Evaluation of NSP and MPA Methods to Optimize Special Truss Moment Frames (STMF) Using Island Genetic Algorithm

The purpose of the present study is to evaluate the Pushover (NSP) and Modal Pushover (MPA) analysis methods in optimizing Special Truss Moment Frames (STMF) using island genetic algorithm. For this purpose, the optimization program is written and developed in Matlab software, and OpenSees software is used for structural analysis. The design variables of truss arrangement, cross section of members, truss height values and length of special zone of truss moment frame are considered. The constraints of the optimization problem are based on the rules and restrictions of AISC341-16. Case studies were performed on five frames of 3, 6, 9, 12 and 15 stories with a story height of 3 meters and span length of 18 meters with the aim of minimizing weight and maximizing the response modification factor. The results of these analyses are compared with nonlinear dynamic time history analyses as the most accurate method available, which could be used to finally identify and introduce the most efficient method in these structures. The MPA method was able to show better performance than the NSP method in estimating the maximum response of the structure. Despite the excellent performance of this method, Evaluation of numerical results of this study indicates the non-economic nature of MPA method for low-rise structures, and the acceptable efficiency of this method for medium-height to high-rise structures.

Analytical investigation of the seismic performance of special truss girder framing systems with new technologies

Αντικείμενο της Διατριβής αποτελεί η αναλυτική διερεύνηση της δυνατότητας βελτίωσης της αντισεισμικής συμπεριφοράς ειδικών δικτυωτών πλαισιακών συστημάτων (Special Truss Moment Frames, STMFs, από χάλυβα) μέσω της ενσωμάτωσης ράβδων κυκλικής διατομής από κράματα νικελίου-τιτανίου (μνήμης μορφής – shape memory alloy bars), οι οποίες αποτελούν εναλλακτικό σύστημα απορρόφησης της σεισμικής ενέργειας στο ειδικό τμήμα (special segment) των πλαισίων. Τούτο καθόσον διαθέτουν την δυνατότητα να ανακτήσουν την αρχική τους (απαραμόρφωτη) γεωμετρία μετά από μηχανική διαταραχή κατά την αποφόρτιση, μέσω του μετασχηματισμού φάσης των κρυσταλλικών δομών (ματερνσιτικής – ωστενιτικής). Ο επικρατών αντισεισμικός σχεδιασμός των STMFs με ειδικό μέρος ευρισκόμενο στο μέσο του ανοίγματος τους (με σκοπό την απορρόφηση σεισμικής ενέργειας) είναι η δημιουργία πλαστικών αρθρώσεων στις τέσσερεις γωνίες. Αυτός ο μηχανισμός προτείνεται να αντικατασταθεί μέσω της παραμόρφωσης των SMAs σε ένα ειδικό μέρος με αρθρώσεις στις κορυφές του. Τονίζεται ότι οι ράβδοι SMA θεωρούνται σε όλες τις αναλύσεις της Διατριβής ως μη λυγηρές, είτε λόγω μεγάλης διατομής είτε λόγω ενίσχυσης μέσω συστημάτων αποφυγής λυγισμού.

STUDI PERBANDINGAN PERENCANAAN BANGUNAN BAJA SISTEM SPECIAL MOMENT FRAMES DAN SPECIAL PLATE SHEAR WALLS

Indonesia merupakan wilayah rawan gempa, sehingga konstruksi bangunan memakai sistem penahan gaya seismik dianggap penting. Umumnya, struktur bangunan adalah beton bertulang, adapun baja penggunaan sistem special moment frames (SMF) lebih banyak dijumpai sebagai sistem penahan gaya seismik. Padahal menurut peraturan ASCE/SEI 7-10 terdapat pilihan sistem penahan gaya seismik untuk bangunan baja seperti special plate shear walls (SPSW), special truss moment frames (STMF) dan sistem khususnya lainnya. Studi ini akan memperlihatkan perbandingan perencanaan bangunan sistem SMF dan SPSW dalam mempelajari potensi penggunaan kedua sistem ini di Indonesia. Konfigurasi bentang antar kolom dipilih agar menghasilkan variasi desain bangunan sistem SMF sehingga menghasilkan struktur yang ekonomis. Dari hasil studi perbandingan perencanaan, diketahui jika konfigurasi struktur bangunan dengan panjang bentang antar kolom yang pendek, maka sistem SMF lebih ekonomis bila dibandingkan terhadap sistem SPSW. Akan tetapi, untuk panjang bentang antar kolom yang besar penggunaan sistem SPSW dapat menjadi alternatif. Indonesia is located in earthquake risk area, thus the construction of seismic resisting structures is important. In general, reinforcement concrete is used for the structural of buildings, while the use of steel material, special moment frames (SMF) is more commonly used as a seismic force-resistant frame system. According to the standard provision of ASCE/SEI 7-10, the seismic resisting systems for steel buildings are special plate shear walls (SPSW), special truss moment frames (STMF) and other specialized systems. This paper will present analytical models of SMF and SPSW, which is studied further to determine the potential use in Indonesia. To overcome this, parametric study is used to develop design variations with the SMF system cases on different column distance designed to find the most economical structure. The results of comparative design study shown that the SMF system is suitable to be applied for the columns distance with short span and verified to be more economical. However, for long span of columns distance the use of SPSW system can be an alternative.

STUDI PERBANDINGAN PERENCANAAN BANGUNAN BAJA SISTEM SPECIAL MOMENT FRAMES DAN SPECIAL PLATE SHEAR WALLS

Indonesia merupakan wilayah rawan gempa, sehingga konstruksi bangunan memakai sistem penahan gaya seismik dianggap penting. Umumnya, struktur bangunan adalah beton bertulang, adapun baja penggunaan sistem special moment frames (SMF) lebih banyak dijumpai sebagai sistem penahan gaya seismik. Padahal menurut peraturan ASCE/SEI 7-10 terdapat pilihan sistem penahan gaya seismik untuk bangunan baja seperti special plate shear walls (SPSW), special truss moment frames (STMF) dan sistem khususnya lainnya. Studi ini akan memperlihatkan perbandingan perencanaan bangunan sistem SMF dan SPSW dalam mempelajari potensi penggunaan kedua sistem ini di Indonesia. Konfigurasi bentang antar kolom dipilih agar menghasilkan variasi desain bangunan sistem SMF sehingga menghasilkan struktur yang ekonomis. Dari hasil studi perbandingan perencanaan, diketahui bahwa konfigurasi struktur bangunan dengan panjang bentang antar kolom yang pendek, maka sistem SMF lebih ekonomis bila dibandingkan terhadap sistem SPSW. Akan tetapi, untuk panjang bentang antar kolom yang besar penggunaan sistem SPSW dapat menjadi alternatif.Kata kunci: gempa, special moment frames, special plate shear walls

Effect of Special Segment Aspect Ratio on Seismic Performance of Special Truss Moment Frames (STMFs)

Special Truss Moment Frame (STMF), a relatively new type of seismic force resisting system dissipates energy through plastic hinge formation in a well-defined region known as special segment. The aspect ratio of special segment plays an important role during dissipation of energy in terms of moment and rotation developed at the end of special segment. Higher aspect ratio lowers the rotational demand while lower aspect ratio increases the rotational demand at the end of special segment. ANSI/AISC 341 specifies that aspect ratio of any panel shall not exceed 1.5 nor be less than 0.67 in the special segment. This paper presents an investigation on the effect of aspect ratio of special segment during seismic event and explore the possibility of higher aspect ratio. The investigation is carried out using FEMA P695 involving nonlinear static as well as dynamic analyses based on collapse probability. In this paper the variation of aspect ratio is taken as 1, 1.5, 2, 2.5 and 3 considering 9-story comprised perimeter STMF with five bays having 150 ft. by 150 ft. in plan. For carrying out nonlinear analysis all the archetypes were modelled in a nonlinear analysis software Perform-3D. The evaluation of collapse carried out by performing incremental dynamic analysis (IDA) using scaled ground motion based on total collapse uncertainty as per FEMA P695.