Structural System Research Articles

Enhancing structural efficiency with digital concrete – Principles, opportunities and case studies

This paper explores the opportunities of digital fabrication with concrete (DFC) to improve structural efficiency and achieve sustainable construction. Efficient structural solutions that drastically reduce material consumption can be achieved by ensuring direct load flow and placing material where needed. More than 50 % of material savings can be achieved by using flanges or hollow sections, providing continuity in beams or slabs, reducing the span of structures or using structural systems such as arches, trusses or deep beams. These concepts are not fully exploited as they often require expensive and complex formwork. DFC tackles the latter point, as it promises to produce complex geometries, minimising extra effort, cost, or waste. The paper discusses the optimisation potential of DFC for several structural elements and presents existing applications that demonstrate this potential. Five case studies of different technological approaches are discussed in detail, highlighting advantages and disadvantages to be addressed for widespread adoption.

Postmodernity Fears and Transformations of Teachers’ Identities

Postmodernity affected educational systems and teaching practices in several ways, such as deconstructing knowledge and changing the power dynamics in class, as well as putting emphasis on diversity, inclusivity, interdisciplinary approaches, critical pedagogy, and reflexivity. These changes led to the alterations and fluidity of teachers’ professional identities. The purpose of this small-scale qualitative research is to depict teachers’ fears in association with changes in their profession caused by postmodernity. Two distinct tools were used: a priority list and an explanation-justification template for each respondent to indicate the reasons behind their priority choices. Thematic analysis was used to indicate major themes and subthemes in the participants’ verbatim answers. Findings indicated that teachers at different stages of their careers are worried about continuous educational and environmental changes. Younger teachers with less experience are especially worried about systemic changes and abruptions that affect not only their profession but their lives as a whole. The findings of this study verify previous research concerning teachers’ professional identity determinants with an emphasis on contextual factors and career advancement. Postmodernity as a factor underpinning professional alterations indicates that the dominance of various factors depends on variations between contexts, cultures, and structures of educational systems, as well as on the psychological mechanisms employed by individuals in forming the perception of their self.

Elastic–Plastic Buckling of Scaled Model of Radial Ring-Stiffened Shallow Spherical Shells Based on Energy Method

Stiffened shallow spherical shell has the advantages including high strength and light weight, which allows it to be widely applied in areas including aerospace, submarine and civil engineering. For the design of scaled model for elastic–plastic buckling of a large radially–circumferentially stiffened shallow spherical shell under uniformly distributed pressure and for the purpose of similarity prediction, the similarity relation of the elastic–plastic buckling coefficient of the shell is derived; then by using the dense stiffening theory and considering the dual nonlinearity of geometry and materials, the energy increment formula for the structure under uniformly distributed external pressure is established; next, based on the similarity transformation of the energy increment of the structural system, the generalized similarity condition and similarity relation of elastic–plastic buckling of the structure under uniformly distributed external pressure are identified. Based on the scaling and equivalence of tensile–compressive stiffness and bending stiffness, the distortion scaled model for the prototype is designed. Through numerical simulation, the distortion similarity prediction for elastic–plastic buckling under uniformly distributed pressure of the radially–circumferentially stiffened shallow spherical shell that has square-shaped dimple defects has been conducted; based on the derived similarity relation of elastic–plastic buckling of stiffened plate, the similarity prediction for the elastic–plastic buckling of orthogonally stiffened plate in the plane under unidirectional uniformly distributed pressure has been conducted. The results indicate that the load–displacement curve, buckling load, and buckling mode of the distortion similarity scaled model, combined with the established radial displacement scaling factor expression, the scaling relation of tension–compression stiffness, and the similarity relation of buckling mode, can effectively predict the elastic–plastic buckling characteristics of its prototype structure. The research results can provide theoretical reference for the design and test of the scaled model with distortion of elastic–plastic buckling of similar stiffened large shell structures.

FDIA localization and classification detection in smart grids using multi-modal data and deep learning technique

False data injection attacks (FDIA) exploit the vulnerabilities of bad data detection in energy management systems to maliciously tamper with state estimation results, seriously jeopardizing the safe and reliable operation of power systems. In order to promptly detect FDIA, recent studies have used machine learning techniques to extract attack characteristics and detect FDIA based on changes in these characteristics. Current research predominantly focuses on detecting a single type of FDIA attack model and topology. However, the increasing diversification of FDIA construction methods and the variability of topological structures in power systems can reduce or even invalidate detection effectiveness. To cope with the abovementioned difficulties, this study introduces a multimodal deep learning detection model based on variational graph auto-encoders (VGAE), temporal convolutional networks (TCN), and gated recurrent units (GRU). The topological features of power systems are obtained through VGAE to adapt to the detection needs of various topological structures and performance enhancement. These features are then integrated with preprocessed measurement data via BDD to form multimodal data. Furthermore, this multimodal data is used to locate and classify FDIA with complete information, FDIA with incomplete information, and topology attack after applying a multi-label classification algorithm based on TCN-GRU for temporal feature extraction. Experiments carried out on the IEEE 14 and IEEE 118 bus systems show that the proposed method is robust and has high detection performance. The results indicate that the proposed detection method achieves AUC values that are, on average, 0.085, 0.145, and 0.04 higher than those of CNN, LSTM, and CNN-LSTM, respectively. Moreover, under various noise and attack intensities, recall, precision, F1 score, and RACC remain above 0.859, 0.877, 0.867, and 0.818, respectively, with a classification accuracy greater than 0.912. This study provides a unique perspective on detecting FDIA across various attack models and power system topologies.

Resolving the Refractive Indices of Transparent and Translucent Liquids from the Spacings, Spatial Frequencies, and Directions of Interference Fringes

In this work, we present a novel approach to resolve the refractive indices of transparent and translucent liquids from straight interference fringes. The optical path difference between the two arms of the Mach–Zehnder interferometer is first derived by assuming a reference plane wave interfering with a plane wave passing through a rectangular cuvette. The analytic expressions for the liquid refractive indices are then deduced, describing how the refractive index is related to the fringe spacings, spatial frequencies, and directions. The structure coefficients in the above formulas are determined from the fringe spacings and directions of the interference patterns of the empty cuvette and the cuvette filled with a liquid of a known refractive index. The NaCl solution and Coca Cola are adopted as the test examples to show experimentally the validity of the proposed method. There is good agreement between the refractive indices obtained from the fringe spacings and direction of a single interference pattern. The sensitivity and resolution of this method are dependent on the structure of the experimental systems and thus can be adjusted in a controlled manner. The proposed method is simple to implement and can be easily extended to other high precision optical interferometer systems.

Application of magnetic data and satellite spectral imaging in identifying gold mineralization zones and its associated subsurface structures at Fawakheir-Attala area, Central Eastern Desert, Egypt

The Fawakheir-Attala gold mining zone in Egypt’s Central Eastern Desert features a diverse range of rock formations, including Precambrian crystalline rocks and Phanerozoic sedimentary formations. These formations encompass gneisses, metavolcanics, metasediments, a metagabbro-diorite complex, Dokhan volcanic rocks, and granitic rocks, alongside lower and upper Nubia sandstones. Faults and shear zones are pivotal in controlling gold mineralization within the area, indicative of substantial mineral wealth. This study aimed to map subsurface structural characteristics and investigate gold mineralization zones using aerial magnetic data and ASTER remote sensing, the latter of which played a crucial role in highlighting the surface exposure of alteration zones. Geological surveys combined with remote sensing techniques were employed to identify rock types and mineralization zones, while magnetic methods, including aeromagnetic surveys and ground-based studies, were used to reveal underlying structural properties and fault systems. Analysis of aeromagnetic data revealed a large mineralization zone running from the Fawakhir Gold mine through the Attala Gold mine in a NW–SE direction. Various structural trends and faults, including NW–SE, NE–SW, E–W, and N–S directions, were identified, strongly associated with hydrothermal alteration zones and gold mineralization. Shallow basement relief was observed in the eastern and central regions, contrasting with deeper formations and greater relief in the western section. Land magnetic surveys were utilized to identify new areas for gold mineralization, with geochemical analysis confirming gold content in quartz veins and host rocks. The integration of magnetic and remote sensing techniques effectively highlighted alteration zones indicative of potential mineralization, which could have a subsurface continuation, aiding in the identification of gold occurrences connected to faults, lineaments, and mineralization zones.

Novel multivariate design concept for floating wind turbines by Gaidai multivariate reliability method and deconvolution scheme

Development of novel risk and reliability assessment methods is intended to support safer construction of offshore structures, subjected to environmental wave loads. Current study investigated 10-MW FWT (i.e., Floating Wind Turbine), operating under realistic environmental conditions. While increasing operating safety, enhanced risk and reliability assessment methods may eventually help reduce manufacturing and maintenance costs. Excessive structural dynamics being usually caused by environmental stressors, acting on structural system. Environmental loads resulting from ambient wind and wave motions are typical for offshore structures. Current work advocates a novel risk and reliability assessment methodology that allows for reliable forecasting of failure/damage risks, arising from excessive FWT structural dynamics. Recently developed Gaidai multivariate reliability methodology along with state-of-the-art deconvolution method had been employed. Unlike existing reliability approaches such as Weibull-type, GP (i.e., Generalized Pareto), POT (i.e., Peaks Over the Threshold), etc., the recommended methodology does not rely on any pre-assumed functional class, when extrapolating failure probability functional tail. Practical advantages of the suggested multivariate reliability methodology combined with deconvolution scheme over, that is, 4-parameter Weibull’s extrapolation method had been demonstrated. Suggested methodology makes effective use of even limited underlying datasets, enabling robust and accurate projections of multidimensional structural system failure/damage risks. Overall methodological performance suggests that numerically stable and accurate extreme dynamics forecasts for FWT structural bending moments might be obtained, utilizing suggested multivariate reliability methodology. Deconvolution extrapolation approach being more numerically stable than parametric extrapolation techniques, due to its non-parametric nature.

Effect of Co-content on microstructure, phases, and mechanical properties of laser additive manufactured Cox(CrNi)100-x alloy

This study describes the combination of mechanical properties of the CoCrNi medium entropy alloy system by tailoring its non-equiatomic compositions. The Laser Directed Energy Deposition (LDED) based Additive Manufacturing (AM) technique is deployed to fabricate the Cox(CrNi)100-x (x=40, 50, 60) alloy system. All compositions exhibit the formation of solidification substructures, with the refinement of subgrain size correlated with an increase in Co-content. The Co40 alloy exhibited a single-phase FCC structure, while Co50 (3.1 % ε-martensite) and Co60 (53.6 % ε-martensite) exhibited dual FCC+HCP structure during deposition. The combined effect of dislocation slip, deformation twinning, and deformation-induced HCP ε-martensite transformation strengthened the Co40 alloy during deformation. However, the Transformation-Induced Plasticity effect (TRIP) resulted in greater HCP ε-martensite transformation during deformation. Due to limited slip systems in the HCP structure, the Co60 alloy showed lower strength. The TRIP effect is highly dominant in Co60 alloy due to the prevalent HCP phase fraction in the initial samples. This led to stress concentration at FCC grain boundaries and ε-martensite, resulting in early failure of the alloy. With the increase in Co-content, the deformation mechanism changed from dislocation slip to deformation twinning to HCP ε-martensitic transformation. The LDED-built Cox(CrNi)100-x alloy system showed a good combination of strength and ductility. The study suggests that additive manufacturing is an easier and more suitable technique for obtaining compositions with the desired combination of mechanical properties.

Die afbakening van die kern van die Afrikaanse poësiesisteem (2000–2022)

A core/periphery structure is a concept often used in various disciplines to examine the structure of different systems. In the study of Afrikaans literature, this structural facet is also a well-known topic and one that has already been written about extensively. It is generally assumed that actors within the core of a system are more important, authoritative, established and stable, while actors on the periphery often fulfill less important roles, are more dynamic and are also often newcomers. However, the question arises how it can be determined scientifically which role players function within the core of the system, and how the core can be demarcated. In this article, a network analysis of the contemporary Afrikaans poetry system is undertaken, and with the help of network concepts such as the k-core and eccentricity, it is shown how and where the core and the absolute core of the Afrikaans poetry system can be delineated. This approach provides an objective and scientific way to examine the structure of the poetry system. As such, the study connects to previous studies of the Afrikaans poetry system as a system and as a network, but the current study applies new criteria to a new data set and delineates the core of this system.

Psychologists aspiring to leadership positions in public sector health care.

Psychologists are well-positioned to take on leadership roles in health care systems as a result of the broad-based skills included in doctoral level, professional training programs. These include knowledge of evidence-based practice, extensive training in applied research and clinical practice, emphasis on critical thinking in scientific methods and hypothesis testing, teaching, supervision, team consultation, and continuous learning (APA Presidential Task Force on Evidence-Based Practice, 2006; Korman, 1974; McFall, 2007). Formal opportunities to learn how to apply these skills in leadership and organizational management roles are, however, limited during graduate training. There have been recent efforts within the American Psychological Association to foster interest and readiness for leadership roles among psychologists. These efforts have included a leadership development fellowship, on-demand webinars, and online learning for continuing education (American Psychological Association, 2023). The content of these training opportunities is typically general in nature so that it can be applied to all types of organizational settings. Psychologists interested in leadership positions within public sector health care organizations are likely to benefit from information that aligns more specifically with the mission and organizational structures of such systems. This article presents a conceptual framework to prepare psychologists aspiring to leadership positions in public sector health care. Leadership theories and models from organizational management science are outlined which capture the context and organizational goals of such programs. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Approximate Bayesian Computation for structural identification of ancient tie-rods using noisy modal data

Masonry arches and vaults are common historic structural elements that frequently experience asymmetric loading due to seismic action or abutment settlements. Over the past few decades, numerous studies have sought to enhance our understanding of the structural behavior of these elements for the purpose of preventive conservation. The assessment of the structural performance of existing constructions typically relies on effective numerical models guided by a set of unknown input parameters, including geometry, mechanical characteristics, physical properties, and boundary conditions. These parameters can be estimated through deterministic optimization functions aimed at minimizing the discrepancy between the output of a numerical model and the measured dynamic and/or static structural response. However, deterministic approaches overlook uncertainties associated with both input parameters and measurements. In this context, the Bayesian approach proves valuable for estimating unknown numerical model parameters and their associated uncertainties (posterior distributions). This involves updating prior knowledge of model parameters (prior distributions) based on current measurements and explicitly considering all sources of uncertainties affecting observed quantities through likelihood functions. However, two significant challenges arise: the likelihood function may be unknown or too complex to evaluate, and the computational costs for approximating the posterior distribution can be prohibitive. This study addresses these challenges by employing Approximate Bayesian Computation (ABC) to handle the intractable likelihood function. Additionally, the computational burden is mitigated through the use of accurate surrogate models such as Polynomial Chaos Expansions (PCE) and Artificial Neural Networks (ANN). The research focuses on setting up numerical models for simple structural systems (tie-rods) and inferring unknown input parameters, such as mechanical properties and boundary conditions, through Bayesian updating based on observed structural responses (modal data, strains, displacements). The main novelties of this research regard, on the one hand, the proposal of a methodology for obtaining a reliable estimate of the axial force in ancient tie-rods accounting for different sources of uncertainty and, on the other hand, the application of ABC to obtain the structural identification inverse problem solution.

Assessment of a Force Method for the Resilient Seismic Design of Special Moment-Resisting Steel Frames with Hysteretic Energy Dissipation Devices

In this paper, the authors present the results of nonlinear dynamic analyses of twelve building models designed according to a methodology based upon the force method, capacity design principles and the concept of structural fuses to achieve resilient seismic designs for special moment-resisting steel frames with hysteretic energy dissipation devices mounted on chevron steel bracing. It is demonstrated that the resilient design mechanism previously checked with pushover analyses is also attained for most studied models with nonlinear dynamic analyses using an acceleration record which is compatible with the elastic design spectrum. Also, it is corroborated that the planned second line of inelastic defense is activated if the seismic action surpasses the considered design spectrum. Based upon the obtained results, it is confirmed that it is possible to perform a resilient seismic design for the studied system under the proposed methodology, even for tall and slender buildings. Therefore, the proposed initial stiffness ratio parameters and the global design parameters previously proposed by the authors to use in a code-oriented force method can be used with confidence for the resilient seismic design of this structural system.

Biocompatibility and Antibacterial Activity of Eugenol and Copaiba Essential Oil-Based Emulsions Loaded on Cotton Textile Materials.

The present study was focused on the preparation, characterization and application onto cotton fabrics of different topical oil-in-water emulsions based on chitosan, eugenol and copaiba essential oil for potential topical applications. Different amounts of copaiba essential oil (oil phases) and eugenol were used, while the water phase consisted of hamamelis water. The designed formulations were evaluated via optical microscopy and rheological parameters assessment. The textile materials treated with the developed emulsions were analyzed in terms of antibacterial efficiency and in vitro and in vivo biocompatibility. The rheological measurements have shown that the emulsions' stability was dependent on their viscosity and structure of the colloidal systems. The emulsions remained stable at temperatures equal to or below 35 °C, but an increase in temperature led to droplet flocculation and creaming. The emulsion-treated textiles exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus, and in vivo biocompatibility on the skin of guinea pigs without sensitization effects. Our study revealed that eugenol and copaiba essential oil-based emulsions loaded on cotton textile materials could be promising candidates for developing skin-friendly textiles designed for different topical applications.

Retention of verbal and nonverbal information in the working memory. An analysis of functional and effective connectivity

In this work we estimated differences in the structure of brain systems that ensure encoding and retention in working memory (WM) of two types of information: verbal (letters) and non-verbal (segments of an open broken line) sequences presented either statically or dynamically. Brain systems were characterized by the strength of functional and effective connections between eight approximately bilaterally symmetrical cortical loci, including the dorsolateral prefrontal cortex (dlPFC) and regions of the temporal (STG), parietal (IPS), and occipital (v2) cortices. Using an 8-channel vector autoregressive model in the space of cortical EEG sources, it was shown in a group of subjects in whom high-density EEG was recorded that: (1) the brain organization of the WM when holding a sequence of letters differs from that when holding a sequence of broken line segments; (2) the brain organization of the WM depends on the mode of presentation of sequences: the strength of the functional connection is different during dynamic and static presentation of the sequence; (3) differences in the structure of functional and effective connections are not of a pronounced frequency-selective nature and are observed in all studied EEG frequency ranges from theta (4–8 Hz) to high-frequency gamma (50–60 Hz); (4) the most reliable differences between the task of retaining a sequence of letters and the task of retaining a sequence of broken line segments are observed in the alpha and beta frequency ranges during static visual presentation of sequences in the strength of functional connectivity measured using coherence between the left hemisphere dlPFC and the right hemisphere STG, as well as in theta range between the right hemisphere dlPFC and the left visual cortex v2; (5) the most reliable difference between static and dynamic presentation modes is observed in the task of holding broken line segments in the gamma frequency range (50–60 Hz) between the dlPFC in the right hemisphere and the left visual cortex v2.

Smart structural health monitoring using computer vision and edge computing

Structural health monitoring (SHM) provides real-time data on the condition and performance of infrastructure, enabling timely and cost-effective maintenance interventions, and hence enhanced safety and extended service life. The computer vision-based non-contact sensor has emerged as a promising alternative to conventional contact-type sensors for structural displacement measurement and SHM. Many of the currently reported vision-based structural displacement measurement systems typically temporarily set up a video camera from a distance to the structure. The collected images or videos are usually stored locally and post-processed offline to obtain structural displacement responses, which is cumbersome and limited to short-term SHM applications. The recent development of technologies empowered by the Internet of Things (IoT) and edge computing has enabled real-time video processing and analysis at the source, minimizing latency, reducing bandwidth requirements, and enabling prompt decision-making, thereby enhancing efficiency and responsiveness compared to traditional offline video recording and processing systems. In this paper, an edge computing vision-based displacement measurement system (EdgeCVDMS) is developed. Video recording, processing, and displacement response identification are entirely performed on an edge device integrated with the vision-based displacement tracking algorithm, thereby greatly reducing the amount of data transmitted to the cloud server. The feasibility and applicability of the developed sensing system are experimentally validated on a laboratory-scaled transmission tower structure. The proposed EdgeCVDMS is cost-effective, easily deployable, and of great potential to be applied for the condition assessment of a larger population of aging civil infrastructure.

Data Industry Green Development Promoted by Public Policy and Law in China

It is difficult to fully match the current green development initiatives in the context of public policy and industrial economy to the new infrastructure process driven by massive data. Its connotation and extension and the level of the rule of law need to be deepened to ensure that data production, processing, circulation, elimination, and other activities can achieve high-quality and sustainable development within the collaborative construction of hard facilities and the soft environment in the new era. Based on the practical needs of data industry green development in key areas, we can resolve the legal risk of data industry green development from three aspects: improving the legal level of green public policy, clarifying the green legal benchmark of data industry development, and improving the green legal system of digital society. Then, this paper considers the design of an environmental protection system based on hardware facilities and the structural and readable clean data system innovation of the soft data industry development framework mode so as to clarify the legalization scheme of data industry green development under the new infrastructure. Overall, achieving the green development of the data industry requires not only active attempts by China but also joint efforts by China and other countries.

Analytical Investigation of the Effects of Additional Load Mass on the Fundamental Frequency of Pedestrian Beam Bridges

The aspect of resonant vibrations due to pedestrian movement is of great significance in engineering practice. Therefore, understanding the variations in the natural frequency of bridge structures under varying positions of additional mass is of particular interest. This paper presents a procedure for the straightforward determination of the natural frequencies of a beam pedestrian bridge for various positions of pedestrians or a service vehicle based on derived analytical solutions. The calculation takes into account the inertial effects of the additional load mass, modeled as either uniformly distributed or concentrated. The importance of additional load mass effects on the fundamental frequency of a beam pedestrian bridge and its dynamic response to a moving pedestrian load is demonstrated on a bridge example. The proposed solutions are also applicable to other girder system structures with uniform mass and stiffness along their span.

Interconnection of irreversible port Hamiltonian systems

This paper shows how the interconnection of two controlled Irreversible port Hamiltonian Systems has to be state and co-state modulated in order to ensure the closed-loop Irreversible port Hamiltonian structure, satisfying the first and second laws of Thermodynamics. It proposes a precise parametrization of this modulation from the open-loop systems structures in order to guarantee the consistency of the closed loop energy and entropy balance equations. The results are illustrated by means of the examples of a heat-exchanger, a gas-piston system and a chemical reaction.

Control of a building system with sudden nonlinearity using the sliding mode technique

In civil engineering application such as the seismic resistant structural design, a building system often enters into its nonlinear range to minimize the force transfer to the superstructure. An ideal control design should enhance the usefulness of the nonlinear behavior by diminishing its adverse effects at a minimal control input. This study developed a unified feedback mechanism based on the sliding mode control approach that fostered the multiple selected modal control of a structural system undergoing linear and nonlinear stages of hysteretic deformations. The ideal sliding surface for controlling a specific mode was designed based on the interaction characteristics between two modes at two different stages of deformation. An ′ S′ type functional form of the control force was developed on either side of the sliding surface based on the velocity feedback of the system by ensuring reachability to the ideal sliding surface. To demonstrate the effectiveness of the adopted control, a five-story shear building with uniform mass and initial stiffness distribution with concentrated nonlinearity at the base column was considered under 10 earthquake excitations. The system was studied under the proposed control along with the uncontrolled system. In addition to the adopted control, a popular and existing LQG control technique was also implemented based on the equivalent linearized structural system for comparison. The adopted control provided the desired performance of the structural system while keeping the effectiveness of the system’s nonlinearity under earthquake excitations. Considering the system’s responses and the input control force, the efficiency of the adopted mechanism outperformed the LQG control, which was found to amplify the unfavorable effects of the system’s nonlinearity.

Evaluasi Desain Struktur Gedung Pondok Pesantren At-Tibyan Deli Serdang

The structural design of this three-story Islamic boarding school building, the results obtained after analysis include; risk category II so that the earthquake priority factor is 1. The soil site class is soft soil. In the structural system, it is designed using a special moment resisting frame system (SRPMK). The seismic design category obtained is category D. Seismic inspection starting from checking irregularities, diaphragm design, checking the number of structural vibration variations, determining the fundamental period of the structure, seismic response coefficient values, seismic base shear, checking the deviation between floors is carried out based on SNI 1726-2019. for column elements, beams and also plates in existing conditions after analysis have met the requirements based on SNI 2847-2019. The conclusion in this final project research is based on the results of the analysis that the design of the Attybian Islamic boarding school building still meets the requirements based on SNI 1726-2019 concerning procedures for earthquake resistance planning for buildings and non-buildings and also for beam, column and plate elements have met the requirements based on SNI 2847-2019 concerning reinforced concrete structures. However, for the beam elements for the reinforcement requirements, it is still too wasteful so that in this analysis, the amount of reinforcement is reduced because in the planning principle it must be safe and economical.