Allowable Stress Design Method Research Articles

Structural Study of Steel‐Concrete Double Composite Girder Bridge

AbstractIn Japan, the steel‐concrete composite girder bridge is widely used to reduce construction and maintenance cost, and improve constructability and the construction period. As an effort to decrease box girder construction cost, the narrow box girder bridge, which has a reduced box girder width, has been developed. Compared with a conventional box girder bridge, this type of box girder bridge simplifies the structure inside the box by narrowing the space between web plates. Furthermore, it is possible to reduce the number of members, welding length and painting area. The average economical span length is approximately 90m. Similarly, in European countries, a new type of composite girder bridge was developed and constructed for the same purpose as the bridge in Japan. The steel‐concrete double composite girder bridge, which has two concrete slabs on the upper and lower surfaces of the girder only in the region of the intermediate supports, is a type of medium span bridge. An advantage of adopting this structural system is that the cross sections of both the sagging and hogging bending moment areas are classified into the compact section at the ultimate limit state; that is, the maximum flexural strength of these sections can be taken full plastic moment. There are few constructed examples of this type of bridge in Japan. Because of the handling difficulty, the shop manufacturing cost of a box girder is, generally, more expensive than that of an I‐girder. Additionally, the design method for bridges has been revised since January 2018 and has changed from the allowable stress design method to the limit state design method in Japan. Therefore, the authors propose a new type of steel‐concrete double composite I‐girder bridge. The trial design of three‐span continuous girder bridges was conducted. In this paper, the effect of double composite action, for instance, the reduction of the girder height in the region of the intermediate supports, and applicable span length are discussed.

Local and distortional buckling behaviour of back-to-back built-up aluminium alloy channel section columns

The use of aluminium alloy channel sections is becoming popular in lightweight structures, especially for pillars of curtain wall systems and brace and chord members in roof trusses. In cases where increased axial strength is required, it is popular to use built-up sections, instead of single channel sections. Back-to-back built-up aluminium alloy channel sections as compression members can be used to achieve higher strengths and longer spanning capabilities. In such an arrangement, intermediate fasteners at discrete points along the length can prevent the individual channel sections from buckling independently. However, no investigative research is available on the axial strength of back-to-back built-up aluminium alloy channel sections. This paper presents both experimental and numerical investigations on the behaviour of screw fastened back-to-back built-up aluminium alloy stub columns under compression. In total, the results from 15 axial compression tests are reported. For all test specimens, initial imperfections were measured using a laser scanner. A nonlinear elasto-plastic finite element (FE) model was then developed and validated against the test results. Thereafter, a comprehensive parametric study was conducted using the validated FE model to investigate the effects of modified slenderness, screw number and section thickness on axial strength of back-to-back built-up aluminium alloy channel sections. In total, 232 FE models were analysed. Axial strengths obtained from the tests and FEA were used to assess the performance of current design guidelines offered by the Aluminium Design Manual (ADM), Australian/New Zealand Standards (AS/NZS), Eurocode 9 (EC9), Eurocode3 (EC3) and the American Iron and Steel Institute (AISI) standards. It is shown that the design, in accordance with these standards, is conservative within 20%, with the exception of the allowable stress design method mentioned in AS/NZS (1664.2:1997). The ADM, and AISI & AS/NZS (4600:2018) provide highly accurate predictions; being conservative to the experimental results by 6% and 10% on average, respectively.

Seismic Performance Evaluation of Steel Moment-Resisting Frames Designed According to 3rd and 4th Editions of 2800 Seismic Code

Current design codes have prepared linear analysis methods instead of nonlinear ones in order to reduce time, cost and other factors such as less need of these methods for expert knowledge. In linear analysis method, elastic strength demand of structure is decreased by applying a response modification factor called behavior factor (R) and by considering the design code regulations, structure members will be permitted to experience nonlinear response (in the time of middle-to-severe earthquakes). Because of different assumptions for linear (force-based method that has deficiencies) and nonlinear methods and whereas seismic stability or instability is not merely related to the strength of structure, rather it depends largely on the capability of structure to resist drifts, seismic performance evaluation of structures designed by linear procedure appears to be necessary using standards for evaluation. In this research, seismic performance of steel moment frames once designed based on 3rd edition of 2800-Iranian seismic code and allowable stress design (ASD) method and another time based on new ones, the 4th edition of 2800 seismic code and load and resistance factor design (LRFD) method, are compared with each other through nonlinear pushover and time-history analyses according to ASCE/SEI 41–13. Results showed positive change of design codes procedure with respect to alteration of design method in both types of ductile design, intermediate and special. Since mean of overstrength values and mean of ductility values have increased a little, mean of behavior factor values has become closer to the recommended values of the new seismic code. Also, a small number of structures met total collapse during nonlinear time-history analyses.

A Study on Load-carrying Capacity Design Criteria of Jack-up Rigs under Environmental Loading Conditions

Jack-up drilling rigs are widely used in the offshore oil and gas exploration industry. Although originally designed for use in shallow waters, trends in the energy industry have led to a growing demand for their use in deep sea and harsh environmental conditions. To extend the operating range of jack-up units, their design must be based on reliable analysis while eliminating excessive conservatism. In current industrial practice, jack-up drilling rigs are designed using the working(or allowable) stress design (WSD) method. Recently, classifications have been developed for specific regulations based on the load and resistance factor design (LRFD) method, which emphasises the reliability of the methods. This statistical method utilises the concept of limit state design and uses factored loads and resistance factors to account for uncertainly in the loads and computed strength of the leg components in a jack-up drilling rig. The key differences between the LRFD method and the WSD method must be identified to enable appropriate use of the LRFD method for designing jack-up rigs. Therefore, the aim of this study is to compare and quantitatively investigate the differences between actual jack-up lattice leg structures, which are designed by the WSD and LRFD methods, and subject to different environmental load-to-dead-load ratios, thereby delineating the load-to-capacity ratios of rigs designed using theses methods under these different enviromental conditions. The comparative results are significantly advantageous in the leg design of jack-up rigs, and determine that the jack-up rigs designed using the WSD and LRFD methods with UC values differ by approximately 31 % with respect to the API-RP code basis. It can be observed that the LRFD design method is more advantageous to structure optimization compared to the WSD method.

Studi Kekuatan Sambungan Batang Tarik Pelat Baja dengan Alat Sambung Baut

Steel as one of construction materials has several advantages compared to other construction materials. One of the advantages is it can withstand large tensile loads compared to wood and concrete. This research was conducted to find out the strength of the connection of two-faced steel plate tension member with bolts connection through experiment and compare it with theoretical calculations by using Allowable Stress Design (ASD) method. The focused structure is a two-faced connection tension member that is connected using bolts. Steel plated that used in this research are 8 mm and 10 mm thickness with bolt sizes O ¼ , O 3/8 and O ½ , each connection using three bolts as connector. The testing of the tension member connections in the laboratory is carried out by gradually loading the tensile load until the tensile member reaches the ultimate load. The results of experimental and theoretical research found that theoretical calculation of tensile strength smaller than tensile strength done experimentally.

Sensitivity Analysis on Response Modification Factor of New Cable-Cylinder Bracing Systems

ABSTRACTCable bracing systems have been increasingly investigated in recent years. The new cable-cylinder bracing system is made of bracings with two cables and one cylinder. In this system, the cables pass through the cylinder at their crossing region. For the first time in the present research, the overstrength factor, ductility factor, and response modification factor of this bracing system are evaluated using a two-dimensional model. For this purpose, incremental dynamic analyses are conducted on the system using 10 earthquake records. Based on the allowable stress design method, the values 2.33, 1.47, and 4.94 are obtained for the overstrength, ductility, and response modification factors, respectively. The response modification factor of the moment frame with cross-cable bracing is calculated and compared with that of the cable-cylinder bracing. Sensitivity analysis has been conducted on the dimensions of the cylinder, including its length and internal diameter, and pre-stressing stress of cables. According to the obtained results, under low pre-stressing stress, the response modification factor increasesby increasing the length and decreasing the diameter of the cylinder, in other words with increase in . Moreover, the response modification factor decreases with increase in pre-stressing stress of the cables. According to the results obtained from sensitivity analysis, the highest change in the response modification factor with different cylinder lengths, inner diameters of the cylinder, and pre-stressing stresses of the cables is 0.34, 0.377 and 0.612 respectively; i.e. the sensitivity of the response modification factor to the pre-stressing of cables is greater, compared to its sensitivity to the dimensions of the cylinder. Finally, an equation has been presented for calculating the values of response modification factor as per the dimensions of the cylinder and pre-stressing stress of cables.

Sustainability design of concrete structures

AbstractConcrete became the most used material on Earth over 200 years following the invention of modern cement. The design concept has undergone a transition from the allowable stress design method, limit state design method, and to the performance‐based design method, in response to the evolution of materials, sophistication of experimental facilities, and advancement of computation skills. From the issues on resources and energy depletion, global warming, and resilience etc., it is necessary to create a new design framework taking into consideration the required performance beyond the conventional concept, in order to construct infrastructure and buildings in a more rational way. In other words, one should construct a design system which sets the continued existence of the diverse and rich global environment as its most important criterion of value. In this paper, the authors review the design and technology system developed in the past and discusses it based on the above‐mentioned new viewpoint, while constructing and presenting a new design system for concrete structures, focusing mainly on the concept of sustainability which is regarded as the most important in achieving conservation of the Earth's rich resources as well as sound socioeconomic activities of humankind in the future, and discusses its feasibility.

Experimental Study on Tensile and Compressive Strength of Bamboo Scrimber

The objective of this study was to provide fundamental parameters for the utilization of bamboo scrimber in the building structure field as a green building material. Both static tensile and compressive tests were conducted on bamboo scrimber, with 180 specimens for compressive tests and 173 specimens for tensile tests. The normal and lognormal distributions were selected to fit the experimental data. The design values were calculated according to the Chinese allowable stress design method and ASTM D2915 (2003). The results showed that both tensile strength (UTS) and compressive strength (CS) parallel to the fiber of bamboo scrimber were significantly higher than those of wood and other bamboo-based composite materials. Kolmogorov-Smirnov and chi-squared test results indicated that a lognormal distribution was a good fit for the UTS and CS except for the fitting result of UTS by the chi-squared test. The calculated design values of UTS and CS using ASTM D2915 (2003) were higher compared with those found using the Chinese allowable stress design method.

사질토지반 얕은기초의 한계상태설계를 위한 신뢰성 분석

Considering level of reliability prevailed currently, resistance factors for applying the Load Resistance Factors Design method (LRFD) to designing shallow foundation on sandy soil (c = 0, ) were proposed in this paper. To quantify the expected uncertainties of soil properties related to soil parameters and bearing capacity of a shallow foundation on sandy soil ground, data used for design and construction from domestic and abroad was collected and analysis of probability statistics on soil properties was performed. First-Order Reliability Method (FORM) was used to propose the target reliability index for general shear failure of shallow foundation. Estimated values of target reliability index were compared with those obtained from the allowable stress design method, based on the safety factor, being currently used in practices.

Seismic Assessment of Petrochemical Piping Systems Using a Performance-Based Approach

The need of enhanced seismic analysis and design rules for petrochemical piping systems is widely recognized, where the allowable stress design method is still the customary practice. This paper presents an up-to-date performance-based seismic analysis (PBSA) of piping systems. The concept of performance-based analysis is introduced and a link between limit states and earthquake levels is proposed, exemplifying international code prescriptions. A brief review on seismic design criteria of piping systems is then provided by identifying the main critical issues. Finally, the actual application of the performance-based approach is illustrated through nonlinear seismic analyses of two realistic petrochemical piping systems.

Sensitivity Analysis by Parametric Study of Load Factor for a Concrete Box Girder Railway Bridge Using Limit State Design

Reliability based limit state design method is replacing traditional deterministic designs such as allowable stress design and/or ultimate strength design methods in world trends. European design code(Eurocode) has adopted limit state design, and Korea road bridge design standard has also recently been transferred to limit state design method. In this trend, Korea railroad design standard is also preparing for adopting the same design concept. While safety factors are determined empirically in traditional design, load combinations as well as load factors are determined by solving limit state equations. General partial safety factors are evaluated by using AFORM(Advanced First Order Reliability Method) in the reliability based limit state design method. In this study sensitivity analysis is carried out for a dead load factor and a live load factor. Relative precisions of the dead load and the live load factors are discussed prior to the AFORM analysis. Furthermore the sectional forces of design and the material quantities required by two different design methods are compared for a PSC box girder railway bridge.

Response modification factor of suspended zipper braced frames

The suspended zipper bracing system is suggested to reduce the flaws of ordinary zipper braced and concentric inverted <i>V</i> braced frames. In the design procedure of suspended zipper bracing systems, columns and top story truss elements are strengthened. This bracing system show different performances and characteristics compared with inverted <i>V</i> braced and ordinary zipper frames. As a result, a different response modification factor for suspend zipper frames is needed. In this research paper, the response modification factor of suspended zipper frames was obtained using the incremental dynamic analysis. Suspended zipper braced frames with different stories and bay lengths were selected to be representations of the design space. To analyze the frames, a number of models were constructed and calibrated using experimental data. These archetype models were subjected to 44 earthquake records of the FEMA-P695 project data set. The incremental dynamic analysis and elastic dynamic analysis were carried out to determine the yield base shear value and elastic base shear value of archetype models using the OpenSEES software. The seismic response modification factor for each frame was calculated separately and the values of 9.5 and 13.6 were recommended for ultimate limit state and allowable stress design methods, respectively.

Evaluating rating factor for prestressed concrete girder bridges by nonlinear finite element analysis

This study provides a new approach to evaluate the load carrying capacity in rating factor (RF) of prestressed concrete I type girder bridges utilising nonlinear finite element (FE) analysis. RF has been conventionally calculated either by ultimate strength design (USD) or allowable stress design methods in terms of live load effects. This study introduces nonlinear FE analysis as a new approach to estimate the RF. In general, nonlinear FE analysis is considered as one of the most efficient methods to simulate structural behaviour. This method can also simulate a live load effect, which is very important for the load carrying capacity of structures. To apply nonlinear FE analysis, an FE live load constant was conceptually suggested to estimate the RF. On comparing the RF obtained via the conventional method of USD, it was found that the RF estimated by nonlinear FE analysis approach has almost the same value. Hence, the nonlinear finite element method-based RF methodology can be efficiently used to estimate the load carrying capacity of bridges.

대수심 대구경 현장타설말뚝의 지지력에 대한 신뢰성 해석을 이용한 허용응력 설계의 파괴확률 평가 연구

시험 설계된 초장대 사장교의 고주탑을 지지하는 대수심 대형 복합기초의 지중 대구경 현장타설말뚝을 허용응력 설계법으로 설계하고, 지지력에 대한 신뢰성 해석을 통해 파괴확률을 평가하였다. 말뚝의 지지력에 대한 허용응력 설계 결과를 신뢰성 해석으로 분석하였으며 파괴확률은 CFEM의 경우 0.12 %, 한국도로공사기준 방법의 경우 0.0002 %, 구조물기초설계기준의 경우 0.003 %였다. 허용응력 설계에서는 안전율 3을 적용하여 대구경 현장타설말뚝의 허용지지력을 구하였으며, 그 결과에 대한 신뢰성 해석을 실시하였다. AASHTO(2007)에서 제시하고 있는 파괴확률(<TEX>$P_f$</TEX>) 0.02 %일 때 CFEM 방법에서는 근입 깊이가 25 % 만큼 증가하였으며 한국도로공사기준(KHCC)에서는 근입깊이를 60 %, 구조물기초설계기준(SFDC)에서는 근입 깊이를 89 % 만큼 감소시킬 수 있었다. A Large-diameter drilled shaft of deep water depth composite foundation supporting a high rise pylon of the test designed super long span bridge was designed by allowable stress design method and failure probability through reliability analysis to bearing capacity was estimated. The allowable stress design results for the bearing capacity of a drilled shaft were analyzed by reliability analysis and the probability of failure shows 0.12 % in case of CFEM, 0.0002 % in case of Korea Highway Corporation criterion, and 0.003 % in case of structure foundation design criterion. In the allowable stress design, the bearing capacity of a large-diameter drilled shaft was obtained by applying to safety factor 3 and reliability analysis for the results was done. If the failure probability suggested by AASHTO(2007) specification is set to 0.02 %, the socketed length of a drilled shaft shows an increase of 25 % in CFEM, decrease of 60 % in KHCC, and decrease of 89 % in SFDC.

Assessment of vehicular live load and load factors for design of short-span bridges according to the new Egyptian Code

The new Egyptian Code (ECP-201:2012) introduces new vehicular live loads (VLL) and new load combinations for the design of roadway bridges. The new VLL and load combinations introduced in ECP-201:2012 are fundamentally different than those presented in previous versions of the code. The impact of these new loads and load combinations on the design of new bridges or the structural safety of the existing bridges that have been designed according to ECP-201:2003 or ECP-201:1993 has not been fully addressed for the different bridge deck systems. Three different bridge deck systems, i.e. concrete I-shaped girders, composite steel plate girders, and concrete box-girders with different spans were numerically modeled using two-dimensional grillage analogy. The bridge decks were analyzed under main gravity loads using VLL according to ECP-201:2012 and ECP-201:2003. The internal forces of individual load cases, total un-factored load combination, and total factored load combination of ECP-201:2012 and ECP-201:2003 were compared.The study shows that concrete box-girders designed according to ECP-201:2012 and ECP-201:2003 using the ultimate limit state method yield almost the same demand. Despite the increase in the VLL of ECP-201:2012, and consequently the live load forces, concrete I-shaped girder bridges will be subjected to less total factored internal forces in comparison to ECP-201:2003 This is attributed to the interaction between the live to dead loads ratio and the load combinations. Design of composite steel plate girder bridges according to ECP-201:2012 using the allowable stress design method yields over designed sections.

Design Check for the Steel Gusset Plate in Tension Using LRFD Method

This study is mainly intended to examine gusset plate described on the basis of the load resistance factored design (LRFD) method. The determination of design based on the full plastic strength of gusset plate in accordance with the current AASHTO Specifications. The I-40 bridge gusset plates considered herein were designed in accordance with the previous allowable stress design (ASD) method. Therefore, new design methodology will be applied to this gusset plate bridge in this study suggested by new LRFD method. The design strength models to evaluate resistance strength against available failure modes such as tension yielding and block shear rupture are presented. In addition, detailed equations are described with step-by-step procedures. Finally, the rating factor between resistance strength and applied loading, which indicates life safety, will be presented according to available failure modes.

Response modification factor of dual moment-resistant frame with buckling restrained brace (BRB)

Response modification factor is one of the seismic design parameters to consider nonlinear performance of building structures during strong earthquake, in conformity with the point that many seismic design codes led to reduce the loads. In the present paper it's tried to evaluate the response modification factors of dual moment resistant frame with buckling restrained braced (BRB). Since, the response modification factor depends on ductility and overstrength; the nonlinear static analysis, nonlinear dynamic analysis and linear dynamic analysis have been done on building models including multi-floors and different brace configurations (chevron V, invert V, diagonal and X bracing). The response modification factor for each of the BRBF dual systems has been determined separately, and the tentative value of 10.47 has been suggested for allowable stress design method. It is also included that the ductility, overstrength and response modification factors for all of the models were decreased when the height of the building was increased.

Response Modification Factor of Coupled Steel Shear Walls

The present research is concerned with the determination of ductility, over- strength and response modification factors of coupled steel shear wall frames. Three structural models with various numbers of stories, bay width and coupling beam height were analyzed using static pushover and incremental nonlinear dynamic analyses. The ductility, over-strength and response modification factors for the three models are determined. Tentative values of 11.1, 11.6 and 10.6 are suggested for the response modification factor of coupled steel shear wall frames with deep and medium depth coupling beams, and uncoupled steel shear wall frames, respectively in the allowable stress design method.

Development of a new equivalent analysis technique to determine the ultimate load in an electric transmission tower

The current design practice of an electric transmission tower is based on allowable stress design method in Korea. However, it is difficult to find reasons for the collapse of a transmission tower designed with this approach because the collapse tends to occur as a result of secondary large deformations. The main influential factors of nonlinear behavior are residual stresses, initial imperfections, and the end restraints on members. In this study, the necessity of the new analysis technique is examined through a comparison of elastic analysis and inelastic analysis. A new equivalent analytical technique (EAT) is proposed as a means of minimizing the complexity. Furthermore, the reliability of the proposed method is validated by comparing the computed ultimate load of the transmission tower with that of nonlinear finite element analysis.

“DESIGN OF REINFORCED SOIL WALLS BY LRFD APPROACH”

In this paper, the detail of Load and Resistance Factor Design (LRFD) approach which is based on reliability concept for the design of Reinforced Soil (RS) walls is presented. For conventional methods i.e Allowable Stress Design (ASD) Method, the factor of safety is applied only to resistance and loads are considered without variations. For LRFD method, factor of safeties are applied for both load and resistance. Due to availability of large statistical data and economy, this method is preferred. An attempt is made to solve one numerical example of geosynthetic RS walls due to soil selfweight plus permanent uniform surcharge using LRFD as well as other conventional methods (ASD) viz. FHWA, Modified Rankine, NCMA and B.S Code Methods and the results of the LRFD methods are compared with conventional design methods and concluding remarks are presented. The various equations are obtained based on various curves plotted by using ASD and LRFD approaches. From these equations it is clear that if FOS against tensile rupture is known for any RS wall having 7m height and same properties and environmental conditions as mentioned in current study then FOS against pullout failure and pullout capacity can be computed for these walls.