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High-performance concretes without steam curing have great potential to improve crack resistance in the hogging-moment regions of continuous steel–concrete composite beams. This paper cond...

Ductility and robustness are two of the most important structural properties for the design of a building against extreme load cases, such as earthquakes and column loss scenarios. Various ...

Externally prestressed steel–concrete composite (EPSCC) beams in their deformed configuration are characterized by changes in the effective depth of external tendons. However, little infor...

The ladder-core system is a novel structural system for supertall towers that was created by SOM for Tower 1 at Shum Yip Upperhills, a mixed-use development in Shenzhen, China. The system features eight megacolumns at the perimeter that form the vertical rails of the ladders on the four corners of the core. Composite coupling beams—the ladder rungs—connect the megacolumns to the interior core, creating a comprehensive lateral system that allows for unobstructed occupant views, simplicity of the floor plates, and inherent structural stability.

The flexural behavior of steel-ultrahigh performance concrete (UHPC) composite beams with waffle slabs (SUCBWS) was investigated through experiments. The effects of design parameters, incl...

In general, a steel beam is assembled with a concrete slab using shear connectors. Recently, perfobond-shear connectors have been attracting interest because of their high shear stiffness a...

Continuous and semicontinuous castellated composite beams can present a global buckling mode in the hogging-moment regions known as lateral-distortional buckling. In this mode, the lower po...

This research aims to experimentally investigate the flexural behavior of ultra-high-performance concrete (UHPC)–steel composite beams with joints under a negative bending moment in order ...

This study presents a design method for the seismic retrofit and rehabilitation of steel moment-resisting frames (MRFs) with composite steel–concrete beams using the minimal-disturbance arm...

Laminated composite components have been widely used in engineering fields, such as aerospace engineering, automotive industries, marine structures, and civil infrastructure. Due to the inh...

This paper presents the results of full-scale flexural testing of deconstructable composite beams that are part of a sustainable composite floor system. In this system, steel beams are atta...

This study investigates the mutual effects of binding and pretreatment procedure (coating) on the structural performance of textile-reinforced concrete (TRC) composite beams under flexural ...

This paper presents a low-damage solution for self-centering steel and composite beam-to-column connections, with the issue of beam-growth being particularly addressed by permitting the con...

This paper presents the results of compartment fire experiments on four 12.8-m-long composite floor beams with various end support conditions. Specimens were constructed as partially compos...

In this paper, we conduct a systematic dynamic investigation of partial-interaction composite beams under various sophisticated loading conditions that have seldom been presented in the lit...

In this paper, a displacement-based weak-form quadrature element (WQE) is formulated and implemented for long-term response analysis of steel–concrete composite beams. The effects of creep ...

Ductile performance of beam structures often is achieved by material yielding or progressive failure of components. A new structural concept was developed and validated in this study to pro...

A novel approach is proposed to compute the secondary internal forces caused by creep in a continuous steel–concrete composite beam that is constructed through segmented pouring. The key to...

This work presents a collocation method for study of the static behavior of composite beams with consideration of linear and nonlinear partial interactions. The collocation concept is first...

In composite structures, the shear keys, that is, the headed studs or the perfobond rib shear connectors (PBL shear connectors), are typically subjected to external pressure, owing to the s...

This paper presents a study that examined the use of a new connection system in a prefabricated timber–concrete composite (TCC) beam in which a hardwood layer was glued to the top of a timb...

With the advantage of satisfying zero shear stress conditions on surfaces, the sinusoidal theory has been widely used for static and dynamic analysis of composite laminated structures. Neve...

In the design of steel structures, composite effects of stud shear connectors are generally measured using ordinary push-out tests. Furthermore, based on those results, the evaluation formu...

This paper focuses on the structural behavior and negative bending moment capacity of steel–timber composite (STC) beam-to-column connections with shear tabs. It is hypothesized that timber...

This paper investigates the flexural behavior of engineered cementitious composite (ECC)–concrete hybrid composite beams reinforced with fiber-reinforced polymer (FRP) bars and steel bars. ...

A timber composite beam consists of a cross-laminated timber (CLT) panel attached to a girder such as a laminated veneer lumber (LVL) beam. Under positive bending moment, part of the CLT pa...

The hybrid composite beam (HCB) is an innovative idea that incorporates traditional construction materials (i.e., steel and concrete) with fiber-reinforced polymer (FRP) composites in an ef...

The concept, basic principle, and characteristics of twice-prestressed composite beam are introduced, and the mechanical performance, deformation performance, and creep stress redistribution of the horizontal interface of twice-prestressed beam are discussed. In addition, previous studies regarding the application of twice-prestressed composite beams in highway bridges are summarized and analyzed. It is concluded that the twice-prestressed composite beam can decrease the creep camber of a prestressed concrete beam by more than 50%; thus, the contradiction of reducing creep camber and improving the safety of section crack resistance can be effectively resolved. Moreover, twice-prestressed composite beam can save approximately 10% of prestressed tendons and has comprehensive technical and economical advantages in highway ultrathin beam bridges and urban overpass bridges. Future research of twice-prestressed composite beam will focus on the design method, connection model, structure, and shear performance of horizontal interface in addition to the construction technology.

Perforated shear connectors (PSCs) in steel–concrete composite joints are usually deeply embedded in concrete, and the perforated plate thickness varies significantly, which is different from those in a steel–concrete composite beam. In this study, two types of push-out tests (24 specimens in total) were conducted to compare the mechanical behavior of PSCs used in steel–concrete composite joints with that in composite beams. The testing variables include the push-out test arrangement, plate thickness, and concrete compressive strength. The experimental results are presented and discussed, focusing on the shear resistance, load-slip behavior, and failure modes. Finally, the experimental results were compared with existing shear resistance equations to evaluate their applicability for PSCs in composite joints.

A new composite floor system was developed to reduce floor-to-floor height and to improve structural capacity and fire resistance as compared with existing encased composite floor systems. The proposed system is composed of asymmetric steel beams with web openings, a biaxial hollow concrete slab, and glass fiber-reinforced plastic (GFRP) plates. The shear resistance of the typical composite beams is commonly determined based on the shear strength of the steel web alone. However, for the proposed system, because the steel web has several circular openings, the concrete contribution to the shear resistance should be included in the design equation. In this paper, tests and finite-element analyses were conducted to evaluate the contribution of the shear-resisting components in the proposed system. An asymmetric steel beam with web openings, inner concrete panels, and a biaxial hollow concrete slab within the effective width for shear were considered as shear-resisting components. Each component fully...

This paper summarizes the results of experimental investigations on steel composite beams with simple connections at elevated temperatures. In the United States, three different types of simple connections are most commonly used in building construction with steel composite beams: (1) double-angle connections; (2) single-angle connections; and (3) shear-tab connections. A testing program was conducted to examine the structural behavior of all three of these connections at elevated temperatures. Each specimen consisted of a steel composite beam attached to a loading frame with simple connections. The specimens were subjected to controlled heating and cooling curves while the loading frames were fire protected and designed to remain in the elastic range. The shear-tab connections showed the largest connection rotation, but they fractured during the cooling phase of the tests. The prying of the angles in the double-angle and single-angle connection during the tests provided ductility to prevent fract...

Composite timber beams strengthened by U-shape steel sections and carbon fiber–reinforced plastic (CFRP) are studied experimentally in this paper. Specimens with various strengthening, i.e., steel only, CFRP only, and a combination of the two, were considered under three-point flexural tests. Failure, displacement and strain response, ductility, bending capacity, and structural efficiency were evaluated for the present tested models. Dramatic enhancement of the capacity in addition to improved deflection and ductility were gained for the strengthened beams relative to the plain specimens, indicating the effectiveness of the reinforcement on the flexural strength of such composite beams.

In conventional timber–concrete composite (TCC) beams, timber joists and concrete slabs are connected permanently; however, the permanent timber–concrete connections can hinder repairing and reusing of structural components and accordingly it reduces the sustainability of construction. This paper deals with development and structural performance of a few novel deconstructable TCC connections that can facilitate recycling and reusing of construction materials. The structural performance of 16 different sets of novel deconstructable TCC connections under shear loads is investigated by push-out tests followed by bending tests on nine TCC beams under service and ultimate loads. The behavior of connections and beams are characterized and the TCC connections with the highest strength and stiffness and feasibility for construction and dismantling are identified.

The fatigue life of composite beam samples were measured by flexural fatigue test under different bonding oil contents, temperatures, and loads. The measurement was conducted to study the influence of interlayer contact on the fatigue life of asphalt pavement and to fine tune the pavement fatigue model. The results show the following: (1) The integrity and fatigue life of asphalt pavement decreases because of interlayer contact. (2) Fatigue life first increases then decreases with increasing bonding oil content. An optimum bonding oil content increases fatigue resistance to a higher level. (3) Fatigue failure more readily occurs at normal temperatures than at low temperatures. In addition, fatigue life significantly decreases when pavement is exposed to overweight vehicles. The relationship of fatigue life with bonding oil content, temperature, and load was identified and total fatigue equations were established.

The experimental results of three full-scale two-story, two-bay, composite steel frames under furnace loading are described briefly. During tests, the composite beams and steel columns were exposed to fire, and only the beam-to-column connections of the tested frames were protected. The furnace temperature, composite steel beam temperature, steel column temperature, horizontal displacements of the columns, and vertical deflections of the composite beams as well as the complete deformation process of the test frames observed during the heating phase and the cooling phase are given. By introducing the slope-deflection equations and joint equilibrium conditions at each joint, the critical temperatures of the buckling of two-story, two-bay, composite steel frames are determined for different furnace scenarios; therefore, this method can consider the effect of the axial force at different levels. The calculated critical temperatures agree well with the experimental results.

This paper presents the results from experimental investigations focused on the thermal and structural behavior of composite beams with shear connections subjected to fire conditions. Five partial composite beams with flat, lightweight concrete slabs were designed according to current U.S. codes and standards. Vertical loading was applied to the composite beams, and the surfaces of the steel and concrete were heated using high-temperature ceramic radiant heaters. Variations in the loading and heating protocol provided insight into the mechanical response and failure modes of composite beams and connections. There was an overall reduction in the composite beam load-carrying capacity due to heating, both at elevated temperatures as well as postfire ambient conditions. Concrete compression failure occurred at moderate steel temperatures (350–500°C) combined with overloading. In cases where service level loading was applied, the composite beams and connections sustained the loading and heating up to s...

Timber-concrete composite beams are an increasingly common design solution for medium-to-long span floors in new buildings. Thus, there is a significant need for accurate models and analysis tools to predict the response and performance of timber-concrete composite beams. In this paper, a nonlinear finite-element (FE) frame model with deformable shear connection is adopted to estimate the short-term structural response of timber-concrete composite beams for which experimental results are available. The FE model is used in conjunction with a probabilistic analysis methodology, which explicitly accounts for the uncertainties in the parameters that describe the constitutive models for timber, concrete, and shear connectors. The objectives of this study are (1) the evaluation of the variability of global and local structural response quantities owing to the uncertainties in the constitutive parameters of timber, concrete, and shear connectors; and (2) the analysis of the correlation between experiment...

Posttensioning has been used successfully to improve the performance of existing bridge structures. High-strength tendons can be used to effectively increase the ultimate capacity of composite beams. The main purpose of this paper is to develop a reliable three-dimensional (3D) finite-element (FE) model to simulate the nonlinear flexural behavior of steel–concrete composite beams strengthened with externally posttensioned tendons. A 3D FE model was used, where the nonlinear material behavior and geometrical analysis based on incremental–iterative load methods were adopted. The effective posttensioning stress was applied as initial strain in the link element used to model the tendons. To verify the accuracy of the developed 3D FE model, comparison between the FE analysis results and previous experimental results is presented. In-depth study has been carried out on the overall behavior of the strengthened beam and the effect of external posttensioning on stiffness, induced stresses, slippage between...

Thin webs of glass-fiber-reinforced polymer (GFRP) girders are sensitive to shear buckling, which can be considered an in-plane biaxial compression-tension buckling problem, according to the rotated stress field theory. An extensive experimental study was performed, which shows that an increasing transverse tension load significantly increases the buckling and ultimate loads caused by a decrease in the initial imperfections and additional stabilizing effects. The stacking sequence also greatly influenced the buckling behavior. Higher bending stiffness in the compression direction increased the buckling and ultimate loads, while higher bending stiffness in the tension direction changed the buckling mode shape. The general solution obtained using the Fok model accurately modeled the experimental results, while the simplified solution (modified Southwell method) provided accurate results only at higher tension loads. DOI: 10.1061/(ASCE)CC.1943-5614.0000167. (C) 2011 American Society of Civil Engineers.

Small timber layers can be mechanically laminated into a larger timber cross section using shear keys to prevent slip between the layers. These mechanically laminated beams are commonly referred to as keyed beams and their use has a strong historical precedence. Current building codes and design standards do not provide adequate guidelines for the analysis of keyed beams. This project examined the applicability of an interlayer slip model to predict the partially composite behavior of the keyed beams. Solutions to the interlayer slip model for common loading configurations were developed, as were stiffness parameters for the semirigid wooden shear keys used to provide composite action. Small and full-scale testing of timber components was also performed to verify the interlayer slip model’s ability to predict the stiffness of specific keyed beam specimens. A comparison of the interlayer slip model to historical keyed beam test data was also conducted. The interlayer stiffness model, as well as the analyti...

The composite interaction in timber-concrete beams is usually achieved with mechanical devices, such as shear connectors or plates driven into the materials. However, this connecting system shows some inherent inconveniences, such as the need for drillings and the limited mechanical improvement owing to interface slip. Using adhesives instead of mechanical connectors might attenuate these drawbacks. However, engineers are hesitant to apply adhesives for structural purposes, mostly because of the different thermohygrometric behavior of the adhesive and the connected material(s). This is particularly concerning timber because its hysteretic response to moisture may cause interface delamination. Therefore, as a preliminary stage for the test of composite beams, an extensive experimental campaign on small-size specimens was performed. The study focused on the shear strength at the interface and the role of some factors. Several series were considered by changing those parameters, and the results were compared. Both prefabricated and cast-on-site concrete specimens were considered. The results show that this system looks suitable for structural application, at least under steady dry conditions.

Flooring systems containing steel-concrete composite beams are common in steel frame structures and it is widely recognized that their behavior under fire loading is profoundly different to that of simply supported composite beams under fire loading. This difference in behavior is due to the presence of restraints provided by cooler members in a compartment fire in a composite frame structure and there is extensive evidence from fire tests that composite beams with unprotected steel components in steel frames perform much better than simply supported composite beams with unprotected steel components. In order to model the structural response of a composite beam restrained in this way at elevated temperature, recourse is needed to a geometric nonlinear formulation, since the transverse beam deflections are large and interact with the substantial axial compressive force in the member at the early stages of the fire. This paper presents such a formulation, which incorporates partial interaction between the concrete slab and steel component, as well as the degradation of the stiffnesses of the components of the composite beam prior to yield at elevated temperature. The generic technique that is developed is shown to agree with solutions reported elsewhere and provides a structural model for the response of a composite beam in fire with the potential for inclusion in prescriptive code rules for rational fire engineering based designs.

As the number of high-rise buildings increases, the floor-to-floor height has been considered as a significant component due to limited city areas. To reduce the floor-to-floor height, a newly developed composite beam using asymmetric steel section with web opening was proposed and experimentally explored. Shear connectors are not used for the proposed composite beam. Instead, longitudinal shear strength is obtained through the bond strength of the interface between concrete and steel, and the bearing strength of the opened web area. In this paper, the flexural behavior of the proposed beam was assessed using the simple beam test. For comparison, a slim floor beam was tested. A bare steel beam was also tested to evaluate resistance under construction loads. The proposed system showed satisfactory horizontal shear resistance and good composite behavior.

Shear-bearing bearing capacity of stud within negative moment region of continuous steel-concrete composite beams was studied. Based on 3 factors of stud diameter and concrete intensity and...

The combined effects of creep and shrinkage of concrete and relaxation of prestressing tendons cause gradual changes in the internal forces and deflections of composite beams. However, most of the research work conducted on prestressed steel–concrete composite beams has focused on short-term behavior; research findings on the long-term behavior are scarce in the literature. For the wide-scale use of prestressed composite beams in civil engineering applications, the long-term behavior must be investigated. This paper presents an experimental program designed to examine the long-term behavior of prestressed composite beams under sustained load conditions for one year. The test program consisted of two prestressed composite beams and one nonprestressed composite beam. On the basis of the age-adjusted effective modulus method and energy principle, the creep stiffness matrix and the creep force matrix of prestressed composite beams were developed. A time-dependent analytical model is presented to predict the l...

The paper investigates the stiffness and strength of composite laminated veneer lumber (LVL) and concrete beams intended for use in long-span flooring systems. Quasi-static bending tests and impact tests were conducted on four, 6 m long specimens to observe the failure mechanisms and to estimate the static and dynamic properties of the systems. One specimen, with a plain LVL member, a strong shear connection, and a concrete slab, was used as a control. The other three specimens investigated the use of (i) a proprietary, lightweight nonstructural concrete panel as a slab; (ii) a straight prestressing tendon and a strong shear connection; and (iii) a draped prestressing tendon and a weaker shear connection. All four specimens had a T-shaped cross section, with the slab supported by either one or two LVL beams. The stiffness of control beam, which is mostly related to the stiffness of the shear connection, is shown to be almost three times that of a bare LVL beam, but the beam is only 74% stronger than the bare beam. The prestressing tendons are shown to have little effect on the stiffness and strength, but reduce the deflection due to permanent load, particularly when they are draped. The proprietary lightweight concrete panels are shown to provide little structural benefit.