Search

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this research, the load-deflection behavior is explored for concrete beams reinforced with FRP bars (polymer reinforcement). An experimental test is done for a total of five beams subjected to 4-point loading. The tested specimens are of dimensions; 2100 mm (length), 200 mm (width) and 300 mm (depth), while the used compressive strength for concrete is f’c = 60 MPa. Four beams were longitudinally reinforced by various CFRP rebar numbers, and the last beam was reinforced only by steel bars as control beam. Relationships for load-deflection were drawn and the influence of several factors was debated on this relationship. It was exhibited that the failure of FRP reinforced samples was generally ruled by the concrete strength. When the ratio of reinforcement rising by 50%, 100% and 150%, the ultimate load increased by 15%, 29% and 38%, respectively, while the recorded deflection at ultimate load decreased by 7%, 16% and 24%, respectively. For the ultimate load of the studied beams, outcomes exhibited that the equations of the American code ACI 440.1R give very close values with the test values, while they give very conservative values to the deflection at ultimate load which are smaller than the test values by about (37%-45%).

Reinforced concrete (RC) slabs are characterized by reduced construction time, versatility, and easier space partitioning. Their structural behavior is not straightforward and, specifically, punching shear strength is a current research topic. In this study an experimental database of 113 RC slabs without shear reinforcement under punching loads was compiled using data available in the literature. A sensitivity analysis of the parameters involved in the punching shear strength assessment was conducted, which highlighted the importance of the flexural reinforcement that are not typically considered for punching shear strength. After a discussion of the current international standards, a new proposed model for punching shear strength and rotation of RC slabs without shear reinforcement was discussed. It was based on a simplified load-rotation curve and new failure criteria that takes into account the flexural reinforcement effects. This experimental database was used to validate the approaches of the current international standards as well as the new proposed model. The latter proved to be a potentially useful design tool. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on bearing capacity of polyvinyl chloride (PVC) carbon fiber-reinforced polymer (CFRP) confined reinforced concrete columns with ring beam joint (PCRBJs) under axial load. All PCRBJs conform to the principle of "strong-column/weak-joint". Four parameters including stirrup ratio, reinforcement ratio, height, and width of the ring beam are considered. Test results demonstrate that the ultimate bearing capacity of PCRBJs increases with stirrup ratio, reinforcement ratio, or ring beam width increases, while it decreases as ring beam height increases. On the basis of the local compression theory, as well as in accordance with confined concrete theory, the concept of gradual superposition of the confinement of multiple annular steel bars on core concrete is adopted, an effect coeffi- cient of joint height is introduced, and a model for predicting the ultimate bearing capacity of PCRBJs is proposed. The predicted results agree well with test data. [ABSTRACT FROM AUTHOR]

In this paper, seven specimens were designed to study the influence of the height (h), width (b), and reinforcement ratio (ρ) of ring beam on the failure mode, bearing capacity, deformation, and equivalent stress–strain relation of joint core reinforced with ring beam for connection of polyvinyl chloride fiber‐reinforced polymer confined concrete column and reinforced concrete beam. The experimental results indicated that the crushing of concrete in the joint core dominated the failure of specimens. The ultimate, yield bearing capacity and axial strain decreased with the increase of height, while raised with the improvement of width or reinforcement ratio. The growth of the strains of reinforcement and concrete accelerated with the increment of height, while decelerated with the rise of width or reinforcement ratio. Subsequently, based on the local compression theory, confined concrete theory, and the principle of superposition of multiple confinement, considering the influence coefficient of joint height βh and the enhancement coefficient of stirrups αs, a new formula was proposed to estimate the ultimate bearing capacity of specimens under axial local compression. Then, on the basis of Mander's model, taking the correction parameter η into consideration, a new model of equivalent stress–strain relationship was established. Verification results showed that the models proposed in this research agreed well with the experimental results. [ABSTRACT FROM AUTHOR]

The target reliability index for the assessment of an existing flexural element depends on the warning of failure provided and therefore on the total deflection at incipient failure. Sensitivity analyses accounting for both the linear-elastic-cracked and plastic responses indicate that the warning of failure depends on the ductility of critical cross sections (and therefore on the flexural reinforcement ratio) and the length of the plastic hinge regions (and therefore on the applied load configuration). Structural redundancy typically reduces the total deflection at incipient member failure and therefore is an inconsistent indicator of warning of failure. The deflections at incipient failure can be normalized as fractions of the span length to quantify the Warning Factor, W, as a function of the reinforcement ratio, span length, and effective beam depth. This continuous variable can replace existing discretized values of the Warning Factor based on somewhat subjective classifications of ductility and redundancy. [ABSTRACT FROM AUTHOR]

The flexural behavioral properties of ultra high performance concrete (UHPC) low-profile T-beams reinforced with a combination of steel fibers and steel reinforcing bars were investigated in this paper. Five large scale T-beams were tested and analyzed regarding their deflection, ductility, strain, curvature, load capacity and crack development. The experimental variables include the reinforcement ratio, the slenderness (length to diameter ratio) of the fiber reinforcements, and the fiber type. The experiments showed that all specimens exhibit flexural failure with the yielding of steel bars and excessive expansion of flexural crack, and the compression zone in the reinforced UHPC low-profile T-beam is not crushed because of the ultra high compressive strength and area of UHPC. In addition, it was concluded that using hooked-end fibers can effectively increase the specimen's durability-based cracking load in comparison to straight fibers of same slenderness, whereas the reinforcement ratio and the slenderness of the fibers have little influence on this. Increasing the reinforcement ratio and using hooked-end instead of straight fibers increase the load capacity and bending stiffness of the specimen, as well as reduces the crack width at comparable applied load. A model was established to compute the ultimate capacity of UHPC low-profile T-beams and the prediction agrees well with the experimental results in the present and published investigations. [ABSTRACT FROM AUTHOR]

One type of failure of reinforced concrete seismic walls is out-of-plane buckling. This type of failure appears at the compressive cycle of loading during the cyclic seismic loading. This work is mainly experimental and tries to investigate the influence of the mechanical factor of tensile deformation on the behavior of seismic walls and particularly on the phenomenon of lateral buckling. Five test specimens are constructed simulating the confined boundary regions of structural walls. They are reinforced using the maximum longitudinal reinforcement ratio (4.02%) prescribed by modern seismic and concrete codes for boundary ends. Apart from the investigation of the factor of elongation degree, this method tries to examine if the detailing of walls using maximum allowable reinforced ratio for longitudinal reinforcement inhibits the appearance of transverse buckling. Each prism specimen was strained under different tensile deformation. Degrees of elongation used were equal to 0‰, 10‰, 20‰, 30‰ and 50‰. After the first tensile cycle of loading, a second compression loading cycle was applied on each specimen, till their failure. Thus, nine experiments were carried out in total-two for each specimen apart from the first specimen which suffered zero elongation. Empirical equations are derived trying to estimate the ultimate bearing capacity and the normalized axial deformation at failure for the different tensile degrees. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) slabs may be exposed to the low-velocity impact load during their service periods. In low-velocity impact scenarios, the effect of strain rates has been remarkably higher than quasi-static loading because the loading duration is very short. Thus, structural responses and failure modes will be different. The present study aims to investigate dynamic response and failure modes of simply supported two-way RC slabs exposed to low-velocity impact load. In the experimental part of this study, nine RC slabs with the dimension of 1,000 × 1,000 × 80 mm were tested. The reinforcement ratio of RC slabs and the input impact energy applied to RC slabs were experimental variables investigated. A drop-weight test setup was utilized to apply impact load to RC slabs. By varying drop-height as 1,000, 1,250 and 1,500 mm, three different impact energies have been applied to RC slabs via a hammer of which weight is 84 kg. The time histories of the accelerations, displacements and impact loads were recorded. The dynamic responses obtained by tests and the failure modes observed has been interpreted in detail. Besides, a finite element model where explicit dynamic analysis is performed has been established for verification of the experimental results. There was observed good accordance between numerical and experimental results. Consequently, it is considered that the present finite element treatment can be used for the evaluation of the dynamic responses and failure modes of RC slabs exposed to low-velocity impact load. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

After using Ultra-High Performance Concrete (UHPC), the mechanical properties of the composite beams have significant differences compared to those of the steel-normal concrete composite beams. To investigate the effect of reinforcement ratio on the force behavior of steel-UHPC composite beams, tests on the flexural performance of steel-UHPC composite beams with different reinforcement ratios under negative moments were carried out, and reasonable design of the composite beams was analyzed by using a numerical simulation method. In addition, the existing crack calculation methods for composite beams were validated. The results showed that the failure modes of the composite beams with different reinforcement ratios were similar. Increasing the reinforcement ratio from 2.01% to 2.98%, the ultimate capacity of the steel-UHPC composite beams was increased by 4% and the ultimate deflection was reduced by 7%, while the ductility was reduced by 11%. The cracking load was not enhanced, but the higher reinforcement ratio had a controlling effect on crack development and crack width in the late loading stage. For steel-UHPC composite beams, the appropriate reinforcement ratio should be less than 4%. Furthermore, the crack calculation formulas in the existing steel-concrete composite beam codes do not apply to steel-UHPC composite beams, and the calculation results were much smaller than the measured values. Among the related formulas for reinforced UHPC members, the calculated value of the formula in NF P 18–710 was closer to the measured value but the overall error was still large, so further research is needed. • Compares the flexural behavior of stee-UHPC composite beams under negativebending moment. • Analyzes the effect of reinforcement ratio on the development of cracks and the width of the main cracks. • Investigates the appropriate reinforcement ratio of steel-UHPC composite beams. • Investigates the variation in the contribution ratio of UHPC tensile strength during the loading process. • Compares and verifies the existing formulas for cracking of composite beams. [ABSTRACT FROM AUTHOR]

• Punching-shear strength of GFRP reinforced precast concrete tunnel lining (PCTL) segments. • Effects of concrete strength and GFRP reinforcement ratio on punching behavior of PCTL. • Punching-shear failure mechanism of PCTL reinforced with GFRP bars. • Deformability and energy absorption of PCTL reinforced with GFRP bars. • Design Equations to predict punching-shear strength of GFRP reinforced PCTL. While assessing the load cases is crucial for designing the precast concrete tunnel lining (PCTL) segments, none of the tunnel-specific standards or codes explicitly consider punching-shear loads. This study aimed at determining the structural performance of full-scale precast concrete tunnel segments reinforced with glass fiber-reinforced polymer (GFRP) bars. The segments were constructed with a rhomboidal shape measuring 2100 × 1500 × 250 mm and subjected to point loading on their extrados surfaces until failure. Such loading simulates the geotechnical exposure conditions surrounding tunnels, such as rock expansion. The effects of concrete strength and GFRP flexural reinforcement ratio on the punching behavior were analyzed and are discussed herein. The load–deflection response, failure mode, punching strength, cracking behavior, reinforcement and concrete strain, deformability, and energy absorption were all evaluated in the experiments. The results reveal that increasing both the flexural reinforcement ratio and concrete strength enhanced the punching response and decreased crack width. In addition, using HSC in tunnel segments yielded higher pre-cracking stiffness, punching-shear capacity, and energy absorption. A theoretical investigation involving a comparison between predictions of the FRP-reinforced concrete slab design provisions and experimental results was performed to assess the applicability of the current punching equations for PCTL segments. The equations in the FRP-reinforced concrete codes predicted the punching capacities conservatively, while the researchers' proposed equations overestimated. Moreover, CAN/CSA S806-12 showed the most accurate prediction of the punching capacity even if the concrete compressive strength exceeded 60 MPa. [ABSTRACT FROM AUTHOR]

• The dynamic equilibrium relationship of the three forces is analyzed. • The distribution of acceleration for the longer and thicker slabs shows a sinusoidal trend. • The slab stiffness by varying slab length and thickness obviously affects the reaction force. • The slab stiffness by varying slab thickness and rebar ratio affects the deformation. • The semi-empirical formulas are proposed to predict the reaction force time history. The purpose of present study is to investigate the effect of global stiffness on the force response of thin GFRP reinforced concrete slabs simply supported by steel beams under drop-weight impact. Considering the strain rate effect of GFRP bars and concrete materials, a numerical model of GFRP-RC slabs was established and verified. The dynamic equilibrium relationship of the impact force, reaction force and inertial force was analyzed and intuitively explained from the velocity and displacement. Meanwhile, the effects of the global stiffness by varying the slab length, slab thickness and reinforcement ratio on the acceleration distribution, characteristic value of impact force and reaction force, failure pattern, displacement distribution and energy dissipation were evaluated in more detail. Eventually, the semi-empirical formulas considering key parameters were proposed to predict the reaction force time history of simply-supported RC/FRP-RC slabs under drop hammer impact. The results show that the effect of the slab stiffness by varying the slab length and thickness on the reaction force is significant, while the influence of reinforcement ratio is not obvious. The effect of global stiffness of the slab on the plateau value of the reaction force is similar to that on the plateau value of the impact force. The effect of the slab stiffness by varying the slab thickness and reinforcement ratio on the displacement is obvious, while varying the slab length hardly affects the deformation. The fitting equation considering key parameters can predict the simplified reaction force time history of simply-supported RC/FRP-RC slabs under impact loading. However, more experimental validation and extensive parametric studies are needed to improve their accuracy and applicability. [ABSTRACT FROM AUTHOR]

In order to investigate the transverse flexural behavior of the UHPC waffle deck, a total of six T-shaped UHPC beams, with varying longitudinal reinforcement ratios, were tested and analyzed. The experiments, including material tests of UHPC and beam tests, were conducted. The material tests of UHPC revealed that strain-hardening behavior in tension was exhibited, and the ratio of uniaxial compressive strength-to-cubic compressive strength was 0.85. The beam tests showed that all the T-shaped UHPC beams, even without longitudinal rebar, exhibited ductile behavior that was similar to that of properly reinforced concrete beams. As the longitudinal reinforcement ratio increased, more flexural cracks developed and a larger load-carrying capacity was provided. Furthermore, the sectional analysis for the ultimate flexural capacity of T-shaped UHPC beams was conducted. Simplified material models, under tension and compression, for UHPC were developed. Based on the reverse calculation from the experimental result, the relation between reduction factor to the ultimate tensile strength of UHPC, and longitudinal reinforcement ratios was formulated. As a result, the predictive equations for the ultimate flexural capacity of T-shaped UHPC beams were proposed, and agreed well with the experimental results in this study and existing studies, which indicates good validity of the proposed equations.

Deteriorated concrete cover, e.g., spalling or delamination, especially when it occurs at the web of a reinforced concrete (RC) beam within the shear span, can reduce the shear capacity of the beam. Patching of this deteriorated area may be the best option to recover the shear capacity of the beam affected. For this purpose, unsaturated polyester resin mortar (UPR mortar) has been formulated. This research aims to investigate the efficacy of UPR mortar in limiting the shear cracking and so restoring the shear capacity of the deteriorated RC beam. The investigation is carried out by an experimental and numerical study. Two types of beams with a size of 150 × 250 × 1000 mm were prepared. The first type of beams was assigned as a normal beam. The other was a beam with a cut off in the non-stirrup shear span, which was eventually patched with UPR mortar. Two reinforcement ratios were assigned for each type of beams. The results show that UPR mortar is effective to hamper the propagation of diagonal cracks leading to increase the shear failure load by 15–20% compared to the reference (normal) beam. The increase of shear strength with the use of UPR mortar is consistently confirmed at various reinforcement ratios.

The contribution is focused on quantifying model uncertainty of crack width estimates for reinforced concrete beams. Predictions obtained by the model provided by the fib Model Code 2010 are compared with results of tests of beams having different longitudinal and shear reinforcement ratios and concrete cover. Trends of model uncertainty with basic variables are investigated.

Various concretes have been developed to meet the principles of sustainability. High volume fly ash-self compacting concrete (HVFA-SCC) is one example. The utilization of HVFA-SCC for structural applications, however, raises a concern among designers: that HVFA-SCC may not be as strong as conventional concrete when carrying shear forces. This concern is related to slow strength development and relatively smoother crack surface formation in HVFA-SCC, which, consequently, reduces the aggregate interlock mechanism contribution to the shear strength. In this respect, the design code for estimating the shear strength of HVFA-SCC may not be valid for the reason that the code was developed on the basis of the conventional concrete database. Previous research on the shear strength of HVFA-SCC was limited and no database can be extracted to justify the validity of the shear design code. This research was conducted to clarify the suitability of shear design code for HVFA-SCC. The research began with a limited laboratory investigation, followed by a numerical investigation to expand the range of results. Two types of HVFA-SCC beams with dimensions of 100 mm × 150 mm × 1700 mm were prepared, utilizing 50% and 60% fly ash. The shear behavior obtained from the laboratory investigations was then numerically modeled with the help of 3D ATENA Engineering software. The numerical model was used to explore the influence of reinforcement ratio, shear span to beam effective depth ratio, and beam size on the shear strength of the HVFA-SCC beam. The results were compared with the shear strength database of conventional and unconventional concrete beams to judge if the provisions in the design code can be applied to the shear design of an HVFA-SCC beam. The results confirm that the ACI shear design code is applicable for HVFA-SCC.

The feature of reinforcing bars is introduced into dynamic cavity-expansion theory. Based on the elastic–plastic response penetration model of plain (i.e., unreinforced) concrete (Forrestal and Tzou, 1997), a dynamic spherical cavity-expansion penetration model for reinforced-concrete targets is developed with consideration of the circumferential restriction effect derived from reinforcing bars in the crushed region. The theoretical solution and simplified calculation formula for the cavity radial stress in incompressible and compressible reinforced concrete are obtained by introducing a reinforcement ratio as the volume fraction of rebars in the concrete target. A damping function is presented to describe the restriction effect of a single layer of reinforcing bars on the surrounding concrete, thus establishing a model to calculate the penetration resistance of multilayer reinforced-concrete targets. Compared with test data for the penetration depth, this model considering the circumferential restriction effect produces better results compared with the existing theory. [ABSTRACT FROM AUTHOR]

Highlights • Slenderness limit concept is generalized to incorporate crack width limitations. • Slenderness limits incorporate the main parameters influencing serviceability. • Cracking and long-term effects are accounted for through simplified coefficients. • Good agreement when comparing to a non-linear time-dependent analysis. • Slenderness limits are a useful tool for performance-based design of RC structures. Abstract The use of high strength materials allows flexural members to resist the design loads or to cover long spans with a reduced depth. However, the strict cross section dimensions and reinforcement amount required in ULS are often insufficient to satisfy the serviceability limit states. Due to the complexity associated to a rigorous computation of deflections and cracks width in cracked RC members along their service life, an effective way to ensure the satisfaction of the SLS is to limit the slenderness ratio l / d of the element. In the present study, the slenderness limit concept, previously used for deflection control, is generalized to incorporate the crack width limitations in the framework of structural performance-based design. Equations for slenderness limits incorporating the main parameters influencing the service behaviour of RC members are derived. Cracking and long-term effects are accounted for through simplified coefficients derived from structural concrete mechanics and experimental observations. The proposed slenderness limits are compared with those derived from a numerical non-linear time-dependent analysis for two case studies, and also with those obtained using the EC2 procedure for deflection calculation in terms of constant applied load and constant reinforcement strain. Very good results have been obtained in terms of low errors and scatter, showing that the proposed slenderness limits are a useful tool for performance-based design of RC structures. [ABSTRACT FROM AUTHOR]

Abstract A hollow concrete column (HCC) is a structurally efficient construction system and uses less material. Conventionally, HCCs are reinforced with steel bars, which are prone to corrosion. This study explored the use of glass-fiber-reinforced-polymer (GFRP) composite bars as reinforcement for HCCs and evaluated the effect of the reinforcement ratio on HCC structural behavior. A total of six HCCs reinforced longitudinally with GFRP bars with different reinforcement ratios (1.78%, 1.86%, 2.67%, 2.79%, 3.72, and 4.00%) were prepared and their behavior was investigated. The different reinforcement ratios were achieved by changing the bar diameter (12.7 mm, 15.9 mm, and 19.1 mm) and number of bars (4, 6, 8, and 9 bars). The results show that increasing the diameter and number of bars enhanced the strength, ductility and confinement efficiency of HCC. For columns with equal reinforcement ratios, using more and smaller-diameter GFRP bars yielded 12% higher confinement efficiency than in the columns with fewer and larger-diameter bars. The crushing strain of the GFRP bars embedded the HCC was 52.1% of the ultimate tensile strain. Lastly, the axial-load capacity of the GFRP-reinforced HCC can be reliably predicted by considering the contribution of the concrete and up to 3000 μ ε in the longitudinal reinforcement. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The direct tensile response of reinforced HyFRC (R/HyFRC) is investigated. • R/HyFRC strengthening is dependent on strain-hardening rebar and softening HyFRC. • Rebar reinforcement ratio and fiber type can affect R/HyFRC strengthening. • Single dominant crack localization occurs in R/HyFRC at low reinforcement ratio. • R/HyFRC has greater tensile load capacity and lower strain capacity than R/C. Abstract While the properties of hybrid fiber-reinforced concrete (HyFRC) have been well-reported in the literature, the behavior of reinforced HyFRC (i.e., HyFRC with embedded steel rebar) is less understood. This paper investigates the mechanics and failure characteristics of reinforced HyFRC under direct tension. Samples with a low longitudinal steel reinforcement ratio were studied to evaluate the feasibility of reducing rebar congestion in structural applications through the use of fiber-reinforced concrete. Although reinforced HyFRC forms multiple cracking sites when loaded, rebar strain and HyFRC crack opening are generally concentrated at a single location under post-yield displacements. The onset of rebar plastic deformation and the exhaustion of fibers' bridging load capacity are coincident events at a dominant crack. For a cracked reinforced HyFRC section to strengthen, the magnitude of load resistance increase from strain hardening rebar must exceed the magnitude of load resistance decrease from fiber pull-out processes. Comparisons are made with studies reported in the literature to demonstrate how longitudinal reinforcement ratio and fiber type influence cracking behavior and ultimate strain capacity. The research presented herein has far-reaching impacts on the structural design of all types of reinforced fiber-reinforced concrete materials detailed for a ductile response under large displacements. [ABSTRACT FROM AUTHOR]

Effects of slab flexural reinforcement on the punching shear strength and deformation capacity of corner slab-column connections without shear reinforcement were evaluated in this study. Four isolated corner slab-column subassemblages were tested under combined gravity-type loading and lateral displacement reversals. Results from present and previous studies indicate that provisions per ACI 318-14 are not conservative for corner slabcolumn connections. For connections subjected to gravity-type loads only, a shear strength model considering effects of the equivalent slab top flexural reinforcement ratio and the critical section aspect ratio (bo/d) is proposed. For connections subjected to combined gravity-type loads and lateral displacement reversals, this proposed shear strength model provides a more conservative estimate of gravity shear ratio when applied to shear decay model per ACI 318-14. [ABSTRACT FROM AUTHOR]

Abstract The study of failure mechanism of reinforced concrete subjected to high-energy projectile impact loading has important significance to accurately evaluate the impact resistance of structures and reasonably design and construct engineering structures. In this study, experiments in which high-speed (>1000 m/s) projectiles impact 1000-mm-thick slabs of reinforced concrete were performed and the damage of the reinforced concrete slabs were measured. Then, an analytical model of the characteristics of reinforced concrete subjected to projectile impact loading is constructed. The principles of energy conservation and minimum potential energy are used to formulate explicit equations for the perforation performance of reinforced concrete. These theoretical predictions agree with our experimental results and with similar published studies. Furthermore, in the context of our model, the effects of impact velocity, concrete compressive strength, and reinforcement ratio on the perforation performance of reinforced concrete are discussed. Highlights • High-speed projectile perforations of reinforced concrete experiments are performed. • An analytical model of projectile perforation of reinforced concrete is proposed. • Theoretical predictions agree well with experimental results. • Effects of analytical model parameters on perforation performance are discussed. [ABSTRACT FROM AUTHOR]

A general criterion is proposed as a supplement to the most recent ACI 318 Code. The proposed criterion applies to slabs with or without prestressing having vertical or inclined legs of stirrups or headed shear stud reinforcement in a crucifix layout. Yielding of the top flexural reinforcement in a zone above a column can induce punching. This flexure-induced punching can occur when a pattern of yield lines develop a local mechanism. To avoid punching, a minimum amount of top flexural reinforcement is generally required. The structure may be subjected to gravity loads and lateral forces due to wind or earthquake. For the universal design, shear and flexural reinforcements should first satisfy the requirements of an applicable code, then verify that the zone and amount of top flexural reinforcement in two orthogonal directions are adequate. [ABSTRACT FROM AUTHOR]

A new type of composite voided slab, the TUBEDECK (TD), which utilizes the structural function of profiled steel decks, has recently been proposed. Previous studies have confirmed that the flexural strength of TD slabs can be calculated based on the full composite contribution of the steel deck, but for long-span flexural members, the deflection serviceability requirement is often dominant. Herein, we derived a novel deflection prediction approach using the results of flexural tests on slab specimens, focusing on TD slabs. First, deflection prediction based on modifications of the current code was proposed. Results revealed that TD slabs exhibited smaller long-term deflections and at least 10% longer maximum span lengths than solid slabs, indicating their greater efficiency. Second, a novel rational method was derived for predicting deflections without computing the effective moment of inertia. The ultimate deflections predicted by the proposed method correlated closely with the deflection under maximum bending moments. To calculate immediate deflections, variation functions for the concrete strain at the extreme compression fiber and neutral axis depth were assumed with predictions in good agreement with experiments. The proposed procedure has important implications in highlighting a new perspective on the deflection prediction of reinforced concrete and composite flexural members.

In this study, the response quantities affecting the equivalent yield curvature, which is important in the deformation-based seismic design and assessment of structural systems, are investigated for reinforced concrete columns with a square cross-section. In this context, the equivalent yield curvatures were determined by conducting moment–curvature analyses on various column models, in which the axial load level, cross-section dimension, longitudinal reinforcement ratio, and concrete compression strength were changed parametrically, and the independent and/or combined effects of the relevant parameters were discussed. Depending on the axial load levels of P/Agfc′ < 0.3, P/Agfc′ = 0.3, and P/Agfc′ > 0.3 for the considered columns, the yielding of reinforcement, yielding of reinforcement and/or concrete crushing, and concrete crushing governed the yield conditions, respectively. It can be noted that the cross-section dimension and axial load level became the primary parameters. Even though the independent effects with regard to particular parameters remained at minimal levels, the combined effects of them with the axial load became important in terms of the equivalent yield curvature.