Buildings In Earthquake-prone Areas Research Articles

Seismic Vulnerability and Retrofit Alternatives for Typical Soft-story Buildings in Earthquake Prone Areas

More than 300 buildings were severely damaged during the 19 September 2017 earthquake (Mw = 7.1) occurred in Morelos, Mexico. One of the most common structural deficiencies detected was the use of ground level parking that produced soft-story buildings. These structures suffered severe damaged or collapsed. A field visit after the earthquake allowed to collect information about typologies of the damaged buildings and a great number of seismic ground motions. This study analyzes the seismic capacity and demands of typical existing building with a soft-story structure, based on the information collected in Mexico City, and subjecting the building to a family of real accelerograms recorded in this area during the earthquake occurrence. To enhance the seismic capacity of these structures, and to reduce their seismic vulnerability, a retrofit technique based on the addition of energy dissipation devices is analyzed. Results show the most efficient retrofit techniques and the strength and stiffness parameters required to improve the expected seismic behavior of this type of structures, and their applicability to mitigate damage in future earthquakes.

Performance-Based Seismic Design of High-Rise Buildings: Incorporating Nonlinear Soil-Structure Interaction Effects

This project aims to understand better how to incorporate nonlinear soil-structure interaction (SSI) effects into high-rise building performance-based seismic design approaches. The primary goals are to determine how important it is to include nonlinear SSI effects, create integration methods for them, and analyze how they affect seismic resilience. In terms of methodology, the study uses case studies and an analysis of current literature to show real-world applicability. Important discoveries highlight how critical nonlinear SSI analysis is for precisely forecasting structural reactions, locating weaknesses, and creating focused mitigation strategies. The policy implications emphasize the necessity of modern building regulations, research and development expenditures, and advancements in site characterization methods to facilitate the implementation of performance-based design methodologies. To improve the resilience and safety of high-rise buildings in earthquake-prone areas, this study's findings highlight the significance of considering nonlinear SSI effects during seismic design procedures.

Pemeriksaan Material pada Pembangunan Rumah Non-Engineered di Daerah Rawan Gempa Dusun Serut, Palbapang Kabupaten Bantul, Yogyakarta

Bantul Regency is a region with high level of seismic activity in Indonesia. Buildings that have the highest risk of collapse to earthquake are non-engineered buildings or residential buildings built without planning or not according regulation. This study aims to know contruction practices and material examination on non-engineered buildings in earthquake prone areas in accordance with the Indonesian National Standard. The object research is the construction of non-engineered building in Serut Village, Palbapang, Bantul Regency. The testing of material construction materials include: concrete test, reinforcing steel test and bricks test. the material are tested on the laboratory of Universitas Muhammadiyah Yogyakarta. The observations and measurements to the practices of construction consist of: concrete sloof with size 15 × 20 cm with the main reinforcement 4O12 and beugel reinforcement O6-150; column with size 10 × 15 cm with main reinforcement 4O10 and beugel reinforcement O6-150; the concrete mixture is made manually with a composition 1 cement: 3 sand: 2 gravel; Brick size 4.35 cm x 12.036 cm x 23.902 cm class criteria M-6 module. Laboratory material test results showed: steel reinforcement diameter O 10 mm obtained tensile strength (fy) 401.52 Mpa; O12 mm diameter obtained tensile strength (fy) 393,736 M.Pa; concrete have average compressive strength of 181 kg/cm 2 ; brick test have average compressive strength of 20.03 kg/cm 2 . The conclusion of contruction practices on non-engineered buildings in earthquake prone areas are adequate on major earthquake, the quality of construction concrete and reinforcing steel are fulfilling the criteria and requirements of the Indonesian National Standard, but quality of material brick is not adequate standar.

Mechanical characterization of a pre-fabricated connection system for cross laminated timber structures in seismic regions

This paper focuses on the point-to-point X-RAD connection system for the construction of cross laminated timber buildings in earthquake prone areas. Tests on X-RAD connectors subjected to “shear-tension” and “shear-compression” loading configurations are presented as supplement to the experimental data provided in previously published research. Tests aimed at characterizing the behavior of timber walls assembled with the system and loaded by lateral force are also reported. A capacity domain that allows for quick safety checks for any given load combination on the connector was derived from the experimental outcomes and is presented herein. An extremely simplified, yet effective numerical approach (the connector behavior is reproduced by 3-link elements) is proposed and compared with the experimental evidence. The 3-link model was able to reproduce with sufficient accuracy both, the elastic and post-elastic response of the walls. In the discussion section, particular attention is given to the system capability of dissipating energy and exhibiting ductile behavior.

A capacity curve model for confined clay brick infills

Experimental studies have proven that clay brick infills, confined with carbon-fiber-reinforced polymers (CFRP) in reinforced concrete (RC) frames, have some advantages in terms of stiffness, strength, energy dissipation capability and damage intensity. Owing to these advantages, existing infill walls in RC frames may be retrofitted with CFRP strips, especially in low-rise buildings in earthquake-prone areas. There is a gap in the literature concerning their behavior model, for use in structural analysis. A piecewise linear capacity curve model called “DUVAR” is proposed here, which estimates the envelope of force-vs.-displacement hysteresis, depending on the data compiled from the literature and the completed experimental studies. A nonlinear shear spring element is utilized in the model to represent the bare and retrofitted infills. The ultimate shear strength and the corresponding displacement, the ratio of cracking stiffness to initial stiffness, the ratio of ultimate strength to cracking strength, and the ductility ratio are the five key parameters of the model. The model is validated against the experimental results of two sovereign studies. Finally, the model is employed in the performance evaluation of an existing three-story RC building to exemplify its straightforward application.

Ambient vibration test of building base slab for different ground conditions

It is very important to know the dynamic behavior of base slabs of buildings in earthquake prone areas. The slabs are generally assumed as a rigid diaphragm in structural analysis and design. But their response is considerably affected from ground condition. In this study, the dynamic characteristics of a scaled base slab are determined for different ground conditions. The dimensions of the base slab model are 150cm long, 100cm wide and 5cm thick. This model is designed to be smaller than 20times from an actual building base. The base slab model is tested for the ground conditions of sand, gravel and clay–silt mixture by ambient vibration test. The dynamic characteristics, such as natural frequencies, modal damping ratios, mode shapes, are identified from collected signals by Operational Modal Analysis method. The first five modes are taken into consideration to compare the effect of ground conditions on the dynamic characteristics. It is observed that the natural frequencies, mode shapes and modal damping ratios are considerably affected from ground conditions. The highest natural frequency is obtained for the gravel ground case. The lowest natural frequency is identified for the clay–silt mixture ground case. The mode shapes changed randomly in each case. But the main modal behaviors are vertical mode and bending modes.

Simulation of strong ground motion due to great earthquake in the central seismic gap region of Uttarakhand Himalaya

Uttarakhand Himalaya in India lies in the central seismic gap region identified by Khattri and Tyagi (Tectonophysics 96:281–297, 1983). Most of the area in Uttarakhand state has been placed under zone V (the highest seismic zone) and zone IV (second highest seismic zone) of the seismic hazard map published by Bureau of Indian standard, Govt. of India (BIS in Indian standards code of practice for earthquake resistant Design of Structures, Indian Standards Institution, New Delhi, 2002). Some of the thrust/faults in the region manifest evidence of neotectonics and recurrent seismicity (Valdiya and Pant in Indian Nat Sci Acad 112–117, 1986; Valdiya in Geodynamics of NW Himalaya Gondwana Research Group Memoir 1999; Thakur in Curr Sci 86(II):1544–1560, 2004; Paul et al. in Seismotectonic implications of data recorded by DTSN in the Kumaon region of Himalaya 2004). On the basis of strain accumulation, Bilham et al. (Science 293:1442–1444, 2001) suggested a future magnitude of M ≥ 8 in this region. Therefore, a great earthquake along main central thrust in the central seismic gap region has been modeled using semi-empirical technique of Joshi and Mohan (J Seismol 12:35–51, 2008). For modeling great earthquake, the shear wave quality factor \( Q_{\beta } \left( f \right) = 30f^{1.45} \) (Joshi et al. in J Earthq Technol 47(1):508, 2010) has been used for Pithoragarh region of Kumaon Himalaya. The strong-motion parameters [peak ground acceleration (PGA), spectral acceleration, and normalized spectral acceleration] are computed at five stations (Sobla, Didihat, Munsiari, Dharchula, and Pithoragarh) in Uttarakhand Himalaya. The maximum PGA of the order of “2g” is computed due to scenario great earthquake in the region at Sobla station. Such type of study is quite helpful for seismic-resistant designs of the buildings in earthquake-prone areas and is essentially required in Uttarakhand Himalaya.

Equivalent frame model and shell element for modeling of in-plane behavior of Unreinforced Brick Masonry buildings

Although performance based assessment procedures are mainly developed for reinforced concrete and steel buildings, URM (Unreinforced Masonry) buildings occupy significant portion of buildings in earthquake prone areas of the world as well as in IRAN. Variability of material properties, non-engineered nature of the construction and difficulties in structural analysis of masonry walls make analysis of URM buildings challenging. Despite sophisticated finite element models satisfy the modeling requirements, extensive experimental data for definition of material behavior and high computational resources are needed. Recently, nonlinear equivalent frame models which are developed assigning lumped plastic hinges to isotropic and homogenous equivalent frame elements are used for nonlinear modeling of URM buildings. The equivalent frame models are not novel for the analysis of masonry structures, but the actual potentialities have not yet been completely studied, particularly for non-linear applications. In the present paper an effective tool for the non-linear static analysis of 2D masonry walls is presented. The work presented in this study is about performance assessment of unreinforced brick masonry buildings through nonlinear equivalent frame modeling technique. Reliability of the proposed models is tested with a reversed cyclic experiment conducted on a full scale, two-story URM building at the University of Pavia. The pushover curves were found to provide good agreement with the experimental backbone curves. Furthermore, the results of analysis show that EFM (Equivalent Frame Model) with Dolce RO (rigid offset zone) and shell element have good agreement with finite element software and experimental results.

Parameterization and Evaluation of Seismic Resistance within the Context of Architectural Design

This paper explores and discusses the possible relations between the architecture and seismic resistance of buildings. The first part of the paper stresses the practical importance of earthquake resistance in every building built in earthquake prone areas. Further on it is shown that the earthquake resistance in architectural expression can be dealt in hidden or concealed principles or on the other hand in revealed or emphasized ways. The paper hypothesize that the architectural design, which to a certain level reflects an earthquake threat, might provide a better designs with stronger architectural identity for buildings in earthquake-prone areas. In this context it summarizes the term “earthquake architecture”, which is defined as particular approach to design of buildings in architecture in a way which draws the inspiration from earthquake engineering. Such an approach might be one of the best responses of the architects (in cooperation with structural engineers and earthquake specialists) to the earthquake threats. In the second part of the paper the proposed method for recognition and evaluation of architecture in the context of earthquake resistance is presented. Using this evaluation method, it is possible to classify buildings at several different levels of “earthquake architecture”. Case study of three comparable competition projects is presented as example of using this method to evaluate the architectural design in the context of seismic resistance, and at the same time, to indicate the ways in which architecture can play its role part within earthquake resistant design.

Effect of Friction on Unbonded Elastomeric Bearings

This paper describes a theoretical analysis of a type of thermal expansion bridge bearing which could be used as a lightweight low-cost elastomeric seismic isolator for application to housing, schools, and other public buildings in earthquake-prone areas of the developing world. The analysis covers the effect of the frictional resistance of the supports on the vertical stiffness of this type of isolator. The most important aspect of these bearings is that they do not have end plates, which reduces their weight, but also means that they are not bonded to the upper and lower support surfaces and are held in place only by friction. This at first sight might seem to be a deficiency of this design, but it has the advantage that it eliminates the presence of tensile stresses in the bearings. It is these tensile stresses and the bonding requirements that arise from them that lead to the high costs of conventional isolation bearings. A theoretical analysis of the response of these bearings to vertical load shows that slip between the unbonded surfaces and rigid supports above and below can have a significant influence on the vertical stiffness and the internal pressure distribution.

Damage detection of a steel–concrete composite frame by a multilevel approach: Experimental measurements and modal identification

AbstractStructural Health Monitoring (SHM) and Experimental Modal Analysis (EMA) have revealed to be really efficient tools for the damage detection of structures and structural elements in many engineering fields (Shock Vib. Dig. 1998; 30(2):91–105; Philos. Trans. R. Soc. A 2007; 365(1851):303–315; Mech. Syst. Signal Process. 2003; 17(1):133–142; Philos. Trans. R. Soc.: Math. Phys. Eng. Sci. 2001; 359(1778): 131–149; Struct. Control Health Monit. 2006; 14:1083–1100; Mech. Syst. Signal Process. 2004; 17(1): 83–89). Unfortunately the great variety of morphologies, construction materials and structural schemes makes these techniques not easily applicable to buildings, due to inherent problems related to the location and the extent of damage, the sensitivity of the dynamic response to damage, the choice of damage indexes to be used, the sensors' location, etc.On the other hand, the modern seismic capacity design of buildings in earthquake‐prone areas tends to locate dissipative zones in well‐determined portions of structures (CEN, European Committee for Standardization, EN 1998‐1. Eurocode 8: Design of Structures for Earthquake Resistance. Part 1: General Rules, Seismic Actions and Rules for Buildings, European Community, Brussels, Belgium, 2005); thus, the application of vibration‐based damage detection techniques to earthquake‐resistant structures seems to be very promising even if nowadays there are only few studies on these arguments.The present paper reports the experiences of a vibration‐based damage identification study applied to a steel–concrete composite frame structure, suitably designed to be high ductile according to Eurocode 8 and localizing the seismic energy dissipation in the beam‐to‐column joints. The structure was subjected to series of pseudo‐dynamic (PsD) and cyclic tests with increasing peak ground acceleration at the European Laboratory for Structural Assessment of Joint Research Centre at Ispra (VA, Italy). The damaging phenomena, caused by PsD tests, were assessed and quantified by means of a multi‐level vibration‐based approach suitably designed in order to evaluate the changes in the global dynamic structural response and to experimentally estimate the reduction in joint stiffness. Copyright © 2008 John Wiley & Sons, Ltd.

Use of copper shape memory alloys in retrofitting historical monuments

The potential use of Cu-based shape memory alloys (SMA) in retrofitting historical monuments is investigated in this paper. This study is part of the ongoing work conducted in Tunisia within the framework of the FP6 European Union project (WIND-CHIME) on the use of appropriate modern seismic protective systems in the conservation of Mediterranean historical buildings in earthquake-prone areas. The present investigation consists of a finite element simulation, as a preliminary to an experimental study where a cantilever masonry wall, representing a part of a historical monument, is subjected to monotonic and quasi-static cyclic loadings around a horizontal axis at the base level. The wall was retrofitted with an array of copper SMA wires with different cross-sectional areas. A new model is proposed for heat-treated copper SMAs and is validated based on published experimental results. A series of nonlinear finite element analyses are then performed on the wall for the purpose of assessing the SMA device retrofitting capabilities. Simulation results show an improvement of the wall response for the case of monotonic and quasi-static cyclic loadings.

Seismic vulnerability assessment of a historical building in Tunisia

A methodology for the seismic vulnerability assessment of historical monuments is presented in this paper. The ongoing work has been conducted in Tunisia within the framework of the FP6 European Union project (WIND-CHIME) on the use of appropriate modern seismic protective systems in the conservation of Mediterranean historical buildings in earthquake-prone areas. The case study is the five-century-old Zaouia of Sidi Kassem Djilizi, located downtown Tunis, the capital of Tunisia. Ambient vibration tests were conducted on the case study using a number of force-balance accelerometers placed at selected locations. The Enhanced Frequency Domain Decomposition (EFDD) technique was applied to extract the dynamic characteristics of the monument. A 3-D finite element model was developed and updated to obtain reasonable correlation between experimental and numerical modal properties. The set of parameters selected for the updating consists of the modulus of elasticity in each wall element of the finite element model. Seismic vulnerability assessment of the case study was carried out via three-dimensional time-history dynamic analyses of the structure. Dynamic stresses were computed and damage was evaluated according to a masonry specific plane failure criterion. Statistics on the occurrence, location and type of failure provide a general view for the probable damage level and mode. Results indicate a high vulnerability that confirms the need for intervention and retrofit.

EVALUATION OF THE SEISMIC PERFORMANCE OF EXISTING RC BUILDINGS: I. SUGGESTED METHODOLOGY

A reliable estimate of the actual capacity and deformability of existing reinforced concrete buildings in earthquake prone areas is essential in pre- or post-earthquake interventions. This study is concerned with the evaluation of the structural overstrength, the global ductility and available behaviour factor of existing reinforced concrete buildings, designed and constructed according to past generations of earthquake resistant design codes. For the estimation of these global performance characteristics different failure criteria are incorporated in a methodology established to predict the failure mode of the buildings. As an application, a typical five-storey building of the 1960s, designed according to the prevailing design codes, is selected and analysed in the inelastic range. Both bare and infilled structural forms of this building are studied. For this structure, the plastic hinge rotation capacity is the critical failure criterion. The same structure, designed according to current design codes, is re-evaluated using the same methodology, in order to calibrate the procedure and to compare the static and dynamic inelastic performances of the two frames. The results indicate that existing buildings exhibit higher overstrength than their contemporary counterparts, but with much reduced ductility capacity. Perimeter infill walls correct for their lack of ductility by augmenting their stiffness and their overall lateral resistance. The methodology is subsequently applied to a larger inventory of typical existing buildings, as described in a companion publication.

Seismic evaluation and innovative retrofit of a historical building in Tunisia

This paper summarizes work conducted within the framework of a European Commission funded project on the use of appropriate modern seismic protective systems in the conservation of Mediterranean historical buildings in earthquake-prone areas. The case study is the one-and-a-half-century-old Palace of Ksar Said, located near the Capital of Tunisia. At the center of the palace, a collection of portraits and furniture are preserved in a room of great architectural and historical value which is the most precious part of the building to be protected. Ambient vibration tests were conducted to measure the acceleration at selected locations of the building. Output-only modal identification techniques were applied to extract the modal signature of the structure. A finite element model of the palace was elaborated based on the measured characteristics of stone and mortar and updated according to its measured vibratory response. Seismic vulnerability assessment of the building was carried out via three-dimensional time-history dynamic analyses of the structure. Results indicate a high vulnerability that confirms the need for intervention. A retrofit scheme is proposed that consists of a steel frame directly, attached to the portrait room structure with added fluid viscous dampers. Vulnerability assessment of the retrofitted building reveals a substantial improvement especially in the vicinity of the portrait room. Copyright © 2004 John Wiley & Sons, Ltd.