Calibration of Load and Resistance Factors for Breakwater Foundation Design. Application on Different Types of Superstructures

Load and resistance factor design is an efficient design approach that provides a system of consistent design solutions. This study aims to determine the load and resistance factors needed for the design of breakwater foundations within a probabilistic framework. In the study, four typical types of Korean breakwaters, namely, rubble mound breakwaters, vertical composite caisson breakwaters, perforated caisson breakwaters, and horizontal composite breakwaters, are investigated. The bearing capacity of breakwater foundations under wave loading conditions is thoroughly examined. Two levels of the target reliability index (RI) of 2.5 and 3.0 are selected to implement the load and resistance factors calibration using Monte Carlo simulations with 100,000 cycles. The normalized resistance factors are found to be lower for the higher target RI as expected. Their ranges are from 0.668 to 0.687 for the target RI of 2.5 and from 0.576 to 0.634 for the target RI of 3.0.

Improved Calculation of Load and Resistance Factors Based on Third-Moment Method

Load and resistance factor design (LRFD) is widely used in building codes for reliability design. In the calculation of load and resistance factors, the third-moment method (3M) has been proposed to overcome the shortcomings (e.g., inevitable iterative computation, requirement of probability density functions (PDFs) of random variables) of other methods. With the existing 3M method, the iterative is simplified to one computation, and the PDFs of random variables are not required. In this paper, the computation of load and resistance factors is further simplified to no iterations. Furthermore, the accuracy of the proposed method is proved to be higher than the existing 3M methods. Additionally, with the proposed method, the limitations regarding applicable range in the existing 3M methods are avoided. With several examples, the comparison of the existing 3M method, the ASCE method, the Mori method, and the proposed method is given. The results show that the proposed method is accurate, simple, safe, and saves material.

Reliability-Based Design of Driven Piles Considering Setup Effects

The total ultimate resistance (or bearing capacity) of driven piles considering setup effects is composed of initial ultimate resistance and setup resistance, and the setup effects of driven piles are mainly reflected by the setup resistance. In literature, a logarithmic empirical formula is generally used to quantify the setup effects of driven piles. This paper proposes an increase factor (Msetup) to modify the resistance factor and factor of safety calculation formula in accordance with the load and resistance factor design (LFRD) principle; here, the increase factor is defined as the ratio of the setup resistance (Rsetup) to the initial ultimate resistance (R0) of driven piles. Meanwhile, the correlation between R0 and Rsetup is fully considered in the resistance factor and factor of safety calculation. Finally, the influence of four key parameters (ratio of dead load to live load ρ = QD/QL, target reliability index βT, Msetup, correlation coefficient between R0 and Rsetup, ρR0,Rsetup) on the resistance factor and factor of safety are analyzed. Parametric research shows that ρ has basically no effect on the resistance factor, which can be taken as a constant in further research, and ρ has a significant influence on the factor of safety. The value of Msetup has almost no effect on the resistance factor and factor of safety. However, βT and ρR0,Rsetup have a significant influence on the resistance factor and factor of safety, so the value selection of βT and ρR0,Rsetup are crucial for reliability-based design of driven piles. Through this study, it is concluded that considering setup effects in reliability-based design of driven piles will greatly improve the prediction for design capacity.

Safe Platooning Headways on Girder Bridges

Truck platooning—digitally linking two or more trucks to travel in a closely spaced convoy—is an emerging technology with the potential to save fuel and reduce labor. A framework is described to determine how much a platoon permit load might be increased above Federal Bridge Formula B legal limits, given strict control over the load characteristics and operational tactics. Soon, platoons are expected to advance not only with respect to traffic operations but also in their ability to weigh and report axle weight and spacing, functioning as mobile weigh-in-motion vehicles. Consequently, platoon live load statistics (bias and coefficient of variation) can differ from code assumptions, and are perhaps controllable, which poses a significant opportunity with respect to operational strategies. A parametric study is presented that examined safe headways between platooning trucks, considering different girder spacings, span lengths, numbers of spans, types of structure, truck configurations, numbers of trucks, and adjacent lane loading scenarios. The Strength I limit state was evaluated for steel and prestressed concrete I-girder bridges optimally designed using load and resistance factor design. Reliability indices, β, were calculated for each load case based on Monte Carlo simulation. Summary headway guidance was developed and is presented here to illustrate potential safe operational strategies for varying truck weights and platoon live load effect uncertainties.

Case Study of Supplemental Steel Structures

Supplementary steel provides essential connections between building steel or ground to pipe supports and component supports of power and processing plants. This type of structure is usually with steel members less than 10 feet in length and sustains temperature within the range of the ambient conditions and the pipe or component. Being a connection, the standards and Codes provide an array of stress and geometrical checks that share that of a building and of a pressure boundary. Therefore, the applied engineering mechanics utilized in the analysis of supplemental steel configurations, including but not limited to beams, columns, and frames along with their welded or bolted connections, stretches across multiple engineering disciplines. A study of load cases and load case combinations is performed across multiple configurations of assemblies with industry assumptions incorporated. With the mitigation of sag of pipe systems, study of analytical stress and geometrical checks are evaluated to find any correlations of governing criteria. Additionally, the utilization of two types of structural steel design fundamentals and provisions, Allowable Strength Design (ASD) and Load and Resistance Factor Design (LRFD), are investigated with supplemental steel structures which stem from design considerations of steel buildings. This case study in the analysis of supplemental steel structures provides segue to highlighting how Codes and Standards utilized within the field that overlap other fields.

Efisiensi Penggunaan Dimensi Balok Wide Flange (WF) terhadap Kekakuan Struktur Gedung BPJN Aceh dengan Penambahan Elemen Shear Wall

Pengaruh gempa terhadap perilaku struktur bangunan seperti rumah, hotel, rumah sakit, perkantoran dan lainnya sangatlah tinggi. Gempa tentu dapat mengakibatkan kerugian dari segi ekonomi dan dapat mengakibatkan korban jiwa manusia. Semakin tinggi suatu gedung, penggunaan struktur rangka untuk menahan gaya lateral akibat beban gempa menjadi kurang ekonomis karena akan menyebabkan dimensi struktur kolom dan balok akan semakin besar serta jumlah tulangan yang diperlukan juga akan semakin banyak. Gedung utama perkantoran ini memiliki 2 (dua) tower berbentuk lingkaran elips pada lantai dasar dibangun dengan menggunakan material beton bertulang, sedangkan pada lantai 1 (satu) sampai lantai atap dibangun dengan menggunakan material baja. Untuk analisis gaya gempa menggunakan data gempa pada daerah Kota Banda Aceh, Perhitungan pembebanan yang digunakan sesuai dengan data yang diperoleh dari konsultan perencanaan. Faktor lain yang ditinjau adalah perpindahan dan gaya terhadap gedung sebelum dan sesudah ditambahkan shear wall pada struktur bagian tengah gedung. Analisa struktur menggunakan program SAP 2000 berlisensi. Penelitian struktur baja ini sendiri menggunakan peraturan SNI 1729 – 2015 tentang Tata Cara Perencanaan Struktur Baja untuk Bangunan Gedung yang mengadopsi peraturan Load and Resistance Factor Design (LRFD). Hasil yang diharapkan dalam penelitian ini adalah menganalisis perkuatan struktur gedung yang lebih ekonomis dengan ditambahnya elemen shearwall diantara struktur baja pada gedung yang dianalisa serta tinjauan terhadap kombinasi beban serta mengevaluasi kekakuannya.

ALTERNATIF PERENCANAAN JEMBATAN RANGKA BAJA DENGAN MENGGUNAKAN METODE LRFD DI JEMBATAN GELATIK KOTA SAMARINDA

Jembatan merupakan elemen penting dalam sistem transportasi. Jembatan adalah suatu konstruksi yang menghubungkan dua jalan yang terputus karena adanya jurang, lembah, sungai bahkan menghubungkan antar pulau yang terpisah cukup jauh. Jembatan rangka baja banyak dibangun untuk kepentingan lalu lintas jalan raya. Secara umum jembatan rangka baja lebih menguntungkan daripada jembatan lainnya, karena batang-batang utama rangka baja memikul gaya aksial tekan atau gaya aksial tarik, konstruksi jembatan jauh lebih ringan, bentang jembatan jauh lebih panjang, pelaksanaan dilapangan jauh lebih mudah. Struktur bangunan jembatan rangka baja terdiri atas beberapa bagian batang utama pembentuk rangka yaitu batang gelagar induk, batang gelagar melintang dan memanjang, batang-batang ikatan angin atas dan bawah, ikatan pengaku dan sistem lantai kendaraan yang membentuk suatu konstruksi yang kaku sehingga membentuk jalur lalu lintas yang aman dan nyaman. Tujuan dari penelitian ini adalah merencanakan ulang jembatan Gelatik menggunakan struktur jembatan rangka baja dengan metode Load And Resistance Factor Design (LRFD), dan mengacu pada peraturan Standar Nasional Indonesia (SNI). Profil baja yang digunakan pada perencanaan jembatan ini adalah profil baja WF untuk gelagar memanjang, gelagar melintang, gelagar induk, dan profil L untuk ikatan angin atas dan ikatan angin bawah.