Lead Extrusion Damper Research Articles

Experimental investigation of the effective parameters on the lead extrusion damper performance

Lead extrusion dampers (LED) are employed for seismic response control of various structures due to their advantages over other energy-dissipative devices. However, a reliable design algorithm and an optimization process are essential to ensure optimal performance within the host structural system. Thus, the influence of device parameters on the damper behavior must be clearly understood. In the first part of this comprehensive study, the effect of different parameters on the LED performance was experimentally investigated. To this end, 23 specimens with different prestressing levels, bulge-to-shaft diameter ratios, shaft-to-bulge transition zone geometries, and device length ratios were cyclically tested under varying displacement amplitudes, i.e., 5 mm, 10 mm, and 20 mm, and loading rates, 0.5 mm/s, 1.0 mm/s, and 2.0 mm/s. Subsequently, they were exposed to a ramp-type loading up to the amplified design displacement. After satisfactorily completing the experimental tests, the behavior of the LEDs was compared in terms of their hysteretic behavior, energy dissipation capacities, temperature change, and stable behavior. It was concluded that the most influential parameters on the LED behavior were the bulge-to-shaft diameter ratio and the prestressing level on the lead. In addition to its effects on improving the hysteretic behavior, having a smooth shaft-to-bulge transition zone geometry was essential to guarantee a stable damper behavior.

Experimental Investigation of High-Force-To-Volume Extrusion Damper Subjected to Cyclic and Time History Loading

Abstract The ability of energy dissipation from earthquake force in a controlled and iterative manner will play a vital role in maintaining structural reliability for various forces. High force-to-volume (HF2V) extrusion damper is a promising technology with simple designs, high damping force and achieving design requirements. This paper develops HF2V extrusion damper with multiple toothing configuration for seismic application. The experimental verification has been undertaken on lead extrusion dampers with various frequency range of 0.5 to 2 Hz. The maximum load-carrying capacity is 10.48 kN with strokes up to 5mm are observed with hysteresis loop with some recentering capability has a stiffness value up to 2*106 N/m, and force levels up to 2-10 kN. The maximum load carrying capacity for time history loading for Northridge earthquake is 11.57 kN. The overall findings suggest that silicone sealant may be employed to build and characterize extrusion dampers with maximum energy dissipation and high force/volume interactions. The suggested device may be a potentially effective way to provide additional energy dissipation to structures in seismic zones, according to the mechanical characteristics to the frequency. Additionally, the system can withstand for earthquake time histories, and ensuring maintenance-free operation even in the midst of frequent ground vibration.

Development and experimental validation of finite element models for a prestressed lead extrusion damper

The emerging trend in earthquake-resistant structural design is to dissipate some part of the seismic input energy through energy-dissipating devices (EDDs). A prominent candidate to serve this purpose is the lead extrusion damper (LED), which dissipates seismic energy by the extrusion of lead through the displacement of a bulged shaft. The LEDs should be designed as they meet the demands of the host structural system. Hence, predicting the force–displacement relation and energy dissipation characteristics of the LED is essential. To serve this purpose, comprehensive three-dimensional finite element models (FEMs) were developed in this study to simulate the cyclic behavior of a prestressed LED. The methodology consisted of performing coupon tests, the development of FEMs, and experimental verification. Coupon tests were performed for lead and steel to simulate the nonlinear material behaviors better. The models were validated against the experimental results of the LED and a steel beam-to-column connection. In general, the adapted model satisfactorily captured the experimental results. The maximum differences in the maximum force and dissipated energy predictions were about 7.5% for the generated FEMs. In addition, the mean relative difference in predicting damper forces for eight LEDs selected from the literature was about 6%. The low relative differences between the models and experiments demonstrated that the adapted FEM could reliably estimate the cyclic response of the LEDs. It can be stated that the adapted three-dimensional finite element modeling strategy can be utilized robustly for design purposes.

Development of Finite Element Model for a Special Lead Extrusion Damper

A significant amount of seismic energy is imparted to the structures during earthquakes. The energy spreads within the structure and transforms in various energy forms as dissipated through the structure. The conventional seismic design provides specific ductile regions, namely plastic hinges, on structural elements. Therefore, the energy dissipation capacities of the structural elements and the structure enhance. However, this approach accepts that the deformations will concentrate on the plastic hinge zones and severe damage may occur on structural elements within deformation limits that are defined by the seismic codes. Aim of modern seismic design is dissipating a large portion of the seismic input energy by installing energy dissipating devices (EDDs) to the structure. Thus, deformation concentrates on EDDs which can be replaced after an earthquake, and energy demand for structural elements is decreased. Lead extrusion damper (LED) is a passive EDD that utilizes the hysteretic behavior of lead. In this paper, the preliminary results of the developed finite element model (FEM) for a LED are presented. The results obtained from the finite element analysis (FEA) are compared with the experimental ones in which LEDs were exposed to sinusoidal displacements. Also, the applicability of the developed FEM is checked for different component dimensions given in the literature. The comparison study yielded a satisfactory consistency. Additionally, maximum relative difference obtained for the literature devices was reduced to 12% from 39% by the developed FEM.

Modeling limit force capacities of high force to volume lead extrusion dampers

Modeling limit force capacities of high force to volume lead extrusion dampers

Seismic performance improvement of single-storey precast reinforced concrete industrial buildings in use

Single-storey precast reinforced concrete (RC) frame type buildings are mainly preferred in manufacturing plants and storehouses. The behaviour of semi-rigid beam-column connections of the buildings is one of the main sources of uncertainty. The common damages observed after credible earthquakes were falling off large-span beams and large plastic deformations at the column base. New generation Lead Extrusion Damper (LED) developed by the authors is utilized in the seismic retrofitting of these buildings in use. This paper discusses the seismic performances of pre- and post-behaviour of the retrofitted buildings and evaluates the efficiency of the applied retrofitting technique. It is exposed that seismic demands are diminished essentially. The relative storey drifts decrease by about 40-90% while the reduction in the strain at the column base section reaches to 70%.

Seismic design and performance evaluation of controlled rocking dual-fused bridge system

It is crucial for highway bridges to remain operational after strong earthquakes as they are critical infrastructures to transport resources. In this study, an innovative seismic-resilient bridge structural system, named controlled rocking dual-fused bridge (CRDFB) system, is proposed. The CRDFB system is designed to dissipate the earthquake energy by the use of replaceable Lead-Extrusion Dampers (LEDs) at the base of the rocking piers. The state-of-the-art Equivalent Energy Design Procedure (EEDP) is adopted and modified to design the CRDFB system to achieve different performance at different levels of shaking intensities. The proposed step-by-step EEDP allows engineers to design the CRDFB system to achieve the desired performance objectives with simple hand calculations and without iterations. A 2-span and a 3-span CRDFB prototypes located in Vancouver, Canada, are designed using the proposed EEDP. To validate the performance of the proposed CRDFB system, advanced three-dimensional analytical models of prototypes are developed using OpenSees and subjected to a broad array of two-dimensional and three-dimensional nonlinear time history analyses. Simulation results show that CRDFB prototypes can successfully achieve the targeted performance, as specified by EEDP design, at different shaking intensities. Hence, the proposed CRDFB system can be designed efficiently using the EEDP design procedure outlined in this paper, and be used as an efficient, reliable, and resilient seismic force-resisting bridge system for high seismic zones.

Experimental and theoretical study of a lead extrusion and friction composite damper

A new lead extrusion and friction composite damper (LEFCD) is proposed for multi-level seismic protection. Compared with conventional metallic dampers, LEFCD is an assembly of components which are changeable and can provide specific performances. For small and moderate earthquakes, the LEFCD uses only the lead extrusion dampers. For strong earthquakes, the LEFCD uses both the lead extrusion and friction dampers simultaneously to dissipate the seismic energy. To investigate the performance of LEFCD, theoretical analyses and experimental cyclic loading tests of LEFCD were carried out. Also, finite element models of the LEFCD were established and were compared with the testing results. The theoretical analysis results indicated that the LEFCD can provide different mechanical behaviors for different LEFCD setups. Results of testing and numerical analysis showed that the LEFCD had good energy dissipation capacity and that the finite element modeling was accurate compared to the test results.

Seismic Response of Structure with Lead Extrusion Damper

Seismic Response of Structure with Lead Extrusion Damper

Retrofitting of pinned beam–column connections in RC precast frames using lead extrusion dampers

A novel retrofitting application for pinned beam–column connections in RC precast frames was investigated from experimental and numerical perspectives. The application is based on the insertion of a lead extrusion damper (LED) in regions of beam–column connection of precast RC frames. The bending moment and deformations at the column base tends to decrease with increased damping, and the shear force at the connection of the LED on the structural member increases with the insertion of an LED. Half-scale non-retrofitted and retrofitted specimens were tested on a shake table. In addition, nonlinear dynamic time history analyses were carried out. The structural behaviors of non-retrofitted and retrofitted specimens were compared based on the experimental and numerical results. Ultimate displacement and story drift of the precast frame, the bending moment and plastic deformations at the column base were significantly reduced via the insertion of an LED. Also, the numerical results are in agreement with the experimental results.

Seismic analysis of parallel structures coupled by lead extrusion dampers

In this paper, the response behaviors of two parallel structures coupled by Lead Extrusion Dampers (LED) under various earthquake ground motion excitations are investigated. The equation of motion for the two parallel, multi-degree-of-freedom (MDOF) structures connected by LEDs is formulated. To explore the viability of LED to control the responses, namely displacement, acceleration and shear force of parallel coupled structures, the numerical study is done in two parts: (1) two parallel MDOF structures connected with LEDs having same damper damping in all the dampers and (2) two parallel MDOF structures connected with LEDs having different damper damping. A parametric study is conducted to investigate the optimum damping of the dampers. Moreover, to limit the cost of the dampers, the study is conducted with only 50% of total dampers at optimal locations, instead of placing the dampers at all the floor level. Results show that LEDs connecting the parallel structures of different fundamental frequencies, the earthquake-induced responses of either structure can be effectively reduced. Further, it is not necessary to connect the two structures at all floors; however, lesser damper at appropriate locations can significantly reduce the earthquake response of the coupled system, thus reducing the cost of the dampers significantly.

Experimental testing of damage-resistant rocking glulam walls with lead extrusion dampers

When rocking structures are designed, dampers may be required to substitute conventional connections to provide load resistance and dissipate the rocking motion. This study investigates the applicability of High-Force-to-Volume (HF2V) damping devices in rocking timber structures. HF2V devices present an attractive solution since the device does not suffer stiffness or strength degradation and can be reused after an earthquake. Laboratory tests on loaded and unloaded timber walls using two HF2V devices per wall were carried out. The applicability of the devices in timber walls was investigated focusing on damper functioning, the influence of the vertical load on the self-centering behaviour of the dampers, and possible slip in all connections. The results show that the devices functioned as intended and no significant damage occurred in the devices or the timber walls. HF2V devices present a feasible solution for rocking timber walls when a damage free structural behaviour is aimed for.

Experimental study on lead extrusion damper and its earthquake mitigation effects for large-span reticulated shell

A Lead Extrusion Damper (LED) is experimentally studied under various frequencies and displacement amplitudes. Experimental results show that the force-displacement hysteresis loops of the LED are close to rectangular and the force-velocity hysteresis loops exhibit nonlinear hysteretic characteristic. Also, the LED can provide consistent energy dissipation without any stiffness degradation. Based on the experimental results, a mathematical model is then proposed to describe the effects of frequency and displacement on property of LED. It can be proved from the comparison between experimental and numerical results that the mathematical model can accurately describe the mechanical behavior of LED. Subsequently, the seismic responses of the Schwedler reticulated shell structure with LEDs are analyzed by ANSYS software, in which three different installation forms of LEDs are considered. It can be concluded that the LED can effectively reduce the displacement and acceleration responses of this type of structures.

The Behavior of a Steel Connection Equipped with the Lead Extrusion Damper

The seismic behavior of the steel connection equipped with the lead extrusion damper (LED) is examined through the experimental and analytical studies. The LED implemented has spherical type bulge and does not consist any lubricant layer. The experimental study is performed in Structural and Earthquake Engineering Laboratory of Istanbul Technical University (STEELAB). In the experimental part, force-displacement relations of the connections with and without LED are achieved for the reversal displacement cycles. The measures of the dissipated energy, the equivalent damping ratio and the effective stiffness are obtained from the experimental study and compared for the connections. The total energy dissipated by the connection with the LED is approximately 175% greater than the total energy dissipated by the bare connection. In the analytical part of the study, nonlinear dynamic time history analyses are performed for the selected earthquakes and mass condition using the analytical models for the connections with and without LED. The maximum top displacement decreases approximately 50% for the connection equipped with the LED respect to the bare connection for the considered earthquakes. The maximum value of restoring force for the connection equipped with LED is approximately 25% greater than the bare connection for the accomplished analyses. Finally, the LED responses obtained in the nonlinear time history analyses are compared with the isolated LED test results.

Seismic Design of Steel Structures with Lead-Extrusion Dampers as Knee Braces

Seismic Design of Steel Structures with Lead-Extrusion Dampers as Knee Braces

Application of Lead Extrusion Dampers for Seismic Control of Viaducts

AbstractTo examine the hysteretic behavior of lead extrusion dampers (LEDs) and their application for the seismic control of viaducts, an experimental research on LEDs according to different heights and lengths of the convex of the extrusion axis was conducted. The feasibility of using LED for seismic control of viaducts and LED design methods are also discussed. The study shows that the height and length of the axis convex can affect the yield force of the LEDs and that the yield force can increase with the increase in height and length of the axis convex. Automobile braking force, temperature effect, and expansion joint width must be considered when LEDs are used on viaducts. Three seismic control methods for LED application are shown to be feasible and to exhibit good seismic control effects.

High-Force-to-Volume Seismic Dissipators Embedded in a Jointed Precast Concrete Frame

An experimental and computational study of an 80-percent scale precast concrete 3D beam-column joint subassembly designed with high force-to-volume (HF2V) dampers and damage-protected rocking connections is presented. A prestress system is implemented using high-alloy high-strength unbonded thread-bars through the beams and columns. The thread-bars are posttensioned and supplemental energy dissipation is provided by internally mounted lead-extrusion dampers. A multilevel seismic performance assessment (MSPA) is conducted considering three performance objectives related to occupant protection and collapse prevention. First, bidirectional quasi-static cyclic tests characterise the specimen’s performance. Results are used in a 3D nonlinear incremental dynamic analysis (IDA), to select critical earthquakes for further bidirectional experimental tests. Thus, quasi-earthquake displacement tests are performed by using the computationally predicted seismic demands corresponding to these ground motions. Resulting damage to the specimen is negligible, and the specimen satisfies all performance objectives related to serviceability, life-safety, and collapse prevention.

Investigation of Optimal Seismic Design Methodology for Piping Systems Supported by Elasto-plastic Dampers (Part 2: Applicability for Seismic Waves with Various Frequency Characteristics)

In this study, the applicability of a previously developed optimal seismic design methodology, which can consider the structural integrity of not only piping systems but also elasto-plastic supporting devices, is studied for seismic waves with various frequency characteristics. This methodology employs a genetic algorithm and can search the optimal conditions such as the supporting location and the capacity and stiffness of the supporting devices. Here, a lead extrusion damper is treated as a typical elasto-plastic damper. Numerical simulations are performed using a simple piping system model. As a result, it is shown that the proposed optimal seismic design methodology is applicable to the seismic design of piping systems subjected to seismic waves with various frequency characteristics. The mechanism of optimization is also clarified.

Lead extrusion dampers for reducing seismic response of coolant channel assembly

In Indian type pressurized heavy water reactors (PHWRs), two fuelling machines (F/Ms) are located on either side of the reactor. The behavior of the coolant channel and tie rod when fuelling machines are engaged on both the ends of the channel for refueling under earthquake is studied. It is observed that the loads acting on the coolant tube were high. In order to reduce the earthquake load acting on coolant channel the fuelling machines are restrained by energy absorbers called lead extrusion dampers (LED). The design of an LED is performed based on the extrusion principle. The aim of the paper is to study the effectiveness of such a device in reducing the response. It was observed that the stresses in the coolant channel due to earthquake are reduced significantly when LEDs are used. Response spectrum analysis is also carried out for the system with LED. In this analysis the LED is replaced with an equivalent viscous damper and stiffness obtained using Caughy’s linearisation techniques. Response spectrum analysis results and the nonlinear time history analysis results show good agreement.

Energy Absorbing Characteristics of a High-Damping Support Utilizing Plastic Deformation of Lead and the Seismic Response Characteristics of Piping Systems

In order to reduce the number of conventional support devices for the piping system, such as oil snubbers or mechanical snubbers, consequently to reduce the plant cost, various kinds of high damping supports have been developed. As one of these high damping supports, the authors have developed a rotary type lead extrusion damper, and investigated the energy absorbing characteristics and the seismic response reduction of piping systems through the fundamental tests and large scale 3D piping system tests. In this report, the relationships between the energy absorbing characteristics of a rotary type lead extrusion damper and seismic response reduction of piping systems are summarized and clarified. Furthermore, in the view point of damper functional integrity, the relationships between the accumulated absorbed energy and the piping system seismic response were discussed, and the important items in designing the piping system supported by lead extrusion dampers are summarized.