Internal Forces Research Articles

Theoretical model of ultimate shear capacity and flexural capacity design method of boundary elements for reinforced concrete frames with steel plate shear walls

AbstractThe steel plate shear walls (SPSWs) have been proven effective in reinforced concrete frames (RCFs) as a lateral force‐resistant structure. Despite of advancements, accurately predicting the ultimate shear capacity of RCFs with SPSWs remains challenging using current simplified models. Additionally, the flexural capacity design procedure for the boundary elements (beams and columns) in previous studies of RCF‐SPSWs involved intricate iterative procedures, hindering its widespread implementation. To address the two issues, this paper investigates the pushover responses and the plate‐frame interaction (PFI) of an RCF‐SPSWs system using theoretical and numerical methods. There are three main contributions. First, a theoretical model of ultimate shear capacity for RCF‐SPSWs is proposed, which can also be used to predict shear contributions of boundary frames in RCF‐SPSWs. Calculation errors for ultimate shear capacity of RCF‐SPSWs and shear contribution from the boundary frame are only 3.7% and 6.7% respectively, which are reduced dramatically compared with the traditional model. A simplified schematic diagram for the global collapse mechanism (uniform distribution of plastic hinges within a structure) of RCF‐SPSWs is developed to facilitate the calculation of internal work and reaction forces. Secondly, a flexural capacity design method for the boundary elements to avoid in‐span plastic hinges is proposed. The proposed method enables the achievement of direct estimation of the flexural demands that could trigger a global collapse mechanism, all without intricate iterative procedures. The applicability of current assumptions for the design of steel boundary frame in RCF‐SPSWs system is discussed, and engineering suggestions are provided to ensure safer and more economic designs. Comparison results confirmed the applicability of the proposed design method, which can be adopted to achieve the global collapse mechanism for RCF‐SPSW system. Thirdly, impacts of yielding panel actions on the flexural capacity of boundary elements of RCF‐SPSWs are clarified. Comparison results demonstrated that adding SPSWs to an RCF alters the axial force on boundary elements and significantly impacts the flexural capacity. A design suggestion is made to emphasize the importance of avoiding the balanced failure of boundary elements. The proposed theoretical model can be used to economize the cross‐section of boundary elements in RCF‐SPSWs system under seismic loads due to accurate prediction of their shear contribution; the proposed flexural capacity design method can achieve a global collapse mechanism, and thus the structural safety and energy dissipation capacity are improved; moreover, the building design efficiency is also improved due to avoidance of intricate iterative procedures.

Analytical Solution for Longitudinal Seismic Responses of Circular Tunnel Crossing Fault Zone

ABSTRACTThis paper proposes a simplified analytical solution for longitudinal seismic responses of a circular tunnel crossing a fault zone under longitudinally propagating shear waves. The transmissions and reflections of shear waves at two geological interfaces between the fault zone and intact rock are considered when calculating the free‐field displacement. An improved elastic foundation beam model considering different tangential contact conditions at the tunnel‒rock interface is also adopted. According to the continuous conditions at the two geological interfaces, explicit expressions for the tunnel displacement, bending moment, and shearing force are given. The effectiveness of the proposed analytical solution is validated via numerical simulations, and the importance of accounting for tangential contact conditions at the tunnel‒rock interface is emphasized. Moreover, parametric studies are performed to investigate the effects of the fault zone width, rock conditions, tunnel lining stiffness, tangential contact conditions, and earthquake frequency on the deformation and internal forces of tunnels subjected to seismic waves. This novel analytical solution can be utilized to quickly estimate the longitudinal seismic responses of circular tunnels crossing fault zones subjected to longitudinally propagating shear waves, particularly in the preliminary engineering design, and can be extended to geological conditions with multiple interfaces.

Factors influencing cross-departmental collaborative performance: evidence from 452 water governance cases in Guangzhou, China

In addressing complex public issues, cross-departmental collaboration encounters challenges that require identification of factors critical to its effectiveness. This study collected data from 452 cases of water governance in Guangzhou using systematic sampling methods, and empirically examined three major perspectives on cross-departmental collaborative performance in them. Modeling results revealed a significant and positive correlation between leaders’ attention to water environmental governance and cross-departmental collaborative performance. Conversely, power fragmentation negatively impacted performance. Greater public participation in water environmental governance was significantly associated with improved cross-departmental performance. This study comprehensively assesses the collaborative performance by incorporating process-oriented and outcome-based dimensions for systematic examination of underexplored questions of horizontal cross-departmental collaboration, going beyond the scope of prior research, which has primarily centered on cross-regional collaboration. Moreover, it offers a refined analytical framework incorporating internal bureaucratic factors and external forces, with an emphasis on the role of public involvement as an independent factor for shaping collaboration. This study contributes to the theoretical understanding of cross-departmental collaborative performance in the Chinese context as a developing country that faces obstacles in decentralized and uncoordinated water governance structures.

Performance Analysis of Pile Group Installation in Saturated Clay

In offshore pile engineering, the installation of jacked piles generates compaction effects within soil, thus further affecting previously installed adjacent piles. This study proposes a three-dimensional numerical model for pile group installation, soil consolidation, and loading analysis. Subsequently, the effect of pile spacing and pile length-to-diameter ratio on the deformation, internal forces, and vertical bearing capacity of adjacent piles are investigated. The results indicate that with an increase in pile center distance, the peak lateral displacement of the adjacent piles decreases, whereas the peak vertical displacement increases. As the pile length-to-diameter ratio increases, the peak vertical and lateral displacements of the adjacent piles are enhanced. In addition, the peak axial force of the adjacent piles initially decreases and then increases with the penetration depth of the subsequent pile, whereas the peak bending moment initially increases and then decreases. The vertical bearing capacity of the subsequent pile is significantly superior to that of the adjacent piles. Therefore, the effects of pile installation on adjacent piles should be included in pile engineering. The impact of the subsequent pile installation on the bearing capacity of adjacent piles can be significantly reduced by increasing the pile center distance and pile length-to-diameter ratio. The findings provide useful guidance for pile group engineering.

Numerical study on seismic performance of a prefabricated subway station considering the influence of construction process

In previous seismic analyses of cast-in-place stations, the importance of the construction process was typically not emphasized. Unlike cast-in-place stations, prefabricated subway stations feature innovative construction methods. The effect of ignoring the complete construction process on the seismic performance of prefabricated subway stations remains unclear, and this study aims to address this issue. In this research, a three-dimensional nonlinear numerical model considering soil-structure interaction (SSI) was established. First, the complete construction process of the station, including excavation of the foundation pit and structural assembly, was replicated. The initial state before dynamic loading was clearly defined. Subsequently, the seismic response mechanisms of the station, including deformation, SSI, acceleration, and internal forces, were thoroughly investigated, revealing the impact of structural type and construction method on seismic performance. The results indicate that neglecting the complete construction process leads to differences in the initial state before dynamic loading, resulting in variations in seismic response. Specifically, ignoring the assembly process causes an average bending moment error of 59 % and an axial force error of 35 % for each component. By comprehensively analyzing these findings, a deeper understanding of the intricate interplay between assembly techniques, structural behavior, and construction processes in seismic contexts can be attained, thereby informing more robust engineering practices.

Analysis of concrete damage at anchorage end of the high-speed railway bridge sound barrier under the 400 km/h train-induced wind loads

The sound barrier installed on high-speed railway bridges withstands repeated train-induced wind load, which may lead to concrete damage at its anchorage end. This paper focuses on the assessment of concrete static damage at the sound barrier anchorage end under train-induced wind loads. The nonlinear finite element model of the sound barrier anchorage system is established to analyze the stress distribution, strain distribution and static damage of concrete structure at the anchorage end under 400 km/h train-induced wind loads in respect of different bolt preloads. The simulated results illustrate that both mortar and concrete near bolt holes suffer a certain degree of tensile and compressive damage. The maximum tensile and compressive damage factor values for mortar and concrete are 0.930, 0.643 and 0.892, 0.434 respectively. In addition, the effects of train-induced wind load on the internal force of the sound barrier anchorage take nearly no account, with a maximum of only 0.68 %. The results indicate that bolt preload is the most significant factor for concrete static damage, while the train-induced wind load appears negligible. An appropriate bolt preload can avoid the concrete static damage of the sound barrier anchorage end, and guarantee the structural stability of the sound barrier.

Nonlinear analysis of spatial trusses with different strain measures and compressible solid

This paper investigates the nonlinear behavior of spatial truss elements under finite deformations, focusing on the impact of various strain measures in compressible materials. We examine both Total Lagrangian (using engineering and Green–Lagrange strains) and Eulerian formulations (using natural, Biot, and Almansi strains). The analysis assumes a linear spatial hyperelastic material where Cauchy stress is proportional to axial natural strain via Young’s modulus. For infinitesimal strains, Young’s modulus remains consistent across different stress/strain pairs. In the finite strain regime, we derive a nonlinear secant modulus based on Young’s modulus. Internal force vectors and tangent stiffness matrices are computed using the direction cosines of the truss element in its deformed state. The paper demonstrates that for infinitesimal deformations, adjusting the modulus of elasticity when using different stress/strain pairs is unnecessary. However, for finite deformations, it is essential to adjust the modulus of elasticity. Numerical simulations validate the performance of the proposed 3D truss element against established formulations. This research offers critical insights into the nonlinear response of spatial trusses, guiding the selection of appropriate strain measures for enhanced accuracy in engineering applications. These findings contribute to more reliable and efficient structural designs, especially in scenarios involving finite deformations and compressible materials.

Investigation of an Ancient Wooden Cantilever Covered Bridge in China: Construction Form and Mechanical Properties

Wooden cantilever-covered bridges are typical Chinese constructions due to their structural style and architectural decoration. Yanzi bridge, an ancient wooden cantilever-covered bridge with more than 220 years of history in Anhua, China, has attracted increasing attention in recent years. In this study, its construction form and cultural background were investigated, and the structural components, original materials and mechanical behavior of the bridge were investigated in detail. First, the same type of raw material used for the Yanzi bridge, namely, pinus koraiensis, was tested to better understand its mechanical properties. Then, a finite element model was built to simulate the mechanical behavior of the bridge, and the stress state and internal forces of the cantilever system were obtained. According to the numerical results, when the loads are transferred downward and evened by the beams in the same layers of the cantilevers, the maximum deflection of the bridge of 12.8 mm meets the requirements of not exceeding L/600 in the specification, and the maximum normal stress of 1.35 MPa is much less than the ultimate tensile strength of the wood. This indicates that the structural safety performance of the ancient wooden cantilever-covered bridge is acceptable. Finally, a small amount of tiny damage of the bridge was observed and presented in the paper. This damage is not severe enough to cause brittle collapse, but care and maintenance are necessary to preserve this old historical bridge.

Does Sagittal Alignment Matter? A Biomechanical Look at Pinning Pediatric Supracondylar Humerus Fractures.

Closed manipulation and percutaneous pinning is standard of care for displaced supracondylar humerus fractures, yet the optimal pin configuration, particularly in the sagittal plane, is not well defined. This study evaluates how sagittal plane pin variations affect construct strength biomechanically. One hundred synthetic pediatric humerus models were used to emulate supracondylar humerus fracture. The models were pinned using 4 different configurations uniformly divergent in the coronal plane with variations in the sagittal plane: (1) 2 diverging pins with the lateral pin anterior (n = 25), (2) 2 diverging pins with the lateral pin posterior (n = 25), (3) 2 parallel pins (n = 25), and (4) 3 parallel pins (n = 25). The models were tested under bending (flexion, extension, and varus) and rotational (internal and external) forces, measuring stiffness and torque. Statistical analyses identified significant differences across configurations. The 2-pin parallel configuration (9.68N/mm in extension, 8.76N/mm in flexion, 0.14 N-m/deg in internal rotation, and 0.14 N-m/deg in external rotation) performed similarly to the 3-pin parallel setup (10.77N/mm in extension, 7.78N/mm in flexion, 0.16 N-m/deg in internal rotation, and 0.14 N-m/deg in external rotation), with no significant differences in stiffness. In contrast, both parallel configurations significantly outperformed the 2-pin anterior (5.22N/mm in extension, 5.7N/mm in flexion, 0.11 N-m/deg in internal rotation and 0.10 N-m/deg in external rotation) and posterior (9.86N/mm in extension, 8.31N/mm in flexion, 0.12N-m/deg in internal rotation, and 0.11 N-m/deg in external rotation) configurations in resisting deformation. No notable disparities were observed in varus loading among any configurations. This study illuminates the sagittal plane's role in construct stability. It suggests that, when utilizing 2-pins, parallel configurations in the sagittal plane improve biomechanical stability. In addition, it suggests avoiding the lateral anterior pin configuration due to its biomechanical inferiority. Further research should assess ultimate strength and compare various 3-pin configurations to better delineate differences between 2-pin and 3-pin configurations regarding sagittal plane alignment. Level III-biomechanical study.

Seismic behavior and design of concrete-filled steel tubular frame-RC core tube structures

In the design of frame-core tube structures, the method for adjusting the frame bearing capacity and stiffness to ensure the structure as a dual system is a critical issue. This study investigates the effects of frame shear distribution ratio, frame bearing capacity, and column pattern on the seismic performance of concrete-filled steel tubular frame to reinforced concrete core tube structures (CFRCTs). Time-history and seismic fragility analyses on eight representative models are performed and the distribution pattern of inter-story drift ratios, structural damage modes, and collapse safety margins are compared. The study results show that CFRCTs possess superior seismic performance (with a collapse margin ratio > 9.3) compared to the structures with reinforced concrete columns and the collapse margin ratio continuously increases from 9.3 to 11.2 with increasing frame stiffness. Enhancing the frame bearing capacity mitigates the frame damage, while improving slightly on structure’s collapse resistance (< 0.1 %). Without adjusting the frame for the second fortification line, damage to the column is not serious and the frame can still effectively withstand the increased shear force transmitted from the core tube during an extremely severe earthquake. The frame experiences more shear force and damage as the frame shear distribution ratio increases; while the core tube damage is effectively alleviated. Due to the redistribution of internal forces, the distribution pattern of inter-story drift ratios under the collapse state is markedly distinct from that under the elastic stage and severe earthquakes. Based on the analysis, design suggestions considering both collapse resistance and economic efficiency are proposed for CFRCTs.

Full-scale loading test for shield tunnel segments: Load-bearing performance and failure patterns of lining structures

To explore the load-bearing performance and the failure patterns of the lining structures, a full-scale loading test on the three-ring staggered assembled shield tunnel segments is carried out through a hydraulic loading system. In the experimental study, the segments’ internal force, convergence deformation, and displacement, and the bolts’ internal force, are analyzed. According to the experimental results, the relationship between internal force and deformation is obtained to determine the residual bearing capacity of the shield tunnel at each stage. Three stages are specified for the evolution of the segment’s maximum bending moment during the loading process, in which, the elastic stage is the main and longest stage, in which the bending moment of the segment increases the most. There are two stages for convergence deformation development and segment misalignment development. At the end of loading, the segment’s maximum positive and negative convergence values reach 61.22 and −57.69 mm, respectively. Besides, the maximum segment misalignment is 3.67 mm, which occurs in the direction of 90°. The segment cracks when its maximum convergence value reaches 25.03 mm. Moreover, there are signs of fracturing on the waist joint of the segment when its maximum convergence value reaches 32.73 mm. The concrete at the waist joint starts fracturing in pieces when the segment’s maximum convergence value reaches 38.93 mm, which is defined as the type of shear failure. Finally, the bearing capacity of shield tunnels during segment failure period can be evaluated by using the corresponding relationship between deformation and internal force.

Study on the coupling mechanism and reinforcement effect of a shield tunnel reinforced by channel steel under side pit excavation

To investigate the internal force and deformation response law and reinforcement effect of a shield tunnel reinforced by channel steel in a pit excavation, a self-developed “hydraulic loading system” is used to conduct a full-size test and numerical simulation analysis on a three-ring staggered-seam assembled tube sheet. The results show that the internal force response of the tube sheet on the excavation side of the pit is complex and sensitive, the internal force is transformed in the direction under different load levels, and the bearing capacity can be effectively increased by 62.5 % through the channel steel reinforcement; the channel steel fails due to weld cracking, and the nonstructural bonding surface is damaged by sliding; and the maximum reinforcing efficiency of the combination of the channel steel and steel plate reaches 45.8 %, making it an economical and reliable reinforcing program.

Plane straight element with semi-rigid connections: formulation from an energetic approach

Discrete connectors, such as screws, nails, and others, are commonly used to fasten various structural elements. The established hypothesis regarding the behavior of joints conceived with discrete connectors directly impacts the distribution of forces. For example, in the design of truss structures, the resisting moments that arise due to the arrangement of the connectors are often disregarded, as considering the semi-rigid behavior of the joints introduces greater complexities in the modeling required to determine displacements and internal forces. This work presents the stiffness matrix of a plane straight element with semi-rigid connections and its support reactions for three loading cases from the application of the Principle of Virtual Work (PVW). Semi-rigid connections are represented by translational and rotational linear elastic springs at both ends of the element, giving it six degrees of freedom. One example shows the application of this formulation using the Classical Displacement Method and the results are also obtained numerically via the Finite Element Method (FEM)This work presents the stiffness matrix of a plane straight element with semi-rigid connections and its support reactions for three loading cases from the application of the Principle of Virtual Work (PVW). Semi-rigid connections are represented by translational and rotational linear elastic springs at both ends of the element, giving it six degrees of freedom. One example shows the application of this formulation using the Classical Displacement Method and the results are also obtained numerically via the Finite Element Method (FEM).

β-barrel proteins dictate the effect of core oligosaccharide composition on outer membrane mechanics.

The outer membrane is the defining cellular structure of Gram-negative bacteria, a group that contains many important pathogens like Escherichia coli , Vibrio cholerae , and Pseudomonas aeruginosa . One role of the outer membrane is to block the uptake of small molecules like antibiotics. However, it is becoming increasingly clear that it also functions as a structural exoskeleton that is critical for the cell's ability to cope with internal and external mechanical forces. Here, we carefully dissect the molecular basis for the load-bearing capacity of the outer membrane by screening a set of mutants with a new cell biophysics assay.

Factors Affecting the Development of Handicrafts Products at Donkeo Village, Luang Prabang City

The purpose of this research were to study the overall situation of producers in Donkeo village, and analyze factors affecting the handicraft products development of Donkeo village, Luang Prabang City. Quantitative methods were used, 40 questionnaires were delivered to the weavers, and descriptive statistics and inferential statistics were used as analyses. The results showed that environmental factors overall using SWOT analysis were at a high level ( = 3.81). The five forces analysis showed overall was at a high level ( = 3.80). The degree of factors affecting the level of handicraft product development overall was high level ( = 4.00). The PEST analysis showed that overall was at a high level ( = 3.86). The factors affecting the level of handicraft product development overall were high level ( = 3.78). Environmental factors were affected by the results of the handicraft product development of Donkeo village in Luang Prabang City consisting of opportunity X3 (b=0.209). The competitiveness forces factors were affected by the results of the handicraft product development of Donkeo village in Luang Prabang City consisting of the threat of substitution (b=0.259), and competitive rivalry (b=0.259). Internal forces factors affected the results of the handicraft product development of Donkeo village in Luang Prabang city consisting of characteristics (b=0.204), and the external factors affected the results of the handicraft product development of Donkeo village in Luang Prabang city consists of economic (b=0.329).

Design of a Six-Story Teaching Building: A Comprehensive Approach to Safety and Structural Efficiency

This paper describes teaching building design. The project, designed for the teaching building, prioritizes safety in its main structure, a reinforced concrete frame with six floors above ground. The story heights are 4.2m, 3.9m, 3.9m, 3.9m, 3.9m and 3.9m, respectively, and the building's total height is 27.6m. The construction site category is classified as type II, and the first group's seismic fortification intensity is 7 degrees. The process includes architectural design, structural design, and PKPM checking calculation. Architectural design mainly consists of a general description. The plan, elevation, section, and draft of the corresponding building are drawn according to the relevant information and requirements provided by the design task book. Structural design mainly includes load statistics, calculation of internal force and displacement of the frame, a combination of internal force, and calculation of staircase, slab roof, floor slab and frame structure. The calculation of displacement, internal force, and reinforcement of the whole frame structure is carried. Out using PKPM. In the course of architectural design, safety is a paramount consideration, in line with the principles of safety, applicability, beauty, economy, and energy-saving requirements, referring to national standards and relevant materials, and strictly following the requirements of relevant architectural design standards, the design of each link is not only a comprehensive scientific consideration of its own but also a related discussion with teachers, as detailed in the construction plan. The frame structure is adopted,in this structural type. It mainly includes structure layout and calculation sketch determination, load calculation, internal force calculation, internal force combination, main beam section design, and reinforcement calculation, frame column section design and reinforcement calculation, secondary beam section design and reinforcement calculation, floor and roof design, staircase design etc. Among them, the D-value method is used to calculate the internal force of the structure under horizontal load, and the distribution method is used to calculate the internal force of the structure under vertical load (dead load and live load).

Study of the influence of spatial effects on the ground surface and buildings in a two-lane tunnel boring

There are a series of engineering risks, such as ground subsidence, building tilt and cracking, in the process of shield tunnel driving through buildings, which have many adverse effects on urban residents and engineers. In particular, the differences in the effects of the interaction of two-lane tunnels on the building structure and ground deformation field are less often considered under different spatial effects such as construction sequences and tunnel spacings. As well as the problem of analyzing the building as a whole out of reality. To solve these problems, the spatial effect of the shield tunnel underpassing the shallow foundation building is simulated by Plaxis3D software to study the sensitivity analysis of surface settlement and the internal forces and deformation law of the building above in the process of tunneling underpassing with different depths of burial H and horizontal distance D of the double line tunnel. The engineering impact zoning method can investigate the safety of tunnels and buildings under different spatial effects when tunnels pass through buildings. The splitting of the building into plates and columns can reveal the forces and deformation laws of different structural parts. The results show that during the construction process of the double-line tunnel, the tunnel constructed first has a “blocking effect” on the tunnel constructed later, which affects the distribution of the disturbance area to a certain extent and changes the curve shape of the settlement trough. When the “blocking effect” occurs, the surface settlement and building deformation will be significantly reduced. In the internal forces of the building, the plate structure is mainly subjected to changes in axial forces, while the column structure is mainly affected by shear forces and bending moments. The factor of safety of tunnels decreases as the tunnel spacing decreases and as the building loads above increase.

Examination of the complementary energy principle in modified couple stress theory and its application for analysis of size effects in the internal force field of functionally graded microbeams

The precise quantification of the internal force field in MEMS piezoresistive sensor micro structure is crucial for ensuring accurate signal output. This paper proposes and proves the complementary energy principle associated with modified couple stress theory (MCST) based on the linear elasticity assumption. And this principle is used to discuss and analyze whether there is a size effect in the internal force field of functionally graded (FG) micro beams for the MEMS piezoresistive sensor. The results show that the size effects exist in the internal forces and the stationary point coordinate x of the total moment for the micro beam. The size effects are related to the dimensionless material scale parameter l/h, the supported spring stiffness, the temperature and the support rotational movements. Intuitive explanations of the size effects are given for the internal force fields and its stationary point coordinates. Behaviors of the solutions agree with the published data when the MCST degenerates into the classical theory (CT).

A Cognitive Model of Language Teacher Fossilization

Expertise in foreign language teaching has been widely discussed in the literature as inherently related to accumulated classroom experience and, hence, extensive practical knowledge. Even though current conceptualizations are increasingly focusing on teachers’ ability to reflect on their performance and continuously develop a repertoire of didactic resources regardless of their career stage, effective human information processing in the profession remains under-researched. This paper sees the concept of expertise from the perspective of cognitive processes, and specifically operations involved in problem-solving. The author presents a theoretical model of teacher fossilization, discussing attention, knowledge, reasoning, and judgment as potential inhibitors of intellectual vitality and growth in individuals. When neglected, these factors might lead experienced teachers to make just as incompetent decisions as novice educators. The model highlights the external and internal forces that cause practitioners to minimize, rather than maximize, their learning opportunities in a workplace. The new concept has implications for teachers’ day-to-day practice as well as for in-service professional development initiatives. It serves as a guiding principle for the successful utilization of one’s cognitive capital and outlines both the purpose and direction of one’s mental effort.

Compatibility and conflict between environmentalist and occupational identities in Northern California’s forests

ABSTRACT This study examines the relationship between occupational identity and attitudes toward environmentalism, using interviews with 55 workers in northern California, including loggers, governmental employees, and members of environmental organizations. The results suggest that attitudes toward environmentalism are shaped by and reflective of the ways participants identify with their work, which is itself a product of both internal (community) and external (stigma) forces. In particular, this relationship appears in the types of environmental knowledge possessed and preferred by participants, debates about active versus passive management, and long-lasting historical narratives form the timber wars. Ultimately, workers are fairly flexible in their attitudes toward the landscape, and they are willing even to shift their own occupational identity over time, as new forest issues emerge. However, they are often more rigid when it comes to perspectives of others, and this poses some challenges for the future of collaboration in western forest management.