Search Results (14)

To improve the post-earthquake resilience evaluation of concrete buildings with various construction types, this study presents a generalized recovery-based framework that ext-ends the FEMA P-58 methodology. The proposed method introduces a dynamic repair scheduling approach that incorporates two key construction-related parameters: the prefabrication ratio and the types of prefabricated components. These inputs govern the allocation of parallel or sequential repairs, enabling a more accurate estimation of recovery trajectories and downtime. Functional loss over time is modeled through component-level repair sequencing combined with mobilization delays. A case study involving three four-story prestressed concrete frame buildings (cast-in situ, partially prefabricated, and fully precast prestressed concrete (PCaPC) with mortise–tenon (MT) connections) demonstrated the framework’s applicability. The results show that higher prefabrication levels lead to significantly shorter median repair times, with up to a 97-day reduction observed for the fully prefabricated frame. Additionally, recovery differences emerge even between buildings with the same prefabrication ratio but different component configurations. Compared to conventional assessment methods, the proposed framework avoids the overestimation of mobilization and repair duration, offering a practical tool for the design and performance assessment of resilient precast and hybrid concrete building systems. Full article

Bamboo is a green, renewable material with high strength and low cost, but raw bamboo has limited application in residential buildings due to its irregular shape and dry cracking. In this regard, this work proposed a novel ecological sandwich panel to explore the potential combination of engineered bamboo and raw bamboo culms. Face sheets made of glued laminated bamboo panels were bonded to the bamboo culm core via epoxy resin and mortise–tenon joints. Two groups of specimens with height-to-thickness ratios of 4.63 and 5.37 were tested through edgewise compression to investigate the failure modes, strength and rigidity. The results revealed that the specimens had no overall stability problem under axial loading, but exhibited delamination and local bulging to the face sheets. When the height-to-thickness ratio increased from 4.63 to 5.37, but still belonged to the short member range, the area of the adhesive interface increased by 16.13%, and the edgewise compressive strength and rigidity increased by 17.57% and 35.04%, respectively. This indicated that the capacity and rigidity were mainly determined by the connection strength, which was obviously affected by the manufacturing and assembly errors. Accordingly, increasing the connection strength could be helpful for improving the load-carrying capacity and ductility of such panels. Full article

In view of the application status and technical challenges of steel–wood composite joints in architecture, this paper proposes an innovative connection technology to solve issues such as susceptibility to pry-out at beam–column joints and low load-bearing capacity and to provide various reinforcement methods in order to meet the different structural requirements and economic benefits. By designing and manufacturing four groups of beam–column joint specimens with different reinforcement methods, including no reinforcement, structural adhesive and angle steel reinforcement, 4 mm thick steel sleeve reinforcement, and 6 mm thick steel sleeve reinforcement, monotonic loading tests and finite element simulations were carried out, respectively. This research found that unreinforced specimens and structural adhesive angle steel-reinforced joints exhibited obvious mortise and tenon compression deformation and, moreover, tenon pulling phenomena at load values of approximately 2 kN and 2.6 kN, respectively. However, the joint reinforced by a steel sleeve showed a significant improvement in the tenon pulling phenomenon and demonstrated excellent initial stiffness characteristics. The failure mode of the steel sleeve-reinforced joints is primarily characterized by the propagation of cracks at the edges of the steel plate and the tearing of the wood, but the overall structure remains intact. The initial rotational stiffness of the joints reinforced with angle steel and self-tapping screws, the joints reinforced with 4 mm thick steel sleeves, and the joints reinforced with 6 mm thick steel sleeves are 3.96, 6.99, and 13.62 times that of the pure wooden joints, while the ultimate bending moments are 1.97, 7.11, and 7.39 times, respectively. Using finite element software to simulate four groups of joints to observe their stress changes, the areas with high stress in the joints without sleeve reinforcement are mainly located at the upper and lower ends of the tenon, where the compressive stress at the upper edge of the tenon and the tensile stress at the lower flange are both distributed along the grain direction of the beam. The stress on the column sleeve of the joints reinforced with steel sleeves and bolts is relatively low, while the areas with high strain in the beam sleeve are mainly concentrated on the side with the welded stiffeners and its surroundings; the strain around the bolt holes is also quite noticeable. Full article

In situ dynamic testing is conducted to study the dynamic characteristics of the wooden structure of the North House main hall. The velocity response signals on the measurement points are obtained and analyzed using the self-interaction spectral method and stochastic subspace method, yielding natural frequencies, mode shapes, and damping ratios. This study reveals that the natural frequencies and damping ratios are highly consistent between the two methods. Therefore, to eliminate errors, the average of the results from both modal identification methods is taken as the final measured modal parameters of the structure. The natural frequencies of the first and second order in the X direction were 2.097 Hz and 3.845 Hz and in the Y direction were 3.955 Hz and 5.701 Hz. The modal frequency in the Y direction of the structure exceeds that in the X direction. Concurrently, a three-dimensional finite element model was established using ANSYS 2021R1, considering the semi-rigid properties of mortise–tenon connections, and validated based on in situ dynamic testing. The sensitivity analysis indicates adjustments to parameters such as beam–column elastic modulus, tenon–mortise joint stiffness, and roof mass for finite element model refinement. Modal parameter calculations from the corrected finite element model closely approximate the measured modal results, with maximum errors of 9.41% for the first two frequencies, both within 10% of the measured resonant frequencies. The adjusted finite element model closely matches the experimental results, serving as a benchmark model for the wooden structure of North House main hall. The validation confirms the rationality of the benchmark finite element model, providing valuable insights into ancient timber structures along transportation routes. Full article

To satisfy the easy-construction demands of precast concrete (PCa) frames after an earthquake, a PCa frame with mortise–tenon (MT) connections is proposed in this paper. MT connections are secured solely through the binding force of unbonded prestressed tendons without grouting for easy construction. The design and construction of the joint are detailed. During an earthquake, the hinge system of the connection allows for slight rotational movements. Finite element analysis was employed to assess the joint’s hysteresis behavior, revealing a three-stage earthquake response mechanism: closing, hinge relocation, and self-centering. Based on the hysteresis performance of the beam and column in the precast prestressed concrete (PCaPC) frame, a seismic response model for PCaPC buildings was established. Full article

This paper proposed a novel demountable fabricated joint in frame, which is connected by the prestressed and mortise–tenon connection. The prefabricated components of the demountable structures are designed to be reused, and the joint presented in this paper will promote the sustainable application of prefabricated components in future. The damage process and damage pattern of the internal joints under the horizontal load were analyzed using the refined numerical analysis model based on ABAQUS 6.14. Parametric analyses were conducted simultaneously for five parameters: axial compression ratio, the area and effective initial stress of unbonded prestressed strands (UPSs), the local reinforcement ratio in the core zone of the demountable joint, and the friction coefficient between the interface of concrete. The results showed that the demountable joint exhibits excellent energy dissipation potential under horizontal loads, but the damage was concentrated in the core zone. The deformation of the joint mainly consisted of the self-deformation of the prefabricated components, including bending, bearing and shear, as well as the relative slip deformation between the prefabricated components. The axial compression ratio has a more significant effect on the hysteresis performance compared to the areas of the UPSs and the reinforcement ratio. The initial effective stress of the UPS and the friction coefficient have relatively minor influence on the hysteretic performance of the joint. Finally, this paper recommends the design parameter values (axial compression ratio should not exceed 0.4, area of unbonded prestressed reinforcement should be not lower than As_n=0.₀₂ and not higher than As_n=0.₁, the initial stress of the UPS takes the value of 0.75f_pu) and outlines optimization measures. Full article

The mortise-and-tenon joint prefabricated connection combines the assembly form of mortise-and-tenon joints and cast-in-place wet joints. It achieves reliable joint connections through small joint depths and lap-spliced reinforcement lengths. To study the impact resistance and damage characteristics of the assembled pier, a nonlinear finite element analysis was performed on the assembled and monolithic pier model piers to study the effects of mortise-and-tenon joint depths, lap reinforcement, and grout on the response of the piers to vehicle impact. The results showed that, after impact, the damage to the prefabricated pier was similar to that of the monolithic one. The failure mode involved opening of the seam at the impact face-pier bottom junction and localized concrete compression at the back-impact face pier bottom, and damage accumulated from the column base towards the column centerline. The mortise-and-tenon joint provided substantial horizontal constraint for the pier, imparting excellent resistance to lateral stiffness. Consequently, both piers showed nearly identical peak impact forces, yet the prefabricated pier exhibited a lesser degree of bending deformation compared to the monolithic one. The depth of the mortise-and-tenon joints was a critical factor affecting the impact response of the prefabricated bridge pier. When the depth reached 0.4D or more, it ensured good impact resistance and joint connection, enhancing energy absorption capability and reducing pier damage. The length of lap-spliced reinforcement significantly affected the overall integrity of prefabricated component connections. Lap lengths of 10d or more greatly reduced the probability of failure in the connection between pier columns and cap beams, lowering damage to the pier columns, joints, and pier cap beams, thus ensuring good impact resistance. The diameter of the lap-spliced reinforcement and the elastic modulus of the grouting material affected the local stiffness near the joints. Increasing the diameter of the lap-spliced reinforcement appropriately prevented excessive local damage, while altering the elastic modulus had minimal impact on improving pier damage. Full article

This paper introduces a novel type of connection that integrates unbonded prestressed strands (UPS) and mortise-tenon in an assembly frame structure (UPS-MTF). First, the damage process and failure modes of the joints under reciprocating horizontal loads were systematically analyzed using refined numerical models. The recommended values of the design parameters of the joints were derived from the parametric analysis results. Refined numerical modeling results reveal the diagonal compression strut mechanism within the core region of the joint. The diagonal compression struts model assists in establishing the theoretical calculation formula for the skeleton curve of shear stress–strain in the core region. Second, a genetic algorithm (GA) parameter was identified for the restoring force model of the core region to determine the parameters of the hysteresis rules. Finally, a macro-simplified analytical model of the joint was created based on the restoring force model of the core region, and parameter analysis was conducted to verify the applicability of this macro-simplified analytical model. The research results prove that the damaged form of the joint proposed in this paper originates from the shear and relative slip damage between the components in the core region. The axial compression ratio significantly affects the hysteretic performance of the joints, and the upper and lower limit values were identified for the axial compression ratio of the joints. The area and initial effective stress of the UPS exert a minimal effect on the hysteretic performance of the joint. Based on the method proposed in this paper for determining the restoring force model in the core region of the joints, the hysteresis curves obtained from the macro-simplified analytical model closely match the refined numerical analysis model results. This correspondence verifies the applicability of the macro-simplified analytical model. Full article

The construction industry has been a significant contributor to global carbon emissions. Fortunately, it is well known that precast concrete structures possess the benefit of reducing carbon emission, of which the beam–column joint plays a crucial role in resisting severe loads. Nowadays, the cast-in-place joint is mostly adopted for beam–column joint The authors declare no conflict of interests of precast concrete structures, and the building industrialization degree is insufficient. In light of this, a novel precast concrete beam–column joint using the mortise–tenon (MT) connection is proposed inspired by traditional timber structures, and the contrastive analysis of mechanical behaviors of this joint and the same-sized cast-in-place joint is conducted by the finite element method. The results indicate that the proposed MT joint has a better mechanical behavior by comparing with the corresponding cast-in-place joint as the beam–column joint. Meanwhile, the MT connection mode has the characteristics of standardized construction, in line with the concept of sustainable development, which can greatly save the construction period. This research demonstrates the feasibility of MT joints in traditional timber structures as beam–column joints in precast concrete structures, and the application of MT joints may be promoted if the size and shape of that are further optimized. Furthermore, this in turn helps research and innovation of precast building construction technology and promotes the sustainable development of the construction industry in the direction of energy conservation and environmental protection. Full article

This article summarizes the current construction methods of prefabricated utility tunnels. (1) The proposed cast-in-place utility tunnel project was used as a background for this study. (2) The original cast-in-place structure was divided into components, and the connection methods of prefabricated composite slabs and mortise and tenon joints were used to propose a new type of prefabricated concrete utility tunnel construction method. After completing the design of the new prefabricated utility tunnel, a numerical simulation analysis of the actual stress situation of the utility tunnel was carried out using ABAQUS finite element software to verify the overall structural performance of the assembled utility tunnel. In addition, after completing the construction of the full-size model of the dual chamber, static load tests were carried out. (3) The test used the method of monotonic static bidirectional loading with a central hydraulic jack and tensioned steel strands, analyzed the cracks, deformation curves, and stress-strain of steel bars and concrete of the overall structure of the utility tunnel, and (4) verified the feasibility of the new assembled integral utility tunnel. Full article

The penetrated mortise–tenon joint (PMT) connecting column and beam in traditional timber structures often has neighbouring gaps between connected structural members due to initial manufacture errors and damage accumulated over years. Influences of the neighbouring gaps on the mechanical properties of the PMT joint have been analysed based on a full-scale experimental study. Four typical gap values are determined according to the probability analysis of on-site survey results of a Chinese traditional timber structure. Four full-scale models of PMT joints with varied gap values have been established. Failure modes and deformation characteristics have been studied by quasi-static tests. Results show that the failure modes are the tearing of wood fiber along the grain at variable cross-sections. The loose penetrated mortise–tenon (LPMT) joints all have high deformability. The slip distance of tenon grows as the gap value increases. Limit angles of the loose joints lag with the increasing degree of loosening. The bending bearing capacity and rotational stiffness of LPMT joints decrease as the gap value increases, and the limitation value of the gap is analysed. The resisting capacities of LJ-2, LJ-3 and LJ-4 are much lower than that of LJ-1. The changing ratios are 18.5%, 55.4% and 70.4%, respectively. A three-parameter power function model of the mortise–tenon joint with consideration of the neighboring gap is presented. Research results provide important references on the condition assessments of the existing traditional timber structures. Full article

Additive manufacturing (AM) is used in many fields and is a method used to replace wood components or wood-jointed furniture components in the furniture industry. Replacing wood joints by 3D printed connectors would be an advantage, considering the fact that during the process of assembling furniture, the execution technology of the joints is difficult, time-consuming, and labor-intensive. Advanced technology of AM applied in furniture manufacturing helps the designers to create new concepts of product design, with no limits of shape, number of joints, color, or size. The diversity of 3D printers and AM technologies provides the selection of materials in relation with the applicability of the 3D printed object. In this respect, the objective of the present research is to design a 3D printed connector to be used for jointing three chair components, namely the leg and two stretchers made from larch (Larix decidua Mill.) wood, and to use reinforced polylactic acid (PLA) fiberglass (20 wt. %) filament for 3D printing this connector using AM with fused filament fabrication (FFF) technology. The design of the connector, the possibility of using this type of material, and the deposition method of filament were investigated in this research. For this purpose, several evaluation methods were applied: microscopic investigation with 50×, 100×, and 200× magnifications, both of the filament and of the 3D printed connector; mechanical testing of corner joint formed with the help of connector between chair leg and the two stretchers; and a microscopic investigation of the connectors’ defects that occurred after applying the compression and tensile loads on the diagonal direction of the L-type joint. The microscopic investigation of the composite filament revealed the agglomerations of glass fibers into the core matrix and areas where the distribution of the reinforcements was poor. The heterogeneous structure of the filament and the defects highlighted in the 3D printed connectors by the microscopic investigation contributed to the mechanical behavior of L-type connecting joints. The bending moments resulting from compression and tensile tests of the 3D printed connectors were compared to the results recorded after testing, under the same conditions, the normal mortise–tenon joint used to assemble the abovementioned chair components. The larch wood strength influenced the mechanical results and the conclusions of the microscopic investigations, as well as the analysis of the broken connectors after testing recommended the change of connector design and filament deposition direction. Full article

In this paper, the mechanical performance improvement of traditional penetration mortise–tenon (PMT) connections reinforced by self-tapping screws (STSs) were experimental and numerical studied. Four unreinforced penetration mortise–tenon connections and four STS-reinforced connections were experimentally investigated under monotonic and low-frequency cyclic loading. Besides, the numerical model of PMT connections reinforced by STSs with different diameters and yield strength were established and analyzed.Their failure modes, rotational stiffness, moment-resisting capacity, ductility, and seismic behavior were studied. The experimental results indicated that the STSs reinforcements could enhance the moment-resisting capacity of the penetration mortise–tenon connection. Compared with unreinforced connections, the initial stiffness of STS-reinforced connections increased by 75% with the moment-resisting capacity increasing by 69%, respectively. Furthermore, the STSs reinforcement method can effectively restrict the pull-out of tenon during the whole loading process. Numerical simulation results showed that the yield strength of STS has little effect on the moment-bearing behavior of the connection. The diameter of STS significantly influences the connection performance, and the diameter of 8 mm is suggested. Full article

This paper presents the results of an experimental study into single-lap joints. One part of the joint was made as a 3D printed polymer and had cylindrical tenons, while the other part was made of an aluminium flat bar having mortises whose diameter and distribution corresponded to the polymer tenons. In addition to the mechanical joint, a layer of double-sided VHB (Very High Bond) adhesive tape was also placed in the lap, thus creating a hybrid joint. In total, 80 specimens were made, which were divided into four groups: A—specimens with one tenon of different diameters, B—specimens with different number of tenons of the same diameter, C—specimens characterised by multi-stage operation and R—reference specimens, connected only by double-sided adhesive tape. The joints were subjected to uniaxial tensile tests. The force–displacement characteristics obtained and the energy required, up to the point of the failure of the joints, have been analysed in this paper. The four and six-stage joints designed can significantly increase the safety of the structures in which they will be used. Full article