serviceability limit state
Recently Published Documents


TOTAL DOCUMENTS

134
(FIVE YEARS 24)

H-INDEX

13
(FIVE YEARS 1)

Author(s):  
Mohsen Ghabdian ◽  
Seyed BB Aval ◽  
Mohammad Noori ◽  
Wael A Altabey

An important and critical area within the broad domain of structural health monitoring, as related to reinforced civil and mechanical structures, is the assessment of creep, shrinkage, and high-temperature effects on reliability and serviceability. Unfortunately, the monitoring and impact of these inherent mechanical characteristics and behaviors, and subsequent impact on serviceability, have rarely been considered in the literature in structural health monitoring. In this paper, the microprestress-solidification creep theory for beams is generalized for the simultaneous effect of linear/nonlinear creep, shrinkage, and high temperature in a reliability framework. This study conducts a systematic time-dependent procedure for the reliability analysis of structures using a powerful nanoscale method. It must be noted that this paper aims to extend the previously developed microprestress-solidification method in a health monitoring reliability-based framework with a close look at a nonlinear creep, parameters affecting creep, and long-time high temperature. A finite element approach is proposed where creep, shrinkage, temperature, and cracking are considered using strain splitting theory. First, the model performance was evaluated by comparing the results with the experimental test available in the literature in the case of creep and shrinkage. Then, the simultaneous effect of creep, shrinkage, and temperature was compared with experimental results obtained by the authors. Reliability analysis was applied to reinforced concrete beams subjected to sustained gravity loading and uniform temperature history in order to calculate exceedance probability in the serviceability limit state. It was found that the exceedance probability of reinforced concrete beams was dependent on the shear span-to-depth ratio. In the serviceability limit state, exceedance probabilities of 0.012 and 0.157 were calculated for the span-to-depth ratios of 1 and 5, respectively. In addition, it was shown that temperature plays an important role in the reliability of reinforced concrete beams. A 4.27-fold increase was observed in the case of moderate to high temperature. Finally, for three different load levels of 40%, 70%, and 80%, the exceedance probabilities were 0.156, 0.328, and 0.527, respectively, suggesting that load level is another key parameter affecting the reliability of reinforced concrete beams. It is thus concluded these fundamental phenomenological studies should be further considered as part of the broad field of structural health monitoring.


Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5528
Author(s):  
Paweł Zabojszcza ◽  
Urszula Radoń ◽  
Waldemar Szaniec

In this paper, Numpress Explore software, developed at the Institute of Fundamental Technological Research of the Polish Academy of Sciences (IPPT PAN), was used to conduct reliability analyses. For static-strength calculations, the MES3D module, designed by the authors, was employed. Ultimate limit state was defined as condition of non-exceedance of the capacity value, resulting from the stability criterion of the bent and compressed element. The serviceability limit state was defined as the condition of non-exceedance of allowable vertical displacement. The above conditions constitute implicit forms of random variable functions; therefore, it was necessary to build an interface between the Numpress Explore and MES3D programs. In the study, a comparative analysis of two cases was carried out. As regards the first case, all adopted random variables had a normal distribution. The second case involved a more accurate description of the quantities mentioned. A normal distribution can be adopted for the description of, e.g., the randomness in the location of the structure nodes, and also the randomness of the multiplier of permanent loads. In actual systems, the distribution of certain loads deviates substantially from the Gaussian distribution. Consequently, adopting the assumption that the loads have a normal distribution can lead to gross errors in the assessment of structural safety. The distribution of loads resulting from atmospheric conditions is decidedly non-Gaussian in character. The Gumbel distribution was used in this study to describe snow and wind loads. The modulus of elasticity and cross-sectional area were described by means of a log-normal distribution. The adopted random variables were independent. Additionally, based on an analysis of the elasticity index, the random variables most affect the failure probability in the ultimate limit state and serviceability limit state were estimated.


Author(s):  
Rozbeh Moghaddam

This study presents the development and calibration of resistance factors for the serviceability limit state (SLS) condition (φSLS) used in the load and resistance factor design (LRFD) of deep foundations. The performance function was established based on load corresponding to tolerable displacement (Qδtol) and design load (Qd). A dataset of published full-scale load tests including projects from Texas, Missouri, Arkansas, Louisiana, and New Mexico was compiled and consisted of 60 load test cases comprising 33 driven piles and 27 drilled shafts. Resistance factors for SLS conditions were calibrated for tolerable displacements using both the Monte Carlo simulation (MCS) and the First Order Second Moment (FOSM) approaches. From the calibration study, resistance factors at SLS conditions were obtained ranging from 0.33 to 0.62 using FOSM method and 0.37 to 0.67 using the MCS for driven piles. In the case of drilled shafts, SLS resistance factors ranged from 0.37 to 0.77 following the FOSM method and 0.41 to 0.86 based on MCS.


2021 ◽  
pp. 111-136
Author(s):  
Gianluca Ranzi ◽  
Graziano Leoni ◽  
Luigino Dezi ◽  
Alejandro Pérez Caldentey ◽  
John Hewitt ◽  
...  

<p>This chapter deals with the long-term behaviour of composite members and structures used for building and bridge applications and provides a review of the relevant international serviceability limit state design methodologies, with particular focus given to the European, Australian and New Zealand, and American specifications. The first part of the chapter introduces the deflection limit requirements specified in design procedures for satisfying the serviceability limit state conditions. This is followed by a review of the design procedures recommended in the specifications for composite slabs, beams, and columns. Particular attention is devoted to reviewing design methodologies for the calculation of the displacements, for detailing, and for control of concrete cracking.</p>


Author(s):  
Marcela Alejandra Juliani ◽  
Wellison José de Santana Gomes

Abstract Most current structural design codes are based on the concept of limit states, that is, when a structure fails to meet one of its purposes, it is said that it has reached its limit state. In the design of reinforced concrete structures, the Ultimate Limit State (ULS) and the Serviceability Limit State (SLS) must be checked. Therefore, this paper presents an optimization scheme for reinforced concrete plane frames, in which the objective is to minimize the cost of structures for three cases of constraints: the first is related to ULS and SLS; the second refers only to the ULS; and the third is related only to the SLS. Computational routines for checking limit states of beams and columns are implemented in MATLAB, following the requirements of the Brazilian code. Structural analyses are performed by using the MASTAN2 software, taking into account geometric nonlinearities and a simplified physical nonlinearity method. The objective function considers the cost of concrete, reinforcement and formwork, and the optimization problems are solved by genetic algorithms. Two numerical examples of frames are presented. Regarding the optimal characteristics related to each type of limit state, it is noted that the beams and columns tend to have larger and more reinforced cross sections in the case of the ULS. Even so, optimal structures related to the ULS often do not satisfy SLS and vice versa, which indicates that the optimal characteristics related to each limit state may be different. In addition, it is observed that the SLS is less restrictive than ULS.


2021 ◽  
pp. 157-188
Author(s):  
Alejandro Pérez Caldentey ◽  
Luigino Dezi ◽  
Javier Jordán ◽  
Graziano Leoni ◽  
Gianluca Ranzi ◽  
...  

<p>This chapter introduces three case studies that describe how aspects related to the serviceability limit state design associated with the time-dependent behaviour of concrete can be considered in a design situation. The first case study considers the Oxec II Bridge in Guatemala. It provides an overview of the stress verification of the steel section of the composite bridge and accounts for concrete time effects to capture the stress redistribution that occurs between the concrete and the steel components. The second case study deals with the Yalquincha Viaduct in Chile and provides an overview of the type of long-term analyses that can be carried out when considering the influence of different cross-sectional arrangements on the time-dependent response of the bridge. The last case study focusses on the Serra Cazzola Viaduct in Italy and highlights the opportunities available to designers in exploiting optimised casting sequences to reduce the time-dependent stresses induced in the concrete and, therefore, mitigate the likelihood of concrete cracking.</p>


2020 ◽  
pp. 136943322097245
Author(s):  
Yangguang Yuan ◽  
Wanshui Han ◽  
Xin Xu ◽  
Junfeng Wang ◽  
Jianpeng Sun

To increase the authorization efficiency of overloaded customized transport vehicle (CTV), a serviceability limit state (SLS) reliability based permit checking method for concrete bridges is proposed through the optimization towards critical load effect ratio. In this procedure, the SLS reliability of crack width and the SLS reliability of concrete stress in tensile region are analyzed for reinforced concrete (RC) and prestressed concrete (PC) structures, respectively. The durability requirements and a unified reliable level can be concentrated reflected by the optimized critical load effect ratio. The results show that it is unreasonable to take a uniform target reliability index for all routes in permit checking of CTV, a stricter authorization criterion should be adopted for a higher expected authorization frequency. For a specific route level, a fluctuant variation of critical load effect ratio can be found with the increasing of bridge span. By introducing an ultimate limit state (ULS) based safety checking procedure, it is found that the SLS based permit checking criterion is crucial and determinative for the authorization of CTV instead of the ULS.


2020 ◽  
Vol 7 (2) ◽  
pp. 47-52
Author(s):  
Vania Regina Husada ◽  
Ferdian Nathanael ◽  
Doddy Prayogo ◽  
Yudas Tadeus Teddy Susanto

Pondasi adalah bagian dari struktur bangunan yang berfungsi meneruskan beban struktur atas ke lapisan tanah dengan aman. Sementara pondasi dangkal digunakan apabila lapisan tanah keras terletak dekat dengan permukaan tanah. Untuk mendapatkan hasil desain pondasi dangkal yang optimal, terdapat tiga kriteria penting yang harus diperhatikan yaitu Ultimate Limit State (ULS), Serviceability Limit State (SLS), dan ekonomis. Sehingga, penggunaan metode optimasi yang baik akan membantu menghasilkan dimensi pondasi yang optimal dan ekonomis namun tetap memenuhi syarat aman. Penelitian-penelitian sebelumnya mengindikasikan bahwa metode metaheuristik dapat digunakan sebagai alternatif yang mampu menyelesaikan permasalahan optimasi yang ada. Oleh karena itu, penelitian ini menggunakan metode metaheuristik Particle Swarm Optimization (PSO) dan Symbiotic Organisms Search (SOS) untuk menyelesaikan permasalahan optimasi pondasi dangkal. Pada penelitian ini, optimasi pondasi dangkal dilakukan terhadap pondasi setempat untuk studi kasus bangunan dua lantai. PSO dan SOS bekerja untuk menemukan solusi dimensi pondasi setempat yang diharapkan dapat memiliki biaya konstruksi terendah dan dibatasi oleh constraint dari SNI 8460:2017, SNI 2847:2013, dan bearing capacity theory. Hasil penelitian menunjukkan bahwa metode metaheuristik mampu menemukan dimensi pondasi dangkal yang optimal untuk masing-masing studi kasus. Selain itu, dapat dilihat apabila algoritma SOS memiliki performa yang lebih baik dari PSO.


Sign in / Sign up

Export Citation Format

Share Document