Hybrid Structural Systems Research Articles

Hybrid structural systems for timber high-rise buildings

Hybrid structural systems for timber high-rise buildings

Experimental investigation on the shear performance of hybrid structures comprising textile reinforced concrete stay-in-place formwork and reinforced concrete

Recently, the application of textile-reinforced concrete (TRC) in thin-walled precast structures has gained significant attention. Among these innovations, the combination of TRC and reinforced concrete (RC) has emerged as an effective method for creating hybrid structural systems. This paper presents the experimental results analyzing the shear behavior of a hybrid deck slab structure consisting of TRC stay-in-place (SiP) formwork and RC components. Shear performance was evaluated using 3-point bending tests on four large-scale specimens with aspect ratios (a/d) varying from 1.6 to 2.3. The average load carried by the TRC SiP formwork prior to failure—due to textile reinforcement rupture—was approximately 26.3 kN, with compressive strains at the top edge ranging from 2.8 to 3.4 ‰, just below the concrete's ultimate strain. The findings demonstrate the versatility of TRC SiP-formwork, highlighting its adaptable cross-section and substantial load-bearing capabilities, making it particularly suitable for composite bridge deck applications. The specimens experienced both shear compression and diagonal shear failures. Moreover, the TRC SiP-formwork effectively mitigated transverse cracking at the interface, enhancing bond strength and improving overall structural performance

Experimental and parametric study on friction-type high-strength bolted connections between steel frames and cross-laminated timber infill walls

Timber-steel hybrid structural systems provide a prospective solution for utilizing timber in multi-storey and high-rise buildings. The system of steel frame with infilled cross-laminated timber (CLT) shear walls is an effective hybrid timber-steel one. In the design of this kind of hybrid system, the connections between CLT walls and steel frame beams are key issues, because they have great impacts on the distribution of lateral forces in structures. In this paper, a friction-type high-strength bolted connection (FHBC) between CLT walls and steel frame beams is proposed. To investigate the performance of the proposed FHBC, experiments were conducted on the FHBCs fabricated with three- and five-ply CLT. The mechanical behaviors of the connections were evaluated. The pretension loss in the tested FHBCs with three-layer CLT is less than 15 % within a displacement of 10 mm. Besides, enhancement of axial force in the high-strength bolt was observed in the five-layer connections during the loading procedure. Theoretical analysis was performed to provide recommendations on the initial pretension force of FHBCs. Furthermore, a solid element-based numerical model was developed and validated by the experimental results. The parametric analysis was conducted to investigate the effect of friction coefficient and initial pretension force on the mechanical behaviors of FHBC. The numerical simulation results show that the greater the initial pretension force is, the bigger the slip activation force and ultimate load-carrying capacity of the FHBC are. When the friction coefficient between CLT wall and steel beam is greater than 0.4, the ultimate load-carrying capacity does not increase much. The experimental and numerical results demonstrate that such connections can provide sufficient stiffness, strength, and ductility to transfer the shear force between the CLT shear walls and the steel frame beams.

Evaluation of vibration properties of an 18-story mass timber–concrete hybrid building by on-site vibration tests

Timber–concrete hybrid structural systems are a practical option to provide tall mass timber buildings with a lateral load-resisting system. This paper discusses the dynamic behavior of an 18-story timber–concrete hybrid building based on the vibration properties evaluated by on-site vibration tests. First, microtremor measurements and human-powered excitation tests were carried out and the obtained vibration data were analyzed using a stochastic subspace identification method to derive natural frequencies, damping ratios, and mode shapes. Then, a finite-element (FE) model was developed based on detailed structural design information, and its eigenvalues and eigenvectors were compared with the test results. The vibration test results showed various mode shapes, including in-plane deformation of the floor diaphragm composed of cross-laminated timber (CLT) panels. The damping ratios in all the modes were scattered between 1 and 3%, and no frequency dependency was observed. The modal properties of the FE model agreed well with the test results by considering the additional stiffness of non-structural components. In order to simulate the in-plane deformation of the CLT floor diaphragm, detailed modeling of the connection between each CLT floor panel and the connection between CLT floor panels and concrete cores is recommended. The findings provide practitioners with an insight into dynamic properties and FE modeling methods of tall timber–concrete hybrid buildings.

Experimental study on seismic behavior of RC column-steel beam joints with whole column-section diaphragm

RC column–steel beam (RCS) frame is one of the most popular hybrid structural systems. Multiple types of RCS joints have been proposed in the last few decades. To avoid undesirable bearing failure, complicated strengthening details were required in RCS joints, which caused difficulties in construction. This study proposed a whole column-section diaphragm type RCS joint with simple details. Compared to most RCS joints, the steel web was cut off at the beam-column interface in the proposed joint, which facilitated the arrangement of stirrups and concrete casting. Moreover, the bearing failure could be avoided since the bearing area of concrete was enlarged and the local bearing stress decreased, requiring no additional strengthening details. To investigate the seismic performance of the proposed RCS joint and the impacts of strengthening configurations, four interior joint specimens were designed, fabricated, and tested under cyclic loading. In addition, joint strengths were calculated using the existing methods. The test results showed that joint shear failure occurred in all specimens. The concrete within the hole in the diaphragm has limited influence on joint behavior. The force in flanges could be fully transferred to concrete through the dowel action of longitudinal reinforcements and friction between the diaphragm and concrete. The ductility of joints was significantly improved due to the confinement provided by face bearing plates (FBPs). The orthogonal FBPs could greatly increase the shear resistance of the joint. The predictions for joint shear strengths following the current calculation methods were significantly conservative. It confirmed that adequate shear capacity could be obtained although the simplified details were used. The conclusions of this research can provide a reference for the engineering application of the RCS hybrid frame.

Structural Performance of Demountable Hybrid Floor Systems Under Monotonic and Cyclic Loading

AbstractThe building sector is actively researching and reviewing technical solutions for de‐construction, driven by the increasing importance of sustainability requirements, as outlined in the EU Commission's ‘Green Deal,‘ which aims to achieve net‐zero greenhouse gas emissions by 2050. Two key research areas in efficient structural design strategies are the performance of hybrid structures, which combine mechanical properties and architectural appearance of different materials, and the techniques and mechanical properties of connections between structural components that enable deconstruction and reuse. However, there is a scarcity of studies and methods focused on demountable and hybrid structural systems, limiting the understanding of their overall structural performance at a real‐structure floor level. In this paper, a finite element model is presented to conduct a comparative study between the traditional floor system with welded stud connections and the demountable floor system with coupler‐embedded bolted connectors. The numerical results showed that the serviceability loading capacity of the demountable floor system was 8% lower, and the difference in ultimate resistance was further enlarged. Reusing a demountable floor system, analysed in the case study, had little effect on the ultimate resistance, but it is difficult to exclude local plastic deformation after the first life cycles.

A Partial Multiplicative Dimensional Reduction-Based Reliability Estimation Method for Probabilistic and Non-Probabilistic Hybrid Structural Systems

A new reliability estimation method based on partial multiplicative dimensional reduction is proposed for probabilistic and non-probabilistic hybrid structural systems. The proposed method is characterized by decorrelating interval input variables from random input variables using the partial multiplicative dimensional reduction method in conjunction with the weakest-link theory. In this method, the failure statistics of the original performance function are equivalent to a statical chain of two elements, in which one of the two elements represents the failures due to random input variables and the other represents the failures due to interval variables. Rather than yielding an estimated interval of failure probability, the proposed method produces a single value for failure probability, which is more meaningful for engineering. In addition, the accuracy, validity, and superiority of the proposed method are demonstrated, and the error-related properties of the proposed method are investigated.

Experimental Study of the Seismic Performance of CJS Hybrid Structural Systems Connected to the CFT Column

Experimental Study of the Seismic Performance of CJS Hybrid Structural Systems Connected to the CFT Column

The Use of Interactive Virtual BIM to Boost Virtual Tourism in Heritage Sites, Historic Jeddah

Today, moving from a two-dimensional environment to a more advanced interactive three-dimensional (3D) environment in the industries of architecture, engineering, and construction has become one of the most significant topics of interest. This is due to several primary advantages that the 3D environment can offer. Building information modeling (BIM) can be used as a highly advanced system to present a desired reality in a 3D interactive environment accompanied with 3D reality captured data, such as the point cloud data. As such, these 3D environments can be employed for more advanced uses, such as virtual reality and augmented reality technologies (VR and AR). Recently, BIM has been employed in the context of heritage (known as HBIM, or Heritage Building Information Modeling) for different purposes, such as to provide as-built information with the ability to interact with the end user and uploading information (e.g., historical photographs, documents about materials, or any past restoration projects) into the BIM model. This research will focus on providing an interactive rich virtual 3D model for heritage management. This virtual environment can be employed in cultural tourism and used for the abovementioned purposes. The research project has been adopted in the case of the Zainal Historical House (Bayt Zainal) located in the Historic District of Jeddah, Saudi Arabia. This house is described as one of the significant historical buildings in the historic district. The key aim for selecting this case study is to bridge the gap in architectural knowledge regarding these heritage buildings and their hybrid structural systems (i.e., integration of steel or concrete with the traditional “Mangbi” stone technique).

The Role of Site Conditions on the Structural Damage in the City of Valdivia during the 22 May 1960 Mw 9.5 Megathrust Chile Earthquake

Abstract The 22 May 1960 Mw 9.5 Valdivia megathrust earthquake, with a rupture length close to 1000 km in the central–south Chile, is the largest recorded earthquake in the modern times. The city of Valdivia is located about 300 km south of the northern boundary of the rupture in front of one of the largest asperities of the earthquake. In this article, we analyze the geology of the city and results from geophysical exploration methods that could explain the observed pattern of structural earthquake-induced damage. Surface waves methods results indicate that the soils in Valdivia have shear-wave velocity in the upper 30 m VS30 ranging from 150 to 300 m/s, whereas horizontal-to-vertical spectral ratios (HVSRs) calculated from ambient seismic noise show predominant vibration periods between 0.6 and 1.4 s. The housing stock in Valdivia at the time of the earthquake mainly consisted of one- and two-story wooden buildings, and fewer masonry and reinforced-concrete buildings. Our reinterpretation of the data indicates that despite the large seismic demand and the low shear-wave velocities, well-designed, well-constructed, and founded structures were barely damaged. Most of the structural damage concentrated in hybrid structural systems, poorly designed and constructed structures, and structures with deficient foundations build over uncontrolled backfills that experienced lateral movement and differential settlement. The predominant vibration periods from the HVSR do not correlate with the most damaged areas, but it seems to correlate with the depth of the soil deposit. The reduced damage of the larger structures in the city at the time of the earthquake may be partially explained because their vibration periods did not resonate with the predominant vibration period of the soil, in addition to their large structural redundancy.

Seismic Evaluation of Mixed Steel and RC Columns in Hybrid High-Rise Buildings

AbstractThe growth in high-rise building construction has increased the need for hybrid reinforced concrete and steel structural systems. Columns in buildings are the most important elements because of their seismic resistance. Reinforced concrete (RC) columns and steel columns were used herein to form hybrid structural systems combining their distinct advantages. Eleven 3D building models subjected to earthquake excitation with reinforced concrete beams and slabs of 12 floors in height and with different distributions of mixed columns were analyzed by the SAP2000 software in order to investigate the most suitable distributions of a combination of reinforced concrete and steel columns. Top displacements and accelerations, base normal forces, base shear forces, and base bending moments were computed to evaluate the selected hybrid structural systems. The findings are helpful in evaluating the efficiency of the examined hybrid high-rise buildings in resisting earthquakes.

Mechanical properties of novel out-of-plane steel beam–concrete wall pinned joints with T-shaped steel connectors under monotonic tension load

Nowadays, reinforced concrete core wall–steel frame hybrid structural systems are widely used in high-rise buildings. In this type of structural system, the steel beam–concrete wall (SBCW) joints bear significant cyclic tensile and compressive loads under earthquake motions. Considering that most of the compressive loads are transferred to the slabs rather than the joint core, the pulling resistant capacity of the joints plays a very important role in the seismic behaviour of the entire structure when neglecting the tensile strength contribution of concrete slabs. In this study, the pullout behaviour of a new form of SBCW pinned joints with T-shaped steel connectors was tested, and the load–displacement curves, failure modes, as well as stress and strain development of the specimens were analyzed. Two failure modes were observed in the experiments: one is the breakout failure mode characterized by the pullout of the concrete pyramid with lower strength and stiffness, and the other is the web yield failure mode characterized by the yielding of the web plate of the T-shaped steel connector with higher strength and stiffness. The failure mode that was experienced mainly depended on the embedded depth of the T-shaped steel connector. Then, an analytical model for predicting the pulling resistant capacity of the joint was proposed. In this model, the calculation method corresponding to the breakout failure mode, which is based on the principle of virtual work, can assess the respective contributions of concrete, shear studs and stirrups to the pulling resistance capacity of the joint, and the calculation method corresponding to the web yield failure mode is simplified by calculating the yield strength of the web plate of the T-shaped steel connector. Finally, the proposed model was verified by experimental results.

In-Plane Stiffness of Hybrid Steel–Cross-Laminated Timber Floor Diaphragms

AbstractThe use of hybrid structural systems formed by combining wood with other materials provides engineers with a wide range of solutions to satisfy code requirements for mid- and possibly high-...

Structural Performance Assessment of Through-Column-Type Beam-to-Column Joints

Reinforced Concrete-Steel (RCS) moment frames consisting of reinforced concrete columns and steel beams are one of several types of hybrid structural systems which are considered as high-performing and cost-effective alternatives to traditional reinforced concrete or steel frames. A primary challenge in the design of RCS frames is the proper detailing of the connection between the steel beam and the reinforced concrete column components. Hence, much of the research has focused on the design and behavior of the composite beam-to-column joints, which are classified into through-beam-type and through-column-type categories. This study focuses on the structural performance assessment of the through-column-type joints with different detailings through experimental investigations and numerical simulation. In this research, three distinct damage patterns have been identified for the through-column-type joints and the effectiveness of proper detailing on the strength, stiffness, and toughness performance enhancement of such connections is demonstrated through experimental investigations. Moreover, the capability of the OpenSees program in simulating the structural response of the RCS frames with through-column-type joints is shown and the degrading effect of the load-cycles repetition on the connection load capacity is investigated and verified.

Failure-mode importance measures in structural system with multiple failure modes and its estimation using copula

In the structural reliability analysis, there exist multiple failure modes. Influence of each failure mode on the structural system reliability needs to be considered, because it is significant for simplifying the system model and improving the performance of the system. By using the concepts of the importance measures(IM) in probability risk assessment (PRA), the importance indices in PRA are extended to measure the failure mode contribution to the structural system reliability, and the analytical solutions of the failure mode importance measure for the parallel and series structural systems are derived firstly. Then, copula method is proposed to estimate the importance indices for the nested hybrid structural systems. At last, one numerical example with a parallel structure and two engineering examples are employed to analyze the failure mode importance and to test the two estimates based on the analytical solution and the copula method. Result indicates that five PRA importance indices can well reflect the failure mode importance. It also shows that the copula method is highly suitable for computing PRA IMs in the intricate structural systems.

Effect of soil in controlling the seismic response of three-dimensional PBPD high-rise concrete structures

In the last decades, valuable results have been reported regarding conventional passive, active, semi-active, and hybrid structural control systems on two-dimensional and a few three-dimensional shear buildings. In this research, using a three-dimensional finite element model of high-rise concrete structures, designed by performance based plastic design method, it was attempted to construct a relatively close to reality model of concrete structures equipped with Tuned Mass Damper (TMD) by considering the effect of soil-structure interaction (SSI), torsion effect, hysteresis behavior and cracking effect of concrete. In contrast to previous studies which have focused mainly on linearly designed structures, in this study, using performance-based plastic design (PBPD) design approach, nonlinear behavior of the structures was considered from the beginning of the design stage. Inelastic time history analysis on a detailed model of twenty-story concrete structure was performed under a far-field ground motion record set. The seismic responses of the structure by considering SSI effect are studied by eight main objective functions that are related to the performance of the structure, containing: lateral displacement, acceleration, inter-story drift, plastic energy dissipation, shear force, number of plastic hinges, local plastic energy and rotation of plastic hinges. The tuning problem of TMD based on tuned mass spectra is set by considering five of the eight previously described functions. Results reveal that the structural damage distribution range is retracted and inter-story drift distribution in height of the structure is more uniform. It is strongly suggested to consider the effect of SSI in structural design and analysis.

Seismic performance assessment of steel frame infilled with prefabricated wood shear walls

Steel-timber hybrid structural systems offer a modern solution for building multi-story structures with more environmentally-friendly features. This paper presents a comprehensive seismic performance assessment for a kind of multi-story steel-timber hybrid structure. In such a hybrid structure, steel moment resisting frames are infilled with prefabricated light wood frame shear walls to serve as the lateral load resisting system (LLRS). In this paper, drift-based performance objectives under various seismic hazard levels were proposed based on experimental observations. Then, a numerical model of the hybrid structure considering damage accumulation and stiffness degradation was developed and verified by experimental results, and nonlinear time-history analyses were conducted to establish a database of seismic responses. The numerical results further serve as a technical basis for estimating the structure's fundamental period and evaluating post-yielding behavior and failure probabilities of the hybrid structure under various seismic hazard levels. A load sharing parameter was defined to describe the wall-frame lateral force distribution, and a formula was proposed and calibrated by the time-history analytical results to estimate the load sharing parameter. Moreover, earthquake-induced non-structural damage and residual deformation were also evaluated, showing that if designed properly, desirable seismic performance with acceptable repair effort can be obtained for the proposed steel-timber hybrid structural system.

The Glass Fibre-Reinforced Polymer–Steel Hybrid Footbridge of Saint Mateus Park, Portugal: From Conceptual Design to In Situ Assessment

In the last two decades, the construction of pedestrian and road bridges using glass fibre reinforced polymers (GFRP) combined with traditional materials has notably increased. The potential of such hybrid structural systems stems from their ability to best exploit the mechanical properties of each constituent material. Pultruded multicellular deck panels have proved to offer innovation and competitiveness to the most recent hybrid panel-to-girder systems. The high strength-to-density ratio of the decks’ cross-sections, the low maintenance costs, the corrosion resistance together with the reduced installation times are particularly advantageous for footbridge applications. It was in this context that a GFRP-steel hybrid design was proposed for the construction of a pedestrian access to the St. Mateus Park in the city centre of Viseu, in Portugal. This recently opened footbridge is a 13.3 m span and 2.5 m wide simply supported low-rise arch, comprising HEB steel profiles and a pultruded GFRP slab composed by 75 mm thick multicellular deck panels with full interaction between elements (studs fastened and epoxy adhesivelybonded). The footbridge design was developed with support of full-scale tests on deck panels and using current analytical and numerical tools, which have proven to be sufficiently accurate for this particular structural system. The lightness/slenderness and harmonious landscape integration over the St. Mateus Market contributed to the wide acceptance of the hybrid footbridge by both the Municipal Authorities and the population in general.

Experimental and numerical investigations into seismic performance of timber-steel hybrid structure with supplemental dampers

Although building structures can be designed to meet the life safety criterion and to deform inelastically without inducing collapse under major earthquakes, the structural and nonstructural damage associated with inelastic responses is normally very costly to repair. In this paper, friction dampers are utilized to upgrade the seismic performance of timber-steel hybrid structure, which has been proposed asan alternative structural solution for multi-story buildings. The hybrid structural system consists of steel moment resisting frame and infill light wood frame shear wall, both of which serve as the main lateral load resisting components, and friction dampers are introduced as frame-to-wall connectors to mitigate earthquake-induced damage. Pseudo-static loading tests were carried out on three timber-steel hybrid lateral load resisting subassemblies, and test results showed that the friction dampers were very effective in dissipating earthquake input energy, and correspondingly, much less damage was observed within the main structural members. The software package OpenSees was used to simulate the hysteretic behavior of the hybrid structure, and the developed finite element model was further validated by test results. Moreover, an optimal damper design solution was provided for a four-story timber-steel hybrid prototype building according to the numerical results from massive time-history analyses. Finally, the floor acceleration and inter-story drift responses of the prototype building with optimal damper configurations were assessed. This research aims to contribute to the development of novel timber hybrid structural systems with enhanced seismic performance.

Ductility Estimation for a Novel Timber–Steel Hybrid System

AbstractIn current force-based seismic design procedures, structures are allowed to behave inelastically during significant seismic events. For this reason, the applied design base shear of a structure is calculated by reducing the elastic strength demand by a ductility factor that represents the ability of a structure or structural system to deform inelastically beyond yielding. Whereas North American building codes provide ductility factors for traditional structural systems, including timber-based or steel-based systems, there are currently no design provisions available for novel hybrid structural systems. Thus research is required to define the force reduction factors, and specifically the ductility factor, Rd, to safely and efficiently design novel systems within the existing seismic design provisions. One such novel system is the so-called finding the forest through the trees (FFTT), proposed in 2012, where mass-timber panels act as shear walls and are connected to each other and to perimeter frame...