Bending Moment Research Articles

On the importance of mooring cable dynamics in response analysis of submerged floating tunnel using quasi-static and fully coupled dynamic models

Submerged floating tunnels are considered an economical alternative to those conventional bridges in crossing deep and long-span water bodies. The development of accurate modeling methods and simulation tools is the primary requirement for the safe design of submerged floating tunnels. Mooring cables are the primary source of stability of submerged floating tunnels against hydrodynamic loadings, and are commonly modelled using the computationally efficient quasi-static catenary approach. The dynamics of mooring cables can be of significant importance in dynamic responses of the submerged floating tunnel. Therefore, in this study, a discrete catenary element is presented with the aim of its implementation in the fully coupled dynamic analysis of submerged floating tunnels. To study the effect of mooring cable dynamics, the prototype of Qiandao Lake submerged floating tunnel has been used in a comparative study between quasi-static and fully coupled dynamic models. The numerical examples show differences in displacements and cable tensions due to the mooring cable dynamics. Furthermore, the mooring cables dynamics have significant effect on the tunnel shear forces and bending moments. The quasi-static coupled modeling significantly underestimates the tunnel internal forces.

Elastic-plastic flexural behavior of hybrid steel girder bridge considering welded residual stress

Hybrid steel girders use a section type that fully utilizes the strength performance of steels, which are widely used in steel plate girder bridges with multiple spans. In this paper, the distribution of the welded residual stress in hybrid I-shaped steel girders was investigated by the hole drilling test, and the unified model was analyzed and revised. Considering welded residual stress, the elastic and plastic design method for calculating the flexural capacity of hybrid I-shaped steel girders was put forward. Experiments and numerical simulations were conducted to analyze the elastic-plastic flexural behavior of the hybrid I-shaped steel girders using multi-scale models. The influence of welded residual stress, geometry of section, steel grade, and initial geometrical imperfections on the elastic-plastic flexural capacity of hybrid I-shaped steel girders were discussed through the parameter analysis adopting the dimensions commonly used in bridges. Analysis results show that the welded residual stress reduces the value of the elastic and plastic bending moments by almost 25% to 40% and 3%, respectively. The geometry of the section should be paid attention to clarify the value of the flexural capacity of the hybrid I-shaped steel girder. The width-to-thickness ratio limit of the flange should be adjusted according to the severity of initial geometrical imperfections.

CROSS Safety Report: Accidental partial demolition of a beam

This month we present a report about a permanent works design engineer who noticed that hydro-demolition of the end of a floor supporting beam had taken place out of sequence. This introduced a pattern of bending moments and shear forces that were not considered in the original design.

Axial compressive stability design of longitudinal asymmetrical shuttle-shaped columns

Longitudinal asymmetrical shuttle-shaped column (LA-SSC) has found its wide application when subjected to combined axial compression and horizontal point load in practical engineering. This paper focuses on elastic and elasto-plastic buckling behaviors of the LA-SSC only under axial compression and the resulting outcome could provide an indispensable basis for further establishing buckling strength prediction of LA-SSC under axial compression and horizontal point load. At first, the elastic buckling behavior of tapered columns (TC) and longitudinal symmetrical shuttle-shaped columns (LS-SSC) are derived in theory and verified by finite element numerical results, and corresponding elastic buckling modes are discussed. Subsequently the elastic buckling load prediction of LA-SSCs is established first and the corresponding normalized slender ratio, as a key design parameter, is generalized. Finally, the stability capacity of LA-SSCs is involved in theoretical analysis and finite element (FE) numerical calculation under axial pressure. Through investigating the axial load-lateral displacement curves and axial stress distributions the buckled LA-SSCs, the effects of different parameters (such as overall length, plate thickness, and steel strength) on the axial compression stability capacity of LS-SSCs are explored. As a result, the complete design formulas for axial compression stability capacity of LA-SSCs are presented first and compared with current major design codes in various countries. It is observed that the proposed strength design formulas are in good correspondence with the FE numerical results. The proposed formulas could provide references and guidance for the axial compression buckling strength of LA-SSCs under axial compression and they further supply fundamentals for establishing the strength design recommendation of LA-SSCs under axial compression and bending moments.

Effects of train speed on dynamic performance of shoe-rail interaction system

The increase of the running speed of electric train has a certain influence on the dynamic performance of coupling of conductor rail and collector shoe. In this paper, the mechanical characteristics of coupling vibration between shoe and rail for high-speed trains are studied by using a numerical simulation method, and the effects of train speed on the vibration law of shoe-rail interaction system are analyzed. The results show that both the maximum displacement of the rail and the maximum contact force between the shoe and the rail increase with the increase of the train speed. The bending moment of the rail, the maximum displacement of the shoe, the elastic and viscous forces of the shoe all decrease first and then increase. In particular, when the train speed increases from 275 to 300 km/h, the displacement, bending moment, contact force, and other mechanical quantities increase significantly, which indicate that it will lead to a sharp increase in vibration degree when the train speed exceeds 275 km/h. Therefore, in the case of actual operating parameters in this paper, it is recommended that the train speed does not exceed 275 km/h.

Fluidic undulation effects on carangiform swimmers propelled by internal active bending moments

With different shapes and material properties, fish all achieve undulatory swimming gait under the action of internal active muscle stimulation and external fluid forces. Such locomotion can be decomposed into deformation affected by internal and external forces in the body frame and overall translation and rotation solely determined by fluid forces. In order to revisit the undulatory swimming gait, we investigate the hydrodynamic performance of two-dimensional flexible carangiform swimmers with varying stiffnesses and thicknesses, which are driven by the active internal bending moments, and employ the complex orthogonal decomposition and Fourier decomposition methods to quantitatively measure and analyze the proportion of undulation. It is found that standing wave deformation characteristics are prominently observed along fish-like bodies with high stiffness, whereas traveling wave characteristics are more evident in bodies with lower stiffness. The self-propelled fish body demonstrates lateral oscillation and rotation around its center of mass, namely, the heaving and pitching movement, particularly in specimens with high stiffness. The present analysis shows that the heaving and pitching locomotion induced by the fluid significantly increase the traveling wave proportion by modulating the amplitude and phase of the left and right traveling waves viewed in forward frame. We called it fluidic undulation effects (FUE), which is different from the undulation of body deformation. This effect is more pronounced for large stiffnesses and thin airfoils. The standing wave deformation observed with a large stiffness transforms into a traveling wave propulsion pattern, with its traveling wave index even slightly surpassing that of a small-stiffness pattern. Although the efficiency of the standing wave deformation is low, it facilitates a faster forward speed (body lengths per stroke). The positive impact of the FUE on the swimming performance is also confirmed by restricting the recoil motions of the lateral translation and rotation of the body. Furthermore, we observe that there is no undulatory swimming gait that has both the highest energy efficiency and the highest speed.

Posterior atlantoaxial fixation of osteoporotic odontoid fracture: biomechanical analysis of the Magerl versus harms techniques in a cadaver model

BACKGROUND CONTEXTOdontoid fractures are among the most common cervical spine fractures in the elderly and are associated with increased morbidity and mortality. Clinical evidence suggests improved survival and quality of life after operative intervention compared to nonoperative treatment. PURPOSEThis study seeks to examine the stability of an osteoporotic Type II odontoid fracture following posterior atlantoaxial fixation with either the Magerl transarticular fixation technique or the Harms C1 lateral mass screws C2 pedicle screw rod fixation. STUDY DESIGNBiomechanical cadaveric study. METHODSEighteen cadaveric specimens extending from the cephalus to C7 were used in this study. Reflective marker arrays were attached to C1 and C2 and a single marker on the dens to measure movement of each during loading with C2–C3 and occiput-C1 being allowed to move freely. A biomechanical testing protocol imparted moments in flexion-extension, axial rotation, and lateral bending while a motion capture system recorded the motions of C1, C2, and the dens. The spines were instrumented with either the Harms fixation (n=9) or Magerl fixation (n=9) techniques, and a simulated Type II odontoid fracture was created. Motions of each instrumented spine were recorded for all moments, and then again after the instrumentation was removed to model the injured, non-instrumented state. RESULTSBoth Harms and Magerl posterior C1–C2 fixation allowed for C1, C2, and the dens to move as a relative unit. Without fixation the dens motion was coupled with C1. No significant differences were found in X, Y, Z translation motion of the dens, C1 or C2 during neutral zone motions between the Magerl and Harms fixation techniques. There were no significant differences found in Euler angle motion between the two techniques in either flexion-extension, axial rotation, or lateral bending motion. CONCLUSIONSOur findings suggest that both Harms and Magerl fixation can significantly reduce dens motion in Type II odontoid fractures in an osteoporotic cadaveric bone model. CLINICAL SIGNIFICANCEBoth Harms and Magerl posterior atlantoaxial fixation techniques allowed for C1, C2, and the dens to move as a relative unit following odontoid fracture, establishing more anatomic stability to the upper cervical spine.

Aeroelastic Scaling of a High-Aspect-Ratio Wing Incorporating a Semi-Aeroelastic Hinge

There has been a growing interest in utilizing flared folding wingtips as an in-flight load alleviation device to enable increased wing spans that meet airport gate limits but with little increase in wing weight. The semi-aeroelastic hinge (SAH) concept is implemented in high-aspect-ratio wings to enable wingtips to be released during severe load cases such as maneuvers and gusts to alleviate the bending moments while maintaining optimum aerodynamic shape for the rest of the flight. In this paper, scaling methods for wings incorporating the SAH are explored, allowing for the development of equivalent scaled unmanned aerial vehicles or wind tunnel models with similar aeroelastic behavior as full-size aircraft. Three scaling approaches are considered in this study, namely, Iso-Froude, Iso-Frequency, and Iso-Strain, where a set of governing nondimensional quantities and scaling factors are determined. Despite the significant nonlinearities resulting from large wingtip fold angles, it is shown that a linear scaling approach can be appropriate for such a wing configuration. Furthermore, the aeroelastic properties of each scaled model are compared to those of the full-scale model, where the best match was obtained from the Iso-Strain model, although it is challenging to meet the required operational conditions.

Experimental study on edge cell partially-replaced joint for I-beam to multi-celled CFST walls under cyclic loading

The multi-celled concreted-filled steel tubular walls (MCCFSTWs) are widely used in practice, especially in apartment constructions. The use of thin steel tubes in MCCFSTWs makes it weak at the joint zone, therefore the connections between the MCCFSTWs and steel beams become an important issue for the application of MCCFSTWs. A novel joint for the connection between the MCCFSTWs and I-beams is proposed in this study. The main feature of the proposed joint is that the edge cell of the MCCFSTW is partially replaced using a welded C-section, where two partial internal diaphragms are set to transfer the bending moment from the I-beam. With this treatment, the edge cell of MCCFSTWs near the joint zone can be significantly strengthened to satisfy the requirements of the seismic design, while the compactness of concrete at the joint zone can be guaranteed by using the partial internal diaphragms. The design philosophy of the proposed joint is first introduced in this study. Three specimens are then designed and tested under the cyclic lateral loading. Subsequently, the behaviors of the proposed joints are discussed based on the test results, including the failure mode, the hysteresis curve, the ductility, the ultimate load and the initial stiffness. The stress states at the joint zone obtained from tests are also analyzed and compared with those using simplified analytical model. According to Eurocode 3, all tested specimens can be classified as rigid and full-strength joints. Moreover, the rotation capacity of this novel joint meets the requirements of GB50011. The investigation of this paper is believed to be meaningful for the application of the novel joints in the practice.

Influence of wind gusts on aeroelastic loads of NREL 5MW wind turbine

This study employs blade-resolved computational fluid dynamics simulations to investigate the aero-elastic loads on a yawed NREL 5MW wind turbine subject to full and partial wind gusts. A novel spatial gust representation, tailored towards application to large eddy simulations, is introduced. This methodology permits the injection of gusts with customizable spatial dimensions inside the flow domain. Simulations are conducted with gusts having the same diameter as the turbine rotor, half rotor diameter, and asymmetric impact with respect to the center of rotation of the turbine. Simulations of the turbine under yawed conditions are also considered. The flow characteristics are reported using contours and iso-surfaces of velocity magnitude and Q-criteria. Insights into the load characteristics of the turbine are described using torque, thrust, and root bending moments. This research highlights that partial gust impact contributes to noteworthy load fluctuations and blade tip deformations, stemming from the imbalance in force distribution across the rotor plane.

An experimental study of the thrust and power produced by a 1/20th scale tidal turbine utilising blade winglets

Winglets have been employed in the aviation industry to reduce vortices generated at aircraft wings, decreasing drag, and hence increasing fuel economy. For rotating applications previous experimental and numerical studies addressed the application for wind turbines and suggested winglets facing backwards on the suction side of a blade could increase the power capture. This paper presents experimental work using a scale 3-bladed horizontal axis tidal turbine. An oil-based paint flow visualisation coupled to blade thrust and torque measurements helped to identify the mechanism behind the phenomenon affecting the performance of winglets facing the suction side of a turbine blade. The results show that on average a winglet facing downstream decreases the power coefficient 1–2% and increases the thrust coefficient up to 6% for tip speed ratios 5.0–7.0. On the other hand, a symmetrically mirrored winglet facing upstream increased the power coefficient by 1–2%, and the thrust coefficient by 3–4%. Further, increased bending moments at the root of the blade were estimated to be in the range 4.5–6.0%. Winglets have the potential to provide a meaningful increase to power capture at minimal additional capital cost without increasing rotor diameters. Further work to optimize pressure‐side winglets should be conducted.

Damage and fracture investigation of self-compacting concrete in the filling layer of CRTS-III using three-point bending tests

Literature about filling layer self-compacting concrete (FLSCC) has indicated that FLSCC plays a crucial role in its application to Chinese railway track system III (CRTS-III). It is apparent that the damage characteristics of FLSCC have not been clearly investigated, as the actual working conditions are not considered enough. There exists a remaining gap about the mechanical properties and fracture behaviors of FLSCC under bending loads. In order to fill this gap, in this study, three-point bending (TPB) tests on the FLSCC beams with precast notches were performed based on the real bending situation of FLSCC in CRTS-III. Acoustic emission (AE), strain gauges and a digital camera were utilized to monitor the fresh evolutionary laws of micro- and macro- cracks as well as the corresponding damage morphology. The study presents that the monitored load-crack mouth opening displacement (P-CMPD) curves, load-strain (P-ε) curves and AE activity curves all exhibited similar distributions, including four stages with increasing bending loads. In term of the AE activities, the first apparent crack in the interior and warning point of failure can be detected by analyzing the captured AE activities of the FLSCC beams. In addition, the dominant failure mode of the specimens was determined as tensile cracks according to the rising angle-average frequency (RA-AF) criterion for potential FLSCC application in terms of the limiting ratios. This failure mode indicates that under pure bending loads, the mid-span section is subjected to the maximum bending moment, and the specimen experiences tensile damage. Therefore, for future practical application, the structural health state of FLSCC in CRTS-III could be nondestructively real-time monitored by the AE technique. Meanwhile, the calculated fracture parameters of the FLSCC specimen can reflect the cracks stability of the specimen. This study can also present experimental and theoretical references for further studies on FLSCC in CRTS-Ⅲ under other types of loads.

Flexural behaviour of post-tensioned precast beams manufactured with basalt-fibre-reinforced recycled concrete–conventional concrete

To promote the sustainable development of the ecological environment, facilitate the recycling of recycled concrete and explore efficient approaches to enhance the performance of structural components, this study proposes a post-tensioned precast beam model manufactured with basalt-fiber-reinforced recycled concrete–conventional concrete. Flexural performance tests were conducted on 12 beams with different concrete strength grades (C40, C50, C60), basalt-fiber-reinforced recycled concrete layer thicknesses (200 mm, 250 mm, 300 mm), and basalt fiber volume fractions (0%, 0.1%, 0.2%). The results show that the incorporation of basalt fiber can effectively inhibit crack development, and improve the stiffness and flexural strength of components. Through theoretical analysis, the factors affecting the ultimate stress formula for high-strength prestressing steel strands are attributed to the comprehensive reinforcement index and prestressed reinforcement index, thereby obtaining a flexural strength formula. Coefficients describing the influences of basalt fiber and recycled coarse aggregate were introduced and combined with average crack spacing and width measurements to derive a post-tensioned precast beam model of average crack spacing and width. Based on the derived calculation model, the average deviation between the tested and calculated results of the ultimate bending moment is less than 6%, and the average deviation between the tested and calculated results of the average crack width is less than 9%. The proposed model has good prediction accuracy for evaluating the flexural strength and average crack width, which provides a theoretical basis for assessing the flexural performance of composite beams.

A novel stability analysis method of single-layer ribbed reticulated shells with roof plates

The steel dome of liquefied natural gas (LNG) storage tanks comprises a curved roof plate welded onto a single-layer ribbed reticulated shell (SLRR shell). However, the roof plate may cause diaphragm effects, which may resulting in instability of the steel dome at a relatively low load level. In this paper, an innovative equivalent single-layer ribbed reticulated shell (ESLRR shell) was proposed to investigate the impact of the diaphragm effect. Specifically, the roof plate and H-shaped radial beam were equated as radial irregular beams based on the principle of plate-shell composite action. Next, we performed a systematic analysis of the instability mechanisms in the ESLRR shell, revealing the interaction between the beam buckling and the overall structural instability. Finally, through parametric study, we explored the effects of roof plate thickness and rise-to-span ratio on the ESLRR shell, and obtained the optimal structural parameters. The results show that the proposed method effectively solves the challenges associated with the presence of roof plates in LNG storage tanks steel dome stability analysis; Under the combination of weak boundary stiffness and high bending moment, radial irregular beams are more prone to buckling; Increasing roof plate thickness or rise-to-span ratio can reinforce the stability of the ESLRR shell. Overall, this research work provides theoretical guidance for the future design and optimization of LNG storage tank domes.

Vibration control of a monopile offshore wind turbines under recorded seismic waves

The dynamics and vibration control of offshore wind turbines (OWTs) under wind, wave, and earthquake loads is an important but understudied topic, especially for fully coupled seismic analysis considering pile foundation flexibility of OWTs. In this work, we study the effect of multiple passive tuned mass dampers (MTMD) on a monopile OWT by using the fully coupled seismic analysis method. A combined shutdown procedures and MTMD vibration control strategy is proposed for the OWT. First, a state-of-the-art aeroelastic tool, FAST, is extended with a seismic load calculation module, and the numerically modeled monopile OWT addresses the effect of pile-soil interaction (PSI) by establishing ElasPile module in the updated FAST. Then, the focus is placed on the normal operation and emergency shutdown status of OWTs under the combined earthquakes, wind and wave conditions, and structural and motion responses are analyzed under various combination conditions through time-domain simulations, the dynamic characteristics of the OWT during realistic seismic events are shown. Sequentially, based on the proposed MTMD, the vibration migitation effects are evident for the operation OWT and the OWT with shutdown strategies during the combined loading conditions. The reduction in the extreme responses can be as high as 10.53% and 55.02% for the bending moment at the mudline in different OWT conditions, respectively. Therefore, the combined shutdown procedures and MTMD vibration control strategy of OWT is an effective vibration reduction method. Additionally, it is found that PSI has a significant impact on the dynamic characteristics and vibration control effects of OWT structures under wind, wave, and earthquake loads, and the coupled spring boundary condition on the basis of developed ElasPile module is recommended for seismic control analysis of OWT using the combined shutdown procedures and MTMD vibration control strategy.

Virtual sensing via Gaussian Process for bending moment response prediction of an offshore wind turbine using SCADA data

Offshore wind turbines (OWTs) can be equipped with two types of monitoring systems: (1) a Supervisory Control and Data Acquisition (SCADA) system that monitors operational data such as wind speed and power generation, and (2) vibration sensors like accelerometers and strain gauges to track structural dynamics. While strain gauges enable fatigue damage calculations, not all OWTs in a wind farm have these sensors installed. This paper proposes a Gaussian process regression (GPR) strategy to predict the bending moment time-histories of an OWT. The model takes into account various SCADA data such as wind speed, power, and nacelle acceleration as input and learns to predict the high and low-frequency dynamic response of the system. The strategy is implemented and tested to predict the bending moment response of a 6 MW offshore wind turbine in the fore-aft and side-side directions of the turbine. The accuracy and reliability of the proposed strategy are evaluated and demonstrated considering different operational conditions and multiple hotspot locations along the height of the turbine. The proposed strategy proves to be an efficient virtual sensing strategy and can be easily transferred to other turbines in the same wind farm without the need for widespread installation of strain gauges.

Structure Design and Strength Analysis of the Glass Reinforcement Plastic (GRP) Malay Traditional “Perahu Bedar”

The Perahu Bedar, a traditional fishing boat in the Terengganu region of Malaysia, has been historically crafted from Cengal wood. In response to challenges posed by wood scarcity and limitations in skilled craftsmen, this study pioneers the exploration of Glass Reinforced Plastic (GRP) as a novel alternative material for constructing the traditional Perahu Bedar, measuring 4.32 meters in length. Through a rigorous analysis, the research delves into the structural design intricacies and strength attributes of the GRP Perahu Bedar, marking a significant departure from conventional wood-based construction methods. The study conducts a comprehensive analysis of the structure design and strength characteristics of the GRP Perahu Bedar. The weight, buoyancy force, and load distribution along the boat are analyzed. The data shows varying weight and buoyancy forces along the stations, with positive load values indicating upward forces contributing to buoyancy and negative load values representing downward forces. This analysis provides insights into the boat’s stability and distribution of forces. The sheer force and bending moment along the Perahu Bedar are evaluated. The sheer force values gradually increase or decrease along the boat, while the bending moment is highest at the midsection and decreases towards the ends. These results indicate the distribution of forces and stress on the boat’s structure, aiding in understanding its integrity and stability. The Factor of Safety (FoS) analysis demonstrates a FoS value of 2.2368, indicating a safety margin greater than 1. This suggests that the GRP Perahu Bedar design meets safety requirements and can withstand applied 
 
 stresses without exceeding yield strength. The FoS value provides assurance of structural integrity and safety during normal operating conditions. In summary, this study underscores the groundbreaking potential of Glass Reinforced Plastic (GRP) as a viable alternative to traditional wooden Perahu Bedar due to very high cost of Cengal Wood (wood that been used to build Peahu Bedar). By meticulously analyzing critical factors such as weight, buoyancy, load, shear force, bending moment, and Factor of Safety (FoS), the research offers invaluable insights into the structural integrity and safety aspects of GRP Perahu Bedar. These revelations not only herald a new era of sustainable and cost-effective boatbuilding practices but also serve as a crucial step towards safeguarding and perpetuating the rich maritime heritage of the region.

Determination of Bending Moment Resistance of L-Type Doweled Joints Reinforced With Glass-Fiber-Reinforced Polymer Woven Fabrics (GFRPWF) and Basalt-Fiber-Reinforced Polymer Woven Fabrics (BFRPWF)

In this study investigated the bending moment resistance of L-type doweled joints reinforced with glass-fiber-reinforced polymer woven fabrics (GFRPWF) and basalt-fiber-reinforced polymer woven fabrics (BFRPWF). Dowels produced from Scots pine, oak, beech and chestnut wood were used in the doweled joints. While the GFRPWF and BFRPWF were fixed with epoxy adhesive, the dowels were fixed with polyvinyl acetate (PVAc-D3/D4) glue. Test were carried out to determine the bending moment resistance of doweled joints. Experimental results showed that joints connected with oak dowel has been the highest bending moment resistance, and the joints of Scots pine dowel has been the weakest bending moment resistance. The bending moment resistance of oak dowel was approximately 23%, 33%, and 61% higher than for joints constructed with beech, Chestnut and Scots pine, respectively. The bending moment resistance value reinforced with the BFRPWF (55.62 N.m), and the lowest was in unreinforced joints (32.06 N.m). The mean bending moment resistance of reinforced joints (GFRPWF, BFRPWF) was 31% and 74% higher than unreinforced samples (control), respectively. In general, it has been found that the bending moment resistance of doweled joints is influenced by wooden dowel species and FRP types.

A New Moment-Resisting Glulam Beam-End Connection Utilizing Mechanically Fastened Steel Rods—An Experimental Study

A new moment-resisting mass timber connection was designed based on the principles of force equilibrium in applied mechanics. The connection configuration utilizing two mechanically fastened threaded steel rods embedded into the end of a glulam beam section was experimentally investigated in this study. A gradually increasing transverse load was applied to the free end of a cantilevered beam, causing a bending moment on the beam-end connection until failure. Four different connection configurations were examined, each replicated twice to verify results. The beam connection parameters investigated were rod anchorage length (200 and 250 mm) and square washer size (38.1 and 50.8 mm). Test results show that increasing the washer size increased the connection bending strength by increments more significantly than those due to increasing the rod anchorage length. However, the connection configurations with the smaller-size washer, which failed mainly due to wood crushing under the washer, had higher ductility ratios than those with the larger-size washer, which failed due to steel rod yielding. In a real-life scenario, a structural element such as a glulam beam is usually loaded to approximately 50% to 70% of its design capacity, considering a reasonable margin of safety. The study estimates a maximum possible bending moment utilization factor for the strongest connection configuration that ranged between 34% and 48% compared to the maximum moment resistance of a supported glulam beam spanning an average length of 4.0 m to 6.0 m (a common span length in framed timber buildings) and has a cross-section size same as the one utilized in this study. This utilization factor is quite large for a timber connection, and thus, confirms a considerable moment-resisting capability of the new configuration developed in this study.

Experimental and Theoretical Investigations of the Mechanical Behavior of Column-Free Quasi-Rectangular Segmental Tunnel Linings

To investigate the mechanical behavior and design methodology of column-free QRST (quasi-rectangular segmental tunnel) structures, a theoretical analysis based on prototype experiments and simulation models is conducted. Initially, a prototype experimental investigation is conducted to reveal the structural behavior at the service stage. Subsequently, the ESHR model (Equivalent Stiffness Homogeneous Ring), the BS model (Beam Spring), and the MBS model (Modified Beam Spring) are used to simulate structural behavior. For design purposes, the design methodology is explored based on the ESHR model, followed by a sensitivity analysis of several key load parameters. Based on the experimental results, weak parts of the column-free QRST structure are found to include several joints (Joint 1, Joint 5, Joint 3, and Joint 8), and corresponding optimization measures are proposed. By comparing the test results, the above-mentioned three models demonstrate their applicability in structural simulation, with the ESHR model having sufficient design accuracy. A model-based deformation mechanism analysis found that joints contribute approximately 2/3 of the structural deformation. For the structural design of the column-free QRST using the ESHR model, amplifying the calculated results of structures directly subjected to the service stage by 10% suffices to meet engineering requirements. Based on the test and study, special attention should be paid to the negative bending moment regions at the waists of the structure during both the design and service stages.