Space Frame Research Articles

Dynamic performance of a 5-story full-scale prestressed precast space frame structure under edge and corner column failure scenarios

Progressive collapse resistance is more critical for precast concrete than cast-in-place structures. Most existing studies utilized scaled-down and quasi-static pushdown tests on substructures with rigid constraints under key member failure scenarios. However, the connection details, the spatial action of floors and the constraint stiffness of the remaining structure significantly affect the structure's progressive collapse resistance. Full-scale structural testing is the most direct method to evaluate the progressive collapse resistance of a new prefabricated structure, although it is difficult and costly to load and measure. A 2 × 2 bay 5-story full-scale frame structure was constructed according to the minimum requirements of the Code for Seismic Design of Buildings to investigate the progressive collapse resistance of a new precast, prestressed, efficiently fabricated frame (PPEFF) system. The structure's dynamic performance was analyzed by removing the 4th-floor edge column and bottom corner column. The slider and double micro-friction surface configuration proved suitable for the rapid removal of large axial force columns in a full-scale progressive collapse experiment. The layout of the full-scale structural test and the structure's dynamic responses are described. The effect of the lateral constraint stiffness and the duration of column removal on the dynamic response of the test structure were analyzed using finite element analysis. The progressive collapse resistance mechanism of the PPEFF structure was discussed. The PPEFF system remained in an elastic state and exhibited good progressive collapse resistance.

RESULTS OF THE TECHNICAL INSPECTION OF A MULTI-STORY RESIDENTIAL BUILDING DAMAGED AS A RESULT OF A ROCKET IMPACT

The article presents the results of the examination of the technical condition of part of the construction structures of the building damaged as a result of a missile strike, the determination of the characteristics and classification of their defects and damage, the provision of conclusions and recommendations regarding the correction of the life cycle and further safe and reliable operation of the building. As part of the study, the object of the survey was a monolithic 22-story residential building with a basement (ATP) floor and a complex configuration in plan. The structural scheme of the complex is a monolithic reinforced concrete frame with stiffening cores. The stability and rigidity of the frame is ensured by diaphragms of stiffness in the form of reinforced concrete walls, elevator-stair nodes and rigid nodes connecting pylons and horizontal disks of monolithic reinforced concrete floor slabs. During the examination, visual and instrumental methods of research were performed. Before the field work, measures were taken to collect design and archival information about the research object. Instrumental studies to determine the actual concrete strength of reinforced concrete frame elements and to determine the diameter, protective layer and pitch of the working rods of the reinforcing frames of the load-bearing elements were carried out by non-destructive methods. The calculation model of the spatial scheme of the structure of the frame of the residential building, taking into account the damage, was made in the subsystem (PS) "COMPOSITION" of the software complex (PC) "MONOMAH CAD". The result of the survey is conclusions and recommendations, which indicate the specifics of damage and types of defects, destruction and debris in various structural elements that were discovered during the survey. The general technical condition of the residential building is classified as emergency. As for the recommendations, two options for carrying out repair and restoration works were provided. The first option is to restore the plan-elevation position of the building, the design marks of vertical and horizontal structures and the unloading of overloaded structures, to be performed with the help of an automatic hydraulic complex. The second option is the arrangement of temporary strengthening of emergency structures with the help of a metal space frame, without restoring the planned height position of the residential building.

An Integrated Framework of Critical Metaphor Analysis and Multi-level View with an Application to Metaphors for the Vietnam War

Since Conceptual Metaphor Theory (CMT) (Lakoff & Johnson, 1980) was introduced, methods of studying conceptual metaphor have kept improving to respond to methodological criticisms. Critical Metaphor Analysis (CMA) proposed by Charteris-Black (2004) has been considered as a “thought-provoking contribution” to metaphor analysis (Deignan, 2005) when approaching metaphor from various perspectives: critical discourse analysis, corpus analysis, pragmatics and cognitive linguistics. CMA is originally applied to one conceptual level in metaphor – domain. However, this paper argues that CMA can be exploited at four conceptual levels in Multi-level View of conceptual metaphor (Kövecses, 2017b) - image schema, domain, frame, and mental space. The combined framework of Critical Metaphor Analysis – CMA (Charteris-Black, 2004) and Multi-level View of conceptual metaphor – MLV (Kövecses, 2017b) can gain deeper insights into ideologies motivating metaphorical concepts for the Vietnam war as well as elucidate the conceptual structure of metaphor via the four levels. Hence, this combination fills the gap of lacking a framework with optimal balance of semantic, pragmatic, cognitive and critical dimensions. It also features the intriguing relationship between ideologies and conceptual structure, i.e., ideologies are embedded in all the four conceptual levels and systematically develop with increasing specificity from image schema to domain, frame and mental space. The focus of this paper is on our argument for an integrated framework of conceptual metaphor and the newspaper articles written by American war correspondents during the Vietnam war are used for illustration of how the integrated framework can help us better understand the conceptual metaphors in the articles.

Improved PBPD method for dual steel system considering the global effect of space frames

Performance-based plastic design (PBPD) method has been proposed to design single bay planar frames for twenty years. For a dual steel system, such as an eccentrically braced frame (EBF) structure, there will be both EBF bays and moment resisting frame (MRF) bays. So, the global effect between different frame bays cannot be considered when designing the global structure using the traditional PBPD method. In this paper, a ten-story high-strength steel composite K-shaped eccentrically braced frame (HSS-K-EBF) structure was firstly used for performance design and analysis based on a single bay EBF. The results show that the global structural model obtained by direct performance design of the single bay model cannot achieve the desired performance objectives. To this end, an improved PBPD method for the dual steel system was proposed considering the global effects of space frames. The elastic and elastic–plastic shear distribution relations were calculated for different bays of the frames including EBFs and MRFs. The performance objectives of the global structure were designed and evaluated more accurately by considering the over-strength contribution of shear links and the plastic development rate index ξ of energy dissipation members. The improved PBPD method was used to design the ten-story global HSS-K-EBF structure. The results of nonlinear dynamic time history analysis show that the improved PBPD method can ensure that the plastic damage distribution of energy dissipation members of different bays is more uniform and the plastic damage degree is more consistent with expectations.

Chronotopes of Transnational Literacies: How Youth Live and Imagine Social Worlds in their Digital Media Practices

AbstractThis study explores the transnational literacies that contribute to creating online social connections among migrant youth that may support their development and navigation of life across countries. We examine how social connectedness is semiotically constructed through time–space framing among two youth of Chinese descent who were participants of a larger study of the digital media practices of young people in an urban high school. We build on the concept of chronotope (Bakhtin, 1981) and scholarship of transnational literacies to understand the space–time dimensions of digital literacy practices, specifically how youth create the spatiotemporal context or frame of reference for their actions and positionings with others across geographical distances. Using a case study approach with data from interviews and observations, we analyzed how the youth depicted their transnational social relations within particular time–space frames. Qualitative and discourse analyses of the youths' narrative accounts show that they positioned themselves in proximity with their transnational peers within particular time–space contexts that supported their actions and emotions, and how they made sense of events, issues, practices, and their own identities as transnational individuals. The youths' ideas of schooling and education, and attunement to nationalistic ideologies, were developed through multiple chronotopes in their social connections across countries. This study offers implications for how an attention to the transnational spatiotemporal frame of youths' discourse and narrative may give us a more nuanced understanding of the subjectivity, knowledge, and perspective they derive from their experiences of movement and connection across borders.

Deformation mitigation and twisting moment control in space frames

Over the last five decades, space frames have centered on the modernization of touristic zones in view of architectural attractions. Although attempts to control joint movement and minimize axial force and bending moment in such structures were made sufficiently, twisting moments in space frames have been underestimated so far. In space frames, external load or restoring the misshapen shape may cause twisting in members. We herein developed a robust computational algorithm to reduce the induced torsional moment through shape restoration within a desired limit by changing the length of active bars that are placed in space frames. Applying optimization algorithms like interior-point and Sequential quadratic programming (SQP), a direct correlation was pursued between bar length alteration and twisting in structural members. A numerical model of a single-layer space frame resembling an egg captures the twisting moment in all members, achieving a specified limit. The overall length change of the active members using an iterative process based on a heuristic that considers a threshold on the minimum length change of the active members.

Homotopy properties of the complex of frames of a unitary space

AbstractLet be a finite‐dimensional vector space equipped with a nondegenerate Hermitian form over a field . Let be the graph with vertex set the one‐dimensional nondegenerate subspaces of and adjacency relation given by orthogonality. We give a complete description of when is connected in terms of the dimension of and the size of the ground field . Furthermore, we prove that if , then the clique complex of is simply connected. For finite fields , we also compute the eigenvalues of the adjacency matrix of . Then, by Garland's method, we conclude that for all , where is a field of characteristic 0, provided that . Under these assumptions, we deduce that the barycentric subdivision of deformation retracts to the order complex of the certain rank selection of that is Cohen–Macaulay over . Finally, we apply our results to the Quillen poset of elementary abelian ‐subgroups of a finite group and to the study of geometric properties of the poset of nondegenerate subspaces of and the poset of orthogonal decompositions of .

New characterization of Robertson–Walker geometries involving a single timelike curve

Abstract Our aim in this paper is two-fold. We establish a novel geometric characterization of the Robertson–Walker (RW) spacetime and, along the process, we find a canonical form of the RW metric associated to an arbitrary timelike curve and an arbitrary space frame. A known characterization establishes that a spacetime foliated by constant curvature leaves whose orthogonal flow (the cosmological flow) is geodesic, shear-free, and with constant expansion on each leaf, is RW. We generalize this characterization by relaxing the condition on the expansion. We show it suffices to demand that the spatial gradient and Laplacian of the cosmological expansion on a single arbitrary timelike curve vanish. In General Relativity these local conditions are equivalent to demanding that the energy flux measured by the cosmological flow, as well as its divergence, are zero on a single arbitrary timelike curve. The proof allows us to construct canonically adapted coordinates to the arbitrary curve, thus well-fitted to an observer with an arbitrary motion with respect to the cosmological flow.

A Folded Coil Design for Cubic Wireless Charging Space Frames With Even Magnetic Flux Density Distribution

A Folded Coil Design for Cubic Wireless Charging Space Frames With Even Magnetic Flux Density Distribution

Analysis of Planar Double-Layer Timber Spatial Frames by Using Parametric Tools

It is in the preliminary design phase of a project that the designer makes decisions concerning the global geometry of the structure. When working with space frames, the choice of the frame topology is key for the structural behavior. It is difficult to find manuals that provide guidance on which of the most common topologies is the right one for the project, let alone in wood construction. In response to this shortcoming, the use of parametric software is proposed (Grasshopper build1.0.0007 and Karamba 3D 2.2.0.16-220828). The aim is to create a dynamic catalog that responds instantaneously to changes in the parameters to provide information on structural behavior, pre-dimensioning and metrics. With the display of all this information, the architect will have enough technical argumentation to choose or reject options. The proposal is developed through a case study: the early design and analysis stages of flat double-layer timber spatial frames as for rectangular medium-span roofs.

Evaluasi Rasio Kapasitas Plat Lantai Jembatan Pangwa Berdasarkan Mutu Beton Aktual

This article reviewed the effect of decreasing quality of concrete in the vehicle deck on Pangwa bridge located in Trienggadeng, Pidie Jaya district, Aceh Province. The bridge deck was planned to use concrete with a quality of 30 MPa, however in practice, it was estimated that only 18.8 MPa was achieved. Based on the actual concrete quality, this article reported a reanalysis of the bending and shear capacity ratio. Structural analysis was carried out using SAP2000 software referring to engineering design data. The stages include modeling the bridge as a space frame steel construction with a deck using reinforced concrete material, loads calculation, internal force analysis, and checking the structural capacity. Load calculations and load combinations refer to the standard Loading for Bridges (SNI 1725: 2016). The bridge deck was analyzed as a one way slabs using D16-150 reinforcement with steel grade fy = 320 MPa. The loads taken into structure analysis include: self weight, additional dead load, truck load, and wind load. Based on the loads on the bridge, it is estimated that the possible forces arising from certain conditions are calculated based on the ultimate load combination of Strength-I, Strength-II, Strength-III, Strength-IV and Strength-V according to the provisions of SNI 1725-2016. Based on the results of the structural analysis recapitulated from the value of the load combination, the maximum and minimum moments were 388.68 kN.m and -391.22 kN.m while the maximum shear force were 169.60 kN. The planned bending capacity was 396.303 kN.m (design) and was achieved at 365.568 kN.m (actual) or 7.75% less than the ultimate moment. The pons shear force arising on the bridge deck was Vu = 169.6 kN with pons shear capacity, ØVn = 874.895 kN in the design data and was achieved by 703.811 kN (actual). Based on the results of these calculations, it can be concluded that Pangwa bridge still meets the level of safety for the use as a vehicle traffic lane.

“We're loud, why aren't you?” Laura’s social media activism through justice-oriented literacies

PurposeSocial media offers youth a virtual platform to build community and amplify underrepresented voices. Online spaces are often used to respond to societal issues and adopt various roles. This article aims to focus on Laura's case, spotlighting the intersection of online activism by a youth of Color, and social media literacies used to demonstrate civic engagement around contemporary social justice issues.Design/methodology/approachThrough case study methods, the author examined how a youth of Color used social media to employ critical literacy practices as tools for civic engagement, advocating for social justice, and navigating the complexities of identity work in online spaces, spotlighting Laura, a self-identified Mexican and Ecuadorian Latine 18-year-old activist, to understand how social media shapes multimodal literacy practices, how youth build culture, engage in literacies and craft civic identities online.FindingsFindings examine Laura’s social media literacies toward social justice activism, contributing to the understanding of youth activism, digital identity and civic engagement. Findings will also examine how Laura enacts online literacy practices related to her racialized identities, and how she engages in activism and civic participation related to social justice issues. These findings contribute to the understanding of youth activism, digital identity and civic engagement.Originality/valueThis paper focuses on Laura’s practices within the larger frame of politics, digital space and youth culture. Moreover, it also highlights the potential of youths' multifaceted social media literacies to redefine the educator's role by fostering youth identity and social justice literacies.

Damage analysis and mechanical performance evaluation of frame structures in recycling

Research on the recycling of space frame structures is beneficial to reduce the waste of resources and has important engineering application prospects. Repeated disassembly tests were carried out on a full size space frame structure with bolt-ball joints. The maximum number of cycles was 3. The test results showed that with the increase of the number of cycles, the damage of joints and tubes gradually increased, the phenomenon of false tightening increased, and the construction efficiency decreased. After three cycles, the damage of high-strength bolts accounted for 16.56 % and the damage of steel tubes accounted for 5 %. Due to the component damage and construction deviation, the deformation and stress of the structure after unloading could not be restored to that before loading. However, within three cycles, the overall displacement and stress of the frame structure under general roof loads were almost not affected by component damage and construction deviation. Furthermore, the distribution pattern of displacement and stress was independent of the number of cycles. The maximum mid-span displacement of the structure was about 80 mm and the maximum difference of the overall stress level was within 10 MPa. Finally, according to the test results, the relevant engineering suggestions for the recycling of space frame structures were put forward.

An optimal design approach for steel space frames with T-stub semi-rigid connections considering soil-structure interaction

An optimization technique for designing the steel space frame with T-stub semi-rigid connections and interaction between soil and structure is presented in this article. A three-parameter-based elastic foundation model is utilized to investigate soil-structure interactions (SSI). To enable two-way data transfer for all optimization methods, computer software was developed using C# version 17.8.6, which connects to SAP2000-OAPI version 22. Particle swarm optimization (PSO) and teaching-learning-based optimization (TLBO) are employed for optimal designs. These optimization techniques choose profile sections from a list, including 64W discrete sections from the American Institute of Steel Construction (AISC). The Load and Resistance Factor Design-American Institute of Steel Construction (LRFD-AISC) strength constraints, geometric constraints, inter-storey drift constraints, and displacement constraints are considered during optimization. The first phase entails creating optimal designs for two unique steel space frames that consider SSI but do not include T-stub semi-rigid connections. Following that, the same optimization procedures are carried out with T-stub semi-rigid connections. The parameters needed for the foundation model are obtained through soil surface displacements. Utilizing T-stub semi-rigid connections while considering the interaction between the structure and the soil produces increased structural weight.

Analysis of Progressive Collapse Resistance in Precast Concrete Frame with a Novel Connection Method

The configuration of beam–column joints in precast concrete (PC) building structures varies widely, and different connection methods significantly affect the progressive collapse resistance of the structure. This study investigates the progressive collapse resistance of an innovative beam–column connection node frame. Finite element models of four-story, two-span space frame structures made of reinforced concrete (RC) and PC were developed using ANSYS 14.0/LS-DYNA R5.x software, employing nonlinear dynamic and static analysis to examine structural collapse behavior under bottom middle or corner column damage. Numerical results indicate that following the failure of the middle or corner column due to explosion loading, the vertical displacement and collapse rate of the PC structure with the novel connection method are less than those of the RC structure during collapse progression. Furthermore, upon removal of the middle or corner column, the residual load-carrying capacity of the PC structure with the innovative connection increased by 7% and 3.7%, respectively, compared to the RC structure. This suggests that PC structures with this type of connection demonstrate superior performance in resisting progressive collapse, offering valuable insights for future engineering applications.

Database of tall pre-Northridge steel moment frames for earthquake performance evaluations

This article describes a detailed database of tall steel moment frame buildings that are representative of the construction practices in San Francisco prior to the 1994 Northridge earthquake. The database contains design details that affect the structural performance of steel moment frames, including frame geometry, member cross-section sizes, and gravity system characteristics. This database also captures irregularities that might impact seismic response, such as podiums, setbacks, mass concentrations (mechanical, electrical, and plumbing (MEP) floors), interrupted column lines, and atriums. The database includes information on 89 moment frame buildings, 14 of which were built before 1960 and are constructed with riveted connections, while the remaining 75 have welded flange connections like those that suffered brittle fracture during the 1994 Northridge earthquake. The buildings are further distinguished between space frame, perimeter frame, and partial space frame systems. For about half (41/89) of the buildings in the database, section sizes of representative structural members were collected, which enabled the evaluation of the seismic design, elastic, and inelastic response using computational workflows. The design diagnostics indicate that most of the buildings meet the minimum seismic strength and strong-column weak-beam requirements of modern building codes, even though they were not necessarily designed with this intent. On the contrary, about one-third of the buildings do not meet the seismic design drift limit of current codes, and about half of them have weak beam-column panel zones. This database, associated structural analysis models, and processing scripts are published at DesignSafe https://doi.org/10.17603/ds2-wjad-r340 to facilitate collaboration and continued development of open-source data for high-resolution simulations to inform risk mitigation strategies on a regional scale.

Influence of idealized joint models on the design of timber space frame on poles

Influence of idealized joint models on the design of timber space frame on poles

Construction of continuous controlled K-g-fusion frames in Hilbert spaces

We present the notion of continuous controlled K-g-fusion frame in a Hilbert space which is generalization of discrete controlled K-g-fusion frame.We discuss some characterizations of a continuous controlled K-g-fusion frame. A relationship between a continuous controlled K-g-fusion frame and a quotient operator has been studied. Finally, stability of a continuous controlled g-fusion frame has been described.

Controlled frames in n-Hilbert spaces and their tensor products

The concepts of controlled frame and its dual in n-Hilbert space have been introduced and then some of their properties are going to be discussed. Also, we study controlled frame in tensor product of n-Hilbert spaces and establish a relationship between controlled frame and bounded linear operator in tensor product of n-Hilbert spaces. At the end, we consider the direct sum of controlled frames in n-Hilbert space.

Influence of Soil Structure Interaction on Seismic Performance of Steel Structure Interaction with Different Types of Foundations and Soil

Soil Structure Interaction is the reaction of soil that influence the motion of the structure. During serve seismic events, the dynamic response of the structure is affected not only by the behavior of the superstructure but also by the nature and behavior of the soil present in and around the substructure. The steel structure design process usually assumes the base of the foundation to be completely restrained in a fixed base condition. In the present project the influence of soil structure interaction on the seismic performance of a steel space frame on different soil has been investigated. The multi-story steel building (G+7) with column to column spacing distance 5m and six number of columns having both X and Y direction of the structure, is designed to withstand self-weight and seismic loads. The study also examined the impact of earthquake loading on the steel structure with soil structure interaction using Response Spectrum Method and Time History Method for seismic zone III, with forces determined using IS 1893 (Part-3):2015. The study measured the displacement of steel structure with influences of soil under seismic forces. Comparison of seismic performance like maximum storey displacement, maximum storey drift and base shear along with soil structure interaction under different types of soil are presented in this project. This paper discusses the influences of the soil structure interaction on steel structure with various configuration and different types of foundations and soil.