Seismic performance evaluation of an infilled rocking wall frame structure through quasi-static cyclic testing

Earthquake investigations have illustrated that even code-compliant reinforced concrete frames may suffer from soft-story mechanism.This damage mode results in poor ductility and limited energy dissipation.Continuous components offer alternatives that may avoid such failures.A novel infilled rocking wall frame system is proposed that takes advantage of continuous component and rocking characteristics.Previous studies have investigated similar systems that combine a reinforced concrete frame and a wall with rocking behavior used.However,a large-scale experimental study of a reinforced concrete frame combined with a rocking wall has not been reported.In this study,a seismic performance evaluation of the newly proposed infilled rocking wall frame structure was conducted through quasi-static cyclic testing.Critical joints were designed and verified.Numerical models were established and calibrated to estimate frame shear forces.The results evaluation demonstrate that an infilled rocking wall frame can effectively avoid soft-story mechanisms.Capacity and initial stiffness are greatly improved and self-centering behavior is achieved with the help of the infilled rocking wall.Drift distribution becomes more uniform with height.Concrete cracks and damage occurs in desired areas.The infilled rocking wall frame offers a promising approach to achieving seismic resilience.

Shake-table testing of a self-centering precast reinforced concrete frame with shear walls

The seismic performance of a self-centering precast reinforced concrete （RC） frame with shear walls was investigated in this paper. The lateral force resistance was provided by self-centering precast RC shear walls （SPCW）, which utilize a combination ofunbonded prestressed post-tensioned （PT） tendons and mild steel reinforcing bars for flexural resistance across base joints. The structures concentrated deformations at the bottom joints and the unbonded PT tendons provided the self-centering restoring force. A 1/3-scale model of a five-story self-centering RC frame with shear walls was designed and tested on a shake-table under a series of bi-directional earthquake excitations with increasing intensity. The acceleration response, roof displacement, inter-story drifts, residual drifts, shear force ratios, hysteresis curves, and local behaviour of the test specimen were analysed and evaluated. The results demonstrated that seismic performance of the test specimen was satisfactory in the plane of the shear wall; however, the structure sustained inter-story drift levels up to 2.45%. Negligible residual drifts were recorded after all applied earthquake excitations. Based on the shake-table test results, it is feasible to apply and popularize a self-centering precast RC frame with shear walls as a structural system in seismic regions.

Seismic behavior and mechanism analysis of innovative precast shear wall involving vertical joints

To study the seismic performance and load-transferring mechanism of an innovative precast shear wall(IPSW) involving vertical joints, an experimental investigation and theoretical analysis were successively conducted on two test walls. The test results confirm the feasibility of the novel joints as well as the favorable seismic performance of the walls, even though certain optimization measures should be taken to improve the ductility. The load-transferring mechanism subsequently is theoretically investigated based on the experimental study. The theoretical results show the load-transferring route of the novel joints is concise and definite. During the elastic stage, the vertical shear stress in the connecting steel frame(CSF) distributes uniformly; and each high-strength bolt(HSB)primarily delivers vertical shear force. However, the stress in the CSF redistributes when the walls develop into the elastic-plastic stage. At the ultimate state, the vertical shear stress and horizontal normal stress in the CSF distribute linearly; and the HSBs at both ends of the CSF transfer the maximum shear forces.

Wing walls for enhancing the seismic performance of reinforced concrete frame structures

A building retrofitted with wing walls in the bottom story, which was damaged during the 2008 M8.0 Wenchuan earthquake in China, is introduced and a corresponding 1/4 scale wing wall-frame model was subjected to shake table motions to study the seismic behavior of this retrofitted structural system. The results show that wing walls can effectively protect columns from damage by moving areas that bear reciprocating tension and compression to the sections of the wing walls, thus achieving an extra measure of seismic fortification. A ‘strong column-weak beam＇ mechanism was realized, the flexural rigidity of the vertical member was strengthened, and a more uniform distribution of deformation among all the stories was measured. In addition, the joint between the wing walls and the beams suffered severe damage during the tests, due to an area of local stress concentration. A longer area of intensive stirrup is suggested in the end of the beams.

Shear-resistant behavior of light composite shear wall

Shear test results for a composite wall panel in a light composite structure system are compared with test results for shear walls in Japan.The analysis results show that this kind of composite wall panel works very well,and can be regarded as a solid panel.The composite wall panel with a hidden frame is essential for bringing its effect on shear resistance into full play.Comprehensive analysis of the shear-resistant behavior of the composite wall panel suggests that the shear of the composite shear wall panel can be controlled by the cracking strength of the web shearing diagonal crack.

Towards experimental studying the airborne sound insulation of light frame walls with staggered studs

Light frame walls(LFWs) serve as common partition walls in prefabricated buildings due to their lightweight nature, costeffectiveness, energy efficiency, and adaptability for rapid on-site assembly. However, their acoustic insulation capability is hindered by issues such as sound bridges, resonance, and coincidence dips, resulting in inadequate sound insulation. This study aims to propose LFW designs with superior acoustic insulation suitable for practical engineering while meeting prevailing national standards. Nine full-scale LFW configurations were subjected to laboratory testing to evaluate the impact of staggered stud arrangements, stud types, and incorporation of compounded materials. The tests were performed between 100 and 5000 Hz,and the sound pressure level and reverberation time at 1/3 octave band were measured and used to calculate the weighted sound insulation index(Rw). Results demonstrated that the outlined design modifications significantly enhanced the sound insulation of the LFW. These modifications effectively mitigate the influence of sound bridges while addressing resonance and coincidence dips inherent in the wall system. Particularly noteworthy was the superior sound insulation achieved by staggered-stud LFWs with compounded materials, surpassing that of autoclaved lightweight concrete walls commonly used in prefabricated constructions despite having lesser thickness and surface density. Rwvalues increased from 43 to 54 dB compared to conventional LFWs, translating to a notable elevation in airborne sound insulation level from 4 to 7 as an internal separation component,meeting the requisite standards for most applications.

Research on Seismic Design of High-Rise Buildings Based on Framed-Shear Structural System

Under the rapidly advancing economic trends,people’s requirements for the functionality and architectural artistry of high-rise structures are constantly increasing,and in order to meet such modern requirements,it is necessary to diversify the functions of high-rise buildings and complicate the building form.At present,the main structural systems of high-rise buildings are:frame structure,shear wall structure,frame shear structure,and tube structure.Different structural systems determine the size of the load-bearing capacity,lateral stiffness,and seismic performance,as well as the amount of material used and the cost.This project is mainly concerned with the seismic design of frame shear structural systems,which are widely used today.

Numerical modeling of external light gauge steel framed wall systems exposed to bushfire flame zone conditions

Bushfire-related building losses cause adverse economic impacts to countries prone to bushfires.Building materials and components play a vital role in reducing these impacts.However,due to high costs of experimental studies and lack of numerical studies,the heat transfer behavior of building’s external components in bushfire-prone areas has not been adequately investigated.Often large-scale heat transfer models are developed using Computational Fluid Dynamics(CFD)tools,and the availability of CFD models for heat transfer in building components improves the understanding of the behavior of systems and systems of systems.Therefore,this paper uses a numerical modeling approach to investigate the bushfire/wildfire resistance of external Light gauge Steel Framed(LSF)wall systems.Both full-scale and small-scale heat transfer models were developed for the LSF wall systems.Experimental results of six internal and external LSF wall systems with varying plasterboard thickness and cladding material were used to validate the developed models.The study was then extended to investigate the bushfire resistance of seven external wall systems under two different bushfire flame zone conditions.The results illustrate the significant effects of fire curves,LSF wall components and configuration on the heat transfer across the walls.They have shown 1)the favorable performance of steel cladding and Autoclaved Aerated Concrete(AAC)panels when used on the external side of wall systems and 2)the adequacy of thin-walled steel studs’load-bearing capacity during bushfire exposures.This study has shown that most of the investigated external LSF walls could be reused with cost-effective retrofitting such as replacing the Fire Side(FS)steel cladding after bushfire exposures.Overall,this study has advanced the understanding of the behavior of external light steel framed walls under bushfire flame zone conditions.

Development of realistic design fire time-temperature ：urves for the testing of cold-formed steel wall systems

Fire resistance rating of light gauge steel frame （LSF） wall systems is obtained from fire tests based on the standard fire time-temperature curve. However, fire severity has increased in modem buildings due to higher fuel loads as a result of modern furniture and light weight constructions that make use of thermoplastics materials, synthetic foams and fabrics. Some of these materials are high in calorific values and increase both the spread of fire growth and heat release rate, thus increasing the fire severity beyond that of the standard fire curve. Further, the standard fire curve does not include a decay phase that is present in natural fires. Despite the increasing usage of LSF walls, their behavior in real building fires is not fully understood. This paper presents the details of a research study aimed at developing realistic design fire curves for use in the fire tests of LSF walls. It includes a review of the characteristics of building fires, previously developed fire time-temperature curves, computer models and available parametric equations. The paper highlights that real building fire time-temperature curves depend on the fuel load representing the combustible building contents, ventilation openings and thermal properties of wall lining materials, and provides suitable values of many required parameters including fuel loads in residential buildings. Finally, realistic design fire time-temperature curves simulating the fire conditions in modem residential buildings are proposed for the testing of LSF walls.