Post-earthquake Repair Research Articles

Determination of optimal behavior of self-centering multiple-rocking walls subjected to far-field and near-field ground motions

In recent years, innovative seismic resistant systems have been introduced based on the Damage Avoidance Design (DAD) philosophy rather than the conventional plastic design-based methods to reduce damages to buildings and to decrease post-earthquake repair costs. Self-centering multiple-rocking walls are amongst these innovative systems. This study aims to determine the optimum number of rocking sections in self-centering concrete multiple rocking walls. To this aim, the seismic behavior of self-centering (SC) concrete rocking walls of 8, 12, 16, and 20 stories with different numbers of rocking sections were examined. Several non-linear time-history analyses were carried out via OpenSEES software in a two-¬dimensional framework. Three sets of ground motions were considered including 22 Far-Field (FF), 14 Near-Field-Pulse (NFP), and 14 Near-Field-no Pulse (NFnP). Five types of quad-rocking walls and one type of dual-rocking walls were specified and compared with base-rocking walls and fixed-base walls. To perform this comparison, a set of utility coefficients was defined to integrate different response aspects including shear and moment demands as well as the residual drifts. The results showed that the effects of higher modes (shear and moment demand) increase with the increase in the height of the rocking structures. Furthermore, NFnP and FF records produced higher mode effects in rocking systems as compared to NFP records. The results suggested that the quad-rocking walls with the reduced tendon area in the first block (R4-S1) are highly effective in reducing the effects of higher modes in NFP and NFnP records. They showed maximum utility coefficients of 67% and 65%, respectively. Also, quad-rocking walls with the reduced tendon area in the third block (R4-S3) were more effective under FF records and their maximum utility coefficient was 65%. The residual roof drift of rocking walls was so negligible that its maximum value in the 8-story structure under NFP records was 0.0008.

Earthquake Damage Repair Loss Estimation in New Zealand: What Other Variables Are Essential Based on Experts’ Opinions?

Major earthquakes can cause extensive damage to buildings and alter both the natural and built environments. Accurately estimating the financial impact from these events is complex, and the damage is not always visible to the naked eye. PACT, SLAT, and HAZUS are some of the computer-based tools designed to predict probable damage before an earthquake. However, there are no identifiable models built for post-earthquake use. This paper focuses on verifying the significance and usage of variables that specifically need to be considered for the post-earthquake cost estimation of earthquake damage repair work (CEEDRW). The research was conducted using a questionnaire survey involving 92 participants who have experience in cost estimating earthquake damage repair work in New Zealand. The Weighted Average, Relative Importance Index (RII), and Exploratory Factor Analysis were used to analyse the data. The research verified that eleven major variables that are significant to the CEEDRW and should be incorporated to cost estimation models. Verified variables can be used to develop a post-earthquake repair cost estimation tool and can be used to improve the pre-earthquake loss prediction tools.

Experimental study on mechanical behaviour of replaceable energy dissipation connectors for precast concrete frames

An innovative replaceable energy dissipation connector (REDC) is proposed in this paper that can be used as a connecting component as well as a metal-yield damper in the beam end of a precast concrete frame. In addition to the precast concrete frame for the REDC (REDC-PCF), a construction and post-earthquake repair method for it is proposed. An experimental study on the mechanical behaviour of REDCs under cyclic reverse loading was conducted to study their axial stiffness, hysteretic behaviour, energy dissipation capacity, and other properties. The results revealed that REDCs manufactured using high ductility steel exhibited a stable hysteretic property and high low-cycle fatigue performance under cyclic reverse loading conditions. On the basis of the test results, the REDC has a promising future in seismic design because it can be widely applied in precast concrete frames in high-seismic activity zones. A numerical analysis of the transverse displacement of the mechanical property of the REDC was also conducted. The results showed that the transverse displacement of the specimen had little effect on its mechanical property and low-cycle fatigue capacity. Thus, the uniaxial testing of REDC specimens would be effective in predicting the properties of beam–column joints.

Seismic performance of self-centering steel-timber hybrid shear wall structures

This paper presents the seismic performance assessment of self-centering steel-timber hybrid shear wall (SC-STHSW) structures. The hybrid structure introduces extra re-centering action to itself through the combination of the post-tensioned steel frame (PTSF) with the light-framed wood shear wall. Slip friction dampers (SFDs) are used as connectors between the frame and the wood wall. An OpenSees model for the SC-STHSW was established and validated versus experimental results. Then, a 9-story SC-STHSW structure was designed with the direct displacement-based design procedure, and the design was checked through nonlinear time history analysis. Based on the designed 9-story SC-STHSW structure, the influence of a key parameter (i.e., self-centering ratio α E ) on the structure's dynamic performance was investigated by considering different hazard levels. The dynamic response of three 9-story SC-STHSW structures with different α E values was compared in terms of maximum inter-story drift (MaxISD) and maximum residual inter-story drift (MaxRISD). Meanwhile, the fragility curve of a 9-story conventional steel-timber hybrid shear wall (STHSW) structure without self-centering capability was calculated based on the cloud analysis, and the fragility curves were compared with those of the 9-story SC-STHSW. It was found that the increase of α E was not only beneficial to decrease the system's MaxRISD but also positive in enhancing system's control over its MaxISD. The lower limit of α E was suggested to be 0.6 when the system was used in high seismic regions. The 9-story SC-STHSW ( α E = 0.6) was comparable to the 9-story STHSW system in regards to the control of MaxISD, which illustrated the advancement of the new system since, at the same time, it had better re-centering ability to decrease post-earthquake repair costs. • A self-centering steel-timber hybrid shear wall structure was designed through the direct displacement-based design. • The influences of α E on the new structure’s seismic performance were explored. • Based on cloud analysis, the seismic fragility of the new structure was compared with the other structure.

Influence of abutment straight backwall fracture on the seismic response of bridges

AbstractField reconnaissance reports reveal the seismic vulnerability of bridge abutment foundations. To reduce the time and cost of postearthquake repair, modern seismic design specifications allow abutment backwalls to fracture before the supporting abutment foundations reach their maximum strength. This design strategy enables abutment backwalls to function as a fuse, thus protecting the abutment foundations from experiencing excessive forces and damage. This paper introduces a new abutment modeling scheme to capture the shear fracture mechanism of straight backwalls in seat abutments. To this end, a backwall connection spring is developed and incorporated into a spring system that simulates the behavior of various abutment components. The importance of considering the backwall fracture is examined by reviewing conventional modeling methodologies for abutments and building companion numerical models. Static pushover and incremental dynamic analyses (IDAs) were conducted for two bridges (single‐ and two‐span) modeled by both the proposed and conventional abutment modeling schemes. Moreover, component‐level fragility curves are developed using IDA results. The comparisons show that the conventional abutment modeling schemes significantly overestimate abutment foundation damage and underestimate the likelihood of deck unseating, column damage, and bearing displacement in the passive direction. Conversely, the proposed modeling scheme is able to capture the essential seismic responses of various components in seat abutment bridges. The consideration of backwall fracture in the modeling of abutment components enables a more rational seismic response assessment of bridges with backwalls, which are likely to be damaged during earthquakes, particularly for bridges which are seismically designed to protect abutment foundations.

Cyclic loading tests of an earthquake-resilient prefabricated steel frame with open-web steel channel beams

Based on the ideas of damage control and energy dissipation by sliding, this paper puts forward an earthquake-resilient prefabricated steel frame with two open-web steel channel beams (OWSCBs). To study its seismic performance and post-earthquake repair performance, the low frequency cyclic loading tests and low cyclic fatigue tests were carried out on five specimens, and several seismic behavior indicators such as the hysteretic curve, the slip curve, the strain analysis curve and the skeleton curve of frames were obtained. The influence of the thickness of the flange cover plate (FCP), the number of connecting bolts in the FCP and the residual deformation on seismic performance of prefabricated steel frames before and after restoration were mainly investigated. The results show that there are two main failure modes of the specimen, one is FCP friction sliding and the other is local buckling deformation of FCP dog-bone weakened section, while the main components such as beams and columns are still in the elastic stage. The repaired specimens have the same experimental phenomena and seismic performance as the initial specimen, which indicates that the functional restoration of prefabricated steel frame structures can be realized by repairing beam-column joint connecting devices. The repair process of the specimen with residual story drift went well, and this specimen still showed good mechanical and seismic performance after repaired. The overall bearing capability of the specimens decreases obviously with the thickness of the FCP decreasing. The decrease in the number of the connecting bolts in the FCP will reduce the critical sliding load of the FCP, which will lead to the slippage of the FCP in advance and reduce the overall bearing capability of the specimens.

Component-Level Seismic Performance Assessment of Instrumented Super High-Rise Buildings under Bidirectional Long-Period Ground Motions

AbstractA detailed seismic performance assessment for super high-rise buildings is essential for decision-making on postearthquake repair, maintenance, and reoccupation. This paper proposes a proba...

Study on the Seismic Behavior of Eccentrically Braced Steel Frames of Replaceable Shear Links With Web Opening

The replaceable energy-dissipating beam is convenient for post-earthquake repair and reinforcement or direct replacement. A quasi-static test study of an eccentrically supported steel frame with replaceable energy dissipating beam sections was performed, and the hysteretic performance and failure mode of the eccentrically supported steel frame with replaceable energy dissipative beam sections were obtained. Based on the test results, the structure of the energy dissipating beam segment was improved, and a number of K-shaped eccentric support frame finite element models for the web opening ratios of different energy dissipating beam segments were established. Nonlinear numerical analysis was performed on its hysteretic performance. The research shows that the finite element analysis is in good alignment with the test results. The opening of the web in the energy-consuming beam segment can effectively reduce the stress level of the frame beam and ensure that large plastic deformation occurs within the energy-consuming beam segment. With the increase of the opening ratio, the ultimate bearing capacity, initial stiffness and energy consumption of the frame have all shown a downward trend. The research provides a basis for the seismic design of similar structures and can guide the design of related projects.

A 5D simulation method on post-earthquake repair process of buildings based on BIM

The post-earthquake repair process of buildings is one of the key components of building seismic resilience. Understanding the details of the repair process in advance will benefit the evaluation and decision making for the seismic resilience of buildings. To this end, a five-dimensional (5D) simulation method on the post-earthquake repair process of buildings is proposed based on building information modeling (BIM), by which the repair activities can be presented in the way associated with a 3D model, time (denoted as the fourth dimension), and the related costs (denoted as the fifth dimension). First, a decision-making model of repair schemes based on the interval index of the possibility degree is created to determine the optimal post-earthquake repair schemes for a damaged building. Subsequently, an algorithm based on separate flow-repetitive process is designed to automatically make the repair schedule on a BIM platform according to the determined repair schemes. Finally, an algorithm of automatic mapping between the components in BIM and their repair schedules is developed, so that a 5D simulation of a post-earthquake repair process can be implemented. A six-story office building is selected as a case study, and the details of the post-earthquake repair process (e.g., the costs of labor, material and equipment over the repair time) are presented by the proposed 5D simulation method. The outcome of this study can be used to evaluate the seismic resilience of buildings and also to facilitate the decision making for seismically resilient buildings by providing the detailed guidance of the repair process.

Factors impacting post-earthquake damage repair cost estimations

Purpose Reconstruction processes after an earthquake require estimating repair costs to decide on whether to repair or rebuild. This requires an accurate post-earthquake cost estimation tool. Currently, there are no post-earthquake loss estimation models to estimate repair costs accurately. There are loss assessment tools available, namely, HAZUS, performance assessment calculation tool (PACT), seismic performance and loss assessment tool (SLAT) and seismic performance prediction tool, which have not been specifically used for post-earthquake repair cost estimation. This paper aims to focus on identifying factors that need to be considered when upgrading these tools for post-earthquake repair cost estimation. Design/methodology/approach The research was conducted as an exploratory study using a literature review, document analysis of the PACT, SLAT and HAZUS software and 18 semi-structured interviews. Findings The research identified information sources available for estimation and factors to be considered when developing estimations based on the information sources. Research limitations/implications The data was collected from professionals who were involved mostly in housing repair work in New Zealand. Therefore, impact of these repair work factors might vary in other forms of structures such as civil structures include bridges and the country as a result of varying construction details and standards. Practical implications The identified factors will be used to improve the loss estimation tools are such as PACT and HAZUS, as well as to develop a post-earthquake repair cost estimation tool. Originality/value Currently, the identified factors impacting post-earthquake damage repair cost estimations are not considered in loss estimation tools. Factors identified in this research will help to develop a more accurate cost estimation tool for post-earthquake repair work.

Experimental study of earthquake-resilient end-plate type prefabricated steel frame beam-column joint

In order to avoid the complex stress field of traditional beam-column joints caused by arranging end side plate or support plate on beam end, and realize the earthquake-resilient of joints, based on the plastic damage control idea, a kind of end-plate type prefabricated steel frame beam-column joint (EPPSFJ) is put forward in this paper. The new type joint mainly consists of the circular steel tube column with cantilever beam, ordinary beam, and the connecting devices. The EPPSFJ can realize stiffness control of the connection by adjusting the thickness of the flange cover plate (FCP), the distance between the middle bolts and other parameters, and make use of the plastic distortion and friction sliding of the FCP to dissipate the seismic energy, so as to ensure the basic elasticity of the structural member and realize the rapid post-earthquake repair of the joint. In the article, the low cycle load test is carried out on five specimens and one repair specimen to obtain the failure pattern, hysteresis curve and strain curves of joints etc., The impact rule of parameters such as the thickness of cantilever beam flange, the distance between the middle bolts, thickness and weakening form of FCP on the seismic performance is researched. The experimental study shows that: the joints have good seismic performance by reasonably designing parameters of bolts and the FCP, and the plastic distortion is focused on the FCP easily replaced, which make sure that plastic damage does not occur at the structural member. The repaired specimen still has great energy dissipation capacity, ductility and other seismic performance indexes, which indicates that the joint can be quickly repaired post-earthquake through replacing the FCP and other connecting devices.

In-plane shear behaviour by diagonal compression testing of brick masonry walls strengthened with basalt and steel textile reinforced mortars

This paper presents an experimental study of the structural behaviour of masonry walls retrofitted with Textile Reinforced Mortar (TRM) to improve their in-plane shear strength and deformation capacity. The experimental programme consists in diagonal compression testing of ten specimens of clay brick and lime mortar masonry retrofitted with three different TRM systems: i) continuous bidirectional grids of basalt TRM, ii) discrete bands of unidirectional steel TRM and iii) continuous basalt TRM on the wall’s inner face and bed joints structural repointing with near surface mounted helical stainless steel bars on the wall’s outer face. Two of the specimens were tested two times, i.e. in the unreinforced condition and subsequently in the repaired configuration including basalt TRM retrofitting. The experimental results show that the adopted TRM solutions produce a beneficial increase of shear resistance and ductility, making them suitable for seismic retrofitting and post-earthquake repair.

Seismic Study of Skew Bridge Supported on Laminated‐Rubber Bearings

Skew bridges consisting of simply supported girders, continuous decks, and laminated‐rubber bearings are widely used in western China; however, they are highly vulnerable to strong earthquakes. To investigate the seismic performance of skew bridges considering the sliding behavior of laminated‐rubber bearings, the Duxiufeng Bridge located in Sichuan, China, was used as a prototype bridge. This bridge is a skew bridge that suffered seismic damage during the 2008 Wenchuan earthquake. The possible seismic response of this skew bridge under the Wenchuan earthquake was simulated, and the postearthquake repair methods were analyzed considering the effects of bearing types and cable restrainers. Parametric studies, using the finite element method, were also performed to investigate the effects of the skew angle and friction coefficient of the bearings on the seismic response of the skew bridge. The results indicate that pin‐free bearings could effectively control the seismic displacement of the bridge, and the cable restrainers with an appropriate stiffness could significantly reduce the longitudinal residual displacements. The effect of skew angles is less significant on skew bridges with laminated‐rubber bearings than on rigid‐frame skew bridges because of the sliding between the girders and bearings. The residual displacements of the bearings were more sensitive to the variation in the friction coefficient between the laminated‐rubber bearings and the girders compared to the maximum seismic displacements.

Spatial substructure hybrid simulation tests of high-strength steel composite Y-eccentrically braced frames

High-strength steel composite Y-eccentrically braced frame (Y-HSS-EBF) is a novel structural system. In this study, the spatial substructure hybrid simulation test (SHST) method is used to further study the seismic performance of Y-HSS-EBF. Firstly, based on the cyclic loading tests of two single-story single-span Y-HSS-EBF planar specimens, a finite element model in OpenSees was verified to provide a reference for the numerical substructure analysis model for the later SHST. Then, the SHST was carried out on the OpenFresco test platform. A three-story spatial Y-HSS-EBF model was taken as the prototype, the top story was taken as the experimental substructure, and the remaining two stories were taken as the numerical substructure to be simulated in OpenSees. According to the test results, the validity of the SHST was verified, and the main seismic performance indexes of the SHST model were analyzed. The results show that, the SHST based on the OpenFresco platform has good stability and accuracy, and the results of the SHST agree well with the global numerical model of the structure. Under strong seismic action, the plastic deformation of Y-HSS-EBF mainly occurs in the shear link, and the beam, beam-columns and braces can basically remain in the elastic state, which is conducive to post-earthquake repair.

Study on Seismic Behavior of Steel Frame-Steel Shear Wall with Assembled Two-Side Connections

Low-cycle reciprocating loading tests were carried out on a steel frame with prefabricated beam-only connected steel plate shear wall (specimen A) and a steel frame with welded beam-only connected steel plate shear wall (specimen B). The seismic performance of the two different types of steel frame-steel plate shear wall specimens was studied and the failure modes, hysteresis curve, skeleton curve, and seismic performance index, etc of two groups of specimens were obtained, together with the studies of failure characteristics, ductility, energy dissipation, and stiffness degradation of the two specimens. The results showed that the assembled steel frame-steel plate shear wall with connection joints of steel shear wall with discontinuous cover plate connected on both sides (DCPC) have good seismic performance. On the basis of no loss of seismic performance, DCPC joints can provide better energy dissipation capacity than traditional welded steel plate shear wall structures and ensure the good postearthquake repair function.

Seismic evaluation of low-rise steel building frames with self-centering energy-absorbing rigid cores designed using a force-based approach

This paper focuses on a new lateral-force-resisting system – the Self-Centering Energy-Absorbing Rigid Core system (denoted as the SCENARIO system)-for achieving enhanced seismic performance and improved post-earthquake reparability in low-rise steel building frames. Friction-Spring Dampers (FSDs) are included in the SCENARIO system to achieve the self-centering feature and dissipate hysteretic energy. Moreover, Buckling Restrained Braces (BRBs) are included in the SCENARIO system to absorb earthquake energy if needed. A design procedure was proposed for the SCENARIO system. Results from Nonlinear Static Analyses (NSA) show that the design procedure can enable the SCENARIO system to exhibit the intended nonlinear behavior. A representative three-story demonstration building was considered in this research to investigate the seismic response of the low-rise steel buildings with the SCENARIO systems to resist the lateral seismic forces. Three designs adopting different response modification factors to determine the design base shears were performed for the demonstration building. Results from Nonlinear Response History Analyses (NRHA) of the considered systems show that the SCENARIO systems can exhibit satisfactory seismic responses when designed with the response modifications factors of 6 and 8 which are assigned to conventional steel braced frames. Moreover, it was found that the residual inter-story drift ratios of the SCENARIO system can be lower than 0.005 rad even under the MCE excitations, creating a satisfactory condition for the post-earthquake repair work if necessary.

Design theory of earthquake-resilient prefabricated beam-column steel joint with double flange cover plates

Prefabricated steel structure with earthquake-resilience has become one of the hot topics in the field of seismic engineering. Based on the idea of damage control, this paper proposes a new type of earthquake-resilient prefabricated beam-column steel joint (PBCSJ) with double flange cover plates (FCPs), which is formed by a circle tubular steel column with a cantilever beam, an independent beam and a set of connecting devices in between. After the comprehensive analysis of the mechanical behaviour of PBCSJ, the formulas are derived from three aspects: the thickness of FCPs, the number of flange connection bolts and the middle bolts interval. Then the design theory of earthquake-resilient PBCSJ with double FCPs is established in this paper, and its rationality and applicability are verified by 11 groups of 57 numerical examples. The study shows that the design theory can be used to accurately calculate the yield load of PBCSJ. The sliding moment of flange connection bolts and the ultimate load of PBCSJ also can be controlled effectively. The joints designed according to this theory have superior bearing capacity and ductility, which ensures that the beams and columns are kept in elastic stage and provides preconditions for post-earthquake repair of PBCSJ.

Assess the Effectiveness of SMA on Response of Steel Connection with PT Strands

Using the post-tensioned (PT) elements can significantly plummet the persistent damages and the relevant costs to post-earthquake repair and maintenance, facing earthquake hazards. Rooted in a PT self-centering steel connection, the deformation and residual drift of the main members are limited to the linear elastic branch derived from existence of steel strands by omitting the gap between beam-column connections. The shape memory alloys (SMA) material has super elastic property according to the conversion of austenite to martensite phases due to changes in the temperature and stress. In this research, a nonlinear behavior of PT steel connection with top-and-seat angles was analyzed due to vulnerability of the connection during the cyclic loading, so that the connection was equipped with stiffened angles and SMA material in order to improve seismic behavior of the steel connection. The results illustrated that the using the equipped angles with SMA property flourish a logical performance in the steel connection under cyclic loading, by which the connection witnesses an appropriate energy dissipation (ED) capacity and dramatically effect on initial stiffness.

Experimental study of earthquake-resilient prefabricated sinusoidal corrugated web beam-column joint

The functional structure of earthquake-resilient has become a frontier issue in the field of structural seismic performance. For researching the performance of seismic and post-earthquake resilience of earthquake-resilient prefabricated sinusoidal corrugated web beam-column joint (PSCWJ) previously proposed by the author, the low frequency cyclic loading test and the finite element (FE) numerical verification have been carried out on eight specimens in this paper. The hysteretic curve, skeleton curve, strain variation curve, ductility, energy dissipation and other seismic performance indexes of this joint have been obtained. The impact of weakend form, thickness and strength of the flange cover plate (FCP), and the gap between beams on the joint seismic performance as well as the post-earthquake repair performance have been investigated. The results indicate that: the reasonably designed joint does well in bearing capacity, ductility and energy dissipation capability; the quick repair of joint can be realized by installing a new connection device, and the repaired joint can still meet the seismic performance requirements; the FCP weakened by a straight dog-bone profile is better for the joint plastic development and the relocation of plastic hinge at the beam end; the gap properly set between beams can effectively promote the rotation capability of the joint; the yield load of joint is directly decided by the thickness and the strength of the FCP.

Mechanical Behavior of a Double-Column Self-Centering Pier Fused with Shear Links

A double-column self-centering pier fused with shear links is a novel structure developed to reduce residual deformation and facilitate post-earthquake repair. With this novel structure, the seismic resilience of bridges can be improved, and the reliability of lifeline infrastructure can be ensured. This paper presents the proposed pier configuration and investigates the mechanical behavior of the pier. A simplified finite element model is established to develop the lateral force-displacement relationship under cyclic loading. Additionally, a theoretical model based on the matrix displacement method and the virtual work principle is proposed to calculate the lateral force-displacement skeleton curve. The rationality and reliability of the theoretical model are validated by the satisfactory agreement observed between the numerical and theoretical results. Furthermore, a series of parametric analyses are conducted to discuss the effects of key parameters. The outcomes of this work can serve as a reference for further development of the design method for the innovated pier.