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The seismic response evaluation of cold-formed steel-framed nonstructural architectural components was investigated in an experimental campaign carried out within of the research study agreement between Knauf Gips KG and the Department of Structures for Engineering and Architecture of the University of Naples “Federico II”. The main objective of this research was to investigate the seismic performance of drywall nonstructural systems, i.e. cold-formed steel-framed indoor partition walls, outdoor façade walls and suspended ceilings. The present paper deals with the dynamic shake table tests. The tests were carried out on two different typologies of prototypes (Type 1 and Type 2) for a total number of five specimens. The influence on seismic response of basic and enhanced anti-seismic solutions, corresponding to the use of fixed or sliding connections at the walls and ceilings perimeter, was investigated. The seismic response evaluation of the systems under investigation has been performed according to ICBO-AC156 code with different levels of increasing intensity. Test results have been analysed in terms of dynamic identification, dynamic amplification, and fragility curves. Test results highlight that enhanced solutions have a better seismic response than basic solutions and indoor partition walls have a higher seismic fragility than outdoor fa ade walls.

Shake table tests are particularly indicative to assess dynamic properties and seismic response under earthquakes in the case of a new building structure. In last years the University of Naples was involved in the research project named "Energy Efficient LIghtweight-Sustainable-SAfe-Steel Construction" (Project acronym: ELISSA), which was devoted to the development and demonstration of enhanced prefabricated lightweight CFS skeleton/dry wall constructions with improved antiseismic properties. Within the ELISSA project, in order to evaluate the global building seismic response, shake table tests on a full-scale two-storey building, named “ELISSA mockup”, were carried out. The mockup was tested in two different conditions. In the first condition the mockup included mainly structural components of walls, floors and roof, whereas in the second condition it was completed with all nonstructural components. This paper presents the testing program and the obtained results in terms of dynamic identification (fundamental period and damping ratio) and earthquake performance (global lateral response, building drift, acceleration amplification, diaphragm response, and observed damage).

The seismic damage of non-structural components could involve functionality interruption of the most affected buildings and substantial economic losses. Therefore, a cooperation be-tween the University of Naples "Federico II" and KnaufGips KG Company, aimed to the knowledge of seismic response of lightweight steel drywall nonstructural components was car-ried forward. The paper presents the dynamic tests on shaking table of protoypes composed by interior partition walls, exterior façade walls and suspended continuous ceilings. The influ-ence on seismic response of basic and enhanced anti-seismic solutions, corresponding to the use of fixed or sliding connections at the walls and ceilings perimeter, was investigated. The seismic response in terms of damage occurrence was also evaluated by fragility curves, which show that enhanced solutions have a better seismic response than basic solutions and interior partition walls have a higher seismic “fragility” than exterior façade walls.

The seismic damage of non-structural components could involve functionality interruption of the most affected buildings and substantial economic losses. Among non-structural components, the lightweight steel ceiling-partition wall systems can represent a significant investment in the construction sector. Nevertheless, the proper seismic design of these systems plays a secondary role within the current structural design, by leading to a lack of specific design provisions. Since the behaviour of these systems cannot be easily simulated with traditional analysis methods, the experimental characterization is an effective procedure. For these reasons, a specific research activity was started over last few years at the University of Naples Federico. The main objective of the research is to investigate the seismic performance of lightweight steel drywall non-structural building components, i.e. partition walls and suspended continuous ceilings made of lightweight steel profiles sheathed with gypsum-based panels. The presented paper describes and discusses particularly the in-plane quasi-static reversed cyclic tests carried out on lightweight steel drywall partition walls. The obtained results could be considered a starting point for developing the in-plane seismic design assisted by testing of lightweight steel drywall partition walls according to European prescriptions.

The unconventionality of the cold-formed steel (CFS) structures raised, in recent times, a lot of interest from many national and international companies resulting in the promotion of ex-perimental activity with the main aim of investigating the seismic behaviour of these systems. In this perspective, an important cooperation between the University of Naples “Federico II” and Lamieredil S.p.A. company started in the last years. The research project included an ex-tended experimental campaign, involving shake-table tests on two three-storeys prototypes in reduced scale (1:3). The investigated seismic-resistant systems were CFS strap-braced stud walls, designed as low dissipative. The present paper illustrates the design of prototypes and the development of a numerical model with OpenSees software for the simulation of seismic response.

The European project named "Energy Efficient LIghtweight-Sustainable-SAfe-Steel Construction" (Project acronym: ELISSA) is devoted to the development and demonstration of cold-formed steel (CFS) modular systems. In particular, these systems are nano-enhanced prefabricated lightweight steel skeleton/dry wall construction with improved thermal, vibration/seismic and fire performance, resulting from the inherent thermal, damping and fire spread prevention properties. The different building performances are studied and improved by means of experimental and numerical activities organized on three scale levels: micro-scale, meso-scale and macro-scale. In particular, the evaluation of the seismic performance is carried out at the University of Naples by means tests on connections (micro), seismic-resistant systems (meso) and full-scale two stories house prototype (macro). From a structural point of view, the system is a sheathed-braced CFS solution, in which the seismic resistant elements are made of CFS stud shear walls laterally braced by gypsum-based panels. In the adopted solution, the sheathing panels are attached to the CFS frame by means of ballistic nails, whereas clinching points are used for steel-to-steel connections. The present paper illustrates the results of meso-scale tests performed on four full scale shear walls, in which the influence of the aspect ratio, the type of loading and the effect of finishing was investigated.

L’attuale interesse del mercato delle costruzioni sembra essere sempre più indirizzato a soluzioni integrate che rispondano ad una molteplicità di requisiti prestazionali, quali buon comportamento fisico/meccanico, facilità e velocità di esecuzione, elevato livello qualitativo e, fattore sempre più importante, economia del ciclo di vita. In quest’ottica, i sistemi realizzati “a secco” mediante l’impiego di profili in acciaio zincato formato a freddo si configurano come soluzioni molto competitive, sia in ambito di applicazioni strutturali, che nel campo delle soluzioni non strutturali. In questo contesto, si inquadra la recente attività di ricerca in corso presso l’Università degli Studi di Napoli “Federico II”, svolta in collaborazione con la multinazionale Knauf Gips KG, sul comportamento sismico di componenti non strutturali che si basano sull’utilizzo di profili in acciaio zincato formato a freddo, quali pareti di partizione e controsoffitti sospesi continui, di cui in questa memoria si presentato i principali aspetti

Il danneggiamento sismico di componenti non-strutturali in caso di evento sismico può com-portare l’interruzione di funzionalità degli edifici interessati e perdite economiche notevoli. Tra i componenti non-strutturali, i sistemi costituiti da partizioni e controsoffitti rappresentano un investimento significativo nel settore delle costruzioni. Tuttavia, la questione dell’adeguata progettazione sismica di tali sistemi riveste ancora un ruolo di secondaria importanza nell’ambito della progettazione strutturale, riflettendosi in notevoli carenze normative. Poiché il comportamento di tali sistemi non può essere facilmente simulato tramite i tradizionali me-todi di analisi, la caratterizzazione sperimentale può rappresentare l’unica procedura efficace. In questo scenario si inquadra la collaborazione tra la KnaufGips KG e l’Università di Napoli “Federico II”, finalizzata alla conoscenza della risposta sismica di sistemi non-strutturali light-weight steel, ossia di partizioni e controsoffitti continui realizzati con profili cold-formed e rivestiti con pannelli in cartongesso. La presente memoria illustra e discute nello specifico le prove monotone quasi-statiche e le prove di identificazione dinamica fuori piano condotte su pareti di partizione, illustrandone i principali risultati ottenuti.

Past earthquakes have shown that the damage to non-structural elements can severely limit the functionality of most affected buildings and cause substantial economic losses compared to structural damage. Among the non-structural components, the ceiling-partition systems represent a significant investment in construction sector. Nevertheless, their seismic performance is poorly understood, because information and specific guidance are very limited. Since the behaviour of these systems cannot be easily simulated with traditional structural analysis, seismic design by testing is an effective procedure. For these reasons, an experimental campaign has been planned at the University of Naples Federico II with the main aim to characterize the seismic response of different Knauf partition walls and suspended continuous plasterboard ceilings. This paper presents and discusses an experimental campaign involving out-of-plane quasi-static monotonic tests and step-relaxation tests on partition walls, mainly devoted to develop out-of-plane seismic design by testing of Knauf drywall partitions.

The European project named "Energy Efficient LIghtweight-Sustainable-SAfe-Steel Construction" (Project acronym: ELISSA) is devoted to the development and demonstration of cold-formed steel (CFS) modular systems. In particular, these systems are nano-enhanced prefabricated lightweight steel skeleton/dry wall construction with improved thermal, vibration/seismic and fire performance, resulting from the inherent thermal, damping and fire spread prevention properties. From a structural point of view, the system is a sheathed-braced CFS solution, in which the seismic resistant elements are made of “Cocoon” CFS stud shear walls laterally braced by “Knauf” gypsum-based panels. The project plans the study of the different physical perfomance on the basis of three levels: micro-scale, meso-scale and macro-scale. This paper presents the micro-scale experimental activity carried out on components and, in particular, the results of monotonic and cyclic tests on connection systems. The tested specimens are clinching for steel-to-steel connection, whereas the fasteners used for panel-to-steel connections of walls and floors are ballistic nails.

The European project named "Energy Efficient LIghtweight-Sustainable-SAfe-Steel Construction" (Project acronym: ELISSA) is devoted to the development and demonstration of cold-formed steel (CFS) modular systems. In particular, these systems are nano-enhanced prefabricated lightweight steel skeleton/dry wall construction with improved thermal, vibration/seismic and fire performance, resulting from the inherent thermal, damping and fire spread prevention properties. From a structural point of view, these systems are represented by a sheathed-braced CFS solution, in which the seismic resistant elements are made of “Cocoon” CFS stud shear walls laterally braced by “Knauf” gypsum-based panels. The project plans the research activities on the basis of three levels: micro-scale, meso-scale and macro-scale. Concerning the research activity for the seismic performance evaluation, these three levels correspond to different test typologies. In particular, the micro-scale level consists of tests on materials/products/components forming the seismic resistant elements (shear walls), the meso-scale level corresponds to tests on single walls, the macro-scale level consists of shaking table tests on full scale two stories house prototype. This paper presents and discusses the planning of the research given information about test programs, specimens/prototypes, instrumentations and loading protocols.

The Cold-Formed Steel (CFS) structures are able to ensure a good structural response in seismic areas. Among them, the stick-built constructions raise a considerable interest in recent studies. In these structures, the lateral load bearing systems are CFS stud walls, that are generally realized with a frame in CFS profiles that can be braced by light gauge steel straps installed in an X configuration. In this case, the "all steel" design methodology can be adopted and the lateral resisting system is assured by the CFS strap-braced stud walls.

Past earthquakes have shown that the damage to non-structural elements can severely limit the functionality of most affected buildings and cause substantial economic losses. Among the non-structural building components, the ceiling-partition systems represent a large economic investment in construction sector. Nevertheless, their seismic performance is poorly understood, because information and specific guidance are very limited. In the last years, international studies have been conducted on the seismic behaviour of light gage steel stud partition walls (Lee et al. [1], Restrepo and Bersofsky [2], Tasligedik et al. [3], Retamales et al. [4], Magliulo at al. [5]), suspended ceilings (Badillo et al. [6], Magliulo et al. [7], Gilani et al. [8], Soroushian et al. [9],) and partition walls - ceiling systems (Filiatrault et al. [10], McCormick at al. [11]). Since the behaviour of these systems cannot be easily simulated with traditional structural analysis, experimentation is the main way to assess the seismic response. For these reasons, an experimental campaign has been planned at the University of Naples Federico II with the main aim to characterize the seismic response of different Cold-Formed Steel (CFS) partition drywalls and suspended continuous plasterboard ceilings. The current paper presents the research project, in terms of experimental program, prototypes and specifically designed set-up.

Recent earthquakes highlighted the high vulnerability of non-structural building components to relatively low seismic intensity levels. Their seismic damage could involve substantial economic losses, limit functionality interruption of the most affected buildings and pose a significant hazard to human life. Nevertheless, in the last decades, the study on the seismic response of non-structural building components has received less attention than the research addressed on the primary structural systems, by leading to a lack of specific design provisions for these systems. These considerations highlight that the development of protection measures aimed to reduce the seismic risks and to manage the vulnerabilities of the non-structural building components is becoming one of the most critical issues of the current seismic design. The importance of a rational concept of non-structural building components has also been recognized in the developments of modern seismic regulations, through the introduction of specific design requirements in terms of strength and deformation for these elements. However, the knowledge of their seismic performance is still poorly understood. Since the ceiling-partition walls systems represent a significant investment in the construction market, the current trend of the construction sector aims to the development and promotion of innovative solutions also in the field of non-structural applications. In this framework, lightweight steel drywall building components represent a valid alternative to traditional non-structural systems in seismic areas, by guaranteed a good seismic behaviour with respect to damage limit states mainly thanks to their lightness and low stiffness. However, since the behaviour of non-structural lightweight steel drywall building components cannot be easily simulated with traditional analysis methods, the experimental characterization is an effective procedure. For these reasons, an important collaboration between an industrial company and the University of Naples Federico II was established over the last few years. The main objective of the research is to investigate the seismic performance of non-structural lightweight steel drywall building components, also considering the design requirements provided in the modern seismic code for non-structural elements. The main aim of this dissertation is to give a contribution to the investigation of the seismic performance of lightweight steel gypsum board partition walls and their interaction with other non-structural and structural components, i.e. exterior walls and surrounding structural elements. In particular, two main objectives are pursued in this work: the study of the seismic behaviour of drywall partition walls, in terms of global response, by means of full-scale out-of-plane and in-plane experimental tests; and the study of local behaviour, by means of tests on main material and components, for understanding their influence on the wall global seismic response. Results obtained by material, component and connection tests will be useful for characterizing the local mechanical behaviour of the investigated systems and for predicting their global seismic response through suitable numerical studies. Furthermore, the experimental assessment of the wall global seismic response will provide seismic design criteria by testing to be compared with the design requirements provided in the European code.

Seismic damage of non-structural components could involve functionality interruption of the most affected buildings and substantial economic losses. Among non-structural components, the ceiling-partition wall systems represent a significant investment in the construction sector. Nevertheless, the seismic design of these systems plays a secondary role within the structural design, by leading to a lack of specific design provisions. Because the behaviour of these systems cannot be easily simulated with traditional analysis methods, the experimental characterization is an effective procedure. For these reasons, an important collaboration between an international company and the University of Naples Federico II was established over the last few years. The main objective of the research is to investigate the seismic performance of non-structural lightweight steel drywall building components, i.e. partition walls and suspended continuous ceilings made of lightweight steel profiles and sheathed with gypsum-based panels. The presented paper describes and discusses particularly the out-of-plane quasi-static monotonic tests and dynamic identification tests carried out on lightweight steel drywall partition walls, mainly devoted to develop the seismic design criteria by testing of these systems.

An experimental program was performed for evaluating the seismic response and fragilities of nonstructural lightweight steel drywall partitions, also considering the interaction with structural elements and other nonstructural building components, ie, outdoor façade walls. Therefore, in‐plane quasi‐static reversed cyclic tests were carried out on 8 specimens of indoor partition walls infilled in a frame and on 4 specimens of indoor partition walls connected at its ends with transversal outdoor façade walls. Constructive parameters under investigation include type of connections used for connecting the indoor partition walls to the surrounding elements, stud spacing, type of sheathing panels, and type of jointing finishing. The effect of the constructive parameters on the lateral response in secant stiffness and strength is examined. Furthermore, the main damage phenomena observed during the tests are reported and associated to 3 damage limit states distinguished for the required repair level for the tested partition walls. Fragility curves are used for the experimental assessment of seismic fragility of the tested specimens, in accordance with the interstorey drift limits required by the European code. Finally, the quantitative estimation of the repair action costs starting from the damage observation is also developed. The obtained results could be considered a starting point for developing the in‐plane seismic design assisted by testing of lightweight steel drywall partition walls.

Damages of non-structural components during a seismic event can involve risks for the human life, interruption of ordinary activities and significant economic losses. Therefore, the understanding of the seismic behaviour of non-structural components is a fundamental prerequisite for their use. In this context, a cooperation between the University of Naples "Federico II" and KnaufGips KG Company, aimed to the knowledge of seismic response of lightweight steel drywall non-structural components was carried forward. In this framework, shake table tests were carried out on protoypes composed by indoor partition walls, outdoor façade walls and suspended continuous ceilings. The influence on seismic response of basic and enhanced anti-seismic solutions, corresponding to the use of fixed or sliding connections at the walls and ceilings perimeter, was investigated. The seismic response in terms of damage occurrence was also evaluated by fragility curves, which show that enhanced solutions have a better seismic response than basic solutions and indoor partition walls have a higher seismic “fragility” than outdoor façade walls.

The unconventionality of the cold-formed steel (CFS) structures raised, in recent times, a lot of interest from many national and international companies resulting in the promotion of experimental activity with the main aim of investigating the seismic behaviour of these systems. In this perspective, a research project carried out at the University of Naples “Federico II” and funded by Lamieredil S.p.A. company started in the last years. The study included an extended experimental campaign, involving shake table tests on two three-storey prototypes in reduced scale (1:3). The investigated lateral load resisting systems were CFS strap-braced stud walls, designed as low dissipative seismic structures. The present paper illustrates case study, prototypes, test program and main shake table tests results.

A research project was conducted at University of Naples “Federico II” over the last few years with the aim to give a contribute to overcome the lack of information on seismic behaviour of architectural non-structural lightweight steel (LWS) drywall components, i.e. indoor partition walls, outdoor facades and suspended continuous ceilings. The tested non-structural components were made of LWS frames sheathed with gypsum-based or cement-based boards. The research activity was organized in three levels: ancilliary tests, component tests and assembly tests. Ancilliary tests were carried out for evaluating the local behaviour of partitions, facades and ceilings. Component tests involved out-of-plane quasi-static monotonic and dynamic identification tests and in-plane quasi-static reversed cyclic tests on partitions. Finally, the dynamic behaviour was investigated through shake table tests on different assemblages of partitions, facades and ceilings. The study demonstrated that the tested architectural non-structural LWS drywall components are able to exhibit a very good seismic behaviour with respect to the damage limit states according to the IDR limits given by Eurocode 8 Part 1. The current paper describes the complete experimental activity within the project.

In the past, the effort of the research was focused on the characterization and modelling of isolated CFS members or parts of building, but this cannot be enough for innovative structure, in which the sheathing panels interact with the steel framing providing the bracing effects against seismic actions. Therefore, in order to evaluate the seismic behaviour of CFS buildings sheathed with gypsum panels, a wide experimental campaign was conducted at University of Naples “Federico II” in the framework of European research project ELISSA (Energy efficient LIghtweight-Sustainable-SAfe steel construction). In particular, a two-storey building was tested on the shaking-table, considering different construction phases. In the first phase, the building included only structural elements and dynamic identification tests were carried out, whereas, in the second phase, the building was completed with all finishing components and it was tested for dynamic identification and under natural ground motions. In addition, a numerical model able to simulate the dynamic/earthquake response of the whole building, considering also the effect of finishing materials, was developed in OpenSees environment. The present paper describes the main results of shake-table testing and numerical modelling.

In the last years, the applications of cold-formed steel structures in domain of low-rise buildings are increasing. The seismic behaviour of these structures is influenced by the lateral response of shear walls, which are usually sheathed with panels. Different approaches are available to evaluate the lateral response of sheathed cold-formed steel (SCFS) walls: tabulated, numerical and analytical methodologies. In literature, a large number of methods developed for the analysis of sheathed wood shear walls is available and their application is also reasonable in the case of steel-framed shear walls. This paper aims to show the methodologies for prediction of SCFS shear wall response. The application of presented methodologies is illustrated using a calculation example by showing the results in terms of resistance and stiffness for SCFS shear wall.

Some experimental studies on the structural response of constructions made of cold-formed steel (CFS) profile are ongoing at University of Naples “Federico II”. Since the connections between panels and CFS frame have a fundamental role in the global response of CFS constructions, a specific task was devoted to test this kind of elements. In particular, the main object of the activity is the experimental characterization of solutions for panel-to-CFS connections commonly used in common practice, with reference to gypsum and cement-based solutions. In order to define their mechanical properties, 54 tests were carried out in order to assess the effect of panel type, thickness profile, screw diameter and number of panel layers. The results of this experimental investigation are discussed in this paper. Furthermore, the experimental values of shear strength obtained in the tests are compared with the available theoretical predictions and experimental data from literature.

Nowadays Lightweight Steel (LWS) Constructions made with Cold-Formed Steel (CFS) profiles are currently used in seismic area, especially for residential buildings. The increasing use of these systems is accompanied by a large development of the research in this field. Indeed, the University of Naples "Federico II" has recently started an important collaboration with Lamieredil S.p.A. Company in order to investigate the seismic behaviour of strap-braced CFS systems through a series of shake-table tests, performed on two reduced-scale strap-braced structures. In addition, 3D numerical models were developed in OpenSees environment in order to simulate the dynamic/earthquake response of the whole structure, considering also the effect of the two different floor typologies. The present paper illustrates the main results of the shake-table testing and numerical modelling.

The search for innovative methods to ensure high structural, technological and environmental performance is an important issue in the development of new constructions. Among the several available building systems, constructions involving the structural use of Cold-Formed Steel (CFS) profiles represent an efficient and reliable solution. In an effort to characterize the seismic response of CFS structures and to support the spreading of these systems, a theoretical and experimental research has been carried out at University of Naples Federico II within the Italian research project RELUIS-DPC 2010-2013. It focused on the "all steel design" solution, in which CFS diagonal strap-braced stud walls are the main lateral resisting system. In order to overcome the lack of information in the current European codes, a critical analysis of the requirements for these systems provided by the AISI S213-2007 has been carried out by comparing them with those given by Eurocodes for hot-rolled X-braced steel frames (tension-only). On the basis of the design hypothesis outlined from this analysis, a case study has been developed with the aim to define an extended experimental campaign involving 12 tests on full-scale CFS diagonal strap-braced stud walls. Finally, on the basis of experimental results, the assumed design prescriptions and requirements, such as the force modification factor and the capacity design rules, have been verified.

The development of light weight steel structures in seismic area as Italy requires the upgrading of National Codes. To this end, in the last years a theoretical and experimental study was undertaken at the University of Naples within the Italian research project RELUIS-DPC 2010-2013. The study focused on "all-steel design" solutions and investigated the seismic behaviour of strap-braced stud walls. Three typical wall configurations were defined according to both elastic and dissipative design criteria for three different seismic scenarios. The lateral in-plane inelastic behaviour of these systems was evaluated by twelve tests performed on full-scale Cold-formed strap-braced stud wall specimens with dimensions 2400 x 2700 m subjected to monotonic and reversed cyclic loading protocols. The experimental campaign was completed with seventeen tests on materials, eight shear tests on elementary steel connections and twenty-eight shear tests on strap-framing connection systems. This paper provides the main outcomes of the experimental investigation. Furthermore, the design prescriptions, with particular reference to the behaviour factor and the capacity design rules for these systems, have been proved on the basis of experimental results

The development of light weight steel structures in seismic area as Italy requires the upgrading of National Codes. To this end, in the last years a theoretical and experimental study was carried out at the University of Naples within the research project RELUIS-DPC 2010-2013. The study focused on "all steel design" solutions and investigated the seismic behaviour of strap braced stud shear walls. Three wall configurations were defined according to both elastic and dissipative design criteria for three different seismic scenarios. The lateral in-plane behavior of these systems were evaluated by 12 tests performed on full-scale CFS strap-braced stud wall specimens with dimensions 2.4 m x 2.7 m subjected to monotonic and reversed cyclic loading protocols. The experimental campaign was completed with 17 tests on materials, 8 shear tests on elementary steel connections and 28 shear tests on strap-framing connection systems. On the basis of the experimental results, and taking into account the AISI S213 provisions, behaviour factors were evaluated. This paper provides the main outcomes of the experimental tests on walls and behaviour factors evaluation.

The objective of this paper is to describe the shake table tests and the numerical modelling of a cold-formed steel (CFS) building. The two-storey full scale building, named as ELISSA mock-up, was subjected to shake table tests at University of Naples “Federico II”, as a part of the European project Energy efficient LIghtweight-Sustainable-SAfe steel construction (ELISSA). The tests were performed at two phases of the building construction process. In the first phase, only structural part of mock-up was subjected to dynamic identification tests, while in the second phase, the architectonic nonstructural elements were added and the mock-up was tested under the action of natural earthquake input with the varying scaling factors. Test results showed that the investigated construction system has a good seismic performance, with very low inter-storey drifts and negligible damages. Moreover, the non-structural elements influenced greatly the seismic response of building. Furthermore, a numerical model was also developed for the experimental mock-up at both construction phases using the OpenSees software. Models were able to simulate with a good accuracy the nonlinear dynamic response of the whole building at both phases.