Composite Slabs Research Articles

Materials, Structure, and construction of a low-shrinkage UHPC overlay on concrete bridge deck

As ultra-high performance concrete (UHPC) has superior mechanical and durability properties, it is a promising solution to apply a thin layer of UHPC on top of normal concrete bridge decks to extend the service life and enhance the structure integrity. However, the large autogenous shrinkage characteristics of UHPC is still an issue, and there is a lack of research focus on the structural design and stress analysis of the concrete bridge deck and UHPC overlay system. Thus, this study first designs and evaluates a new low-shrinkage UHPC mixture internally cured with a high-strength, high-abrasion resistant, and porous aggregate (calcined bauxite, CB), and the optical mixture design is validated by testing the fresh, mechanical, autogenous shrinkage, abrasion, and impact properties of the UHPCs. Second, the outdoor UHPC overlay-NC composite slab experiments and the numerical modeling are carried out to analyze the shrinkage performance of the UHPC, debonding potential of the overlay layer, stress and strains development in the system. Then, the significant influencing factors and the key measures to assure the UHPC-NC interface bonding properties are obtained, including proposing a grouped L-shape steel rebar arrangement for strengthening the interface. Finally, the applicability of the new low-shrinkage UHPC mixture as overlay materials on a real concrete bridge deck is demonstrated. Based on these, the engineering design scheme and the construction recommendations of an environmentally-cured low-shrinkage UHPC overlay on concrete bridge deck is given. The utilization of UHPC overlay on concrete bridge decks offers a novel paving system that substantially enhances strength, abrasion resistance, and durability.

Damage modes and mechanism of steel-concrete composite bridge slabs under contact explosion

The steel-concrete (SC) composite bridge slab is widely used in long-span bridges. With the increasing threat of explosive attacks on bridges, understanding the blast-resistant performance of composite bridge slabs is important. In this paper, SC composite slabs with different types of interfaces between concrete slab and steel plate, and different steel plate thickness, were tested under contact explosion. The damage modes and dynamic responses were carefully observed and measured. Refined FE models were developed to investigate the damage mechanism by analyzing and comparing the detailed damage process of slabs and characteristics of stress wave propagation. The results revealed that the damage modes of SC composite slabs varied significantly depending on the type of interface. For slabs with stud connectors, the compressive stress wave propagated within the composite slab in a spherical pattern and finally induced a circular concrete crater and steel plate deformation. Increasing the thickness of steel plate significantly reduced steel plate deformation. For slab with PBL connectors, the stress wave in the concrete was attenuated when it propagated across the PBL ribs, while the stress of concrete between the ribs nearest to the explosion was much large than that outside the ribs. Stress reflection on the top of PBL ribs increased the damage degree of concrete, potentially leading to induced cracks along the ribs. The overall response of composite slabs could be divided into the combined phase and separated phase. The PBL ribs could better restrain the interface detachment compared to studs.

Resilient performance of steel connections with low yield point fuses considering the effect of RC floor slab

The beam-column connection of a steel frame equipped with replaceable low yield point steel cover plates (SF-LYCP) was proposed to address the significant repair challenge and financial losses caused by beam-column connection brittle failure after an earthquake. According to an experimental study, the SF-LYCP exhibited outstanding bearing capacity, ductility, energy dissipation, and post-earthquake rapid recovery performance. To explore the effect of the reinforced concrete (RC) floor slab on the mechanical behavior of SF-LYCP in a natural working environment, the finite element method of steel beam-column connection with low yield point (LYP) steel cover plates considering the effect of the RC floor slab (SF-LYCP-RCslab) was developed and analyzed by ABAQUS. The results demonstrated that the proposed finite method was able to accurately predict the behavior of SF-LYCP-RCslab. The load capacity, initial stiffness, and energy dissipation capacity of the SF-LYCP-RCslab were increased in comparison to the SF-LYCP. The LYP cover plates in the SF-LYCP-RCslab still played the desirable role of structural fuses. However, the concrete of the RC floor slab had severe damage and prevented the quick replacement of repairable LYP cover plates. Based on these findings, four improved strategies for the SF-LYCP-RCslab were proposed to reduce concrete damage and increase the replacement convenience of damaged elements. Comprehensively considering the bearing capacity, ductility, energy dissipation, structural fuse function, concrete damage, and post-earthquake rapid recovery performance, the improved strategy, which adopted a profiled steel–concrete composite floor slab with a gap, was recommended in steel frame beam-column connection design.

Efficient numerical simulation of steel-UHPC composite structures based on a fiber beam-column model

To satisfy the demands of different engineering scenarios, ultra-high performance concrete (UHPC) is usually combined with steel to form various steel-UHPC composite structures. This study proposes an efficient numerical method for simulating steel-UHPC composite structures. A finite element analysis program, SU-COMPONA, is developed, which combines the fiber beam-column model and the concept of smeared cracks. Rational material constitutive laws are proposed and integrated into the program to describe the uniaxial behavior of UHPC and steel fibers. The proposed numerical method is validated against sufficient experimental data for various steel-UHPC composite structures, including reinforced UHPC beams and slabs, steel-UHPC composite beams and slabs and steel-UHPC-steel sandwich beams. In addition, the simulation performance is evaluated quantitatively. The results show that the proposed method can predict the ultimate capacity, the load-deflection curve and the development of crack widths with satisfactory accuracy and stability. Compared with the elaborate three-dimensional finite element method, the proposed method based on the fiber beam-column model is a competitive numerical approach that can achieve higher efficiency with slightly less accuracy.

The assessment of structural behaviours of steel framing system – affordable house system design

Purpose Nowadays, residential buildings have become increasingly important due to the growing communities. The purpose of this study is to investigate the behavior of a steel structural framing system that incorporates lightweight load-bearing walls and slabs, and to compare the weight of materials used in cold-formed and hot-finished steel structural systems for affordable housing. Design/methodology/approach Four types of models consisting of 243 members were simulated. Model 1 is a cold-formed steel structural framing system, while Model 2 is a hot-finished steel structural framing system. Both Models 1 and 2 use lightweight wall panels and lightweight composite slabs. Models 3 and 4 are made with brick walls and precast reinforced concrete systems, respectively. These structures use different wall and slab materials, namely, brick walls and precast reinforced concrete. The analysis includes bending behavior, buckling resistance, shear resistance and torsional rotation analysis. Findings This study found that using thinner steel sections can increase the deflection value. Meanwhile, increasing member length and the ratio of slenderness will decrease buckling resistance. As the applied load increases, buckling deformation also increases. Furthermore, decreasing shear area causes a reduction in shear resistance. Thicker sections and the use of lightweight materials can decrease the torsional rotation value. Originality/value The weight comparison of the steel structures shows that Model 1, which is a cold-formed steel structure with lightweight wall panels and lightweight composite slabs, is the most suitable model due to its lightweight and affordability for housing. This model can also be used as a reference for the optimal design of modular structural framing using cold-formed steel materials in the field of civil engineering and as a promotional tool.

Composite slab floors made of cross laminated timber and ultra high-performance concrete: Early-age deflection, stripping time, and its implication on the structural performances

Timber-Concrete Composite floors made of Cross-Laminated Timber (CLT) and Ultra-High-Performance Concrete (UHPC) boast remarkable efficiency in lightweight and slenderness. While the rapid UHPC hardening facilitates swift construction, the optimal shoring time depends on the effect of the UHPC autogenous shrinkage on the floor deflection. This study aims to investigate the experimental deflection of CLT-UHPC floors at an early age without shoring and to develop a simplified model for predicting the optimal shoring time for TCC floors.An eco-friendly UHPC with recycled glass waste is considered in this study. Firstly, the evolution of its modulus of elasticity and compressive strength as well as the early-age shrinkage were experimentally characterized. Furthermore, the shear behavior of the notch connection was evaluated after 28 days, and it was estimated to be proportional to the stiffness of the concrete at an early age. Then, two TCC floors made of CLT-UHPC with a span of 3.6 m were cast and their deflection under the self-weight of fresh concrete was measured over the initial 28-day period in a simple supported configuration without the use of shoring. A simplified analytical model was developed to predict the TCC deflection at an early age by coupling an existing solution with the concept of Age-Adjusted Effective Modulus (AAEM). The model effectively predicted the experimental early-age deflection of the CLT-UHPC floor without the use of shoring. Finally, after 3 months, the TCC floors were tested under bending, showing a reduced structural stiffness of about 35 %, caused by concrete cracking due to restrained shrinkage. The parametric analysis with the developed analytical tool allowed for estimating the maximum span of CLT-UHPC floors without shoring or, for longer spans, the optimal time of shoring removal. This study offers valuable insights into the behavior of CLT-UHPC along, along with a robust analytical tool to optimize their design and construction of TCC floors.

Study on the fire performance of novel G550 galvanized steel‐concrete composite slabs

AbstractTo reduce the construction and maintenance difficulties caused by fire proof coatings and reinforcement used in composite structures, 2 new types of steel‐concrete composite slab was proposed combining G550 galvanized steel with re‐entrant sheeting and closed profiled sheeting. 12 full‐scale standard fire tests were conducted to investigate the fire performance of G550 galvanized steel‐concrete composite slabs. Temperature rise within profiled sheeting and concrete are compared for the novel composite slabs. With the development of bearing capacity index, the fire performance of novel G550 galvanized steel‐ concrete composite slabs are analyzed under the same unified standard. Results showed that all the newly developed composite slabs could reach the design requirements for buildings up to 18 m above ground without the use of coatings and reinforcement. And the composite slabs with closed profiled sheeting can reach 120 min fire resistance when bearing capacity index is less than approximately 0.1 and are suitable for application in high‐rise buildings.

Finite Element Analysis on Flexural Bearing Performance of Innovative Closed Profiled Steel Sheeting‐Concrete Composite Slab

AbstractBased on ABAQUS system, the flexural behavior of the closed profiled steel sheeting‐concrete composite slab was studied. The influence of different geometric and material parameters on the bending bearing capacity and flexural rigidity of the closed profiled steel sheeting‐concrete composite slab was analyzed. And the applicability of the current Chinese codes to the calculation of the bending bearing capacity of the closed composite slab was discussed. The results showed that, the influence of slab thickness is the largest, followed by the thickness and strength of steel sheeting, and the influence of concrete strength is the smallest; the calculation of the flexural bearing capacity of the closed profiled steel sheeting‐concrete composite slab is safe and conservative in accordance with the current Chinese codes.

Shear Capacity of Channel Shear Connectors Applied in Composite Slabs with Profiled Steel Decking

AbstractThis paper assesses the shear capacity and the structural behaviour of channel connectors in composite slabs. Push‐out specimens were analyzed numerically by using the finite element program ABAQUS. For the studied solution, regular openings at the lower flange in the profiled decking are considered to allow the welded channel connector to pass through. The numerical model was calibrated against experimental outputs on push‐out tests found in the literature. Then, the influence of steel decking thickness on load capacity, stiffness and ductility of channel connectors in composite slabs was also assessed. In addition, it was concluded that safe predictions of load capacity could be obtained by including reduction factors in the Canadian design approach.

Orthotropic composite slabs for road bridges

AbstractLarge increases in traffic loads led to extensive fatigue damages to existing orthotropic steel deck slabs of road bridges. Reinforced concrete bridges and conventional composite bridges are less susceptible to fatigue but considerably heavier. The ortho‐composite slab is a lightweight and robust alternative construction method, which retains the advantages of the previously mentioned construction methods, but eliminates their disadvantages. Within the framework of the AiF‐FOSTA research project P1265 [1], the construction of the bridge deck was developed using dowel strips as composite elements with high load‐bearing capacity and fatigue resistance. The principle of area composite with loading of the dowel strips in longitudinal and transverse direction was used. Extensive experimental and structural mechanics studies were conducted, particularly investigating the load‐bearing capacity and fatigue strength of the ortho‐composite slab under local load application. The following article describes the load‐bearing structure of the ortho‐composite slab and the motivation for the research project P1265. It gives an overview of the experimental investigations carried out. Finally, the article presents pilot projects that were carried out to apply the construction method. In further articles on Eurosteel, the experimental investigations and structural‐mechanical calculations are described in more detail (see [2] and [3]).

Numerical investigation on bending behaviour of hollow precast slab with FRP tubes using Ansys

Hollow-core precast concrete slabs are frequently employed in modular building construction to reduce concrete volume and weight. Nevertheless, the presence of the hollow-core increases susceptibility to failure. To address this issue, a composite reinforcing system (CRS) has been developed to support the void in precast slabs. This research aims to investigate the bending behavior of a composite slab comprising precast concrete, steel, and the composite reinforcement system. Bending tests will be conducted on precast slabs with various CRS configurations (including changes in tube material properties and tube cross-section) to assess the structural performance of this innovative construction system. Additionally, a non-linear finite element modeling was employed to gain a comprehensive understanding of the behavior of the internal components of the slab. The findings of this study will offer valuable insights for designing more reliable and cost-effective hollow-core precast concrete slabs.

Numerical investigations of the load‐bearing and fatigue behavior of orthotropic composite slabs for road bridges

AbstractFatigue damage to existing steel bridges occurred due to the large increases in traffic loads and the notch sharpness in the details of orthotropic steel roadway slabs. The development of the orthotropic‐composite‐slab (OC‐slab) provides an alternative durable and lightweight composite construction. As part of the AIF‐FOSTA research project P1265 [1], the orthotropic‐composite‐slab for road bridges is currently being investigated at the Technische Universität Dresden. The project aims to develop fundamentals for the design of OC‐slabs with dowel strips. The investigations create important foundations for the establishment of the innovative construction method as an economical and durable alternative. The papers [2] and [3] give an overview of the construction and the load bearing behavior of the OC‐Slab, the paper [4] details about the experimental test program. This paper describes the numerical investigations carried out. They complement the experimental tests and provide additional knowledge about the load‐bearing and fatigue behavior of the OC‐slabs with dowel strips. The focus is on the presentation of the numerical simulation of the beam test and the determination of the ultimate and fatigue strength of the structure.

Behaviour of demountable steel‐concrete composite beams with bolts and headed studs

AbstractImplementation of demountable beams in steel‐concrete composite floors enables structure reuse during several life cycles, consequently leading to savings in material consumption and reduction of emissions, providing overall ecological benefits. The behaviour of the innovative demountable beam with a shear connection consisting of headed studs and bolts is analysed in this paper. The proposed beam is formed of a steel profile and a steel‐concrete composite slab cast in open trough profiled steel sheeting. Headed studs, welded to the additional steel angles, are placed in sheeting ribs, whereas bolts are installed between ribs, connecting the steel angles and profile flange. A numerical FE model of a full‐scale steel‐concrete composite beam has been developed to analyse the beam behaviour under service loads. Experimental results of push‐out tests have been used to describe the load‐slip behaviour of headed studs, whereas bolt response has been simulated according to the experimental investigations of lap joints with preloaded bolts and oversize holes. The parametric study has been conducted by varying the bolt diameter, grade and bolt hole size. The results have validated the applicability of the proposed system, confirming the fulfilment of serviceability limit state requirements.

A review on long‐term behaviour of steel‐concrete composite structures

AbstractThe exceptional structural performance of steel‐concrete composite structures, which harness the advantages of both steel and concrete, has garnered considerable attention. Following a summary of the fundamental time‐dependent characteristics of concrete, this paper reviews the existing studies about the long‐term behaviour of various steel‐concrete composite components, including slabs, beams, columns and walls. For composite slabs, nonuniform shrinkage occurs along the thickness direction. The long‐term behaviour of composite beams is significantly affected by the degree of shear connection. While the creep and shrinkage effects of composite columns are substantially reduced in comparison to reinforced concrete columns, stress redistribution may cause yielding or buckling of the steel tube. However, there is currently limited research available on the long‐term behaviour of composite walls with profiled steel plates, and no studies have been conducted on composite walls made of double‐skinned flat steel faceplates infilled with concrete. This lack of knowledge may lead to design uncertainties for composite coupled wall‐frame structures. To bridge this gap, the authors are currently conducting a corresponding long‐term experimental program.

Investigations of the shear connectors and the load‐bearing behaviour of steel cross‐laminated timber composite beams

AbstractA strengthening of cross laminated timber (CLT) by a composite effect with steel girders can act as a sustainable option to replace concrete or composite slabs for spans of more than 7 m. The efficiency of a composite structure is strongly influenced by the stiffness of the shear connectors. Therefore, fully threaded screws and shear studs were investigated in double push‐out tests. The screws are inclined to increase their stiffness and are rotated within the drilled hole towards the web, so that a multidimensional load situation with both axial and shear loads results. The shear studs are placed in openings of the CLT and cast in with mortar. The shear tests confirmed that their load bearing behaviour can basically be described with existing analytical calculation approaches. The findings were extended in large‐scale 4‐point bending tests to investigate the bending behaviour of the composite beam.

Three-dimensional finite element modeling for bending and pull-out tests of composite slabs

This article introduces a novel modeling and simulation methodology that advances the understanding of steel deck and concrete slab micromechanics for bending and pull-out composite slab tests. Three-dimensional composite models detailed the embossment depth, slope, steel thickness, and tilting angle to overcome previous model simplification assumptions. Newton-Raphson was the simulation method that enabled the consideration of material non-linearities. The validity of each model was contrasted against the results from actual laboratory tests. The model incorporating the non-linearity of materials and a crack inducer was very consistent with the tests. The other two models, which did not account for non-linear behaviors, were partially consistent with test results at complementary bending stages and thus could be combined to reproduce the tests. The robustness of the simulation approach was leveraged to analyze the influence of parametric and boundary conditions in pull-out simulations. Also, micromechanics phenomena that cannot be observed during laboratory tests were investigated. The proposed computing method offers the opportunity to model, predict, and hence optimize the composite slab and steel deck profile design without the need to perform expensive and time-consuming tests on actual specimens.

Experimental study on flexural behavior of precast ultra-lightweight ECC plank with lattice girder at construction stage

During the construction of precast concrete (PC) structures, concrete composite slabs are commonly used, employing PC planks with lattice girders as permanent formwork to enhance assembly efficiency while ensuring structural performance. However, traditional PC planks suffer from heavy weight and susceptibility to cracking, adversely affecting construction efficiency and quality. This paper proposes the incorporation of ultra-lightweight engineered cementitious composite (ULECC) into PC planks. The research aims to investigate the flexural behavior of precast ULECC planks with lattice girders during the construction stage. Four-point bending tests were conducted to study the effects of lattice girders and ULECC layer. The introduction of ULECC reduced the self-weight of precast planks by 24%, while resulting in a decrease in strength and stiffness due to ULECC's lower elastic modulus. Remarkably, precast ULECC planks exhibited excellent crack width control. Even at a deflection-span ratio of approximately 4%, precast ULECC planks were capable of maintaining crack widths below 0.2 mm. The combination of ULECC and lattice girders significantly improved the structural performance of precast ULECC planks, allowing them to meet construction requirements without requiring temporary support.

Experimental study and numerical modelling of a novel two-way steel-concrete composite slab

This study proposes a new innovative two-way steel-concrete composite slab system. The experimental work investigates the structural capacity, shear behaviour and two-way load distribution of the proposed composite slabs consisting of a new profiled steel deck and concrete. The innovative deck is developed by providing 90° bends in corrugated steel sheets to form hat sections, which then are placed on a corrugated base sheet in the perpendicular direction. Five composite slabs were tested under uniform loading, in which three slabs contained shear studs, and the remaining two were tested without shear studs. The slabs failed by flexural failure and shear bond failure, and the composite slabs with and without studs showed comparable load-carrying capacity and two-way action. The unique geometry of the deck profile provides good longitudinal shear capacity in the main direction. The slip is absent in the main longitudinal direction of the slab due to the corrugated top-hats. The provided shear studs further complement the role of the top-hats by resisting interface shear failure in the perpendicular direction. Therefore, the new deck type can be used effectively in two-way composite slabs for shear and load capacity by reducing the quantity of additional shear connectors, which is a significant advantage of the proposed deck compared to conventional deck types. A finite element (FE) model of the composite slabs with and without shear connectors is developed and validated against the experimental results and then used to investigate the slab's performance in two-way load distribution.

Entwicklung einer Orthoverbundfahrbahnplatte für Straßenbrücken

AbstractStark angestiegene Verkehrsbelastungen führten zu umfangreichen Ermüdungsschäden an existierenden orthotropen Stahlfahrbahnplatten. Stahlbetonbrücken und herkömmliche Verbundbrücken sind zwar weniger ermüdungsanfällig, aber erheblich schwerer. Die sog. Orthoverbundfahrbahnplatte ist eine vergleichsweise leichte und robuste alternative Bauweise, die die Vorteile der zuvor genannten Bauweisen beibehält, deren Nachteile jedoch beseitigt. Im Rahmen des AiF‐FOSTA‐Forschungsprojekts P 1265 wird die Konstruktion des Brückendecks unter Verwendung von Dübelleisten als Verbundmittel mit hoher Tragfähigkeit und Ermüdungsfestigkeit entwickelt. Dabei wird das Prinzip des Flächenverbunds mit Beanspruchung der Leisten in Längs‐ und Querrichtung genutzt. Es wurden umfangreiche experimentelle und strukturmechanische Untersuchungen durchgeführt, im Rahmen derer insbesondere die Tragwirkung und Ermüdungsfestigkeit der Orthoverbundfahrbahnplatte unter lokaler Lasteinleitung sowie der Dübelleisten bei Beanspruchung in Querrichtung analysiert wurden. Der folgende Beitrag geht auf die Motivation zum Forschungsvorhaben ein und gibt eine Übersicht über die durchgeführten Untersuchungen. Darüber hinaus wird ein Pilotprojekt vorgestellt, das zur Anwendung der Bauweise ausgeführt wurde.

Seismic and collapse behavior of existing high-rise steel buildings under long-period earthquakes

This work presented the experimental and numerical evaluation of the seismic and collapse behavior of Japanese existing high-rise steel buildings subjected to long-period ground motions (LPGMs). Initially, the experiment (E-Defense, 2008) was performed by the full-scale shaking table tests on a typical 21-story steel frame substructure. Accordingly, a nonlinear rotational spring model was used in the numerical modeling. In consideration of the stiffness/strength deterioration and fatigue fracture of beam-column connections, the cyclic pushover analysis was utilized to account for such effect using seismic response data from system-level testing. Subsequently, the numerical model parameters were derived and validated with the initial experiment on the high-rise steel frame substructure. Herein, a well agreement on the seismic failure behavior between simulation and experiment was found in this situation. Furthermore, both field-welded and shop-welded connections on the seismic performance were included for comparison. For the 21-story prototype steel building (built before 1970s), a series of numerical collapse analyses were performed. The above revised model using nonlinear static pushover analysis and time history analysis were conducted to simulate and compare the effects of connection details and composite slabs on the 21-story prototype building. Finally, a cyclic loading protocol for simulating LPGMs was proposed, and the related ultimate failure behavior of the high-rise building was analytically discussed. Critically, this work should provide a viable strategy to numerically simulate the seismic and collapse behavior of high-rise steel buildings in this progressing construction field.