter, however, depends strongly on the anchorage length as the de terioration in hysteretic behavior can be large if short anchorages are used.
86 citations
TL;DR: In this article, the authors describe the test results from 6 large pile caps that failed in 2-way shear and find that ACI Building Code procedures for the shear design of pile caps are unable to predict the experimental results because the procedures neglect certain important parameters, such as the amount of longitudinal reinforcement, and overemphasize other parameters such as effective depth.
Abstract: The paper describes the test results from 6 large pile caps that failed in 2-way shear. ACI Building Code procedures for the shear design of pile caps are unable to predict the experimental results because the procedures neglect certain important parameters, such as the amount of longitudinal reinforcement, and overemphasize other parameters, such as the effective depth. Strut-and-tie models were found to describe more accurately the behavior of deep pile caps.
84 citations
TL;DR: In this paper, a truss-model-based design procedure is developed for transversely reinforced slabs, and its application is illustrated for the case of a large transfer plate in a high-rise building.
Abstract: To supplement conventional design methods, this paper reviews mechanisms of transverse shear transfer in reinforced concrete slabs. A truss-model-based design procedure is developed for transversely reinforced slabs, and its application is illustrated for the case of a large transfer plate in a high-rise building.
75 citations
TL;DR: In this paper, a nonlinear material model for cracked reinforced concrete subjected to inplane shear and normal stresses has been developed and a set of constitutive equations suitable for incremental finite element analysis is derived.
Abstract: A nonlinear material model for cracked reinforced concrete subjected to inplane shear and normal stresses has been developed. As a result, a set of constitutive equations suitable for incremental finite element analysis is derived. Features of the present model include the smeared crack representation, rotating crack approach, tension stiffening, stress degrading effect for concrete parallel to the crack direction, and shear retention of concrete on the crack surface. This material model has been tested against the experimental data of Vecchio and Collins and it has been demonstrated that this material model is adequate in describing the post-cracking behavior of reinforced concrete.
74 citations
TL;DR: In this article, a design method was presented to predict the punching strength and deflection of flat plates at interior columns. Failure is assumed to occur when the compression zone of the slab in the vicin...
Abstract: The paper presents a design method to predict the punching strength and deflection of flat plates at interior columns. Failure is assumed to occur when the compression zone of the slab in the vicin ...
73 citations
TL;DR: In this article, the effects of loding history and repair methods on the structural characteristics of reinforced concrete walls were investigated and it was found that, while repairing only the damaged regions of the compressive zone was sufficient to fully restore wall strength, the additional use of epoxy resins to heal major flexural and inclined web cracks led only to a marginal improvement of the structural properties of the original walls.
Abstract: The effects of loding history and repair methods on the structural characteristics of reinforced concrete walls was investigated. Large scale slender wall models were tested to failure, then unloaded, repaired, and retested to destruction under various regimes of cyclic horizontal loading. It was found that, while repairing only the damaged regions of the compressive zone was sufficient to fully restore wall strength, the additional use of epoxy resins to heal major flexural and inclined web cracks led only to a marginal improvement of the structural characteristics, the latter being distinctly inferior to those of the original walls. Such results are in compliance with the concept of the compressive force path and demonstrate that, in contrast to widely held views, the compressive zone is the main contributor to shear resistance.
TL;DR: In this paper, a simple equation based on previous experimental results is derived to define the softening characteristics of the concrete, and can be used to compute deflections, and the effect of the resultant tensile force location and magnitude on the overall respnse of the structure is demonstrated in flexural members with low percentages of reinforcement.
Abstract: The different parameters that influence the tension stiffening of reinforced concrete are critically examined. A simple equation based on previous experimental results is derived to define the softening characteristics of the concrete, and can be used to compute deflections. Reinforcement parameters, such as bar diameter, reinforcement spacing, and cover affect the numerical coefficients in the equation describing the falling branch of the concrete component. Incorporating these material nonlinearities in the tension and compression zones of a 2-zone model, moment-curvature relations are developed. The analytical resutls are verified by comparison with test data. The effect of the resultant tensile force location and magnitude on the overall respnse of the structure is demonstrated in flexural members with low percentages of reinforcement.
TL;DR: In this paper, the effect of member span-depth ratio on the predicted steel stress f sub ps in unbonded prestressed concrete members at their nominal moment resistance is implemented in an approximate manner of ACI 318-83.
Abstract: The effect of member span-depth ratio on the predicted steel stress f sub ps in unbonded prestressed concrete members at their nominal moment resistance is implemented in an approximate manner of ACI 318-83. The recognition of member span-depth ratio and its implementation as an independent design parameter was made based on comparison of limited experimental results. However, there is not yet a clear phenomenological explanation that helps in understanding the mechanism of this parameter and its level of influence on the predicted f sub ps at ultimate flexural strength.
TL;DR: In this paper, the authors present the results of an experimental investigation relating punching shear to concrete strength and steel ratio and conclude that shear capacity is proportional to the cube root of concrete strength.
Abstract: This paper reviews recent research and code provisions on punching shear capacity and its relation to concrete strength It presents the results of an experimental investigation relating punching shear to concrete strength and steel ratio The paper concludes that shear capacity is proportional to the cube root of concrete strength and steel ratio and that the ACI-CSA code provisions should be reviewed
TL;DR: In this paper, two interior reinforced concrete subassemblages (PI and VI) were subjected to a series of cyclic lateral loads to simulate moderate earthquake damage and then repaired with one of two epoxy repair techniques: pressure injection (RPI) or vacuum impregnation (RVI).
Abstract: Two test series were conducted to determine the effectivenes of epoxy techniques to repair moderate earthquake damage. Two interior reinforced concrete subassemblages (PI and VI) were subjected to a series of cyclic lateral loads to simulate moderate earthquake damage. The specimens were then repaired with one of two epoxy repair techniques: pressure injection (RPI) or vacuum impregnation (RVI). The repaired specimens RPI and RVI were then subjected to the same load history as that imposed on the original test specimens (PI and VI). The restoration of bond between the reinforcement and concrete in the joint was of particular interest. Both techniques worked well in restoring the strength, stiffness, energy-dissipation capacity, and bond of the specimens. The vacuum impregnation technique may have an advantage in the repair of large regions of damage and offshoot cracks.
TL;DR: In this article, the inelastic buckling and load-carrying capacity of reinforcing steels in concrete columns are studied by an accurate finite element method, and a critical tie spacing exists for reinforced steels under monotonic loading.
Abstract: The inelastic buckling and load-carrying capacity of reinforcing steels in concrete columns are studied by an accurate finite element method. A critical tie spacing exists for reinforcing steels under monotonic loading. The peak lods for cases with a spacing below and above the critical spacing differ greatly. Below the critical spacing, the tangent modulus theory used in previous works of tie spacing and tie stiffness determination may be applied; above the critical spacing, the theory may not be expected to predict the load-carrying capacity accurately. The critical spacing varies with the shape of the stress-strain curve of the reinforcing steel. A parametric study is carried out to establish the range of critical spacing for typical high strength steels.
TL;DR: The results of an experimental investigation of the punching shear strength of reinforced concrete slabs with varying span-depth ratios are summarized in this paper, where 10 axisymmetric slabs were tested.
Abstract: The results of an experimental investigation of the punching shesr strength of reinforced concrete slabs with varying span-depth ratios are summarized. Ten axisymmetric slabs were tested. The slab thickness was kept constant while the support diameter was varied to produce different span-depth ratios. The punching shear strength was found to significantly increase as the span-depth ratios decreased below 6. Maximum test strengths were nearly 5 times greater than the 1983 ACI Building Code predicted strengths. The higher strengths were a result of smaller span-depth ratios, in-plane compressive forces caused by restraining action at the supports, and excellent anchorage provided for the shear reinforcement.
TL;DR: In this article, the behavior differences of these types of connections with respect to strength, ductility, stiffness, energy dissipation, and bond deterioration at the joint core are discussed.
Abstract: An experimental investigation was conducted to study the behavior of semirigid precast beam-column connections subjected to simulated seismic forces. Four full-scale interior beam-column assemblies representing a portion of a frame subjected to simlated seismic loading were tested, including one monolithic specimen and 3 precast specimens. The behavior differences of these types of connections with respect to strength, ductility, stiffness, energy dissipation, and bond deterioration at the joint core are presented and discussed. Test data showed that properly designed precast beam-column connections maintained ductility and strength and exhibited excellent energy capacity when subjected to large inelastic deformations under load reversals.
TL;DR: In this paper, the influence of a full range of variables on EI of slender reinforced concrete (RC) columns bent in symmetrical single curvature under short-time loads was investigated.
Abstract: The ACI Building Code permits a moment magnifier approach for design of slender reinforced concrete (RC) columns. This approach is strongly influenced by the effective flexural stiffness EI of the column which varies due to cracking, creep, and nonlinearity of the concrete stress-strain curve, among other factors. However, the EI expressions given in the ACI Building Code are quite approximate when compared with the values of EI derived from thrust-moment-curvature relationships. This study was undertaken to determine the influence of a full range of variables on EI of slender tied rectangular RC columns bent in symmetrical single curvature under short-time loads. Approximately 9500 columns, each with a different combination of variables, were used to generate the stiffness data. The EI expresions were then statistically developed for use in slender column designs. Two sets of equations are proposed in this paper; (a) Eq. 21 through 23 for initial sizing and preliminary design of structures; and (b) Eq. 18 through 20 for use in final more accurate structural designs.
TL;DR: In this paper, the deflection ductility of flat plates with different types of shear reinforcement is tested and a combination of bent bars and stirrups, even at reinforcement reinforcement, is used.
Abstract: The deflection ductility of flat plates with different types of shear reinforcement is tested. Excellent performance is achieved with a combination of bent bars and stirrups, even at reinforcement ...
TL;DR: In this article, the authors present rules to design and detail stud-shear reinforcement in accordance with the 1989 ACI Building Code (ACI 318-89) and three numerical examples illustrate the design of shear studs and their distribution in slabs in the vicinity of interior, edge, and corner columns transferring axial force V and bending moment M.
Abstract: Extensive tests presented earlier have establidhed the effectiveness of stud-shear reinforcement in increasing the punching-shear strength and ductility of slab-column connections transfering axial force V and bending moment M. The shear reinforcement is composed of vertical rods mechanically anchored at their top and bottom ends. This paper presents rules to design and detail stud-shear reinforcement in accordance with the 1989 ACI Building Code (ACI 318-89). Three numerical examples illustrate the design of shear studs and their distribution in slabs in the vicinity of interior, edge, and corner columns transferring V and M. Because of effective anchorage, design rules that reduce the amount of shear reinforcement are suggested and applied. Rules for the design according to the Canadian standard CAN3-A23.3-M84 are also given.
TL;DR: In this article, a method to calculate the strength of reinforced concrete slender columns in braced frames is presented, based on a simplified stability analysis of a standard pin-ended column, including the creep defelection due to sustained loads as an additional eccentricity.
Abstract: A method to calculate the strength of reinforced concrete slender columns in braced frames is presented. It is based on a simplified stability analysis of a standard pin-ended column. The method includes the creep defelection due to sustained loads as an additional eccentricity. The strengths calculated by the proposed method show good correlation with 80 test results reported in the literature. When compared with the proposed method, the slender-column provisions contained in the ACI Building Code are found to be conservative. Based on the method, proposals for design are made and illustrated by an example.
TL;DR: The flexural and shear behavior of reinforced masonry shearwalls subject to both monotonic and cyclic lateral loads is examined in this article, based on the experimental results obtained from more than twenty 6 x 6 ft reinforced wall panels tested under inplane vertical and lateral loads.
Abstract: The flexural and shear behavior of reinforced masonry shearwalls subject to both monotonic and cyclic lateral loads is examined. The study is based on the experimental results obtained from more than twenty 6 x 6 ft reinforced masonry wall panels tested under in-plane vertical and lateral loads. For the square wall panels studied, the shear strength is initially provided by the diagonal compression strut mechanism, and later by the interface shear as well as the resistance of the horizontal reinforcement. A simple shear formula, based on the latter and proposed in a prior study, appears to be reliable. In general, wall panels that failed shear exhibited a more brittle behavior than those that failed in flexure. Furthermore, based on experimental data, an empirical formula governing the degradation of shear strength under cyclic displacement reversals is developed.
TL;DR: In this article, the application of load balancing in a broader context as the emerging standard for analyzing post-tensioned buildings is reviewed and the governing relationships are introduced and discussed.
Abstract: The paper reviews the application of load balancing in a broader context as the emerging standard for analyzing post-tensioned buildings. Terminology, concepts, and current procedures used in the extended scope of load balancing are presented and the governing relationships are introduced and discussed. The redistribution of elastically computed moments due to limited joint plastification is examined and numerical examples illustrate the application of load balancing to more complex structures and the importance of faithful representation of balanced loading.
TL;DR: In this paper, an efficient model for inelasitc biaxial bending interaction of reinforced concrete sections is presented based on a rate-dependent viscoelastic equation.
Abstract: The paper presents an efficient model for inelasitc biaxial bending interaction of reinforced concrete sections. Based on a rate-dependent viscoelastic equation, it is shown that the model is extremely versatile and has the capability to incorporate stiffness and strength decay. The model also enables identification of the physical nature of interaction and achieves a controlled hysteretic behavior. Only uniaxial information is required for the material parameters that describe the model. Unlike other conventional reinforced concrete models, loop tracing is necessary, thereby making it simple, efficient, and readily suitable for use with large computational models for analyzing reinforced concrete building structures. The validity of the proposed scheme is demonstrated through the analytical simulation of available biaxial experiences on reinforced concrete columns and comparison with other analytical models.
TL;DR: In this article, the authors investigated shrinkage cracking behavior of thin mortar walls with continuous base restraint and found that the base restraint showed a significant effect on the crack width and spacing.
Abstract: This work investigated shrinkage cracking behavior of thin mortar walls with continuous base restraint. Reduced-scale wall models were subjected to natural drying conditions to determine the effects of the horizontal and vertical (dowel) reinformcement, as well as the effects of wall length and height and length-height ratio on crack width and spacing. The base restraint showed a significant effect on the crack width and spacing. Smaller crack spacing in base restrained members were obtained for the same amounts of volume change and steel ratio, and compared with end-restrained members. Crack spacing proved to be related mainly to the combined effects of the horizontal reinforcement and wall height. On the other hand, a variation in crack width along the wall heights was observed. this variation proved to be related to the amount of change in restraint in the wall associated with its cracking. Finally, adopting the change-of-restraint principle, a formula has been suggested for the prediction of maximum crack width at any position along the wall height.
TL;DR: In this article, a model was developed to determine the yield and ultimate behavior of reinforced concrete beams strengthened by concrete overlays, and the results of a parametric study showed that thick overlays on the compression side of heavily reinforced beams can increase shear making the bond between the beam and overlay especially critical.
Abstract: A model was developed to determine the yield and ultimate behavior of reinforced concrete beams strengthened by concrete overlays. The overlay may be on the compression or tension side (in which case it is reinforced). The behavior at the interface between the overlay and the beam is simulated by a shear spring with a bilinear shear-slip-relationship. The model was evaluated by comparing analytical results with the test data obtained for 14 beams. A reasonably close agreement between the calculated and measured moments and yield displacements was noted. The results of a parametric study showed that thick overlays on the compression side of heavily reinforced beams can increase shear making the bond between the beam and overlay especially critical.
TL;DR: In this article, a trilinear moment-curvature curve is constructed by depicting each of uncracked, cracked, and yielded behavior of reinforced concrete beams as linear segments.
Abstract: A trilinear moment-curvature curve is constructed by depicting each of uncracked, cracked, and yielded behavior of reinforced concrete beams as linear segments. This curve and Branson's well-known formula for effective stiffness are qualitatively related to each other, and as a result the difference between predictions by the two models is inherently bounded. Moment-curvature and load-deflection curves derived by Branson's formula and a recent nonlinear model by Bazant and Oh have been compared with those produced by the trilinear model for several example beams. Good agreement is observed among these models. The main advantage of the trilinear model is in computer applications related to analysis and design of reinforced concrete beams and frames.
TL;DR: In this paper, the effect of the presence of a floor slab on the behavior of beam-column connections was studied by testing two-bay frame subassemblies, where each subassembly consisted of two exterior connections and an interior connection.
Abstract: 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.
TL;DR: In this paper, three large-scale reinforced concrete portal frame models were subjected to combinations of thermal and mechanical loads, including unrestrained thermal deformation, restrained deformation under shock thermal loads, and loading to ultimate capacity.
Abstract: Three large-scale reinforced concrete portal frame models were subjected to combinations of thermal and mechanical loads. Test conditions included unrestrained thermal deformation, restrained deformation under shock thermal loads, and loading to ultimate capacity. Aspects of response were monitored in terms of resulting restraint forces, deflection, strains, cracking, and leakage. Test results indicated that thermal loads can result in significant stressing of a structure and can lead to concentrated damage in local regions. A proposed theoretical analysis procedure was found to give reasonably accurate predictions of response.