Composite Structural Systems Research Articles

Predictive control of seismic responses of a novel seismic isolation – non-seismic isolation composite structure system based on Levenberg-Marquardt algorithm

In order to reduce the seismic responses of adjacent structures, this paper proposes a novel seismic isolation – non-seismic isolation composite structure system, which is made up of a seismic isolation structure and a non-seismic isolation structure adjoined via controllers, and whose seismic responses are controlled with good effect by the principle of interacting control between the seismic isolation and non-seismic isolation structures. With a novel five-layer seismic isolation – non-seismic isolation composite structure system as an example, this paper builds a calculation model for the structure, derives the kinematic equations for the interacting control within this structural system, and adopts linear quadratic regulator (LQR) optimal control to analyze the control effect of this system and study the effect of time lag on the interacting control within this system. To address the issue of time lag in the interacting control between structures, an improved BP algorithm (Levenberg-Marquardt) is further adopted to set up a four-layer feedforward network to forecast the seismic responses of this novel composite structure system; the network structure is trained using the data acquired from LQR control under the action of the first 500 sampling points of the seismic motion taft, and the structure undergoes predictive control using the untrained seismic motion data of El Centro. The research results show that the interacting control of such a novel seismic isolation – non-seismic isolation composite structure system can achieve a good result, with the displacement response of the topmost layers of both structures decreasing by above 50 %; time lag may have an adverse effect on the control of the composite structure system, so that the structure’s seismic response increases by 20 % ∼ 40 %. The issue of time lag in interacting control can be addressed by adopting neutral network for predictive control, so that the structure’s seismic responses are 11 % ∼ 25 % lower than when it is not predicted. Levenberg-Marquardt algorithm demonstrates a strong learning ability and a curve approximation ability. The time history curves of the structure’s seismic responses under predictive control of this algorithm are highly overlapped with the time history curves under LQR optimal control with zero time lag.

RESISTANT MECHANISM AND MECHANICAL PROPERTY OF MASONRY HYBRID STRUCTURES OF RAMMED EARTH-LIGHT WEIGHT STEEL MEMBERS

In previous researches, composite structure system made of rammed earth and steel member has been proposed, and mechanical properties and deformation behavior were investigated. This paper suggests an improved composite structural system made of rammed earth and light wight steel member. From the loading tests and a finite element analysis as parameter with states of open/close of wall and thickness of steel, the effective resistant mechanism with adjacent composite structure blocks is appeared, and the combined effect for strength and rigidity is obtained. From analytical results, the relationship between the stress state and the thickness of steel members is investigated.

INNOVATIVE COMPOSITE STRUCTURAL SYSTEMS FOR MODULAR TALL BUILDINGS

AbstractModular or offsite construction is believed to shape the future of the construction industry as it possesses significant benefits over traditional onsite construction methods. However, most of its application are limited to steel or concrete buildings. Although steel‐concrete composite structural system has many merits over the steel and concrete systems, its application in modular buildings is very limited. This paper explores recent developments of composite systems for modular high‐rise buildings. They include modular units for resisting vertical gravity loads and lateral structural systems for resisting horizontal forces from wind and earthquake loadings and progressive collapse due to accidental loads such as fire, explosions and impact. Various inter‐module joining methods developed in the literature will also be reviewed. Finally, a case study of the most efficient connection is presented to explore its applicability to high‐rise modular buildings.

Experimental and numerical investigation of core splicing configurations in an advanced composite sandwich structural system

In this study, an investigation is presented on the effects of the honeycomb core splice gaps on the performance of advanced composite sandwich structures consisting of aluminum honeycomb core and carbon-fiber/epoxy facesheets. The experimental and numerical investigation explores the effects of core thickness, facesheet thickness, splice gap width, and the presence of core splice adhesive on the structural response of the composite sandwich structure. The specimens fabricated with the splices exposed to primarily bending and shear to understand further how the core splice interacts with the overall structural response under such loading conditions. In addition, 3D finite element models investigated the failure modes in the specimens by examining the strain fields for core-spliced sections of the sandwich structure under the experimentally observed loading conditions. Various failure modes are observed in the experiments ranging from core shear failure, facesheet debonding, or fracture depending on the location of the core splice, core, and the facesheet properties. The results illustrate the importance of proper detailing and analysis of core splices in composite structures made from sandwich designs.

Experimental study of seismic performance of PEC column-steel beam 3D frame with endplate connection

The design and quasi-static test of a 1/3 scale down the single-story partially-encased composite structure of steel and concrete (PEC) column-steel beam 3D frame with endplate connection has been completed, confirming that the PEC is a new composite structural system that combines the advantages of concrete and steel structures. The damage mode and yielding mechanism of the frame by strain variation were analyzed, and its seismic performance was evaluated. The results show that the concrete filling in the node domain of the PEC column can activate the strut and tie mechanism for transferring the compression force between the column and the slab. The yield mechanism of the frame is “beam-column-node,” which satisfies the design principles of “strong column but weak beam” and “strong connection but weak component.” The full hysteresis curve has excellent energy dissipation capability. The strength degradation is stable, and the ductility coefficient is >2.85. The elastic inter-story and the elastic-plastic inter-story displacement drift meet the design requirements, which indicates that the frame has a stable bearing capacity, excellent flexibility, and anti-collapse capacity.

Seismic Capacity Estimation for Composite Multi-storeyed RC buildings

Seismic hazard happens to be one of the most devastative natural hazards to be faced by mankind. In view of urbanization and knowledge gained from past natural hazards, several urban cities have seen a transformation in building their habitats. These range from regular, irregular multistoried Reinforced Concrete (RC) buildings to several composite multi storeyed RC buildings due to certain inherent functional benefits (viz., ventilation, parking space, ease of construction etc.,). The existing seismic code regulations provided by BIS (Bureau of Indian Standards) do not specify any approach to arrive at appropriate design seismic forces and capacity for composite multi storeyed buildings. Therefore, it is imminent to assess the structural behaviour of these multistoried composite RC buildings under earthquake forces at the site location to provide a safe and functional configuration. Hence an attempt has been made in this study to analytically compare regular and composite RC building models having similar Plan and Height. The multistoried RC building configurations considered in this study comprises of regular RC building as well as RC building frame coupled with steel joists at certain locations to represent a composite structural system. These models are further analyzed to arrive at inherent nonlinear seismic capacity, ductility and design seismic forces necessary to be considered during design of RC building structure. Hence, a typical hypothetical G+5 regular and composite multistoried buildings were modelled and analysed using the nonlinear static (pushover analysis) approach. The outcomes of these analyses clearly portrays the variation in dynamic characteristics of the building frames represented in terms of its time period, inelastic capacity and response reduction factor (R). Moreover, the present study emphasizes to analytically evaluate the design seismic forces necessary for earthquake resistant design of composite buildings in any urban environment albeit the changes in structural configurations.

Seismic Response Analysis of Steel–Concrete Composite Frame Structures with URSP Connectors

The uplift-restricted and slip-permitted (URSP) connector is a new type of connector used in steel-concrete composite structures that has been proven to improve the structural performance of negative moment regions. Since this connector changes the interface restraint between the slab and steel beam, there is an imperative to study the seismic performance of steel-concrete composite frame systems with this new type of connector. In this study, the dynamic behavior of composite frame structures with URSP connectors under seismic loads was numerically investigated. First, a beam-shell mixed model was used and complex interfaces of different connectors were considered while establishing a numerical model to conduct elasto-plastic time history analysis under various seismic loads. This numerical model was validated with the frame sub-assemblage experimental results of quasi-static cyclic tests. Second, the model analysis results of structures with URSP connectors were obtained and compared with those of traditional structures. Third, dynamic response results including roof displacement, inter-story displacement, and the distribution and failure modes of plastic hinges were analyzed and compared. The comparisons indicated that the arrangement of full-span URSP connectors had a non-negligible influence on the dynamic behavior of the systems. The arrangement increased the maximum inter-story displacement by 31.5% and induced adverse effects in certain cases, which is not suggested in the application of URSP connectors. The partial arrangement of URSP connectors had little influence on the dynamic behavior of the systems, and the frame systems still showed a good seismic performance, which was the same as the traditional composite structural system. These findings may promote the application of URSP connectors in composite structures.

A New, Green, Recyclable Fireproof Insulation Board for Use in Integrated Composite Structure Fire Protection Systems

A fireproof insulation board can be recycled, and the raw materials used in its production are very environmentally friendly, non-toxic and non-hazardous, and bring no harm to the human body and the surrounding environment. One practical application of fireproof insulation board is in an integrated composite structural fire protection system, which is a multidimensional comprehensive structural fire protection system proposed for the combined construction of buildings with different functions, such as horizontal and vertical, to ensure overall safety in the event of a building fire. The specific new technology of this new system includes an integrated structural fire protection system composed of a 3.00 h fire insulation board, which comes from the collection of textile scraps consisting of metals and buttons removed from clothes. To prove the effectiveness of this fireproof insulation board, its parameters were collected and put into FDS (FirG Dynamics Simulator, a CFD model of fluid flow during combustion developed by the National Institute of Standards and Technology), the fire safety goals considering the safety of building and personnel were established, and fire scene design based on the statistics of fire data and building codes was generated to test the safety of evacuation. To ensure the reliability of simulation results, an on-site physical fire test was conducted with the recycled insulation board. The result shows that the function of recycled board optimizes the phased evacuation design plan of personnel and solves the design difficulties of expanding fire zones and long evacuation distances when used in warehouses. Through the innovative design of the roof opening rate set at 30% and a hole spacing of 60 m, this underground fireproof insulation board is guaranteed to possess natural smoke exhaust conditions and can be used to improve public safety areas.

Flexural behaviour of a new timber-concrete composite structural flooring system. Full scale testing

Timber-concrete composite systems are a high-performance alternative for building floors, of great interest in the current context of environmental concerns. Looking for a more eco-friendly solution, the paper presents a new flooring system with a wood-concrete connection that does not require adhesives or special metal elements. Four-point bending tests were performed on TCC flooring samples with a span of 6.0, 7.2 and 8.4 m. Its cross section was a prefabricated piece in the shape of an inverted T made up of a lower glulam flange, glued together with a central plywood rib with aligned holes in its upper part that go through the entire thickness of the plywood. The set was completed with a top layer of poured-in-place concrete. The connection between both materials is achieved by penetrating the concrete into the rib holes. Additionally, corrugated steel bars were placed through said holes to achieve ductile behaviour. In all cases, a slenderness ratio of L/24 was used. The experimental results showed that the lowest value of ultimate load obtained was 4.3 times higher than the total service load estimated for a building for public use (9 kN/m2). The maximum deflection of the total load was between L/573 and L/709 for the loads corresponding to a building for public use (9 kN/m2) and between L/1069 and L/1340 for the case of residential type building (5 kN/m2). An analysis of the effects of vibrations in the service limit state in relation to user comfort has been included. The results indicate that the system satisfies the requirements for the intended uses.Consequently, the proposed solution shows its effectiveness both in terms of strength and stiffness for the construction of light floors, being easy to build and having high performance.

BIM-based life cycle assessment for different structural system scenarios of a residential building

This study pinpoints the benefit of integrating Life Cycle Assessment (LCA) and Building information modelling (BIM) for different design scenarios of a residential building’s structural system; (1) reinforced concrete solid slab system, (2) steel and (3) composite structural system. The environmental impacts for each scenario are evaluated, providing insights into the contribution of (1) building life cycle stages, (2) structural systems and (3) building materials. Construction cost and time were also assessed and compared for each. The results show how LCA-BIM integration can streamline the environmental stewardship and prioritize action; showing that the building operation stage, the steel structural system, slabs and beams as well as reinforced concrete have the highest environmental impact, respectively. Hence, this calls for acting on building operation as well as the proper design of building elements and selection of building materials to reduce the associated environmental burden resulting from the building process.

Energy-based time equivalent method for evaluating the fire resistance of timber–concrete composite structures exposed to travelling fires

Timber–concrete composite (TCC) structure system is most frequently used in large-span structures. Recently, a performance-based fire safety design method named improved travelling fires methodology (iTFM), which is suitable for long-span structures, has been developed. In this article, an energy-based time equivalent method (EBTEM) is proposed, while its effectiveness is experimentally verified. The proposed method can be used to evaluate the fire resistance of the TCC structures subjected to iTFM fires. The results indicated that the damage degree at different spatial positions of the TCC structure under the same fire size was different, and the location with the least and most serious damages occurs towards the beginning and middle of the fire path, respectively. The results show that this difference in damage degree mainly depends on the fire size, and the difference becomes less pronounced as the fire size increases. Concomitantly, it can be obtained that the damage degree under the different fire sizes was different, and the smaller the fire size, the greater the damage degree. Hence, when the EBTEM is adopted to design the TCC structures exposed to iTFM fires, the setting of fire protection target is largely determined by the actual fire size.

Boundary continuity effect on performance of composite beam-slab sub-assemblages at elevated temperature

The behaviour of composite beam-slab structural system under fire condition has been investigated in the past few decades. However, previous research works mainly focused on isolated beam-slab sub-assemblages. In this paper, the boundary continuity effect on structural behaviour of composite beam-slab sub-assemblages subject to fire is investigated, where three different boundary continuities are considered, namely, internal, edge, and corner composite slab. Six specimens with a single unprotected interior beam were tested to failure, and two aspect ratios of 1 and 1.5 for each boundary condition were included. A total vertical load of 100 kN was applied to each specimen, which was heated by an electrical heating furnace from ambient temperature to 1000 °C within 1 h and maintained at 1000 °C until failure of the specimen occurred. The internal composite slab panel with an aspect ratio of 1 had the longest failure time and the edge composite slab panel with an aspect ratio of 1.5 sustained the longest duration. Finite Element (FE) models of the specimens validated by the experimental results were adopted to study membrane forces in the beam-slab sub-assemblage. Numerical simulations showed that different boundary continuities resulted in different membrane forces, and both the axial and rotational stiffness values in the direction of continuous edges were much greater than those of discontinuous edges for typical composite slabs. Moreover, the authors proposed minor amendments to Bailey-BRE method for calculating the enhanced load capacity at ultimate limit state and showed that the predictions were conservative when compared with test results.

Parametric Finite Element Analyses of Lightweight Cold‐formed Steel‐concrete Composite Floor Beams

AbstractComposite structural systems have many benefits, such as a high degree of prefabrication, reusability and long span capability. The main advantage of such systems is manifested through the optimal utilisation of structural steel and concrete. Additionally, allowing for demountability and reusability, the system can also result in a much smaller carbon footprint at the end of life. These advantages are particularly emphasised with the implementation of cold‐formed steel sections. This paper presents an innovative solution for a composite floor structure system consisting of built‐up cold‐formed profiles and concrete slabs made with profiled sheets. The influence of the corrugated web thickness, type of connection between steel beam elements, the degree of shear connection and steel beam height on the overall behaviour of the composite system is analysed. The performed FE analyses showed that the influence of connections between steel beam elements and the degree of shear connection had the most significant impact on system behaviour. In contrast, the steel beam height, the corrugated web thickness and spot weld density had less influence on the analysed composite system behaviour. The obtained results provide the basis for implementing laboratory research on the proposed system.

Response adjustable performance of a visco-elastomer sandwich plate with harmonic parameters and distributed supported masses under random loading

Vibration control of composite structures with distributed masses under random loadings is a significant issue. Adjustability of dynamic characteristics including response spectrum peaks and valleys is important for structural vibration control. The vibration control design in space contains structure and conformation designs which combination results in periodic composite structures. In the present paper, spatial periodicity control design is proposed. Stochastic response adjustable performance of a visco-elastomer sandwich plate with harmonic distribution of geometrical and physical parameters and distributed supported masses under random base motion loading is studied. Both facial layer thickness and core layer modulus of the sandwich plate are considered as harmonic distribution in length and width directions as well as periodically distributed masses. Partial differential equations of coupling motions of the sandwich plate system are derived and converted into ordinary differential equations for multi-mode coupling vibration. Generalized stiffness, damping, and mass coefficients are functions of the harmonic distribution parameters. An analysis solution with frequency response function and response spectral density expressions of the sandwich plate system is obtained. Numerical results are given to show the response adjustable performance through the harmonic geometrical and physical parameters and distributed masses. The results have a potential application to stochastic vibration control or dynamic optimization design of smart composite structure systems.

New modular precast composite shear wall structural system and experimental study on its seismic performance

Modular buildings are becoming increasingly popular due to their higher construction efficiency, better quality control and less resource consumption. In this study, a new modular precast composite shear wall structural system was proposed and the joint design principle was given. The new modular precast structural system adopted volumetric concrete modules and dry bolted connections for fully precast construction and demountable ability. This paper presented comparative shaking table tests and comprehensive test result analyses on a modular precast composite shear wall model and a cast-in-place shear wall model. The fundamental frequency of the modular precast model was 10.2% lower than that of the cast-in-place model because of the semi-rigid joints. The modular precast model exhibited comparable dynamic responses with the cast-in-place model, but showed less severe shear wall damage under the same intensity level test due to the small gap opening of vertical joints. The screw fracture and nut slip in vertical joints induced the failure of the modular precast model. The modular precast model exhibited better energy dissipation performance than the cast-in-place model. The adjoining concrete modules could achieve satisfactory synergistic working performance, and the horizontal joints remained elastic throughout the tests. The excellent test performance of modular precast composite shear wall model confirmed the feasibility of the proposed structural system in concrete modular buildings.

Damage Detection in Steel-Concrete Composite Structures by Impact Hammer Modal Testing and Experimental Validation.

Steel–concrete composite systems are an efficient alternative to mid- and high-rise building structures because of their high strength-to-weight ratio when compared to traditional concrete or steel constructive systems. Nevertheless, composite structural systems are susceptible to damage due to, for example, deficient construction processes, errors in design and detailing, steel corrosion, and the drying shrinkage of concrete. As a consequence, the overall strength of the structure may be significantly decreased. In view of the relevance of this subject, the present paper addresses the damage detection problem in a steel–concrete composite structure with an impact-hammer-based modal testing procedure. The mathematical formulation adopted in this work allows for the identification of regions where stiffness varies with respect to an initial virgin state without the need for theoretical models of the undamaged structure (such as finite element models). Since mode shape curvatures change due to the loss of stiffness at the presence of cracks, a change in curvature was adopted as a criterion to quantify stiffness reduction. A stiffness variability index based on two-dimensional mode shape curvatures is generated for several points on the structure, resulting in a damage distribution pattern. Our numerical predictions were compared with experimentally measured data in a full-scale steel–concrete composite beam subjected to bending and were successfully validated. The present damage detection strategy provides further insight into the failure mechanisms of steel–concrete composite structures, and promotes the future development of safer and more reliable infrastructures.

Research on damping performance and parameter influence of new frame-MRD-core tube composite structural system

The position of the plastic hinge is uncertain due to the design and construction of the frame-core tube structural system, causing problems such as reduced collapse resistance and difficulty in repairing after an earthquake. To address these problems, this paper proposes a new type of frame-magnetorheologicaldamper (MRD)-core tube composite damping structural system. In this system, the frame and the core tube are two independent structures connected by MRD. Based on the instantaneous optimal control algorithm, the semi-active control strategy of MRD is designed. The relative motion between structures is used to provide damping force, and the vibration control equation is established. In this paper, a 10-story reinforced concrete frame-MRD-core tube composite structural system is taken as an example, and the El Centro (NS, 1940) ground motion with the peak acceleration of 220 cm· S-2 is used as the lateral load for horizontal seismic time-history analysis. MATLAB is employed to perform numerical simulation calculations to investigate its damping effect and related influence parameters. Compared with the traditional frame-core tube structural system, the new system can reduce the top floor displacement and the maximum interstory drift by more than 50% and reduce the top floor acceleration of the frame and core tube by 65% and 40%, respectively. Furthermore, reasonably optimizing the position of the control floor can reduce the number of dampers. When the interstory control is implemented, the total control force of dampers can be reduced by 18% compared to the full-story control. This article provides a new damping idea and theoretical reference basis for the engineering design and application of the frame-core tube composite structural system.

Dynamic Performance Analysis by Laboratory Tests of a Sustainable Prefabricated Composite Structural Wall System

In recent decades, steel frames infilled with precast load-bearing walls have been successfully employed as lateral load-resisting structural systems in high-rise buildings. This is due to their structural efficiency as outer and major inner facades and to the higher construction speed of the building. This paper presents a detailed experimental investigation of a sustainable, prefabricated, composite structural wall system, using a representative test model named the Precast Concrete Steel Panel-Infilled Steel Frame (PCSP-ISF) in full-scale dimensions and subjected to in-plane cyclic loading. A series of experiments was conducted on critical structural specimens, including three-point bending, concentric axial compression, and diagonal compression, together with additional cycling loading tests on steel connection joint specimens, with the aim of validating the reliability and the structural response of the connections. The resulting test data and the observed failure mechanisms are discussed carefully to optimise the sustainable structural performance of the system. A theoretical approach for the evaluation of the shear capacity of the total frame system is also discussed to expand the experimental results for several numerical and experimental research cases. The failure mechanism of this module was formed by a combination of developed plastic hinges on the steel joints and diagonal cracks on the concrete panel. The obtained hysteretic behavior of the system at a parameter with major impact is mainly analysed and discussed. The outcomes indicate a satisfactory and sustainable seismic performance of the PCSP-ISF model, indicating that it can be a very promising lateral load-resisting system for earthquake-prone regions.

Numerical investigation on dynamic performance of reinforced ultra‐high ductile concrete–ultra‐high performance concrete panel under explosion

AbstractUltra‐high ductile concrete (UHDC) is known for ultra‐high tensile ductility, and ultra‐high performance concrete (UHPC) has ultra‐high compressive strength. Reinforced UHDC–UHPC panels that are made of UHDC and UHPC (i.e., hybrid panels) are expected to have excellent blast‐resistance capacity. However, only limited research is devoted to study the dynamic performance of the panels under explosion. To further investigate the dynamic performance of such kind of composite structural system, numerical simulations are carried out through LS‐DYNA. The developed material models are used for describing the mechanical properties of UHDC, UHPC and steel bars at high strain rate. Based on the corresponding field blast test results, the feasibility and accuracy of the adopted finite element models are validated. Furthermore, parameter analysis is applied for investigating the effects of scale distance, reinforcement ratio and concrete type on the dynamic performance. It is concluded that the maximum deflection of reinforced UHDC–UHPC panels reduces with increasing scale distance and reinforcement ratio. Reinforced UHDC–UHPC panels possess excellent blast‐resistance capacity in comparison with reinforced concrete panels.

Finite Element Analysis Study of CJS Composite Structural System with CFT Columns and Composite Beams

Finite Element Analysis Study of CJS Composite Structural System with CFT Columns and Composite Beams