High Seismic Area Research Articles

“Guidelines for the classification and management of risk, for the evaluation of safety and for the monitoring of existing bridges”. An automatic calculation model of the seismic attention class optimized for the use of cloud computing services.

The Italian road network is complex due to the particular orography of the territories crossed, often characterized by areas of high seismicity. In addition, bridges and viaducts present a peculiar state of decay mainly due to their remote period of construction. The situational picture is also difficult to understand due to the absence or non-uniformity of infrastructural safety management systems (SMS). To fill this gap, the Italian Higher Council of Public Works has issued guidelines for risk management, that allow the classification, safety assessment and monitoring of existing bridges. The central focus of the new approach is the identification of the overall attention class, which allows to move from assessments on a territorial scale to safety assessments on a limited number of bridges. This work focuses on the development of a prototype for the automatic calculation of the seismic attention class that has been optimized for cloud computing services. In particular, a standardized procedure has been defined that guides the operator in the evaluation of the seismic attention class. The model also allows to carry out the validation of other software. Finally, the prototype created is easily extensible to other attention classes which are therefore manageable independently in the perspective of modular development of an open access and open source platform.

CONSTRUCTION SYSTEM SELECTION IN LOW-BED CAPACITY HEALTH BUILDINGS WITH FUZZY AHP IN EARTHQUAKE ZONES

Purpose: Reconstruction of health buildings that were heavily damaged after the earthquake has become an important issue in Turkey. The negative performance of the construction systems of health buildings after major earthquakes necessitates the evaluation of the building system (CS) options, which can create an alternative to the market, according to various criteria. The main purpose of the study is to develop a systematic basis for the CS of 1816 health institutions to be rebuilt within the scope of the UDSEP 2023 project and to decide between alternatives in Turkey. In this study, the example of a hospital with a low bed capacity (20 beds) was discussed. Method: In the application of the Methodology-Fuzzy Analytical Hierarchy Process (FAHP) method of the research, 40 expert opinions were taken at the stages of planning, construction and inspection of health buildings. Findings: Experts in various fields of the construction industry have determined that CS performance is the primary criterion and cost is the secondary criterion for healthcare buildings in high seismic hazard areas. Conclusion: Among the CS alternatives, Structural Steel Frame (SSF) was determined as the most suitable structural system for earthquake zones.

Structural Health Monitoring and Dynamic Identification of the Historical Town-Hall of Borgo Val di Taro

A good structural knowledge of heritage buildings is a key factor for their conservation and for the planning of retrofit interventions, especially in high seismic risk areas, like Italy. Within this context, structural health monitoring techniques, like those based on ambient vibrations under operating conditions, represent powerful tools for evaluating the dynamic behavior of existing structures. The presented methodology is particularly interesting for historic and monumental buildings due to its non-invasiveness. This work illustrates the installation of a monitoring system in the historical masonry Town-Hall of Borgo Val di Taro, dating back to the fifteen century, for its ambient vibration modal identification. The so collected data are then used for the construction of a refined numerical model for the simulation of the dynamic response of the building, and for the updating of its parameters. A comparison between numerical and experimental results is finally provided.

Effect of using Engineered Cementitious Composites (ECC) on failure behavior of flat slab-column connections

Load capacity and ductility are two key characteristics of the flat slab-column connection in high seismic areas. This study specifically examined the effect of strengthening layer thickness of Engineered Cementitious Composites (ECC) on punching shear strength and post punching behavior of flat slabs. The effect of the unbalanced moment, ECC thickness of the slab and the strengthening ECC layer on flat slab punching and post punching behavior were also investigated. Thirteen reinforced concrete flat slab specimens were made and examined. It was observed that the replacement of slab concrete with ECC increased the punching capacity and improved post-punching behavior without a large and sudden drop in load. In addition, the use of ECC as a strengthening layer for the flat slabs significantly increased the punching and post-punching shear strength capacities. The change in failure mechanism was observed from a sudden and abrupt failure to a ductile failure with high-energy absorption when more ECC layer thicknesses were used.

Tribological investigation on metal mating surfaces to explore real use conditions of a novel friction damper for seismic applications

The seismic rehabilitation of existing buildings is a strategic goal for many countries located in high seismic risk areas of the globe. Retrofit techniques based on energy dissipation by implementing additional mechanical dampers into the structure have proved to be very efficient. Among the others, friction-based dampers have revealed to be particularly simple and cheap; nonetheless, for this kind of device, the selection of mating surfaces set a crucial point. This paper shows the experimental investigation performed for the development of a novel Friction Damper (FD) using Pin-on-Disk (PoD) tests and highlights the main tribological aspects useful for the full-scale tests. PoD tests have been set to simulate the real use condition of the device in development under the action of subsequent earthquakes. Sliding surface’s material and machining processes have been selected taking into account the S355JR steel main body of the device in development, and the need of reducing the friction’s abrasive component and the particle formation during sliding. The experimental campaign has been addressed to highlight the influence of surface roughness, machining processes, additional treatment, and different coupling materials on Coefficient of Friction (COF) mean value and its statistical dispersion.

Influence of Tie Configuration on Seismic Behaviour of Ultra High Performance Concrete Columns

Ultra-High-Performance Concrete (UHPC) is one of the latest advances in concrete technology as it overcomes the shortcomings of conventional concrete such as low strength to weight ratio, high permeability, low tensile strength, low ductility, and volume instability. Confinement is capable of increasing capacity of the concrete structure to sustain large deformation without a substantial strength loss. The present study discusses the influence of tie configuration, percentage of longitudinal reinforcement and tie spacing in improving the confinement and behaviour of UHPC columns. In order to determine the behaviour of UHPC column, half scaled specimens of original short column with four different tie configurations were used. The configurations considered for the study included a double legged ties (A), welded ties with bars running centrally across the length and width (B), ties with inclined bars connecting two adjacent mid-points (C) and ties with bars connecting two adjacent sides at one-third distances (D). For the same tie configuration, the transverse reinforcement ratios are varied by changing the diameter of the ties. The specimens were tested under quasi static reverse cyclic loading under a constant axial load. The test results were represented and compared in terms of load-deflection envelope, ductility and cracking patterns. Tie configuration C exhibited better performance in stiffness and ductility, when compared with other configurations. For same parameters, “B” and “D” configuration displayed better behaviour than “A” configuration. This variation in performance was due to increase in transverse reinforcement percentage and the consequent effectiveness of core confinement. Transverse reinforcement percentage of “B” and “C” configurations is less than “D” configuration. The enhancements of properties of “B” and “C” configurations are better than “D” configuration. It was due to the effective core confinement of “B” and “C” configuration. For the same tie configuration, ultimate load, initial stiffness and relative ductility increases with increase in transverse reinforcement percentage. UHPC columns with “C” type tie configuration can effectively use in moderate and high seismic areas and its performance can be improved by increasing the transverse reinforcement ratio.

Experimental research on seismic behaviors of RC columns considering buckling of HRB600 longitudinal steel bars

The inelastic buckling of longitudinal bars and premature fracture that followed can always be observed in laboratory research and earthquake damage of reinforced concrete (RC) columns. The buckling deformation and accompanied fracture of HRB600 high-strength steel bars are more significant than those of conventional reinforcing bars, but the buckling properties of HRB600 reinforcement and the influence of premature fracture on the seismic performance of RC columns are far from clear. In this paper, low cyclic loading tests were conducted on six full-scale RC columns reinforced with HRB600 reinforcement by changing the slenderness ratios of longitudinal bars and the axial compression ratios of columns, and the lateral buckling displacements of longitudinal bars were measured by an identified method. Based on the lateral buckling displacements, the buckling behaviors of longitudinal bars were analyzed. It shows that cover concrete has a significant constraint effect on preventing buckling of HRB600 reinforcement. The inelastic buckling behaviors and premature fracture of HRB600 bars on the ultimate deformation capacity and ductility of RC columns were investigated according to the lateral buckling displacements and ductility coefficient. It is found that the increase of the slenderness ratio would cause larger buckling displacements making the local plastic deformation concentration and low-cycle fatigue damage of HRB600 reinforcement more serious, resulting in the premature fracture of longitudinal bars and decrease of ductility of RC columns. Furthermore, a series of individual bars accompanied by the RC columns were tested. Based on the average stress–strain curves, the effects of yield strength and slenderness ratio were discussed. Former researches of conventional longitudinal bars were involved to form a comparison group with HRB600 bars. The results indicate that the deformation capacity reserves of HRB600 reinforcement after 85% peak load were significantly lower compared with conventional bars. It is suggested to limit the application of RC columns reinforced with HRB600 longitudinal bars in high seismic intensity areas and improve the limitation on the slenderness ratio of high-strength steel bars.

Design procedure for orthogonal steel exoskeleton structures for seismic strengthening

The steel exoskeleton systems are widespread structures applied on the external perimeter of an existing building designed to absorb the horizontal actions providing at the same time useful support for energy efficiency upgrading and architectural restyling. The growing interest in the use of exoskeletons is due to the possibility of creating an integrated retrofit (structural, energetic, formal and functional), combining “structural safety” with the concepts of “deep renovation”. Among many solutions present in the literature, in the present work, the steel exoskeletons placed orthogonally to the facade of the existing building have been analysed; this structural typology has the advantage to allow rapid retrofit execution without interfering with the activities carried out within the existing structure. In this framework, the aim of the present work is the introduction of a detailed step-by-step design procedure for steel exoskeletons systems adopted for seismic retrofit of existing buildings looking also at the accessibility and operability aspects. Each step of the procedure was individually explained and it was applied for the design of a strengthening intervention on a real single-storey steel industrial building. The existing building is located in Nusco (Av, Italy) which is classified as in medium–high seismic intensity area which corresponds a peak ground acceleration (ag) equal to 0.238 g. Non-linear analyses were conducted to assess the existing structure’s performance as well as to verify the effectiveness of the strengthening solutions designed. The use of the exoskeleton systems allows to strongly increase both the elastic stiffness and the resistance of the investigated industrial building without interrupting its product activity.

Seismotectonics of Southern Calabria Terrane (South Italy)

Seismic data of earthquakes recorded during the last 40 years in southern Calabria have been compared with geological data in order to obtain a seismotectonic picture of the area. We sought for any possible correlation between the main regional tectonic structures, the distribution of earthquake hypocentres and the focal mechanism of earthquakes with magnitude (Ml)≥3. Studies of historical and recent seismicity and analysis of geological structures allowed to define the main shear strips on a regional scale. More than 2600 earthquakes with 1.5 ≤ Ml ≤ 4.5 have been considered. The focal mechanisms of earthquakes with Ml≥3 have been compared with the kinematics of known faults and used to give insight on the current active stress field. From the analysis carried out it was possible to expand the cognitive framework regarding the activity of the main tectonic structures present in the area. This study also served to identify areas of high seismicity which do not correspond to any evidence of tectonic structures on the surface, and areas where recognized tectonic structures have not shown any seismicity during the last decades. These cases could be the subject of future investigation in order to correctly assess the seismic hazard in Calabria. This task is important in the context of seismic hazard evaluation and mitigation.

Shake table test and numerical analyses of a thin-walled Cold-Formed Steel structure: Part 1 — Investigation of the structural skeleton without claddings

CFS structures are classified as structures with low ductility. Due to this, they are not recommended for medium to high seismic areas. The paper presents the results of a complex experimental program coupled with numerical investigations on the behavior of Cold Formed Steel (CFS) structures under seismic actions. The scaled-down model skeleton was made of DX51D+Z C-shaped 89 × 41 × 12 × 1 mm steel elements connected by 4.8 × 16 mm self-tapping screws (STS) and 5.5 × 25 mm self-drilling screws (SDS). This structure represents a replica of constructive solutions for single-story or one or two-storey structures that are frequently met in South-Eastern Europe, including highly active seismic areas.The main purpose of the research program is to gather both quantitative and, more importantly, accurate information regarding structural response to dynamic actions characterized by input accelerations equal in amplitude to the maximum values specified in seismic design codes, up to PGA = 0.40 g. The damage of the joints and the reduction in the structural stiffness due to cyclic loads, such as the ones produced by earthquakes, change the structure’s eigen period and significantly influence the structure’s response to seismic actions. Larger gravitational loads lead to more extensive damage of the joints. The developed numerical model based on the experimentally determined connection axial rigidity can offer accurate results in terms of the fundamental frequency of vibration, relative accelerations and displacements. However, for a more accurate capturing of the local damages and onset of failure mechanisms, more complex numerical models are needed, which take into account non-linear material behavior.The results presented in this paper help to design these structures as only the skeleton and serve as a starting point for future research work aimed to assess the influence of the sheathing on the global response of CFS structures to seismic actions. Additionally, research in the direction of improved joints with better energy dissipation properties is also pursued by the authors.

Generalized response spectrum analysis based computational morphogenesis for metal gridshells with buckling-restrained braces subjected to seismic loading

Structural morphogenesis is widely used as a parametric tool to find an optimal structural shape of shell structures for a prescribed objective function and a given design load. However, the current optimization methods are limited to finding a geometry under only a specific static load like the dead load or an equivalent static seismic load for predefined geometrical shapes, and so can not be applied to free-form gridshells. This poses a challenge to achieving an efficient free-form shell structure in high seismic hazard areas. This paper aims to resolve this by presenting a computational morphogenesis method to obtain form-found shell structures by considering the dynamic seismic loads and the response reduction effects of seismic energy-dissipating devices using generalized response spectrum analysis. The method was applied to optimize the buckling-restrained brace layouts on target spherical metal gridshell structures with different diameter-to-height ratios. The resulting form-found structures had an efficient roof geometry, along with an efficient damper layout (to prevent member buckling and the dropout of finishing materials). Dampers were found to be more efficient if placed in the (relatively heavy) supporting structure instead of the roof, and a flattened but locally bulged roof shape proved to be the most efficient in mitigating the seismic response. The generalized response spectrum analysis significantly reduced the computation time while evaluating the displacement response with sufficient practical accuracy, although it slightly underestimates the acceleration response if compared to the conventional nonlinear response history analysis results.

Seismic performance of continuous curved girder bridge with high pier in Maduo earthquake and characteristic analysis

PurposeThe purpose of this study is to explore the seismic damage mechanism of the Dayemaling Bridge during the Maduo earthquake and discuss the seismic damage characteristics of the high-pier curved girder bridge.Design/methodology/approachIn this study, the numerical simulation method is used to analyze the seismic response using synthetic near-field ground motion records.FindingsThe near-field ground motion of the Maduo earthquake has an obvious directional effect, it is more likely to cause bridge seismic damage. Considering the longitudinal slope of the bridge and adopting the continuous girder bridge form, the beam end displacement of the curved bridge can be effectively reduced, and the collision force of the block and the bending moment of the pier bottom are reduced, so the curved bridge with longitudinal slope is adopted.Originality/valueCombined with the seismic damage phenomenon of bridges in real earthquakes, the seismic damage mechanism and vulnerability characteristics of high-pier curved girder bridges are discussed by the numerical simulation method, which provides technical support for the application of such bridges in high seismic intensity areas.

State of the Art Review on Design of Steel Plate Shear Wall

Steel plate shear walls are rapidly becoming an appealing alternative in high seismic areas. The current research reviews the existing work on design and development of steel plate shear wall. The existing studies encompasses research on optimization of different design parameters of SPSW, materials of SPSW and various design configurations. The stability of these structures as lateral load resisting member is assessed using experimental and numerical techniques and presented in this review.

Seismic performance of prefabricated steel tube-confined concrete circular pier

In this study, a prefabricated steel tube-confined concrete (PSTC) circular pier with a bottom grouted sleeve connection was developed to correct some limitations in typical precast concrete (PC) piers, such as over-dense grouting sleeves and insufficient energy dissipation capacity, thus promoting their use in high seismic hazard zones. To validate the performance of the proposed design, four scale models of an actual circular bridge pier, including two PSTC, one PC, and one cast-in-place (CIP) specimens, were fabricated and their seismic response under cyclic loading was investigated via quasi-static experimental and numerical tests. The seismic performance indices, hysteretic energy dissipation characteristics, skeleton curve, flexural strength, stiffness degradation, residual displacement, and ductility of the different specimens were compared. The experimental and numerical results indicated that, compared with the CIP and PC circular piers, the flexural strength and energy dissipation capacity of the PSTC piers were significantly improved owing to the confinement provided by the steel tube to the concrete core, their ductility and initial stiffness effectively increased, and the pier body stiffness (pier body curvature) was more uniformly distributed. Moreover, parametric finite element analyses of the PSTC pier under low-cycle reciprocating load were used to determine the influence of the steel tube thickness and strength on the seismic performance of the pier. It was found that an increase in the thickness and strength of the steel tube also increases the flexural strength, yield load, yield displacement and initial tangent stiffness of the PSTC circular pier. Consequently, this study demonstrates that PSTC piers are reliable and suitable for prefabricated bridge construction in high seismic hazard areas.

The Evaluation of Double Story Building Considering Earthquake

Despite being one of the safest countries in the world with shallow earthquake hazards, Malaysia has experienced some minor earthquakes due to its proximity to neighboring countries like Indonesia and Filipina. High seismicity areas surround the nation on the west, south, and east. Furthermore, only about one percent of Malaysia's buildings are earthquake resistant, and Malaysia needs to think of ways to deal with it by constructing more seismic resistance buildings. This research aims to study the implication and cost consequences of the double-story building when an earthquake occurs. In this study, the evaluation of double-story buildings will be investigated by comparing the structural and cost implications of double-story buildings with seismic and without seismic loads. The analysis of an architectural drawing of a typical double-story building will be carried out as part of the research. It is observed that buildings considering earthquake design have more significant structural and cost implications when compared with buildings without considering earthquake design. The study's findings are expected to provide earthquake design criteria for double-story buildings in Malaysia and its neighboring countries to ensure community safety and reduce the structural and cost effects of the construction of double-story buildings with earthquake resistance.

Improving seismic behaviors of precast segmental piers with bonded prestressed tendons

Precast segmental bridge piers attract engineers due to the strengths of accelerated construction, reduced traffic disturbance and enhanced quality control. However, their widely applications in high-seismicity areas are hindered, for the insufficient capacities of energy dissipation. In this study, precast segmental piers’ seismic behaviors were investigated, focusing on the connection of ‘grouted sleeves/bonded tendons’. To this end, four piers were cyclically loaded, of one cast-in-place pier, one precast segmental pier, and two prestressed precast segmental piers. Among them, Benefits of bonded tendons were evidenced, in terms of lateral strength, ductility, energy dissipation capacity and residual drift. Of particular, bonded tendons prevented the shear-induced slip between the shaft and footing segments. Enlightened from observations, cyclic dowel-friction effect is proposed and implemented within a zero-thickness sliding spring in the finite element model, capable of capturing the shear-induced joint slip. Furthermore, seismic vulnerability assessments of the bridge piers are obtained in terms of fragility curves, by performing incremental dynamic analyses. In addition, the effects of bonded or unbounded tendons are also discussed. Two criteria are adopted to define the limit states, namely displacement ductility and residual drift. It is suggested that bonded tendons could significantly ameliorate the fragility curves of precast segmental piers. HIGHLIGHTS Four bridge piers were cyclically loaded, with various prestressing levels. A reliable fiber-based model was constructed, considering shear-induced slip at the segmental joint for the first time. Seismic vulnerability assessments were performed to quantify the piers’ behaviors.

Structural and mechanical performance of adobe with the addition of high-density polyethylene fibres for the construction of low-rise buildings

Adobe bricks have been used in construction since ancient times, due to their low cost, good performance and the ease of assembly and elaboration of these elements in construction. However, the low ductility and resistance of adobe could harm the structural behaviour of buildings, especially taller buildings. The addition of additives, in the form of abundant high-density polyethylene (HDPE) fibres, could improve the mechanical properties from a seismic and structural point of view. These improved adobes could replace factory bricks, whose mechanical deficiencies are similar to adobe (stiffness and flexural strength), and they could reduce the high cost of buildings today. This work analyses and compares the performance and structural performance that these elements acquire in framed buildings, compared to traditional adobe, incorporating different percentages of high-density polyethylene fibres (HDPE) in low-rise buildings (of 2 and 4 storeys), which are very abundant in areas of high seismicity. For this, models of structural frames are analysed, adding adobe walls using the mechanical results carried out in a laboratory at the University of Talca (Chile). The addition of a small percentage (0.6% and 1.2%) of HDPE in the traditional adobe, improves the ductility and the structural performance of the frames.

Seismic Stability and Liquefaction Analysis of Tailings Slope

The potential for liquefaction and slope stability of a thickened tailings slope, within a storage facility located on the shore of a natural glacial lake in Tehran, is evaluated based on field and laboratory testing. The tailings slope has the particularities of being located in a high seismicity area and founded on conventional slurry tailings from the previous operation of the facility. The in-situ state of the thickened tailings was investigated through field tests, including Standard Penetration Tests (SPT) and Cone Penetration Tests with pore pressure measurement (CPTu). Samples collected during the field investigation were used in an extensive geotechnical laboratory program to determine index properties and strength parameters for the thickened tailings. Testing included a series of isotropically consolidated undrained and drained (CIU and CID) triaxial tests, as well as a simulation of the consolidation process within the tailings through oedometer tests. The liquefaction potential was evaluated using the data from the CPTu testing, while slope stability was assessed using the limit equilibrium approach for an infinite slope, considering the variation of shear strength with the degree of consolidation (void ratio) of the tailings from a critical state approach. Based on the results of the liquefaction potential and the slope stability assessment, a design approach is suggested for facilities under similar conditions.

Seismic behavior of an innovative equivalent monolithic precast shear wall under low and high axial load ratios

To meet the demands for the axial load and shear capacity of prefabricated reinforced concrete shear walls located at lower floors in high-rise buildings in high seismic intensity area, an innovative equivalent monolithic precast shear wall (labeled as EMPSW) was proposed by introducing X-shaped steel plate bracings and high ductility hidden column in this research. And seismic behavior of two EMPSWs under low and high axial load ratios (ALRs) were evaluated by quasi-static loading tests. The experimental phenomenon showed that EMPSWs under low and high ALRs presented similar fully developed and wide distributed cracks, whilst the ultimate draft ratios and ductility coefficients of specimens all met the specification requirements, exhibiting good lateral resistance through ductile damage for EMPSWs under different ALRs. Also, the increase of ALRs could improve the load carrying capacity and initial stiffness, but had no benefit on the energy dissipation and deformation capacity of EMPSW. Then, a reasonable strut-and-tie model (STM) was applied and verified to be well suitable for predicting the mechanical behavior of EMPSW. Besides, further investigations regarding the influence of critical parameters were implemented by finite element analysis (FEA). The FEA results illustrated that a higher ALR was beneficial for load-bearing capacity but had a significant negative impact on deformation capacity, thus the test ALR for EMPSW should be controlled within 0.5 in engineering practice. The volumetric ratio of X-shaped steel plate bracings and longitudinal reinforcement ratio in hidden column had a positive effect on capacity, but their contributions decreased as ALR increased.

Experimental investigation and numerical modeling of rocking cross laminated timber walls on a flexible foundation

AbstractWith recent developments of engineered wood products such as cross laminated timber, mass timber buildings in areas of high seismicity are becoming feasible and offer benefits such as faster construction and unique architectural features. It has also opened the door to creating seismically resilient lateral systems that sustain minor and reparable damage during large earthquakes. This paper presents a numerical modeling procedure for mass timber rocking wall lateral system with distributed spring elements to model base rocking. This modeling technique was validated by comparing the behavior with results from the full‐scale two‐story shake table test on a mass timber building with coupled CLT rocking walls completed as part of the NHERI TallWood Project. Although the lateral system performed better than expected during testing, it was determined that the flexibility of the foundation actually limited damage to the rocking wall panels. By adjusting the numerical model to represent a rigid foundation boundary condition, it was determined that the wall system would have experienced more damage, but would have still met design performance objectives had it been tested on a rigid foundation.