Composite Slabs Research Articles

Experimental investigation of flare groove weld stiffness in lattice girder beams by means of push-out tests

With the purpose to investigate the behaviour of the lattice girder composite slab (LGCS) at construction stage, a push-out experimental investigation has been carried out on 9 lattice girder specimens having not only different diameters of web bars, top and bottom chords, but also different heights. The results obtained from tests are here presented and analysed. The paper focuses on the behaviour of the flare groove welds among web bar and bottom and top chords. For each tested specimen a F.E.M. model has been developed, schematizing the stiffness of the flare groove welds by local springs, whose stiffness has been calibrated by means of the load-displacement curves obtained from tests. A chart that allows to estimate the aforesaid stiffness of a lattice girder beam in function of the triad of top, bottom chords and web bar diameters, and in function of the inclination between the web bar and the beam horizontal transversal axis is proposed. This paper highlights that the chart proposed here provides stiffness values with which numerical models can more accurately predict the behaviour of LGCS during construction. Furthermore, this paper highlights that the weld stiffness of the flare groove influences the buckling length of the web bar.

Structural and Service Performance of Composite Slabs with High Recycled Aggregate Concrete Contents

Structural and Service Performance of Composite Slabs with High Recycled Aggregate Concrete Contents

Numerical modeling of inverted-U-shaped connectors to enhance the performance of composite beams

Steel and concrete are the most essential and frequently encountered building materials. These materials are used in combined structural systems, such as concrete cores surrounded by steel pipes, as well as composite structures with steel and concrete components. In numerous countries, the combination of concrete cores, steel frames, and composite slab construction has become the typical construction approach for multistory commercial buildings. The shear stud connector is one of the elements used in the construction of composite sections. The use of inverted-U-shaped reinforcement experimentally and numerically significantly improves punching shear resistance for post-tensioned slabs compared with slabs that use stud connectors. Other experimental and numerical studies using inverted-U-shaped reinforcement in post-tensioned beams indicate an enhancement in their shear strength. Recently, an experimental investigation was performed on composite beams to inspect the effect of mild and rigid shear stud connectors. The experimental and numerical results for the composite beams showed good correlation. The goal of this study was to numerically model the capacity and deformation of composite beams with inverted-U-shaped connectors of varying configuration and mechanical properties and compare the beam performance with composite beams using shear stud connectors.

Large-scale test of a 3D steel moment-resisting frame with composite slab subject to penultimate interior column loss

This paper investigates the structural behavior of a typical three-dimensional steel frame-concrete slab substructure (3D composite floor subassembly) subject to a penultimate interior column removal scenario. A two-by-two bay composite floor subassembly is one-third downscaled and quasi-statically pushed down to failure by a specially designed twelve-point loading tree in displacement control mode. Unlike the previous studies where progressive collapse propagates vertically, the current study reveals the possibility of horizontal progressive collapse of 3D composite floor structures that characterized by losing stability of the exterior column. The load-displacement relationships, failure modes, deformation pattern and beam end rotations of the test specimen are presented in detail. Based on the test results, the three load-transferring mechanisms, including flexural action, catenary action and tensile membrane action, are determined and discussed. Besides, the test results are compared with previous test results subject to interior column, edge column and corner column removal scenarios, based on which a structural design and analysis strategy of normal composite buildings against progressive collapse are recommended in this study.

Structural damage assessment of RC slab strengthened with POZD coated steel plate under contact explosion

To reveal the anti-explosion capacity of polyisocyanate oxazodone (POZD)-coated steel RC composite structural slabs, a explosion test was carried out for 2 test models. Using ANSYS/LS-DYNA, the damage mode and maximum mid-span deflection of steel plate-RC plate and POZD coated steel plate-RC plate were explored, and the experimental results were compared. Parametric analysis of the charge, POZD, steel plate and concrete slab thickness on the anti-explosion performance of the POZD-steel plate-RC slab. The results show that increasing the thickness of POZD, steel plate and RC slab can effectively reduce the POZD-steel – RC slab mid-span deflection. The POZD coating and steel plates increased the tensile area of concrete and improved the flexural and load carrying ability of the concrete slabs.

Research on the Development and Joint Improvement of Ceramsite Lightweight High-Titanium Heavy Slag Concrete Precast Composite Slab

Despite the continuous improvement in the research and development of concrete precast composite slab technology, problems like easy cracks and excessive weight at the joints remain. In this study, high-titanium heavy slag was mixed with different kinds of ceramsite to prepare ceramsite lightweight high-titanium heavy slag concrete. The joint of the composite slab was optimized to develop a novel ceramsite lightweight high-titanium heavy slag concrete precast composite slab, hereinafter referred to as “CLHCPCS”. Two CLHCPCS and one ordinary concrete composite slab were prepared. This study analyzed the effects of new materials and improved joints on the flexural capacity and crack resistance of CLHCPCS. It concluded that the density of high-titanium heavy slag concrete with shale ceramsite decreased by 12.0%, and the density of high-titanium heavy slag concrete with fly ash ceramsite decreased by 10.6%. At a 30% dosage of fly ash ceramsite, the compressive strength and splitting tensile strength of concrete reached the maximum. At a 20% dosage of shale ceramsite, the mechanical properties were optimal. Finally, fly ash ceramsite was selected as part coarse aggregate of CLHCPCS. CLHCPCS 1 and 2 demonstrated superior ultimate bearing capacity and crack resistance than ordinary concrete composite slab DBS1, with its ultimate bending capacity test value higher than the average value of ordinary concrete composite slab. ANSYS established the joint model of CLHCPCS for a bending simulation test. The stress and strain distribution of the model and the ultimate bending capacity under the plastic line method were obtained, consistent with theory and experimental analysis results.

Numerical Studies on Composite Deck Slab With Floor Openings

Openings in slabs are provided mainly for service works. According to the purpose of the services, the size of the openings was classified as small, medium, and large. The provision of openings in a composite slab was not addressed in design codes like EC-4 and IS 11384. Normally the Longitudinal shear interaction is the influencing factor in determining the capacity and elastic rigidity of a composite slab which may be affected by the presence of openings. In the market, there are various forms of embossment/indentation available to enhance the interlocking at the interface of the Cold Form Steel decking sheet and the topping concrete thereby an increased longitudinal shear resistance can be achieved at the interface. In this numerical study, Among the various type of embossments, combined types of embossments (rectangular and chevron) are considered then the m and k values are determined with the help of the Penalty Friction interaction approach and the same was verified with the known experimental values for a solid slab. In addition, Finite Element [FE] models with various sizes of floor openings were created under the guidelines of SCI publication P300 and SDI Technical Guidance on Deck Damage and Penetrations. The effects of those openings located in the high shear region and no shear region are studied. The simulated load-deflection responses of various FE floor opening models were compared.

Fatigue behaviour of joint-free bridges with steel and GFRP-reinforced ECC link slabs

Engineered Cementitious Composite (ECC) link slabs provide a feasible alternative to leaking expansion joints for improving long-term durability of slab-on-girder bridges. The use of Glass Fiber Reinforced Polymer (GFRP) rebars have become increasingly common for inducing superior chemical resistance in bridge decks in salt-prone locations. Existing literature lacks experimental research on effects of fatigue load on joint-free bridges with ECC link slabs reinforced with GFRP bars. This paper presents results of experimental testing of joint-free bridges with GFRP or steel-reinforced ECC link slabs subjected to static and fatigue (up to 1 million cycles at 4 Hz) loadings. Comparative performance between GFRP and steel-reinforced ECC link slab bridges is described based on load–deflection or moment-rotation behaviour, strain characteristics and crack development in pre-fatigue, fatigue and post-fatigue stages. After 1 million fatigue cycles, the GFRP-reinforced ECC link slab exhibited smaller crack widths and higher deformation capacity while its incorporation provided superior ductility and deformation capability of the full bridge. A finite element (FE) model was also developed using experimental results to simulate load–deflection behaviour of composite deck-steel girder joint-free bridge with ECC link slab subjected to fatigue loading. Parametric FE study showed that increasing mean stress level caused increased composite deck-steel girder deflection while link slab deflection was limited by bridge span deformation.

Tensile test of headed stud in steel-UHPC composite slab

The headed studs as connectors play a key role in affecting the mechanical properties of steel-UHPC composite slab. In this paper, eighteen tensile specimens were tested to analyze the failure mode, loading process, bearing capacity and stiffness. Where the studs (diameter of 13 mm) commonly used in steel-UHPC composite structure were taken as the subject, and the steel fiber content (0 %, 1 %, and 2 %) and specimen size (160 mm and 200 mm) were the parameters. The influence of each parameter on the tensile load-interface separation curve, failure mode, tensile bearing capacity and tensile stiffness was then analyzed. There are two typical failure modes, that is, UHPC cone failure and stud fracture. Test results show that specification ACI 349–13 indicated a relatively high calculation accuracy to predict the tensile bearing capacity of specimens with UHPC cone failure, and the tensile stiffness value can be calculated based on the secant modulus with 0.1 mm slip.

Experimental research on mechanical performance of the lightweight composite slabs Research Progress on the Lightweight High-Entropy Alloys

The high-entropy alloy, a new multi-principal element alloy, contains light elements to obtain the lightweight high-entropy alloy (HEA) with the outstanding property of low densities. Its high strength and hardness, corrosion resistance, and high-temperature resistance allow it to be broadly applied in aerospace, transportation, etc, which has attracted wide attention and research. Its research status is described and its component design methods are classified in this paper. Meanwhile, this paper summarizes its microscopic phase structure and properties of different kinds, including hardness, strength, corrosion resistance, and high-temperature resistance. Finally, its application prospect and the shortcomings of current research are also summed up.

Experimental Analysis of Cooling Effects on Mechanical Properties of Steel for Reinforced Concrete After High-Temperature Exposure

This article examines the mechanical properties of hot rolled FeE500-3 steels, used for reinforced concrete, with a nominal yield strength of 500 MPa. These steels are intended for the manufacture of beams, columns, and composite slabs made of reinforced concrete. This analysis is centered on small diameter ribbed bars (6 mm, 8 mm, and 10 mm) massively used for residential construction projects. It includes tensile tests carried out on specimens cooled to ambient temperature after a heating cycle at several temperature levels from 300 °C to 900 °C. Two cooling methods are studied to assess their influence on the residual mechanical properties of the steel material (elastic strength, ultimate strength, Young's modulus, strain at yield point, strain at the ultimate point, and strain at failure). The results have showed that the reinforcements cooled by air lose approximately 30% of their resistance from 700 °C and 20% in the case of cooling by water. The type of cooling has a negligible effect on the Young module. Ductility is the most impacted mechanical property. Significant degradation of ultimate strain and strain at failure has been noted for bars heated beyond 600 °C and cooled by water. However, ductility has improved for natural air cooling. Curves and predicted equations of the main residual mechanical properties of hot-rolled FeE500-3 steel are presented in this study. They can be used to rehabilitate damaged buildings and improve their safety.

Post-cracking punching shear behavior of concrete flat slabs partially reinforced with full-depth UHPC: Experiment and mechanical model

Concrete flat slab partially reinforced with full depth UHPC within the critical punching shear area was considered an advanced and economical form of slabs since the application of UHPC can significantly enhance the punching shear behavior after cracking due to its superior mechanical properties. An experimental study of six flat slabs was conducted to research the post-cracking punching shear behavior of NC-UHPC composite slabs, where the crack pattern, stiffness degradation, post-cracking deformability, and peak strengths under different UHPC dimensions were investigated. The test results revealed that the failure mode of slabs changed from brittle punching failure to ductile combined punching shear-flexural failure when the width of the UHPC coverage area reaches more than 1 times the slab thickness from the periphery of the loading plate face. Two new ductility indexes were proposed to evaluate the post-cracking deformability of NC-UHPC composite slabs, which was improved by about 65 % and 108 %, compared to that of NC slabs, respectively. The influence of different UHPC dimensions on the post-cracking punching shear behavior was analyzed. The optimal application of UHPC in NC-UHPC composite slabs was deemed to be the area enclosed by a perimeter located at about 1–2 times of slab thickness from the periphery of the loading plate face. Meanwhile, the peak strengths of NC-UHPC composite slabs were predicted by two mechanical models. It was concluded that the mechanical model proposed in this paper which consider both fibers’ contribution and the influence of different UHPC dimensions can predict the peak strength of NC-UHPC composite slabs accurately.

A Creep and Shrinkage Prediction Model for Serviceability Analysis of Composite Concrete Slabs with Steel Decking

A Creep and Shrinkage Prediction Model for Serviceability Analysis of Composite Concrete Slabs with Steel Decking

The Development and Application of Prefabricated Buildings

This essay will start at the development of construction area, including the detailed introduction of the meaning and features of prefabricated buildings, as well as its general situation and requirements and policies relating to prefabricated buildings development in part of provinces in China. In the second half of this report, detailed introduction to advantages and disadvantages of main prefabricated components like precast reinforced concrete composite slab which are applied for domestic constructions and combination characteristics of commonly used concrete sandwich wall. This essay may offer some references to related workers and students studying in related majors.

Experimental and theoretical analysis on truss construction robot: Automatic grasping and hoisting of concrete composite floor slab

AbstractThe development of various construction robots can significantly reduce the construction labor intensity and risk. We present an experimental task of a truss construction robot, including automatic grasping and hoist positioning of concrete composite floor slab. And, a control strategy matching the construction robot is proposed to solve the following problems: (a) Due to the widespread manufacturing errors of building components, the position deviation of diagonal web reinforcement on concrete composite floor slab may cause grasping failure. (b) The chaotic surface of the floor slab seriously affects the recognition accuracy of the grasping target. (c) The large mass and inertia of heavy‐duty hanger and concrete composite floor slab make it difficult for robot to achieve accurate positioning under eccentric load condition. The machine vision recognition system ensures that if the diagonal web reinforcement is detected more than half of the grasping path, the grapple hook can change the grasping path independently to prevent it from colliding with the offset diagonal web reinforcement. An anticollision and grasping path planning method based on machine vision is proposed to improve the success rate and efficiency of automatic grasping. The mean value of proportional speed and proportional position is introduced as the evaluation speed and evaluation position of driving wheel to improve the accuracy of multiwheel synchronization. Moreover, we analyzed the robot performance from actual grasping and hoist positioning process of the concrete composite floor slab. The experimental results show that the robot has a good performance on the automatic grasping and hoisting of the concrete composite floor slab.

OpenSeesdevelopment for modelling timber structural members subjected to realistic fire impact

AbstractTimber buildings have been preferred in many regions for the sustainable nature of timber material. Although engineered timber products become promising alternates to traditional construction materials, the fire safety of timber buildings remains a key barrier to wider use. Currently, the design of timber structures mostly adopts the Eurocode 5 approach, which estimates the heat transfer or char depth under the premise of standard fire exposure. To investigate the behaviour of timber structural members in the context of realistic fire action in compartments, appropriate models for different stages of numerical simulation are needed. A series of development have now been conducted in the open‐source platform OpenSees, which enables modelling the heat transfer of timber sections in non‐standard fire scenarios and thermo‐mechanical analysis model using either beam elements or shell elements for various timber structural members. Corresponding thermal actions are developed to deal with timber slabs in fire or timber beams subjected to three‐side fire exposure. Tests on cross‐laminated timber beams at ambient temperature and under fire exposure are modelled to validate the developed capabilities, which is followed by modelling a glued laminated timber beam heated by furnace. In the end, a timber‐concrete composite slab is modelled using the fire impact from a Computational Fluid Dynamics model, which demonstrates the current vision of modelling timber structures in fire and OpenSees for fire is committed to providing such an open‐source research platform to support further modelling work.

Experimental performance of novel cost – effective hybrid composite slabs made with cementitious composite

The present research investigation introduced a new design system for making cementitious structural elements. This study emphasizes on novel hybrid composite slab elements. The combination of newly formed hybrid fiber reinforced engineered cementitious composite (HECC) and self-consolidation concrete (SCC) was used to make slabs. The main objective of this study was to introduce novel kind of cost effective and greener HECC structural elements. In this study total 13 types of slabs were casted based on the 7 different cement mixes. To analyse the behaviour of slab specimens cracking loads, load-deflection behaviour, energy absorption capacity, flexural strength capacity, general failure pattern, ecological and economical aspects was recorded. The results from current experimental approach depicted that new composite slab system enhanced the flexural performance, energy absorption, service life and ductility of slab specimens. Construction of slabs with HC approach reduced the global warming potential (GWP), embodied energy (EE) and cost by 16.98%, 36.1%, and 67.53% respectively than full depth PVA fiber reinforced slab (HECC1). PI method indicated that HC-SL6 slab members most preferable for flexural strength capacity, ultimate load, environmental and economical aspects.

Study on the Mechanical Performance of H-Shaped Steel-Concrete Laminated Plate Composite Beams under Negative Bending Moment

To make the construction of assembled steel-reinforced truss concrete laminated plate composite structure faster, safer, and more efficient, this paper proposes an H-shaped steel-reinforced truss concrete laminated plate composite structure with new angle connectors embedded in the precast bottom panel. Through experimental studies on the H-shaped steel-concrete laminated plate composite beams with precast bottom panels protruding from the bent-up bars, precast bottom panels with embedded new angle connectors and laminated whole cast slab, the similarities and differences of load-deflection, deflection distribution, interface slip, crack distribution and cross-section strain distribution of three groups of composite beams under negative bending moment were analyzed and compared. Using ABAQUS finite element software, we established a finite element model and found the numerical simulation results were in good agreement with the experimental results. Based on this, five groups of finite element models were established for parametric analysis to investigate the effect of concrete strength on the flexural load capacity and flexural stiffness of the steel-laminated plate composite beams with embedded angle connectors. The results of the study show that the combined performance of the H-shaped steel-concrete laminated plate composite beams with the new angle connection embedded in the precast bottom panel was better and the flexural stiffness was greater. The slippage of the H-shaped steel-concrete laminated plate composite beams with embedded new angle connectors in the precast bottom panel was less than the slippage of the precast bottom slab bent-up bars protruding and the laminated cast plate, with the maximum slippage being only 1/2 of the precast bottom panel bent-up bars protruding. In the composite structure of H-shaped steel-concrete composite slabs under negative bending moment, shear angle connectors can replace the bent-up bars protruding from the laminated bottom panel to achieve without extending the reinforcement of the laminated bottom panel.

Numerical modeling techniques and investigation into the flexural behavior of two‐way posttensioned concrete slabs with profiled steel sheeting

In recent years, the combined use of posttensioning methods with steel decking in the concrete slabs has provided significant benefits in both economic and structural terms. In construction practice, this prestressed composite floor has extensive use in two-way spanning slab systems. However, this application still has inherent limitations due to its novelty and lack of research in this specific field. Hence, this study aims to gain the first insight into the flexural behavior of a two-way posttensioned composite (PTC) slab system based on a numerical approach. Scientific software is utilized for the derived model validation with a focus on models' geometric and material nonlinearity. Available modeling techniques used to perform the posttensioning process and interaction of composite slabs are verified with existing experiments. A comparative study was conducted between PTC slabs and various conventional slab systems on two different support conditions. The findings in this study consider the structural effects of posttensioning and profiled steel sheeting on the flexural behavior of PTC slabs. In addition, numerical results from this research might help structural engineers to modify the design input parameters and make judgments on the bending stiffness of this two-way slab structure. Further studies are required since the shear behavior, flexural, and punching shear conditions in the column regions are not addressed in this article.

Investigation of corrugated profiles in thin lossy dielectric slabs for wideband absorption up to 100 GHz

The paper compares and optimizes through modeling conductive polymer composite slabs having different architectures of corrugated surfaces, designed to minimize both the reflectivity and its sensitivity to the angle of incidence of a microwave/millimeter wave signal impinging on the corrugated surface of the slab. Simulations using CST Studio software consider Poly-Lactid-Acid as dielectric material since it is widely used for 3D printing and offers very good possibilities of recycling in the frame of sustainability and green processing. Various profiles of corrugation are investigated; triangular, sinusoidal, or square-dot profiles, and compared with a uniform profile. Parameters such as height, width, and periodicity of the corrugations are varied in order to optimize the performances in terms of reflectivity over a large range of frequencies, between 20 GHz and 100 GHz. The configuration considered is the reflective screen, when the corrugated lossy dielectric slab covers a metallic plate mimicking the target. The goal is to maintain the reflectivity below 10 dB, in order to ensure up to 95% of absorption, for incidence angles up to 60°. Guidelines for the design and optimization of corrugated dielectric slab absorbers are proposed using specific gauges (Rozanov formalism and figure of merit) for the assessment of performances. Particular attention is devoted to the feasibility of manufacturing corrugated structures using additive 3D printing techniques.