Slab Reinforcement Research Articles

DESAIN JEMBATAN T-GIRDER PADA SUNGAI JALAN ANTARA MENGGUNAKAN SNI 1725 2016

Bridges are part of the national transportation system that has an important facility. In Putri Sembilan Village, Rupat Utara District, there is a very important bridge where this bridge is the only alternative for residents of Putri Sembilan Village to the fishing port and plantation. The current condition of the bridge has been damaged with wood material that has been decayed and hollow. For this reason, a new bridge was planned using reinforced concrete structures. This plan refers to SNI 1725-2016 concerning the loading of bridges and SNI T-12-2004 concerning the planning of concrete structures for bridges in the hope of obtaining a bridge structure that is safe and in accordance with applicable standards. The design consists of bridge slabs, sidewalks, stamped plates, girder beams and diaphragm beams. As the result, the main reinforcement slab D16-200 mm and D13-300 mm are obtained. Reinforcement direction extending the stamp plate obtained reinforcement D16-200 mm while for the transverse obtained D16-250 mm. For the main reinforcement girder beam obtained 28D32 mm, compressive reinforcement used 8D32 mm reinforcement and shear reinforcement used Ø13-100 mm reinforcement. While the main reinforcement of the diaphragm beam using 3D16 mm and shear reinforcement obtained Ø13-200 mm reinforcement.

Solving the problem of unilateral contact of the slab with the strengthening beams by the method of variational approximations

The work is devoted to the numerical-analytical solution of the contact problem when reinforcing the floor slab with beams using the mathematical apparatus of generalized functions. Such tasks arise during the reconstruction of existing buildings, when reinforcement of floor slabs is required to increase their bearing capacity under load. The contact of a slab with reinforcing beams is considered for various types of one-sided local restrictions on its deflections. To solve the structurally nonlinear problem of contact interaction between the slab and the reinforcement beams, a stepwise loading method is used in combination with the method of variational approximations. At each loading step, to ensure the convergence of the desired function of the plate deflections from the action of local contact forces of the beams resistance, the procedure of the method of variational approximations is used. Based on the use of the mathematical apparatus of generalized functions and the use of the method of variational approximations with the help of a stepwise algorithm, numerical-analytical solutions for the problem of contact interaction of an elastic plate with reinforcement beams are obtained. Two types of elastic one-way connections were considered: discrete supports and support along rectilinear segments. Due to the rational choice of approximating functions that describe with a high degree of accuracy the irregular parameters of the considered constructive-nonlinear system while keeping a small number of members of the series, a higher calculation accuracy is achieved in comparison with computational complexes that implement numerical methods of strength calculation of the indicated building structures.

Calculation of the composite timber­reinforced­concrete bending elements considering the nonlinear work of the joint

A method has been proposed to calculate the composite timber-concrete bending elements taking into consideration the non-linear work of a nail joint and the stretched reinforcement in a slab. An acting building code regulates the structure estimation based on the linear-elastic work while the pattern of the joint's deformation under loading demonstrates a pronounced non-linear character. Estimation formulae do not account for the presence of reinforcement in a concrete slab, which leads to the irrational use of the structure's load-bearing properties.A dependence has been proposed to determine the slip modulus. The determining coefficients are computed based on the rated characteristics given in the acting design standards.An algorithm for calculating the composite timber-concrete bending structures has been given, taking into consideration the deformation diagram of the joint and reinforcement in the stretched zone of a concrete element.It has been established that the normal stresses for the considered variants of timber-concrete beams, determined on the basis of the proposed procedure and the linear-elastic model, differ by 1‒8 %. At loads corresponding to plastic deformations, those stresses that were estimated in line with the linear-elastic model prove to be understated. At loads exceeding 0.75 kN/m for the beam with a span of 3 m, and 0.5 kN/m for the beam with a span of 5 m, stresses in the stretched region of a concrete slab exceed the concrete stretching strength while the stresses in a timber beam do not reach the ultimate values. In fact, in this case, the structure's load-bearing capacity is underutilized because the stretching effort in the cross-section with a crack is accepted by the reinforcement.Based on the design features of timber-concrete floors (the thickness of a slab and protective layer), an analysis of the load-bearing capacity considering the reinforcement has been performed. It has been established that the load-bearing capacity of a slab ensures that an estimated bending momentum is tolerated up until the loads that cause the destruction of the timber beam. At the same time, the conditions for the rational operation of compressed concrete and stretched reinforcement are met

NUMERICAL STUDY ON ANCHORAGE ZONES OF POST-TENSIONED SLAB CONSIDERING ANCHORAGE DEVICE

The integrity of Post-Tensioned (PT) concrete slabs is highly dependent on the design of the anchorages zone and the anchorage system used. Using new anchorage devices may require much experimental testing, particularly when we need to examine several parameters. This research aims to numerically investigate the stresses at anchorage zones when using a new anchor device. To that aim, a 3D finite element model for the slab and the anchor device was established using a finite element program. The numerical modelling technique and parameters were verified using the results of experimental work from literature. Anchorage device transversal ribs, ties around the device, and reinforcement in the end block slab were examined to study their effect on the end block stresses. It was found that the studied parameters have a considerable impact on the behaviour of the end block. Also, numerical modelling was successful in studying anchorage zones stresses when using new anchorage devices.

Effect of load level of corner columns on punching shear resistance of flat slabs

The problem related to the effect of the corner column load on the punching shear resistance of the slab was presented. Existing experimental studies on internal columns demonstrated that the column pressure could lead to an increase in the punching shear resistance. Because of different confinement conditions of corner column-slab connection joints, it is unclear if such an effect exists for corner columns. New experimental investigations were initiated to clarify this issue. They covered a total of three corner column-slab connection specimens – slabs with a thickness of 140 mm and a longitudinal reinforcement ratio ρl = 1.09% connected with columns of a cross-section of 200×200 mm. The only variable parameter was the column load equal to 500, 1000 and 1500 kN.
 A reduction of the slab load-carrying capacity of about 9% due to a three-fold increase in the column load was noted. Therefore, the effect of the column load turned out to be opposite to that observed for most previous tests on internal column-slab connections, which could have a result of a limited capacity of the slab reinforcement due to additional tensile forces from the lateral expansion of joint concrete.
 Comparison in the light of test results demonstrated, that EN 1992-1-1 procedure allowed for safe, yet conservative estimation of the punching shear resistance. An average ratio of experimental to theoretical load of 1.82 was obtained.

Flexural Behavior of Reinforced Concrete Slabs Reinforced with Innovative Hybrid Reinforcement of Geogrids and Steel Bars

This paper aims to innovate a hybrid reinforcement system for concrete slabs, consisting of geogrids and steel bars, by conducting an experimental comparative study between using different types, tensile strengths, and layers of geogrids as additional reinforcement to steel bars in comparison to conventional steel-reinforced concrete control slab. These concrete slabs were tested under a four-point loading system until they failed due to bending. As an addition, strain gauges were attached to the concrete slabs bottom reinforcement (geogrids and steel bars) to provide a close examination of geogrids and steel bars as a hybrid reinforcement system. Results show that the innovated hybrid reinforcement system of uniaxial geogrids and steel bars more preferred as concrete slabs reinforcement as it provided more benefits values (including, but not limited to, initial-peak load, steel-yield load, post-peak load, displacement ductility index, and energy absorption capacity) and more efficient utilization (including, but not limited to, higher benefits to cost values and better flexural performance) than the case of using conventional reinforcement of steel bars and the cases of using triaxial geogrids as additional reinforcement to the steel bars; however, triaxial geogrids provide lower deflection values and higher first-crack load values.

Novel Approach to Inspections of As-Built Reinforcement in Incrementally Launched Bridges by Means of Computer Vision-Based Point Cloud Data

The paper presents inspection and assessment of as-built reinforcement of a selected segment of an incrementally launched (IL) concrete bridge under construction. Two novel techniques were used for data acquisition: modified photogrammetry and High Definition Surveying - a combination of terrestrial-based laser scanning, computer technology and precision control networks. The main goal of this in-situ experiment was to develop a practical, effective, yet affordable methodology for inspecting reinforcement of the above mentioned structures. In order to maintain the requirements resulting from the specifics of IL technology (seven-day cycles, 24/7 operation, two concrete pours per week), the authors have limited the maximum allowed time for data acquisition, minimized the complexity of measurement data processing and related requirements for the software and computers, and replaced the professional equipment for photogrammetry with a commonly available SLR camera. Data obtained using this method was than referred to the point cloud model obtained with a precise, state-of-the-art 3D laser scanner. The adopted mathematical model for data post-processing turned out to be effective and correct both for the analysis of data from laser scanners and photogrammetry. Presented solution adopts practical workflow with camera calibration to simplify in-situ measurement procedure achieving high accuracy standards required for reinforcement inspection. The point cloud data model obtained from photogrammetry turned out to be insufficient to assess web reinforcement thoroughly. In turn, it was possible to inspect and evaluate the reinforcement of the bottom slab, with accuracy matching the laser scanning.

Nonlinear finite element analysis of full-scale concrete bridge deck slabs reinforced with FRP bars

Bridges with reinforced concrete deck slabs are more vulnerable to environmental-induced deterioration mainly due to corrosion. Carbon and glass fiber reinforced polymer (FRP) bars are getting attention as an alternative to steel bars to enhance the overall performance of the concrete bridge deck slabs and minimize corrosion-induced deteriorations. This study presents a 3D nonlinear finite element analysis (NLFEA) simulating the response of full-scale concrete bridge deck slabs reinforced with FRP bars. A control slab model was developed initially and properly calibrated and validated against published independent experimental results. A parametric study was then conducted through creating 27 NLFEA models with different parameters: concrete compressive strength, reinforcement type (glass FRP, carbon FRP, and steel), and bottom transverse reinforcement ratio. Monotonic single concentrated load was applied at the center of the concrete deck slab over a contact area of 600 mm × 250 mm, simulating the footprint of sustained truck wheel load. The CFRP and GFRP bars reinforcement of bridge deck slabs had superior effects on the ultimate load, elastic stiffness, post cracking stiffness, elastic energy absorption and post cracking energy and a little impact on ultimate deflection compared with steel reinforcement. Punching shear failure with a very similar cracking pattern was observed almost in all slabs and the bottom transverse reinforcement ratio is the main parameter affecting the tensile strains. For all slabs reinforced with GFRP and CFRP bars, the maximum measured strains in the bars at failure were less than 50% of their ultimate strain. Increasing concrete compressive strength will increase the ultimate load capacity and corresponding deflection of the slab.

Shear-bending failure modeling of concrete ribbed slabs strengthened with UHPFRC

The use of Reinforced Ultra High Performance Fiber Reinforced Cementitious Composite (R-UHPFRC) materials in the strengthening of existing infrastructure has been more broadly exploited in recent years, although the main domain of application pertains to the rehabilitation of bridge slabs. In this work, the method is extended to the reinforcement of the ribbed slabs of an iconic building, situated in Zurich, Switzerland, where an increase on shear and bending capacity has been deemed necessary. Due to the uncertainties relating to the properties of the existing concrete, dated from 1913, laboratory tests were conducted on four specimens, for verifying the efficacy of the proposed strengthening solution. As a result of the experimental campaign, a novel analytical model for R-UHPFRC and Reinforced Concrete T-beams has been developed, which was validated with the help of a Finite Element (FE) simulations.

Analysis of slab action on the seismic behavior of external RC beam-column joints

The correct evaluation of beam flexure capacity is of paramount importance in the capacity design process of reinforced concrete (RC) frame structures. Even though few experimental studies on beam-column joints have considered the presence of slab, its action as a tension flange in modifying beam-column strength hierarchy has been clearly found. This is mainly due to the increased hogging moment capacity of beams. Nevertheless, European and Italian seismic codes do not explicitly consider slab action as tension flange nor indicate proper values for effective slab width.To better understand this action, an accurate 3D finite element model has been calibrated based on the results of past experimental tests carried out on a full-scale beam-column joint. Afterwards, the calibrated model has been equipped with a portion of the adjacent spandrel beam and slab in order to evaluate their effect on the beam-column connection's behavior through numerical analyses. Alike previous studies, numerical results show that the tension flange effect of slab can significantly increase hogging (negative) moment in beams framing into beam-column joints. Additionally, it has been found that this effect is a function of slab steel amount, also highlighting the role of slab reinforcement orthogonal to the beam. Based on the above, practical indications have been provided for the evaluation of hogging moment in beams specifically concerning effective slab width to be considered in resisting moment calculations as a function of slab steel amount.

Implementation of GPR and TLS data for the assessment of the bridge slab geometry and reinforcement

Implementation of GPR and TLS data for the assessment of the bridge slab geometry and reinforcement

Experimental study on seismic behaviour of composite frames with wide floor slabs considering the effect of floor loads

The steel–concrete composite frame systems are widely used in multistory and high-rise buildings owing to good mechanical performance and high construction efficiency. In previous research on the composite frame systems, many lateral cyclic tests were conducted on specimens with small-width floor slabs without floor loads, which could not precisely reflect the actual behaviour of composite frames in spatial multistory buildings. Therefore, this paper presents an experimental study on the seismic behaviour of composite frames with wide floor slabs considering the effect of floor loads. The specimen was a two-story two-span composite frame with the scale ratio of 0.5, and three load cases, including the vertical floor loading test, the lateral cyclic loading test and the pushover test, were respectively applied to investigate the mechanical performance of the composite frame. The slab crack development, mid-span deflection and strain distribution of slab reinforcements in the vertical floor loading test were discussed. The overall responses of the specimen in the lateral cyclic loading test and pushover test were analysed, including failure phenomena, load–displacement curves, strength and stiffness degradation, energy dissipation capacity and deformation characteristics. Moreover, the seismic performance of columns, beams, slabs and joints in the specimen was discussed in detail and the force mechanism of the composite frame was revealed based on the structural analysis of components. The results indicated that the specimen exhibited sufficient load-bearing capacity, good ductility, stable strength and stiffness degradation and excellent energy dissipation capacity under the combination of vertical floor loads and lateral loads. The welds at the bottom flange near the exterior joint fractured under cyclic loading, which was found to have significant influence on the deformation pattern and force mechanism of the composite frame. The shear lag effect was obvious in the wide floor slabs and the effective width of the slabs was estimated to be nearly 0.75 times the column width.

Structural performance of jointed reinforced concrete pavement slab with subbase erosion

Structural behavior of jointed reinforced concrete pavement (JRCP) slab is sensitive to the subbase erosion which is considered in pavement design as a potential failure mode. However, erosion of subbase has not been clearly addressed in the JRCP design specifications. The most widely used procedures for the design of pavement slabs is specified in the Guide for Design of Pavement Structures (AASHTO 1986, 1993, and 2008). In this study a simple but effective 2D finite element (FE) structural response model is proposed and utilized to examine the effect of subbase erosion on the JRCP slab performance. The FE model considers different JRCP slab thicknesses and dimensions and different subbase erosion scenarios. The results of the proposed FE model indicate that considering the subbase erosion in JRCP slab design may require a substantial increase in slab reinforcement; however, it can lead to less damage and longer lifespan of the pavement slab.

A new method for dynamically estimating long-term seepage failure frequency for high concrete faced rockfill dams

Failure frequency of a dam varies greatly with reservoir water level and time. It is important but difficult to dynamically estimate failure frequency of high concrete faced rockfill dams (CFRDs) merely based on the probabilistic approach due to limited failure cases of high CFRDs. In this study, a new method is developed for dynamically estimating the long-term revolution of seepage failure frequency of high CFRDs by combining an analogical approach with the Bayesian approach. A simple and precise seepage generalized method and a parameter named defect parameter are introduced to provide the basis of comparison between the dam of interest and the accumulated database of high CFRDs. Using the cumulative probability distribution from the database, the correlation between annual seepage failure frequency and defect parameter is established. A high CFRD case in China with an operation history of slab breakage and reinforcement is selected as an example to illustrate the applicability of the new method. It is verified that the variation tendency of safety level of high CFRD is well simulated through the annual seepage failure frequency calculated by the newly proposed method.

Potential use of coconut stem as reinforcement in concrete slab

The utilization of an economical, eco-friendly, renewable building material has gained the attention of researchers lately. The construction sector is responsible for depleting large quantities of non-renewable resources. This activity not only generates millions of tons of mineral waste but millions of tons of carbon dioxide gas emissions as well. Research is thus needed on building materials based on renewable resources such as vegetable fibres. Investigated was on the possible use of coconut stem strips as reinforcement in concrete paste. The coconut stem was cut into various lengths, diameter, treated and coated with gloss paint and coal tar. Various tests in accordance to standard were conducted to determine the performance of the coconut stem strips. Compressive strength test and impact load tests were carried out on the concrete slab specimens to satisfy the desire of incorporating coconut stem as reinforcement in concrete slab. The compressive strength was performed on a large number of concrete cubes; 3 cubes each for day 7, 14, 21 and 28. As regards the impact loads test, 13 slabs were cast, 3 slabs each containing steel, dried coconut stem strips, gloss painted coconut stem strips, coal tar coated coconut stem strips with varying dimensions of 16 × 15 mm, 20 × 15 mm and 25 × 15 mm and plain slab without reinforcement serving as control. As expected, the slab reinforced with steel showed better strength in the cured state; however, the 2% of the coconut stripes reinforcement treated with coal tar would serve as good as the conventional steel reinforcement for normal concrete. The coal tar can be used for low-bearing load structures such as lintel and pavement.

Effect of Rib Geometry in Steel–Concrete Composite Beams with Deep Profiled Sheeting

Presented are the results from a finite element model of steel–concrete composite beams with deep decks and a comparison with various analytical/design methods. Using a deck deeper than 80 mm are becoming popular with a desire for longer spanning capability and lower concrete volume. However, there are no design rules in either American or European design codes for using a deck deeper than 80 mm, as both codes limit the deck rib height to 75 and 85 mm, respectively for using the stud’s capacity formula. Therefore, research is needed to establish the design stud capacity in beams with decks deeper than 80 mm. After extensive validation, the 3-D FE model is used for a parametric study with tests having decks deeper than 80 mm. The parameters include rib geometries, studs’ layout and concrete slab reinforcements. The FE results showed that stud capacity with narrow and deep decks (100–150 mm) is about 70% of the conventional decking (60–80 mm deep). The stud capacities from the numerical results were compared to the predicted strengths from the design/theoretical models. While the equations from the concrete pull-out failure mode by Johnson and Yuan (Proc Inst Civ Eng Struct Build 128(3):252–263, 1998) gave reasonable predictions with a coefficient of variation as 11%, both EC4 and ANSI/AISC rules provided inaccurate and inconsistent predicted strengths. A generalised stud capacity formula should be developed in the design codes for decks deeper than 80 mm.

Numerical model of beam-to-column composite connection between slim floor system and composite column

Abstract The slim floor system has been used mainly due to the structural and constructive advantages of it, such as the capacity to overcome large spans with the low height of the composite floor system. There is a lack of finite element modelling researches of composite connections between the slim floor system and columns, especially with the concrete infilled steel tube columns. This paper presents the numerical approach based on the solid modelling, for the simulation of the nonlinear structural behavior of composite connection between partially encased composite beam and concrete infilled steel tube column; in this model, the composite beam represents the slim floor. The ABAQUS finite element code was used to investigate the behavior of composite connection that consists of a shear steel plate and negative reinforcement of the composite slab. In this paper, the authors discusses the procedures to the numerical model construction including finite elements and boundary conditions. Besides, the influence of stress-strain relationships for concrete and steel and the parameters that defines each model are presented and discussed, as well as the different steel to concrete interface conditions. Based on the results obtained, the effectiveness of the numerical model developed was verified against experimental results showing a good agreement response for the Moment vs. Rotation response, as well as the moment resistance of the composite connection.

Experimental and analytical research on the flexural behaviour of steel–ECC composite beams under negative bending moments

Due to the strain-hardening and multi-cracking properties, engineered cementitious composite (ECC) is a new solution to the cracking issue in the negative bending moment region of steel–concrete composite beams. This paper presents an experimental and analytical study on the flexural performance of composite steel–ECC beams subjected to negative bending moments as well as the tension stiffening behaviour of reinforced ECC (R/ECC) flange slabs. Three beams with different slab materials and reinforcement ratios were tested under a hogging moment. Experimental results demonstrated significant enhancement in stiffness and crack resistance for the steel–ECC composite beams. A practical four-parameter fibre-bridging model was established to describe the strain-hardening behaviour of different ECC materials. Then, a modified analytical tension-stiffening model for R/ECC was formulated considering the strain-hardening behaviour of ECC and rebar–ECC bond–slip interaction based on the conventional tension-stiffening model for reinforced concrete. This modified model was verified by several direct tensile tests of R/ECC members. In addition, by applying the model to the traditional fibre beam–column element model, the mechanical performance and crack opening of general R/ECC structures were derived. The simulation results of the steel–ECC composite beams demonstrated satisfactory accuracy compared with the test results. Finally, a parametric study based on the new model was conducted to identify the influence of several important material and structural parameters on the flexural performance of steel–ECC composite beams under negative moments.

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.