Experimental investigation into the effect of vertical loading on in-plane cyclic behavior of adobe walls Ali Mirjalili, Abolfazl Eslami ⇑ , Reza Morshed Dept. of Civil Engineering, Yazd University, Yazd, Iran highlights  Adobe walls are tested under a combination of axial and lateral cyclic loading.  The experimental parameters involve axial load and height to width ratio.  The results are compared in terms of different structural parameters. article info Article history: Received 15 January 2020 Received in revised form 8 August 2020 Accepted 20 August 2020 Keywords: Adobe wall In-plane lateral behavior Cyclic load Vertical load Lateral resistance Displacement capacity abstract Adobe buildings are highly susceptible to lateral loads, which is responsible for their collapse during earth- quakes in the past resulting in vast damages and immense human casualties. Nonetheless, a majority of such buildings in the seismic-prone regions worldwide, including those in the Iranian plateau, are in every-day use. Thus, close examination of their behavior under lateral loading is vital for developing appro- priate retrofit techniques aimed at preventing their severe damage and the associated casualties during strong ground motions. Towards this, the present experimental investigation was designed and imple- mented to study the in-plane lateral behavior of adobe walls under different axial pre-compression loads. The experimental program consisted of 12 adobe wall panels, all 1000 mm long and 200 mm thick but of three different heights of 800, 900, and 1000 mm. Loading was applied in the form of an incremental lateral loading regime in the presence of four vertical pre-compression stresses of 0.1, 0.3, 0.5, and 0.7 MPa. The aim was to investigate the effects of vertical loading and wall height on the in-plane lateral responses of adobe walls. The results were compared in terms of hysteretic load-displacement response, lateral resis- tance, displacement capacity, ductility, stiffness degradation, and energy absorption. Another aspect of the study involves a detailed examination of the failure modes and general behavior of the specimens. Ó 2020 Elsevier Ltd. All rights reserved. 1. Introduction Adobe is a type of unfired brick made of clayey soil molded either manually or under mechanical compression. It has served as an inexpensive and locally available construction material for thousands of years in many parts of the world. Many of the adobe buildings are still in everyday use, particularly in developing coun- tries. In the central cities of Iran, such as Yazd, adobe constructions constitute a robust part of the down town regions. Recent years have witnessed a renewed attention to adobe buildings due to their intrinsic features such as eco-friendliness, thermal insulation, humidity regulation, and compatibility with vernacular architecture. These features represent adobe as an outstanding material for sustainable construction. Consequently, efforts have been made to resume using adobe in construction pro- jects and improving its short- and long-term behaviors with fibers and stabilizers such as lime and cement [1]. However, recent inves- tigations about earth stabilization indicated that the cement stabi- lization would not be much beneficial as it was proposed in the past [2]. While it brings only moderate mechanical improvements at a high environmental cost. Thus, it is, in general, neither techni- cally nor environmentally advisable. Further, it has been indicated that unstabilized earth blocks could provide satisfactory values of compressive strength [3,4]. The adobe used in the traditional construction of the Iranian pla- teau is typically set with mud mortar. The structures made thereof offer an acceptable compressive strength enabling them to carry gravity loads. However, they are highly vulnerable to lateral loading such as those produced during seismic ground motions due to their negligible tensile strength. Regarding the lateral performance of adobe buildings, walls play a prominent role in their overall struc- https://doi.org/10.1016/j.conbuildmat.2020.120706 0950-0618/Ó 2020 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: a.eslami@yazd.ac.ir (A. Eslami). Construction and Building Materials 264 (2020) 120706 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat