Effect of Building Configuration on Overstrength Factor and Ductility Factor

It is important for the structure to be economical and still have a high level of life safety. The lateral force sustained by the structures during a large earthquake would be several times larger than the lateral force for which the structures are designed. This is opposite to the fact that design loads such as gravity in codes are usually higher than the actual anticipated load. It is based on the probability that the occurrence of large earthquakes is quite rare and the capacity of the structure to absorb energy. The co-factors of response reduction factor which is the overstrength factor and ductility factor reduce the design horizontal base shear coefficient. A total of 36 low-rise residential buildings having different storey, bay and bay lengths are selected and analysed in this paper. NBC 105: 2020 is selected for the seismic design of RC buildings while provision provided in FEMA 356:2000 is used to carry out non-linear pushover analysis. The results indicated that between the different structures, the value of overstrength factor and ductility factor has a high deviation.

EVALUASI KINERJA STRUKTUR DUAL SYSTEM DENGAN BELT TRUSS

In structural engineering applications, the limit of building deflection or interstory drift is an important issue. In high-rise buildings that are more than or equal to 60 floors in the current era, systems are used in the structure of the building. The function of the Belt Truss is to reduce the deflection that occurs in the building by converting the building's overturning moment into the axial force of the exterior column. The Belt Truss structure itself can use reinforced concrete structures and steel structures. Because the Belt Truss structure is an innovation in the world of structural engineering, the parameter values for earthquake loads are not listed in the applicable Building Planning Standards. The standard for earthquake-resistant building regulations requires the parameters of Response Modification Factor (R), Overstrength Factor (Ωo), and Deflection Magnification (Cd) for determining earthquake loads. Because the parameters on the Belt Truss structure are not listed in the Standard for Earthquake Resistant Building Regulations, a study of the earthquake load parameters on the Belt Truss structure was carried out. The method used in this research is a literature study using Pushover Load Analysis according to ATC - 40 and FEMA 356. Keywords: Belt Truss, Dual System; ATC – 40; FEMA 356; Response Modification Factor (R); Overstrength Factor (Ωo); and Deflection Magnification (Cd) AbstrakDalam aplikasi rekayasa struktur gedung, batasan defleksi bangunan atau interstory drift adalah masalah penting. Pada bangunan tinggi yang lebih dari atau sama dengan 60 lantai pada era sekarang sudah menggunakan sistem pada struktur bangunan tersebut. Fungsi dari Belt Truss tersebut berguna untuk mengurangi defleksi yang terjadi pada bangunan dengan mengkonvesi momen guling bangunan menjadi gaya aksial kolom eksterior. Struktur Belt Truss sendiri materialnya bisa menggunakan struktur beton bertulang dan struktur baja. Karena struktur Belt Truss merupakan inovasi pada dunia rekayasa struktur, maka nilai parameter beban gempa tidak tercantum pada Standar Peraturan Perencanaan Bangunan yang berlaku. Standart Peraturan Bangunan tahan gempa diperlukan parameter – parameter Faktor Modifikasi Respon (R), Faktor Kuat Lebih (Ωo), dan Perbesaran Defleksi (Cd) untuk penentuan beban gempa. Dikarenakan parameter pada struktur Belt Truss tidak tercantum pada Standar Peraturan Bangunan Tahan Gempa, maka dilakukan penelitian parameter-parameter beban gempa pada struktur Belt Truss tersebut. Metode yang digunakan dalam penelitian ini adalah studi literatur dengan menggunakan analisa Beban Dorong Pushover Analysis sesuai ATC - 40 dan FEMA 356.

LOOP ALGORITHMS FOR DUCTILITY ANALYSIS OF COLUMN REINFORCED STEEL WITH YIELD STRENGTH ABOVE 500 MPA

There are many benefits to the use of high-strength reinforcement (above 500 MPa) in reinforced concrete buildings. The advantages of using high-strength reinforcement are reduction steel volume and dimension, reduced construction time, reduction in reinforcement congestion, as well as savings in materials and worker cost. Meanwhile, the investigation of ductility of reinforced concrete element with high-strength reinforcement to resist earthquake effects under current design procedure is needed. In the current standard, ACI 318-71, The maximum specified yield strength was restricted to 60 Ksi (413 MPa) for reinforcement in special seismic system. There were also no ASTM standard specifications for reinforcement with yield strength above 500 MPa. In the design of seismicresisting structures, the analysis of curavture ductility and flexural overstrength factor is of important consideration in order to avoid brittle failure. This paper attempts to anaylze the ductility and re-evaluate the flexural overstrength factor of reinforced concrete column. The tensile tests of steel reinforcement with yield strength above 500 MPa generates stress-strain curve. An idealisations for the monotonic stress-strain curve proposed by mander wasadopted in this study. Whereas in this numerical study of confined concrete columns, the behavior of concrete cored is modeled by the stress-strain relationship of confined concrete proposed by Kappos-Konstantinidis. This stress strain model was used for the momen, curvature, ductility, and flexural overstrength factor analysis.

Seismic Behavior of Concentrically Braced Steel Frames with Out-of-Plane Offset Irregularity

Braced steel frames are sometimes designed with out-of-plane shifted bracing members on the first story due to architectural or functional considerations. Such frames are classified and designated as frames having the Type-4 horizontal structural irregularity entitled “frames with out-of-plane offset irregularity” as per theMinimum Design Loads for Building and Other Structures(ASCE 7-10). The purpose of this study is to investigate the nonlinear seismic behavior of ordinary steel concentrically braced frames with out-of-plane offset irregularity and evaluate their seismic design parameters. To this end, two 3-story and 6-story three-dimensional ordinary concentrically braced frames (OCBFs) with and without out-of-plane offset of one of the vertical elements on the first story were considered (i.e. irregular and regular configurations). The seismic design parameters considered in this study includes: frame overall overstrength factor, column overstrength factor and the inelastic dynamic inter-story drift demands. Nonlinear time-history dynamic analysis of the frames showed that overall overstrength factor of the low- and mid-rise irregular frames studied in this research is lower than that of the regular ones. Moreover, it was found that theSeismic Provisionsprescribed overstrength factor (i.e. Ωo=2.0) to amplify columns axial seismic forces in OCBFs is not conservative for the studied regular frames’ columns as well as the columns in the vicinity of the shifted bracing members on the first story of the irregular frames. Also, it was shown that the studied low- and mid-rise regular and irregular concentrically braced frames experience greater inter-story drift demands than predicted by the amplified elastic analysis proposed in the codes.