Farhad Darani - Academia.edu (original) (raw)

Papers by Farhad Darani

INTRODUCTION The innovative Resilient Slip Friction Joint (RSFJ) technology has recently been int... more INTRODUCTION The innovative Resilient Slip Friction Joint (RSFJ) technology has recently been introduced to the NZ construction industry. This damage avoidance technology not only provides life safety, but also minimizes the earthquake-induced damage so that the building can be reoccupied quickly. The RSFJ is a friction-based damping device with a special configuration that can produce a flag-shape hysteresis. It provides the required seismic performance regardless of the material used for the main structural components. It can be used in various applications including (but are not limited to) shear walls, tension-compression braces, tension-only braces and moment resisting frames. The philosophy of design is that the inelastic behavior of the structure is provided by the RSFJs and the rest of the structural members remain elastic. This study reports on the latest development of this technology including the analysis and design procedure. RSFJ BRACE AND RSFJ TBRACE As shown in Figur...

The innovative Resilient Slip Friction Joint (RSFJ) technology has recently been developed and in... more The innovative Resilient Slip Friction Joint (RSFJ) technology has recently been developed and introduced to the New Zealand construction industry. The RSFJ is a friction-based energy dissipation device that provides the required seismic performance regardless of the material used for the main structural components. It can be used in various lateral load resisting systems including (but are not limited to) shear walls, rocking columns, tension-compression braces, tension-only braces and moment resisting frames. The performance of the RSFJ technology has previously been verified by joint component testing and full-scale experimental tests. Different design codes around the world have different approaches to determine the design seismic loads yet most of them recommend to reduce the elastic base shear by a factor that is related to the ductility. Most of the codes recommend ductility-related values for different types of conventional structures based on the type of lateral load resisting system and the material used. Nevertheless, there is still lack of information about the seismic design of buildings with more advanced technologies such as RSFJ. This research aims to provide a simple analysis and design procedure for the structural engineers when designing a seismic resilient building with RSFJs. A step-by-step forced-based design procedure is provided that generally requires the use of the Equivalent Static Method (ESM) to specify the structural design actions followed by non-linear static pushover and non-linear dynamic time-history simulations to verify the performance. In this procedure, the designer adopts a force reduction factor at the start and verifies it at the end. A case-study structure that uses RSFJ braces as the lateral load resisting members is considered to explain and follow the proposed design procedure

Structures, 2021

Abstract In recent years, there has been more interest in utilisation of slip friction connectors... more Abstract In recent years, there has been more interest in utilisation of slip friction connectors among researchers, due to their energy dissipation without any yielding of the components. Resilient Slip Friction Joint (RSFJ) is a damage avoidance friction damper in which energy dissipation and self-centring features are provided in one device. This is achieved by controlled friction sliding of especially grooved steel plates which are designed to take the induced tension, bending and shear stresses. In order to perform in accordance with damage avoidance philosophy, the RSFJ plates should remain elastic. Hence, in this paper, the performance of RSFJ components is initially investigated through numerical, analytical and experimental studies. New simplified equivalent spring models are developed in this research for analysis and design of the plates. Also, to prevent the sudden stiffness increase of the joint after locking at its maximum deflection, a new mechanism is introduced and named Anti-Locking Mechanism (ALM). The new ALM is presented and studied experimentally in this research. The ALM is in fact a secondary fuse for the RSFJ in which the clamping bolts elongate providing more ductility for the joint and solving the locking-issue of the damper while the re-centring feature is still preserved without any compromise. Therefore, the RSFJ equipped with ALM could prevent the formation of seismic shocks to the structure during unpredictable seismic events beyond the design level.

Journal of Structural Engineering, 2020

AbstractThe innovative resilient slip friction joint (RSFJ) technology has recently been develope... more AbstractThe innovative resilient slip friction joint (RSFJ) technology has recently been developed and introduced to the construction industry. This technology not only aims to provide life safety ...

Journal of Constructional Steel Research, 2019

The Resilient Slip Friction Joint (RSFJ) has recently been developed and introduced to the constr... more The Resilient Slip Friction Joint (RSFJ) has recently been developed and introduced to the construction industry. This joint is a friction-based energy dissipation device that owing to its special configuration can provide energy absorption and self-centring behaviour in one package. This device is most applicable when the designers consider a damage avoidance philosophy of design. One of the applications of this device is the RSFJ brace. In this bracing system, the required seismic performance is provided by the RSFJ and the rest of the brace components are aimed to stay elastic. This paper introduces the RSFJ bracing system including the collapse-prevention fuse. This built-in fuse works in a way that when the applied force exceeds the design load, the secondary fuse is activated and the RSFJ brace is still able to provide self-centring up to twice the target deformation with an axial force of up to 1.25 times of the target design force. The performance of this fuse is investigated by experimental tests on the component level and the results are presented. Moreover, a numerical model for a five story steel structure with RSFJ braces is developed and was subjected to non-linear static pushover and nonlinear dynamic time-history simulations in order to investigate the seismic performance of the proposed system. The findings of this research shows that the RSFJ brace system can offer substantial performance benefits and has the merit to be considered as an efficient alternative for the current bracing systems.

Key Engineering Materials, 2018

Higher seismic performance can be achieved by localizing the inelastic deformation in the connect... more Higher seismic performance can be achieved by localizing the inelastic deformation in the connections (fuses) and minimizing the residual drift that are often a determining factor in whether a structure can be repaired or re-occupied after an earthquake. This paper introduces the self-centering damage avoidance steel Moment Resisting Frames (MRFs) using innovative Resilient Slip Friction Joints (RSFJs). The RSFJ provides self-centering and energy dissipation in one compact package requiring no post-event maintenance. In this concept, the beam is connected to the column through a pinned joint at the top, an RSFJ at the bottom and a slotted web plate for transferring the shear forces, when required. The RSFJ allows for gap opening in the connection upon loading and then re-centers the system when unloading. Furthermore, a secondary fuse within the RSFJ is considered to keep maintaining a ductile behavior in the system in case of an earthquake larger than the design earthquake. The con...

Journal of Constructional Steel Research, 2017

Multi-story hybrid timber-steel structures are becoming progressively desirable owing to their ae... more Multi-story hybrid timber-steel structures are becoming progressively desirable owing to their aesthetic and environmental benefits and also to the relatively higher strength to weight ratio of timber. Moreover, there is an increasing public pressure to have low damage structural systems to minimize the destruction after severe earthquakes. A recent trend in the timber building industry is the use of cross laminated timber (CLT) wall systems. CLT is a relatively novel engineered wood based product well suited for multi-story structures. Latest research findings have shown that CLT buildings constructed with traditional steel connectors can experience high damage mainly because of stiffness degradation in the fasteners. It has been proven that friction joints can provide a perfectly elastoplastic behaviour and a stable hysteretic response. Up until now, the main disadvantage of the friction joints has been the undesirable residual displacements after an earthquake. This study presents a hybrid damage avoidant steel-timber wall system using the innovative Resilient Slip Friction (RSF) joint. The proposed system includes coupled timber walls and boundary steel column as the main lateral load resisting members. RSF joints are used as ductile links between the adjacent walls or between the walls and the steel boundary columns. The efficiency of the system has been investigated by experimental joint component tests on the RSF joint followed by reversed cyclic numeral analyses and dynamic non-linear time-history simulations on the wall system. The results confirmed that the proposed system has the potential to be recognised as an efficient lateral load resisting system.