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Calculating bearing capacity is critical when designing shallow foundations. Many countries use limit state design (LSD) as the standard method for geotechnical design. The paper aims to develop realistic LSD partial factors for bearing capacity calculations of shallow foundations on cohesionless soils based on full-scale model tests. The experimental setup consisted of a hydraulic jack, concrete footing, sand samples, and pressure cells placed in a cylindrical wall. Fifteen sand samples were tested and classified by gradation and relative density. Settlement curves were plotted for each sample under an increasing load. The measured ultimate bearing stresses were found to be higher than theoretical values calculated using traditional methods. This indicates that the traditional approach is conservative. The suggested safety factor for the internal friction angle in cohesionless soils (γtan(ϕ) = 1.10) is notably lower than the values specified in Eurocode 7 at 1.25 and the Egyptian code of practice at 1.30. The proposed LSD partial factors allow for more economical designs than traditional factors while maintaining safety. The full-scale model-testing approach is novel and provides realistic factors directly applicable to Egyptian codes. The results are satisfactory and reasonable for the geotechnical design of shallow foundations on cohesionless soils. [ABSTRACT FROM AUTHOR]

Structural walls are subjected to axial load with bi-axial bending. Despite this, structural walls are designed considering the demand along the strong axis. However, to minimize damage to structural wall it is necessary to design structural walls considering P–Mx–My interaction. Currently, IS 456:2000 recommends design P–Mx–My interaction for columns using a non-dimensional parameter ( α n ). In theory, the recommended α n are meant for symmetric column sections with uniform distribution of longitudinal reinforcement. Consequently, it is necessary to verify the applicability of the design P–Mx–My interaction equation for structural walls. Furthermore, the α n values recommended in the design code are shown to underestimate the flexural capacity of columns, particularly at lower axial load ratios (i.e., Pu/Puz; where Pu is the axial load demand and Puz is the maximum compressive load capacity of the column). To address these issues, the paper recommends design α n values for rectangular RC structural walls. Additionally, the paper presents simplified design equations to develop bi-axial interaction for structural walls. The simplified equations present in this paper are developed using regression analyses of rectangular structural walls with: (a) aspect ratios ranging between 4 and 25, (b) longitudinal reinforcement ratios from 0.5% to 1.5%, (c) reinforcement grades of 415 and 500 MPa, and (d) grade of concrete between M20 and M55. The proposed bi-axial interaction for structural walls will help designers to assess the adequacy of wall with relative ease. [ABSTRACT FROM AUTHOR]

Inconsistencies in standards and codes result in confusion, increased costs, and do not promote the efficient use of concrete. In addition to inconsistencies, the lack of science-based approaches and data used for defining criteria in these standards and codes can limit the reliability and trust of these requirements. A review of industry documents indicates that inconsistencies and lack of science-based approaches exist across many documents, both throughout the industry and within ACI, relating to the corrosion of steel reinforcement embedded in concrete. This paper proposes to address five key issues to promote science-based standardization of requirements necessary for reinforced concrete systems exposed to corrosive conditions. These five issues include the need for: 1) standardization of chloride testing methods and requirements; 2) standardization of chloride reporting units; 3) standardization of terminology for specifying chlorides in cementitious systems; 4) standardization of exposure classifications for corrosive conditions; and 5) standardization of allowable chloride limits. This paper presents current inconsistencies in guide documents and codes for each of the items listed previously and then proposes an approach to standardize each using either available data and/ or a scientifically based approach. Recommendations for testing, reporting, definition of exposure classifications, and allowable chloride limits are then proposed. It is hoped that the systematic approach used herein will lead to standardization and consistency, less confusion, and will promote the efficient use of durable and economical concrete. [ABSTRACT FROM AUTHOR]

The fanning compression stress pattern in RC deep beams under uniform load presents a challenge to formulating the configuration of strut‐and‐tie model (STM). To this end, this paper proposes an alternative method for creating a graphical discontinuous stress field model (DSFM) to fill up the whole beam continuum. It comprises a certain number of trapezoidal stress‐bands with varying bandwidths, and their stress values can be calculated based on force equilibrium conditions. Several stress subfields are defined through a certain stress combination from several directions. The DSFM is implementable for both service limit state (SLS) and ultimate limit state (ULS) in that its configuration is primarily oriented by elastic stress field and only a limited plastic redistribution is allowed for plastic failure. The graphical procedure of DSFM is demonstrated and examined by a test deep beam example, which shows that the predictions are fairly in good agreement with the test results. [ABSTRACT FROM AUTHOR]

This paper reviews previous research and current practice in timber connection design in Australia with reference to methods of deriving design information from test data for nails and screws. The two key documents for timber connection design in Australia are AS 1720.1 design of timber structures and AS 1649 test methods and evaluation of timber connections. These documents have a long history of development, with major changes in design methodologies – from deterministic working stress design to probabilistic limit state design. The supply chain for timber connections has changed with a reduction in the utilisation of timber species and an increase in new fasteners developed for specific purposes. A new approach to the design of timber connections has been proposed to cope with the changing situation. The review is of historic interest but also to ensure that the proposed new approach is consistent with past developments. [ABSTRACT FROM AUTHOR]

Tunnel faces excavated under particularly difficult ground conditions are commonly supported. In case of conventional tunnelling, this support is provided by either improving the mechanical properties of the soil or introducing linear inclusions. This latter technique, consisting in the introduction of fibreglass pipes in the face, is particularly popular since it is very simple to tailor to the different conditions encountered during the excavation the reinforcement spatial distribution. In the current engineering practice, this stabilisation technique is designed by employing simplified approaches not allowing the face displacement estimation. For this reason, in case of deep tunnels in cohesive soils under either undrained or 'partially drained' conditions, these approaches cannot be employed. In this paper, the authors present the practical application of a new displacement based design approach, based on the definition of the face characteristic curve, putting in relation the face displacement to the stress applied on the face. [ABSTRACT FROM AUTHOR]

Relevance. Beam cages are the most common type of floor covering for working areas of buildings and structures. Based on the results of a critical analysis of the existing methods for calculating and arranging the dimensions of beam cells, it was established that there are no clear recommendations on the rational range of selection of the sizes of beam cells depending on the surface load. The purpose of the study is to present the areas of rational operation of steel rolling beams, secured against buckling, based on the requirements of the calculation by the method of limit states. Methods. The tasks set in the work, aimed at achieving the research goal, are solved by analytical methods, relying on the basic laws of structural mechanics and existing knowledge about the actual operation of steel rolling beams under load. Methods of mathematical statistics were used to construct the main dependencies presented on the nomograms. Results. Areas of rational operation of steel rolling beams, secured against curvatures, are determined. The area of rational operation of beams is presented in the form of nomograms, which allow at the design stage to use a beam cell of maximum dimensions. As a criterion for rationalization, the criterion of the simultaneous satisfaction of the accepted section of the beam with the requirements of two groups of limiting states with minimum reserves was chosen. A refined algorithm for the layout of the beam cages and a refined method for calculating the cross-section of rolled beams are proposed, which make it possible to arrange the dimensions of the beam cage with a minimum steel consumption. The increase in the overall dimensions of the cells of the working platforms is substantiated.

Goal based and limit state design is nowadays a well-established approach in many engineering fields. Ship construction rules started introducing such concepts since early 2000. However, classification societies' rules do not provide hints on how to verify limit states and to determine the structural layout of submerged thin-walled stiffened cylinders, whose most prominent examples are submarines. Rather, they generally offer guidance and prescriptive formulations to assess shell plating and stiffening members. Such marine structures are studied, designed and built up to carry payloads below the sea surface. In the concept-design stage, the maximum operating depth is the governing hull scantling parameter. Main dimensions are determined based on the analysis of operational requirements. This study proposes a practical concept-design approach for conceptual submarine design, aimed at obtaining hull structures that maximize the payload capacity in terms of available internal volume by suitably adjusting structural layout and stiffening members' scantling, duly accounting for robustness and construction constraints as well as practical fabrication issues. The proposed scantling process highlights that there is no need of complex algorithms if sound engineering judgment is applied in setting down rationally the hull scantling problem. A systematic approach based on a computer-coded procedure developed on purpose was effectively implemented and satisfactorily applied in design practice. [ABSTRACT FROM AUTHOR]

This paper presents comprehensive parametric analyses on the behavior of damage-repaired steel-concrete composite girders using CFRP sheets. Cross-sectional loss was considered on the lower steel flange at midspan to replicate corrosion damage in the girder. Damage was repaired using CFRP sheets to the underside of the lower flange. Non-linear Finite Element (FE) analyses were conducted on the repaired and intact composite girders. The FE models were validated using experimental results and a parametric study was carried out considering the variables such as number of CFRP sheets, CFRP elastic modulus, damage amount, epoxy resin elastic modulus, concrete strength, flange strength, and CFRP bonding area. The effect of parameters on failure components was studied for Limit States 1, 2, and 3 defined in the revised Design Specification for Highway Bridges in Japan (JSHB) (2017). Limit States 1 and 3 correspond to the service limit and ultimate Limit States in AASHTO, respectively. However, Limit State 2 is JSHB unique Limit State located between 1 and 3 in terms of functionality. Regression models were proposed to determine the load-carrying capacity of the repaired composite girder for 3 Limit States. Comparison between the proposed equation and FE-predicted values showed good agreement with prediction errors of ±10% to ±19%. The study showed that to restore the stiffness and load capacities for Limit State 1 high-modulus CFRP sheets and resins are more suitable options than the low-modulus sheets and resins. Finally, the study proposes the optimal repair method for damaged composite girder considering the Limit States. • Parametric analyses of damage repaired steel-concrete composite girder were conducted using CFRP sheets. • Effect of various parameters has been investigated. • Equations for loadcapacities of repaired composite girders for Limit States 1, 2 and 3 have been proposed. [ABSTRACT FROM AUTHOR]

The current design philosophy for submarine hulls, in the preliminary design stage, generally considers as governing limit states material yielding along with various buckling modes. It is common belief that, beyond the design pressure, material yielding of the shell plating should occur first, eventually followed by local buckling, while global buckling currently retains the highest safety factor. On the other hand, in the aeronautical field, in some cases structural components are designed in such a way that local instability may occur within the design loads, being the phenomena inside the material elastic range and not leading to a significant drop in term of stiffness. This paper is aimed at investigating the structural response beyond a set of selected limit states, using nonlinear FE method adopting different initial imperfection models, to provide the designers with new information useful for calibrating safety factors. It was found that both local and global buckling can be considered as ultimate limit states, with a significant sensitivity towards initial imperfection, while material yielding and tripping buckling of frames show a residual structural capacity. In conclusion, it was found that the occurrence of local buckling leads to similar sudden catastrophic consequences as global buckling, with the ultimate strength capacity highly affected by the initial imperfection shape and amplitude. [ABSTRACT FROM AUTHOR]

The load resistance factor according to the target reliability level was proposed using 16 vertical breakwaters constructed along the coast of Korea. Limit state functions for sliding and overturning limit states were defined. Reliability analysis was performed to obtain the sensitivity of the limit state function to the design variables. The partial safety factors of the design variable were obtained using the sensitivity, and the load resistance factor was calculated in turn. The representative value of load resistance factors was obtained by optimizing the load resistance factors for 16 vertical breakwaters, and it was verified that the breakwater designed using the representative value had a reliability index greater than the target value. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a web‐based and design‐oriented structural health evaluation system (SHES) for long‐span bridges equipped with long‐term structural health monitoring system (SHMS). The key parameters of a long‐span bridge, used in its limit state design, are recollected. The key design parameters cover not only bridge acceleration, displacement, internal force and stress but also wind loading, temperature loading, traffic loading, earthquake excitation, and corrosion. Data analysis methods are applied to the measurement data recorded by SHMS installed in the bridge to obtain its measured/predicted key parameters. Because most design parameters are reliability‐based, data analysis methods therefore include not only statistical analysis, fatigue analysis, corrosion analysis but also extreme value analysis. The design key parameters and the measured/predicted key parameters are then used to evaluate the health status of the bridge in terms of loading, serviceability, safety, and durability. The three statuses of structural health monitoring, that is, normal monitoring, critical monitoring, and inspection initialization, are correspondingly defined as a reference for maintenance and management decision. All of the above are implemented with a series of web‐based software. The feasibility and advantage of the proposed SHES are finally demonstrated through a case study using a real long‐span butterfly arch bridge. [ABSTRACT FROM AUTHOR]

The European standards, developed extensively over last 30 years, are driven by the need for continuous evolution and their Authors’ pursuit of better EU-wide quality in civil engineering – combining safety, economy, and sustainable development. The adoption of theory of reliability as the basis for design has played a major role in shaping current geotechnical practice. However, it requires from practitioners a greater understanding of underlying uncertainties. Furthermore, a number of alternative approaches, not generally used in structural design, are also allowed, as some situations in geotechnical engineering require an individual approach. Moreover, the current trends in geoengineering increase the importance of risk assessment and management. The paper presents general philosophy guiding the geotechnical design and pointing to some of the ideas introduced by Eurocode 7 and its requirements, in relation to preexisting practice of geotechnical design in civil engineering.

In slope engineering, the allowable safety factor design (ASFD) is widely used. However, it includes all sources of uncertainties and does not truly account for risk. Therefore, a more robust design method is required. This study compares the actual reliability levels that ASFD, PFD (partial factor design), and BTD (baseline technique design) provide. The results indicate BTD provides the most stable reliability levels. The major findings are as follows. (1) A sampling strategy is provided to evaluate the performance that ASFD, PFD, and BTD achieve specific target reliability indexes. It provides reliability-based calibration and evaluation. (2) BTD provides more stable reliability levels, especially when the target reliability index is high. (3) The performance of PFD is influenced by the selection of quantile; BTD uses optimal quantiles and achieves the most stable reliability levels. This study provides a numerical investigation of design factors for shear strength parameters, and it uses a sampling strategy considering typical soils from sand to clay. Preliminary results show that BTD is attractive in numerical aspects. [ABSTRACT FROM AUTHOR]

The load resistance factor according to the target reliability level was proposed using 16 vertical breakwaters constructed along the coast of Korea. Limit state functions for sliding and overturning limit states were defined. Reliability analysis was performed to obtain the sensitivity of the limit state function to the design variables. The partial safety factors of the design variable were obtained using the sensitivity, and the load resistance factor was calculated in turn. The representative value of load resistance factors was obtained by optimizing the load resistance factors for 16 vertical breakwaters, and it was verified that the breakwater designed using the representative value had a reliability index greater than the target value.

Bridges are the most important component of transportation system of any country due to their ability of accelerating the development of the nation. Design of bridge highly depends on its function, nature of soil strata where it is constructed and the material used to construct it. Extensive growth of population and traffic leads to many changes in the use and development of different types of bridges. Box and T-beam girders are most commonly used superstructure in case of bridges. In this research work, analysis and design of box and T beam girder has been performed using SAP2000 in order to find out the most suitable type of bridge superstructure. The main objective of this study is to compare the structural behavior, optimization of materials used in each component and cost comparison of box and T beam girder bridge. Previous research in this regard is based upon working stress method but this research follows limit state design. Detailed comparison shows that box girder is more suitable as compared to T beam girder even for shorter span in terms of structural stability and cost efficiency. [ABSTRACT FROM AUTHOR]

For a long time, the framework of geotechnical design in Egypt has been based mainly on Working Stress Design (WSD) philosophy with the global safety concept as presented in the current version of the Egyptian Code of Practice for Soil Mechanics and Foundations Design and Construction [1]. This design philosophy is supported by long-term experience, considering local experiences and is adopted to fulfill the required safety margin. Limit State Design (LSD) philosophy, on the other side, has already been applied for the design of reinforced concrete structures as introduced in the Egyptian Code of Practice for the Design and Construction of Reinforced Concrete Structures [2]. Applying LSD for superstructure and WSD for foundations often results in design misleading because of the incompatibility between the two design philosophies. Accordingly, implementation of LSD philosophy for geotechnical designs in Egypt has become mandatory and the transition to this new design philosophy of LSD should be as smooth and gradual as possible to allow for a better acceptance by the Egyptian geotechnical community. LSD philosophy using partial safety factors has been applied worldwide using two different approaches; factored strength approach and factored resistance approach. During this study, resistance reduction factors are calibrated on the basis of calibration-by-fitting technique, to be used with factored resistance approach for axially loaded single piles. The calibrated resistance reduction factors from this study are found to be relatively consistent with those values adopted in other geotechnical design codes worldwide.

This paper presents a general procedure for evaluating a proper target reliability index and corresponding wind load factor for a wind load-governed limit state in reliability-based design codes. The Monte-Carlo simulation is conducted to reveal relationships between statistical parameters of wind velocity and pressure. The normalized wind pressure is defined and used in the simulations. The analytical form of the wind load factor is presented in terms of the statistical parameters of wind velocity and the target reliability index. The return period of a nominal wind velocity is expressed for the target reliability index and the wind load factor. An approach determining the target reliability index based on the return period of wind velocity at the limit state is proposed. The return period of wind velocity at the limit state is set to that of the design earthquake in a design code. The proposed approach is applied to calculate the target reliability index for the Korean Highway Bridge Design Code-Cable supported Bridge. The target reliability index is found as 2.25, and the corresponding wind load factor ranges from 1.60 to 1.82 depending on the Coefficient of Variation (COV) of wind velocity. Detailed discussions on the return period of wind velocity, target reliability index and wind load factor are made. A simplified expression of the wind load factor corresponding to the target reliability of 2.25 is proposed. The basic wind velocities for five regions in the Korean Highway Bridge Design Code (Limit State Design) are estimated through the proposed procedure. [ABSTRACT FROM AUTHOR]

The European standards, developed extensively over last 30 years, are driven by the need for continuous evolution and their Authors' pursuit of better EU-wide quality in civil engineering - combining safety, economy, and sustainable development. The adoption of theory of reliability as the basis for design has played a major role in shaping current geotechnical practice. However, it requires from practitioners a greater understanding of underlying uncertainties. Furthermore, a number of alternative approaches, not generally used in structural design, are also allowed, as some situations in geotechnical engineering require an individual approach. Moreover, the current trends in geoengineering increase the importance of risk assessment and management. The paper presents general philosophy guiding the geotechnical design and pointing to some of the ideas introduced by Eurocode 7 and its requirements, in relation to preexisting practice of geotechnical design in civil engineering. [ABSTRACT FROM AUTHOR]

Abstract Sea ice poses hazards to ships and offshore structures which create challenges for designers. Designers have to take into account the ice actions resulting from the various ice conditions, interactions and operational scenarios which may occur during the lifetime of structures. In this paper the methodologies used in ship and offshore structure standards, such as the Finnish Swedish Ice Class Rules, International Association of Classification Societies Polar Class rules and ISO 19906, are considered with respect to Limit State Design principles and design air temperature definitions. The paper presents an overview of the design approach used in these standards and especially the criteria for the structural limit used. Case study examples based on ship measurements in the Baltic, as well as design air temperature data from the Russian Arctic, are used to highlight the different approaches and their implementation. The analysis shows clearly that explicit design ice action and structural limit are required for the rational basis in the future development of Limit State definitions in standards accounting for ice actions. Highlights • The methodologies used in ship and offshore structure standards are considered with respect to Limit State Design principles and design air temperature definitions. • Overview of the design approach used and especially the criteria for the structural limit. • Case study examples based on ship measurements in the Baltic, as well as design air temperature data from the Russian Arctic. • Explicit design ice action and structural limit are required for the rational basis in the future development in standards accounting for ice actions. [ABSTRACT FROM AUTHOR]

With the growing demands on limit state design in engineering practices, the reliability index approach (RIA) has been widely used because it is simple and convenient. However, the RIA using a norm function cannot distinguish the negative reliability index, though it is based on the same concept with the HLRF method. Focusing on this issue, a finding from the HLRF concerning negative reliability indices is presented, and accordingly the sign of RIA is resolved. And then a supplement to the RIA is formed with a suggested formula of sensitivity factors for both positive and negative cases. Two nonlinear examples illustrating negative reliability problems are presented, which validates that the proposed supplement can ascertain negative cases whereas the conventional RIA could not. Additionally, results of sensitivity factors agree well with the proposed formula. Furthermore, the proposed supplement is applied to address tunnel reliability problems including assessment and design. Results reveal that the conventional RIA cannot get the real sign of reliability indices and could mislead search directions of the RBD, which would lead to dangerous decisions. Fortunately, the proposed supplement can help to make correct decisions and thus it can facilitate the application of RIA in the limit state design. [ABSTRACT FROM AUTHOR]

Article presents the analysis of classical and structural ways of fastening of the glass unit subjected to uniformly distributed wind load under the various conditions: modification of the fixing step in horizontal and vertical direction, change of gas-filled gap and glass panel thicknesses. Calculation is performed in FEM-based SJ Mepla software for three most common types of glass units of the size of 1200×1200 mm, 2400×1200 mm and 3600×1200 mm. On the basis of obtained results, it is possible to conclude that modification of the fixing step in horizontal direction and glass panel thickness have a significant influence on the stress and deformation values; in contradistinction, modification in vertical direction and gas filling thickness do not noticeably impact stress-strain state of a plate. Default fixing step between two adjacent supports, which is often adopted by manufactures of IGUs without preliminary calculation for actual applied load, has to be verified in each case in terms of deformation in order to satisfy the conditions of SLS. The table of recommended values of maximum distance between supports is presented.