Slab Reinforcement Research Articles

Structure behavior of reinforced concrete beam-slab assemblies subjected to perimeter middle column removal scenario

The perimeter columns of framed structures are more vulnerable to terrorist attacks due to accessibility. The beams and slabs above the damaged columns are the primary structural members to redistribute gravity load to avoid progressive collapse. Therefore, to investigate the structural behavior of reinforced concrete (RC) beam-slab assemblies against progressive collapse introduced by a perimeter middle column removal scenario, an experimental program and numerical analyses were carried out in this paper. Three 3/10 scaled specimens, each of which consisted of two square slab panels and seven beams, were tested with equivalent uniformly distributed loading (UDL) achieved by a 12-loading apparatus. High-fidelity finite element models were used to conduct parametric studies after the validation, recheck the validity of the loading apparatus and highlight the effect of loading positions. The concerned parameters include the geometric parameters of beams caused by different seismic design intensity, the slab thickness and reinforcement ratio, and the type of reinforcing bars (i.e. deformed and plain). The results indicate that progressive collapse is resisted by compressive arch action and flexural action of the beams and slabs connecting the stub above the removed column at small deformation stage, whereas catenary action of longitudinal beams and tensile membrane action of slabs are more prevailing at large deformation stage. Moreover, higher seismic design intensity results in a larger resistance at small deformation stage, and plain bars cause larger deformation capacity. Finally, loading positions approaching the stub above the removed column tends to show smaller structural resistance.

Numerical Analysis of the Impact of Thermal Spray Insulation Solutions on Floor Loading

The paper presents the effect of considering the substrate under the floor—insulation in the form of closed-cell polyurethane spray foam, which is used for insulating surfaces particularly exposed to mechanical impact. The layer of thermal insulation was made by spraying, which prevents the occurrence of thermal bridges due to tight filling of the insulated space. It seems extremely important to adopt the appropriate material characteristics of an insulating layer. The basic thermophysical properties of polyurethane foam justifying its choice as an insulation material were the values of its thermal conductivity coefficient (0.022 W/(mK)) and density (36 kg/m3). However, what was the most important for the calculations provided in the work was to determine the stiffness of the foam subgrade so as to assess its impact on the floor load capacity. The paper includes calculations for a floor slab characterized by a static diagram, with all edges free (unfixed), loaded in strips circumferentially. The reinforced concrete slab was 6 × 6 m long, 0.25 m thick, and made of C20/25 concrete resting on an elastic substrate. Calculations were made for two variants taking into consideration two values of subgrade stiffness. The first variant concerned the subgrade stiffness for sprayed polyurethane foam insulation. On the basis of laboratory tests in situ made according to the standard procedure, its average value was assumed as K = 32,000 kN/m3. The second, comparative, computational variant included the subgrade stiffness equal to K = 50,000 kN/m3. A variation approach to the finite difference method was used for static calculations, adopting the condition for the minimum energy of elastic deformation while undergoing bending that was accumulated in the slab resting on a Winkler elastic substrate. Static calculations resulted in obtaining the values of deflections at each point of the discretization grid adopted for the slab. The obtained results have proved the necessity of calculating the floor as a layer element. For the reference substrate with the subgrade stiffness K = 50,000 kN/m3 that was adopted in the work, the value of the bending moment was 17% lower than when taking into account that there was thermal insulation under the floor slab, causing an increase in the deflection of the slab and an increase in its bending moment. If a design does not include the actual subgrade stiffness of the layer under the floor slab, it results in an understatement of the values of the bending moments on the basis of which the slab reinforcement is designed. Adherence of insufficient concrete slab reinforcement may cause subsequent damage to floor slabs.

Shear Strengthening of Composite Concrete Steel Plate Girders with Web Openings Using Steel Strips

The study aims to investigate behaviour plus influence on the final load resistance of strengthen girders containing openings in web which were 40% of web height. This paper presents an experimental study of applying of five steel-concrete composite plate girder specimens that were loaded in shear predominantly. Three of those girders were considered as control girders, without web openings, containing circular web holes, and containing square web holes, respectively. Other two girders were strengthen girders. The slab reinforcement, dimensions of girders and compressive strength of concrete slabs were constant. Strengthening was made by using steel rings and strips which were welded to webs of strengthen girders to investigate influence of strengthening plan by steel welding on behaviour and final load strength for these girders. Findings illustrate increasing in final load strength of strengthen girders with circular and square web holes with about 57.38% and 43.75%, respectively in comparing to that for control girders. Moreover, the final shear capacity for the tested girders was also compared with that predicted by von Mises stresses.

Stresses, deformations and damages of various joints in precast concrete segmental box girder bridges subjected to direct shear loading

Precast segmental concrete bridges involve multiple concrete segments joined together by posttensioning, and have the advantages of rapid construction, low-cost, and excellent quality control. Joints that represent locations of discontinuity are prominent factors affecting overall structural behavior of segmental bridges. In this study, a comprehensive analysis is performed for thirteen tested specimens with different joint types, subjected to direct shear loading, to assess the shear behavior of joints in precast box girder segmental bridges. The analysis focused on understanding the role of prestressing force, concrete compressive strength, presence of epoxy, and number of shear keys on: the stress and strain level in reinforcing bars, prestressing strands, displacements, type, time and mechanisms of sequential cracking and of damage level in the joints. The results showed that increasing of the confining pressure to 4.5 MPa and/or number of shear keys from 6 to 10, can highly improve both of the elastic stiffness and the plastic ductility of the segmental bridges, and changes the brittle behavior of the epoxied joints to a gradual strength degradation mode; the relative displacement of the dry joints is double of that in their identical epoxied joint; and the strains in the top layer reinforcement of the top slabs for keyed joints are ten times higher than that in the flat joint specimens.

Numerical simulation of the dynamics of a reinforced concrete slab under an air shock wave

Deformation and fracture of a reinforced concrete slab under the effect of an air shock wave are considered. The research involves data from the public experiment "Blind Blast Test". The slab is loaded by an air shock wave resulting from high explosive detonation in a shock tube. The results of calculations and experiments are compared quantitatively and qualitatively. Quantitative comparison is made for the history of movement of the reinforced concrete slab key points during the process of deformation. Qualitative comparison is made for photographs of the destruction of a real reinforced concrete slab and distribution of the damage fields obtained by calculation. The numerical simulation is carried out in the LS-DYNA code, and the finite element method with an explicit time integration scheme is used. The CSCM (Continuous Surface Cap Model) model is used to model the concrete material. This model is an isotropic constitutive model with three-variant surface of ductility; the strength characteristics of the material depend on the rate of loading, and its damage is considered separately for compressive and tensile loads, which allows taking into account the partial recovery of compressive strength. The mathematical description of the model is given as part of the paper. Steel reinforcement of the concrete slab is modeled explicitly with beam finite elements. Finite element meshes of the concrete volume and reinforcing elements are coupled by means of the kinematic automatically calculated equations. The properties of the reinforcement are set within the classical theory of elastic-plastic strengthening material flow with the criterion of limiting states in the form of Huber-Mizes and taking into account visco-plastic effects. The influence of boundary conditions, practical mesh convergence, and capability of the mathematical model to predict the location of zones of material failure, displacement, and deformation of the structure are studied.

Flexural behaviour of concrete slabs reinforced with GFRP bars and hollow composite reinforcing systems

Glass Fibre Reinforced Polymer (GFRP) bars are now attracting attention as an alternative reinforcement in concrete slabs because of their high resistance to corrosion that is a major problem for steel bars. Recentlyhollow concrete slab systems are being used to reduce the amount of concrete in the slab and to minimise the self-weight, but the internal holes makes them prone to shear failure and collapse. A hollow composite reinforcing system (CRS) with four flanges to improve the bond with concrete has recently been developed to stabilise the holes in concrete members. This study investigated the flexural behaviour of concrete slabs reinforced with GFRP bars and CRS. Four full-scale concrete slabs (solid slab reinforced with GFRP bars; hollow slab reinforced with GFRP bars; slab reinforced with GFRP bars and CRS; and slab reinforced with steel bars and CRS) were prepared and tested under four-point static bending to understand how this new construction system would perform. CRS is found to enhance the structural performance of hollow concrete slabs because it is more compatible with GFRP bars than steel bars due to their similar modulus of elasticity. A simplified Fibre Model Analysis (FMA) reliably predicted the capacity of hollow concrete slabs.

Performance of Hollow Core Concrete Slab reinforced by embedded steel tubes

The aims of this paper are gaining additive knowledge about using steel tubes as reinforcement for hollow-core concrete slabs. For this purpose, this paper presents an investigation of how one-way concrete slabs would behave after embedding steel tubes within the cross section. Five concrete slabs were cast, these specimens differ from one another in the horizontal distance (spacing) between the two steel tubes placed within its cross section, steel tubes positioned in the center of the shorter lane of the specimen (width) which is 400 mm, the steel tubes spaced from each other with 4 different configurations, they were 0, 100, 200 and 300 mm. The ratio of the clear spacing between the two tubes and to the total width of the specimen is indicated (s/b) equal to (0, 0.25, 0.5 and 0.75). In addition to one solid slab cast and tested as a reference for the testing results. All five concrete slabs were loaded up to failure by submitting load at one point at the center of the slab. Only one variable was deemed to be considered and checked on this study which is the (s/b) ratio defined earlier. The results exhibit that, using steel tubes as reinforcement increase the first crack load by 12.75% compared to the reference slab, as well as increasing the ultimate load capacity by 59.02% compared to the reference slab. As for the mid-span deflection, the specimens with steel tubes embedded decreased the deflection values up to 47.37 %.

AN ASSESSMENT OF THE EFFECT OF CONSTRUCTION ERRORS DURING THE IMPLEMENTATION OF RC T-BEAMS

This paper investigates the effects of construction errors during the implementation of reinforced concrete T-beams. These errors are classified into two main sections. The first focuses on the position and ratio of reinforcing bars, while the other is related to the concrete strength. A total of ten specimens of T-beams were tested to assess the effect of the possible defects in the construction sites, viz. impact of misplacement of slab reinforcement, irregular arrangement of slab reinforcement, the change in bar diameter of slab reinforcement and the effect of casting method of concrete on the structural behavior of T-beam sections. The results indicated that the faulty placement of slab reinforcement leads to a lower bending moment capacity of the slab (brittle behavior) and the steel strain of slab decreases as the height of slab reinforcement decreases. The irregularity of the reinforcing bars in concrete slab affects the ultimate load carrying capacity of the slab. Also, it was found out that well-arranged distribution of reinforcement improves the ductile behavior of the slab and reduces the corresponding deflections.

Methods of calculation of reinforced concrete monolithic floors with hollow liners

Monolithic reinforced concrete slabs overlap with hollow liners have great advantages over traditional solid. Their use can reduce their own weight, reduce the load frame of the building, increase spans, improve heat – and sound conductivity will overlap. However, the implementation of such panels in construction is constrained by the lack of theoretical research and necessary regulatory framework for design. In the article the methods of analytical and numerical modeling in ITU complexes of slab work with hollow liners are examined. It is considered four possible methods of the computerized modelling of the floor slabs of the overlap with cross cavities in combination with full-bodied AREAS OF the plate using SP lira-Cad. The results of the efforts and displacements of the slice plate. It Is shown, that most adequately reflects the tense and deformed condition of the calculation 1 – overlap normalized cooker. This method is the simplest in terms of modeling complex architectural forms of overlap, has satisfactory similarity of results, allows to select necessary reinforcement using Postprocessors. This method is recommended for modelling the spatial work of the building frame, to assess the effort and reinforcement of the necessary slabs, frame elements and foundations.

Collapse of steel-concrete composite frame under edge-column loss—Experiment and its analysis

Previous studies on steel frames cannot consider the effect of concrete slabs on the collapse behavior of structures, while recent experimental studies on steel-concrete composite frames fail to fully mobilize the tensile membrane action in slabs and catenary action in beams which have great influence on the failure mode of the frame. Large-scale experiments are conducted in this study on steel frames with flat concrete slabs to investigate the resistance mechanisms and typical failure modes of the structure. An edge-column removal scenario is used to consider a worse condition than an internal-column removal case. The resistance-vertical displacement relationship at the column-removal location, horizontal displacements at the structural edges and final failure patterns of main structural components are reported. Parametric studies are conducted using a validated numerical model to further quantify the effect of concrete slab thicknesses, reinforcement diameters, and beam section dimensions on the collapse resistance of composite structures. A simplified calculation method is also proposed to predict the resistance-displacement curve of composite framed structures under an edge-column loss scenario. The experimental results show that even without external horizontal restraints, tensile catenary action and membrane action can significantly develop in the steel beams and concrete slabs, respectively, at large deflections of structures under an edge-column loss scenario. Positive yield lines are found to distribute diagonally in the slab extending from the column-removal location to the two corners of the slab, while negative yield lines elliptically distribute along the edges of the slab. The numerical results highlight that the contribution of tensile membrane action in concrete slabs to the collapse resistance is less significant than that of catenary action in steel beams. Moreover, increasing the section height of beams guarantees a greater plastic bearing capacity of composite structures, but it fails to always provide a larger ultimate bearing capacity due to a poorer ductility.

Torsional effects of a novel rebar stiffened cold-formed U-shaped steel-concrete composite beam system

Torsional effects of a novel rebar stiffened U-shaped steel-concrete composite beam (RCUCB) system are discussed in this paper, based on a series of torsional experiments. The rebar truss is welded on the top varus flanges of the open steel U-section to enhance its stability; The inverted U-shaped rebar is furnished to enhance the integral action between concrete slab and beam web; and the bottom rebar is installed to control the interface slip between concrete and steel. The test results reveal that the torsional failure mode of RCUCB is characterized by the critical inclined concrete cracks and crushed inclined struts of the slab, the cracking torsion ratio (ψcr,b) is 0.04–0.05ψu,b, the cracking torque capacity (Tcr) is 0.31–0.44Tu, and the secant stiffness at the ultimate load is 13–25% of the elastic stiffness. Additionally, some influencing factors are found: the elastic stiffness and cracking torque capacity increase with increasing slab width, slab thickness, and web depth; the ultimate torque capacity may be improved by increasing slab width, slab thickness, slab reinforcement strength, web depth, rebar truss, and inverted U-shaped rebars. Moreover, the concrete slab and beam web share a common torsion ratio provided that the inverted U-shaped rebars are adequate; and the crack width in the slab can be controlled by the torsion resisting ability of slab and the restraint action from the beam web. Lastly, design methods for elastic torsional stiffness, Tcr, and Tu of RCUCBs are proposed.

About the use of semi-continuity in simply supported composite steel and concrete beams, to remove fireproof coatings for standard-fire resistance requirement of less than 30 minutes

Abstract Previous studies of the behavior under fire conditions of composite steel and concrete beams, not subjected to local buckling (compact steel profile), showed that it’s not possible to justify, by design code methods, the absence of fire coating for 30 minutes standard-fire resistance requirement, even when considering the support rotational stiffness provided by the upper longitudinal slab reinforcement (semi-continuity). The purpose of this work is to verify the viability of this proposal for lower standard-fire resistance time, which, although rare, may occur with the use of the equivalent time method.

A Review of Design Methods of Transverse Reinforcement of Concrete Bridge Deck on Prestressed Girders

A review of current practices in designing the transverse reinforcement of concrete bridge slab supported by wide-flange prestressed-T girders is presented. Slabs are commonly assumed to be supported continuously at the center points of girders, neglecting the effect of the girder flange stiffness. The design in this manner may produce conservative transverse reinforcement of the slab. As alternative a newly constructed bridge deck is chosen as a case study where the design based on this conservative assumption is compared with that considering the girder flange length, thickness and rigidity. The results of these two designs are compared. It is found that the amount of transverse reinforcement of the concrete slab obtained from the conventional design is considerably larger than that considering the girder flange stiffness. This promising finding warrants further investigation of the latter approach focusing on the effect of girder flanges in taking bridge loading in the transverse direction.

Effects of high temperature on residual punching strength of slab-column connections after cooling and enhanced post-punching load resistance

Large-scale experiments were conducted on six isolated slab-column connection specimens. Each specimen contained a 300 mm square center column and a 150 mm thick slab. The objectives of the experiments were to study the effects of fire-induced high temperatures on the residual punching shear strength of reinforced concrete flat-plate structures after cooling and to examine the effectiveness of a detailing approach for enhancing the post-punching load-carrying capacity. Ceramic fiber heating panels were used to apply high temperatures to slab shear-critical regions at the compressive face. The test results indicate that the high temperatures up to 800 °C did not seriously impact connection punching shear strength. Moreover, the use of crossties can effectively engage slab tensile reinforcement in resisting post-punching loads with a loading capacity close to or even greater than the punching failure load. Complementary to experiments, finite element simulations were conducted. The numerical simulations predicted the punching failure load of slab-column connections at room temperature with a good accuracy; however, the simulations underestimated the post-heating punching strength of the cooled slab-column connections by up to 11%.

Behaviour of continuous reinforced concrete floor slabs subjected to different compartment fires

This paper presents the experimental results of four continuous reinforced concrete slabs with three compartments under different compartment fire scenarios. The research focuses on the quantitative relationships of the compartment fire temperatures, the temperature distribution along the thickness of the slabs, the vertical and horizontal deflections, the crack patterns and failure modes of the slabs and the corners’ reaction forces. The results indicate that for a continuous floor slab, the central vertical deflection of the slab in the middle compartment is considerably affected by the vertical deflections of the slab in the two edge compartments. The boundary condition, the ratio and arrangement of the top reinforcement of the continuous slab, and the fire spreading scenarios have important effects on the failure mode of the slab in different compartments. It is evident that more severe cracking happened within the slab in the middle compartment compared to the two edge compartments. For the edge compartment, the slab may fail by large deflection and the integrity failure of the slab in the middle compartment may occur. Increasing reinforcement ratio and using the continuous reinforcement are the effective methods to prevent or delay the failure of the continuous slabs with any fire spreading scenarios.

ANALYSIS OF POWER SUPPORT BEHIND PILE AND GIRDER BRIDGE ABUTMENT RANDUMERAK LOAD ON VERTICAL AND HORIZONTAL

Construction of pile foundations is also called a foundation in construction enabled to heavy loads (high rise building). Before the implementation of the construction of the first construction is implemented and carried out in the field is the work of the foundation (bottom structure). Foundation work itself is very important for civil engineering works, because this is the foundation that secures simultaneously carry the load working on the construction. This study aimed to analyze the carrying capacity and the forces acting on the pile working from the Standard Penetration Test (SPT), the data kalendering pile installation time, then the data terbebut in include into the application to determine how far the resilience of construction are already working. Methodology The data collection is done by making observations, collecting data from the project and conduct a literature study. From the analysis of the structure obtained by the forces at work in the use of the calculation of the structure. The calculations show that the pile cap and slab reinforcement in accordance with the moment that occurs, the strength and bearing capacity of the pile meet safety requirements.

Behaviour Of Bamboo Reinforcement In Flexural Strength Of Sea Water Concrete Slab

World Resources Institute data shows that there will be a fresh water crisis in 2040 including Indonesia. Responding to the above, many studies have been carried out using seawater, one of which is on concrete. Several studies have shown that seawater does not reduce the quality of concrete, but provides a corrosion effect on reinforcement. In this study, sea water concrete slabs have been made using bamboo as a reinforcement that will not corrode due to seawater. For concrete mix design refers to SNI SNI 03-2834-2000 and for slab flexural strength refers to 03-2847-2002. Slab specimens with sea water concrete that have been made consist of Slab concrete of steel reinforcement (SCS), Slab concrete of bamboo reinforcement V type notch (SCBV) and Slab concrete of bamboo reinforcement U type notch (SCBU). The result of the compressive strength of sea water concrete can reach the compressive strength of the plan. Tensile strength of bamboo reaches 223.5MPaand approaching the tensile strength of steel reinforcement. The maximum load of SCBV and SCBU were decrease than theoretical analysis of0.14% and 21.51% respectively. Otherwise, the maximum load of SCS greater than theoretical analysis with a difference of 14.67%. The flexural strength of the concrete slab was not affected by sea water as in compressive strength of cylinder. Keywords : Bamboo reinforcement slab, Flexural strength, Seawater concrete

Slab corner effect on torsional behaviour of perimeter beams under missing column scenario

Perimeter beams in reinforced-concrete buildings are subjected to considerable torsion from slab negative bending moments. In the event of progressive collapse caused by column removals, torsion effects on such beams become critical, owing to redistribution of loads. The aim of this study is to explore the effects of slab corners on the torsional behaviour of perimeter beams in reinforced concrete beam–slab buildings, particularly in the case of column loss. A series of torsional tests on peripheral beams was conducted, comparing cases with and without slabs. Thereafter, physics-based numerical models were developed, based on the test results, to investigate the effect of varying the slab's parameters, such as thickness and reinforcement ratio, on torsional capacity. The models showed that the presence of reinforced concrete slabs could increase the torsional strength of perimeter beams by as much as 97%. The enhancement came first from the slab corner, which acted as a set of compressive struts. This effect increased with increasing slab thickness. It was also observed that the slab corners tend to shift torsional failure (which occurred at the twisted beam near the support) to about one beam depth away. The contribution of negative bending moment from slab reinforcement along the edges could also enhance overall structural capacity.

Experimental measurement of the diameter and cover depth of steel reinforcement using an electromagnetic concrete cover meter

In spite of the fact that concrete cover meters are some of the most commonly used non-destructive means of measuring reinforcement diameter, position, and cover, there are barely any specific measurement results available in published literature. This paper focuses on the use of a Profometer PM-630 concrete cover meter for in-situ measurements of such things as the cover depth of stirrups in the column of a high-rise building or determining the diameter of main reinforcement in hollow-core ceiling slabs.

Tests and analysis of RC building, with or without masonry infills, for instant column loss

Abrupt loss of a ground story column was experimentally simulated on a 0.8:1-scaled model of a 2 × 3 bay, two-story concrete building with masonry infills along the perimeter of the second story. Three cases were investigated in the infilled building: loss of a column at a corner of the building, inside the plan area or at the perimeter; loss of the perimeter column was also studied with the infills removed and the weight on the model structure increased, to simulate a third story. In general, there was almost no visible damage after each test, neither in the concrete structure nor in the infills. Residual diagonal cracks were visible at the bottom face of slabs, starting from the removed interior column, and especially from the removed exterior column in the repeat test without infills; after the additional load on the floors had been removed, these cracks were not visible anymore. The excellent performance even without the infills is due to the continuity of the bottom bars of beams through the beam/column joints and to the placement of two-way top and bottom reinforcement throughout the slabs, continuous across the supports on beams. During the quasi-stationary free vibration stage that followed column removal, the accelerations measured on the slabs adjacent to the column being removed exceeded only marginally the acceleration of gravity upwards and downwards. This confirms that it is good practice to place two-way top reinforcement in slabs, as well as to use a magnification factor of 2 on the gravity loads of these slabs in pushdown analyses performed to investigate loss of column incidents. Numerical simulation of the tests was successful as far as the prediction of the residual deflections and the decay of vertical vibrations are concerned, but could not capture the high frequency features of the transient vibration.